High Band Gap Values Research Articles

New Silver(I) Complexes as Achromatic Sensitizers in Solar Cell Applications

ABSTRACTThe design, synthesis, and spectroscopic characterization of [Ag(P(o‐C6H4OCH3)3)(NO3)]2 (1) and [Ag(P(o‐C6H4OCH3)3)2][NO3] (2) were conducted to investigate the efficiency of the fabricated solar cell devices. The slow evaporation technique proved effective in growing the colorless crystals of the silver(I) complexes. Spectroscopic analyses including Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and ultraviolet–visible (UV–Vis) studies were carried out to elucidate the chemical structure and absorption properties of the compounds. The chemical composition and existence of intermolecular interactions in 1 and 2 were disclosed via the single‐crystal x‐ray diffraction method. The side‐to‐side arrangement of molecules in 1 and 2 was evident from the crystal packing analysis, in which the molecules in both compounds were linked together by C–H···O and C–H···π contacts. The silver(I) complexes exhibited maximum absorption wavelength (287–288 nm) within the ultraviolet region, where both compounds had comparable high energy band gap values ranging from 4.15 to 4.16 eV. Moreover, both compounds possess appropriate HOMO–LUMO energy levels that facilitate effective electron injection and dye regeneration processes in dye‐sensitized solar cell (DSSC) applications. Photophysical characterization techniques, field‐emission scanning electron microscopy (FESEM), and energy‐dispersive x‐ray (EDX) spectroscopy studies were employed to assess the morphological characteristics and elemental composition of the silver(I) complexes on TiO2. Compound 2 exceeded 1 in terms of solar cell efficiency, 2 (η = 3.34%) > 1 (η = 0.66%) due to the complex being in ionic form and composed of the mononuclear [Ag(P(o‐C6H4OCH3)3)2]+ cation [NO3]− anion.

Effects of Rapid Heat Treatments on the Properties of Cu2O Thin Films Deposited at Room Temperature Using an Ammonia-Free SILAR Technique

We report herein the analysis of the properties of copper(I) oxide thin films deposited by an optimized ammonium-free successive ion layer adsorption and reaction (SILAR) technique. The Cu2O thin film deposition process was carried out at room temperature using copper acetate monohydrate, sodium citrate as complexing agent, and hydrogen peroxide as precursors of copper and oxygen ions, respectively. The harmless and easy-to-handle sodium citrate replaces the volatile NH4OH commonly employed as complexing agent in the SILAR technique for the deposition of metal oxide thin films. The optical, structural, morphological, and electrical properties of the as-deposited Cu2O thin films were studied as a function of the number of cycles during deposition, as well as their modifications produced by the effect of rapid thermal annealing (RTA) in vacuum in a temperature range of 200–250°C for 1 min, 3 min, and 5 min. The as-deposited thin films had cubic crystalline structure corresponding to the Cu2O phase as determined by x-ray diffraction (XRD), with a direct energy bandgap of 2.43–2.51 eV depending on the number of cycles, and electrical resistivity of the order of 103 Ω cm. The XRD and x-ray photoelectron spectroscopy (XPS) analysis of the Cu2O thin films treated by RTA demonstrated an increase of the crystal size with time and temperature of the RTA and reduction effects from Cu2+ to Cu1+ oxidation states. On the other hand, the RTA treatments also decreased their energy bandgap to 2.38 eV and electrical resistivity to 102 Ω cm. The high energy bandgap values of the Cu2O thin films were attributed to quantum confinement effects produced by their small crystal size in the range of 3.6–8.6 nm.Graphical

Application of Bi0.5Na0.5TiO3 −based catalysts for piezocatalytic, photocatalytic and piezo-photocatalytic degradation of organic pollutants in wastewater remediation

In order to attain visible light driven piezo-photocatalyst for treatment of organic pollutants, Ag doped Bi0.5Na0.5TiO3 particles (Bi0.5Na0.5-x AgxTiO3 particles with x = 0, 0.01, 0.03, and 0.05) have been synthesised via sol–gel route. X-ray diffraction (XRD) study confirmed the monoclinic phase structure with Cc space group for all compositions. The Rietveld refinement using FullPROF program was performed to ensure the phase purity of the samples. The structure is reconfirmed by matching vibrational modes in Raman spectra as well. Morphological and elemental analysis were done using scanning electron microscopy (SEM) equipped energy dispersive x-ray spectra (EDX) and found the particle size ranging from 300-400 nm. UV–vis absorbance spectra were employed to find the optical bandgap for all synthesised particles, found in the range of 3.65–2.63 eV. The best piezo-photocatalytic activity found for sample x = 0.01 tested for rhodamine B dye, which is ∼ 82 % in 80 min under the exposure of UV light and mechanical disturbances, whereas degradation was ∼ 52.4 % and ∼ 22.7 % for photo- and piezocatalysis, respectively. Kinetics study and rate constant values were found using first order rate kinetics equation. Trapping experiment and stability test for the catalysts were done systematically, finding that hydroxyl and superoxide radicals are major active species and ∼ 9 % decrement in degradation capacity over three cycles were found due to loss of catalyst amount. The improvement in degradation is attributed to least recombination rate, greater oxygen vacancies, high degradation yield, high absorption capacity and optimum bandgap values over the other compositions. Therefore, 1 % Ag doped BNT sample can be novel efficient piezo-photocatalyst for treatment of organic dyes.

Application of Two-dimensional P-type ZnO Powder Illuminated By Visible Light for the Inhibition of Gram-positive and Gram-negative Bacteria in Water

Bacteria affect food quality in developing countries by spreading through contaminated soils and water. Antibiotics are used indiscriminately to eliminate Gram-positive and Gram-negative bacteria, with varying degrees of success. The use of nanomaterials with bactericidal properties can minimize the overuse of antibiotics. In this study, a two-dimensional p-type ZnO powder was successfully synthesized and its bactericidal properties were demonstrated. The XRD and Raman spectroscopy results indicated the presence of wurtzite-phase ZnO with Oi as the predominant native defect, resulting in p-type conductivity. SEM analysis confirmed the two-dimensional morphology, and optoelectronic characterization revealed a bandgap of 3.17 eV. Despite this high bandgap value, a plasmonic effect was generated on the surface of two-dimensional ZnO, which enhanced its bactericidal properties when the powders were in contact with bacteria. From an initial colony level of 5.5 × 105 CFU/mL, a significant decrease in the number of Gram-positive bacteria to 1.15 × 105 CFU/mL was observed, whereas the number of Gram-negative bacteria slightly increased to 1.45 × 106 CFU/mL. The observed inhibition rates were higher than those achieved with the broad-spectrum antibiotic, as validated in this study. The use of two-dimensional ZnO may provide a sustainable solution for the eradication of waterborne pathogens using visible light alone.

Computational studies into the chemical nature, thermal behaviour, solvent role, reactivity and biological evaluation of Rigidin E – A marine alkaloid with potent liver cancer inhibition

The current work includes theoretical studies of Rigidin E (marine alkaloid) molecule with the DFT technique and evaluation of its biological properties in silico. DFT calculations in different media were performed for the title molecule. Gradual changes were noticed in the properties of the title compound when subjected to solvation in polar solvents. Electron density distribution, interaction and excitation were demonstrated using topological studies (ELF, LOL, RDG, and charge transfer) done using Multiwfn software. From FMO analysis, methanol is the solvent in which the title compound has the highest band gap value (3.8972 eV) compared to other solvents, and in the gas phase it has a band gap value of 3.6886 eV. Theoretical UV studies show that n -->π* and n -->σ* electronic transitions are significant in Rigidin E. In water, the title molecule has a first-order hyperpolarizability about 100 times that of the reference substance urea, indicating its powerful NLO potential in aqueous medium. ADMET profile was generated using online tools (ADMET lab 2.0, PreADMET, and SwissADME). For the title molecule, docking was done against select liver cancer targets using AutoDock Tools and the lowest binding affinity was obtained −4.62 kcal/mol against 4H6J protein.

A hBN/B-Si-Al-O-glass composite coating growth on SiCp/Al composite using one-step PEO with nanoparticle addition for outstanding electrical insulation performance

A comprehensive study of the formation of electrical insulation coatings on SiCp/Al composite using plasma electrolytic oxidation (PEO) in an electrolytic system with hBN nanoparticles has been carried out. A complete coating can be formed under a high positive voltage (550–600 V) in a short period of time (3 min), and the coating is mainly composed of the hBN crystal phase as well as some amorphous phases. The high temperature of the local plasma in the PEO process impels these amorphous phases to form an amorphous B-Si-Al-O glass phase. As the treatment time goes on, the cross-sectional porosity of the coating first decreases rapidly and then increases slowly. This is attributed to the fact that the nanoparticles continuously deposit and sinter to repair the larger pores during the coating growth process, hence reducing porosity. Within 6 min, the coating thickness rapidly increases to 133.3 μm, showing excellent electrical insulation performance (with a breakdown voltage of 1460 ± 28 V, volume resistance of 5.52 ± 0.26 G·Ω, electrical resistivity of 4.18 × 1010 Ω∙cm) and high optical band gap value (above 5 eV), which is suitable for electronic packaging or dielectric materials.

Green synthesis of copper oxide nanoparticles using neem leaf extract (Azadirachta indica) for energy storage applications

ABSTRACT The green synthesis method was utilised in synthesising copper oxide nanoparticles from Azadirachta indica using copper sulphate as the precursor at different molarities. The nanoparticles were investigated using X-ray diffractometry (XRD), Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis spectrophotometry, and potentiometry to understand their respective structural, morphological, elemental, optical, and electrochemical properties. Crystalline diffraction peaks with nanospheres distributed through the surface. The elemental compositions of the as-deposited elements were confirmed from the EDX spectra. High optical absorbance and energy band gap values ranging from 1.75 eV to 2.72 eV at increasing molarities were obtained. Good cyclic voltammograms measured at a scan rate of 20 mV/s yielded a maximum specific capacitance of 148 F/g. The synthesised nanoparticles would find useful applications in supercapacitors and electrochemical devices.

Investigation of the optoelectronic and structural properties of FA(1−x)BixPbBr6I3 of perovskite mixed halide films

In this study, we analyzed the structural and optical characteristics of pure FAPbBr2I mixed halide perovskites and doped with a large proportion of bismuth. Previous work has demonstrated that the replacement of 2/3 of the iodine by bromine in the perovskite FAPbI3 limits its phase transition and thus increases its stability. However, this improvement in stability is accompanied by an increase in the band gap, from 1.45 to about 2 eV. It has been found that bismuth doping of certain perovskite materials makes it possible, in addition to increasing their stability, to significantly reduce their band gap, although certain authors still contest this phenomenon. Thus, we synthesized thin layers of perovskite FAPbBr2I doped with bismuth and studied the effect of this doping on the crystalline structure and the layers' optical characteristics thanks to analyses by X-ray diffraction, scanning electron microscopy and measurements of absorption and photoluminescence. The structural analysis results showed that bismuth diffuses very slowly into the crystal, resulting in a reduction in crystal size and a smoother surface. Moreover, measurements of the absorption coefficient revealed a significant reduction in the band gap, going from 2.08 eV with 0% bismuth to 1.45 eV with 20% bismuth. However, photoluminescence measurements gave much higher bandgap values. We believe that a phenomenon related to the addition of bismuth is responsible for this discrepancy.

DFT Insights into Noble Gold-Based Compound Li5AuP2: Effect of Pressure on Physical Properties.

In this study, the Li5AuP2 compound is investigated in detail due to the unique chemical properties of gold that are different from other metals. Pressure is applied to the compound from 0 to 25 GPa to reveal its structural, mechanical, electronic, and dynamical properties using density functional theory (DFT). Within this pressure range, the compound is optimized with a tetragonal crystal structure, making it mechanically and dynamically stable above 18 GPa and resulting in an increment of bulk, shear, and Young's moduli of Li5AuP2. Pressure application, furthermore, changes the brittle or ductile nature of the compound. The anisotropic elastic and sound wave velocities are visualized in three dimensions. The thermal properties of the Li5AuP2 compound are obtained, including enthalpy, free energy, entropy × T, heat capacity, and Debye temperature. The electronic properties of the Li5AuP2 compound are studied using the Perdew-Burke-Ernzerhof (PBE) and Heyd-Scuseria-Ernzerhof (HSE) functionals. The pressure increment is found to result in higher band gap values. The Mulliken and bond overlap populations are also determined to reveal the chemical nature of this compound. The optical properties, such as dielectric functions, refractive index, and energy loss function of the Li5AuP2 compound, are established in detail. To our knowledge, this is the first attempt to study this compound in such detail, thus, making the results obtained here beneficial for future studies related to the chemistry of gold.

Sol-Gel Synthesis of ZnO Nanoparticles Using Different Chitosan Sources: Effects on Antibacterial Activity and Photocatalytic Degradation of AZO Dye

Chitosan was used in the sol-gel synthesis of zinc oxide nanoparticles (ZnO NPs) as a capping agent in order to control the size, morphology, optical bandgap, photocatalytic efficiency, and antimicrobial activity. Different chitosan sources were used for the sol-gel synthesis of ZnO NPs, namely chitosan of shrimp shells, crab shells, and Streptomyces griseus bacteria. The photocatalytic efficiency was studied by using the methylene blue (MB) photodegradation test, and the antibacterial activity of the different types of ZnO NPs was investigated by the agar well diffusion technique. The particle size of ZnO NPs varied between 20 and 80 nm, and the band gap energy ranged between 2.7 and 3.2 eV. Due to the different chitosan sources, the ZnO NPs showed different antibacterial activity against Listeria innocua, Bacillus Subtiliis, Staphylococcus Aureus, Salmonella Typhimurium and Pseudomonas Aeruginosa. The ZnO NPs with lower band gap values showed better antibacterial results compared to ZnO NPs with higher band gap values. The MB dye removal of ZnO (shrimp shells), ZnO (crab shells), and ZnO (Streptomyces griseus) reached 60%, 56%, and 44%, respectively, at a contact time of 60 min, a low initial MB dye concentration of 6 × 10−5 M, a solution temperature of 25 °C, and a pH = 7.

Large energy mode-locked phenomenon based on ZrS2 in Er-doped fiber laser

With high nonlinear effect and low band gap value, ZrS2 is a promising material in photovoltaic application. In our work, a ZrS2-polyvinyl alcohol thin film modulator was successfully prepared by liquid phase exfoliation. The modulation depth of ZrS2 saturable absorber is 6.3 % and its saturation intensity is 3.92 MW/cm2. Large energy mode-locked phenomenon was obtained in the Er-doped fiber laser with ZrS2 as an optical modulator. When the pump power was 1250 mW, the center wavelength, pulse repetition rate, and maximum pulse energy of the large energy mode-locked were 1531 nm, 604.23 kHz, and 23.65 nJ, respectively. This experiment proves that ZrS2 has excellent nonlinear absorption performance, also provides a reference for the future research of large energy mode-locked based on transition metal dihalogenateds.

Enhancement of dysprosium oxide doped zinc alumino borosilicate glasses in thermal, optical and luminescence domain for solid state lighting application

Zinc alumino borosilicate (ZABS) glasses incorporated with Dy3+ ions are prepared through melt-quenching technique. Non-crystallinity behaviour of the glasses are confirmed through XRD studies. The presence of functional and vibrational groups in the glass network are witnessed through FTIR studies. From the differential thermal analysis (DTA), the thermal stability of the glasses are found to be greater than 90 °C. UV–Visible–NIR spectra of glasses showed strong absorptions of Dy3+ ions in the NIR region (∼1267 nm). The highest bandgap value is obtained for ZABSDy0.5 (4.27 eV) glass that has the lowest amount of non-bridging oxygens. The ionic nature of dysprosium ions in the glass vicinity is thereby known through bonding parameter calculation. Judd-Ofelt (J-O) intensity parameters showed the trend Ω2 > Ω6 > Ω4, maintained same for all synthesized glasses. The luminescence spectra showed three emission peaks of Dy3+ ions at 482 (6H15/2), 575 (6H13/2) and 663 (6H11/2) nm. The hypersensitive transition observed at 4F9/2 → 6H13/2 exhibits a greater emission cross-section and radiative transition for all the glasses. Through the decay measurements, the lifetime of the Dy3+ ions are calculated. The estimated CIE coordinates for the glasses showed their location in white light region. The correlated colour temperature (CCT) values are obtained between 4200 and 4500 K suggesting the importance of glasses to use for white-LEDs application.

Facile fabrication of SnO2 / MoS2 / rGO ternary composite for solar light-mediated photocatalysis for water remediation

Tin oxide (SnO2) nanostructure has potential application for the removal of organic contaminants from industrial effluents. However, higher bandgap value (3.8 eV and fast recombination of charge carriers (e- - h+ pair)) have limited its applications. To overcome these limitations, we have proposed a double Z-scheme strategy, which not only reduced the rate of recombination but lso provides a new pathway for charge carriers to degrade the organic toxins. SnO2 surface sensitization with MoS2 nanofibers by hydrothermal method followed by composite formation with reduced graphene oxide (rGO) via ultrasonication was employed as photocatalyst for methylene blue (MB) degradation. The surface sensitized SnO2 with MoS2 and its composite with rGO were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-rays (EDX), and ultraviolet-visible (UV-Vis.) spectroscopy. XRD analysis revealed that SnO /MoS2 heterostructure has very small crystallite. From UV-visible studies, a redshift was observed for the SnO2 /MoS2 heterostructure as compared to SnO2, which further extends to the visible spectrum with the introduction of reduced graphene oxide (rGO). The photocatalytic studies revealed that SnO2 /MoS2 /rGO composite significantly improved the photocatalytic efficiency up to 90% under 75 min in the presence of solar light. EIS measurements exhibited that SnO2/MoS2/rGO has better charge transfer and mass transfer potential as compared to SnO2.

Highly efficient and simultaneous catalytic reduction of multiple toxic dyes and nitrophenols waste water using highly active bimetallic PdO\u2013NiO nanocomposite

Azo dyes and nitrophenols have been widely used in the various industry which are highly toxic and affecting the photosynthetic cycle of aquatic organism. The industry disposals increase the accumulation of azo compounds in the environment. In the present study, we synthesized the low cost, PdO-doped NiO hetero-mixture via simple hydrothermal combined calcination process. The morphology results proved that, the spherical PdO nanoparticles are evenly doped with NiO nanoparticles. The band gap values of metal oxides NiO, PdO and PdO–NiO composite were found to be 4.05 eV, 3.84 eV and 4.24 eV, respectively. The high optical bandgap (Eg) value for composite suggests that the PdO interface and NiO interface are closely combined in the composite. The catalytic activity of the PdO–NiO was analyzed for the reduction of different toxic azo compounds namely, 4-nitrophenol (NP), 2,4-dinitrophenol (DNP), 2,4,6-trinitrophenol (TNP), methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) separately and their mixture with the presence of a NaBH4. For the first time, the large volume of the toxic azo compounds was reduced into non-toxic compounds with high reduction rate. The proposed PdO–NiO catalyst exhibit excellent rate constant 0.1667, 0.0997, 0.0686 min−1 for NP, DNP and TNT and 0.099, 0.0416 and 0.0896 min−1 for MB, RhB and MO dyes respectively which is higher rate constant than the previously reported catalysts. Mainly, PdO–NiO completes the reduction of mixture of azo compounds within 8 min. Further, PdO–NiO exhibit stable reduction rate of azo compounds over five cycles with no significant loss. Hence, the proposed low cost and high efficient PdO–NiO catalyst could be the promising catalyst for degradation of azo compounds.

Optimization of different temperature annealed nanostructured CdSe thin film for photodetector applications

In this work, the photo sensing performance of the highly sensitive CdSe-based photodetector prepared using thermal evaporation method on a cleaned glass substrate were analyzed. At various temperatures, the effect of post-annealing on the crystalline, morphological, optical, and photo-electrical properties was examined. X-ray diffraction (XRD) and Raman experiments confirmed the polycrystalline nature of the CdSe films. From the field emission scanning electron microscopy (FESEM), it was observed that there were changes in surface morphology and grain size of the films. Energy dispersive X-ray spectroscopy (EDS) confirms the presence of constituent elements such as Cd and Se in the deposited films. The UV–Visible measurement was used to evaluate the change in several optical properties of the examined films, such as bandgap (Eg), absorption & extinction coefficient (α &k) and refractive index (n). Importantly, varying annealing temperatures resulted in lower and higher bandgap values. The photo-response and optical properties of the annealed CdSe film at 300 °C were good, making it suitable for the application of photodetectors.

Structural, micro-structural, optical and dielectric behavior of mullite ceramics

Mullite ceramics of two different compositions Al0·60Si0·40O and Al0·75Si0·25O have been synthesized by pyrophoric method followed by reaction sintering at 1050°C. The structural, micro-structural, optical, and dielectric characterization of mullite has been carried out through XRD, Raman, SEM, UV–Visible and dielectric studies. In this work, the synthesized mullite materials possess quite high dielectric constant value with negligible dielectric loss factor. The room temperature dielectric constant values for Al0·60Si0·40O and Al0·75Si0·25O stoichiometric mullites are found to be 110 and 2665 with a loss factor of 2.04 and 2.29 at 100 Hz frequency, which is comparatively high than the corresponding values of dielectric constants reported in previous literatures of mullite. The dielectric constant values for both the ceramics are very high (>104) for temperatures greater than 250°C. The room temperature dielectric constant (6.03 and 5.08, at 1 MHz), dielectric loss (0.07 and 0.05, at 1 MHz), electrical conductivity (1.5 × 10−5 S/m and 8.1 × 10−6 S/m, at 300 °C) results for Al0·60Si0·40O and Al0·75Si0·25O prove these ceramics suitable for electronics-related applications. The Arrhenius type conductivity, non-Debye type relaxation mechanism is confirmed from AC conductivity, complex impedance, and modulus study of these ceramics. These ceramics possess high optical band gap values of 3.46 eV and 3.36 eV for Al0·60Si0·40O and Al0·75Si0·25O, respectively which is suitable for using as electronic circuit packaging material or as a dielectric substrate material for any kind of storage devices.

A DFT study on the electronic structure of in-plane heterojunctions of graphene and hexagonal boron nitride nanoribbons

The structural similarity between hexagonal boron nitride (h-BN) and graphene nanoribbons allows forming heterojunctions with small chain stress. The insulation nature of the former and the quasi-metallic property of the latter make them attractive for flat optoelectronics. Recently, shapes of graphene and h-BN domains were precisely controlled, creating sharp graphene/h-BN interfaces. Here, we investigated the electronic and structural properties of graphene (h-BN) nanoribbon domains of different sizes sandwiched between h-BN (graphene) nanoribbons forming in-plane heterojunctions. Different domain sizes for the non-passivated zigzag edge termination were studied. Results showed that the charge density is localized in the edge of the heterojunctions, regardless of the domain size. The systems with graphene domains are metallic, presenting null band gaps. The ones with the h-BN island are small-bandgap semiconductors with the highest bandgap value around 0.2 eV. The calculated bandgap has the same magnitude of the certain threshold for density functional theory. As a general trend, these materials exhibit a ferromagnetic behavior, which can be useful for magnetic applications at the nanoscale.

Simultaneous introduction of 0D Bi nanodots and oxygen vacancies onto 1D Bi6Mo2O15 sub-microwires for synergistically enhanced photocatalysis

Bi6Mo2O15 is a promising photocatalyst toward environmental remediation due to its high ionic conductivity. However, the high band gap value and fast charge recombination rate limit its photocatalytic efficiency. To tackle these issues, we prepared 1D Bi6Mo2O15 sub-microwires by a molten salt-assisted synthesis approach. Then the as-synthesized photocatalysts were further modified through a facile chemical reduction treatment to introduce 0D Bi nanodots and oxygen vacancies (OVs). Due to the synergistic effects of the surface plasmon resonance (SPR) effect of Bi and the formation of OVs, the Bi deposited Bi6Mo2O15 (B-BMO) heterojunctions manifested excellent photocatalytic performance for tetracycline (TC) degradation. Under visible-light illumination, the 3% B-BMO (3% meant the mass ratio of NaBH4 and Bi6Mo2O15 was 3:100) presented a highest TC degradation efficiency of 98%, much higher than that of the pristine Bi6Mo2O15 (13.4%). Moreover, the possible TC degradation pathways were established based on the identification of degradation products by HPLC-MS/MS. This study provides new insights into the rational design and development of other bismuth-based photocatalysts with superior photocatalytic performance for environmental applications.

Solar-Driven Hydrogen Generation by Metal Halide Perovskites: Materials, Approaches, and Mechanistic View.

Solar-driven photocatalysis by metal halide perovskites (MHPs) is emerging as an exciting and promising field to promote several relevant catalytic reactions taking advantage of the superior optical properties of MHPs. Their electronic structure is suitable to run reduction reactions (H2 generation, CO2 reduction) and even oxidation reactions, in particualr for perovskites with higher band gap values, and further extends their possible use in the field of photochemical organic syntheses. This Mini-Review focuses on the application of MHPs in the solar-driven hydrogen generation with particular emphasis on the materials’ design and mechanistic features involved in the catalytic reactions.

Synthesis and study of structural, optical, and electrical properties of nontoxic and earth-abundant Na2ZnSnS4 material

In this work, we report the structural, electrical, and optical properties of nontoxic and earth-abundant Na2ZnSnS4 (NZTS) material. NZTS powder has been successfully synthesized using an easy and nontoxic pathway: the solid-state reaction technique. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy were used to study the structural properties of the NZTS. The synthesized powder crystallized in the stannite tetragonal structure with lattice parameters a = 6.48 A and c = 9.12 A. XRD and Raman characterizations showed the occurrence of the secondary phase Na4SnS4. Optical bandgap measurements were obtained from UV–Visible analysis and showed a high optical bandgap value of 3.32 eV and confirmed the presence of Na4SnS4. TEM micrographs provide a description of the morphology of NZTS. The HRTEM images reflect a preferred orientation along the {112} plane, which is consistent with the X-ray diffraction pattern. EDS analysis confirmed the presence of the four constituent elements of the NZTS within their corresponding composition. NZTS powder indicates a conductivity type n. A study of electrical conductivity was carried out by using the impedance spectroscopy. The frequency and temperature dependence of the complex electrical impedance and AC and DC conductivity were explored. These interesting results make the NZTS particularly attractive for solar cell applications and especially suitable as a window layer.