Direct Gap Research Articles

Terahertz Modulation Properties Based on ReS2/Si Heterojunction Films

Low cost, low power consumption and high performance are urgent needs for the application of terahertz modulation devices in the 6G field. Rhenium disulfide (ReS2) is one of the ideal candidate materials due to its unique direct band gap, but it lacks in-depth research. In this work, a highly stable ReS2 nanodispersion was prepared by liquid-phase exfoliation, and a uniform, dense and well-crystallized ReS2 film was prepared on high-resistivity silicon by drop casting. The morphological, optical and structural properties of the ReS2/Si heterojunction film were characterized by OM, SEM, AFM, XRD, RS and PL. The terahertz performance was tested by using a homemade THz-TDS instrument, and the influence of different laser wavelengths and powers on the terahertz modulation performance of the sample was analyzed. The modulation depth of the sample was calculated based on the transmission curve, and the changes in the refractive index and conductivity of the sample with frequency at the corresponding laser power were calculated. The results show that the fabricated ReS2/Si heterojunction terahertz modulator can stably achieve 30% broadband modulation in the range of 0.3~1.5 THz under the low-power pumping of 1555 mW/cm2, and the maximum conductivity is 3.8 Ω−1m−1.

Designing Zero-Dimensional Cadmium-Based Organic-Inorganic Hybrids: The Role of Halogen Doping in Modulating Multifunctional Properties.

Advances in materials science are increasingly dependent on the development of multifunctional materials capable of improving system efficiency and reducing the environmental impact. In this study, two zero-dimensional (0D) cadmium-based organic-inorganic hybrid materials (BEMPD)2CdBr4 (BEMPD-Br, 1) and (BEMPD)2CdBr2Cl2 (BEMPD-ClBr, 2) (BEMPD = 1-(2-bromoethyl)-1-methylpiperidine) were prepared by halogen doping. Compound 2 is a mixed halide in which there are two halogen sites, Cl and Br, and in a disordered state, which has a regulatory effect on the structural distortion and properties of the compound. The Curie temperatures of compounds 1 and 2 are 348 and 390 K, respectively, and the UV-vis absorption spectra showed that the direct band gaps of compounds 1 and 2 were 4.68 and 4.8 eV, respectively. In addition, room-temperature photoluminescence experiments show broadband emission peaks at 717 and 683 nm for compounds 1 and 2, respectively, with fluorescence lifetimes of 2.414 and 3.915 μs. These 0D hybrids provide an avenue for the development of smart materials and optoelectronic devices, and also provide positive clues for manipulating the properties of organic-inorganic hybrid compounds.

First-principles study of the electronic, optical adsorption, and photocatalytic water-splitting properties of a strain-tuned SiC/WS2 heterojunction

Heterojunction is widely acknowledged as a potent strategy as an effective means for achieving quality electronic, optical adsorption, and photocatalytic water-splitting properties. Strain also can regulate these properties effectively. In this study, we have fabricated and studied a heterojunction comprised SiC and WS2. Utilizing a first-principles method, we systematically investigated the SiC/WS2 heterojunction's structure, stability, electronic, and optical properties, as well as its photocatalytic water splitting characteristics under strain engineering. Our calculations reveal that the SiC/WS2 heterojunction is a type-II heterostructure with two stable structures, which exhibits a direct bandgap and well performance in the visible light region, facilitating efficient separation of photogenerated electron-hole pairs. We have explored and discussed the impacts of biaxial strain on the various properties. The bandgaps of System-A and B are 1.778 eV and 1.820 eV, respectively, without strain. Under strain from −6% to 10%, they initially rise, peak at 1.858 eV and 1.899 eV respectively at −2% strain, then decline. Without strain, effective mass mh/me for both structures are 1.642 and 1.673. Under positive strain, they increase, decrease, then increase again, peaking at 6% with 2.116 and 2.260. At −2% strain, values drop to 0.901 and 0.910 for A and B, respectively. Our calculations also demonstrate that the SiC/WS2 heterostructure qualifies as a promising photocatalytic material, fulfilling the criteria for water splitting under strain conditions of −4%, −2%, and 0%. And the heterojunction with System-B under −4% strain has the optimal performance in photocatalytic water splitting. At a strain of −4%, System-B achieves the maximum η′STH of 16.91%. In conclusion, our study not only offers fundamental insights into the utilization of SiC/WS2 heterojunctions for photocatalytic water splitting, but also provides the foundational design principles of heterojunctions.

Cobalt-Doped ZnO Nanocomposits for Efficient Dye Degradation: Charge Transfer.

Doping enhances the optical properties of high-band gap zinc oxide nanoparticles (ZnO NPs), essential for their photocatalytic activity. We used the combustion approach to synthesize cobalt-doped ZnO heterostructure (CDZO). By creating a mid-edge level, it was possible to tune the indirect band gap of the ZnO NPs from 3.1 eV to 1.8 eV. The red shift and reduction in the intensity of the photoluminescence (PL) spectra resulted from hindrances in electron-hole recombination and sp-d exchange interactions. These improved optical properties expanded the absorption of solar light and enhanced charge transfer. The field emission scanning electron microscopy (FESEM) image and elemental mapping analysis confirmed the CDZO's porous nature and the dopant's uniform distribution. The porosity, nanoscale size (25-55 nm), and crystallinity of the CDZO were further verified by high-resolution transmission electron microscopy (HRTEM) and selected area electron image analysis. The photocatalytic activity of the CDZO exhibited much greater efficiency (k=0.131 min-1) than that of ZnO NPs (k=0.017 min-1). Therefore, doped heterostructures show great promise for industrial-scale environmental remediation applications.

Non‐Monotonic Variation of the Low Lattice Thermal Conductivity with Temperature in Penta‐HgO2 Sheet

AbstractInspired by the experimental synthesis of bulk HgO2 with the potential of exfoliation to form a penta‐HgO2 sheet composed entirely of pentagonal motifs, a detailed theoretical study on the lattice thermal conductivity by using first‐principles calculations combined with the unified theory of thermal transport is performed. It is found that the penta‐HgO2 sheet is semiconducting with an indirect bandgap of 1.18 eV and possesses a low lattice thermal conductivity of 2.07 W m−1 K−1 (3.28 W m−1 K−1) along the x (y)‐direction at 300 K. More interestingly, the variation of its thermal conductivity with temperature is non‐monotonic, different from most cases. The phonon dispersion, phonon scattering, and phonon coherence is further systematically investigated to understand the underlying physics. This results suggest that the strong intrinsic anharmonicity resulting from its unique atomic configuration with the buckled structure and the heavy element of Hg leads to a high scattering rate, resulting in the ultralow particle‐like thermal transport of 0.20 W m−1 K−1 (0.01 W m−1 K−1) in the x (y)‐direction, while the narrow average frequency interval and strong phonon linewidth are responsible for the dominant coherent thermal transport and non‐monotonic variation of the low lattice thermal conductivity of the penta‐HgO2 sheet.

Theoretical prediction of chalcogen-based Janus monolayers for self-powered optoelectronic devices

Exploring potential two-dimensional monolayers with large photogalvanic effect (PGE) has been of great importance for developing self-powered optoelectronic devices. In this paper, we systematically investigate the generation of PGE photocurrent in chalcogen-based Janus XYZ monolayers (X/Y/Z = S, Se, Te; X ≠ Y ≠ Z) based on non-equilibrium Green's function formalism with density functional theory. The optimized Janus SSeTe, SeSTe, and TeSeS monolayers in the rectangular phase are shown stable and, respectively, possess 1.54, 1.49, and 1.74 eV indirect bandgaps. Illuminated by linearly polarized light, the PGE photocurrent without bias voltage can be collected in both armchair and zigzag directions. Unlike common Janus 2D materials with C3v symmetry, the photocurrent peak values of Janus XYZ monolayers do not come up with certain polarization angles, while the relations can be fitted by Iph = α sin(2θ) + β cos(2θ) + γ at each photon energy. Meanwhile, the maximum photoresponses of Janus SSeTe, SeSTe, and TeSeS monolayers are 2.02, 3.33, and 4.42 a20/photon, respectively. The relatively large PGE photocurrents and complicated polarization relations result from the lower symmetry of Janus XYZ monolayers. Moreover, the specific polarization angles for maximum photoresponses at each photon energy and the ratio between two transport directions are demonstrated, reflecting the anisotropy. Our results theoretically predict a potential Janus monolayer family for self-powered optoelectronic applications.

Characterization of polycrystalline bulk ferroelectric ZnSnS3 synthesized by hydrothermal method for photovoltaic application

ZnSnS3, a newly theoretically predicted ferroelectric material which shows promising properties for solar cell and photovoltaic applications, was successfully grown in our laboratory by hydrothermal method. The high intensity x-ray diffraction pattern from the (211), (101̅), (200), (210), (310), (320), and (321̅) planes reveal the crystalline character of the trigonal ZnSnS3 phase. The microstructural property and elemental distribution were evaluated using SEM and TEM studies. Diffuse reflectance measurement at room temperature shows a direct bandgap of 2.62 eV along with a high energy direct transition of 3.13 eV. Two broad photoluminescence peaks at various temperatures (4–300 K) were also detected around (2.61–2.73 eV) and (3.04–3.11 eV). The emission characteristics are explained considering the shallow donor level to valence band transitions. Raman study elucidates that the synthesized ZnSnS3 possess a good number of Raman active bands. A phase transition from the ferroelectric to non-ferroelectric phase of ZnSnS3 is observed around 330 °C in DSC and dielectric measurements. The P-E measurement showed that the material is ferroelectric in nature with saturation polarization value of 21.85μC/cm2. The current-voltage characteristics showgood photovoltaic response of the fabricated Ni/ZnSnS3/Ni device in the visible range indicating its application in PV devices and photodetector.

Structural, optical, and electronic properties of cerium doped BaTiO3: Experimental study and DFT calculation

The barium titanate Ba1-xCe2x/3TiO3 (BCTx, x = 0, 1, 2 and 3 %) have been produced using the sol-gel process. The impact of cerium concentration on structure and optical properties was examined using techniques such as X-ray diffraction, infrared spectroscopy, Raman spectroscopy and UV–visible spectroscopy. DFT calculation were carried out on BCTx to obtain an extensive comprehension of the relationship between the structure and electronic properties of BCTx. The findings demonstrate a tetragonal structure for BCT0 and a pseudo-cubic for the doped samples. The UV–visible study indicates a successive reduction in bandgap due to vacancies in the A site, lattice defect formation and local bond distortion. For every sample, the electronic band structure showed a direct band gap. The partial density of states (PDOS) revealed that the valence band was dominated by the 2p orbitals of the O atoms. However, the conduction band was formed by the 3d orbitals of the Ti atom.

Organic‐Inorganic Hybrid Cuprous‐Based Metal Halides with Unique Two‐Dimensional Crystal Structure for White Light‐Emitting Diodes

AbstractTernary cuprous (Cu+)‐based metal halides, represented by cesium copper iodide (e.g., CsCu2I3 and Cs3Cu2I5), are garnering increasing interest for light‐emitting applications owing to their intrinsically high photoluminescence quantum yield and direct band gap. Toward electrically driven light‐emitting diodes (LEDs), it is highly desirable for the light emitters to have a high structural dimensionality as it may favor efficient electrical injection. However, unlike lead‐based halide perovskites whose light‐emitting units can be facilely arranged in three‐dimensional (3D) ways, to date, nearly all ternary Cu+‐based metal halides crystallize into 0D or 1D networks of Cu−X (X=Cl, Br, I) polyhedra, whereas 3D and even 2D structures remain mostly uncharted. Here, by employing a fluorinated organic cation, we report a new kind of ternary Cu+‐based metal halides, (DFPD)CuX2 (DFPD+=4,4‐difluoropiperidinium), which exhibits unique 2D layered crystal structure. Theoretical calculations reveal a highly dispersive conduction band of (DFPD)CuBr2, which is beneficial for charge carrier injection. It is also of particular significance to find that the 2D (DFPD)CuBr2 crystals show appealing properties, including improved ambient stability and an efficient warm white‐light emission, making it a promising candidate for single‐component lighting and display applications.

The impact of halogens on the structural, electronic, and optical properties of vacancy-ordered double perovskites Rb2SeX6 (X=I, Br, Cl)

Lead-based perovskite materials have become one of the most widely used materials in the field of photovoltaics due to their excellent properties. However, concerns over lead toxicity and the stability of materials have prompted the search for alternative, eco-friendly, and stable perovskite materials. To address this need, our study conducts an in-depth analysis of the electronic and optical properties of the lead-free double perovskite materials Rb2SeX6 (X = Cl, Br, I) using first-principles calculations. The results indicate that Rb2SeX6 perovskites possess an indirect bandgap, with values of 3.26 eV, 2.52 eV and 1.39 eV for Rb2SeCl6/Br6/I6, respectively. Rb2SeI6 has larger dielectric function and superior absorption spectrum across the visible range than the other two materials. Thus, Rb2SeI6 has a promising future as a photoelectric material for solar cells. Rb2SeCl6 and Rb2SeBr6 also have the potential for use in photodetectors, light-emitting diodes and other optoelectronic devices.

Study of ultra-wide bandgap beryllium based perovskite ZBeF3 (Z = Na, Rb, Cs) alloys for smart window applications: A DFT insights

UV radiation affects the human body due to the fact that it might penetrate through the skin and damage biological cells. In the present study, density functional theory (DFT) within the Perdew-Burke-Ernzerhof (PBE) approximations (GGA-PBE) is used to examine certain structural, optical, electronic, and physical characteristics exhibited by the beryllium-based cubic perovskite ZBeF3 (Z = Na, Rb, Cs) compounds. The substances ZBeF3 (Z = Cs, Na, Rb) exhibit space group 221-pm3m, with (4.07, 3.61, and 3.89) Å lattice factors and (67.76, 47.33, and 58.88) Å3 volumes that correspond to their structural features. Simulated findings show that the ZBeF3 (Z = Cs, Na, Rb) exhibit indirect bandgaps of 5.19, 6.12, and 6.61 eV, respectively. All compounds appear to be insulators based on their band structure features. Optical characteristics of compounds such as conductivity, absorption, and reflectivity that represent the interaction between light and matter are investigated. These materials appeared to be robust but brittle, as demonstrated by their greater bulk modulus B with respect to elastic properties, Pugh's ratio, and B/G ratios, in addition to Vickers hardness. According to research, the compound ZBeF3 can be applied to cars, sunglasses, and room windows to serve as UV protection and a reflecting layer.

On the response of the CR-39 NTD to low doses of gamma rays using optical and photoluminescence spectroscopy

In this work, the response of the CR-39 nuclear track detector (NTD) exposed to different low doses of gamma rays was investigated using UV–Vis and photoluminescence spectroscopy. Five NTDs of CR-39 were irradiated with low gamma-ray doses ranging from 10 to 120 kGy using a60Co source. The dose of gamma rays correlates with red shift in the absorption spectra of a gamma-irradiated CR-39 detector. As the gamma dose increases, the indirect and direct energy band gaps, as well as Urbach energy, decrease gradually. However, the decrease in the indirect optical band gap is greater than the decrease in the direct band gap. The observed spectra of the CR-39 detector after being irradiated with different doses of γ-rays showed an acceptable variation in photoluminescence (PL) emission spectra generated by a well-defined excitation wavelength of 290 nm. Starting at 45 kGy dose, the integrated area of the photoluminescence peak increases and tends to saturate, whereas the photoluminescence peak height is linearly correlated with the gamma dose with high sensitivity, which is 53.1 ± 6.3 CPS. kGy−1. According to the current findings, photoluminescence (PL) spectroscopy has a greater sensitivity than UV–Vis spectroscopy for measuring the response of the CR-39 detector to gamma rays in the dose range of 10–120 kGy. The results reflected a potential possibility of using the CR-39 detector in dosimetric applications of low gamma ray doses through the high resolution achieved by photoluminescence (PL) and UV–Vis spectroscopy.

DFT-based simulation for the semiconductor behavior of XGeCl3 (X=K, Rb) halide perovskites under hydrostatic pressure

In this work, the structural and electronic properties of XGeCl3 (X=K, Rb) crystallized in cubic cell (Pm-3m, 221) were presented under hydrostatic pressure from 0 to 8 GPa using the first-principal Density Functional Theory (DFT) under the Perdew–Burke–Ernzerhof (PBE) form of the generalized gradient approximation (GGA). The Projector Augmented Wave (PAW) method describing electron–ion interaction was used here. For XGeCl3 (X=K, Rb), the lattice constants were calculated as 5.171 and 5.197 Å, and the band gaps were predicted as 0.5802 and 0.657 eV, respectively at ambient pressure. It was observed that the lattice parameters and bond lengths of the XGeCl3 (X=K, Rb) compounds decreased with increased pressure. The applied hydrostatic pressure reduced the band gaps, and the metallic character was detected at 5 GPa for both structures. This study provides a theoretical basis that may have potential uses in optoelectronic applications of the XGeCl3 (X=K, Rb) perovskites.

Nanostructured MnMoO4 as a trifunctional electrocatalyst for overall water splitting and CO2 reduction

Electrochemical water splitting and CO2 reduction are important processes to produce hydrogen and low–carbon fuels as renewable energy sources. Here, nanostructured MnMoO4, prepared by the reflux precipitation method, was investigated as a trifunctional electrocatalyst for overall water splitting and CO2 reduction reactions. Using a combination of diffuse reflectance spectroscopy and electrochemical impedance spectroscopy results, a direct band gap of 3.05 eV was obtained experimentally for the prepared MnMoO4. An overpotential of 0.36 V at a current density of 5 mA cm−2 and a Tafel slope of 58 mV dec−1 were obtained for the oxygen evolution reaction. At a current density of 3 mA cm−2, overpotentials of 0.39 V and 0.58 V were achieved in the absence and presence of CO2 bubbling into a 0.1 M KOH solution, respectively, emphasizing the poisoning effect of CO2 reduction intermediates for the hydrogen evolution reaction. Based on the obtained results, MnMoO4 could be a promising electrocatalyst for water splitting and CO2 reduction reactions.

Effects of applied pressure on structural, electronic, and optical properties of magnesium incorporated wurtzite beryllium oxide at different magnesium compositions

The effects of applied pressure on the structural, electronic, and optical properties of magnesium-incorporated wurtzite beryllium oxide (w-BeO) at different magnesium compositions are calculated. Each compound at different applied pressures confirms stability in the wurtzite phase. At different applied pressures, the equilibrium lattice constants (a0, c0) increase, but the bulk modulus (B0) and the c0/a0 ratio decrease with increasing magnesium composition. With increasing pressure, the lattice constants of each specimen decrease nonlinearly. Each compound possesses a wide direct band gap (Г-Г) at different applied pressures. The calculated band gap decreases with increasing magnesium composition at different applied pressures. With an increase in applied pressure, the band gap of each compound increases. Each wurtzite specimen is optically anisotropic and exhibits birefringence. Electronic excitations from O-2p to Be-2s, 3p and Mg-3s, 3p are responsible for the various optical features of the considered alloys. At different applied pressures, static optical constants ε1(0), n(0), and R(0) increase, but critical points in the ε2(ω), k(ω, σ(ω), and α(ω) spectra decrease with increasing magnesium composition. For each specimen, components of static optical constants reduce, while components of critical point energies increase with an increase in applied pressure.

Ultrafast Decay of Interlayer Exciton in WS2/MoSe2 Heterostructure Under Pressure

AbstractAtomically thin transition metal dichalcogenides (TMDs) heterostructures provide a rich platform for exploring fascinating physics and engineering strategies. A pressure strategy is developed to effectively manipulate the physical properties in such heterostructures. However, there is still a lack of studies on the corresponding pressure‐modulated evolution of carrier dynamics, which is crucial to the performance of electronic and optoelectronic devices. Here, utilizing the diamond anvil cell, the interlayer exciton dynamics of WS2/MoSe2 heterostructure are subtly manipulated by pressure. Intriguingly, with pressure modulation, the enhanced interlayer coupling accelerates the recombination of spatially separated electron and hole, which significantly shortens the interlayer exciton lifetime from 37.10 ps at 0.0 Gpa to 3.03 ps at 2.2 Gpa. For comparison, the intralayer exciton lifetime of monolayer MoSe2 is increased due to the transition of direct to indirect bandgap under pressure. Furthermore, the pressure‐regulated band structure and interlayer coupling are confirmed by photoluminescence and Raman spectroscopy. The results demonstrate that pressure provides a powerful tuning knob for interlayer exciton relaxation of TMDs heterostructure, which is attractive to various electronic and optoelectronic applications based on such heterostructure.

Nickel stanogermanides thin films: Phases formation, kinetics, and Sn segregation

Ge1−xSnx thin films with a Sn content of x ≥ 0.1 present a direct bandgap, which is very interesting for the fabrication of efficient photonic devices. The monostanogermanide phase, Ni(GeSn), is promising to form ohmic contact in GeSn-based Si photonic devices. However, the formation kinetics of Ni stanogermanides and the incorporation of Sn in Ni–GeSn phases are not fully understood. In this work, Ni thin films were deposited on Ge and Ge0.9Sn0.1 layers grown in epitaxy on an Si(100) substrate using magnetron sputtering technique. In situ x-ray diffraction measurements were performed during the solid-state reaction of Ni/Ge and Ni/Ge0.9Sn0.1. 1D finite difference simulations based on the linear parabolic model were performed to determine the kinetics parameters for phase growth. The nucleation and growth kinetics of Ni germanides are modified by the addition of Sn. A delay in the formation of Ni(GeSn) was observed and is probably due to the stress relaxation in the Ni-rich phase. In addition, the thermal stability of the Ni(GeSn) phase is highly affected by Sn segregation. A model was developed to determine the kinetic parameters of Sn segregation in Ni(GeSn).

Facile hydrothermal synthesis of Sb2S3 thin-film photo-cathodes for green hydrogen energy production

Semiconducting characteristics of antimony-based chalcogenides in the recent past gained the utmost attention for photovoltaic (PV) cells and photo electrochemical (PEC) hydrogen evolution. In the current research endeavour, a simple hydrothermal route has been employed to prepare polycrystalline Sb2S3 thin films. Under ideal temperature conditions of 120 °C, Sb2S3 films were prepared in an autoclave, varying the reaction times between 10:00 and 14:30 h with an interval of 30 min. Further heat treatment of the as-synthesized Sb2S3 thin films was carried out on an electric hot plate at 200 °C for 90 min. XRD analysis of heat-treated Sb2S3 films unveiled an orthorhombic crystal structure with (310) predominant plane. Consequently, the crystallite sizes, displayed improvement from ∼ 33 to 77 nm, with reaction periods for 10:00 to 13:30 h and decreased after that. The five distinct Raman modes were spotted at 155, 190, 236, 280, and 305 cm−1, further confirming the single-phase formation of Sb2S3 thin films. SEM and EDS analysis indicated conspicuous variations in surface morphology and stoichiometric ratios of antimony and sulfur elements. The Sb2S3 thin films deposited at 120 °C for 13:30 h are found to be nearly stoichiometric (Sb and S are 42.61 and 57.39 at. %). The resultant oxidation states were demonstrated to be (+3) and (−2) for antimony and sulfur respectively. All the thin films exhibited an optical absorption coefficient greater than 104 cm−1 with a direct energy band gap ranging between 1.43 and 1.61 eV. The Sb2S3 thin films deposited for 13:30 h have unveiled the highest photocurrent density of −0.27 mA/cm2, indicating a potential photocathode for hydrogen production.

Optical, AC conductivity and antibacterial activity enhancement of chitosan-silver nanocomposites for optoelectronic and biomedical applications

This study is aimed to prepare and investigate the optical, electrical and antibacterial activity of the environmentally friendly (green) chitosan (Cs)/silver nanocomposites. TEM demonstrated that AgNPs have a spherical shape with particle size ranged from 3 nm to 25 nm. UV analysis spectra of Cs and Cs/Ag nanocomposites showed that, increasing the content of AgNPs led to a noticeable increase in the values of Urbach energy (E U ) and a dramatic decrease in both the indirect (E ig ) and direct (E dg ) optical bandgap energies. It is found that (E ig ) and (E dg ) are decreased from (4.72/5.31 eV) to (2.47/4.19 eV). The formation of the AgNPs is verified by the existence of surface plasmon resonance (SPR) peak at ∼ (421–450) nm. Wemple-DiDomenico and Sellmeier oscillator models are employed and displayed a clear enrichment in the dispersion energy (E d ) and oscillator energy (E 0) as well as the linear and nonlinear optical parameters of Cs. It is observed that the linear (χ(1)) and nonlinear (χ(3) and n2) parameters are enhanced from 0.083, 0.868 × 10−14 and 1.584 × 10−12 to 0.153, 9.762 × 10−14 and 4.088 × 10−12. The novel results in our study nominate Cs/Ag nanocomposites for applications in linear/nonlinear optical devices. AC conductivity behavior of Cs and Cs/Ag nanocomposites is analyzed based on Jonscher’s law and the analysis showed that the overlapping large polaron tunneling (OLPT) is the dominant conduction mechanism for our samples. It is clear that the values of dielectric constant (ε′) of Cs and Cs/Ag nanocomposites are higher confirming the presence of interface polarization (IP) relaxation. Moreover, it is found that the antibacterial activity of Cs against Gram-negative (P. aeruginosa) and Gram-positive (B. thuringiensis) bacteria is found to be enhanced with increasing the content of Ag NPs. These results suggested that Cs/Ag nanocomposites will be good source for preparing bio-nanocomposites for use in many biomedical and industrial applications.

Tunable electronic and optical properties of a Type-ⅡViolet Phosphorus/MoS2 heterojunction: First-principles calculation

Photodetectors based on heterostructures have garnered significant research interest due to their superior self-powering and responsiveness capabilities. In this work, the optoelectronic properties of a violet phosphorus (VP/MoS2)/MoS2 heterojunction are investigated through first-principles calculations. The results reveal that the VP/MoS2 heterojunction possesses an indirect bandgap and a type-II band alignment. The interface potential drop (Ep) of the VP/MoS2 heterojunction is 5.45 eV by studying the interfacial interaction, suggesting the formation of a large in-built electric field and an excellent self-powering capability. The absorption coefficient of VP/MoS2 heterojunction are significantly higher in the UV and visible regions. Under biaxial strain, the VP/MoS2 heterostructure can undergo transformations from a semiconductor to a metal, from an indirect to a direct bandgap, and from a type-II to a type-I energy band structure. Moreover, the light trapping ability in the near-infrared region is significantly enhanced. These findings underscore the broader potential application of VP/MoS2 heterostructures in high-performance optoelectronic devices.