Shift Of Absorption Edge Research Articles

Modulation of optical, mechanical and radiation shielding characteristics in TeO₂-B2O3–BaO–CeO₂ glasses with varying CeO₂ level

The TeO₂-BaO-CeO₂-B₂O₃ glass samples are synthesized using the melt quenching technique in order to examine the impact of varying concentrations of CeO₂ on their physical, mechanical, optical, and gamma ray shielding capabilities. With an increase in the CeO₂ concentration, the density (ρ) of the glasses increased, so the glass structure became more compact, as shown by the drop in molar volume (Vm) from 27.895 to 27.554 cm³/mol and the reduction in the average distance between boron atoms (<dB-B>) from 4.045 × 10⁻⁸ to 3.919 × 10⁻⁸ cm. The Young's modulus (E) increases from 93.209 to 93.527 GPa, the bulk modulus (B) increased from 73.763 to 74.236 GPa, the shear modulus (G) increased from 38.497 to 38.609 GPa, and the longitudinal modulus (L) increased from 125.093 to 125.714 GPa. The absorption edge shifts towards the longer wavelength side as the amount of CeO₂ increased, changing from 336 nm to 527 nm. This shift was followed by a drop in the energy difference between the valence band and the conduction band, known as the band gap energy (Eg), which decreased from 3.082 to 1.574 eV.The radiation shielding properties for the prepared glasses were investigated using Phy-X software in the energy range of 0.015–15 MeV. The increase of CeO₂ content showed a direct relationship with the radiation shielding characteristics.

Solvothermal synthesized mesoporous BiOCl nano-ellipsoids with oxygen vacancies for photocatalytic degradation of low density polyethylene (LDPE) plastic

This study explores mesoporous BiOCl nanoparticles as a promising photocatalyst for low-density polyethylene (LDPE) degradation under visible light for the first time. A solvothermal synthesis yields BiOCl nanoparticles with a high ratio of exposed {010} facets and abundant oxygen vacancies (OVs). These properties, along with the co-existence of Bi³-x and Bi³⁺x defect states, promote a tailored surface chemistry with high surface-bound hydroxyl groups. These properties optimize light absorption by inducing favorable surface states, leading to a red shift in the light absorption edge for efficient utilization of visible light. Additionally, OVs suppress the recombination of photo-generated charge carriers and enhance their transfer rate. Furthermore, the free-standing LDPE/BiOCl nanocomposite films of 50μm, prepared via solution casting technique with varying BiOCl weight percentages (3, 5, and 7 wt.%), exhibit remarkable photocatalytic activity. The analysis of photodegraded LDPE confirms the presence of carbonyl groups (C.I.= 86%), cracks, pores, and hydroxyl radicals (•OH), alongside reduced thermal stability and band gap changes. Through meticulous analysis of the results obtained, we have ascertained that the optimal photocatalytic degradation of LDPE is achieved by incorporating up to 5 wt.% of BiOCl.

Synthesis, characterization and application of MWCNT/TiO2 composite for photocatalytic reduction of benzophenone to benzopinacol

Photocatalytic reactions are widely investigated as a green chemistry approach towards organic molecule synthesis. Herein, we fabricated (MWCNT/TiO2) composite materials which are beneficial in the photocatalytic synthesis of benzopinacol on irradiation with UV–visible light. The precursor-layer-coating (PLC) method was successfully employed to produce a series of composite materials, X%-MWCNT/TiO2, where (X = 2, 4, 6, and 8 % w/w). The XRD confirmed major-anatase and minor-brookite TiO2 along with MWCNT in the composite. FE-SEM, HR-TEM, and EDAX revealed the expected composite microstructure, morphology, and compositional details. The nanosized (10 ̶30 nm), spherically shaped TiO2 particles were seen integrated to the MWCNT surface. The BET-surface area of the mesoporous composites enhanced from 83.77 to 114.39 m2/g as the MWCNT loading increased from 2 % to 8 %. The optical studies indicated a marginal shift in absorption edge towards longer wavelength with % MWCNT loadings. The band gap (Eg) was reduced and the charge pair recombination rate retarded. The PL, Raman and XPS studies supported the heterojunction formation at the interface. The photocatalytic activity was evaluated based on the % conversion efficiency of benzophenone to benzopinacol in the presence of light and composite as a photocatalyst. The 6 %-MWCNT/TiO2 demonstrated the highest photoactivity with an additional 34 % and 25 % yield in UV and sunlight respectively compared to bare TiO2. The effective light absorption, electronic excitation, charge pair separation and transfer mechanism at the MWCNT/TiO2 interface were responsible for enhanced photoactivity. The current investigation provided a promising strategy to produce hybrid photocatalytic material for organic molecule synthesis.

Epitaxial (AlxGa1−x−yIny)2O3 alloys lattice matched to monoclinic Ga2O3 substrates

We have epitaxially stabilized a series of monoclinic (AlxGa1−x−yIny)2O3 alloys by careful choice of molecular beam epitaxy growth conditions, which balance alloy growth with suboxide desorption. The films are pseudomorphic to (010) β-Ga2O3 substrates at thicknesses up to 150 nm with compositions ranging from (Al0.01Ga0.83In0.16)2O3 to (Al0.24Ga0.75In0.03)2O3. The absorption edge shifts from approximately 4.62–5.14 eV with coincidently increasing Al and decreasing In mole fractions. J–V measurements reveal an increase in resistivity over four orders of magnitude with a maximum value of 4.2 × 105 Ω-cm for (Al0.17Ga0.76In0.07)2O3, which has nearly identical lattice parameters (both in-plane and out-of-plane) to the underlying β-Ga2O3. Scanning transmission electron microscopy of this sample reveals a mostly uniform and single crystalline film, though we identify areas of non-uniform In incorporation and some γ-phase inclusions. This work demonstrates the feasibility of thick layers lattice-matched to β-Ga2O3 with increased bandgap compared to phase-separation limited (Al,Ga)2O3. These alloys can enable higher bandgap epitaxial dielectrics and high sheet charge density transistors by increasing the conduction band offset with respect to β-Ga2O3.

Alloying and Segregation in PdRe/Al2O3 Bimetallic Catalysts for Selective Hydrogenation of Furfural

X-ray absorption fine structure (XAFS) spectroscopy, temperature-programmed reduction (TPR), and temperature-programmed hydride decomposition (TPHD) were employed to elucidate the structures of a series of PdRe/Al2O3 bimetallic catalysts for the selective hydrogenation of furfural. TPR evidenced low-temperature Re reduction in the bimetallic catalysts consistent of the migration of [ReO4]− (perrhenate) species to hydrogen-covered Pd nanoparticles on highly hydroxylated γ-Al2O3. TPHD revealed a strong suppression of β-PdHx formation in the reduced catalysts prepared by (i) co-impregnation and (ii) [HReO4] impregnation of the reduced Pd/Al2O3, indicating the formation of Pd-rich alloy nanoparticles; however, reduced catalysts prepared by (iii) [Pd(NH3)4]2+ impregnation of calcined Re/Al2O3 and subsequent re-calcination did not. Re LIII X-ray absorption edge shifts were used to determine the average Re oxidation states after reduction at 400 °C. XAFS spectroscopy and high-angle annular dark field (HAADF)-scanning transmission electron microscopy (STEM) revealed that a reduced 5 wt.% Re/Al2O3 catalyst contained small Re clusters and nanoparticles comprising Re atoms in low positive oxidation states (~1.5+) and incompletely reduced Re species (primarily Re4+). XAFS spectroscopy of the bimetallic catalysts evidenced Pd-Re bonding consistent with Pd-rich alloy formation. The Pd and Re total first-shell coordination numbers suggest that either Re is segregated to the surface (and Pd to the core) of alloy nanoparticles and/or segregated Pd nanoparticles are larger than Re nanoparticles (or clusters). The Cowley short-range order parameters are strongly positive indicating a high degree of heterogeneity (clustering or segregation of metal atoms) in these bimetallic catalysts. Catalysts prepared using the Pd(NH3)4[ReO4]2 double complex salt (DCS) exhibit greater Pd-Re intermixing but remain heterogeneous on the atomic scale.

SYNCHROTRON BASED X-RAY ABSORPTION SPECTROSCOPY FOR STRUCTURAL ANALYSIS OF BASALT FIBERS

X-ray Absorption Near Edge Structure (XANES) spectroscopy at the Synchrotron Light Research Institute (Thailand) was used to investigate temperature related structural changes in basalt fibers. As a first step, XANES spectra of fiber samples cut from a basalt roving heated for 1 hour at 800 °C were recorded at the K absorption edges of three chemical elements and compared with the spectra of the untreated fibers. Silicon and calcium K-edge XANES spectra of the fibers were not affected by heating, whereas iron K-edge XANES spectra were significantly influenced by heating at 800 °C. The high iron content in basalt fibers has been attributed to their higher thermal stability compared to common natural or synthetic fibers. As a next step, iron K-edge XANES spectra of two types of fibers (basalt roving and uncoated chopped fibers) were recorded after heating at temperatures between 600 °C and 900 °C. In both cases, with increasing temperature the absorption edge shifts to higher energies, indicating progressing oxidation of the iron atoms in the fibers. These experiments demonstrate the potential of X-ray absorption spectroscopy as a powerful analytical tool to investigate structural changes in basalt fibers upon heating and to correlate them with changes in their mechanical properties.

Time-dependent 532 nm laser irradiation for tuning in optical, structural, and surface wettability changes of Te/In2Se3 thin films for optoelectronic applications

Laser irradiation for tuning the optoelectronic parameters of semiconducting thin films is widely applicable and has many benefits. The aim of the study is 532 nm laser irradiation of Te/In2Se3 film at different laser exposure time scales. The bilayer structure and its conversion to a single layer with laser annealing were confirmed from cross-sectional scanning electron microscopy. At the same time, the element's appearance was found in the EDX analysis. FESEM probed the corresponding surface structure change. XRD and Raman's spectroscopy analyzed the increase in crystallinity with laser irradiation by mixing Te into the In2Se3 layer and related microstructural changes. The shift in Raman peak with lasing time signifies the effect of time of exposure. There is a systematic decrement in the transmittance of the films. Also, the absorption edge shift resulted in the decrement in bandgap with laser irradiation. The static refractive index and optical density increased as well. The skin depth was decreased with a minimal change in the optical electronegativity. The nonlinear refractive index increased from 1.638 × 10–9 esu to 1.773 × 10–9 esu by 60 min laser irradiation. Similarly, there was an increment in 3rd-order nonlinear susceptibility from 1.58 × 10–10 esu to 1.73 × 10–10 esu. The surface wettability test confirmed the hydrophilic nature of the samples with decreasing hydrophilicity by laser irradiation. The tuning in different properties of the Te/In2Se3 film by laser irradiation is suitable for various optoelectronic applications.

Synergistic effects of Co-Mn co-doping on the structural and optical properties of TiO2 nanospheres: Dual functions for DSSC photoanodes and degradation photocatalyst

Synthesizing direct solar irradiance-responsive nanomaterial capable of serving as an efficient photoanode for dye-sensitized solar cells (DSSCs) and active photocatalysts for organic pollutant elimination poses a formidable challenge. This study focused on the synthesis of cobalt and manganese co-doped titanium dioxide (TiO2) nanoparticles via sol-gel technique, enhancing their efficacy in both the DSSCs and methylene blue (MB) dye degradation. X-ray diffraction and Raman analysis confirm the existence of a tetragonal crystal structure with the anatase phase of TiO2, while XPS analysis verifies the successful integration of cobalt and manganese ions into the host lattices. BET analysis has confirmed that Co, Mn co-doped TiO2 exhibits a higher pore volume and specific surface area compared to the undoped TiO2 material. FESEM and HR-TEM reveals spherical shape morphology and EDS mapping confirms the purity of synthesized nanoparticles. Moreover, Co-Mn co-doped TiO2 nanoparticles exhibits a shift in the optical absorption edge towards the visible spectrum in UV-DRS analysis. PL analysis suggests a diminished electron-hole recombination within the doped and co-doped sample. Electrochemical impedance spectroscopy demonstrates improved charge transfer properties. DSSCs employing the co-doped TiO2 exhibit significantly enhanced power conversion efficiency (4.99 %) compared to bare TiO2 (2.03 %), cobalt-doped (2.61 %), and manganese-doped TiO2 (3.97 %). Additionally, it demonstrates exceptional photocatalytic activity, with 87.83 % (Co-Mn co-doped TiO2) degradation efficiency with a lesser time extent for the methylene blue dye degradation. These findings underscore the potential of Co-Mn co-doped TiO2 for addressing dual challenges in renewable energy (DSSC) and environmental remediation (Pollutant removal).

Structural, thermo-mechanical, optical and gamma-ray shielding properties of lead-free BaO–ZnO–B2O3–SiO2 and lead-based PbO–Bi2O3–K2O–SiO2 glasses

Lead-free BaO–ZnO–B2O3–SiO2 glass (BZBS) and lead-based PbO–Bi2O3–K2O–SiO2 glass (LS) were synthesized by melt quench technique. Glass samples were irradiated using 60Co gamma source up to 50 kGy dose to study the changes in structural, thermo-mechanical, optical and gamma ray shielding properties. Measured density values of both the glasses were greater than 4.0 g/cc. X Ray Diffraction (XRD) studies confirmed amorphous nature of prepared glasses before and after gamma irradiation. The structural changes induced by gamma irradiation were also investigated using Raman, Positron annihilation lifetime spectroscopy (PALS) and Electron Paramagnetic Resonance (EPR) spectroscopy. PALS data revealed increase in free volume/voids after irradiation. Defect studies carried using EPR spectroscopy confirmed formation of electron trap centre in BZBS glass, whereas in LS glass in addition to the electron trap centers, non-bridging oxygen hole centers (NBOHC) and peroxy radical defects were also observed. Investigations on thermo-mechanical properties demonstrated higher glass transition temperature (Tg), hardness and modulus of elasticity values for BZBS glass as compared to the LS glass, which were found to be decreased after irradiation because of radiation induced defects. Visible transparency and band gap for BZBS glass were found to be higher than that in LS glass. After irradiation, colour change, reduction in transparency as well as band gap, and red shift in absorption edge were observed due to the formation of defects in both the glasses. The values of radiation induced absorption (α) at three different visible wavelengths have been determined for 50 kGy dose using UV–Vis transmission data. Analysis of refractive index data showed around 12 % reflection losses for both the glasses. Annealing of irradiated samples using UV light source showed significant improvement in transparency. Linear attenuation coefficient (LAC) was calculated using XCOM program and experimentally measured using 60Co 1.33 MeV gamma ray. Linear attenuation coefficient of BZBS glass was around 0.20 cm−1 whereas for LS glass value was 0.24 cm−1. Half value layer thickness of prepared glasses was also compared with available standard materials and it was found that prepared glasses may be suitable for shielding of high energy gamma rays.

In search of coloured alloys resembling gold: Structure and optical properties of LiCu2Ga1−xAlx and Li(Cu1–yNiy)2Ga

The Li-containing solid solutions LiCu2Ga1–xAlx and Li(Cu1–yNiy)2Ga were prepared by induction heating. LiCu2Ga1–xAlx retains the Cu2MnAl-type (full Heusler) structure of LiCu2Ga for x = 0–0.7 and then adopts the CsCl-type structure for x = 0.9–1.0. The solid solution Li(Cu1–yNiy)2Ga forms for y = 0–0.5 with the Cu2MnAl-type structure. Solid-state 7Li NMR spectra for LiCu2Ga1–xAlx suggest that Li atoms occupy unique sites, but there is some uncertainty about the intermediate members of this solid solution. These compounds show high reflectivity in the yellow region and an absorption edge caused by interband transitions from filled Cu 3d states to empty bands. The yellow colour of LiCu2Ga gradually changes to red as Ga is substituted by Al because the absorption edge shifts to lower energy, and it becomes lighter yellow as Cu is substituted by Ni because the relative reflectivity decreases. For low levels of substitution by Al (x = 0.1) or Ni (y = 0.1), the chromaticity coordinates are close to those of elemental gold.

Effect of Yttrium doping on enhancing the photocatalytic performance of TiO2/GO nanocomposite

Pure and Yttrium doped Titania/Graphene oxide (YTGO) nanocomposites were synthesized by hydrothermal method. XRD analysis confirmed the crystal structure and anatase phase of TiO2 nanoparticles. The anatase phase of TiO2 has been retained in the composite as confirmed from the XRD pattern. SEM and TEM images revealed that the spherical TiO2 nanoparticles are embedded into sheet like structures of GO. The size of the spherical nanoparticles in the composites is relatively smaller than that of pure sample due to anchoring on the GO sheets. The photocatalytic performance of TiO2 has significantly increased in the Y-doped TiO2 with GO compared to pure TiO2 and TiO2/GO (TGO). Moreover, 0.7 % Y-doped TiO2/GO nanocomposite exhibited superior photocatalytic performance with overall efficiency of 97 % compared to other samples. The 0.7 % Y-doped TiO2/GO nanocomposite shows higher rate constant and shorter half life time compared to other samples. The enhancement of photocatalytic activity of YTGO composites attributed to the combination of increased absorption due to the absorption edge shift and effective separation of photo generated carriers.

Optical properties of nanocomposites based on polypropylene modified by nanoparticles of oxide compounds

The optical properties in UV, visible and near IR spectral regions for nanocomposites based on polypropylene modified by nanoparticles of oxide compounds ZrO2, Al2O3, SiO2, MgO, TiO2, ZnO were studied. A shift of the main optical absorption edge to the short-wave region upon modification by dielectric nanoparticles (MgO, ZrO2, and Al2O3) was established. The absorption edge shifts to the long-wave region upon the introduction of semiconductor nanoparticles (ZnO, TiO2) and amorphous SiO2 particles. In all spectra, the absorption bands at 1200, 1400, and 1720 nm characterized by overtone vibrations of CH, CH2, and CH3 molecular groups were recorded. OH groups make a certain contribution to the bands at 1400 and 1720 nm. The dependence of the intensity of these absorption bands on the type and concentration of nanoparticles used in the modification of polypropylene was analyzed. X-ray diffraction analysis of the studied nanocomposites was carried out, the formation of β-PP was registered upon modification by Al2O3 nanoparticles. Photoluminescence spectra of nanocomposites were studied. It was found that the introduction of nanoparticles (except SiO2) does not lead to the formation of new luminescence bands in PP.

Structural, Optical, Electrical and Photocatalytic Investigation of n-Type Zn2+-Doped α-Bi2O3 Nanoparticles for Optoelectronics Applications.

Herein, n-type pure and Zn2+-doped monoclinic bismuth oxide nanoparticles were synthesized by the citrate sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL) analysis, ultraviolet-visible (UV-vis) spectroscopy, and Hall effect measurements were used to study the effect of Zn2+ on the structural, optical, and electrical properties of nanoparticles. XRD revealed the monoclinic stable phase (α-Bi2O3) of all synthesized samples and the crystallite size of nanoparticles increased with increasing concentration of dopant. Optical analysis illustrated the red shift of absorption edge and blue shift of band gap with increasing concentration of dopant. Hall Effect measurements showed improved values (2.79 × 10-5 S cm-1 and 6.89 cm2/V·s) of conductivity and mobility, respectively, for Zn2+-doped α-Bi2O3 nanoparticles. The tuned optical band gap and improved electrical properties make Zn2+-doped α-Bi2O3 nanostructures promising candidates for optoelectronic devices. The degradation of methylene blue (MB, organic dye) in pure and zinc-doped α-Bi2O3 was investigated under solar irradiation. The optimum doping level of zinc (4.5% Zn2+-doped α-Bi2O3) reveals the attractive photocatalytic activity of α-Bi2O3 nanostructures due to electron trapping and detrapping for solar cells.

Absorption edge shift and broadening in nanostructured Al doped ZnO thin films

Samples of ZnO were prepared by sol-gel and deposited by dip-coating. The influence of synthesis conditions on the optical properties were studied in different sets of ZnO films, synthesized by alternately varying the following parameters: addition of additives to the precursor solution, Al doping percentage and number of layers. The optical properties of the obtained films were studied by transmittance, being typically >90 % at 600 nm. The absorption edge for undoped samples showed a structure due to exciton formation at room temperature. The bandgap energy Eg, was between (3.227 ± 0.010) eV and (3.275 ± 0.010) eV for undoped samples, increasing to (3.352 ± 0.010) eV for Al doped ones (10 % Al/Zn in solution with additives). For intermediate 5 % doping the mean bandgap energy was (3.315 ± 0.015) eV. A similar value (3.320 eV ± 0.010) eV was obtained for 10 % Al/Zn when no additives were included. Doped samples showed a smoother absorption edge. This edge shape evolution was studied by Urbach band tail analysis. The Urbach band tail parameter EU increased with doping, varying from 30 meV to 90 meV and increasing as Eg increases. This correlation describes the influence of impurity states in the structure and optical properties of the material.

Phase Composition of HiVac-VPE Lithium Niobate Optical Waveguides Identified by Spectroscopic Investigations.

High-index contrast lithium niobate waveguides, fabricated by the High Vacuum Vapor-phase Proton Exchange (HiVac-VPE) technique, are very promising for increasing both the optical nonlinear and electro-optical efficiencies of photonic integrated devices. So as to play this role effectively, it is mandatory to know the crystallographic phase composition of waveguides and the position of protonated layers for appropriate tailoring and optimization based on the intended applications. In addition, the estimation of structural disorder and electro-optical properties of the waveguides are also of high interest. Benefiting from Raman spectroscopy, IR reflection, IR absorption, and UV-VIS absorption, the HxLi1-xNbO3 phase compositions, as well as the structural disorder in waveguides, were determined. Based on experimental data on the shift of the fundamental absorption edge, we have quantitatively estimated the electro-optic coefficient r13 in as-exchanged waveguides. The electro-optical properties of the waveguides have been found to be depending on the phase composition. The obtained results allow for reconsidering the proton exchange fabricating process of photonic nonlinear devices and electro-optic modulators based on high-index contrast channel waveguides on the LiNbO3 platform.

Effect of preparation conditions on the surface morphology and edge absorption of ZnGa2O4:Cr thin films

Thin ZnGa2O4:Cr films were obtained by RF ion-plasma sputtering in argon and argon-oxygen atmospheres mixtures on single-crystal NaCl and amorphous υ-SiO2 substrates. The surface morphology of the films was studied by atomic force microscopy. It was found that during the annealing of ZnGa2O4:Cr films on υ-SiO2 substrates in oxygen, the grains forming the film grow along the film surface, and during annealing in an argon atmosphere, the growth of grains is observed normal to the film surface. The region of the fundamental absorption edge was studied by optical spectroscopy. The variation of the optical band gap of Eg depending on the deposition and annealing atmosphere was determined. The total effective mass of free charge carriers and the concentration of free charge carriers are estimated. It is shown that the shift of the fundamental absorption edge in ZnGa2O4:Cr thin films after annealing in an argon atmosphere and when oxygen is added to the sputtering atmosphere is due to the Burstein-Moss effect.

Optimization of Reduction Time for Chemically Synthesized rGO

Introduction: This article presents structural and morphological analysis for graphene oxide (GO) synthesized via Hummers' method and for reduced Graphene Oxide (rGO) prepared by chemical reduction. Graphene Oxide is synthesized from graphite powder at room temperature. Hydrazine hydrate is used as a reducing agent to reduce the accumulated GO. Method: To understand the impact of reduction time on structural parameters of produced rGO, three different time limits, i.e. 4, 5, and 6 hrs at 800 °C are used. FTIR spectra show the presence of all functional groups to confirm the authenticity of rGO samples. The XRD peaks are utilized to calculate different structural parameters for all the samples to identify the effect of reduction time. A change in the band gap energy may be noticed from UV-Vis absorption spectra. Result: It indicates that with the increase in reduction time, the absorption edge shifts to a lower wavelength value. FESEM micrographs reveal a flake-like random growth of rGO with prominent wrinkled structures, which is a signature of graphene-like 2D material. Conclusion: Hence, from the structural and absorption studies, it can be concluded that an increase in reduction time will produce smaller rGO flakes in the Hummers synthesis method.

Electrical and Optical Properties of Thin-Film Wide-Gap Metal Oxides Sno 2, In 2 O 3 , Ito , Cdo , Moo 3

The electrical properties of the created doped and undoped wide-gap layers of metal oxides SnO 2, In 2 O 3 , ITO , CdO , MoO 3 were studied. Depending on technological factors. The optimal growth conditions for these semiconductor materials have been determined. The study of the electro physical and optical properties of the resulting oxide films confirmed the stability of the operational parameters of oxide materials SnO 2, In 2 O 3 , ITO , CdO , MoO 3 . The AFM method showed, along with the oxides SnO 2, In 2 O 3 , ITO , CdO , the oxide of pure MoO3 has The highest transmittance is in the visible region of the spectrum , where the absorption edge shifts toward higher wavelengths.

Plasma assisted pulsed laser deposition of WO3 films for thermochromism

Tungsten trioxide (WO3) is one of the extensively investigated transition metal oxides. Its excellent chromogenic properties make WO3 promising for a variety of scientific and technological applications. We report a new method for reactively depositing WO3 films by plasma assisted pulsed laser deposition that combines electron cyclotron resonance microwave discharge and pulsed laser ablation. The plasma formed during film deposition was spectroscopically characterized by optical emission measurement, revealing that the plasma contains high density of reactive gaseous oxygen and tungsten species which are essential for efficiently synthesizing WOx precursors and depositing WO3 films. The structure of the deposited films and the effect of post-deposition thermal annealing on the film structure were characterized by X-ray diffraction and Raman spectroscopy. The as-deposited WO3 film appears amorphous in nature. Annealing resulted in the growth of crystalline grains and the improvement in the crystallinity of monoclinic WO3. Optical properties of the prepared WO3 films were studied by measuring ultraviolet–visible–near infrared transmission spectra. With the increase of annealing temperature, the WO3 films show a continuous change in color, decline in transmittance, red shift in absorption edge, and narrowing in band gap, clearly manifesting the thermochromic features of the deposited WO3 films.

Microwave assisted synthesis of ZnIn2S4 nanoparticles: effect of power variation for photoresponse and optoelectronic applications.

The ternary ZnIn2S4 has recently gained significant attention due to its potential applications in various optoelectronics and photocatalysis sectors. In the current study, ZnIn2S4 nanoparticles were prepared using a simple microwave-assisted synthesis method with different irradiation powers varying from 180 W-720 W. Structural analysis confirmed their polycrystalline nature with the appearance of ZnIn2S4 and In2S3 phases. The variation in diffraction pattern intensity and Raman vibrational bands with irradiation power indicates structural rearrangements induced with power variation. Morphological studies confirmed the formation of agglomerate nanoparticles with size variation as induced by different microwave powers. Broad absorption across the visible and near-infrared regions and the increased band gap enhance their photocatalytic and sensing applications. An increased irradiation power in the ZnIn2S4 lattice reduced intermediate levels within the band gap, altering the optical responsiveness. The blue shift in absorption edges with microwave power increased the optical band gap by reducing disorder and defects. The refractive indices were estimated using different theoretical models and reduced with an increase in the band gap. Thermal analysis revealed endothermic peaks. These ZnIn2S4 nanoparticles displayed an enhanced photocurrent under white light, increasing tenfold with microwave power. The greater powered ZIS (ZIS-720 W) nanomaterial showed the best photoresponse and is well suited for optoelectronic application. All of their optical and electrical properties make them suitable for various optoelectronic devices, particularly in detection applications.