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 Functional Materials Letters   [SJR: 0.528]   [H-I: 14]   [1 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1793-6047 - ISSN (Online) 1793-7213    Published by World Scientific  [120 journals]
• High vibration damping in in situIn–Zn composites
• Authors: Samuel P. Balch, Roderic S. Lakes
Abstract: Functional Materials Letters, Ahead of Print.
Indium–zinc in situ composites were fabricated and their viscoelastic properties studied over 8.5 decades of frequency. Material with 5% indium by weight was found to have a stiffness damping product (the figure of merit for damping layers) of 1.9 GPa at 10 Hz; 3 times better than the peak of polymer damping layers and over a wider frequency range. Material with 15% indium had a stiffness damping product of 1.8 GPa. The indium segregated in a platelet morphology, particularly favorable for attaining high damping from a small concentration, as predicted by viscoelastic composite theory.
Citation: Functional Materials Letters
PubDate: Fri, 17 Apr 2015 02:48:46 GMT
DOI: 10.1142/S1793604715500599

• Cellulose acetate–lithium bis(trifluoromethanesulfonyl)imide solid
polymer electrolyte: ATR-FTIR and ionic conductivity behavior
• Authors: Siti Masyitah Mohd Razalli, Siti Irma Yuana Sheikh Mohd Saaid, Ab Malik Marwan Ali, Oskar Hasdinor Hassan, Muhd Zu Azhan Yahya
Abstract: Functional Materials Letters, Ahead of Print.
Solid polymer electrolytes (SPEs) based on cellulose acetate (CA) doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt are prepared by solution cast technique. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy of the polymer salt complexes are recorded in the frequency range between 400 cm-1 and 4000 cm-1. The shifting of carbonyl band (C=O) at 1737 cm-1 to a lower wavenumber confirms the occurrence of complexation between the polymer and the salt. The electrochemical impedance spectroscopy (EIS) analysis discovered that the film with 25 wt.% of salt shows the highest ionic conductivity at room temperature. The change in real dielectric permittivity (εr) as a function of frequency at different salt concentrations which exhibits a dispersive behavior at low frequencies and decays at higher frequencies, shows the electrode polarization and space charge effect. The real modulus formalism (Mr) analysis shows that the polymer electrolytes in this work are ionic conductors.
Citation: Functional Materials Letters
PubDate: Tue, 31 Mar 2015 06:47:34 GMT
DOI: 10.1142/S1793604715400172

• Abnormal capacitance–voltage and switchable photovoltaic effect of
epitaxial Mn-doped BiFeO3 thin film capacitor
• Authors: Zeng-Wei Peng, Bao-Ting Liu
Abstract: Functional Materials Letters, Ahead of Print.
Epitaxial BiFe0.95Mn0.05O3 (BFMO) film was deposited on (001)-oriented SrRuO3 (SRO) coated SrTiO3 (STO) substrate by radio-frequency (rf) magnetron sputtering. Indium tin oxide (ITO) was grown on BFMO/STO heterojunction to fabricate ITO/BFMO/SRO capacitor for investigating the ferroelectric and photovoltaic properties. The ITO/BFMO/SRO capacitor exhibits large remanent polarizations of 92.2 μC/cm2, 101 μC/cm2 and 109 μC/cm2 measured at 20 V, 25 V and 30 V, respectively. An observed abnormal capacitance–voltage (C–V) curve can be explained based on the ITO/BFMO interface. The calculated capacitance and junction width of ITO/BFMO interface are 105 pF and 32 nm, respectively. Additionally, it is found that photovoltaic effect of the ITO/BFMO/SRO capacitor is mainly attributed to ferroelectric polarization and internal electric field induced by defects. The photocurrent densities coming from ferroelectric polarization and internal field are 36 μA/cm2 and 23 μA/cm2, respectively. The photovoltaic output from the ferroelectric polarization is obviously larger than that from the internal electric field.
Citation: Functional Materials Letters
PubDate: Tue, 31 Mar 2015 06:47:34 GMT
DOI: 10.1142/S1793604715500575

• Synthesis and magnetic property of SiO2 coated Fe3O4/palygorskite
• Authors: Xi He, Qian Yang, Liangjie Fu, Huaming Yang
Abstract: Functional Materials Letters, Ahead of Print.
SiO2 coated Fe3O4/palygorskite magnetic nanocomposites (MNCs) were successfully synthesized via coprecipitation route. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscopy (TEM) and magnetic properties. The resulsts indicated that SiO2 was coated on the surface of Fe3O4/palygorskite through the hydrolysis of tetraethyl orthosilicate (TEOS) and the orientation changing of MNCs could be realized by external magnetic field. The interfaces of the composite were further elucidated at atomic level. We believe that the as-prepared SiO2 coated Fe3O4/palygorskite MNCs could show potential application in the fields of functional nanomaterials.
Citation: Functional Materials Letters
PubDate: Tue, 31 Mar 2015 06:47:33 GMT
DOI: 10.1142/S1793604715500563

• Interplay between magnetism and Na concentration in NaxCoO2
• Authors: M. H. N. Assadi, H. Katayama-Yoshida
Abstract: Functional Materials Letters, Ahead of Print.
Through comprehensive density functional calculations, the crystallographic, magnetic and electronic properties of NaxCoO2 (x = 1, 0.875, 0.75, 0.625 and 0.50) were investigated. We found that all Na ions in NaCoO2 and Na0.875CoO2 share the basal coordinates with O ions. However, as x decreases, some of Na ions move within the basal plane in order to reduce the in-plane Na-Na electrostatic repulsion. Magnetically, there was strong tendency for type A antiferromagnetism in the Na0.75CoO2 system, while all other Na deficient systems had a weaker ferromagnetic (FM) tendency. The results on magnetism were in excellent agreement with the experiments.
Citation: Functional Materials Letters
PubDate: Tue, 31 Mar 2015 06:47:33 GMT
DOI: 10.1142/S1793604715400160

• Investigation of electrical transport properties of Bi0.5Sb1.5Te2.7Se0.3
alloys prepared by high-pressure method
• Authors: Xin Guo, Xiaopeng Jia, Yuewen Zhang, Hairui Sun, Bing Sun, Hongan Ma
Abstract: Functional Materials Letters, Ahead of Print.
The quaternary Bi0.5Sb1.5Te2.7Se0.3 alloys have been successfully synthesized within 25 min by high-pressure method. The pressure-dependent electrical transport properties of the as-prepared Bi0.5Sb1.5Te2.7Se0.3 alloys are carefully investigated at room temperature. The measurement results indicate that the electrical resistivity and the Seebeck coefficient reveal a strong correlation with the increase of synthesis pressure. The carrier concentration and mobility are modulated effectively due to the effects of synthesis pressure and composition, leading to an improvement in the power factor of Bi0.5Sb1.5Te2.7Se0.3. These results suggest that the utilization of pressure during the synthesis process provides an effective and controllable strategy to optimize the electrical transport properties of the (Bi,Sb)2(Te,Se)3 alloys.
Citation: Functional Materials Letters
PubDate: Thu, 19 Mar 2015 03:06:29 GMT
DOI: 10.1142/S1793604715500551

• Ultra large deflection of thin PZT/aluminium cantilever beam
• Authors: Raynald Seveno, Benoit Guiffard, Jean-Pierre Regoin
Abstract: Functional Materials Letters, Ahead of Print.
Flexible piezoelectric cantilever beam has been realized by depositing lead zirconate titanate (PZT) thin film (4.5 μm) by chemical solution deposition (CSD) onto very thin aluminium foil (16 μm). The tip deflection of the beam has been measured as a function of the frequency of the applied sinusoidal voltage to the PZT film for different amplitudes. Resonance curves have been compared to a classical model of an oscillating system under sinusoidal stress with a very good agreement. Despite of weak ferroelectric properties (remnant polarization: 13 μC/cm2), ultra-large deflection amplitudes have been measured under very moderate applied voltage values: 750 μm@10 V for quasi-static mode and 5 mm@10 V at the resonance frequency (∼12 Hz), which makes this PZT/aluminium composite film very promising for highly flexible actuation applications where large displacements are wanted.
Citation: Functional Materials Letters
PubDate: Wed, 11 Mar 2015 02:01:31 GMT
DOI: 10.1142/S1793604715500514

• Direct observation of magnetic exchange-spring development in epitaxial
DyFe2/YFe2 superlattices by magneto-optical Kerr effect
• Authors: Ke Wang, Yang Xiang, Chuanwen Chen, Fengjiang Zhuang, Xuefeng Wu, Roger Ward
Abstract: Functional Materials Letters, Ahead of Print.
The magnetic reversal properties of molecular beam epitaxy (MBE) grown Laves phase single crystal YFe2-dominated DyFe2/YFe2 superlattices were investigated using magneto-optical Kerr effect (MOKE) measurements. Single crystal DyFe2/YFe2 superlattices with a thickness ratio of 1:4 were MBE-grown with a (110) growth direction. In the epitaxial superlattices, the development of exchange-spring structure during magnetic reversal is revealed by both magneto-optical reflectivity and Kerr rotation angle loops. The bending fields of the samples are found to be close due to nonideal anisotropy in both hard and soft layers. For the sample with thin soft/hard layers, large magneto-optical reflectivity change up to 0.25% was observed. This can be related with rotation of Fe spins in YFe2 soft layers under a low pinning field, in consistence with the small switching field of thin DyFe2 hard layers measured experimentally.
Citation: Functional Materials Letters
PubDate: Wed, 11 Mar 2015 02:01:31 GMT
DOI: 10.1142/S1793604715500538

• Silicon quantum dots embedded in amorphous SiC matrix for third-generation
solar cells: Microstructure control by RF discharge power
• Authors: Qijin Cheng, Igor Levchenko, Denyuan Song, Shuyan Xu, Kostya (Ken) Ostrikov
Abstract: Functional Materials Letters, Ahead of Print.
A low-frequency (460 kHz), low-pressure, thermally non-equilibrium, high-density inductively coupled plasma (ICP) has been used to synthesize a novel, advanced photovoltaic material suitable for fabrication of third-generation solar cells. Silicon quantum dots (SQDs) embedded in an amorphous silicon carbide matrix were prepared at a very low substrate temperature of approximately 200°C without any hydrogen dilution. The effect of the radio-frequency (RF) power of the plasma discharge on the morphology and structure of the embedded quantum dots was studied. A brief discussion on the possible mechanisms of the quantum dot formation in the ICP is presented. This study is relevant to third-generation photovoltaic solar cells.
Citation: Functional Materials Letters
PubDate: Wed, 11 Mar 2015 02:01:30 GMT
DOI: 10.1142/S179360471550054X

• Fabrication and characterization of environmental-friendly Ni1-xRxTiO3
nanopigments with high NIR reflectance
• Authors: Yu-Ping Tong, Zheng Chen, Hui-Xian Wang, Xu-Fang Zhang, Jun-Tao Ma, Xi Chen
Abstract: Functional Materials Letters, Ahead of Print.
A series of novel high dispersed environmental-friendly nanopigments based on NiTiO3 doped with rare earth ion such as Y, La, Eu, Sm have been developed. The products were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), commission internationale de l'Eclairage (CIE) 1976 L* a* b* color scales and UV-Vis-near-infrared radiation (NIR) reflectance spectroscopy. The substitution of R3+ for Ni2+ in NiTiO3 can improve the yellowness of pigments, especially for Eu3+ substitution. The sample with the substitution of Eu3+ for Ni2+ processes the highest NIR reflectance and enhances the NIR reflectance to 89.0%. SEM results revealed that the obtained pigments were composed of well-dispersed spherical-like particles with the range of 40–60 nm. EDS results indicated that the distribution of Ni, Ti, R, O element was considerably uniform with no chemical segregation phenomenon.
Citation: Functional Materials Letters
PubDate: Wed, 11 Mar 2015 02:01:30 GMT
DOI: 10.1142/S1793604715500502

• Photovoltaic properties of silicon nanocrystals in silicon nitride
prepared by ammonia sputtering
• Authors: Xiaobo Chen
Abstract: Functional Materials Letters, Ahead of Print.
In this work, we present an investigation of the photovoltaic properties of low-temperature (700°C annealing temperature) prepared P-doped Silicon nanocrystals (SiNCs) in silicon nitride by ammonia sputtering followed by rapid thermal annealing (RTA). We examined how the flow rate of NH3 influenced the structural properties of the annealed films by using Raman scattering, grazing incidence X-ray diffraction (GI XRD) and transmission electron microscopy (TEM), it was found that the appropriate flow rate of NH3 is 3 sccm. For the sample deposited at the flow rate of 3 sccm, TEM image showed that SiNCs were formed with a mean size about 3.7 nm and the density of ~ 2.1 × 1012 cm-2; X-ray photoelectron spectroscopy (XPS) characterization showed the existence of Si–P bonds, indicating effective P doping; the average absorptance of higher than 65% and a significant amount of photocurrent makes it suitable for photoactive. Moreover, the experimental P-doped SiNCs:Si3N4/p-Si heterojunction solar cell has been fabricated, and the device performance was studied. The photovoltaic device fabricated exhibits an open-circuit voltage (VOC) and a short-circuit current density (JSC) of 470 mV and 3.25 mA/cm2, respectively.
Citation: Functional Materials Letters
PubDate: Wed, 11 Mar 2015 02:01:29 GMT
DOI: 10.1142/S1793604715500526

• Effect of the matrix subsystem on hydrostatic parameters of a novel
1–3-type piezo-composite
• Authors: Vitaly Yu. Topolov, Christopher R. Bowen, Paolo Bisegna, Anatoly E. Panich
Abstract: Functional Materials Letters, Ahead of Print.
The influence of the aspect ratio and volume fraction of ferroelectric ceramic inclusions in a 0–3 matrix on the hydrostatic parameters of a three-component 1–3-type composite is studied to demonstrate the important role of the elastic properties of the two-component matrix on the composite performance. Differences in the elastic properties of the 0–3 matrix and single-crystal rods lead to a considerable dependence of the hydrostatic response of the composite on the anisotropy of the matrix elastic properties. The performance of a 1–0–3 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3 SC/modified PbTiO3 ceramic/polyurethane composite suggests that this composite system is of interest for hydroacoustic applications due to its high hydrostatic piezoelectric coefficients $d_{h}^{*} \approx (400-500)\,{\rm pC/N}$ and $g_{h}^{*} \sim 0.1\,{\rm V}\cdot {\rm m/N}$, squared figure of merit d_{h}^{*}g_{h}^{*} \approx (30-40)\cdot 10^{-12}\,{\rm Pa}^{-1}$, and electromechanical coupling factor$k_{h}^{*} \approx 0.5-0.6\$.
Citation: Functional Materials Letters
PubDate: Thu, 26 Feb 2015 02:50:22 GMT
DOI: 10.1142/S1793604715500496

• Interface characterization of Cu–Mo coating deposited on Ti–Al
alloys by arc spraying
• Authors: Shengqiang Bai, Fei Li, Ting Wu, Xianglin Yin, Xun Shi, Lidong Chen
Abstract: Functional Materials Letters, Ahead of Print.
Cu–Mo pseudobinary alloys are promising candidates as electrode materials in CoSb3-based skutterudite thermoelectric (TE) devices for TE power generation. In this study, Cu–Mo coatings were deposited onto Ti–Al substrates by applying a dual-wire electric arc spraying coating technique. The microstructure of the surfaces, cross sections and coating interfaces were analyzed by scanning electron microscopy (SEM) and energy dispersion spectrometry (EDS). Cu–Mo coatings showed a typical banded splat with compact microstructures, and have no coarse pores nor micro-cracks. The thermal shock resistance of the Cu–Mo coating was also investigated to show good combinations with Ti–Al substrates. After 50 thermal shock cycles, there were no cracks observed at the interface. In contrast, the test of the thermal shock resistance of the Cu coating on the Ti–Al substrate was also investigated. Due to a large difference in the thermal expansion coefficients between Cu and Ti–Al alloys, the Cu coating flaked from the Ti–Al substrate completely after 10 thermal shock cycles. The contact resistivity of the Ti–Al/Cu–Mo interface was about 1.6 μΩ⋅cm2 and this value was unchanged after 50 thermal shock cycles, indicating the low electric resistance and high thermal stability of the Cu–Mo/Ti–Al interface.
Citation: Functional Materials Letters
PubDate: Thu, 26 Feb 2015 02:50:22 GMT
DOI: 10.1142/S1793604715500484

• Room temperature reduction and hydrolysis of FeCl3⋅6H2O on
self-sacrifice microscale Cu2O octahedron template: A mild chemical
synthesis of pseudocapacitor electrode materials
• Authors: Mu Zhang, Xiaoyang Peng, Xu Chen, Kunfeng Chen, Xudong Sun, Dongfeng Xue
Abstract: Functional Materials Letters, Ahead of Print.
Fe(OH)x(x = 2, 3) colloidal aggregations were synthesized at room temperature via a reduction and hydrolysis of FeCl3⋅6H2O on microscale Cu2O octahedron, which functions as a self-sacrifice template. We herein proposed the growth of Fe(OH)x colloidal aggregation by redox etching Cu2O octahedron while two critical reactions of both redox and precipitation were well employed in this work. As-synthesized Fe(OH)x samples exhibited high specific capacitance of 242.7 F/g, which was higher than those available data of iron oxides and hydroxides.
Citation: Functional Materials Letters
PubDate: Wed, 18 Feb 2015 02:17:04 GMT
DOI: 10.1142/S1793604715500472

• Synthesis and luminescence properties of novel deep red emitting phosphors
Li2MgGeO4:Mn4+
• Authors: Renping Cao, Dong Ceng, Xiaoguang Yu, Siling Guo, Yufeng Wen, Guotai Zheng
Abstract: Functional Materials Letters, Ahead of Print.
Novel deep red phosphor Li2MgGeO4:Mn4+ is synthesized by high temperature solid state reaction method in air. The strongest PL band peaking at ∼ 671 nm in the range of 600–750 nm is due to the 2E → 4A2 transition of Mn4+ ion and the PLE spectra shows broad band peaking at ∼ 323 within the range 220–550 nm owing to the 4A2 → 4T1 transitions of Mn4+ ion. The optimum Mn4+ doping concentration is about 0.4 mol.%. The luminous mechanism is explained by Tanabe–Sugano diagram of Mn4+ ion. The results indicate that red phosphor Li2MgGeO4:Mn4+ is a beneficial phosphor for use in white light-emitting-diodes (LEDs).
Citation: Functional Materials Letters
PubDate: Wed, 11 Feb 2015 07:10:41 GMT
DOI: 10.1142/S1793604715500460

• The study of composition and surface electron structure of nitrogen-doped
DLC film prepared by PIII-D
• Authors: Hai Huang Li, Feng Wen, Changjiang Pan, Hongyan Ding, Nan Huang, Yongxiang Leng
Abstract: Functional Materials Letters, Ahead of Print.
Nitrogen-doped diamond-like carbon (N-DLC) films were synthesized by plasma immersion ion implantation and deposition (PIII-D) at room temperature (RT). During the process of deposition, N2 flow was changed from 0 to 10 sccm. Lifshitz–van der Waals/acid–base (LW-AB) approach was employed to study the surface electronic state of the films, X-ray photoelectron spectroscopic (XPS) and valence band spectra (VBS) were used to study chemical bonds and electron structure information inside the films. Bandgap of the films were calculated by the data from ultraviolet spectrophotometer. The results showed that synthesized films were n-type semiconductors and doping of nitrogen element will affect the accepted–electron capability of the film. The change tendency of the bandgap coincides with that of the ratio of acidic to alkaline component of the polar acid-alkali surface energy. There was much sp hybrid electronic state existed in the films, which mainly sp2C=C/C=N and sp3C–C/C–N bonds.
Citation: Functional Materials Letters
PubDate: Fri, 06 Feb 2015 01:36:37 GMT
DOI: 10.1142/S1793604715400159

• Design of poly(ether block amide)/polyacrylonitrile composite membrane for
carbon dioxide capture
• Authors: Lianjun Wang, Pengfei Ji, Yang Li, Mingming Di, Quan Lv, Shuguang Li
Abstract: Functional Materials Letters, Ahead of Print.
In this study, poly(ether block amide) was used as coating material to develop a novel composite polymer membrane for CO2 capture. Polyacrylonitrile (PAN) ultrafiltration membrane was applied as substrate. Between them, a gutter layer prepared from cross-linked polydimethylsiloxane (PDMS) blending with amino silicone was introduced to improve separation performance of the composite membrane. The separation properties of resultant triple layer composite membrane was characterized using pure CO2 and N2 gases. It was found that the crosslinking degree of the gutter layer had great influence on membrane performance, which could be significantly improved with the help of amino-PDMS gutter layer compared with that of the membrane having Pebax coating directly onto PAN substrate. Using 2 wt.% Pebax coating solution and properly cross-linked gutter layer, the designed Pebax/amino-PDMS/PAN composite membrane showed CO2 permeance of 147 GPU and CO2/N2 selectivity of 62.
Citation: Functional Materials Letters
PubDate: Fri, 06 Feb 2015 01:36:37 GMT
DOI: 10.1142/S1793604715500459

• Solid high-proton conductor tungstovanadozincic acid with transition metal
as central atom: Synthesis and conductivity
• Authors: Tianpei Huang, Xuefei Wu, Qingyin Wu, Fahe Cao, Wenfu Yan
Abstract: Functional Materials Letters, Ahead of Print.
A Keggin-type vanadium-substituted tungstovanadozincic heteropoly acid H7ZnW11VO40 ⋅ 8H2O, with the transition metal as central atom, was firstly synthesized and characterized. Its proton conductivity was measured by the electrochemical impedance spectrum (EIS), and the result indicates that the H7ZnW11VO40 ⋅ 8H2O is a solid high-proton conductor with conductivity of 3.26 × 10-3S ⋅ cm-1 at 58°C, 50% relative humidity. Its activation energy is 29.50 kJ ⋅ mol-1, which suggests that the mechanism of proton conduction is the Vehicle mechanism.
Citation: Functional Materials Letters
PubDate: Fri, 06 Feb 2015 01:36:36 GMT
DOI: 10.1142/S1793604715500411

• Facile preparation of size-controlled TiO2 nanoparticles by hot-filament
metal oxide deposition method and their gas sensing properties to NO2
• Authors: Xiaoguang San, Weiwei Xu, Guosheng Wang, Bing Liang, Nannan Hou, Fanli Meng
Abstract: Functional Materials Letters, Ahead of Print.
Titanium dioxide (TiO2) nanoparticles were prepared by resistive heating Ti filament under an oxygen atmosphere. The obtained nanoparticles were confirmed to be a tetragonal crystal TiO2 and the particle size increased with increasing the oxygen pressure. The NO2 gas sensing properties of the TiO2 nanoparticles were investigated. All the sensors made of TiO2 nanoparticles with different particle sizes exhibited the maximum sensitivities to 1 ppm NO2 at a relative low operating temperature of 150°C. Comparing with the large particle size of TiO2 nanoparticles, the ones with the smallest particle size exhibited the highest sensitivity and the best response and recovery characteristic to various NO2 gas concentrations.
Citation: Functional Materials Letters
PubDate: Fri, 06 Feb 2015 01:36:36 GMT
DOI: 10.1142/S1793604715500435

polyacrylamide/calcium alginate/TiO2 composite film
• Authors: Shuxin Wei, Kongyin Zhao, Xinxin Zhang, Yifan Fu, Zhihui Li, Sai Xu, Junfu Wei
Abstract: Functional Materials Letters, Ahead of Print.
Citation: Functional Materials Letters
PubDate: Fri, 06 Feb 2015 01:36:35 GMT
DOI: 10.1142/S1793604715400147

• A novel high color purity yellow luminescent material NaBaBO3:Sm3+
• Authors: Jianghui Zheng, Jia Feng, Qijin Cheng, Ziquan Guo, Lihan Cai, Chao Chen
Abstract: Functional Materials Letters, Ahead of Print.
Yellow emitting Sm3+-doped NaBa1-xBO3(0.01 ≤ x ≤ 0.13) phosphors were synthesized by conventional solid state reaction method. The phase structure and luminescence properties of the as-prepared phosphors were investigated. These phosphors can be effectively excited by 403 nm near-ultraviolet light and feature a satisfactory yellow performance. The emission peaks are observed at 560 nm, 603 nm and 650 nm, originating from the transitions of 4G5/2 → 6H5/2, 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 respectively. Investigation of Sm3+ concentration-dependent emission spectra indicates that the NaBa0.95BO3:0.05Sm3+ phosphor shows the strongest yellow emission intensity and exhibits the CIE value of x = 0.4760 and y = 0.5090. Through the theoretical calculation, a high color purity of 96.0% was determined for the NaBaBO3:Sm3+ phosphor, and the color purity of NaBaBO3:Sm3+ is much higher than that of the commercial yellow phosphor YAG:Ce3+. This work is highly relevant to the development of a new type of potential down-conversion (DC) yellow phosphor for near ultraviolet white or yellow light-emitting diodes (LEDs).
Citation: Functional Materials Letters
PubDate: Fri, 06 Feb 2015 01:36:35 GMT
DOI: 10.1142/S1793604715500423

• Ferritin-mediated biomimetic synthesis of bimetallic Au–Ag
nanoparticles on graphene nanosheets for electrochemical detection of
hydrogen peroxide
• Authors: Li Wang, Jiku Wang, Pengjuan Ni, Zhuang Li
Abstract: Functional Materials Letters, Ahead of Print.
We demonstrated a biomimetic green synthesis of bimetallic Au–Ag nanoparticles (NPs) on graphene nanosheets (GNs). The spherical protein, ferritin (Fr), was bound onto GNs and served as the template for the synthesis of GN/Au–Ag nanohybrids. The created GN/Au–Ag nanohybrids were further utilized to fabricate a non-enzymatic amperometric biosensor for the sensitive detection of hydrogen peroxide (H2O2), and this biosensor displayed high performances to determine H2O2 with a detection limit of 2.0 × 10-6 M and a linear detection range from 2.0 μM to 7.0 mM.
Citation: Functional Materials Letters
PubDate: Fri, 06 Feb 2015 01:36:35 GMT
DOI: 10.1142/S1793604715500447

• Fabrication and photocatalytic performance of electrospun PVA/silk/TiO2
nanocomposite textile
• Authors: Ming-Chung Wu, Shun-Hsiang Chan, Ting-Han Lin
Abstract: Functional Materials Letters, Ahead of Print.
Many organic/inorganic nanocomposites have been fabricated into fibrous materials using electrospinning techniques, because electrospinning processes have many attractive advantages and the ability to produce relatively large-scale continuous films. In this study, the polyvinyl alcohol (PVA)/silk/titanium dioxide (TiO2) nanocomposite self-cleaning textiles were successfully produced using electrospinning technique. After optimizing electrospinning conditions, we successfully obtained the PVA/silk/TiO2 nanocomposite fibers with average diameter of ∼220 nm and TiO2 concentration can be as high as 18.0 wt.%. For the case of the PVA/silk/TiO2 nanocomposite textile, the color of brilliant green coated on the textile surface changed from the initial green color to colorless after ultraviolet (UV) irradiation. Because of its worthy photocatalytic performance, the developed PVA/silk/TiO2 nanocomposite materials in this study will be beneficial for the design and fabrication of multifunctional fibers and textiles.
Citation: Functional Materials Letters
PubDate: Thu, 15 Jan 2015 03:39:28 GMT
DOI: 10.1142/S1793604715400135

• Influence of Sm3+ doping on microstructure and electrical properties of
((Nd0.7Yb0.3)1-xSmx)2Zr2O7
• Authors: Jia-Hu Ouyang, Cheng Zhu, Zhan-Guo Liu, Zhe Ren, Lin Jing
Abstract: Functional Materials Letters, Ahead of Print.
(Nd0.7Yb0.3)2Zr2O7 and ((Nd0.7Yb0.3)1-xSmx)2Zr2O7(0 < x ≤ 0.25) ceramics have been synthesized by pressureless sintering by tailoring the chemical compositions. Microstructure and electrical conductivity of ((Nd0.7Yb0.3)1-xSmx)2Zr2O7 were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and AC impedance spectroscopy. (Nd0.7Yb0.3)2Zr2O7 ceramic exhibits a mixed crystal structure of defect fluorite and pyrochlore. After doping with Sm3+ cations, the structure changes from a mixed type of (Nd0.7Yb0.3)2Zr2O7 to a single pyrochlore type of ((Nd0.7Yb0.3)1-xSmx)2Zr2O7, as the addition of Sm3+ reduces the difference in ionic radius between Nd3+ and Yb3+. However, ((Nd0.7Yb0.3)1-xSmx)2Zr2O7 ceramics contain the localized short-range disorder despite the structural order overall in the pyrochlore. The measured total conductivities of ((Nd0.7Yb0.3)1-xSmx)2Zr2O7 obey the Arrhenius relation. Doping of Sm3+ enhances the electrical conductivity of (Nd0.7Yb0.3)2Zr2O7 ceramic significantly, which is closely related to the variations in the concentration of oxygen vacancies at 48f sites, relatively low activation energy and high pre-exponential factor caused by the long-range order and short-range disorder.
Citation: Functional Materials Letters
PubDate: Thu, 15 Jan 2015 03:39:27 GMT
DOI: 10.1142/S1793604715400123

• Magnetic and dielectric properties of 3Y-TZP/strontium doped barium
ferrite composite
• Authors: Chao Zhang, Shan-Shan Wang, Rui-Song Guo, Guang-Lan Cai, Wei-Na Guo, Chen Wu
Abstract: Functional Materials Letters, Ahead of Print.
Magnetic and dielectric properties of 3Y-TZP/20 wt.% Ba1-xSrxFe12O19(x = 0, 0.25, 0.5, 0.75) composites prepared by solid state reaction method are investigated. The magnetic properties are improved in the composites with the strontium doped barium ferrite. When x = 0.25, the saturation magnetization of the ferrite reaches the maximum. This is due to the migration of Fe3+ induced by the Sr2+ doping. The dielectric properties are also improved in the composite with the strontium doped barium ferrite. When x = 0.5, the dielectric constant and dielectric loss possess the maximum. This is caused by the lattice distortion resulting from the Sr2+ doping. The dielectric properties are analyzed by the universal relaxation law.
Citation: Functional Materials Letters
PubDate: Wed, 14 Jan 2015 02:59:28 GMT
DOI: 10.1142/S179360471550040X

• Synthesis and physical properties of quasi-one-dimensional magnetic
material Ca3LiRuO6
• Authors: Dapeng Wu, Yang Qi
Abstract: Functional Materials Letters, Ahead of Print.
Ca3LiRuO6 single crystals were grown using the flux method, magnetic properties measurement results along different directions of needle-like single crystals are reported for the first time and show Ca3LiRuO6 occurs a paramagnetic (PM)-weak ferromagnetic (FM) transition at a temperature Tc = 120 K, also the magnetic moment aligns in the ab plane. Although Ca3LiRuO6 is characterized by one-dimensional configuration in crystallographic structure, it has three-dimensional (3D) magnetic order, the value of Tc is far below the magnitude of Curie–Weiss temperature. Θcw ≈ -306 K indicates complex nature of the magnetism is in this compound.
Citation: Functional Materials Letters
PubDate: Fri, 09 Jan 2015 08:22:45 GMT
DOI: 10.1142/S1793604715500393

• Energetic and thermal properties of tilt grain boundaries in
graphene/hexagonal boron nitride heterostructures
• Authors: Mingchao Wang, Guangping Zhang, Huisheng Peng, Cheng Yan
Abstract: Functional Materials Letters, Ahead of Print.
Graphene/hexagonal boron nitride (G/h-BN) heterostructure has attracted tremendous research efforts owing to its great potential for applications in nanoscale electronic devices. In such hybrid materials, tilt grain boundaries (GBs) between graphene and h-BN grains may have unique physical properties, which have not been well understood. Here we have conducted non-equilibrium molecular dynamics simulations to study the energetic and thermal properties of tilt GBs in G/h-BN heterostructures. The effect of misorientation angles of tilt GBs on both GB energy and interfacial thermal conductance are investigated.
Citation: Functional Materials Letters
PubDate: Mon, 29 Dec 2014 06:38:52 GMT
DOI: 10.1142/S1793604715500381

• Preparation of bionic lotus leaf surfaces using SiO2 nanoparticle-filled
polymer
• Authors: Jianfang Wang, Siwen Qian, Cheng-an Tao, Fang Wang, Sida Zhang, Chenchao Song
Abstract: Functional Materials Letters, Ahead of Print.
A bionic lotus leaf surface is prepared using a nanoparticle filling method that takes modified SiO2 nanoparticles as the filling and a polymer with low surface energy as the matrix. The effects of the mass ratio of SiO2 nanoparticles to the polymer with low surface energy (β) on the surface microstructure, infiltration, and mechanical properties of the bionic lotus leaf surface are discussed. Results show that it is feasible and easy to form a microstructured coating surface using nanoparticle filling. Nanosilica modified by KH570 has better compatibility (infiltration and dispersity) with polymers. The mass ratio between the nanoparticles and the polymer can significantly affect the microstructure and surface properties. As nanoparticle content and aggregation increase, the surface of the coating gradually develops submicron and nanoscale peaks and holes. The contact angle increases sharply to 155° when β = 1.4, showing super-hydrophobicity. However, excessive nanoparticle content causes mechanical failure of the coating surface. Considering the self-cleaning and anti-fouling properties as well as the mechanical properties of the surface, the bionic lotus leaf surface achieves the best comprehensive performance when β = 1.4.
Citation: Functional Materials Letters
PubDate: Mon, 29 Dec 2014 06:38:52 GMT
DOI: 10.1142/S179360471550037X

• Non-Debye relaxation and resonance phenomena in dielectric spectra of
CaCu3Ti4O12 family functional ceramic materials
• Authors: A. V. Turik, A. S. Bogatin
Abstract: Functional Materials Letters, Ahead of Print.
Experimental data on dielectric spectra of calcium copper titanate, CaCu3Ti4O12 (CCTO) family functional ceramics have been studied and analyzed. It is shown that there are both non-Debye relaxation and resonance regions in their spectra. An occurrence of a retardation of complex permittivity and a relaxation of electric modulus is established. An average relaxation frequency of the electric modulus is considerably (in some cases several orders of magnitude) larger than the retardation frequency of the permittivity. A parallel connection of the capacity and complex conductivity is used to model and interpret experimental data on a negative permittivity in the infralow frequency range. Computer simulation enables us to reveal that the hopping conductivity, characteristic for disordered heterogeneous systems, is to be taken into account to describe adequately experimental data on passing the real part of the capacity (or permittivity) through zero. We have found a critical frequency at which the parallel resonance would take place.
Citation: Functional Materials Letters
PubDate: Tue, 23 Dec 2014 09:26:04 GMT
DOI: 10.1142/S1793604715500356

• Improving dielectric properties and thermal conductivity of polymer
composites with CaCu3Ti4O12 and β-SiC hybrid fillers
• Authors: Xin Ouyang, Peng Cao, Weijun Zhang, Zhaohui Huang, Wei Gao
Abstract: Functional Materials Letters, Ahead of Print.
In this paper, we report a series of homogeneous polymeric composites with enhanced dielectric properties and thermal conductivity. The composites were constituted of polyvinylidene fluorides (PVDFs) matrix and CaCu3Ti4O12 (CCTO) monolithic or CCTO/β-SiC hybrid fillers, and prepared by simple melt blending and hot moulding technique. The influence of different types of fillers and their composition on the dielectric response and thermal conductivity of the obtained composites was studied. Results show that hybrid loading is preferred and a reasonable combination of thermal conductivity (0.80 W ⋅ m-1 ⋅ K-1), dielectric constant (~50) and dielectric loss (~0.07) at 103 Hz was achieved in the PVDF composite containing 40 vol.% CCTO and 10 vol.% β-SiC. The strong dipolar and interfacial polarization derived from the fillers are responsible for the enhancement of the dielectric constant, while the formation of thermally conductive networks/chains by β-SiC whiskers contributes to the improved thermal conductivity.
Citation: Functional Materials Letters
PubDate: Tue, 23 Dec 2014 09:26:04 GMT
DOI: 10.1142/S1793604715400111

• Selectivity and mixed reactant fuel cells
• Authors: Ilan Riess
Abstract: Functional Materials Letters, Ahead of Print.
Mixed reactant fuel cells (MR-FCs), are aimed at using a uniform mixture of fuel and oxygen applied to both the anode and the cathode. This allows redesign of fuel cells with a significantly simpler construction, having potentially a higher power density, better fuel utilization and be less expensive. The challenge in realizing MR-FCs is finding selective electrodes that can enhance oxygen reduction at the cathode, fuel oxidation at the anode while inhibiting the chemical reaction between the fuel and oxygen in the gas mixture. This task is in particular challenging in solid oxide fuel cells (SOFCs), as they operate at elevated temperatures, where many reactions are easily activated and selectivity is difficult to achieve. As a result no true MR-FC of the SOFC type were reported while some were found for low temperature fuel cells (FCs). The so-called single-chamber-SOFC are not true MR-FCs as they do not contain two selective electrodes, as required. We shall discuss potential ways to search for and develop selective anodes and cathodes for SOFC type MR-FCs. We first consider material properties which should contribute to that goal. This refers to electronic properties of the bulk, band banding under adsorbed specie, point defects in the bulk and on the surface. We then proceed to show how cell design, in particular electrode structure, can contribute to selectivity. Finally operation conditions are considered and it is shown that they also can contribute to selectivity. The operation condition considered are gas mixture composition, gas mixture residence time in the hot zone, hence gas flow rate, current density and temperature. The topics discussed hold for all FC types but are crucial for the SOFC type because of the difficulty to achieve selectivity at elevated temperatures. It is suggested that a concerted effort taking advantage of all those options should allow development of a true SOFC type MR-FC.
Citation: Functional Materials Letters
PubDate: Tue, 23 Dec 2014 09:26:03 GMT
DOI: 10.1142/S179360471540010X

• Reliable resistive switching and its tunability in La-doped PbTiO3\TiO2
composite bilayer
• Authors: Ying Wang, Shaopeng Lin, Xiaoyue Zhang, Weiming Xiong, Biao Wang, Yue Zheng
Abstract: Functional Materials Letters, Ahead of Print.
Nanoscale La-doped PbTiO3(PLT)\TiO2 (PLTT) composite structures have been fabricated. It shows that the structure presents reliable resistive switching (RS) behavior, and importantly, has great tunability on RS characteristics such as forming/set/reset voltages and resistance ratio by adjusting the PLT layer thickness. Particularly, the set voltage can be tuned at a large range from several volts to dozens of volts. Meanwhile, the set current keeps almost the same, indicating the RS is current dominating. The space-charge-limited current (SCLC) feature indicates that the localized traps are decisive for the RS. Our result sheds light on the prospects of composite structures for designing tunable RS devices.
Citation: Functional Materials Letters
PubDate: Tue, 23 Dec 2014 09:26:00 GMT
DOI: 10.1142/S1793604715500332

• Effects of hydrothermal temperature on the morphology and
photoelectrocatalytic performance of TiO2-based nanomaterials
photoelectrode
• Authors: Dong Li, Xiujuan Yu, Xiuwen Cheng
Abstract: Functional Materials Letters, Ahead of Print.
TiO2-based nanomaterials (BNMs) photoelectrode was successfully synthesized via a facile and controllable hydrothermal procedure. The as-prepared TiO2-BNMs photoelectrode was characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The resulting TiO2-BNMs samples assembled by different morphologies were obtained through changing hydrothermal temperature that were: (i) One-dimensional (relative to nanosheets) nanobelts at 140°C, (ii) two-dimensional nanosheets at 160–180°C and (iii) three-dimensional network nanowires at 200–220°C. Structural investigation of the obtained nanomaterials revealed that the content of anatase increased as increasing the apparent dimensionality of the materials. The photoelectrochemical performance of TiO2-BNMs photoelectrode was elucidated by comparative investigation on the electron transport and electron–hole (e-/h+) recombination in TiO2-BNMs sample with typically morphology. The photoelectrochemical performance of the TiO2-BNMs sample was obviously dependent on the morphology. Compared to the nanobelts and the network nanowires structure, the two-dimensional nanosheets displayed the more effective photogenerated electron transfer and reduced electron–hole recombination rate. Moreover, two-dimensional nanosheets had significantly enhanced photoelectrocatalytic efficiency for degradation of methyl orange (MO).
Citation: Functional Materials Letters
PubDate: Tue, 23 Dec 2014 09:25:59 GMT
DOI: 10.1142/S1793604715500344

• Enhanced adhesion and conductivity of Cu electrode on AlN substrate for
thin film thermoelectric device
• Authors: Shaoxiong Hu, Xin Chen, Yuan Deng, Yao Wang, Hongli Gao, Wei Zhu, Lili Cao, Bingwei Luo, Zhixiang Zhu, Guang Ma, Yu Han
Abstract: Functional Materials Letters, Ahead of Print.
The Cu thin film electrode grown on aluminum nitride (AlN) substrate is widely used in the thin film thermoelectric devices due to its high electrical conductivity. We have developed a new type of buffer layer by co-sputtering Ti and Cu forming Ti–Cu layer. The Ti–Cu layer was sputtered on the Ti buffered AlN substrate so that the adhesion and electrical conductivity properties of the Cu film electrode on AlN substrate could be improved. The interface between the thin films and the substrate were characterized by the scanning electron microscope (SEM). Nanoscratch tests were conducted on a nanomechanical test system to investigate the adhesion between the Cu film electrodes and AlN substrate. Meanwhile, accelerated ageing test under thermal cycling was conducted to evaluate the reliability of the thin film electrode. The results show that the adhesion and the reliability of Cu film electrode on AlN substrate have been greatly improved by employing Ti–Cu/Ti buffer layers.
Citation: Functional Materials Letters
PubDate: Tue, 23 Dec 2014 09:25:58 GMT
DOI: 10.1142/S1793604715500320

• Synthesis of Ag decorated graphene-hierarchical TiO2 nanocomposite with
enhanced photocatalytic activity
• Authors: Li Fu, Yuhong Zheng, Zhuxian Fu, Wen Cai, Jinpin Yu
Abstract: Functional Materials Letters, Ahead of Print.
Reduced graphene oxide (RGO) wrapped TiO2/Ag ternary nanocomposite was synthesized via a wet chemical method. The synthesized nanocomposite was characterized using UV-Vis spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX) and X-ray Diffraction (XRD). The average size of RGO wrapped TiO2 and deposited Ag nanoparticles were 3.2 μm and 48 nm, respectively. Due to the highly facilitated electron transport by the synergistic effect between RGO sheets and Ag nanoparticles, the TiO2/RGO/Ag nanocomposite exhibited a significant enhancement of photocatalytic activity towards degradation of methylene blue under UV light.
Citation: Functional Materials Letters
PubDate: Tue, 23 Dec 2014 09:25:58 GMT
DOI: 10.1142/S1793604715500368

• Preparation of lignite-based activated carbon with high specific
capacitance for electrochemical capacitors
• Authors: Baolin Xing, Jianliang Cao, Yan Wang, Guiyun Yi, Chuanxiang Zhang, Lunjian Chen, Guangxu Huang, Bing Xu
Abstract: Functional Materials Letters, Ahead of Print.
A lignite-based activated carbon (LAC) for electrochemical capacitors (ECs) was prepared from high moisture lignite by KOH activation, and the as-prepared sample was characterized by the N2-sorption, scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical performances of ECs with activated carbon as electrodes in 3 M KOH aqueous solution were evaluated by constant current charge-discharge and cyclic voltammetry. The LAC exhibits a well-developed surface area of 2581 m2/g, a relative wide pore size distribution of 0.5–10 nm. The ECs with LAC as electrode materials presents a high specific capacitance of 392 F/g at a low current density of 50 mA/g, and still remains 315 F/g even at a high current density of 5 A/g. The residual specific capacitance is as high as 92.9% after 2000 cycles. Compared with the commercial activated carbon (Maxsorb: Commercial product, Kansai, Japan), the LAC based electrode materials shows superior capacitive performance in terms of specific capacitance and charge–discharge performance at the high current density.
Citation: Functional Materials Letters
PubDate: Tue, 02 Dec 2014 01:33:09 GMT
DOI: 10.1142/S1793604715500319

• Structural and optical properties of KNN nanocubes synthesized by a green
route using gelatin
• Authors: Gh. H. Khorrami, A. Kompany, A. Khorsand Zak
Abstract: Functional Materials Letters, Ahead of Print.
Sodium potassium niobate nanoparticles [(K0.5Na0.5)NbO3, KNN], KNN-NPs, were synthesized using a modified sol–gel method. Structural and optical properties of the prepared samples were investigated by thermogravometric analyzer (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman and UV–Vis spectroscopy. The XRD patterns showed that the formation of the orthorhombic KNN-NPs starts at 500°C calcination temperature. Raman spectroscopy was used to investigate the crystalline symmetry and the structural deformation of the prepared KNN-NPs. TEM images showed that the morphology of the prepared particles is cubic, with the average size of about 50 nm. From diffused reflectance spectroscopy along with using Kubelka–Munk method, the energy bandgaps were determined to be indirect with the values of 3.13 eV and 3.19 eV for the samples calcined at 500°C and 600°C, respectively.
Citation: Functional Materials Letters
PubDate: Tue, 02 Dec 2014 01:33:08 GMT
DOI: 10.1142/S1793604715500307

• An non-centrosymmetric mononuclear Zr complex exhibiting UV
second-harmonic-generation
• Authors: Cai-Yun Han, Mei Qu, Qin-Qin Dang, Xian-Ming Zhang
Abstract: Functional Materials Letters, Ahead of Print.
A novel non-centrosymmetric (NCS) orthorhombic complex Zr(dmpu)2Cl4 (1) has been solvothermally prepared in situ from starting materials of Zirconium(IV) acetylacetonate (Zr(acac)4) and N,N-dimethylpropyleneurea (dmpu), in which dmpu can act not only as solvent but also as organic ligand of monodentate oxygen donor. The second-harmonic generation (SHG) measurements reveal that complex 1 has a strong response of 1.4 times that of potassium dihydrogen phosphate (KDP) at 532 nm based on the Kurtz–Perry method. Furthermore, optical transmission study indicates that complex 1 has a wide transparency range in the UV region (200–850 nm) with a cutoff at 291 nm. According to first-principles calculations, the enhanced macroscopic SHG response of 1 can be attributed to the organic ligand dmpu. Therefore, 1 could be a promising candidate for non-linear optical material.
Citation: Functional Materials Letters
PubDate: Tue, 02 Dec 2014 01:33:08 GMT
DOI: 10.1142/S1793604715500290

• Effect of Sn on sensing performance of nanostructred ZnO film
• Authors: Yongqin Chang, Changjing Shao, Nan Jiang, Shiqi Wang, Bo Zou, Yi Long
Abstract: Functional Materials Letters, Ahead of Print.
Nanostructured ZnO films were fabricated by chemical vapor deposition (CVD) method with different Sn source concentrations for ethanol and acetone sensing applications. The samples prepared with Sn:ZnO (weight ratio) of 0.1:1, 0.2:1 and 0.3:1 are named as S1, S2 and S3, respectively. It was found that hexagonal wurtzite structure of ZnO is maintained after Sn doping. The S1 sample shows the highest response to acetone, while the S2 sample shows the highest response to ethanol, which confines that the as-grown ZnO films with different Sn source concentrations exhibit obvious selectivity to ethanol and acetone. Working temperature can also be reduced by the increase of Sn source concentration. All the samples have very short average recovery time. Our work provides a prospective approach to obtain high performance gas sensor for ethanol and acetone.
Citation: Functional Materials Letters
PubDate: Tue, 02 Dec 2014 01:33:08 GMT
DOI: 10.1142/S1793604715400093

• Piezoelectric properties of rhombohedral ferroelectric materials with
phase transition
• Authors: Xiaofang Zhao, A. K. Soh
Abstract: Functional Materials Letters, Ahead of Print.
The temporal evolution of domain structure and its piezoelectric behavior of ferroelectric material BaTiO3 during the transition process from rhombohedral to tetragonal phase under an applied electric field have been studied by employing Landau–Ginzburg theory and the phase-field method. The results obtained show that, during the transformation process, the intermediate phase was monoclinic MA phase, and several peak values of piezoelectric coefficient appeared at the stage where obvious change of domain pattern occurred. In addition, by comparing the cases of applied electric field with different frequencies, it was found that the maximum piezoelectric coefficient obtained decreased with increasing frequency value. These results are of great significance in tuning the properties of engineering domains in ferroelectrics, and could provide more fundamentals to the design of ferroelectric devices.
Citation: Functional Materials Letters
PubDate: Wed, 19 Nov 2014 02:00:58 GMT
DOI: 10.1142/S1793604715400081

• Effects of flow rate of atmosphere gases on the characteristics of
Zn-doped ITO (ZITO) thin films for organic light emitting diodes
• Authors: Hwa-Kyun Jeong, Kyu-Mann Lee
Abstract: Functional Materials Letters, Ahead of Print.
We have investigated the effect of ambient gases on the structural, electrical, and optical characteristics of Zn-doped indium tin oxide (ZITO) thin films intended for use as anode contacts in organic light emitting diodes (OLED) devices. These ZITO thin films are deposited by radio frequency (RF) magnetron sputtering under different ambient gases (Ar, Ar + O2 and Ar + H2) at 300°C. In order to investigate the influences of the oxygen and hydrogen, the flow rate of oxygen and hydrogen in argon mixing gas has been changed from 0.1 sccm to 0.5 sccm and from 0.1 sccm to 1 sccm, respectively. The intensity of the (400) peak in the ZITO thin films increases with increasing H2 flow rate whilst the (400) peak was nearly invisible in an atmosphere of Ar + O2. The electrical resistivity of the ZITO thin films increases with increasing O2 flow rate, whereas the electrical resistivity decreases with increasing H2 flow rate. The change of electrical resistivity with changes in the ambient gas composition is mainly interpreted in terms of the charge carrier mobility and the charge carrier concentration. All the films show an average transmittance of over 80% in the visible range. The optical bandgap of the ZITO films increases with increasing H2 flow rates, whereas the optical bandgap of the ZITO films deposited in an O2 atmosphere decreases with increasing O2 flow rates. The current density and the luminance of the OLED devices with ZITO thin films deposited in 1 sccm of H2 ambient gas are the highest among all the films. The optical bandgap energy of ZITO thin films plays a major role in OLED device performance, especially the current density and luminance.
Citation: Functional Materials Letters
PubDate: Tue, 18 Nov 2014 01:48:01 GMT
DOI: 10.1142/S179360471540007X

• Electrochemical oxidation of glucose on gold nanoparticle-modified reduced
graphene oxide electrodes in alkaline solutions
• Authors: Qiaofang Shi, Guowang Diao, Shaolin Mu
Abstract: Functional Materials Letters, Ahead of Print.
A given amount of gold is electrodeposited on the reduced graphene oxide (RGO)/glassy carbon (GC) electrodes to form Au/RGO/GC electrodes, which are carried out at different potentials. The Au/RGO/GC electrode with Au loading of 250 μg cm-2 prepared at a constant potential of -0.30 V exhibits the best electrocatalytic activity to glucose oxidation in alkaline solutions because of homogeneous dispersion of gold nanoparticles with smaller sizes. This electrode shows long-term stability, rapid charge transfer ability, and higher current density compared to other gold electrodes reported previously.
Citation: Functional Materials Letters
PubDate: Tue, 18 Nov 2014 01:48:01 GMT
DOI: 10.1142/S1793604715400044

• Efficient reduction of graphene oxide nanosheets using Na2C2O4 as a
reducing agent
• Authors: Mohamad Fahrul Radzi Hanifah, Juhana Jaafar, Madzlan Aziz, A. F. Ismail, M. H. D. Othman, Mukhlis A. Rahman, M. N. A. M. Norddin, N. Yusof, W. N. W. Salleh
Abstract: Functional Materials Letters, Ahead of Print.
The efficient synthesis of reduced graphene oxide (RGO) nanosheets via chemical reduction process of exfoliated graphene oxide (GO) nanosheets was performed by introducing sodium oxalate (Na2C2O4) as a reducing agent. To study the effects of the reduction time on the synthesized RGO, the GO was reduced within -1/2, 1 and 2 h for RGO-1, RGO-2 and RGO-3, respectively. The C/O atomic ratio of the synthesized RGO-3 has increased from 2.16 to 6.32 after reduction as determined by X-ray photoelectron spectroscopy (XPS). The morphology analysis of the RGO-3 was determined by high-resolution transmission electron microscopy (HRTEM) almost revealed the formation of single layer. The number of RGO layers decreases as the time of the reduction increases. Based on these analysis results, sodium oxalate plays an important role in the efficient removal of the oxygen containing groups in the GO to produce high quality of RGO.
Citation: Functional Materials Letters
PubDate: Tue, 18 Nov 2014 01:48:01 GMT
DOI: 10.1142/S1793604715500265

• The magnetism of BiFeO3 powders
• Authors: Xi Luo, Li-Ting Tseng, Sean Li, Jiabao Yi
Abstract: Functional Materials Letters, Ahead of Print.
Conventional sintering and direct ball milling of Bi2O3 + Fe2O3 mixture were used for the fabrication of BiFeO3 powders. The fabricated powders were performed annealing or high energy ball milling to vary the grain size from bottom-up or top-down. It was found that the magnetization of the powders synthesized by both methods plotted with the reciprocal of the grain size could be linearly fitted, indicating that the magnetism is from the finite size effect. Exchange bias phenomenon was observed after field cooling (FC) of the powders, confirming the magnetization is due to the uncompensated or canted surface spins. No spin glass behavior was found in these powders.
Citation: Functional Materials Letters
PubDate: Tue, 18 Nov 2014 01:48:00 GMT
DOI: 10.1142/S1793604715500277

• Metal molybdate nanorods as non-precious electrocatalysts for the oxygen
reduction
• Authors: Tian Wu, Lieyu Zhang
Abstract: Functional Materials Letters, Ahead of Print.
Development of non-precious electrocatalysts with applicable electrocatalytic activity towards the oxygen reduction reaction (ORR) is important to fulfill broad-based and large-scale applications of metal/air batteries and fuel cells. Herein, nickel and cobalt molybdates with uniform nanorod morphology are synthesized using a facile one-pot hydrothermal method. The ORR activity of the prepared metal molybdate nanorods in alkaline media are investigated by using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperomety in rotating disk electrode (RDE) techniques. The present study suggests that the prepared metal molybdate nanorods exhibit applicable electrocatalytic activities towards the ORR in alkaline media, promising the applications as non-precious cathode in fuel cells and metal–air batteries.
Citation: Functional Materials Letters
PubDate: Tue, 18 Nov 2014 01:48:00 GMT
DOI: 10.1142/S1793604715400056

• Enhancement effects of two kinds of carbon black on piezoelectricity of
PVDF-HFP composite films
• Authors: Bin Hu, Ning Hu, Liangke Wu, Hao Cui, Ji Ying
Abstract: Functional Materials Letters, Ahead of Print.
Two kinds of carbon black (CB) (i.e., CB#300 and CB#3350) were added into poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), respectively, to improve its piezoelectricity. The results revealed that when 0.5 wt.% CB was added, the best performance of the PVDF-HFP/CB composite films was obtained. The calibrated open circuit voltage and the density of harvested power of 0.5 wt.% CB#3350 contained composite films were 204%, and 464% (AC) and 561% (DC) of those of neat PVDF-HFP films. Similarly, for 0.5 wt.% CB#300 contained films, they were 211%, and 475% (AC) and 624% (DC), respectively. The enhancement mechanisms of piezoelectricity were clarified by the observation of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscope (SEM). We found that the added CBs act as nucleate agents to promote the formation of elongated, oriented and fibrillar β-phase crystals during the fabrication process, which increase the piezoelectricity. Overdosed CBs lead to a lower crystallinity degree, resulting in the lower piezoelectricity. Compared with CB#3350, CB#300 performs slightly better, which may be ascribed to its higher specific surface area.
Citation: Functional Materials Letters
PubDate: Tue, 18 Nov 2014 01:48:00 GMT
DOI: 10.1142/S1793604715400068

• Improved thermoelectric efficiency in p-type ZnSb through Zn deficiency
• Authors: Qilong Guo, Sijun Luo
Abstract: Functional Materials Letters, Ahead of Print.
We herein report a feasible approach to improve the thermoelectric performance of p-type ZnSb compound by Zn content regulation. It is found that Zn vacancies formed by Zn deficiency not only efficiently enhance the electrical conductivity due to the improved hole concentration but also markedly lower the lattice thermal conductivity on account of the reinforced point defect scattering of phonons. The ZnSb compound with a nominal 3 mol.% Zn deficiency shows a maximum thermoelectric figure of merit ZT of ~0.8 at 700 K which is a ~60% improvement over the pristine sample. The strategies of further enhancing the performance of ZnSb-based material have been discussed.
Citation: Functional Materials Letters
PubDate: Tue, 18 Nov 2014 01:48:00 GMT
DOI: 10.1142/S1793604715500289

• Synthesis of spinel LiMn2O4 cathode material by a modified solid state
reaction
• Authors: Jiawei Zhang, Shudong Lin, Keyan Li, Fenfen Shua, Kunfeng Chen, Liqiu Wang, Dongfeng Xue
Abstract: Functional Materials Letters, Ahead of Print.
Spinel LiMn2O4 was synthesized by a modified solid state reaction. We pretreated the reactants using tartaric acid as complexing agent through a grinding process to obtain uniform distribution of metal ions at atomic level. The structures, morphologies and electrochemical properties of the products were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and galvanostatic charge-discharge test. The results show that adding tartaric acid during the chemical pretreatment plays an important role in the formation of regular and uniform particles, which is beneficial to the electrochemical performance of LiMn2O4. At the current density of 100 mA g-1, the discharge capacity is 118 mAh g-1 after 50 cycles with the capacity retention of 97%.
Citation: Functional Materials Letters
PubDate: Mon, 10 Nov 2014 06:38:47 GMT
DOI: 10.1142/S1793604715400020

• Enhanced piezoelectricity and photoluminescence in Dy-doped
• Authors: Fengying Lei, Na Jiang, Lingling Luo, Yongquan Guo, Qiaoji Zheng, Dunmin Lin
Abstract: Functional Materials Letters, Ahead of Print.
Lead-free multifunctional ceramics of Ba0.85Ca0.15Ti0.9Zr0.1O3-x mol% Dy have been prepared by an ordinary sintering method and the effects of Dy2O3 doping on structure, piezoelectric, ferroelectric and photoluminescent properties of the ceramics have been studied. The ceramics possess a single phase perovskite structure. The grain growth of the ceramics is prohibited and the ferroelectric–paraelectric phase transition at TC becomes more diffusive after the addition of Dy2O3. Dy2O3 doping improves the piezoelectricity of the ceramics and the optimal piezoelectric properties d33 = 335 pC/N is obtained at x = 0.5. The addition of 2 mol% Dy enhances the photoluminescent properties of the ceramics and strong emissions at ~ 478 nm and ~ 575 nm are observed. Our study shows that the ceramics with low Dy2O3 levels exhibit simultaneously the strong piezoelectricity, ferroelectricity and photoluminescence and may have a potential application in mechano-electro-optic integration and coupling device.
Citation: Functional Materials Letters
PubDate: Mon, 10 Nov 2014 06:38:46 GMT
DOI: 10.1142/S1793604715400019

• Material and physical model for evaluation of deep brain activity
contribution to EEG recordings
• Authors: Yan Ye, Xiaoping Li, Tiecheng Wu, Zhe Li, Wenwen Xie
Abstract: Functional Materials Letters, Ahead of Print.
Deep brain activity is conventionally recorded with surgical implantation of electrodes. During the neurosurgery, brain tissue damage and the consequent side effects to patients are inevitably incurred. In order to eliminate undesired risks, we propose that deep brain activity should be measured using the noninvasive scalp electroencephalography (EEG) technique. However, the deeper the neuronal activity is located, the noisier the corresponding scalp EEG signals are. Thus, the present study aims to evaluate whether deep brain activity could be observed from EEG recordings. In the experiment, a three-layer cylindrical head model was constructed to mimic a human head. A single dipole source (sine wave, 10 Hz, altering amplitudes) was embedded inside the model to simulate neuronal activity. When the dipole source was activated, surface potential was measured via electrodes attached on the top surface of the model and raw data were recorded for signal analysis. Results show that the dipole source activity positioned at 66 mm depth in the model, equivalent to the depth of deep brain structures, is clearly observed from surface potential recordings. Therefore, it is highly possible that deep brain activity could be observed from EEG recordings and deep brain activity could be measured using the noninvasive scalp EEG technique.
Citation: Functional Materials Letters
PubDate: Mon, 10 Nov 2014 06:38:46 GMT
DOI: 10.1142/S1793604715400032

• Red-emitting AlN:Mn2+ phosphors prepared by combustion synthesis
• Authors: Zhongqi Shi, Yongyong Zou, Ruifeng Jing, Kuo Zhang, Guanjun Qiao, Hongjie Wang
Abstract: Functional Materials Letters, Ahead of Print.
Red-emitting Mn2+-doped AlN (AlN:Mn2+) phosphors were successfully prepared by a highly effective combustion synthesis method. The phase purity, morphology, element-composition and luminescence properties of the synthesized phosphors were investigated. X-ray diffraction (XRD) results show that the Mn2+-doped into the AlN host did not induce a second phase and distort the structure significantly. Scanning electron microscopy (SEM) images display that the phosphors have an irregular shape with a particle size in the range of 1–5 μm. X-ray photoelectron spectroscopy (XPS) spectrum indicates that Mn ions are divalent state. The synthesized AlN:Mn2+ phosphors exhibit a strong red emission centered at ~ 600 nm, which is ascribe to the 4T1(4G)–6A1(6S) transition of Mn2+ under ultraviolet excitation. The emission intensity reaches its maximum when Mn2+-doped concentration is 3 mol%.
Citation: Functional Materials Letters
PubDate: Fri, 07 Nov 2014 03:54:05 GMT
DOI: 10.1142/S1793604715500253

• Adsorptive performance for methylene blue of magnetic Ni@activated carbon
nanocomposites
• Authors: Panfeng Wang et al
Abstract: Functional Materials Letters, Ahead of Print.
Owing to the unique microporous structure and high specific surface area, activated carbon (AC) can act as a good candidate for functional materials. In this paper, Ni@AC magnetic nanocomposites with excellent magnetic response are synthesized by the hydrothermal method. All Ni@AC nanocomposites present ferromagnetism and Ni nanoparticles exist in the pores of AC. The saturation magnetization (Ms) increases with the increasing content of Ni, while the specific surface area and pore volume decrease. The S-50 sample possesses the parameters of the specific surface area of 1156.8 m2 ⋅ g-1 and Ms of 3.5 emu/g. Furthermore, the methylene blue (MB) removal analysis indicates that 99% MB can be adsorbed in 50 min. The as-prepared Ni@AC nanocomposites present good adsorptive capacity of MB and can be separated easily from water by magnetic separation technique.
PubDate: Thu, 30 Oct 2014 03:41:01 GMT
DOI: 10.1142/S1793604715500241

• Comparison of photovoltaic performance of TiO2 nanoparticles based thin
films via different routes
• Authors: Yajun Ji
Abstract: Functional Materials Letters, Ahead of Print.
Well crystallized TiO2 nanoparticles were prepared by hydrothermal and sol–gel routes, respectively. The morphologies, structures, crystallinity and optical properties of resulted TiO2 nanoparticles-based thin films via the two methods were examined by field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD) and reflectance spectra. In addition, comparison of photovoltaic performance of TiO2 nanoparticles-based thin films by the two methods was performed. It is found that the maximum energy conversion efficiency of 4.06% was achieved based on the obtained electrode via hydrothermal, which is much better than that of the sol–gels route. The uniform film structure with improved dye absorption capability, increased diffused reflectance property and relatively low charge recombination rates for injected electrons are believed to be responsible to the superior photoelectrochemical properties of dye-sensitized solar cells (DSSC) via hydrothermal route.
PubDate: Fri, 24 Oct 2014 09:28:48 GMT
DOI: 10.1142/S179360471550023X

• Luminescence properties and first principles calculations of Dy3+
activated Sr3B2O6 phosphors
• Authors: Lihan Cai et al
Abstract: Functional Materials Letters, Ahead of Print.
A novel white-light-emitting Sr3B2O6:Dy3+ phosphor was prepared by solid-state reactions and its luminescence properties were investigated. The excitation spectrum of obtained phosphor monitored at 479 nm covers a very broad spectral region from 320 nm to 460 nm with peaks at 323, 349, 363, 386, 427 and 456 nm. Under excitation at 349 nm, the phosphor exhibits a blue emission centered at 479 nm and a yellow emission centered at 574 nm. The optimal doping concentration of Dy3+ is obtained to be 7 mol%, and the concentration quenching is observed when the concentration of Dy3+ exceeds 7 mol%. This concentration quenching is due to the enhanced energy exchange among Dy3+ ions. The CIE chromaticity coordinate (0.289, 0.302) of Sr3-0.07B2O6:0.07 Dy3+ located in the white-light region can be achieved. Theoretical calculations of electronic properties for Sr3B2O6:Dy3+ phosphor in the framework of the density functional theory (DFT) were carried out. Our results suggest that the Sr3B2O6:Dy3+ phosphor is a promising single-component white-light-emitting material.
PubDate: Tue, 21 Oct 2014 03:47:38 GMT
DOI: 10.1142/S1793604715500228

• Preparation of nanoporous graphene and the application of its
nanocomposite membrane in propylene/propane separation
• Authors: Hai-Xiang Sun et al
Abstract: Functional Materials Letters, Ahead of Print.
Chemically reduced graphene oxide containing hydroxyl groups and a wide size distribution of nanopores was prepared by a facile one-pot hydrothermal method. The resulting material was characterized by transmission electron microscopy (TEM), Raman spectroscopy, surface area measurement and attenuated total reflection infrared spectroscopy (ATR-FTIR), respectively. It was found that this reduced graphene oxide exhibited more clear nanopores and hydroxyl groups in the basal plane. Then the morphologies of the nanocomposite membrane incorporated into the nanoporous graphene were investigated through scanning electron microscopy (SEM), and the permeation test also was performed. Notably, the results showed that the nanocomposite membrane had a homogenous morphology and a better performance (separation factor 11.09) than polymer membrane in the separation of propylene/propane. This work demonstrates that nanoporous graphene exhibits great potential in the field of olefin/paraffin separation.
PubDate: Tue, 21 Oct 2014 03:47:38 GMT
DOI: 10.1142/S1793604715500198

• Transport properties of Bi2Se3 thin films grown by magnetron sputtering
• Authors: Z. T. Wei et al
Abstract: Functional Materials Letters, Ahead of Print.
Epitaxial growth of Bi2Se3 thin films is of great current interest due to the advantages in spintronics and thermoelectrical applications. In this paper, Bi2Se3 thin films on Si (111) substrate have been prepared via magnetron sputtering deposition with post-annealing treatment and their microstructures and electrical transport properties were studied. Good quality with highly c-axis oriented films could be obtained after post-annealing treatment. The annealing temperature (Ta) obviously affected the phase structures and electrical properties. The crystallinity and the lattice parameters c of the Bi2Se3 thin-films increased with increasing Ta. The relative atomic ratio of Se/Bi decreased with increasing Ta and large number of Se vacancies was discovered in films with Ta = 350°C. The resistivity of films decreased monotonously and showed weakly metallic resistivity with the increase of Ta. Non-saturated high-field linear magnetoresistance and weak antilocalization were found in films with higher Ta.
PubDate: Tue, 21 Oct 2014 03:47:38 GMT
DOI: 10.1142/S1793604715500204

• Uniform Bi2O2CO3 hierarchical nanoflowers: solvothermal synthesis and
photocatalytic properties
• Authors: Feng Cao et al
Abstract: Functional Materials Letters, Ahead of Print.
Well-defined flowerlike Bi2O2CO3 nanostructures were fabricated by a simple one-pot solvothermal method with high yield. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy, nitrogen sorption, photoluminescence spectra and UV–visible diffuse reflectance spectroscopy. The photocatalytic properties of the as-prepared samples were further investigated by photocatalytic decomposition of Rhodamine B (RhB) dye, and it was found that the Bi2O2CO3 nanoflowers showed a good photocatalytic activity under UV light. The excellent photocatalytic performance of Bi2O2CO3 flowerlike nanostructures is related to its special nanostructure and morphology, indicates its potential application in photocatalysis and nanosensors.
PubDate: Tue, 21 Oct 2014 03:47:36 GMT
DOI: 10.1142/S1793604715500216

• Synthesis and photocatalytic property of porous metal oxides nanowires
based on carbon nanofiber template
• Authors: Weiqiang Fan et al
Abstract: Functional Materials Letters, Ahead of Print.
A series of porous metal oxides nanowires (Fe2O3, Co3O4, NiO and CuO) have been successfully synthesized, where commercial carbon nanofibers were used as the template. The obtained samples were systematically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–Vis diffuse reflectance (UV–Vis DR) spectra and transmission electron microscope (TEM). According to the photodegradation data, the porous metal oxides nanowires exhibit significantly photocatalytic activity for degrading tetracycline (TC). Furthermore, the porous Fe2O3 nanowires show the best photocatalytic performance among all the samples.
PubDate: Fri, 10 Oct 2014 05:49:44 GMT
DOI: 10.1142/S1793604715500186

• Electrical properties modulation of thin film solar cell using gold
nanostructures at textured FTO/p–i–n interface
• Authors: A. Gentile et al
Abstract: Functional Materials Letters, Ahead of Print.
We report about the modulation of the electrical properties of thin film solar cells due to the incorporation of size-selected Au nanostructures (NSs) at a textured FTO/p–i–n interface. By increasing the Au NSs size, the analyses of current-voltage characteristics show lower Schottky barrier heights and the gradual reduction of the open-circuit voltages (VOC). The optical measurements show higher parasitic absorption by larger Au NSs that reduces the amount of radiation transmitted by the transparent to absorber layer. This process decreases the number of photo-generated carriers and may explain the VOC reduction related to the devices with larger Au NSs at the interface. So, the correlation between materials properties and device performances was established.
PubDate: Wed, 01 Oct 2014 10:07:01 GMT
DOI: 10.1142/S1793604715500174

• Fabrication of ordered mesoporous carbon film supporting vanadium oxides
for electrochemical supercapacitor
• Authors: Chunxia Zhao et al
Abstract: Functional Materials Letters, Ahead of Print.
Ordered mesoporous carbon film supporting vanadium oxide nanoparticles has been synthesized via ultrasound-assistant impregnation method with ordered mesoporous carbon C-FDU15 film as the host and V2O5 sol as the guest precursor. The hybrids exhibit type IV sorption isotherms with H2 hysteresis loop, indicating the well-retained characteristics of ordered mesoporous structure. The capacitance of the materials is enhanced with V2O5 loading. Particularly, the hybrids with 32.26 wt.% V2O5 loading yield an important capacitance of 128 F/g in 1 mol/L KNO3 electrolyte under a potential range from -0.6 V to 0.6 V. The improved specific capacitance of the hybrids is proposed to be the combination of the double-layer capacitance of ordered porous structure and the pseudocapacitance derived from V2O5.
PubDate: Wed, 01 Oct 2014 10:06:48 GMT
DOI: 10.1142/S1793604715500162

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