Similar Journals
|
Photochem
Number of Followers: 15  Open Access journalISSN (Online) 2673-7256 Published by MDPI  [258 journals]
|
- Photochem, Vol. 3, Pages 197-208: Conformational-Dependent
Photodissociation of Glycolic Acid in an Argon Matrix
Authors: Jussi Ahokas, Timur Nikitin, Justyna Krupa, Iwona Kosendiak, Rui Fausto, Maria Wierzejewska, Jan Lundell
First page: 197
Abstract: Ultraviolet-induced photodissociation and photo-isomerization of the three most stable conformers (SSC, GAC, and AAT) of glycolic acid are investigated in a low-temperature solid argon matrix using FTIR spectroscopy and employing laser radiation with wavelengths of 212 nm, 226 nm, and 230 nm. The present work broadens the wavelength range of photochemical studies of glycolic acid, thus extending the understanding of the overall photochemistry of the compound. The proposed kinetic model for the photodissociation of glycolic acid proceeds from the lowest energy conformer (SSC). The model suggests that ultraviolet light induces isomerization only between the SSC and GAC conformers and between the SSC and AAT conformers. The relative reaction rate coefficients are reported for all proposed reactions. These results suggest that the direct photodissociation of GAC and AAT conformer does not occur in an argon matrix. The main photodissociation channel via the SSC conformer produces formaldehyde–water complexes. The proposed photodissociation mechanism emphasizes that the conformers’ relative abundancies can significantly affect the photodissociation rate of the molecule. For example, in the case of high relative GAC and AAT concentrations, the ultraviolet photodissociation of glycolic acid requires the proceeding photo-isomerization of GAC and AAT to SSC.
Citation: Photochem
PubDate: 2023-03-31
DOI: 10.3390/photochem3020013
Issue No: Vol. 3, No. 2 (2023)
- Photochem, Vol. 3, Pages 209-226: Photodynamic Activity of Acridine Orange
in Keratinocytes under Blue Light Irradiation
Authors: Bárbara Fornaciari, Marina S. Juvenal, Waleska K. Martins, Helena C. Junqueira, Maurício S. Baptista
First page: 209
Abstract: Acridine orange (AO) is a metachromatic fluorescent dye that stains various cellular compartments, specifically accumulating in acidic vacuoles (AVOs). AO is frequently used for cell and tissue staining (in vivo and in vitro), mainly because it marks different cellular compartments with different colors. However, AO also forms triplet excited states and its role as a photosensitizer is not yet completely understood. Human immortalized keratinocytes (HaCaT) were incubated for either 10 or 60 min with various concentrations (nanomolar range) of AO that were significantly lower than those typically used in staining protocols (micromolar). After incubation, the cells were irradiated with a 490 nm LED. As expected, cell viability (measured by MTT, NRU and crystal violet staining) decreased with the increase in AO concentration. Interestingly, at the same AO concentration, altering the incubation time with HaCaT substantially decreased the 50% lethal dose (LD50) from 300 to 150 nM. The photoinduced cell death correlated primarily with lysosomal disfunction, and the correlation was stronger for the 60 min AO incubation results. Furthermore, the longer incubation time favored monomers of AO and a distribution of the dye to intracellular sites other than lysosomes. Studies with mimetic systems indicated that monomers, which have higher yields of fluorescence emission and singlet oxygen generation, are favored in acidic environments, consistent with the more intense emission from cells submitted to the longer AO incubation period. Our results indicate that AO is an efficient PDT photosensitizer, with a photodynamic efficiency that is enhanced in acidic environments when multiple intracellular locations are targeted. Consequently, when using AO as a probe for live cell tracking and tissue staining, care must be taken to avoid excessive exposure to light to avoid undesirable photosensitized oxidation reactions in the tissue or cell under investigation.
Citation: Photochem
PubDate: 2023-04-23
DOI: 10.3390/photochem3020014
Issue No: Vol. 3, No. 2 (2023)
- Photochem, Vol. 3, Pages 227-273: Photophysical Properties of Anthracene
Derivatives
Authors: Agonist Kastrati, Franck Oswald, Antoine Scalabre, Katharina M. Fromm
First page: 227
Abstract: In this tutorial review, we intend to provide the reader with a comprehensive introduction to the photophysical properties of organic compounds with a specific focus on anthracene and its derivatives. Anthracene-based building blocks have attracted the attention of chemists due to their intrinsic luminescent properties. A deep understanding of their interaction with light, including the mechanisms of emission (luminescence, i.e., fluorescence or phosphorescence) and quenching, is crucial to design and generate compounds with precise properties for further applications. Thus, the photophysical properties of different types of aggregates, both in the ground state (J- and H-type) and in the exited state (e.g., excimer, exciplex) will be discussed, finishing with a few examples of dyads and triads.
Citation: Photochem
PubDate: 2023-05-04
DOI: 10.3390/photochem3020015
Issue No: Vol. 3, No. 2 (2023)
- Photochem, Vol. 3, Pages 274-287: Synthesis and Characterization of New
Tetradentate N2O2-Based Schiff’s Base Cu (II) Complexes for Dye
Photodegradation
Authors: Rohini Vallavoju, Ranjith Kore, Radhika Parikirala, Mahesh Subburu, Ramesh Gade, Vipin Kumar, Matta Raghavender, Prabhakar Chetti, Someshwar Pola
First page: 274
Abstract: We have reported tetradentate ligands (salophen) coordinated with N and O atoms that led to the Cu (II) complexes. These Cu (II) complexes (C-1 and C-2) were firstly established by using elemental analysis and confirmed by mass spectra. At the same time, the characterization of C-1 and C-2 complexes is performed by using several spectroscopic methods and morphological analysis. The bandgap values of the C-1 and C-2 complexes are evaluated with UV-vis DRS spectra. The PL spectral data and photocurrent curves clearly indicated the small recombination rate of the hole–electron pair. The synthesized C-1 and C-2 complexes’ photocatalytic properties were examined for the degradation of cationic dyes such as methylene blue (MB λmax.= 654 nm) and methyl violet (MV λmax.= 590 nm) below visible-light action. The C-2 complex is more active than the C-1 complex because of its high photostability, small band-gap energy, and low recombination rate for hole–electron pair separation, and improved visible-light character, which encourages the generation of hydroxyl radical species throughout the photodegradation process. Scavenger probes were used to identify the dynamic species for the photodegradation of dyes, and a mechanism investigation was established.
Citation: Photochem
PubDate: 2023-05-11
DOI: 10.3390/photochem3020016
Issue No: Vol. 3, No. 2 (2023)
- Photochem, Vol. 3, Pages 1-14: Fluorescence Quantum Yields and Lifetimes
of Aqueous Natural Dye Extracted from Tradescantia pallida purpurea at
Different Hydrogen Potentials
Authors: Sthanley R. De Lima, Larissa R. Lourenço, Marina Thomaz, Djalmir N. Messias, Acácio A. Andrade, Viviane Pilla
First page: 1
Abstract: In this work, we monitored the fluorescence quantum efficiency (η) and the fluorescence lifetime (τ) of natural dye extracts from the leaves of Tradescantia pallida purpurea. The natural dye was extracted from leaves in aqueous solutions as a function of the potential of hydrogen (pH). The η was determined from conical diffraction (CD) pattern measurements due to thermally-driven self-phase modulation. The fluorescence spectra and time-resolved fluorescence measurements corroborate the CD results, and the average η ≈ 0.28 and τ ≈ 3.1 ns values were obtained in the pH range 3.96–8.02. In addition, the extracted natural dye was tested as a possible colorimetric and/or fluorometric pH indicator in milk.
Citation: Photochem
PubDate: 2023-01-03
DOI: 10.3390/photochem3010001
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 15-37: Cobalt Sulfide (Co9S8)-Based Materials
with Different Dimensions: Properties, Preparation and Applications in
Photo/Electric Catalysis and Energy Storage
Authors: Chuantao Wang, Xiangxiang Pang, Guangqing Wang, Loujun Gao, Feng Fu
First page: 15
Abstract: Due to their excellent properties and unique structures, transition metal sulfides play an important role in the development of efficient and stable photoelectric catalysts. In recent years, their potential applications have expanded from photoelectric catalysis to energy storage, especially as materials for key components of electrochemical energy storage. As a typical multifunctional metal sulfide catalyst, Co9S8 is highly attractive due to its high conductivity, better stability, suitable band structure, enhanced performance and wide applications. A large number of studies have shown that strategically modified Co9S8-based materials have greater advantages in various applications compared with pure Co9S8. Therefore, this review will evaluate the physicochemical properties and the preparation of different dimensions of Co9S8-based materials, and the influence of different structures on the photoelectrochemical energy of materials will be described. In addition, the research progress regarding the evolution of hydrogen photocatalytic, electrocatalytic water splitting and various electrochemical energy storage materials will be emphasized. Finally, the challenges faced by Co9S8-based materials and the research directions for their future applications will be discussed.
Citation: Photochem
PubDate: 2023-01-12
DOI: 10.3390/photochem3010002
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 38-58: Bismuth Vanadate-Nanostructured Graphite
Electrodes for Rhodamine B Photoelectrochemical Degradation
Authors: Bruna Guimarães Isecke, Arthur Saldanha Guimarães, Guilhermina Ferreira Teixeira, Flavio Colmati, Aparecido Ribeiro de Souza, Isaac Yves Lopes de Macêdo, Lucas Mattos Duarte, Sergio Botelho de Oliveira, André Gabriel Carmo Costa, Vernon Sydwill Somerset, Eric de Souza Gil
First page: 38
Abstract: Electrocatalysis is a promising way to treat water contaminated by harmful organic compounds. The combination of nanoparticles supported on a conductive substrate allows degradation to occur under less energetic conditions. This work evaluated the effect of deposition of bismuth vanadate (BVO) particles on pencil-type graphite electrodes. BVO particles were obtained by ultrasonic irradiation with coprecipitation. Then, they were deposited on the surface of a graphite electrode by the impregnation method. A 23-design was used to optimize electrode fabrication. Matter Dispersion Spectroscopy (SEM/EDS), X-Ray Diffraction (XRD) and Dynamic Light Scattering (DLS) were used for characterization. Electrochemical characterization was performed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results confirmed the synthesis of BVO@C (BVO/graphite). Furthermore, BVO@C significantly increased the electroactive surface area of the electrode, decreased the electron transfer resistance, and significantly increased the electron transfer rate to a greater extent than the electrode without any modification. To prove that the performance of BVO@C is better than the pure electrode, photoelectrocatalysis (PEC) and electrocatalysis (EC) were performed in a rhodamine B (RhB) solution. The results showed that in 5 min of treatment with unmodified electrode, BVO@C EC system and BVO@C PEC system, there was degradation of 31.53%, 46.09% and 58.17% respectively, reaching 95%, 98% and 99.64%, respectively, in 30 min. The reaction rate constants were calculated and to be found k = 0.10272 m−1, k = 0.12221 m−1 and k= 0.15022 m−1 for the unmodified graphite, BVO@C EC System and BVO@C PEC system, respectively. These results demonstrate that the BVO@C electrodes are efficient for application in a wide range of treatments, including the treatment of organic pollutants.
Citation: Photochem
PubDate: 2023-01-13
DOI: 10.3390/photochem3010003
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 59-60: Acknowledgment to the Reviewers of
Photochem in 2022
Authors: Photochem Editorial Office Photochem Editorial Office
First page: 59
Abstract: High-quality academic publishing is built on rigorous peer review [...]
Citation: Photochem
PubDate: 2023-01-20
DOI: 10.3390/photochem3010004
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 61-81: Spectroscopic and DFT Study of Alizarin
Red S Complexes of Ga(III) in Semi-Aqueous Solution
Authors: Licínia L. G. Justino, Sofia Braz, M. Luísa Ramos
First page: 61
Abstract: A combined spectroscopic and computational approach has been used to study in detail the complexation between Ga(III) and ARS in solution. The NMR results revealed the formation of four Ga(III)/ARS complexes, at pH 4, differing in their metal:ligand stoichiometries or configuration, and point to a coordination mode through the ligand positions C-1 and C-9. For equimolar metal:ligand solutions, a 1:1 [Ga(ARS)(H2O)4]+ complex was formed, while for 1:2 molar ratio solutions, a [Ga(ARS)2(H2O)2]− complex, in which the two ligands are magnetically equivalent, is proposed. Based on DFT calculations, it was determined that this is a centrosymmetric structure with the ligands in an anti configuration. For solutions with a 1:3 molar ratio, two isomeric [Ga(ARS)3]3− complexes were detected by NMR, in which the ligands have a mer and a fac configuration around the metal centre. The DFT calculations provided structural details on the complexes and support the proposal of a 1,9 coordination mode. The infrared spectroscopy results, together with the calculation of the infrared spectra for the theoretically proposed structures, give further support to the conclusions above. Changes in the UV/vis absorption and fluorescence spectra of the ligand upon complexation revealed that ARS is a highly sensitive fluorescent probe for the detection of Ga(III).
Citation: Photochem
PubDate: 2023-01-31
DOI: 10.3390/photochem3010005
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 82-97: Action of Photodynamic Therapy at Low
Fluence in 9 L/lacZ Cells after Interaction with Chlorins
Authors: Gabrielle dos Santos Vitorio, Bruno Henrique Godoi, Juliana Guerra Pinto, Isabelle Ferreira, Cristina Pacheco Soares, Juliana Ferreira-Strixino
First page: 82
Abstract: Gliosarcoma (GS) is a primary malignant neoplasm of the central nervous system, treated with an unfavorable prognosis with surgery, radiotherapy, and chemotherapy. The treatment for GS consists of surgical resection, almost always accompanied by radiotherapy and/or chemotherapy, given the invasive behavior of the tumor. Photodynamic Therapy (PDT) is studied as an alternative method that combines light, a photosensitizer (PS), and molecular oxygen. This study aimed to compare the effects of PDT using the photosensitizers Fotoenticine (FTC) and Photodithazine (PDZ) at low concentrations and fluences. For this study, 9 L/lacZ cells, concentrations of 1.55 µg mL−1, 12.5 µg mL−1, and 50 µg mL−1 of chlorins and fluences of 1, 5, and 10 J/cm2 were used. A test was also carried out with Trypan Blue in L929 cells at the mentioned concentrations at 5 J/cm2. Both chlorins were internalized in the cytoplasm, with a significant reduction in viability (>95%) in almost all groups and altered cell adhesion and morphology after PDT. HSP70 expression decreased in both PS, while HSP27 increased only in PDT with FTC, and although there was a change in cell adhesion in the 9 L/LacZ lineage it was not observed in the L929 fibroblast lineage. Both chlorins were effective, highlighting the concentration of 50 µg mL−1 at the fluence of 5 J/cm2; according to the present study, the PDZ showed better results.
Citation: Photochem
PubDate: 2023-02-02
DOI: 10.3390/photochem3010006
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 98-108: The Fate of Sulfur Radical Cation of
N-Acetyl-Methionine: Deprotonation vs. Decarboxylation
Authors: Katarzyna Grzyb, Vidhi Sehrawat, Tomasz Pedzinski
First page: 98
Abstract: In the present study, we investigated the photooxidation of the biomimetic model of C-terminal methionine, N-Acetyl-Methionine (N-Ac-Met), sensitized by a 3-Carboxybenzophenone (3CB) excited triplet in neutral and basic aqueous solutions. The short-lived transient species that formed in the reaction were identified and quantified by laser flash photolysis and the final stable products were analyzed using liquid chromatography coupled with high-resolution mass spectrometry (LC-MS) and tandem mass spectrometry (MSMS). Based on these complementary methods, it was possible to calculate the quantum yields of both competing reactions, and the deprotonation was found to be favored over decarboxylation (for neutral pH: ϕ-H = 0.23 vs. ϕ-CO2 = 0.09, for basic pH: ϕ-H = 0.23 vs. ϕ-CO2 = 0.05). Findings on such a model system, which can possibly mimic the complex protein environment, are important in understanding complicated biological systems, for example, the studied compound, N-Ac-Met, can, to some extent, mimic the methionine in the C-terminal domain of β-amyloid, which is thought to be connected with the pathogenesis of Alzheimer’s disease.
Citation: Photochem
PubDate: 2023-02-05
DOI: 10.3390/photochem3010007
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 109-126: Pyridine-Based Small-Molecule
Fluorescent Probes as Optical Sensors for Benzene and Gasoline
Adulteration
Authors: Thiago Jacobsen Peglow, Marcelo Marques Vieira, Nathalia Batista Padilha, Bianca T. Dalberto, Henrique de Castro Silva Júnior, Fabiano Severo Rodembusch, Paulo Henrique Schneider
First page: 109
Abstract: Here we present simple fluorophores based on the pyridine core, obtained with straightforward synthetic methodologies. These compounds present in solution absorption maxima in the UV region and fluorescence emission of between 300 and 450 nm, depending on the solvent and chemical structure of the fluorophore. The nature of the solvent was shown to play a fundamental role in their excite-state deactivation, which allowed successful exploration of these compounds as optical sensors for benzene and fuel adulteration in gasoline. In ethanolic solution, upon the addition of benzene, in general the fluorophores presented fluorescence quenching, where a linear correlation between the emission intensity and the amount of benzene (quencher) was observed. In addition, the application of an optical sensor for the detection of fuel adulteration in commercial standard and premium gasoline was successfully presented and discussed. Theoretical calculations were also applied to better understand the solvent–fluorophore interactions.
Citation: Photochem
PubDate: 2023-02-17
DOI: 10.3390/photochem3010008
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 127-154: Linear and Nonlinear Optical Properties
of Quadrupolar Bithiophenes and Cyclopentadithiophenes as Fluorescent
Oxygen Photosensitizers
Authors: Nicolas Richy, Safa Gam, Sabri Messaoudi, Amédée Triadon, Olivier Mongin, Mireille Blanchard-Desce, Camille Latouche, Mark G. Humphrey, Abdou Boucekkine, Jean-François Halet, Frédéric Paul
First page: 127
Abstract: The linear and nonlinear optical properties of two quadrupolar bithiophenes and two quadrupolar cyclopentadithiophenes have been investigated. At the 5,5′ positions of the central bi/dithiophene units, the molecules possess 1,4-phenylalkynyl groups that bear either electron-donating (NPh2) or electron-withdrawing (SO2CF3) groups. The optical properties were experimentally studied and modelled via quantum chemistry computations of key configurations and conformations. All the compounds show good light harvesting efficiency due to their strong absorption in the visible range. These fluorescent compounds are also good two-photon absorbers in the NIR range that can photosensitize oxygen in toluene. DFT calculations reveal that the mixtures of conformers in a solution show similar linear optical properties. TD-DFT calculations reproduce the experimental spectroscopic data fairly well, including vibronic couplings in the fluorescence spectra. The lowest excited state for two-photon absorption corresponds to the S2 state. The roles of the SO2CF3 and NPh2 terminal groups on the nonlinear response were analyzed for possible bio-oriented applications, with the cyclopentadithiophenes showing the most promising figures of merit.
Citation: Photochem
PubDate: 2023-02-20
DOI: 10.3390/photochem3010009
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 155-170: Insights into the Machine Learning
Predictions of the Optical Response of Plasmon@Semiconductor Core-Shell
Nanocylinders
Authors: Ehsan Vahidzadeh, Karthik Shankar
First page: 155
Abstract: The application domain of deep learning (DL) has been extended into the realm of nanomaterials, photochemistry, and optoelectronics research. Here, we used the combination of a computer vision technique, namely convolutional neural network (CNN), with multilayer perceptron (MLP) to obtain the far-field optical response at normal incidence (along cylinder axis) of concentric cylindrical plasmonic metastructures such as nanorods and nanotubes. Nanotubes of Si, Ge, and TiO2 coated on either their inner wall or both their inner and outer walls with a plasmonic noble metal (Au or Ag) were thus modeled. A combination of a CNN and MLP was designed to accept the cross-sectional images of cylindrical plasmonic core-shell nanomaterials as input and rapidly generate their optical response. In addition, we addressed an issue related to DL methods, namely explainability. We probed deeper into these networks’ architecture to explain how the optimized network could predict the final results. Our results suggest that the DL network learns the underlying physics governing the optical response of plasmonic core-shell nanocylinders, which in turn builds trust in the use of DL methods in materials science and optoelectronics.
Citation: Photochem
PubDate: 2023-03-02
DOI: 10.3390/photochem3010010
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 171-186: Water-Soluble Dicationic
Deuteroporphyrin Derivative for Antimicrobial PDT: Singlet Oxygen
Generation, Passive Carrier Interaction and Nosocomial Bacterial Strains
Photoinactivation
Authors: Dmitry B. Berezin, Sergey O. Kruchin, Natal’ya V. Kukushkina, Evgeny A. Venediktov, Mikhail O. Koifman, Andrey V. Kustov
First page: 171
Abstract: Multidrug resistance of pathogenic microflora is a serious threat to the modern community looking for new approaches to treating superinfections. In this sense, antimicrobial photodynamic therapy (aPDT) is an effective and safe technique considered to be a promising alternative or an important supplement to the traditional clinically applied methods for inactivating antibiotic resistant pathogens. Macroheterocyclic photosensitizers (PS) of three generations are proposed for clinical practice. They are known as the key compounds for PDT able to be localized selectively in microbial cells and to be activated with the red light producing toxic reactive oxygen species (ROS). However, these neutral and anionic PSs possess low affinity towards the outer lipopolysaccharide membrane of Gram-negative bacteria and, consequently, poor ability to kill these pathogens under irradiation. In contrast, cationic PSs containing one or more charged groups, especially those bound to an appropriate carrier, provide efficient inactivation of microorganisms. In this paper, we focus on the study of photophysics, aggregation and photoinduced antimicrobial activity of the water-soluble derivative of deuteroporphyrin-IX, a blood group porphyrin, bearing two cationic trialkylammonium fragments. This potential photosensitizing agent is found to generate singlet oxygen in a non-polar environment and forms stable nano-sized molecular complexes with passive non-ionic carrier Tween 80, localizing in an aqueous surfactant solution as a non-aggregated form in the surface micellar layer. Two different modes of PS/Tween 80 binding characterized by their own stability constants and interaction stoichiometry are observed. Microbiological experiments clearly demonstrate that the increased permeability of the outer bacterial membrane caused by the application of the intramicellar form of the photosensitizer or addition of some potentiation agents leads to pronounced light phototoxicity of the pigment against antibiotic-resistant nosocomial strains of Gram-negative bacterial pathogens.
Citation: Photochem
PubDate: 2023-03-11
DOI: 10.3390/photochem3010011
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 3, Pages 187-196: Facile Synthesis, Characterization, and
Photocatalytic Performance of BiOF/BiFeO3 Hybrid Heterojunction for
Benzylamine Coupling under Simulated Light Irradiation
Authors: Abdalla S. Abdelhamid, Reem H. Alzard, Lamia A. Siddig, Aya Elbahnasy, Duha Aljazmati, Zaina Kadoura, Hind Zeidane, Rufaida Elshikh, Ahmed Alzamly
First page: 187
Abstract: Under simulated light irradiation, the aerobic oxidation of benzylamine to N,N-benzylidenebenzylamine was carried out as a model reaction to investigate the photocatalytic activity of a hydrothermally prepared composite based on BiOF and BiFeO3 materials. The prepared photocatalysts were characterized using several spectroscopic techniques, such as powder X-ray diffraction (PXRD), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). Band gap analysis showed that the composite exhibits a band gap that lies in the UV region (3.5 eV). Nonetheless, pristine BiOF and BiFeO3 exhibited band gaps of 3.8 eV and 2.15 eV, respectively. N,N-benzylidenebenzylamine was selectively achieved with a high conversion yield of ~80% under atmospheric conditions in which the product was confirmed using 1H-NMR, 13C-NMR, and FTIR spectroscopic techniques. Various control experiments were conducted to further confirm the enhanced photocatalytic performance of the reported composite.
Citation: Photochem
PubDate: 2023-03-21
DOI: 10.3390/photochem3010012
Issue No: Vol. 3, No. 1 (2023)
- Photochem, Vol. 2, Pages 810-830: Plasmon-Induced Semiconductor-Based
Photo-Thermal Catalysis: Fundamentals, Critical Aspects, Design, and
Applications
Authors: Atif Sial, Afzal Ahmed Dar, Yifan Li, Chuanyi Wang
First page: 810
Abstract: Photo-thermal catalysis is among the most effective alternative pathways used to perform chemical reactions under solar irradiation. The synergistic contributions of heat and light during photo-thermal catalytic processes can effectively improve reaction efficiency and alter design selectivity, even under operational instability. The present review focuses on the recent advances in photo-thermal-driven chemical reactions, basic physics behind the localized surface plasmon resonance (LSPR) formation and enhancement, pathways of charge carrier generation and transfer between plasmonic nanostructures and photo-thermal conversion, critical aspects influencing photo-thermal catalytic performance, tailored symmetry, and morphology engineering used to design efficient photo-thermal catalytic systems. By highlighting the multifield coupling benefits of plasmonic nanomaterials and semiconductor oxides, we summarized and discussed several recently developed photo-thermal catalysts and their catalytic performance in energy production (CO2 conversion and H2 dissociation), environmental protection (VOCs and dyes degradation), and organic compound synthesis (Olefins). Finally, the difficulties and future endeavors related to the design and engineering of photo-thermal catalysts were pointed out to draw the attention of researchers to this sustainable technology used for maximum solar energy utilization.
Citation: Photochem
PubDate: 2022-10-02
DOI: 10.3390/photochem2040052
Issue No: Vol. 2, No. 4 (2022)
- Photochem, Vol. 2, Pages 831-848: Efficient Access of Phenyl-Spaced
5,5′-Bridged Dinuclear Ruthenium Metal Complexes and the Effect of
Dynamic Ligand Exchange on Catalysis
Authors: Martin Lämmle, Steffen Volk, Madelyn Klinkerman, Marius Müßler, Alexander K. Mengele, Sven Rau
First page: 831
Abstract: Herein, we present the synthesis, characterization, and light-driven hydrogen evolution activity of two dinuclear Ru-Pt complexes, Rup(ph)pPtX2 (X = Cl, I), comprising a new phenyl-spaced 5,5′-bis-phenanthroline p(ph)p bridging ligand. The two complexes only differ in the nature of the halide ligand at the catalytic center. Structural, photophysical, electrochemical, as well as photochemical characterization techniques revealed that the variations of single components of the intramolecular system provide a strong influence on the stability even in non-catalytic conditions. Interestingly, varying electron density at the catalytic center, mainly influenced by the coordinating halide at the catalytic center, as shown by 195Pt NMR spectroscopy, strongly influences the photocatalytic efficiency. Furthermore, intensive investigations on the potential catalytic mechanism showed that small structural variations (e.g., halide exchange) not only affect catalytic activity but can also switch the main catalytic mechanism from an initially molecular one to a fully heterogeneous, colloid-driven hydrogen evolution.
Citation: Photochem
PubDate: 2022-10-06
DOI: 10.3390/photochem2040053
Issue No: Vol. 2, No. 4 (2022)
- Photochem, Vol. 2, Pages 849-865: Photobehavior of an Acidochromic
Dinitrophenyl-Hydrazinylidene Derivative: A Case of Total Internal
Conversion
Authors: Letizia Mencaroni, Alessio Cesaretti, Giuseppe Consiglio, Fausto Elisei, Cosimo Gianluca Fortuna, Anna Spalletti
First page: 849
Abstract: Research in photochemistry is always looking for novel compounds that can serve a role in applications ranging from medicine to environmental science. Push–pull compounds with protonable groups represent an interesting class of molecules in this sense, as they can prove to be sensitive to changes in both the acidity and polarity of the medium, becoming valuable as sensors and probes. Hence, in this work, a new dinitrophenyl-hydrazinylidene derivative with multiple protonable centers has been specifically designed and synthesized. The molecule showed an important acidochromism in the visible, with three differently-protonated species under acidic, neutral, and basic conditions, each characterized by a peculiar absorption spectrum. The photophysical characterization of this compound revealed an ultrafast excited-state deactivation, as described by femtosecond transient absorption experiments, and the hints of charge-transfer dynamics, as supported by the observed solvatochromism and quantum-mechanical calculations. These properties led to almost undetectable fluorescence that, together with negligible intersystem crossing and the absence of reactive pathways, points to the preference for a total non-radiative deactivation mechanism, i.e., internal conversion. This intriguing behavior stimulates interest in light of possible applications of the investigated acidochromic dye as a probe in photoacoustic imaging, which offers an alternative to classical fluorescence imaging.
Citation: Photochem
PubDate: 2022-10-10
DOI: 10.3390/photochem2040054
Issue No: Vol. 2, No. 4 (2022)
- Photochem, Vol. 2, Pages 866-879: Increasing the Photocatalytic Activity
of BiVO4 by Naked Co(OH)2 Nanoparticle Cocatalysts
Authors: Luiz E. Gomes, Luiz F. Plaça, Washington S. Rosa, Renato V. Gonçalves, Sajjad Ullah, Heberton Wender
First page: 866
Abstract: Bismuth vanadate (BiVO4 or BVO) is one of the most studied photocatalysts for water oxidation because of its excellent visible light absorption and appropriate band energy positions. However, BVO presents a low charge mobility and a high electron–hole recombination rate. To address these fundamental limitations, this study proposes the coating of previously synthesized phase-pure monoclinic scheelite BVO with different amounts of naked cobalt (further oxidized to cobalt hydroxide) nanoparticles (NPs) via a modified magnetron sputtering deposition. The resulting BVO/Co photocatalysts were investigated for methylene blue (MB) photodegradation, photocatalytic oxygen evolution, and photoelectrochemical (PEC) water oxidation. In the MB photodegradation tests, the BVO/Co sample prepared with a deposition time of 5 min (BVO/Co(5 min)) presented the highest photoactivity (k = 0.06 min−1) compared with the other sputtering investigated times (k = 0.01–0.02 min−1), as well as the pristine BVO sample (k = 0.04 min−1). A similar trend was evidenced for the PEC water oxidation, where a photocurrent density of 23 µA.cm−2 at 1.23 V (vs. RHE) was observed for the BVO/Co(5 min) sample, a value 4.6 times higher compared with pristine BVO. Finally, the BVO/Co(5 min) presented an O2 evolution more than two times higher than that of the pristine BVO. The increased photocatalytic performance was ascribed to increased visible-light absorption, lesser electron–hole recombination, and enhanced charge transfer at the liquid/solid interface. The deposition of Co(OH)2 NPs via magnetron sputtering can be considered an effective strategy to improve the photocatalytic performance of BVO for different target catalytic reactions, including oxygen evolution, water oxidation, and pollutant photodegradation.
Citation: Photochem
PubDate: 2022-10-12
DOI: 10.3390/photochem2040055
Issue No: Vol. 2, No. 4 (2022)
- Photochem, Vol. 2, Pages 880-890: Photoprotective Effects of Selected
Polyphenols and Antioxidants on Naproxen Photodegradability in the
Solid-State
Authors: Kohei Kawabata, Ayano Miyoshi, Hiroyuki Nishi
First page: 880
Abstract: Photostabilization is an important methodology to ensure both the quality and quantity of photodegradable pharmaceuticals. The purpose of our study is to develop a photostabilization strategy focused on the addition of photostabilizers. In this study, the protective effects of selected polyphenols and antioxidants on naproxen (NPX) photodegradation in the solid state were evaluated. Residual amounts of NPX were determined by high-performance liquid chromatography (HPLC), and the protective effects of tested additives on NPX photodegradation induced by ultraviolet light (UV) irradiation were evaluated. As a result, quercetin, curcumin, and resveratrol suppressed NPX photodegradation completely. When they were mixed with NPX, the residual amounts of NPX after UV irradiation were significantly higher compared to that without additives, and comparable to those of their control samples. In addition, to clarify the mechanisms of the highly protective effects of these additives on NPX photodegradation, their antioxidative potencies, and UV filtering potencies were determined. There was no correlation between photoprotective effects and antioxidative potencies among selected polyphenols and antioxidants although photoprotective additives showed more significant UV absorption compared to NPX. From these results, it is clarified that a higher UV filtering activity is necessary for a better photostabilizer to photodegradable pharmaceuticals in the solid state.
Citation: Photochem
PubDate: 2022-11-06
DOI: 10.3390/photochem2040056
Issue No: Vol. 2, No. 4 (2022)
- Photochem, Vol. 2, Pages 891-904: Photodynamic Polymers Constituted by
Porphyrin Units as Antibacterial Materials
Authors: María B. Ballatore, María E. Pérez, Sofía C. Santamarina, Javier E. Durantini, María E. Milanesio, Edgardo N. Durantini
First page: 891
Abstract: Photodynamic inactivation of microorganisms has emerged as a promising strategy to kill and eradicate pathogens. In this work, two polymers, TCP-P and ZnTCP-P, were synthesized by oxidative polymerization of 5,10,15,20-tetrakis [3-(N-ethylcarbazoyl)]porphyrin and its complex with Zn(II). Solid polymers consist of rods (diameter 100 nm, length ~100–500 nm) that form microporous structures on a surface. UV-visible absorption spectra in solution showed the Soret and Q bands characteristic of the corresponding constitutional porphyrins. In addition, the polymers presented two red emission bands with quantum yields ΦF = 0.11 for TCP-P and ΦF = 0.050 for ZnTCP-P. These compounds sensitized the production of singlet molecular oxygen with quantum yields of ΦΔ~0.3. Thus, the spectroscopic and photodynamic properties of the porphyrin units were maintained in the conjugates. The photodynamic activity induced by both polymers was tested to inactivate S. aureus. In cell suspensions, TCP-P was more effective than ZnTCP-P in killing bacteria. Viable S. aureus cells were not detected using 4 µM TCP-P after 20 min of irradiation. Moreover, both polymers showed a high photocytotoxic activity to eradicate S. aureus cells attached to a surface. The results indicate that these conjugated polymers can act as effective antimicrobial agents to photoinactivate pathogens.
Citation: Photochem
PubDate: 2022-11-09
DOI: 10.3390/photochem2040057
Issue No: Vol. 2, No. 4 (2022)
- Photochem, Vol. 2, Pages 905-917: Application of Zirconia/Alumina
Composite Oxide Ceramics as Photocatalysts for Removal of
2,4,6-Trichlorophenol from Water
Authors: Tatjana D. Vulić, Milica V. Carević, Nadica D. Abazović, Tatjana B. Novaković, Zorica D. Mojović, Mirjana I. Čomor
First page: 905
Abstract: The mesoporous zirconia/alumina composites were synthesized via a sol–gel method, followed by heat treatment at 500 °C for 5 h. The effect of the ZrO2/Al2O3 ratio on the structural and textural properties of the obtained composites was explored. Sorption analysis has confirmed that all samples have a mesoporous structure whose parameters (SBET, Vp and Dmax) strongly depend on the ZrO2/Al2O3 ratio. The XRD pattern of composites has shown that the addition of zirconia disrupts the crystallinity of alumina. The composites with higher zirconia content (50% ZrO2 and 67% ZrO2) are characterized by peaks related only to the zirconia phase. UV/Vis diffuse reflection spectra of all samples revealed that composites have more intensive absorption compared to pure oxides for wavelengths larger than 250 nm and similar band gaps. Photoluminescence measurements showed presence of defects in all samples, which are responsible for photocatalytic activity. All samples showed significant adsorption/photocatalytic efficacy for the removal/degradation of 2,4,6 -trichlorophenol (TCP). Results obtained using HPLC and TOC techniques showed that between 70 and 80% of the initial TCP concentration was removed/degraded after 4 h of illumination. These results were corelated with flat, conduction and valence band potentials of synthesized pure and binary oxides, calculated using Mott–Schottky plots.
Citation: Photochem
PubDate: 2022-11-28
DOI: 10.3390/photochem2040058
Issue No: Vol. 2, No. 4 (2022)
- Photochem, Vol. 2, Pages 918-931: Effect of the Donor/Acceptor Size on the
Rate of Photo-Induced Electron Transfer
Authors: Nikolai V. Tkachenko
First page: 918
Abstract: The photo-induced electron transfer has been under intensive investigation for a few decades already, and a good understanding of the reaction was developed based on thorough study of the molecular donor–acceptor (DA) system. The recent shift to hybrid DA systems opens the question of transferring the knowledge to analyze and design these new materials. One of the apparent differences is the size increase of the donor or acceptor entities. The electronic wave functions of larger entities occupy a larger volume, but since these are still one-electron wave functions, their amplitudes are lower. A simple analysis proposed here demonstrates that this leads to roughly inverse third power dependence of the electron transfer rate constant on the donor or acceptor size, kET∝R−3. This dependence can be observed upon switching from molecular to quantum dot donor in DA systems with a fullerene acceptor.
Citation: Photochem
PubDate: 2022-11-30
DOI: 10.3390/photochem2040059
Issue No: Vol. 2, No. 4 (2022)
- Photochem, Vol. 2, Pages 932-946: Structural Quasi-Isomerism in Au/Ag
Nanoclusters
Authors: Yifei Zhang, Kehinde Busari, Changhai Cao, Gao Li
First page: 932
Abstract: Atomically precise metal nanoclusters are a new kind of nanomaterials that appeared in recent years; a pair of isomer nanoclusters have the same metal types, numbers of metal atoms, and surface-protected organic ligands but different metal atom arrangements. This article summarizes the structure features of isomer nanoclusters and concentrates on synthesis methods that could lead to isomer structure. The pairs of isomer inorganic nanoclusters’ conversion to each other and their applications in catalyst and photoluminescence are also discussed. We found that the structure conversions are relevant to their stability. However, with the same molecule formulas, different atom arrangements significantly influence their performance in applications. Finally, the existing challenges and some personal perspectives for this novel field in the nano-science investigation are proposed. We hope this minireview can offer a reference for researchers interested in inorganic isomer nanoclusters.
Citation: Photochem
PubDate: 2022-12-05
DOI: 10.3390/photochem2040060
Issue No: Vol. 2, No. 4 (2022)
- Photochem, Vol. 2, Pages 463-478: UPS, XPS, NEXAFS and Computational
Investigation of Acrylamide Monomer
Authors: Luca Evangelisti, Sonia Melandri, Fabrizia Negri, Marcello Coreno, Kevin C. Prince, Assimo Maris
First page: 463
Abstract: Acrylamide is a small conjugated organic compound widely used in industrial processes and agriculture, generally in the form of a polymer. It can also be formed from food and tobacco as a result of Maillard reaction from reducing sugars and asparagine during heat treatment. Due to its toxicity and possible carcinogenicity, there is a risk in its release into the environment or human intake. In order to provide molecular and energetic information, we use synchrotron radiation to record the UV and X-ray photoelectron and photoabsorption spectra of acrylamide. The data are rationalized with the support of density functional theory and ab initio calculations, providing precise assignment of the observed features.
Citation: Photochem
PubDate: 2022-06-22
DOI: 10.3390/photochem2030032
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 479-488: Antibacterial Activity of In Situ
Generated Silver Nanoparticles in Hybrid Silica Films
Authors: Sudipto Pal, Rossella Nisi, Antonio Licciulli
First page: 479
Abstract: Herein we present silver nanoparticles (AgNPs)-doped inorganic–organic hybrid silica films on glass and polypropylene substrates. A hybrid inorganic–organic silica sol in alcoholic medium was prepared at room temperature using TEOS, GLYMO, and APTES. Silver nanoparticles were generated in situ within the hybrid silica sol. AgNPs-SiO2 film was obtained by dip coating method following drying at 80 °C. FTIR spectra shows several vibrational bands of the hybrid silica network and amine functionalization. AgNPs formation was observed from the XRD spectra of the dried film. UV–Visible spectra show sharp surface plasmon resonance (SPR) band centered at 412 nm arising from the evenly distributed silver nanoparticle inside the silica film that was supported by morphological characterization. Both the coated films showed good antibacterial activity against E. coli bacterial strain by forming a zone of inhibition in the agar diffusion test. The antibacterial efficiency for coated glass and polypropylene was 72.5% and 83.75%. This coating approach provides a straight-forward solution to prepare antibacterial coatings on various substrates especially on plastics, where low temperature processing is necessary.
Citation: Photochem
PubDate: 2022-06-23
DOI: 10.3390/photochem2030033
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 489-502: Probing the Local Polarity in
Biocompatible Nanocarriers with Solvatofluorochromism of a
4-Carbazole-1,8-naphthalimide Dye
Authors: Ana M. Diniz, Rui P. R. Cruz, João Avó
First page: 489
Abstract: The study of local polarity at the nanoscale is of crucial importance for the development of smart drug delivery systems and photonic materials and is frequently accomplished with the use of luminescent tracer dyes. Nile Red is often used for this purpose, owing to its polarity-sensitive internal charge transfer transition, but its performance is affected by specific solute-solvent interactions that prevent its widespread applicability. Herein, we develop a new 1,8-naphthalimide dye with a strong charge-transfer transition that results in a large dipole moment change upon excitation. This leads to luminescence properties with high sensitivity to solvent polarity, that are independent of specific or inductive interactions. These properties are explored to probe the polarity of biocompatible nanocarriers. This dye was effective in probing the properties of polymeric nanoparticles, allowing the accurate calculation of polarity descriptors and dielectric constants.
Citation: Photochem
PubDate: 2022-06-24
DOI: 10.3390/photochem2030034
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 503-514: Pharmaceutical Micropollutant Treatment
with UV–LED/TiO2 Photocatalysis under Various Lighting and Matrix
Conditions
Authors: Monika Snowdon, Robert Liang, Jocelyn C. Van Leeuwen, Olivia Schneider, Abrar Khan, Lena C. M. Li Chun Fong, Norman Y. Zhou, Mark R. Servos
First page: 503
Abstract: The persistence of pharmaceuticals and personal care products (PPCPs) in water has been a cause for concern for several years. Many studies have successfully used TiO2/UV photocatalysis to remove these compounds from water. In order to optimize these systems for large-scale water treatment, the effects of the reaction matrix, methods to improve energy efficiency, and methods for easy catalyst separation must be considered. The following study examines the photocatalytic degradation of a cocktail of 18 PPCPs using a porous titanium–titanium dioxide membrane and the effect of solution pH on kinetic rate constants. The addition of methanol to the reaction—commonly used as a carrier solvent—had a significant effect on kinetic rate constants even at low concentrations. Solution pH was also found to influence kinetic rate constants. Compounds had higher kinetic rate constants when they were oppositely charged to the membrane at experimental pH as opposed to similarly charged, suggesting that electrostatic forces have a significant effect. The controlled periodic illumination of UV–LEDs was also investigated to increase photonic efficiency. The dual-frequency light cycle used did not cause a decrease in degradation for many compounds, successfully increasing the photonic efficiency without sacrificing performance.
Citation: Photochem
PubDate: 2022-07-01
DOI: 10.3390/photochem2030035
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 515-527: Optical and Structural Characteristics
of Rare Earth-Doped ZnO Nanocrystals Prepared in Colloidal Solution
Authors: Maria Toma, Oleksandr Selyshchev, Yevhenii Havryliuk, Aurel Pop, Dietrich R. T. Zahn
First page: 515
Abstract: ZnO nanocrystals doped with Nd, Gd, and Er were synthesized using a soft chemical process in ambient atmosphere. Pseudospherical and hexagonal nanocrystals (NC) of the wurtzite phase with a mean size of (7.4 ± 1.7) nm were obtained. The presence of rare earth (RE) dopants was confirmed by X-ray fluorescence (XRF) spectroscopy. The ZnO nanocrystals exhibited simultaneously narrow excitonic- and broad trap/surface-related photoluminescence (PL), both of which were affected by doping with RE atoms. Doping reduced the total PL intensity, suppressing the excitonic emission by a greater extent than the broad band PL. Also, doping resulted in a blue shift of the trap/surface-related emission, while the energy of the excitonic peak remained unchanged. Resonant Raman spectra additionally confirmed the wurtzite phase of ZnO NCs and revealed a shift of the A1-LO mode towards lower frequency upon doping that could be caused by the mass effect of RE atoms, point defects, and increases in charge carrier concentration. Fitting of the spectra with Voigt profiles showed better results with two surface optical (SO) phonon modes that were previously theoretically predicted for the wurtzite ZnO phase. The influence of RE doping on PL and Raman spectra can be explained by the incorporation of RE ions into the ZnO nanostructures, where the dopants act as non-radiative defects.
Citation: Photochem
PubDate: 2022-07-02
DOI: 10.3390/photochem2030036
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 528-538: Recent Advances in Aerobic
Photo-Oxidation over Small-Sized IB Metal Nanoparticles
Authors: Yifei Zhang, Meng Wang, Gao Li
First page: 528
Abstract: Aerobic photo-oxidation is a kind of green catalytic process that give valuable chemicals because of its mild reaction conditions and high product selectivity. Recently, small-sized IB metal nanoparticles (NPs; e.g., Cu, Ag, and Au, sized 1–3 nm) upon the surface of titanium oxide show excellent photocatalytic performance. The introduction of IB metal NPs can enhance the separation of photo-generated holes/electrons during photo-oxidations. In this account, we summarize the recent progress of small-sized IB metal NPs catalyzed by aerobic photo-oxidations, including the conversion of methanol, ethanol, sulfide, and benzylamine. More importantly, the structure–property correlations at the atomic level are detailed and discussed, e.g., the insights into the activation of oxygen and the identification of catalytic active sites. Future investigations are needed to carry out and reveal the catalytic mechanisms and conversion pathways.
Citation: Photochem
PubDate: 2022-07-13
DOI: 10.3390/photochem2030037
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 539-562: Photocatalyzed Production of Urea as a
Hydrogen–Storage Material by TiO2–Based Materials
Authors: Felipe Matamala-Troncoso, Mauricio Isaacs, César Sáez-Navarrete
First page: 539
Abstract: This review analyzes the photocatalyzed urea syntheses by TiO2–based materials. The most outstanding works in synthesizing urea from the simultaneous photocatalyzed reduction of carbon dioxide and nitrogen compounds are reviewed and discussed. Urea has been widely used in the agricultural industry as a fertilizer. It represents more than 50% of the nitrogen fertilizer market, and its global demand has increased more than 100 times in the last decades. In energy terms, urea has been considered a hydrogen–storage (6.71 wt.%) and ammonia–storage (56.7 wt.%) compound, giving it fuel potential. Urea properties meet the requirements of the US Department of Energy for hydrogen–storage substances, meanly because urea crystalizes, allowing storage and safe transportation. Conventional industrial urea synthesis is energy–intensive (3.2–5.5 GJ ton−1) since it requires high pressures and temperatures, so developing a photocatalyzed synthesis at ambient temperature and pressure is an attractive alternative to conventional synthesis. Due to the lack of reports for directly catalyzed urea synthesis, this review is based on the most prominent works. We provide details of developed experimental set–ups, amounts of products reported, the advantages and difficulties of the synthesis, and the scope of the technological and energetic challenges faced by TiO2–based photocatalyst materials used for urea synthesis. The possibility of scaling photocatalysis technology was evaluated as well. We hope this review invites exploring and developing a technology based on clean and renewable energies for industrial urea production.
Citation: Photochem
PubDate: 2022-07-15
DOI: 10.3390/photochem2030038
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 563-579: Vibrational-Excitation-Induced and
Spontaneous Conformational Changes in Solid Para-H2—Diminished
Matrix Effects
Authors: Sándor Góbi, Gopi Ragupathy, Gábor Bazsó, György Tarczay
First page: 563
Abstract: Both vibrational-excitation-induced (by (N)IR laser) and spontaneous (by H atom tunneling) conformational changes are often investigated by matrix-isolation spectroscopy. It is well known that rigid hosts, such as solid noble gases, N2, or normal-H2, can largely affect both the quantum efficiency of the (N)IR photon-induced process and the tunneling rate. In the present study, the conformational changes of formic and acetic acids, as well as glycine, were investigated in a soft quantum host, solid para-H2. It is shown that the tunneling rates in para-H2 are orders of magnitude larger than those in rigid hosts. Furthermore, our results also suggest that the quantum efficiencies of some (N)IR-light-induced conformational changes are larger than in rigid matrices. These results can open a door for the applications of para-H2 host in conformational and tunneling studies and can help understand the details of these complex processes.
Citation: Photochem
PubDate: 2022-07-26
DOI: 10.3390/photochem2030039
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 580-608: Progress in the Photoreforming of
Carboxylic Acids for Hydrogen Production
Authors: Anita Samage, Pooja Gupta, Mahaveer A. Halakarni, Sanna Kotrappanavar Nataraj, Apurba Sinhamahapatra
First page: 580
Abstract: Photoreforming is a process that connects the redox capability of photocatalysts upon light illumination to simultaneously drive the reduction of protons into hydrogen and the oxidation of organic substrates. Over the past few decades, researchers have devoted substantial efforts to enhancing the photocatalytic activity of the catalyst in hydrogen production. Currently, the realization of the potential of photocatalysts for simultaneous hydrogen production with value-added organics has motivated the research field to use the photo-oxidation path. As a distinct benefit, the less energetically demanding organic reforming is highly favorable compared to the slow kinetics of oxygen evolution, negating the need for expensive and/or harmful hole scavengers. Photocatalyst modifications, such as secondary component deposition, doping, defect, phase and morphology engineering, have been the main strategies adopted to tune the photo-oxidation pathways and oxidation products. The effect of the reaction parameters, including temperature, pH, reactant concentration and promising reactor strategies, can further enhance selectivity toward desired outcomes. This review provides a critical overview of photocatalysts in hydrogen production, including chemical reactions occurring with semiconductors and co-catalysts. The use of various oxygenates as sacrificial agents for hydrogen production is outlined in view of the transition of fossil fuels to clean energy. This review mainly focuses on recent development in the photoreforming of carboxylic acids, produced from the primary source, lignocellulose, through pyrolysis. The photo-oxidation of different carboxylic acids, e.g., formic acid, acetic acid and lactic acid, over different photocatalysts for hydrogen production is reviewed.
Citation: Photochem
PubDate: 2022-07-29
DOI: 10.3390/photochem2030040
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 609-627: Solid State Nanostructured Metal Oxides
as Photocatalysts and Their Application in Pollutant Degradation: A Review
Authors: Carlos Díaz, Marjorie Segovia, Maria Luisa Valenzuela
First page: 609
Abstract: Most dyes used in various industries are toxic and carcinogenic, thus posing a serious hazard to humans as well as to the marine ecosystem. Therefore, the impact of dyes released into the environment has been studied extensively in the last few years. Heterogeneous photocatalysis has proved to be an efficient tool for degrading both atmospheric and aquatic organic contaminants. It uses the sunlight in the presence of a semiconductor photocatalyst to accelerate the remediation of environmental contaminants and the destruction of highly toxic molecules. To date, photocatalysis has been considered one of the most appealing options for wastewater treatment due to its great potential and high efficiency by using sunlight to remove organic pollutants and harmful bacteria with the aid of a solid photocatalyst. Among the photocatalysts currently used, nanostructured metal oxide semiconductors have been among the most effective. This review paper presents an overview of the recent research improvements on the degradation of dyes by using nanostructured metal oxide semiconductors obtained by a solid-state method. Metal oxides obtained by this method exhibited better photocatalytic efficiency than nanostructured metal oxides obtained using other solution methods in several cases. The present review discusses examples of various nanostructured transition metal oxides—such as TiO2, Fe2O3, NiO, ReO3, IrO2, Rh2O3, Rh/RhO2, and the actinide ThO2—used as photocatalysts on methylene blue. It was found that photocatalytic efficiency depends not only on the bandgap of the metal oxide but also on its morphology. Porous nanostructured metal oxides tend to present higher photocatalytic efficiency than metal oxides with a similar band gap.
Citation: Photochem
PubDate: 2022-08-05
DOI: 10.3390/photochem2030041
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 628-650: Structural, Morphological and Optical
Properties of MoS2-Based Materials for Photocatalytic Degradation of
Organic Dye
Authors: Jadan Resnik Jaleel UC, Madhushree R, Sunaja Devi K R, Dephan Pinheiro, Mothi Krishna Mohan
First page: 628
Abstract: Molybdenum disulfide (MoS2) is a transition metal dichalcogenide (TMDCs) having versatile properties and plays a great role in the photodegradation of organic dyes. MoS2 also finds applications in diverse fields such as catalysis, electronics, and nanomedicine transportation. MoS2 can be prepared by using chemical and physical methods such as hydrothermal, solvothermal, and chemical vapour deposition methods. The preparation method employed can produce subtle but significant changes in the morphology. To increase the efficiency of MoS2, it can be combined with different materials to produce composites that improve the photodegradation efficiency of MoS2. The various methods of preparation, the morphology of MoS2, and photodegradation activity of the MoS2-based nanocomposites are briefly discussed in this review.
Citation: Photochem
PubDate: 2022-08-08
DOI: 10.3390/photochem2030042
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 651-671: Mechanistic Insights into Graphene Oxide
Driven Photocatalysis as Co-Catalyst and Sole Catalyst in Degradation of
Organic Dye Pollutants
Authors: Jai Prakash
First page: 651
Abstract: Photocatalysis is a promising route to utilize sunlight, which has been potentially used to solve energy as well as environmental problems with an emphasis on fundamental understanding and technological applications in society. Semiconductors are excellent photocatalysts but often show less efficient activities due to the fast recombination of photogenerated charge carriers and very slow kinetics of surface photochemical reactions. However, recent advancements show promising strategies to improve their photocatalytic activities, including surface modifications using suitable co-catalysts and the development of novel efficient photocatalysts. Graphene oxide (GO) is one of such nanomaterials which shows multifarious roles in photocatalysis with a great potential to act as an independent solar-driven sole photocatalyst. In this minireview, the photochemistry of GO has been discussed in view of its multifarious roles/mechanisms in improving the photocatalytic activity of metal oxide semiconductors, plasmonic nanomaterials, and also their nanocomposites. In addition, recent advancements and applications of such GO-based photocatalysts in photocatalytic degradation of organic dye pollutants, including engineering of GO as the sole photocatalyst, have been discussed. Furthermore, the challenges and future prospects for the development of GO-based photocatalysts are discussed.
Citation: Photochem
PubDate: 2022-08-17
DOI: 10.3390/photochem2030043
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 672-693: Consecutive Multicomponent
Coupling-Addition Synthesis and Chromophore Characteristics of
Cyclohexene-Embedded Merocyanines and Cyanines
Authors: Julian Papadopoulos, Tabea Gerlach, Guido J. Reiss, Bernhard Mayer, Thomas J. J. Müller
First page: 672
Abstract: Merocyanines with embedded butadiene structure in a cyclohexane scaffold are readily obtained by consecutive three-component alkynylation-addition sequences in moderate to excellent yield. Moreover, employing pyrrolidine as an amine provides a pseudo four-component synthesis of related cyanines by carbonyl condensation of the heterocyclic amine in excellent yield. While the merocyanines are essentially nonluminescent, pentamethine cyanines show luminescence with low quantum yield. TDDFT calculations using various exchange correlation hybrid functionals in the gas phase and explicit continuum of dichloromethane underline that the lowest energy absorption bands are highly solvent dependent for a merocyanine and cyanine model. The blue-shifted deviation from the experimental spectra agrees with related merocyanine and cyanine systems. The lowest energy absorption band of merocyanines contains n-π* character, which rationalizes the absence of luminescence.
Citation: Photochem
PubDate: 2022-08-19
DOI: 10.3390/photochem2030044
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 694-716: A Photochemical Overview of Molecular
Solar Thermal Energy Storage
Authors: Alberto Gimenez-Gomez, Lucien Magson, Beatriz Peñin, Nil Sanosa, Jacobo Soilán, Raúl Losantos, Diego Sampedro
First page: 694
Abstract: The design of molecular solar fuels is challenging because of the long list of requirements these molecules have to fulfil: storage density, solar harvesting capacity, robustness, and heat release ability. All of these features cause a paradoxical design due to the conflicting effects found when trying to improve any of these properties. In this contribution, we will review different types of compounds previously suggested for this application. Each of them present several advantages and disadvantages, and the scientific community is still struggling to find the ideal candidate suitable for practical applications. The most promising results have been found using norbornadiene-based systems, although the use of other alternatives like azobenzene or dihydroazulene cannot be discarded. In this review, we primarily focus on highlighting the optical and photochemical aspects of these three families, discussing the recently proposed systems and recent advances in the field.
Citation: Photochem
PubDate: 2022-08-22
DOI: 10.3390/photochem2030045
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 717-732: Awakening a Molecular Mummy: The
Inter-and Intramolecular Photochemistry of Pyromellitic Diimides with
Alkyl Carboxylates
Authors: Wolfgang H. Kramer, Donya Razinoubakht, Gurjit Kaur, Axel Klein, Simon Garbe, Jörg Neudörfl, Sabrina Molitor, Anne Zimmer, Axel G. Griesbeck
First page: 717
Abstract: Pyromellitic acid diimides are not as chemically unreactive as conjecturable (and presupposed) from their numerous applications as electron acceptor units or electron carriers in molecular donor–acceptor dyads or triads. Similar to the corresponding phthalimides, electronically excited pyromellitic diimides oxidize alkyl carboxylates in aqueous solution via intermolecular electron transfer (PET) processes, which eventually results in radical–radical combination products, e.g., the benzylation product 6 from N,N′-dimethyl pyromellitic diimide 5. The analogous product 7 was formed with pivalic acid as tert-butyl radical source. One additional product 8 was isolated from alkylation/dearomatization and multiple radical additions, respectively, after prolonged irradiation. In intramolecular versions, from N-carboxyalkylated pyromellitic diimides 9a–e (C1 to C5-spaced), degradation processes were detected, e.g., the cyclization products 10 from the GABA substrate 9c. In sharp contrast to phthalimide photochemistry, the green pyromellitic diimide radical anion was detected here by UV-vis absorption (λabs = 720 nm), EPR (from 9d), and NMR spectroscopy for several intramolecular electron transfer examples. Only the yellow 1,4-quinodial structure is formed from intermolecular PET, which was deduced from the absorption spectra (λabs = 440 nm) and the subsequent chemistry. The pyromellitimide radical anion lives for hours at room temperature in the dark, but is further degraded under photochemical reaction conditions.
Citation: Photochem
PubDate: 2022-08-24
DOI: 10.3390/photochem2030046
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 733-751: Low-Cost and Recyclable Photocatalysts:
Authors: Timur Borjigin, Michael Schmitt, Fabrice Morlet-Savary, Pu Xiao, Jacques Lalevée
First page: 733
Abstract: Novel metal oxide/polymer composite photocatalysts prepared by photocuring with common metal oxide particles (ZnO or CeO2) and acrylic ester monomers have been investigated for the first time. Metal oxide particles were fully integrated with the acrylate polymer network based on the crosslink of poly ethylene glycol diacrylate (noted below as Poly-PEG) by photopolymerization upon mild light source (LED@405 nm) irradiation. The prepared metal/oxide composite showed excellent performance in the photodegradation of Acid Black dye (used as a benchmark pollutant) in an aqueous environment. Indeed, under UV lamp irradiation for 60 min, the degradation of Acid Black reached 59% and 56%, in the presence of 10 wt% ZnO/Poly-PEG and 3 wt% CeO2/poly PEG, respectively. Markedly, the new reported photocatalysts have offered much better performance over the conventional TiO2 photocatalytic material used as a control (39% degradation using 1 wt% TiO2/poly PEG). In turn, the new proposed metal oxide/polymer composites were further characterized by a range of analytical characterization methods, including the swelling test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), dynamic mechanical analysis (DMA), UV–visible diffuse reflectance spectroscopy, and electron spin resonance analysis. The results showed that the new photocatalysts demonstrated excellent water adsorption properties, high-temperature resistance, and excellent recyclability, which were very suitable for wide application and in line with the concept of green chemistry.
Citation: Photochem
PubDate: 2022-08-24
DOI: 10.3390/photochem2030047
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 752-764: Decoding Breast Cancer Metabolism:
Hunting BRCA Mutations by Raman Spectroscopy
Authors: Monika Kopec, Beata Romanowska-Pietrasiak, Halina Abramczyk
First page: 752
Abstract: Presented study included human blood from healthy people and patients with BReast CAncer gene (BRCA) mutation. We used Raman spectroscopy for BRCA mutation detection and the bioanalytical characterization of pathologically changed samples. The aim of this study is to evaluate the Raman biomarkers to distinguish blood samples from healthy people and patients with BRCA mutation. We demonstrated that Raman spectroscopy is a powerful technique to distinguish between healthy blood and blood with BRCA mutation and to characterize the biochemical composition of samples. We applied partial least squares discriminant analysis (PLS-DA) to discriminate BRCA1/2 mutations and control samples without the mutations based on vibrational features. The sensitivity and specificity for calibration obtained directly from PLS-DA are equal to 94.2% and 97.6% and for cross-validation are equal to 93.3% and 97%. Our combination (Raman spectroscopy and PLS-DA) provides quick methods to reliably visualize the biochemical differences in human blood plasma. We proved that Raman spectroscopy combined with the chemometric method is a promising tool for hunting BRCA mutation in breast cancer.
Citation: Photochem
PubDate: 2022-08-25
DOI: 10.3390/photochem2030048
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 765-778: Ar-Matrix Studies of the Photochemical
Reaction between CS2 and ClF: Prereactive Complexes and Bond Isomerism of
the Photoproducts
Authors: Michelle T. Custodio Castro, Carlos O. Della Védova, Helge Willner, Rosana M. Romano
First page: 765
Abstract: In this work, prereactive complexes, reaction products, and conformational preferences derived from the photochemical reaction between CS2 and ClF were analyzed following the codeposition of the reactants trapped in argon matrices at cryogenic temperatures. After codeposition of CS2 and ClF diluted in Ar, the formation of van der Waals complexes is observed. When the mixture is subsequently irradiated by means of broad-band UV-visible light (225 ≤ λ ≤ 800 nm), fluorothiocarbonylsulfenyl chloride (FC(S)SCl) and chlorothiocarbonylsulfenyl fluoride (ClC(S)SF) are produced. These species exist as two stable planar anti- and syn-conformers (anti- and syn- of the C=S double bond with respect to the S–Cl or S–F single bond, respectively). For both novel molecules, anti-FC(S)SCl and anti-ClC(S)SF are the lowest-energy computed rotamers. As expected due to the photochemical activity of these species, additional reaction products due to alternative or subsequent photochannels are formed during this process.
Citation: Photochem
PubDate: 2022-09-02
DOI: 10.3390/photochem2030049
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 779-797: An Insight into the Bicarbonate Effect
in Photosystem II through the Prism of the JIP Test
Authors: Alexandr V. Shitov
First page: 779
Abstract: Photosystem II (PSII) is the unique pigment–protein complex that is capable of evolving molecular oxygen using solar energy. The activity of PSII determines the overall productivity of all oxygenic photosynthetic organisms. It is well known that the absence of HCO3− induces a drop in the activity of PSII. However, it is not yet clear what type of photochemical reaction, single turn-over or multiple turn-over, HCO3− is involved in. Kinetic parameters of this (these) involvement(s) are almost unexplored now. This work addresses these issues. Using the JIP test, being the perspective noninvasive method for measuring PSII activity in plants, this paper describes how HCO3− deficiency affects the electron transfer on the oxidizing as well as the reducing sides of PSII in thylakoids and in PSII preparations from the leaves of pea plants. HCO3− was found to be simultaneously involved both in single turn-over and in multiple turn-over events (“dynamical processes”). Moreover, the involvement of HCO3− in dynamical photochemical processes was revealed to be associated with both sides of PSII, being the rate limiting on the reducing side, which follows from obtained kinetic parameters. The involvement of HCO3− in dynamical processes as the constant exchangeable ligand is discussed for both the electron donor and acceptor sides of PSII.
Citation: Photochem
PubDate: 2022-09-15
DOI: 10.3390/photochem2030050
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 798-809: Mass-Resolved Momentum Imaging of Three
Dichloroethylene Isomers by Femtosecond Laser-Induced Coulomb Explosion
Authors: Yoriko Wada, Hiroshi Akagi, Takayuki Kumada, Ryuji Itakura, Tomonari Wakabayashi
First page: 798
Abstract: Coulomb explosion experiments using linearly polarized intense 60 fs laser pulses were conducted for structural characterization of three dichloroethylene (DCE) isomers, 1,1-DCE, cis-1,2-DCE, and trans-1,2-DCE. Under relatively low laser intensity at 1.8 × 1014 W/cm2, mass-resolved momentum imaging (MRMI) for selected fragment ions of 35Cl+ and C2+ revealed different patterns for the three isomers. The C2+ ion fragmented from multiply charged trans-1,2-DCE was forced to leave perpendicularly to the direction of the laser polarization, due to recoil forces from adjacent cations. In contrast, the fast ions of C2+ from cis-1,2-DCE exhibited an isotropic distribution, whereas the fast ions of C2+ from 1,1-DCE recoiled along the laser polarization together with the slow C2+ ions, and thereby distinction of the three isomers was demonstrated. Coulomb explosion occurs predominantly at specific orientation, which is useful for potential applications of MRMI analysis to molecular structure assays.
Citation: Photochem
PubDate: 2022-09-16
DOI: 10.3390/photochem2030051
Issue No: Vol. 2, No. 3 (2022)
- Photochem, Vol. 2, Pages 237-262: Water Clusters in Interaction with
Corannulene in a Rare Gas Matrix: Structures, Stability and IR Spectra
Authors: Heloïse Leboucher, Joëlle Mascetti, Christian Aupetit, Jennifer A. Noble, Aude Simon
First page: 237
Abstract: The interaction of polycyclic aromatic hydrocarbons (PAHs) with water is of paramount importance in atmospheric and astrophysical contexts. We report here a combined theoretical and experimental study of corannulene-water interactions in low temperature matrices and of the matrix’s influence on the photoreactivity of corannulene with water. The theoretical study was performed using a mixed density functional based tight binding/force field approach to describe the corannulene-water clusters trapped in an argon matrix, together with Born-Oppenheimer molecular dynamics to determine finite-temperature IR spectra. The results are discussed in the light of experimental matrix isolation FTIR spectroscopic data. We show that in the solid phase, π isomers of (C20H10)(H2O)n, with n = 2 or 3, are energetically favored. These π complexes are characterized by small shifts in corannulene vibrational modes and large shifts in water bands. These π structures, particularly stable in the case of the water trimer where the water cluster is trapped “inside” the corannulene bowl, may account for the difference in photoreactivity of non-planar–compared to planar–PAHs with water. Indeed, planar PAHs such as pyrene and coronene embedded in H2O:Ar matrices form σ isomers and react with water to form alcohols and quinones under low energy UV irradiation, whereas no photoreactivity was observed for corannulene under the same experimental conditions.
Citation: Photochem
PubDate: 2022-03-25
DOI: 10.3390/photochem2020018
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 263-271: Phosphorescence of C5N− in
Rare Gas Solids
Authors: Urszula Szczepaniak, Robert Kołos, Jean-Claude Guillemin, Claudine Crépin
First page: 263
Abstract: Phosphorescence of C5N− was discovered following the ArF-laser (193 nm) photolysis of cyanodiacetylene (HC5N) isolated in cryogenic argon, krypton, and xenon matrices. This visible emission, with an origin around 460 nm, is vibrationally resolved, permitting the measurement of frequencies for eight ground-state fundamental vibrational modes, including the three known from previous IR absorption studies. Phosphorescence lifetime amounts to tens or even hundreds of ms depending on the matrix host; it is five times longer than in the case of HC5N.
Citation: Photochem
PubDate: 2022-03-28
DOI: 10.3390/photochem2020019
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 272-298: Photoelectrochemical Energy Conversion
over 2D Materials
Authors: Ali Raza, Xinyu Zhang, Sarfraz Ali, Changhai Cao, Arslan Ahmed Rafi, Gao Li
First page: 272
Abstract: The solar motivated photoelectrochemical (PEC), used in water splitting systems, shows superior talent in converting solar energy in the form of cleaning and in sustaining a chemical energy evolution. PEC systems present by integrating a photoelectrode, which involves light-harvesting to absorb solar energy, thereby introducing an interlayer for the transformation of photogenerated electrons and holes, along with a co-catalyst to trigger oxidation and reduce the chemical reactions. In this review, we describe a variety of two-dimensional (2D) layered photoanodes and photocathodes, such as graphitic carbon nitrides, transition metal dichalcogenides, layered double hydroxides, MXenes, and co-catalysts for the assembly of combined photoelectrodes belonging to oxygen evolution and/or hydrogen evolution chemical reactions. The basic principles of PEC water splitting associated with physicochemical possessions relating to photoelectrodes unified with catalytic chemical reactions have been investigated. Additionally, the mechanisms attributing to a relationship with 2D photoelectrodes have been incorporated as a supplementary discussion. The improvement strategies, which include the construction of heterostructures, surface functionalization, and formations of heterojunctions, have also been discussed. The issues and challenges relevant to the field have been acknowledged for facilitating future research, indicating optimized conversion activity corresponding to PEC water splitting.
Citation: Photochem
PubDate: 2022-03-30
DOI: 10.3390/photochem2020020
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 299-307: Energy Relaxation of Porphycene in
Atomic and Molecular Cryogenic Matrices
Authors: Jacek Dobkowski, Igor V. Sazanovich, Aleksander Gorski, Jacek Waluk
First page: 299
Abstract: The kinetics of relaxation of high-lying electronic states of porphycene (porphyrin isomer) embedded in different cryogenic matrices were studied using picosecond time-resolved fluorescence (TRF) and transient absorption (TA) techniques. The molecule was excited into the Soret band, i.e., with a large energy excess compared to that of the lowest (Q) excited state. The TRF and TA time profiles obtained for porphycene embedded in argon and methane matrices were remarkably different: the overall relaxation in argon occurred in 64 ps, whereas the corresponding value for methane matrix was 18 ps. Analysis of the evolution over time of different spectral ranges of TRF spectra indicates the multidimensional character of relaxation kinetics.
Citation: Photochem
PubDate: 2022-04-06
DOI: 10.3390/photochem2020021
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 308-325: Structure-Function-Environment
Relationship of the Isomers Zeaxanthin and Lutein
Authors: Barbara Demmig-Adams, Stephanie K. Polutchko, William W. Adams
First page: 308
Abstract: A synthesis is provided of the roles of the carotenoids zeaxanthin and/or lutein in opposing (i) photodamage in plants, (ii) photodamage to the human eye as well as cognitive dysfunction and a host of human diseases and disorders, and (iii) damage to extremophile microorganisms in the most inhospitable environments on earth. Selected examples are used to examine microenvironments and basic biological structures with which these xanthophylls associate as well as the effect of the organisms’ external environment. An overview is presented of the multiple principal mechanisms through which these xanthophylls can directly or indirectly impact organisms’ internal redox (oxidant/antioxidant) balance that provides input into the orchestration of growth, development, and defense in prokaryotic microorganisms, plants, and humans. Gaps in the research are identified, specifically with respect to the need for further in vivo assessment of the mechanisms.
Citation: Photochem
PubDate: 2022-04-18
DOI: 10.3390/photochem2020022
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 326-344: Electronic Absorption, Emission, and
Two-Photon Absorption Properties of Some Extended
2,4,6-Triphenyl-1,3,5-Triazines
Authors: Alison G. Barnes, Nicolas Richy, Anissa Amar, Mireille Blanchard-Desce, Abdou Boucekkine, Olivier Mongin, Frédéric Paul
First page: 326
Abstract: We report herein the linear optical properties of some extended 2,4,6-triphenyl-s-triazines of formula 2,4,6-[(1,4-C6H4)C≡C(4-C6H4X)]3-1,3,5-(C3H3N3) (3-X; X = NO2, CN, OMe, NMe2, NPh2) and related analogues 4 and 7-X (X = H, NPh2), before briefly discussing their two-photon absorption (2PA) cross-sections. Their 2PA performance is discussed in relation to 2PA values previously measured for closely related octupoles such as N,N′,N″-triphenylisocyanurates (1-X, 5, and 6-X) or 1,3,5-triphenylbenzenes (2-X). While s-triazines are usually much better two-photon absorbers in the near-IR range than these molecules, especially when functionalised by electron-releasing substituents at their periphery, they present a decreased transparency window in the visible range due to their red-shifted first 1PA peak, in particular when compared with corresponding isocyanurates analogues. In contrast, due to their significantly larger two-photon brilliancy, 2,4,6-triphenyl-s-triazines appear more promising than the latter for two-photon fluorescence bio-imaging purposes. Rationalisation of these unexpected outcomes is proposed based on DFT calculations.
Citation: Photochem
PubDate: 2022-05-19
DOI: 10.3390/photochem2020023
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 345-357: Solution and Solid-State Optical
Properties of Trifluoromethylated
5-(Alkyl/aryl/heteroaryl)-2-methyl-pyrazolo[1,5-a]pyrimidine System
Authors: Felipe S. Stefanello, Jean C. B. Vieira, Juliane N. Araújo, Vitória B. Souza, Clarissa P. Frizzo, Marcos A. P. Martins, Nilo Zanatta, Bernardo A. Iglesias, Helio G. Bonacorso
First page: 345
Abstract: This paper describes the photophysical properties of a series of seven selected examples of 5-(alkyl/aryl/heteroaryl)-2-methyl-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidines (3), which contain alkyl, aryl, and heteroaryl substituents attached to the scaffolds of 3. Given the electron-donor groups and -withdrawing groups, the optical absorption and emission in the solid state and solution showed interesting results. Absorption UV–Vis and fluorescence properties in several solvents of a pyrazolo[1,5-a]pyrimidines series were investigated, and all derivatives were absorbed in the ultraviolet region despite presenting higher quantum emission fluorescence yields in solution and moderate emission in the solid state. Moreover, the solid-state thermal stability of compounds 3a–g was assessed using thermogravimetric analysis. The thermal decomposition profile showed a single step with almost 100% mass loss for all compounds 3. Additionally, the values of T0.05 are considerably low (72–187 °C), especially for compound 3a (72 °C), indicating low thermal stability for this series of pyrazolo[1,5-a]pyrimidines.
Citation: Photochem
PubDate: 2022-05-19
DOI: 10.3390/photochem2020024
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 358-375: Photooxidation of
2,2′-(Ethyne-1,2-diyl)dianilines: An Enhanced Photocatalytic
Properties of New Salophen-Based Zn(II) Complexes
Authors: Mahesh Subburu, Ramesh Gade, Prabhakar Chetti, Someshwar Pola
First page: 358
Abstract: Under solvothermal conditions, the Zn(II) complexes formed from salophen-based ligands with N and O donor atoms are reported. These Zn(II) complexes were initially confirmed through elemental analysis and supported by mass spectral data. The purity of the ligands and Zn(II) complexes was confirmed by using NMR spectral studies. The functional group complexation was established by FT-IR analysis. Additional supportive information about the complexes is also reported through molar conductance and thermal studies. The bandgap energies of the ligands and Zn(II) complexes are estimated with UV-visible DRS studies. The rate of recombination of hole–electron pairs is directly related to photocatalytic activity, which is confirmed by using emission spectral analysis. The surface metaphors for ligands and complexes are obtained from FESEM analysis. These new sequences of Zn(II) complexes were used for the photooxidation of 2,2′-(ethyne-1,2-diyl)dianiline and its derivatives. Mechanistic studies on the fast degradation of dyes were supported in the presence of several scavengers. The rapid photooxidation process in the presence of [Zn(CPAMN)] has been demonstrated, and a highly efficient photocatalyst for the photooxidation of 2,2′-(ethyne-1,2-diyl) dianiline has been proposed. Furthermore, the experimental findings are supported by the DFT studies.
Citation: Photochem
PubDate: 2022-05-23
DOI: 10.3390/photochem2020025
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 376-389: UV-Induced Benzyloxy Rotamerization in
an Ortho OH-Substituted Aryl Schiff Base
Authors: İsa Sıdır, Yadigar Gülseven Sıdır, Sándor Góbi, Halil Berber, Rui Fausto
First page: 376
Abstract: A new benzyloxy containing ortho hydroxyl-substituted aryl Schiff base, trans 2-((2-(benzyloxy)benzylidene) amino)phenol (abbreviated as BBAP), was synthesized and characterized by 1H-, 13C-NMR and infrared spectroscopic techniques and elemental analysis. The conformational landscape of the compound, as well as its infrared spectra in argon and N2 cryogenic matrices (10 K) were investigated, followed by the study of the effects of in situ UV irradiation of the matrix-isolated compound. The structural information was obtained through an extensive series of quantum chemical calculations performed at the DFT(B3LYP)/6-311++G(d,p) level of theory, which enabled to identify 3 low-energy OH···N intramolecularly H-bonded conformers of the molecule that were later found to be present in the as-deposited cryogenic matrices. The 3 experimentally relevant conformers of BBAP differ in the geometry of the benzyloxy substituent, and were discovered to interconvert upon in situ UV irradiation (λ = 230 nm) of the matrix-isolated compound. This is the first report on UV-induced conformational changes taking place in a benzyloxy fragment for a matrix-isolated compound.
Citation: Photochem
PubDate: 2022-05-25
DOI: 10.3390/photochem2020026
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 390-404: Photochemistry of Metal Nitroprussides:
State-of-the-Art and Perspectives
Authors: Paula M. Crespo, Oscar F. Odio, Edilso Reguera
First page: 390
Abstract: This contribution summarizes the current state in the photochemistry of metal nitroprussides, which is dominated by the electronic structure of the nitrosyl group. From the combination of p orbitals of the nitrogen and oxygen atoms in the NO+ ligand, a π*NO molecular orbital of relatively low energy is formed, which has π*2px and π*2py character. This is a double degenerate orbital. When the nitrosyl group is found coordinated to the iron atom in the nitroprusside ion, the availability of that low energy π*NO orbital results in light-induced electronic transitions from the iron atom dxy, dxz and dyz orbitals, 2b2 (xy) → 7e (π*NO) and 6e (xz,yz) → 7e (π*NO), which are observed at 498 and 394 nm, respectively. These light-induced transitions and the possibility of NO isomer formation dominate the photochemistry of metal nitroprussides. In this feature paper, we discuss the implications of such transitions in the stability of coordination compounds based on the nitroprusside ion in the presence of water molecules for both 3D and 2D structures, including the involved degradation mechanisms. These photo-induced electronic transitions modify the physical and functional properties of solids where the nitroprusside ion forms part of their structure and appear as an opportunity for tuning their magnetic, electrical, optical and as energy-applied materials, for instance. This contribution illustrates these opportunities with results from some recently reported studies, and possible research subjects, even some not explored, are mentioned.
Citation: Photochem
PubDate: 2022-05-31
DOI: 10.3390/photochem2020027
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 405-422: Conformational Structure, Infrared
Spectra and Light-Induced Transformations of Thymol Isolated in Noble Gas
Cryomatrices
Authors: Antόnio Jorge Lopes Jesus, Cláudio M. Nunes, Igor Reva
First page: 405
Abstract: The conformational space of the natural product thymol (2-isopropyl-5-methylphenol) was investigated using quantum chemical calculations at the B3LYP and MP2 levels, which revealed the existence of four types of conformers differing in the orientation of the isopropyl and hydroxyl groups. Thymol monomers were isolated in noble gas (Ar and Xe) matrices (at 15 K) and characterized by IR spectroscopy. With the support of B3LYP harmonic vibrational calculations, the two most stable trans-OH-conformers, differing in the isopropyl orientation, were identified in the cryomatrices. The two less stable cis-OH conformers were not detected as they shall undergo fast tunneling to the most stable ones. Annealing experiments in a Xe matrix up to 75 K did not lead to any conversion between the two isolated conformers, which is in accordance with the significative energy barrier computed for rotamerization of the bulky isopropyl group (~24 kJ mol−1). Vibrational excitation promoted by broadband or by narrowband irradiation, at the 2ν(OH) frequencies of the isolated conformers, did not lead to any conversion either, which was interpreted in terms of a more efficient energy transfer to the hydroxyl rotamerization (associated with a lower energy barrier and a light H-atom) than to the isopropyl rotamerization coordinate. Broadband UV irradiation experiments (λ > 200 nm) led to a prompt transformation of matrix isolated thymol, with spectroscopic evidence suggesting the formation of isomeric alkyl-substituted cyclohexadienones, Dewar isomers and open-chain conjugated ketenes. The photochemical mechanism interpretation concords with that reported for analogous phenol derivatives.
Citation: Photochem
PubDate: 2022-06-07
DOI: 10.3390/photochem2020028
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 423-434: Fluorescence and Phosphorescence of
Flavylium Cation Analogues of Anthocyanins
Authors: Gustavo T. M. Silva, Cassio P. Silva, Karen M. Silva, Renan M. Pioli, Tássia S. Costa, Vinícius V. Marto, Adilson A. Freitas, Jennifer Rozendo, Lucas M. O. S. Martins, Victor F. Cavalcante, Liuqing Sun, Adelia J. A. Aquino, Vânia M. T. Carneiro, Frank H. Quina
First page: 423
Abstract: Fluorescence spectra and lifetimes were determined for 16 synthetic flavylium cation analogues of anthocyanin plant pigments in dry acetonitrile acidified with trifluoroacetic acid (TFA). Phosphorescence was also observed from the lowest excited triplet state for all of the flavylium cations at 77 K in a rigid TFA-acidified isopropanol glass. The fluorescence quantum yields and lifetimes depend in a systematic manner on the nature and position of the substituents on the flavylium chromophore and three specific substitution patterns associated with significant decreases in the fluorescence quantum yield were identified. A 4′-bromo or 4′-iodo substituent in the B-ring of the flavylium cation produced a small but normal heavy-atom effect, reducing the fluorescence quantum yield and the phosphorescence lifetime relative to analogues without the halogen atom. In contrast, three flavylium cations with a 3′-bromo substituent exhibited an “inverse” heavy atom effect, i.e., an increase in the fluorescence quantum yield rather than a decrease, which was rationalized on the basis of the nodal properties of the natural transition orbitals (NTOs) involved in the S0→S1 radiative transition.
Citation: Photochem
PubDate: 2022-06-08
DOI: 10.3390/photochem2020029
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 435-447: UV-Vis Spectrophotometer as an
Alternative Technique for the Determination of Hydroquinone in Vinyl
Acetate Monomer
Authors: Md Al Mamunur Rashid, Mofizur Rahman, ASM Obaidullah Mahmud, Ali Shazzad Mohammad Morshed, Md Masudul Haque, Md Mobarak Hossain
First page: 435
Abstract: As an appropriate quantity of hydroquinone (HQ) is essential to safeguard inhibition characteristics by eliminating the risk of self-polymerization of vinyl acetate monomer (VAM), the determination of the HQ content in VAM is very crucial to ensure the stability of VAM during storage and transportation as well as to achieve the possibility of a proper polymerization reaction. In this study, a simple, cheap, time-saving, and easy method has been developed by which the HQ content in VAM can be measured quickly based on the measurement of UV-Vis absorbance of the HQ content at 293 nm using methanol as a blank. No color development is required for this determination process, and the HQ content in the VAM can be measured directly without any further processing. The limit of detection, limit of quantification, linearity range, accuracy, precision, robustness, and measurement uncertainty of this method have been measured and analyzed and found to be within the acceptable limit and range. The method shows linearity within 0.36–25.0 ppm HQ content in the solution range with a regression coefficient of 0.9999, a relative spike recovery of 101.35%, precision of 1.36%, relative bias of 0.55%, and robustness with a temperature variation of −5 °C.
Citation: Photochem
PubDate: 2022-06-15
DOI: 10.3390/photochem2020030
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 448-462: Phototransformations of
2,3-Diamino-2-Butenedinitrile (DAMN) Monomers Isolated in Low-Temperature
Argon Matrix
Authors: Igor Reva, Hanna Rostkowska, Leszek Lapinski
First page: 448
Abstract: UV-induced transformations were studied for monomers of 2,3-diamino-2-butenedinitrile (DAMN) isolated in argon matrices. Photoinduced hydrogen-atom transfer was found to be the major process occurring upon UV (λ > 320 nm or λ > 295 nm) excitation of matrix-isolated DAMN monomers. As a result of the transfer of a hydrogen atom from an amino group to a nitrile fragment, a tautomer of DAMN involving a ketenimine group was generated. Identification of this photo-produced species was based on comparison of its experimental IR spectrum with the spectrum theoretically predicted for the ketenimine form. Another product photogenerated upon UV (λ > 320 nm, λ > 295 nm, or λ > 270 nm) irradiation of DAMN isolated in Ar matrices was identified as 4-amino-1H-imidazole-5-carbonitrile (AICN). The structure of this photoproduct was unambiguously assigned on the basis of an exact match of wavenumbers of the bands in the IR spectrum of this photogenerated species and the wavenumbers of IR bands of AICN trapped (in a separate experiment) from the gas phase into an Ar matrix.
Citation: Photochem
PubDate: 2022-06-16
DOI: 10.3390/photochem2020031
Issue No: Vol. 2, No. 2 (2022)
- Photochem, Vol. 2, Pages 9-31: Photophysics and Electrochemistry of
Authors: Eli Misael Espinoza, John Anthony Clark, Mimi Karen Billones, Gustavo Thalmer de Medeiros Silva, Cassio Pacheco da Silva, Frank Herbert Quina, Valentine Ivanov Vullev
First page: 9
Abstract: Natural dyes and pigments offer incomparable diversity of structures and functionalities, making them an excellent source of inspiration for the design and development of synthetic chromophores with a myriad of emerging properties. Formed during maturation of red wines, pyranoanthocyanins are electron-deficient cationic pyranoflavylium dyes with broad absorption in the visible spectral region and pronounced chemical and photostability. Herein, we survey the optical and electrochemical properties of synthetic pyranoflavylium dyes functionalized with different electron-donating and electron-withdrawing groups, which vary their reduction potentials over a range of about 400 mV. Despite their highly electron-deficient cores, the exploration of pyranoflavyliums as photosensitizers has been limited to the “classical” n-type dye-sensitized solar cells (DSSCs) where they act as electron donors. In light of their electrochemical and spectroscopic properties, however, these biomimetic synthetic dyes should prove to be immensely beneficial as chromophores in p-type DSSCs, where their ability to act as photooxidants, along with their pronounced photostability, can benefit key advances in solar-energy science and engineering.
Citation: Photochem
PubDate: 2022-01-06
DOI: 10.3390/photochem2010003
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 32-57: Nanostructured Luminescent Micelles:
Efficient “Functional Materials” for Sensing Nitroaromatic and
Nitramine Explosives
Authors: Shashikana Paria, Prasenjit Maity, Rafia Siddiqui, Ranjan Patra, Shubhra Bikash Maity, Atanu Jana
First page: 32
Abstract: Luminescent micelles are extensively studied molecular scaffolds used in applied supramolecular chemistry. These are particularly important due to their uniquely organized supramolecular structure and chemically responsive physical and optical features. Various luminescent tags can be incorporated with these amphiphilic micelles to create efficient luminescent probes that can be utilized as “chemical noses” (sensors) for toxic and hazardous materials, bioimaging, drug delivery and transport, etc. Due to their amphiphilic nature and well-defined reorganized self-assembled geometry, these nano-constructs are desirable candidates for size and shape complementary guest binding or sensing a specific analyte. A large number of articles describing micellar fluorogenic probes are reported, which are used for cation/anion sensing, amino acid and protein sensing, drug delivery, and chemo-sensing. However, this particular review article critically summarizes the sensing application of nitroaromatic (e.g., trinitrotoluene (TNT), trinitrobenzene (TNB), trinitrophenol (TNP), dinitrobenzene (DNB), etc.) and nitramine explosives (e.g., 1,3,5-trinitro-1,3,5-triazinane, trivially named as “research department explosive” (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, commonly known as “high melting explosive” (HMX) etc.). A deeper understanding on these self-assembled luminescent “functional materials” and the physicochemical behavior in the presence of explosive analytes might be helpful to design the next generation of smart nanomaterials for forensic applications. This review article will also provide a “state-of-the-art” coverage of research involving micellar–explosive adducts demonstrating the intermolecular charge/electron transfer (CT/ET) process operating within the host–guest systems.
Citation: Photochem
PubDate: 2022-01-10
DOI: 10.3390/photochem2010004
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 58-68: A P-61 Black Widow Inspired Palladium
Biladiene Complex for Efficient Sensitization of Singlet Oxygen Using
Visible Light
Authors: Anthony T. Rice, Glenn P. A. Yap, Joel Rosenthal
First page: 58
Abstract: Photodynamic therapy (PDT) is a promising treatment option that ablates cancerous cells and tumors via photoinduced sensitization of singlet oxygen. Over the last few decades, much work has been devoted to the development of new photochemotherapeutic agents for PDT. A wide variety of macrocyclic tetrapyrrole based photosensitizers have been designed, synthesized and characterized as PDT agents. Many of these complexes have a variety of issues that pose a barrier to their use in humans, including biocompatibility, inherent toxicity, and synthetic hurdles. We have developed a non-traditional, non-cyclic, and non-aromatic tetrapyrrole ligand scaffold, called the biladiene (DMBil1), as an alternative to these traditional photosensitizer complexes. Upon insertion of a heavy atom such as Pd2+ center, Pd[DMBil1] generates singlet oxygen in substantial yields (ΦΔ = 0.54, λexc = 500 nm) when irradiated with visible light. To extend the absorption profile for Pd[DMBil1] deeper into the phototherapeutic window, the tetrapyrrole was conjugated with alkynyl phenyl groups at the 2- and 18-positions (Pd[DMBil2-PE]) resulting in a significant redshift while also increasing singlet oxygen generation (ΦΔ = 0.59, 600 nm). To further modify the dialkynyl-biladiene scaffold, we conjugated a 1,8-diethynylanthracene with to the Pd[DMBil1] tetrapyrrole in order to further extend the compound’s π-conjugation in a cyclic loop that spans the entire tetrapyrrole unit. This new compound (Pd[DMBil2-P61]) is structurally reminiscent of the P61 Black Widow aircraft and absorbs light into the phototherapeutic window (600–900 nm). In addition to detailing the solid-state structure and steady-state spectroscopic properties for this new biladiene, photochemical sensitization studies demonstrated that Pd[DMBil2-P61] can sensitize the formation of 1O2 with quantum yields of ΦΔ = 0.84 upon irradiation with light λ = 600 nm. These results distinguish the Pd[DMBil2-P61] platform as the most efficient biladiene-based singlet oxygen photosensitizer developed to date. When taken together, the improved absorption in the phototherapeutic window and high singlet oxygen sensitization efficiency of Pd[DMBil2-P61] mark this compound as a promising candidate for future study as an agent of photodynamic cancer therapy.
Citation: Photochem
PubDate: 2022-01-11
DOI: 10.3390/photochem2010005
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 69-76: Demonstration of a Stereospecific
Photochemical Meta Effect
Authors: Hoai Pham, Madelyn Hunsley, Chou-Hsun Yang, Haobin Wang, Scott M. Reed
First page: 69
Abstract: A fundamental goal of photochemistry is to understand how structural features of a chromophore can make specific bonds within a molecule prone to cleavage by light, or photolabile. The meta effect is an example of a regiochemical explanation for photolability, in which electron donating groups on an aromatic ring cause photolability selectively at the meta position. Here, we show, using a chromophore containing one ring with a meta-methoxy group and one ring with a para-methoxy group, that two stereoisomers of the same compounds can react with light differently, based simply on the three-dimensional positioning of a meta anisyl ring. The result is that the stereoisomers of the compound with the same configuration at both stereogenic centers are photolabile while the stereoisomers with opposite configuration do not react with light. Furthermore, time-dependent density functional theory (TD-DFT) calculations show distinct excitation pathways for each stereoisomer.
Citation: Photochem
PubDate: 2022-01-12
DOI: 10.3390/photochem2010006
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 77-87: Effect of Photolysis on Zirconium Amino
Phenoxides for the Hydrophosphination of Alkenes: Improving Catalysis
Authors: Bryan T. Novas, Jacob A. Morris, Matthew D. Liptak, Rory Waterman
First page: 77
Abstract: A comparative study of amino phenoxide zirconium catalysts in the hydrophosphination of alkenes with diphenylphosphine reveals enhanced activity upon irradiation during catalysis, with conversions up to 10-fold greater than reactions in ambient light. The origin of improved reactivity is hypothesized to result from substrate insertion upon an n→d charge transfer of a Zr–P bond in the excited state of putative phosphido (Zr–PR2) intermediates. TD-DFT analysis reveals the lowest lying excited state in the proposed active catalysts are dominated by a P 3p→Zr 4d MLCT, presumably leading to enhanced catalysis. This hypothesis follows from triamidoamine-supported zirconium catalysts but demonstrates the generality of photocatalytic hydrophosphination with d0 metals.
Citation: Photochem
PubDate: 2022-01-18
DOI: 10.3390/photochem2010007
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 88-101: UV Photolysis Study of Para-Aminobenzoic
Acid Using Parahydrogen Matrix Isolated Spectroscopy
Authors: Alexandra McKinnon, Brendan Moore, Pavle Djuricanin, Takamasa Momose
First page: 88
Abstract: Many sunscreen chemical agents are designed to absorb UVB radiation (and in some cases UVA) to protect the skin from sunlight, but UV absorption is often accompanied by photodissociation of the chemical agent, which may reduce its UV absorption capacity. Therefore, it is important to understand the photochemical processes of sunscreen agents. In this study, the photolysis of para-aminobenzoic acid (PABA), one of the original sunscreen chemical agents, at three different UV ranges (UVA: 355 nm, UVB: >280 nm, and UVC: 266 nm and 213 nm) was investigated using parahydrogen (pH2) matrix isolation Fourier-Transform Infrared (FTIR) Spectroscopy. PABA was found to be stable under UVA (355 nm) irradiation, while it dissociated into 4-aminylbenzoic acid (the PABA radical) through the loss of an amino hydrogen atom under UVB (>280 nm) and UVC (266 nm and 213 nm) irradiation. The radical production supports a proposed mechanism of carcinogenic PABA-thymine adduct formation. The infrared spectrum of the PABA radical was analyzed by referring to quantum chemical calculations, and two conformers were found in solid pH2. The PABA radicals were stable in solid pH2 for hours after irradiation. The trans-hydrocarboxyl (HOCO) radical was also observed as a minor secondary photoproduct of PABA following 213 nm irradiation. This work shows that pH2 matrix isolation spectroscopy is effective for photochemical studies of sunscreen agents.
Citation: Photochem
PubDate: 2022-01-26
DOI: 10.3390/photochem2010008
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 102-121: Local and Remote Conformational
Switching in 2-Fluoro-4-Hydroxy Benzoic Acid
Authors: Sándor Góbi, Mirjam Balbisi, György Tarczay
First page: 102
Abstract: In this work, 2-F-4-OH benzoic acid was isolated in Ar matrices and conformational changes were induced by near-IR irradiating the sample. Upon deposition, three conformers could be observed in the matrix, denoted as A1, A2, and D1, respectively. A1 and A2 are trans carboxylic acids, i.e., there is an intramolecular H bond between the H and the carbonyl O atoms in the COOH group, whereas D1 is a cis carboxylic acid with an intramolecular H bond between the F atom and the H atom in the COOH group, which otherwise has the same structure as A1. The difference between A1 and A2 is in the orientation of the carbonyl O atom with regard to the F atom, i.e., whether they are on the opposite or on the same side of the molecule, respectively. All three conformers have their H atom in their 4-OH group, facing the opposite direction with regard to the F atom. The stretching overtones of the 4-OH and the carboxylic OH groups were selectively excited in the case of each conformer. Unlike A2, which did not show any response to irradiation, A1 could be converted to the higher energy form D1. The D1 conformer spontaneously converts back to A1 via tunneling; however, the conversion rate could be significantly increased by selectively exciting the OH vibrational overtones of D1. Quantum efficiencies have been determined for the ‘local’ or ‘remote’ excitations, i.e., when the carboxylic OH or the 4-OH group is excited in order to induce the rotamerization of the carboxylic OH group. Both ‘local’ and ‘remote’ conformational switching are induced by the same type of vibration, which allows for a direct comparison of how much energy is lost by energy dissipation during the two processes. The experimental findings indicate that the ‘local’ excitation is only marginally more efficient than the ‘remote’ one.
Citation: Photochem
PubDate: 2022-01-28
DOI: 10.3390/photochem2010009
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 122-137: Photoreactions of Sc3N@C80 with
Disilirane, Silirane, and Digermirane: A Photochemical Method to Separate
Ih and D5h Isomers
Authors: Masahiro Kako, Kyosuke Miyabe, Shinpei Fukazawa, Shinji Kanzawa, Masanori Yasui, Michio Yamada, Yutaka Maeda, Zdeněk Slanina, Filip Uhlík, Ludwik Adamowicz, Ilias Papadopoulos, Dirk M. Guldi, Makoto Furukawa, Shigeru Nagase, Takeshi Akasaka
First page: 122
Abstract: Under photoirradiation, Sc3N@Ih-C80 reacted readily with disilirane 1, silirane 4, and digermirane 7 to afford the corresponding 1:1 adducts, whereas Sc3N@D5h-C80 was recovered without producing those adducts. Based on these results, we described a novel method for the exclusive separation of Ih and D5h isomers of Sc3N@C80. The method includes three procedures: selective derivatization of Sc3N@Ih-C80 using 1, 4, and 7, facile HPLC separation of pristine Sc3N@D5h-C80 and Sc3N@Ih-C80 derivatives, and thermolysis of Sc3N@Ih-C80 derivatives to collect pristine Sc3N@Ih-C80. In addition, laser flash photolysis experiments were conducted to elucidate the reaction mechanism. Decay of the transient absorption of 3Sc3N@Ih-C80* was observed to be enhanced in the presence of 1, indicating the quenching process. When Sc3N@D5h-C80 was used, the transient absorption was much less intensive. Therefore, the quenching of 3Sc3N@D5h-C80* by 1 could not be confirmed. Furthermore, we applied time-dependent density functional theory (TD-DFT) calculations of the photoexcited states of Sc3N@C80 to obtain insights into the reaction mechanism.
Citation: Photochem
PubDate: 2022-02-07
DOI: 10.3390/photochem2010010
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 138-149: Enhanced Photocatalytic Activity of TiO2
Thin Film Deposited by Reactive RF Sputtering under Oxygen-Rich Conditions
Authors: Takaya Ogawa, Yuekai Zhao, Hideyuki Okumura, Keiichi N. Ishihara
First page: 138
Abstract: TiO2 thin films are promising as photocatalysts to decompose organic compounds. In this study, TiO2 thin films were deposited by reactive radio-frequency (RF) magnetron sputtering under various flow rates of oxygen and argon gas. The results show that the photocatalytic activity decreases as the oxygen-gas ratio is increased to 30% or less, while the activity increases under oxygen-rich conditions. It was observed that the crystal structure changed from anatase to a composite of anatase and rutile, where the oxygen-gas ratio during RF sputtering is more than 40%. Interestingly, the oxygen vacancy concentration increased under oxygen-rich conditions, where the oxygen-gas ratio is more than 40%. The sample prepared under the most enriched oxygen condition, 70%, among our experiments exhibited the highest concentration of oxygen vacancy and the highest photocatalytic activity. Both the oxygen vacancies and the composite of anatase and rutile structure in the TiO2 films deposited under oxygen-rich conditions are considered responsible for the enhanced photocatalysis.
Citation: Photochem
PubDate: 2022-02-18
DOI: 10.3390/photochem2010011
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 150-164: Observation of Light-Induced Reactions
of Olefin–Ozone Complexes in Cryogenic Matrices Using
Fourier-Transform Infrared Spectroscopy
Authors: Fumiyuki Ito
First page: 150
Abstract: Each olefin (ethylene, trans-1,3-butadiene, isoprene, dimethyl butadiene (DMB)) and ozone molecules were codeposited on a CsI window at cryogenic temperature, and the products of photolysis with ultraviolet–visible light were observed using Fourier-transform infrared spectroscopy. The products of the C2H4–O3 system could be assigned to glyoxal (CHO–CHO), ethylene oxide (c–C2H4O), CO, and CO2. The formation of CHO–CHO and c–C2H4 and the absence of H2CO and HCOOH indicated that the main reaction channels did not involve C–C bond breaking. Based on this simple scheme, the photoproducts of different olefin–O3 systems were assigned, and the vibrational features predicted by density functional theory calculations were compared with the observed spectra. Regarding butadiene, spectral matches between the observations and calculations seemed reasonable, while assignments for isoprene ambiguities of and DMB remain, mainly because of the limited availability of authentic sample spectra.
Citation: Photochem
PubDate: 2022-02-24
DOI: 10.3390/photochem2010012
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 165-180: Comparison of the Photodynamic Effect of
Two Chlorins, Photodithazine and Fotoenticine, in Gliosarcoma Cells
Authors: Letícia Corrêa Fontana, Juliana Guerra Pinto, Jéssica Aparecida Magalhães, Dayane Batista Tada, Rainara Moreno Sanches de Almeida, Cristina Pacheco-Soares, Juliana Ferreira-Strixino
First page: 165
Abstract: The treatment and prognosis of cancers of the nervous system remain unfavorable to the patient, which makes it necessary to study alternative therapies as primary or adjuvant treatments to existing methods. Photodynamic Therapy (PDT) is a method that consists of combining a photosensitizer (PS), a light source at the appropriate wavelength, and molecular oxygen, forming reactive oxygen species (ROS), leading to death in the target cell. The objective of this work was to compare the effects of PDT with two chlorins, Photodithazine (PDZ) and Fotoenticine (FTC), in 9L/lacZ gliosarcoma cell lines. Both chlorins, together with an LED device at 660 nm with a fluence of 10 J/cm², were included in the study. It was observed that the response to therapy depends on the concentration and type of PS used. In addition, PDZ showed a higher quantum yield of singlet oxygen generation than FTC.
Citation: Photochem
PubDate: 2022-02-25
DOI: 10.3390/photochem2010013
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 181-201: Phosphorescence of Hydrogen-Capped
Linear Polyyne Molecules C8H2, C10H2 and C12H2 in Solid Hexane Matrices at
20 K
Authors: Tomonari Wakabayashi, Urszula Szczepaniak, Kaito Tanaka, Satomi Saito, Keisuke Fukumoto, Riku Ohnishi, Kazunori Ozaki, Taro Yamamoto, Hal Suzuki, Jean-Claude Guillemin, Haruo Shiromaru, Takeshi Kodama, Miho Hatanaka
First page: 181
Abstract: Laser-ablated polyyne molecules, H(C≡C)nH, were separated by size in solutions and co-condensed with excess hexane molecules at a cryogenic temperature of 20 K in a vacuum system. The solid matrix samples containing C8H2, C10H2, and C12H2 molecules were irradiated with UV laser pulses and the phosphorescence 0–0 band was observed at 532, 605, and 659 nm, respectively. Vibrational progression was observed for the symmetric stretching mode of the carbon chain in the ground state with increments of ~2190 cm−1 for C8H2, ~2120 cm−1 for C10H2, and ~2090 cm−1 for C12H2. Temporal decay analysis of the phosphorescence intensity revealed the lifetimes of the triplet state as ~30 ms for C8H2, ~8 ms for C10H2, and ~4 ms for C12H2. The phosphorescence excitation spectrum reproduces UV absorption spectra in the hexane solution and in the gas phase at ambient temperature, although the excitation energy was redshifted. The symmetry-forbidden vibronic transitions were observed for C10H2 by lower excitation energies of 25,500–31,000 cm−1 (320–390 nm). Detailed phosphorescence excitation patterns are discussed along the interaction of the polyyne molecule and solvent molecules of hexane.
Citation: Photochem
PubDate: 2022-02-28
DOI: 10.3390/photochem2010014
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 202-216: Theoretical Modeling of Absorption and
Fluorescent Characteristics of Cyanine Dyes
Authors: Sonia Ilieva, Meglena Kandinska, Aleksey Vasilev, Diana Cheshmedzhieva
First page: 202
Abstract: The rational design of cyanine dyes for the fine-tuning of their photophysical properties undoubtedly requires theoretical considerations for understanding and predicting their absorption and fluorescence characteristics. The present study aims to assess the applicability and accuracy of several DFT functionals for calculating the absorption and fluorescence maxima of monomethine cyanine dyes. Ten DFT functionals and different basis sets were examined to select the proper theoretical model for calculating the electronic transitions of eight representative molecules from this class of compounds. The self-aggregation of the dyes was also considered. The pure exchange functionals (M06L, HFS, HFB, B97D) combined with the triple-zeta basis set 6-311+G(2d,p) showed the best performance during the theoretical estimation of the absorption and fluorescent characteristics of cyanine dyes.
Citation: Photochem
PubDate: 2022-03-04
DOI: 10.3390/photochem2010015
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 217-224: Phosphorescence and Photophysical
Parameters of Porphycene in Cryogenic Matrices
Authors: Barbara Golec, Aleksander Gorski, Jacek Waluk
First page: 217
Abstract: Matrix isolation studies were carried out for porphycene, an isomer of porphyrin, embedded in solid nitrogen and xenon. The external heavy atom effect resulted in nearly a 100% population of the triplet state and in the appearance of phosphorescence, with the origin located at 10163 cm−1. This energy is much lower than that corresponding to the T1 position in porphyrin. This difference could be explained by postulating that the orbital origin corresponds in both isomers to the second excited singlet state, which lies much closer to S1 in porphycene. Most of the vibrational frequencies observed in the phosphorescence spectrum correspond to totally symmetric modes, but several ones were assigned to the out-of-plane Bg vibrations. These bands are not observed in fluorescence, which suggests their possible role in vibronic-spin-orbit coupling.
Citation: Photochem
PubDate: 2022-03-09
DOI: 10.3390/photochem2010016
Issue No: Vol. 2, No. 1 (2022)
- Photochem, Vol. 2, Pages 225-236: Study of the Response Surface in the
Photocatalytic Degradation of Acetaminophen Using TiO2
Authors: Adriana Marizcal-Barba, Jorge Alberto Sanchez-Burgos, Victor Zamora-Gasga, Alejandro Perez Larios
First page: 225
Abstract: An effective way to obtain the optimal parameters of a process or experiment is the response surface method. Using the Box–Behnken design further decreases the number of experiments needed to obtain sufficient data to obtain a reliable equation. From the equation, it is possible to predict the behavior of the response with respect to the combination of variables involved. In this study we evaluated the photocatalytic activity of the synthesized TiO2 for the degradation of acetaminophen, a frequently used and uncontrolled drug that has been detected with increasing frequency in wastewater effluents. The variables used for this study were pH, contaminant concentration (acetaminophen) and catalyst dose. We found, with a 95% confidence level, that 99% of the contaminant can be degraded to pH 10, contaminant to 35 mg/L and a catalyst dose of 0.15 g TiO2.
Citation: Photochem
PubDate: 2022-03-10
DOI: 10.3390/photochem2010017
Issue No: Vol. 2, No. 1 (2022)
