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Journal Cover Modern Physics Letters B
  [SJR: 0.222]   [H-I: 33]   [4 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0217-9849 - ISSN (Online) 1793-6640
   Published by World Scientific Homepage  [118 journals]
  • Dielectric properties of [math]–[math] composite ceramics
    • Authors: Jing Wang, Guijuan Rong, Liangbin Hao, Lan Gao, Haiyan Cheng, Jiali Li, Ruijie Duan
      Abstract: Modern Physics Letters B, Ahead of Print.
      A wet solid-state method was used in this work to produce [math]–[math] materials. By using core-shell structure nanocubic [math] (BMST) decorated [math] (BBT) assemblies, a composite capacitor with improved dielectric constant and enhanced breakdown strength was successfully fabricated in contrast with the composite ferroelectric [math]–[math] (BBT–BST) ceramic. With increasing Mg content, the ceramic capacitors display a stronger performance in its dielectric behavior. The best dielectric properties were obtained in the composition [math] with the dielectric constant above 65,000. The dielectric strength of the ceramics was measured by a withstanding voltage tester. The best dielectric strength was achieved in the composition [math] with [math] kV/mm.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-17T07:23:49Z
      DOI: 10.1142/S0217984916503632
  • Global explicit solutions with n double spectral parameters for the
           Myrzakulov-I equation
    • Authors: Hai Chen, Zi-Xiang Zhou
      Abstract: Modern Physics Letters B, Ahead of Print.
      The Darboux transformation with n double spectral parameters for the Myrzakulov-I equation is obtained by taking suitable limit of the spectral parameters. Global explicit solutions are obtained by using this Darboux transformation with n double spectral parameters.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-17T07:15:40Z
      DOI: 10.1142/S0217984916503589
  • Package of double helical bromine chains inside single-walled carbon
    • Authors: Zhen Yao, Chun Jian Liu, Hang Lv, Xi Bao Yang
      Abstract: Modern Physics Letters B, Ahead of Print.
      The helicity of stable double helical bromine chains inside single-walled carbon nanotubes (SWCNTs) was studied through the calculation of systematic interaction energy, using the van der Waals interaction potential. The results presented clear images of stable double helical structures inside SWCNTs. The optimal helical radius and helical angle of chain structure increase and decrease, respectively, with the increase of tube radius. The detailed analysis indicated that some metastable structures in SWCNTs may also co-exist with the optimal structures, but not within the same tubes. In addition, a detailed simulation of X-ray diffraction patterns was performed for the obtained optimal helical structures.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-17T07:15:38Z
      DOI: 10.1142/S0217984916503590
  • Structural, electronic and optical properties of the [math] in three
    • Authors: Zhu-Hua Yin, Jian-Min Zhang
      Abstract: Modern Physics Letters B, Ahead of Print.
      The structural, electronic and optical properties of the [math], [math] and [math] are studied by the spin-polarized first-principles calculation. The [math] and [math] are metals in tetragonal structures, while the [math] in trigonal structure is half-metal with 100% spin polarization. The [math] has the biggest static dielectric constant [math] and static refractive index [math], which may be ascribed to the highest crystal symmetry. The maximum absorption peaks of the [math], [math] and [math] are located about 44 eV in the ultraviolet region, indicating these materials have good prospect for optoelectronic materials in the ultraviolet range.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-17T07:15:34Z
      DOI: 10.1142/S0217984916503565
  • Optical transmission through metallic split-ring resonator
           with inner cross dimer array
    • Authors: Xin Zhou, Min Ouyang, Zhibing Wang, Diwu Yang, Jun He
      Abstract: Modern Physics Letters B, Ahead of Print.
      We investigate numerically the optical properties through gold split-ring resonator (SRR) with inner cross dimer array by using the finite difference time domain (FDTD) method. The dependence of the geometrical parameters on the optical properties of SRR with inner cross dimer array is studied. The study covers the change of transmission spectra with the metallic cross arm length, width of air slits, width of SRRs and environmental dielectric constants. The spatial distributions of the electric and magnetic fields are also discussed to further understand more basic physical mechanisms behind some dip and peak.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-13T03:14:34Z
      DOI: 10.1142/S021798491650353X
  • Effects of nonmetal doping on electronic structures of NaNbO3 based on
           hybrid density functional calculation
    • Authors: Haifeng Shi, Benyue Lan, Chengliang Zhang, Enjia Ye, Yanguang Nie, Baoan Bian
      Abstract: Modern Physics Letters B, Ahead of Print.
      The influences of a series of anion doping on the electronic structures of sodium niobate (NaNbO3) have been systematically investigated by density functional theory (DFT) calculations with the hybrid B3LYP functional. As for B[math](C,[math]P)-doped NaNbO3, the isolated B 2p (C 2p, P 3p) states were formed above the valence band maximum (VBM) of NaNbO3, which were too weak to mix with O 2p states and thus produced band gap narrowing. While the band gap of NaNbO3 was slightly narrowed after F doping. As for S-doped NaNbO3, the S 3p states mixed with O 2p states well and thus reduced the band gap energy. According to the calculation results, we tentatively put forward that S doping would be appropriate for single anion doping NaNbO3, while the B[math](C,[math]P) elements would be suitable candidates for co-doping NaNbO3.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-13T03:14:34Z
      DOI: 10.1142/S0217984916503504
  • Characteristics of heat transfer with different dimensionless
           distance in an enclosure
    • Authors: Yi-Kun Wei, Hua-Shu Dou, Hui Yang
      Abstract: Modern Physics Letters B, Ahead of Print.
      In this paper, the influence of different dimensionless distance on heat transfer characteristics in a rectangular enclosure is studied using lattice Boltzmann method (LBM). It is shown that the relation between the Rayleigh number (Ra) and the Nusselt number (Nu) using LBM is in promising agreement with that of the previous experimental data by Corvaro and Paroncini [Appl. Therm. Eng. 28 (2007) 25]. It is found that the characteristic of heat transport is closely related to the dimensionless distance of heat source. Special attention is paid to investigate the relation between Ra and Nu. Some relations between Ra and Nu for different dimensionless distance are approximately established in natural convection. It is further found that the heat transport is enhanced with the increase of dimensionless distance.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-13T03:14:33Z
      DOI: 10.1142/S0217984916503541
  • Investigation on microstructure and martensitic transformation of
           neodymium-added NiTi shape memory alloys
    • Authors: Dovchinvanchig Maashaa, Ulzii-Orshikh Dorj, Malrey Lee, Min Hi Lee, Chunwang Zhao, Munguntsetseg Dashjav, Seon-Mi Woo
      Abstract: Modern Physics Letters B, Ahead of Print.
      The effect of rare earth element neodymium (Nd) addition on the microstructure and martensitic transformation behavior of Ni[math]Ti[math]Nd[math] ([math] = 0, 0.1, 0.3, 0.5 and 0.7 at.%) shape memory alloy was investigated by scanning electronic microscope, X-ray diffraction and differential scanning calorimetry. The results show that the microstructure of Ni–Ti–Nd ternary alloy consists of NiNd phase, NiTi2 and the NiTi matrix. A one-step martensitic transformation is observed in the alloys. The martensitic transformation temperature Ms increases sharply increasing 0.1–0.7 at.% Nd content is added.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-13T03:14:33Z
      DOI: 10.1142/S0217984916502869
  • The luminescent carbon nanoparticles with controllable oxygen-related
           functional groups prepared by pulsed laser ablation in water
    • Authors: Jun Zhang, Zhixing Gan, Guang Hu, Yalu Tang, Lei Zhou, Qingsong Jiang, Yu Cui
      Abstract: Modern Physics Letters B, Ahead of Print.
      Fluorescent carbon nanoparticles (CNPs) are obtained via pulsed laser ablation (PLA) of a carbon target immersed in deionized water. By tuning the laser power for PLA, the density of oxygen-related functional groups at the surfaces is controllable. While the crystallinities, sizes, morphologies and defects are nearly retained, the prepared CNPs show blue fluorescence under UV exposure and the photoluminescence (PL) intensities of the C-dots are dependent on the oxygen contents. Accordingly, the PL is attributed to the transition of electronic states caused by oxygen-related functional groups. This work sheds new light on the PL mechanism of CNPs and proposes an efficient way to prepare CNPs with controllable oxygen-related functional groups.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-12T02:07:23Z
      DOI: 10.1142/S0217984916503206
  • Dispersion engineering of a As2Se3-based strip/slot hybrid waveguide for
           mid-infrared broadband wavelength conversion
    • Authors: Zhanqiang Hui, Lingxuan Zhang, Leiran Wang, Wenfu Zhang
      Abstract: Modern Physics Letters B, Ahead of Print.
      An arsenic tri-selenide-based strip/slot hybrid waveguide with a single horizontal silica slot is proposed to achieve an extremely low and flat dispersion with three zero dispersion wavelengths. By adjusting the geometrical structural parameters of the hybrid waveguide, dispersion tailoring is fully obtained. The flat group velocity dispersion varying between ±[math]0.08 ps2/(m) is obtained over a 1253 nm bandwidth. The parameters of effective area, nonlinear coefficient, and third-order dispersion are all investigated. Moreover, a compact on-chip all-optical wavelength converter is designed based on degenerate four-wave mixing in this waveguide. The dependencies of conversion efficiency and conversion bandwidth on the pump wavelength are discussed. The impact of pump power and signal power on the conversion efficiency is also investigated. The results show that a maximal conversion efficiency of −0.46 dB, and a 3-dB conversion bandwidth of 830 nm in the mid-infrared is achieved.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-12T02:07:13Z
      DOI: 10.1142/S021798491650336X
  • Quantum consciousness in warm, wet and noisy brain
    • Authors: Valeriy I. Sbitnev
      Abstract: Modern Physics Letters B, Ahead of Print.
      The emergence of quantum consciousness stems from dynamic flows of hydrogen ions in brain liquid. This liquid contains vast areas of the fourth phase of water with hexagonal packing of its molecules, the so-called exclusion zone (EZ) of water. The hydrogen ion motion on such hexagonal lattices shows as the hopping of the ions forward and the holes (vacant places) backward, caused by the Grotthuss mechanism. By supporting this motion using external infrasound sources, one may achieve the appearance of the superfluid state of the EZ water. Flows of the hydrogen ions are described by the modified Navier–Stokes equation. It, along with the continuity equation, yields the nonlinear Schrödinger equation, which describes the quantum effects of these flows, such as the tunneling at long distances or the interference on gap junctions.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-12T02:07:08Z
      DOI: 10.1142/S0217984916503292
  • Conductivities of zinc oxide by finite block spins
    • Authors: Tae Hoon Jo, Myoung Soo Yun, Je Huan Koo, Gi Chung Kwon
      Abstract: Modern Physics Letters B, Ahead of Print.
      In the current work, we have demonstrated the phase of ZnO by reference to block theory, in which the phase may be considered to show a paramagnetic ordering between block spins, which in turn comprise random spins that have a majority of individual spins in a given direction. By making use of the Curie–Weiss law of block spins for zinc oxide, we obtained the susceptibility for the lower approximation of the Brillouin function and calculated the resistivity. The resistivity of ZnO mainly stems from spin glass-like disorders according to our analysis.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-12T02:07:04Z
      DOI: 10.1142/S0217984916503103
  • Pressure-dependent structural, electronic and optical properties of ZnO
           with native defect: A first-principles study
    • Authors: Yonghong Hu, Caixia Mao, Shengli Zhang, Bo Cai
      Abstract: Modern Physics Letters B, Ahead of Print.
      Defects are usually unavoidable in lattices and have great impacts on the electronic structures, which can also be adjusted by pressure. Here, we report a systemic first-principles investigation on the pressure-dependent electronic and optical properties of wurtzite ZnO containing O vacancy or Zn interstitial. The pressure is loaded in the range of 0–12 GPa. The calculated result shows that the top valence bandwidth of ZnO materials varies with the pressure loaded. In particular, the top valence bandwidth of ZnO with O vacancy under about 5 GPa gets an extreme value. Meanwhile, it is also found that there are different energy shifts in the optical spectrums with the increase of pressure. The influence of increasing pressure on the optical properties of ZnO containing Zn interstitial is found to be notable, especially in the energy range of 3.0–4.7 eV. So the electronic and optical properties of ZnO with native defect may be tuned through changing the pressure. Our research results may provide important references to the choice and production of ZnO-based ultraviolet photoelectric materials.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-05T10:02:53Z
      DOI: 10.1142/S0217984916502754
  • A multiband absorber with dielectric–dielectric–metal
           structure in the infrared regime
    • Authors: Yan-Lin Liao, Yan Zhao, He-Ping Lu
      Abstract: Modern Physics Letters B, Ahead of Print.
      We report a multiband absorber with dielectric–dielectric–metal structure in the infrared regime. The simulation results show that that near-perfect absorption is originated from the guide mode resonance and surface plasmonic polaritons (SPPs) excitation. Furthermore, the absorption peaks of this multiband absorber can be tuned by changing the incidence angle or scaling the microstructure dimensions. The results of this study have possible future potential applications in thermal emitter and sensor.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-05T10:02:52Z
      DOI: 10.1142/S0217984916503528
  • A new macro model of traffic flow by incorporating both timid and
           aggressive driving behaviors
    • Authors: Guanghan Peng, Li Qing
      Abstract: Modern Physics Letters B, Ahead of Print.
      In this paper, a novel macro model is derived from car-following model by applying the relationship between the micro and macro variables by incorporating the timid and aggressive effects of optimal velocity on a single lane. Numerical simulation shows that the timid and aggressive macro model of traffic flow can correctly reproduce common evolution of shock, rarefaction waves and local cluster effects under small perturbation. Also, the results uncover that the aggressive effect can smoothen the front of the shock wave and the timid effect results in local press peak, which means that the timid effect hastens the process of congregation in the shock wave. The more timid traffic behaviors are, the smaller is the stable range. Furthermore, the research shows that the advantage of the aggressive effect over the timid one lies in the fact that the aggressive traffic behaviors can improve the stability of traffic flow with the consideration of incorporating timid and aggressive driving behaviors at the same time.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-05T10:02:48Z
      DOI: 10.1142/S0217984916503516
  • Energy spectra and fluence of the neutrons produced in deformed space-time
    • Authors: F. Cardone, A. Rosada
      Abstract: Modern Physics Letters B, Ahead of Print.
      In this work, spectra of energy and fluence of neutrons produced in the conditions of deformed space-time (DST), due to the violation of the local Lorentz invariance (LLI) in the nuclear interactions are shown for the first time. DST-neutrons are produced by a mechanical process in which AISI 304 steel bars undergo a sonication using ultrasounds with 20 kHz and 330 W. The energy spectrum of the DST-neutrons has been investigated both at low (less than 0.4 MeV) and at high (up to 4 MeV) energy. We could conclude that the DST-neutrons have different spectra for different energy intervals. It is therefore possible to hypothesize that the DST-neutrons production presents peculiar features not only with respect to the time (asynchrony) and space (asymmetry) but also in the neutron energy spectra.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-05T10:02:45Z
      DOI: 10.1142/S0217984916503462
  • Three-dimensional few cycle optical pulses in nonlinear
           medium with carbon nanotubes
    • Authors: Mikhail B. Belonenko, Ilya S. Dvuzhilov, Elena N. Galkina, Yulia V. Nevzorova
      Abstract: Modern Physics Letters B, Ahead of Print.
      The theoretical problem of three-dimensional few cycle optical pulse (known as light bullet) propagation dynamics was considered in nonlinear medium containing carbon nanotubes. The stable and persistent propagation of optical pulses were found out.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-04T03:45:49Z
      DOI: 10.1142/S0217984916503450
  • Experimental study on oblique water entry of projectiles
    • Authors: Chenggong Zhao, Cong Wang, Yingjie Wei, Xiaoshi Zhang, Tiezhi Sun
      Abstract: Modern Physics Letters B, Ahead of Print.
      An experimental study of oblique water entry of projectiles with different noses has been conducted using high-speed photography technology. The images of the initial water entry impact, cavity evolution, and the closure and shedding of vortices of cavity are presented in the paper. The results reveal that for high-speed oblique water entry (the initial impact velocity [math] m/s), the cavity attached to the projectile is symmetrical and free from the influence of gravity. The shedding of the water–vapor–air mixture in the tail of the cavity produces vortices which disappear in the rear of the projectile trajectory. Particular attention is given to the velocity attenuation of the projectile after water entry. The results show that there is a transition point at the time corresponding to the surface seal of the cavity during the velocity attenuation after oblique water entry, and the rates of velocity attenuation are different before and after this transition point. Additionally, the chronophotography of the cavity evolution shows that the time when the surface seal of the cavity occurs decreases with the increase of the initial impact velocity of the projectile.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-04T03:45:48Z
      DOI: 10.1142/S0217984916503486
  • Modeling of optical losses in graphene contacted CIGS solar cells
    • Authors: Mohammad Houshmand, M. Hossein Zandi
      Abstract: Modern Physics Letters B, Ahead of Print.
      For the first time, an optical model is applied to superstrate configuration of CdS/CIGS thin film solar cells with graphene front/back contact (FC/BC) to simulate the loss in current density and efficiency. Graphene shows to be a great candidate to replace with the metallic BC transparent conductive oxides as the front electrode. Our model is based on the refractive index and extinction coefficient and takes into account the reflection and absorption in interfaces and layer’s thickness, respectively. CIGS cells with graphene as front electrode have a lower current density and efficiency than the one with graphene BC. However, the bifacial configuration shows a higher current density and efficiency, mostly because of a higher transmission rate. The interference effect was observed in simulation of transmission rate of hybrid cells representing that graphene can cause multiple reflection. We simulated the device parameters versus the ZnO layer’s thickness, which is essential for high quality interfaces. However, the simulation results are also consistent when CdS thickness is replaced with inorganic ZnO.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-03T03:54:11Z
      DOI: 10.1142/S0217984916503425
  • The energy separation effect based on the disk resonance multichannel MIM
    • Authors: Liu Wang, Ya-Ping Zeng, Zhi-Yong Wang, Xiong-Ping Xia, Qiu-Qun Liang
      Abstract: Modern Physics Letters B, Ahead of Print.
      In this paper, a multichannel metal–insulator–metal (MIM) waveguide structure based on a disk resonator is proposed. The transmission characteristics of visible and near-infrared light in the waveguide are investigated by using the finite-difference time-domain (FDTD) method. The results show that the structure has typical band-pass filter function due to the wave resonance in the nanodisk. The energy of the second-order resonance wavelength of the disk can transmit through each output port averagely, which is realized by the energy separation function of the electromagnetic wave. Moreover, the wavelength will transmit through the output port in redshift as the radius and/or the refractive index of the disk are increased. The transmissivity is sharply reduced with the increase of the coupling thickness between the disk and the output port waveguide.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-03T03:54:09Z
      DOI: 10.1142/S0217984916503449
  • Nonlinear analysis of a new car-following model accounting
           for the global average optimal velocity difference
    • Authors: Guanghan Peng, Weizhen Lu, Hongdi He
      Abstract: Modern Physics Letters B, Ahead of Print.
      In this paper, a new car-following model is proposed by considering the global average optimal velocity difference effect on the basis of the full velocity difference (FVD) model. We investigate the influence of the global average optimal velocity difference on the stability of traffic flow by making use of linear stability analysis. It indicates that the stable region will be enlarged by taking the global average optimal velocity difference effect into account. Subsequently, the mKdV equation near the critical point and its kink–antikink soliton solution, which can describe the traffic jam transition, is derived from nonlinear analysis. Furthermore, numerical simulations confirm that the effect of the global average optimal velocity difference can efficiently improve the stability of traffic flow, which show that our new consideration should be taken into account to suppress the traffic congestion for car-following theory.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-03T03:54:08Z
      DOI: 10.1142/S0217984916503279
  • Emergence of ferromagnetism in conducting polymers in the presence of
           lattice vibrations
    • Authors: M. Gulacsi, Z. Gulacsi
      Abstract: Modern Physics Letters B, Ahead of Print.
      The emergence of ferromagnetism in conducting polymers is well known, however, the influence of lattice vibrations has not been analyzed yet. Hereafter, we fill this gap by studying the common effect of strong correlations and lattice vibrations in hole doped conjugated polymers. The results underline that away from system half-filling, the lattice vibrations have negligible effect on the studied ordered phase.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-03T03:54:06Z
      DOI: 10.1142/S0217984916503358
  • Boron-doped cobalt oxide thin films and its electrochemical properties
    • Authors: S. Kerli
      Abstract: Modern Physics Letters B, Ahead of Print.
      The cobalt oxide and boron-doped cobalt oxide thin films were produced by spray deposition method. All films were obtained onto glass and fluorine-doped tin oxide (FTO) substrates at 400[math]C and annealed at 550[math]C. We present detailed analysis of the morphological and optical properties of films. XRD results show that boron doping disrupts the structure of the films. Morphologies of the films were investigated by using a scanning electron microscopy (SEM). Optical measurements indicate that the band gap energies of the films change with boron concentrations. The electrochemical supercapacitor performance test has been studied in aqueous 6 M KOH electrolyte and with scan rate of 5 mV/s. Measurements show that the largest capacitance is obtained for 3% boron-doped cobalt oxide film.
      Citation: Modern Physics Letters B
      PubDate: 2016-10-03T03:54:05Z
      DOI: 10.1142/S0217984916503437
  • Spin polarization current induced by hydrogen hybrid within closed hexagon
           graphene nanoribbon devices
    • Authors: Yun Ren, Jun He, Zhi-Qiang Fan, Xiang Zhu, Yi Liu, Meng-Qiu Long, Ke Xiao
      Abstract: Modern Physics Letters B, Ahead of Print.
      We investigate the spin-polarized electronic transport properties of the closed hexagon graphene nanoribbon devices with different hydrogen hybrid of edge carbon atoms by using non-equilibrium Green’s functions in combination with the density functional theory. The results show that an excellent molecular switching with on/off ratio over 106, perfect spin-filtering effect and negative differential resistance effect have been observed. A detailed analysis has been presented.
      Citation: Modern Physics Letters B
      PubDate: 2016-09-30T08:02:29Z
      DOI: 10.1142/S0217984916503334
  • The effects of electron and hole transport layer with the
           electrode work function on perovskite solar cells
    • Authors: Quanrong Deng, Yiqi Li, Lian Chen, Shenggao Wang, Geming Wang, Yonglong Sheng, Guosheng Shao
      Abstract: Modern Physics Letters B, Ahead of Print.
      The effects of electron and hole transport layer with the electrode work function on perovskite solar cells with the interface defects were simulated by using analysis of microelectronic and photonic structures-one-dimensional (AMPS-1D) software. The simulation results suggest that TiO2 electron transport layer provides best device performance with conversion efficiency of 25.9% compared with ZnO and CdS. The threshold value of back electrode work function for Spiro-OMeTAD, NiO, CuI and Cu2O hole transport layer are calculated to be 4.9, 4.8, 4.7 and 4.9 eV, respectively, to reach the highest conversion efficiency. The mechanisms of device physics with various electron and hole transport materials are discussed in details. The device performance deteriorates gradually as the increased density of interface defects located at ETM/absorber or absorber/HTM. This research results can provide helpful guidance for materials and metal electrode choice for perovskite solar cells.
      Citation: Modern Physics Letters B
      PubDate: 2016-09-30T08:02:28Z
      DOI: 10.1142/S0217984916503413
  • Mechanism of enhanced photocatalytic activities on tungsten trioxide doped
           with sulfur: Dopant-type effects
    • Authors: Dan Li, Wei-Qing Huang, Zhong Xie, Liang Xu, Yin-Cai Yang, Wangyu Hu, Gui-Fang Huang
      Abstract: Modern Physics Letters B, Ahead of Print.
      The enhanced photocatalytic activity of tungsten trioxide (WO3) has been observed experimentally via doping with S element as different dopant types. Herein, a comparative study on the effect of different types of S dopant and native vacancy defects on the electronic structure and optical properties of WO3 is presented by using hybrid Heyd–Scuseria–Ernzerhof 2006 (HSE06) density functional methods. Six possible models (S[math]–WO3, S[math]–WO3, V[math]–WO3, V[math]–WO3, S[math] + V[math]–WO3 and S[math] + V[math]–WO3) based on WO3 are tentatively put forward. It is found that cationic S doping (the substitution of W by S) is more favorable than anionic S doping (replacing O with S), and both cases become easier to form as native vacancy defect is accompanied. The electronic structures of doped WO3 depend on the type of dopant: anionic S doping results into three isolated levels in the upper part of valence band, while cationic S doping only induces an effective band gap reduction, which is critical for efficient light-to-current conversion. Interestingly, the isolated states near gap of WO3 would appear as long as native vacancy defects exist. The introduced levels or reduced band gaps make the systems responsed to the visible light, even further to a range of 400–700 nm. These findings can rationalize the available experimental results and pave the way for developing WO3-based photocatalysts.
      Citation: Modern Physics Letters B
      PubDate: 2016-09-30T08:02:27Z
      DOI: 10.1142/S0217984916503401
  • Laser frequency down-conversion by means of a
           monochromatically driven two-level system
    • Authors: Andrey V. Soldatov
      Abstract: Modern Physics Letters B, Ahead of Print.
      Conditions are found under which a simple two-level quantum system possessing dipole moment operator with permanent non-equal diagonal matrix elements and driven by external semiclassical monochromatic high-frequency EM (laser) field can radiate continuously at much lower frequency. Possible ways to experimental observation and practical implementation of the predicted effect for a wide range of applications are discussed.
      Citation: Modern Physics Letters B
      PubDate: 2016-09-28T01:56:19Z
      DOI: 10.1142/S0217984916503310
  • Enhanced photocatalytic activity and persistent luminescence
           in Zn2GeO4:Mn[math] by Eu[math] doping
    • Authors: Hong Li, Yinhai Wang, Lei Li, Haiju Huang, Hui Zhao, Zhengfa Hu
      Abstract: Modern Physics Letters B, Ahead of Print.
      Zn2GeO4:Mn[math],[math]Eu[math] and Zn2GeO4:Mn[math] powders were synthesized by a high-temperature solid-state reaction. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structures and morphologies of the synthesized powders, respectively. The photocatalytic properties and long persistent luminescence performance were improved by Eu[math] doping. Thermoluminescent (TL) curves showed that the trap concentration in the material was increased with Eu[math] doping, which formed trap centers in Zn2GeO4:Mn[math]. The trap centers can capture the electrons or holes and subsequently increase the separation of photogenerated electrons and holes by suppressing the recombination of captured electrons and holes; thus, resulting in an improved photocatalytic activity and a prolonged persistent luminescence. The present strategy may be used as a general method to improve the photocatalytic activity and persistent luminescence.
      Citation: Modern Physics Letters B
      PubDate: 2016-09-28T01:56:13Z
      DOI: 10.1142/S021798491650305X
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