Band Gap Reduction Research Articles

Structural and Optical Properties of Magnetron-Sputtered Chromium Oxynitride Thin Films

Doping non-metal elements into Cr2O3 can tailor its properties, making it more efficient for applications like sensors or photocatalysis. For this purpose, the current research work presents the impact of nitrogen doping on the structural and optical properties of Cr2O3 thin films. Pure and N-doped Cr2O3 (Cr2O3−xNx) thin films were synthesized using the DC reactive magnetron sputtering approach. The stoichiometry was obtained by raising values of x, where x = 0, 0.125, 0.25, and 0.50. X-ray diffraction analysis confirmed the rhombohedral crystal structure without the presence of any other secondary phase in undoped and N-doped Cr2O3 thin films. Furthermore, crystallinity and average crystallite size have enhanced by doping. Field emission scanning electron micrographs disclosed that the surface morphology of the prepared samples changed considerably with doping. A thorough optical investigation was carried out by spectroscopic ellipsometry. Several optical properties significantly changed with dopant content. The reduction in the optical bandgap from 2.50 eV to 1.82 eV, with N-doping was observed. The study demonstrated that N-doping improves the structural and optical properties that make it a promising candidate for optoelectronic applications.

Electrochemical remediation of methyl orange over reusable biochar ferrite coated photocatalytic plates

Biochar (BC) obtained from biomass pyrolysis holds immense potential for environmental remediation. The efficiency of BC can further be enhanced by incorporating metal nanoparticles (NPs) in the porous carbon matrix. In the present work nanocomposites (NCs) were prepared by the addition of ferrite nanoparticles (FNPs) into an oxidized BC matrix to create BC /Fe3O4 (BCF). This process improves BC stability, electron transfer, conductivity, and photocatalytic ability for dye degradation. Microstructure and functional group analysis of BCF was performed by SEM, XRD, and FTIR showing intercalation of FNPs with surface functionalities of oxidized BC matrix. The B-H curve of FNPs and BCF reveals super paramagnetic behavior with saturation magnetization (Ms, emu/g) of 67.36 and 20.01 respectively. BET surface area analysis shows surface area (m2/gm) 45.81 and 44.19 for oxidized BC and BCF respectively, that attributed to partial blocking of porous carbon matrix by FNPs. UV-DRS supports the semiconducting behavior of BCF with a significantly reduced band gap (eV) of 2.95 over pristine BC (4.76). BCF-coated photocatalytic plates (PCPs) were developed and utilized for the remediation of methyl orange (MeO) in water samples. Degradation of MeO was investigated over time by electrochemical methods. The square wave voltammetric method showed the limit of detection and quantification of 0.09 ppm and 0.28 ppm respectively for MeO over a glassy carbon electrode in 0.1 M acetate buffer. BCF-derived PCPs rendered ∼99 % degradation efficiency against MeO (50 mgL−1) under UV radiation over 240 min. Developed PCPs demonstrate reusability up to 5 cycles without any further purification step and offer efficient degradation of MeO making them suitable for the treatment of water polluted with dyes.

Silver nanogranules-decorated ZnO hybrid nanostructures with enhanced UV photoresponses

Detecting low-power ultraviolet (UV) light is crucial for practical applications. However, 1D ZnO/Ag based photodetectors (PDs) suffer from high expenses and care due to special operating conditions, posing challenges in capturing weak light signals and response time. To overcome these limitations, we integrate ZnO nanostructures with localized surface plasmon resonance of Ag nanoparticles via a surfactant-free hydrothermal-assisted polyol method, resulting in a notable bandgap reduction. SEM analysis revealed roughly spherical nanostructures for pristine ZnO and a porous structure in ZnO@Ag, around 1.4 µm in size with small agglomerates. XRD patterns showed reduced ZnO diffraction peak intensities in ZnO@Ag, confirming their core-like ZnO morphology. The fabricated ZnO@Ag heterojunction PD on an FTO substrate resulted in notable enhancement of PD performance. The ZnO@Ag heterojunction PD demonstrated a rapid 1.77 s response time, a 0.64 s recovery time and a specific detectivity of 11×107 cmHz1/2W−1, indicating its potential for low-cost and sustainable optoelectronics.

Copper doping induced band structure and morphology transformation in CaTiO3 for textile dye photodegradation applications

Semiconductor metal oxides with a wide bandgap like CaTiO3 can be exploited into an efficient visible light photocatalyst via cation doping. The type of dopant and the site of doping is known to greatly influence the photocatalytic activity of a material. Based on the intricacies of the density functional theory electronic structure study, we delve into the optimization of one-pot solvothermal synthesis to obtain Cu doped CaTiO3 nanocuboids. Doping of copper not only resulted in change in the electronic structure of the material but also led to change in the morphology. The uneven nanostep architecture resulted in increase in the surface area of the catalyst, which led to more active sites for the adsorption of the dyes and subsequent degradation. The reduced band gap and decreased recombination of charge carriers made the copper doped calcium titanate an efficient photocatalyst for degradation of both cationic (99.7% degradation of MV dye in 120 minutes) and anionic (99.8% degradation of RB in 45 minutes) dyes.

Influence of Al doping on crystal structure, magnetic and optical properties of TiO2 compound

Recently, an attempt to search for the novel material which can be applicable for spintronics devices, has become a highly debated and intensively investigated field of study. Within the scope of this investigation, Ti1−xAlxO2 (0≤x≤0.12) polycrystalline samples were produced using the traditional solid-state reaction method, and their crystal structure, magnetic, and optical characteristics were investigated. Single rutile phase with tetragonal crystal structure of titanium oxide is seen from the X-ray diffraction patterns study. The variation in the lattice parameter elucidate that Al3+ ions successfully substitute the Ti4+ ions. The analyses of the optical characteristics reveals that the incorporation of Al into the TiO2 matrix leads to a reduction in the optical band gap. Investigation on magnetic characteristics showed that all Ti1−xAlxO2 compounds displayed room temperature ferromagnetic nature with 81Oe≤Hc≤930Oe. Hall effect measurements show that all doped samples display p-type conductivity while un-doped TiO2 exhibits n-type conductivity and with increasing Al-doping concentration, the hole carrier density rises.

Substituent Controlled Tunable Fluorescence from Green to Red and pH Stimuli‐Induced Reversible Fluorescence Switching in Triphenylamine–Quinoxaline Derivatives

A series of triphenylamine‐quinoxaline donor‐acceptor (bipolar) compounds (TPA‐QH, TPA‐QMe, TPA‐QCOOH and TPA‐QNO2) with different substituents were synthesized and investigated their fluorescence properties, including stimuli‐induced fluorescence responses in solution and the solid‐state. Single crystal structural analysis revealed non‐planar molecular conformation, substituent controlled intermolecular interactions and molecular packing in the crystal lattice. TPA‐QH, TPA‐QMe, TPA‐QCOOH and TPA‐QNO2 showed tunable solid‐state emission from green to red. TPA‐QH showed strong fluorescence at 487 nm (quantum yield (Φf) = 28.3%) whereas NO2 substituted TPA‐QNO2 exhibited relatively weak fluorescence at 610 nm (Φf = 4.3%). Density functional theoretical (DFT) calculations also indicated reduction of optical bandgap with substituting electron withdrawing group. The donor‐acceptor structure with intramolecular charge transfer (ICT) resulted solvent polarity dependent fluorescence tuning. The presence of acid responsive quinoxaline group was utilized to demonstrate pH‐responsive fluorescence switching and dual state fluorescence was utilized for fabricating rewritable fluorescent platform. Thus, the present study provides a structural insight to develop dual state emissive triphenylamine–quinoxaline based bipolar materials for optoelectronic applications.

Tailoring the properties of SnS thin films deposited at room temperature by varying the amount of complexing agent for enhanced photocatalytic activity

This work examines how the characteristics and photocatalytic efficacy of modified SILAR-deposited SnS thin films are affected by the addition of a complexing agent. Stannous chloride dihydrate and sodium sulphate were used as tin and sulphur sources, respectively, while triethanolamine (TEA) served as a complexing agent in film deposition. The modified SILAR method facilitated the formation of well-adhesive thin films on the glass substrate at room temperature. The formation of SnS was demonstrated using EDAX and XPS analysis. XRD analysis proved that all the films are polycrystalline in nature with an orthorhombic crystal structure. The presence of chlorine as an involuntary dopant was observed in all the films prepared with TEA. Optical studies employing UV–visible spectroscopy found that all of the films have good visible absorption, with bandgap values ranging from 1.58 eV to 2.2 eV. Even though the films were deposited at room temperature, all films exhibited good thermal stability as per TGA analysis. The introduction of TEA caused improvements in the adhesion of the film to the substrate, a decrease in the band gap, a change in the morphology and composition, and an increase in the crystallinity and crystallite size. Due to their suitable bandgap corresponding to the visible region, SnS thin films exhibited good photocatalytic efficiency in degrading various types of dyes. The SnS thin film catalyst reduced 97% of methylene blue in 90 min at room temperature without using any reducing agent. The LCMS analysis validated the photocatalytic degradation of dye, whereas the UV–visible spectroscopic analysis gave a quantitative measure of the degradation efficiency. The reduction in photodegradation efficiency in the presence of OH radical scavengers confirmed the role of OH radicals in the degradation process. The terephthalic acid test further demonstrated the generation of OH radicals during the dye degradation process. The observed increase in photocatalytic activity of SnS thin films with TEA addition could be due to TEA-induced bandgap reduction, crystallinity increase, and crystallite size increase. The catalyst was reusable, stable, easy to recover after use, and effective against various kinds of dyes. The study emphasizes the use of complexing agents as a useful tool for modifying the characteristics and, consequently, the photocatalytic efficiency of modified SILAR-deposited SnS thin films.

Unravelling Structural, Optical, and Band Alignment Properties of Mixed Pb-Sn Metal-Halide Quasi-2D Ruddlesden-Popper Perovskites.

Lead-tin (Pb-Sn) mixed-halide perovskites show potential for single-junction and tandem solar cells due to their adjustable band gaps, flexible composition, and superior environmental stability compared to three-dimensional (3D) perovskites. However, they have lower power conversion efficiencies. Understanding band alignment and charge carrier dynamics is essential for enhancing photovoltaic performance. In this view, herein we have prepared thin films of mixed Pb-Sn-based two dimensional (2D) Ruddlesden-Popper (RP) perovskites BA2FA(Pb1-xSnx)2I7 using a solution-based method. XRD study revealed the formation of orthorhombic phases for pristine (BA2FAPb2I7) and mixed Pb-Sn perovskite thin films. UV-vis analysis showed that different n = 2 and n = 3 phases are present in the pristine sample. In contrast, Pb-Sn-doped samples showed no signature of other phases with a prominent red-shift in the visible spectral region. Cyclic voltammetry showed peaks for electron transfers at the band edges. Additionally, electrochemical and optical band gap matching was observed, along with decreased peak intensity due to less reactant and altered electrolyte-perovskite interface stability. Density functional theory (DFT) calculations revealed that the reduced band gap is due to the alteration of electrostatic interactions and charge distribution within the lattice upon Sn substitution. Low-temperature PL analysis provided insights into charge carrier dynamics with Sn substitution and suggested the suppression of higher n phases and self-trapped excitons/carriers in mixed Pb-Sn quasi-2D RP perovskite thin films. This study sheds light on the electron transfer phenomena between TiO2 and SnO2 layers by estimating band offsets from valence band maximum (VBM) and conduction band minimum (CBM), which is crucial for future applications in fabricating stable and efficient 2D-Pb-Sn mixed perovskites for optoelectronic applications.

[formula omitted] magnetism engineering in the low-buckled hexagonal SiS monolayer: A first-principles study

In this work, vacancy- and doped-induced magnetism engineering is investigated to functionalize the non-magnetic low-buckled hexagonal silicon sulfide (SiS) monolayer. This monolayer is an indirect gap semiconductor two-dimensional (2D) material with an energy gap of 2.20(3.02) eV obtained from the PBE(HSE06)-based calculations. Creating a single Si vacancy leads to a significant magnetization of SiS monolayer with the feature-rich half-metallic nature. Herein, a total magnetic moment of 1.89 μB is obtained and magnetic properties are produced mainly by S and Si atoms closest to the defect site. In contrast, single S vacancy preserves the non-magnetic nature inducing a band gap reduction of the order of 26.36%. n-type doping with P atom metalizes the monolayer, meanwhile As impurity leads to the emergence of the half-metallicity with a total magnetic moment of 1.00 μB. Similarly, this value is also obtained by p-doping using P and As atoms as dopants, where the diluted magnetic semiconductor nature is obtained. Moreover, doping with IA- (Na and K) and IIIA-group (Al and Ga) atoms is also proposed to engineer the magnetism in SiS monolayer. It is found that these impurities induce either half-metallic or diluted magnetic semiconductor behaviors with total magnetic moment between 0.99 and 1.00 μB. The electronic and magnetic properties are regulated mainly by the interactions between impurities and their neighbor S atoms, which modify the charge distribution in their outermost orbitals. In addition, the Bader charge analysis asserts that dopant atoms gain charge from the host monolayer when substituting S atom, meanwhile they act as charge loser — transferring charge to the host monolayer when doping at Si sublattice. The presented results may suggest efficient approaches to properly engineer SiS monolayer electronic and magnetic properties, making new 2D candidates for spintronic applications.

Density Functional Theory Provides Insights into β-SnSe Monolayers as a Highly Sensitive and Recoverable Ozone Sensing Material.

This study explores the potential of β-SnSe monolayers as a promising material for ozone (O3) sensing using density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) method. The adsorption characteristics of O3 molecules on the β-SnSe monolayer surface were thoroughly investigated, including adsorption energy, band structure, density of states (DOSs), differential charge density, and Bader charge analysis. Post-adsorption, hybridization energy levels were introduced into the system, leading to a reduced band gap and increased electrical conductivity. A robust charge exchange between O3 and the β-SnSe monolayer was observed, indicative of chemisorption. Recovery time calculations also revealed that the β-SnSe monolayer could be reused after O3 adsorption. The sensitivity of the β-SnSe monolayer to O3 was quantitatively evaluated through current-voltage characteristic simulations, revealing an extraordinary sensitivity of 1817.57% at a bias voltage of 1.2 V. This sensitivity surpasses that of other two-dimensional materials such as graphene oxide. This comprehensive investigation demonstrates the exceptional potential of β-SnSe monolayers as a highly sensitive, recoverable, and environmentally friendly O3 sensing material.

Exploring the influence of fused heterocyclic donor moieties on optical nonlinearity of styrylthiophene based chromophores: A DFT study

A new series of styrylthiophene based NLO compounds was designed with D-π-A configuration for NLO materials. The DFT calculations of designed derivatives (CTMFD1–CTMFD6) were performed at M06/6-311G (d,p) functional. A reduction in band gap with bathochromic shift (λmax = 644.107–712.430 nm) was seen in all designed derivatives as compared to reference chromophore (ΔE = 2.458 and λmax = 586.907 nm) except for CTMFD1. In FMO analysis, energy band gaps of designed derivatives were found to be smaller (1.901–2.319, eV) except CTMFD1 (2.824 eV) comparative to CTMFR (2.458 eV). Among all other molecules, CTMFD1 and CTMFD2 compounds showed the higher βtot of 5.370 × 10–27 and 4.837 × 10–27esu, while CTMFD4 compound showed the lowest value at 1.629 × 10–27esu. In the case of second hyperpolarizability (γtot), comparing with other derivatives, the larger value of γtot has also been found in the CTMFD2 compound which is 4.514 × 10–33esu, suggesting potential prospects for the advancement of large NLO scaffolds.

Tuning Excitonic Properties of Monochalcogenides via Design of Janus Structures.

Two-dimensional (2D) Janus structures offer a unique range of properties as a result of their symmetry breaking, resulting from the distinct chemical composition on each side of the monolayers. Here, we report a theoretical investigation of 2D Janus Q'A'AQ P3m1 monochalcogenides from group IV (A and A' = Ge and Sn; Q, Q' = S and Se) and 2D non-Janus QAAQ P3̅m1 counterparts. Our theoretical framework is based on density functional theory calculations combined with maximally localized Wannier functions and tight-binding parametrization to evaluate the excitonic properties. The phonon band structures exhibit exclusively real (nonimaginary) branches for all materials. Particularly, SeGeSnS has greater energetic stability than its non-Janus counterparts, representing an outstanding energetic stability among the investigated materials. However, SGeSnS and SGeSnSe have higher formation energies than the already synthesized MoSSe, making them more challenging to grow than the other investigated structures. The electronic structure analysis demonstrates that materials with Janus structures exhibit band gaps wider than those of their non-Janus counterparts, with the absolute value of the band gap predominantly determined by the core rather than the surface composition. Moreover, exciton binding energies range from 0.20 to 0.37 eV, reducing band gap values in the range of 21% to 32%. Thus, excitonic effects influence the optoelectronic properties more than the point-inversion symmetry breaking inherent in the Janus structures; however, both features are necessary to enhance the interaction between the materials and sunlight. We also found anisotropic behavior of the absorption coefficient, which was attributed to the inherent structural asymmetry of the Janus materials.

Computational exploration of janus ZrMCO2 (M=Ti, hf) MXenes for optoelectronic and photocatalytic applications

MXenes exhibit unique structural flexibility, excellent carrier mobility and abundant active sites, making them valuable catalysts in photocatalysis. The electronic properties and photocatalytic activity of Janus ZrMCO2 (M = Ti, Hf) MXenes are investigated by hybrid HSE06 functional. Photocatalytic activities of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are further explored. Structural stability is proved by negative cohesive energy and elastic stiffness coefficients. ZrTiCO2 and ZrHfCO2 are all direct semiconductors. Ti/Hf doping makes conduction band minimum (CBM) have a redshift and induces the reduction of band gaps of Janus systems. The three systems are potential photocatalysts due to their appropriate bandgaps and significant absorption in visible region. The irradiation-generated holes and electrons can easily drive the HER or OER on ZrHfCO2 MXene due to the small overpotential. ZrHfCO2 and Zr2CO2 are highly efficient for photocatalytic hydrogen production with STH efficient of 30.3%. Hf doping improves the photocatalytic reduction of CO2, while The Ti/Hf doping doesn't improve the N2 reduction.

Photocatalytic degradation of antibiotics by N-doped carbon nanoflakes-nickel ferrite composite derived from algal biomass

This work reports the synthesis of nickel ferrite (NiFe) nanoparticles, N-doped mesoporous carbon nanoflakes (NCF) and novel nickel ferrite-carbon nanoflakes (NiFe@NCF) nanocomposite using solvothermal method. NCF was derived from a cyanobacterial consortium consisting of Anabaena, Lyngbya and Weistiellopsis, rich in carbon and nitrogen. The synthesized nanoparticles were used as heterogeneous photocatalyst for degradation of two harmful water pollutants, ciprofloxacin (CIP) and levofloxacin (LEV). 99.91% LEV and 98.86% CIP were degraded within 50 and 70 min of visible light irradiation using NiFe@NCF following pseudo first order kinetics. This improved efficiency of the nanocomposite may be attributed to its higher surface area, reduction of band gap (from 2.42 to 2.19 eV), more active sites as well as charge carrier mobility with decreasing agglomeration tendency of the magnetic nickel nanoparticles upon being embedded on NCF. N-doping improves light harvesting property, retards charge recombination and extends as well as delocalises ᴨ-conjugated system resulting in enhanced photocatalytic activity. The scavenging experiments and EPR analysis reveal that O2−• and •OH are the main active species taking part in the degradation process. The material performs well within a wide range of pH and can be effectively used up to 5 repetitive cycles. A feasible photocatalytic degradation mechanism of the antibiotics against NiFe@NCF nanocomposite is also put forwarded along with their possible degradation pathways from LCMS studies.

K2Ag(Ga/In)Br6 lead-free HDPs: Investigation of the elastic, optoelectronic, optical coating, and thermal characteristics for thermoelectric and solar cells

In this study, an investigation of the structural stability, elastic, optoelectronic, thermoelectric, optical thin-film coating, and thermodynamic properties of K2Ag(Ga/In)Br6 (lead-free halide double perovskites, HDPs) was performed using first-principles calculations. The optimized structural parameters are in good agreement with the available data. Furthermore, Goldsmith's tolerance factor indicates an ideal value for both double perovskites, ensuring the structural stability of the cubic perovskites, and the elasticity parameters were analyzed to ensure the mechanical stability of the cubic phase. Direct and reduced band gaps of 0.4524 eV and 1.064 eV with semiconductor behavior are found for K2AgGaBr6 and K2AgInBr6, respectively, through adoption of the modified Becke–Johnson potential scheme. The absorption coefficient, refractive index, and dielectric function, as some of the optical properties, in addition to the optical thin-film properties, are well discussed, and the values suggest that these materials are promising candidates for different devices, such as optoelectronic and photovoltaic energy devices. In terms of the thermodynamics, the HDPs display favorable characteristics across various temperature and pressure ranges. Additionally, we assessed the thermoelectric properties, considering the power factor, Seebeck coefficient, thermal and electronic conductivities, and figure of merit. The current predictions suggest that these lead-free halide double perovskites have strong potential for application in thermoelectricity and photovoltaics.

Harnessing Light and CO2 With Copper‐Nickel on TiO2 Photocatalysts for Methanol Production

AbstractThe contemporary focus on global concerns such as carbon dioxide (CO2) emissions impacting the environment and contributing to the energy crisis has prompted exploration into alternatives, with photocatalysis emerging as a potential solution. This research involved the development of a PT (TiO2) photocatalyst, synthesized through the hydrothermal method and enhanced with double co‐catalysts of copper and nickel via the wet impregnation technique. The characteristics of the resulting photocatalysts were comprehensively examined using various techniques, including XRD, Raman, UV‐Vis DRS, surface area and pore analysis, SEM‐EDX, HRTEM, XPS, PL, and EPR. The characterization outcomes revealed that the PT phase comprised anatase, brookite, and rutile. The incorporation of double co‐catalysts was evident through the emergence of new peaks in the XRD diffraction pattern, corroborated by SEM, HRTEM, and XPS analysis. In the activity test, CNT‐4 (Cu−Ni/TiO2‐400) exhibited the highest methanol yield at 772.41 μmole g−1 h−1, followed by CONTT‐4 (CuO−NiTiO3/TiO2‐400) with 750.38 μmole g−1 h−1 after three hours of irradiation using a 300 W xenon lamp, while methanol in PT formed only after three hours of irradiation. The presence of co‐catalysts significantly influenced methanol yield, attributed to the increased active sites for the reaction and the reduced band gap, impacting light absorption optimization and suppressing electron‐hole recombination. In CNT‐4, the formation of Ti3+ associated with oxygen vacancies facilitated the generation of more products.

Dilution of helical antiferromagnetic matrix of CaMn7O12 under nonmagnetic Ga[formula omitted] doping

The work reports dilution studies on antiferromagnetic CaMn7O12. Introduction of nonmagnetic ion in an antiferromagnetic matrix changes the magnetic properties in an interesting way. The study becomes significant due to the fact that remarkable increase in magnetization is observed as a result of substitution of a few of the magnetic Mn ions with the nonmagnetic Ga ion. For 5% doping of Ga, the magnetization value becomes nearly thrice of the un-doped CaMn7O12. A sequential decrease in antiferromagnetic ordering transition temperature is also observed with increasing Ga percentage in the parent compound. The solid solubility limit of Ga in the matrix is found to be nearly 5%, above which it start showing impurity peaks. Experimental results are well complemented with the Density functional theory (DFT) based calculations. Theoretical calculations are carried out on (CaMn7O12)3 unit cell with one Ga atom doped at different Mn sites resulting around 5% doping concentration. Besides identifying the most favourable doping site for Ga, results indicate a reduction of bulk band gap and significant increase in magnetization, both of which are in agreement with the experimental results.

Femtosecond nonlinear optical properties of Ti-doped In2Te3 thin films grown by magnetron co-sputtering

Herein, we successfully prepared Ti-doped In2Te3 and pure In2Te3 films by magnetron co-sputtering at room temperature. The film structure was measured using x-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS), while the linear optical constant of the films was measured using a spectroscopic ellipsometer (SE). The nonlinear optical properties of the films were examined using the Z-scan technique, wherein the samples were irradiated with 140 fs laser pulses at a wavelength of 800 nm and a repetition rate of 80 MHz, with an input intensity of 1.2GW/cm2. Ti incorporation led to decreased crystallinity and a reduction (redshift) in the optical bandgap (E g ). All films exhibit reverse saturation absorption (RSA) and self-focusing effect. A ninefold increase in the nonlinear refractive index (n2) and a fourfold increase in the nonlinear absorption coefficient (β) were observed for the Ti-doped S40 sample in comparison to the pure S0 sample. Adjusting the phase transition between amorphous and crystalline states in Ti-doped In2Te3 films further modulated their nonlinear optical properties. The optical limiting (OL) behavior of pure In2Te3 and Ti-doped In2Te3 thin films was investigated, and the results demonstrated that Ti-doped In2Te3 films show great promise as optical limiter devices in nonlinear photonics.

Study of Band Gap Reduction and Enhanced light Absorption in DSSC’s using N-TiO2 and Azo Dye Composites

This research delves into enhancing Dye-Sensitized Solar Cells (DSSCs) using Nitrogen added Titanium Dioxide (N-TiO2) nanoparticles. Nitrogen is employed to reduce TiO2's band gap, thereby enhancing its light absorption capabilities. Azo dyes namely VC, RP and RM are chosen as sensitizers due to their efficient light absorption properties. UV-spectrophotometer analysis reveals superior absorption and a lower band gap in N-added TiO2 compared to pure TiO2. Additionally composites of pure TiO2, N-added TiO2 with azo dyes taken in various proportion are explored. Energy band gap of each is calculated using UV- spectrophotometer analysis. Composites made using 8% N and TiO2 with azo dyes VC and RP taken in equal ratio showed the maximum absorption for a range of frequencies from 300nm to 900nm and thus leading to the minimum energy band gap.

First-Principles Investigation on the Tunable Electronic Structures and Photocatalytic Properties of AlN/Sc2CF2 and GaN/Sc2CF2 Heterostructures.

Heterostructure catalysts are highly anticipated in the field of photocatalytic water splitting. AlN/Sc2CF2 and GaN/Sc2CF2 heterostructures are proposed in this work, and the electronic structures were revealed with the first-principles method to explore their photocatalytic properties for water splitting. The results found that the thermodynamically stable AlN/Sc2CF2 and GaN/Sc2CF2 heterostructures are indirect semiconductors with reduced band gaps of 1.75 eV and 1.84 eV, respectively. These two heterostructures have been confirmed to have type-Ⅰ band alignments, with both VBM and CBM contributed to by the Sc2CF2 layer. AlN/Sc2CF2 and GaN/Sc2CF2 heterostructures exhibit the potential for photocatalytic water splitting as their VBM and CBM stride over the redox potential of water. Gibbs free energy changes in HER occurring on AlN/Sc2CF2 and GaN/Sc2CF2 heterostructures are as low as -0.31 eV and -0.59 eV, respectively. The Gibbs free energy change in HER on the AlN (GaN) layer is much lower than that on the Sc2CF2 surface, owing to the stronger adsorption of H on AlN (GaN). The AlN/Sc2CF2 and GaN/Sc2CF2 heterostructures possess significant improvements in absorption range and intensity compared to monolayered AlN, GaN, and Sc2CF2. In addition, the band gaps, edge positions, and absorption properties of AlN/Sc2CF2 and GaN/Sc2CF2 heterostructures can be effectively tuned with strains. All the results indicate that AlN/Sc2CF2 and GaN/Sc2CF2 heterostructures are suitable catalysts for photocatalytic water splitting.