UV Vis NIR Research Articles

Theoretical DFT and experimental investigation of the effect of Co doping in electrochemically deposited ZnSe films

In this study, we examine the impact of introducing cobalt doping on the morphological, structural, optical, and electronic properties of ZnSe thin films produced by electrodeposition at room temperature. Characterization techniques, including X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and UV–Vis–NIR spectroscopy, were employed to analyze structural, morphological, and optical features. The developed films display a consistent and even distribution of grains with a cubic structure, showcasing a preferred orientation along the (111) axis. The calculated crystal size was estimated to be around 80 nm. The elemental composition of the film aligns with the synthesized deposition of elements. The introduction of cobalt resulted in enhanced optical properties and reduced energy bandgaps in the films. Concurrently, theoretical studies using the FP-LAPW approach in density functional theory were conducted, focusing on structural, electronic, and optical properties of cobalt-doped ZnSe at different concentrations (2 %, 4 %, 6 %). Theoretical findings demonstrated a substantial decrease in the bandgap, aligning well with the experimentally determined value of 2.72 eV. This coherence between theoretical predictions and experimental observations highlights the effectiveness of cobalt doping in influencing the optical characteristics of ZnSe thin films.

Synthesis and characterizations of zinc oxide nanorods by cost effective aqueous hydrothermal technique for solid state lighting applications

Zinc oxide (ZnO) is recognized as the most promising and often utilized semiconducting material due to its exceptional physical, chemical, optical, and relatively low-cost production features, as well as its ecologically beneficial nature. ZnO is a prominent candidate owing to its wide band gap (3.37 eV at room temperature) as well as its high exciton binding energy (60 meV) for the next generation of ultraviolet and blue optoelectronic devices. This would be achieved through the development of hybrid heterostructured LED devices with low manufacturing costs by blending gallium nitride (GaN) with zinc oxide (ZnO), which serves as the most efficient opto-electronic device. Due to its high electron mobility, high transparency in the visible wavelength spectrum, and low work function, ZnO is also a highly investigated transparent conducting oxide thin film for several applications. Besides, their incredible optical capabilities, ZnO-based optical devices, such as light-emitting diodes (LEDs) and laser diodes (LDs), have drawn a great deal of interest. This reported research work demonstrates the growth of high-density, high-aspect-ratio ZnO nanorod (NR) arrays on p-type gallium nitride substrates employing low-cost facial aqueous hydrothermal syntheses with optimised growing conditions. Additionally, a top-down chemical etching technique is adapted for fabricating zinc oxide nanotubes. High-quality ZnO nanorods with high intensity that were a few microns long were found across the GaN substrate with FESEM analysis. The chemical composition of the grown nanorods is confirmed with EDAX analysis. The wurtzite crystalline structure and c-axis orientation of the grown ZnO NR-arrays were identified in X-ray diffraction studies. A Schimadzu UV–Vis–NIR spectrophotometer was used to record the optical curve, and the energy gap was determined to be 3.24 eV by plotting the Tauc curve. The good optical quality of the harvested nanorods is ensured by the narrow near-band-edge (NBE) emission at 384 nm and defect emission peaks detected through photoluminescence analyses. Grown specimens are also subjected to Raman spectrum analyses, and the obtained results are presented.

Wet-chemical synthesis and luminescence studies of nano-crystalline gadolinium gallium garnet

Abstract This paper reports the photoluminescence studies of pure polycrystalline nano-sized gadolinium gallium garnet (Gd3Ga5O12, GGG) powders synthesized by the method of co-precipitation using ammonium hydrogen carbonate (NH4HCO3, AHC) as the precipitant. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, ultraviolet, visible, near-infrared (UV–Vis–NIR) spectroscopy and photoluminescence studies. The X-ray diffraction analysis confirms the formation of cubic structure of gadolinium gallium garnet (Gd3Ga5O12). The average particle sizes are found to be in the range of approximately 19 nm–88 nm, for different calcining temperatures. The formation of gadolinium gallium garnet is also confirmed by Fourier transform infrared studies. Scanning electron microscopy image measurement confirms the formation of nanosized particles. The photoluminescence studies of the pure gadolinium gallium garnet sample shows emission peaks around at 441 nm for an excitation wavelength of 350 nm for the sample calcined at 1,100 °C.

Self‐Doped Mixed Ionic‐Electronic Conductors to Tune the Threshold Voltage and the Mode of Operation in Organic Electrochemical Transistors

AbstractOrganic mixed ionic‐electronic conductors with tunable doping, low threshold voltages, and air stability are crucial for bioelectronic applications. A homopolymer based on an alkoxy thiophene monomer and its copolymer with a thiophene carrying ethylene glycol side chains are synthesized and converted to self‐doped conjugated polyelectrolytes, P3HOTS‐TMA+, and P3HOTS‐TMA+‐co‐P3MEEET. The self‐doping occurs during the conversion to polyelectrolytes. Both polyelectrolytes show high electrical conductivity without any external dopants. UV–Vis–NIR spectroscopy and spectroelectrochemistry confirm excellent air stability of the doped state. In an organic electrochemical transistor (OECT), the P3HOTS‐TMA+ operates in depletion mode, while P3HOTS‐TMA+‐co‐P3MEEET exhibits accumulation mode of operation with low threshold voltage, both showing fast response times. On the other hand, the non‐doped homopolymer, P3MEEET, shows a high negative threshold voltage in accumulation mode. Thus, copolymerization with the self‐dopable monomer changes the mode of operation as well as the threshold voltage substantially. Ultraviolet photoelectron spectroscopy reveals a considerable reduction of the hole injection barrier for the self‐doped system P3HOTS‐TMA+. Mott‐Schottky analysis shows reduction in charge carrier concentration in the copolymer compared to the homopolymer. Thus, the copolymerization strategy with a self‐dopable monomer is an efficient tool for tuning the degree of doping leading to low threshold voltage in OECTs.

Surface DBD in moist air for nitrogen fixation: a comparative study of pulsed versus amplitude-modulated AC powered discharge

Surface DBD (SDBD) discharge maintained in moist air in the immediate vicinity of the water surface is an effective source of reactive species for the production of plasma-activated water (PAW). In this work, we investigated the water activation process for two different DBD energization methods; i.e. using periodic HV pulses with nanosecond risetimes and amplitude-modulated HV AC. We combined UV–vis–NIR ICCD spectroscopy with electrical characteristics to determine the basic characteristics of SDBD microfilaments. Formation of N2O5/NO2/N2O/H2O2/NO2 −/NO3 − species was followed and the production yields of species generated in PAW (H2O2/NO2 −/NO3 −) were determined in a flow-through reactor under well-defined and stable discharge conditions. Both energization methods reached comparable energy efficiencies of nitrogen fixation in the range of 1–6 g kWh−1 with minimal concentrations of H2O2 (10 s μM). However, the AC-powered SDBD produced mainly NO3 − with minimal NO2 − (1/10 of NO3 −), while in the case of pulsed SDBD the better-balanced NO2 −/NO3 − ratio was achieved.

Optical behaviour of magnetron sputtered nano-hilled TiN coatings

Cylindrical magnetron sputtered TiN thin films have been grown on glass (G) and quartz (Q) substrates to examine optical properties under two flow conditions: increasing nitrogen flow rate (1 → 35 sccm): (I) and decreasing nitrogen flow rate (35 → 1 sccm): (D). The optical properties of the film are characterized using UV–Vis-NiR spectroscopy, spectroscopic ellipsometry, and photoluminescence studies. Films deposited under both parameters exhibited excellent UV-restriction properties. Nano-hilled topography of the film contributed to multiple reflections and scattering of incident light on both quartz and glass specimens. Clustering of nano-particles in G(D) specimen increases the light interaction and absorption within the film leading to higher absorbance and lower transmittance properties compared to G(I). TiN-Quartz specimen displayed better UV absorbing properties compared to TiN-Glass as confirmed through ellipsometry studies. lack of phonon-related transitions in Tauc's plot indicated the involvement of direct allowed transitions.

Influence of choline chloride pH adjuster on physical and optical properties of CuInSe2 thin films by CBD

We concentrate on low-cost thin film solar cells with the help of choline chloride acting as a pH adjuster because copper ternary material compounds and their alloys have become more and more lavish over the past 20 years. Chemical Bath Deposition (CBD) is used to produce copper indium selenium (CuInSe2) thin films on glass substrates while a pH adjuster is present. The micro structural and elemental properties are studied using X-ray diffraction (XRD), Raman, Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDS). The optical studies of CuInSe2 thin films are done using a UV–Vis–NIR spectrometer. XRD and Raman spectra shows that the CIS thin films deposited in the sequence of Glass/In/Se/Cu2Se/Se (labeled as CISB) and annealed at 400 °C (CISB400) contains all the peaks corresponding to the chalcopyrite CuInSe2. From the EDS measurements it was noted that the selenium to metal ratio (Se/Cu + In) for all the samples changes with temperature. It is worth to note that the film thickness decreases with a decrease in the pH of choline chloride which results a change in the optical band gap of the films. The optical properties of these thin films are greatly influenced by adjusting pH and it gives better results for optoelectronic devices with a sustainable UV filter which absorbs more in ultraviolet vicinity. The energy gap (Eg) values of the CISB samples were determined and is found to be suitable for photovoltaic conversion process.

Fabrication and characteristics study of self‐powered and UV–Vis–NIR photodetector based on p‐NiO:Eu nanofibers

AbstractHeterojunctions formed between undoped and Eu‐doped NiO nanofibers (NFs) and n‐Si were fabricated by electrospinning the NiO:Eu NFs onto Si. Since the photoresponse of the Eu‐doped NiO‐containing device was better than the undoped one, the study focused on the doped NiO‐containing device. This was explained by the increase in electron kinetics in terms of the active role of Eu in bonding with the 4f orbitals and the s, d, and f states of NiO. Electro‐optical measurements of the NiO:Eu NFs/n‐Si heterojunction were performed in the visible region depending on the light intensity and in the UV and NIR regions for 10 mW/cm2 powers. It was observed that the device exhibits a good level of rectification properties and responds very well to all lights. At all three light sources, the heterojunction photodetector exhibited self‐powered behavior. Furthermore, for 10 mW/cm2 light intensity, the NiO:Eu NFs/n‐Si photodetector achieved R values of 1.84 A/W at 365 nm, 0.98 A/W at 395 nm, and 1.54 A/W at 850 nm, while it is 0.12 A/W for visible light. Besides, the device showed an external quantum efficiency of 625% and this was attributed to the photocurrent gain. In self‐driven mode, D* values have been determined as 3.0 × 1012 Jones, 2.6 × 1012 Jones, and 2.9 × 1012 Jones for 365, 395, and 850 nm, respectively. The performance of NiO under UV light was attributed to the absorption of NiO under UV light, as well as the very good excitation of (Eu3+) ions by UV light.

The figure of merit improvement of (Sn, Co)–ZnO sprayed thin films for optoelectronic applications

Nanocrystalline zinc oxide (ZnO) has garnered significant attention from researchers and industries due to its superior properties as an optoelectronic material, particularly in solar cells as a transparent electrode. Doping, especially with tin (Sn) and co-doping with tin and cobalt (Co), can refine its optoelectronic properties. In this manuscript, we report on the optoelectronic properties of undoped ZnO thin films, as well as those doped with Sn and/or Co, elaborated using a simple chemical pneumatic spray pyrolysis method on glass substrates. A 1 % Sn doping concentration was used, with Co doping concentrations of 0 %, 0.5 %, and 1 %. The effects of Sn and/or Co doping concentration on the structure, morphology, optical, and electrical properties of nanocrystalline ZnO were studied using X-ray diffractometer (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FESEM), UV–Vis–NIR spectroscopy and Hall effect measurements. All the films studied exhibit wurtzite ZnO structures with a predominant (002) orientation and no secondary phase, as confirmed by X-ray diffraction (XRD) analysis. The Raman spectroscopy also reveals the presence of a wurtzite structure in all the films. The FESEM images reveal the kind and concentration of the dopants significantly influenced the surface morphology of the films. The elemental analysis with energy dispersive X-ray analysis (EDS) analysis successfully detected the doping of Sn and Co. The analysis of UV–Vis spectroscopy provide that the optical band gap for the undoped ZnO film is 3.25 eV. This band gap increases upon doping and co-doping, reaching a peak value of 3.30 eV for the Sn:Co (1 %:0.5 %) co-doped ZnO film. The ZnO film shows an improvement in the electrical resistivity upon doping and co-doping with low resistivity value of 1.95 × 10−2 Ω cm for the film (1%Sn, 0.5 % Co)–ZnO. The highest figure of merit (FOM) achieved is 1.41 × 10−4 Ω−1 for a ZnO thin film co-doped with (1 % Sn, 0.5 % Co). The existence of (1 % Sn, 0.5 % Co) film with improved optical gap, low electrical resistivity and high FOM supports its use in transparent conductive oxide applications.

Synthesis, structure and characterization of two new silver-iron based phosphates AgFe2(PO4)2F(H2O)2 and Ag3Fe2(PO4)(HPO4)3

Two new silver-iron based phosphates AgFe2(PO4)2F(H2O)2 (1) with monoclinic P21/n and Ag3Fe2(PO4)(HPO4)3 (2) with triclinic P-1 were synthesized by a conventional hydrothermal method, featuring a dimer structure and a twisted honeycomb-like lattice, respectively. XPS and BVS (Bond Valence Sum) calculations indicated only Fe3+ ions in both compounds, while FT-IR spectra proved the presence of [H2O] in 1 and [OH] groups in 2. Solid-state UV–vis–NIR diffuse reflectance spectra suggested their wide optical band gaps of 2.31 eV and 1.94 eV, respectively. Magnetic measurements indicated that both compounds display a long-range antiferromagnetic ordering at low temperature, showing the change of magnetic entropy of 9.59 J mol−1 K−1 in 1 and that of 14.87 J mol−1 K−1 in 2, respectively.

Colouring mechanism and firing technology of white porcelain from the Sui Dynasty (581–618) from the Xiangzhou kiln, Anyang, China

The Xiangzhou kiln was one of the first significant kilns in China to fire white porcelain and as well as the earliest one to adopt the technique of Make-up clay. It plays a very important role in the history of Chinese ceramics. Here we utilize ten pieces of Sui (581–618) white porcelain from the Xiangzhou kiln as the research objects. The chemical composition, micro-morphology, firing temperature, firing atmosphere, micro-area composition and other characteristics of white porcelain glaze were tested by energy dispersive X-ray fluorescence spectroscopy (EDXRF), laser Raman spectroscopy (LRS), optical microscope (OM), thermal dilatometer (TD), focused ion beam scanning electron microscope combined with X-ray energy spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and spectrophotometer (UV–Vis–NIR). Finally, the firing technology and colouring mechanism of the Xiangzhou white porcelain are revealed. Our study demonstrates that the relatively high content of Fe2O3 and TiO2 in the white porcelain glaze of the Xiangzhou kiln results in a milky white glaze with a slight greenish tinge. The high content of CaO and K2O in the glaze and the almost entirely glass phase of glaze layer lead to the fine grain, good transparency and gloss. Most of the white porcelain of the Xiangzhou kiln is fired at high temperature under reducing atmosphere. The Xiangzhou kiln white porcelain glaze belongs to the crystalline glaze, glaze disorderly distribution of some calcium feldspar precipitation crystals and a very small amount of quartz, calcite residual crystals, glaze bubbles are larger, the distribution of relatively dispersed. The overall colour effect of the Xiangzhou kiln white porcelain results from the combined action of the chemical colour of the body and glaze, along with structural colour.

Gamma irradiated Er3+ ions doped Li2O–BaO–B2O3–P2O5 glasses: Structural, optical, and thermoluminescence glow curve analysis

Lithium barium borophosphate glasses doped with Er3+ rare earth ions are reported in terms of their physical, optical, structural, and thermoluminescence (TL) properties in this study. The melt quenching method was used to synthesize the glasses with varying concentration of the dopant (0.0, 0.2, 0.4 0.6, 0.8 and 1.0 mol%). A thorough analysis of physical characteristics, including their variation with erbium oxide, has been conducted. The amorphous phase of the as-quenched samples has been validated through X-ray diffraction patterns, while Fourier transform infrared spectroscopy confirmed the existence of different structural groups. UV–Vis–NIR spectroscopy at wavelengths ranging from 200 to 1100 nm has been utilized to investigate various optical properties. In the gamma dose range of 50 Gy to 10 kGy, the glass sample with 0.6 mol% of erbium concentration (LBPEr0.6) showed the maximum integrated TL intensity with an optimized heating rate of 5 °C/s and annealing temperature of 400 °C. The deconvolution of TL glow curves was done using the R-package “tgcd: Thermoluminescence Glow Curve Deconvolution" by employing the Kitis general order kinetics model. Chen's peak shape approach has been used to calculate the trapping parameters, including order of kinetics (b), shape factor (μg), frequency factor (s), and activation energy (E). The ideal thermoluminescence dosimeter characteristics showed that LBPEr0.6 glass has outstanding linearity, excellent sensitivity, minimal fading and good reproducibility over six cycles.

Structural, linear/nonlinear optical characteristics and radiation shielding effectiveness of Cu4O3/Cu2O dual-phase thin films: Influence of oxygen flow rate in reactive sputtering process

In the present work, we investigated the impact of oxygen flow rate on the structural, linear, and nonlinear optical characteristics while also evaluating the radiation shielding effectiveness during reactive radio frequency (rf) sputtering in the deposition of Cu4O3/Cu2O dual-phase thin films. Microstructural analysis revealed distinct changes with increased OFRs, switching from a Cu2O cubic structure phase to a Cu4O3 tetragonal structure phase. The XRD patterns revealed good crystallinity, and the crystallite size of the film reduced from 28 nm to 22 nm, and the microstrain exhibited an opposing trend as the oxygen flow rate increased. In contrast, investigating the optical properties of dual-phase Cu4O3 and Cu2O thin films using UV–Vis–NIR spectroscopy revealed intriguing trends in the absorbance spectra, absorption coefficient, and extension index. The apparent bandgap increases from 2.0 eV to 2.62 eV with increasing oxygen flow rates. In addition, nonlinear optical parameters, including the nonlinear refractive index n2 linear, nonlinear sensitivity (χ1 and χ3), and nonlinear absorption coefficient βc were calculated to demonstrate the applicability of these materials. The dual-phase structure of the films enhances their potential for effective radiation shielding. Our findings provide valuable insights into the design of properties of Cu4O3/Cu2O dual-phase thin films for applications ranging from photoelectric and nonlinear optical devices to radiation shielding effectiveness.

Anti-Corrosion SiOx-Doped DLC Coating for Raster Steel Linear Scales

In this study, we investigated the efficacy of SiOx-doped diamond-like carbon (DLC) films for enhancing the corrosion resistance of raster steel linear scales. The research work highlights the significant role of DLC film materials in enhancing corrosion resistance, making them a promising solution for various industrial applications. The Raman spectroscopy analysis of SiOx-doped DLC films, synthesized via a direct ion beam technique with HMDSO vapor, revealed prominent D and G bands characteristic of amorphous carbon materials, with a high degree of disorder indicated by an ID/IG ratio of 1.85. X-ray diffraction patterns confirmed the amorphous nature of the SiOx-doped DLC films and the minimal impact of the DLC deposition process on the underlying crystalline structure of steel. UV–Vis-NIR reflectance spectra of SiOx-doped DLC on stainless steel demonstrated improvements in the blue wavelength region compared to stainless steel with ripples alone, which is beneficial for applications utilizing blue light. Corrosion tests, including immersion in a 5% salt solution and salt spray testing, showed that SiOx-doped DLC-coated stainless steel exhibited superior corrosion resistance compared to uncoated steel, with no significant signs of corrosion observed after extended exposure. These findings underscore the potential of SiOx-doped DLC coatings to provide long-term corrosion protection and maintain the structural integrity and surface quality of steel components in harsh environments.

Impact on preferred orientation and crystal strain behavior of nanocrystal anatase-TiO2 by X-ray diffraction technique

The primary goal of this research outline is the conversion of titanium isopropoxide (TTIP) at 50.0 °C to form a high crystalline preferred oriented predominant (101) with a low crystal strain of 90.0 % anatase-TiO2 phase. With the interval of time, the peptizing agent (IP) reacts to an acidic aqueous medium and preferential growth of anatase-TiO2 has been identified. Exhaustive recombination in X-ray diffraction (XRD) analysis ensures the crystal strain, lattice volume, lattice parameters, d-spacing and crystallite size. UV–vis-NIR showed maximum absorption of 320.0 nm with 0.78 a.u. at blue shift for decreasing nano-size and smaller bandgap 3.0313 eV of larger dimensions anatase-TiO2. The preferred orientation also revealed by nanobeam diffraction (NBD) of TEM enables qualitative lattice type and highly crystal orientated predominant (101) plane 5.60 nm−1 in a diffraction pattern imposed on 200.0 kv parallel electron bean from LaB6 filament.

The Modeling of Concentrators for Solar Photovoltaic Systems

Concentrating photovoltaic (CPV) systems have emerged as a transformative technology that incorporates radiation concentrators into the photovoltaic system to enable radiation to be concentrated onto a receiver—the solar cells. Different concentrator configurations have different impacts on the performance of the solar photovoltaic system. This research work aims to analyze the impact of different concentrators, comparing and identifying the most efficient structures for capturing and concentrating solar energy. Aiming at a deep analysis and comparison among concentrators shapes, this research work presents a unique investigation and revision among different structures such as flat, triangular, LFR, and parabolic concentrators. Moreover, since, in the UV–visible–NIR region, metals’ reflectance varies with the incident wavelength, five metals were considered: aluminum, gold, platinum, copper, and silver. Additionally, the research focuses on studying the effects of parameters critical to the quality of the concentration on the power obtained and on the uniformity of the radiation distribution on the surface of the receiver, as well as on the number of solar rays that reach the receiver. The power on the receiver increases proportionally with the number of reflector concentrators in the system and their reflectance. For parabolic geometries, the optical efficiency is affected by the receiver’s shadow on the concentrator and, in the case of the LFR, by a non-ideal alignment of the reflectors in relation to the receiver. However, in parabolic concentrator geometries, uniformity is usually lower, since in these configurations, the radiation is focused on specific areas of the receiver, usually the central zone.

Structural, optical analysis, stress-strain, and dielectric properties of selenium oxide/LaFeO3/blend nanocomposites with tunable properties for optoelectronics and micro-supercapacitors

This work focuses on developing flexible nanocomposites by introducing two types of ceramic nanofillers into a biopolymeric blend for optoelectronic and energy-storing applications. Selenium oxide (SeO2) nanoparticles (NPs) and LaFeO3 NPs were prepared by hydrothermal and solid-state reactions, respectively, and incorporated into the polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) through the solution casting process. Transmission electron microscope and X-ray diffraction tests revealed the creation of hexagonal SeO2 and orthorhombic LaFeO3 NPs, with average sizes of 17 and 93 nm. The blend's degree of crystallinity was dependent on SeO2 NPs and LaFeO3 contents. The infrared absorption spectra revealed the interactions/complexation of the fillers with the blend reactive groups. The scan e-microscope (field emission mode) investigated the films' surface morphology and detected the elements they contain. LaFeO3/SeO2 content impacted stress-strain behavior, raised the tensile strength from 64 to 70.9 MPa, and dramatically lowered the strain at break and toughness. UV–vis-NIR measurements exhibited that the transmittance, extinction coefficient, and refractive index can be tuned by SeO2 and LaFeO3/SeO2 content. The direct (Eg.d)/indirect (Eg.id) band gaps were reduced from 5.25/4.9 eV to 4.95/4.7 eV. The dielectric parameters (constant, loss, energy density, and conductivity) were significantly increased after loading 5.0 wt% LaFeO3/SeO2. The dielectric moduli and Cole-Cole plots were also investigated. The structural modifications and enhancement of the optical features and dielectric parameters make the resulted samples the best candidates for optoelectronic devices and energy-storing applications such as sensors and supercapacitors.

Defects induced SnOx-TiO2 nanocomposite thin films for improved visible light driven photocatalysis and photoelectrochemical applications

Advanced oxidative removal of organic pollutants from water bodies using nanoparticles of metal oxide photocatalysts is a concurrent hot topic. In the present study, SnOx-TiO2 heterogeneous nanocomposite thin film photocatalysts have been synthesized using SnO and TiO2 precursors by binder-free doctor blade technique. X-ray diffraction was used to confirm the presence of anatase TiO2 as a major phase at elevated temperatures. Raman spectra analysis confirmed phase transformation and defect induction. X-ray photoelectron spectroscopy was utilized to determine the purity and chemical condition of the synthesized thin films. The porous nature of the thin film surface was observed using field emission scanning electron microscopy. UV–Vis-NIR spectroscopy results showed a reduction of bandgap from 3 eV to 2.6 eV with enhanced light absorption. The superior oxygen evolution reaction, redox nature and charge carrier generation were demonstrated using photo-electrochemical techniques. Improved photoresponse of the photocatalysts was observed using chrono-amperometry technique. The superior visible light-driven photocatalytic activity of the samples was demonstrated utilizing cationic and anionic model pollutant dyes. The reusability of the catalyst is ensured through successive photodecomposition processes. These results show a facile fabrication of defects induced heterogenous nanocomposite photocatalyst thin films with improved visible light activity.

Optical properties of NiO films: Effect of nitrogen-doping, substrate temperature and band gap estimation using machine learning

In this study, nickel oxide (NiO) thin films were synthesized on glass substrates using RF magnetron sputtering with varying nitrogen (N) doping ratio and substrate temperatures to explore modifications in their structural, morphological, and optical properties. The films were prepared using a high-purity NiO target under controlled sputtering conditions. Structural analysis by X-ray diffraction revealed an improvement in crystallinity in the (200) direction with increasing N ratio. In contrast, higher N ratio led to the suppression of (111) and (220) peaks, indicating a significant influence of N on the crystal structure and orientation. The films’ thickness and morphology, examined using scanning electron microscopy and energy-dispersive X-ray spectroscopy, showed uniform and homogeneous growth with smooth surface topologies. Optical properties, assessed by UV–Vis-NIR spectrophotometry, demonstrated a decrease in transmittance and a redshift in the absorption edge with increased N doping, corresponding to a narrowing of the energy bandgap from 3.7 eV to 3.45 eV. This bandgap reduction is attributed to N incorporation substituting oxygen sites, introducing defect states within the band structure. Additionally, the impact of substrate temperature on film growth enhanced crystallinity and orientation along the (111) plane at higher temperatures, with a simultaneous reduction in film thickness due to increased adatom mobility and potential thermal decomposition. The evaluation of Kernel Ridge Regression (KRR) and Ridge Regression (RR) models revealed their effectiveness in predicting band gap values for thin films at varying substrate temperatures and thicknesses. While RR excelled in predicting a band gap of 3.6 eV for a film with a substrate temperature of 24 °C and a thickness of 112.7 nm, KRR outperformed in predicting a band gap of 3.65 eV for a film with a substrate temperature of 24 °C and a thickness of 107 nm. These findings elucidate the dual influence of N doping and substrate temperature on enhancing the functional properties of NiO thin films, promising for applications in optoelectronic devices and gas sensors.

Comprehensive investigation of 2-methylquinolinium-5-sulphosalicylate monohydrate: Synthesis, characterization, multifaceted analysis of molecular structure, optical, and nonlinear optical properties

We introduce the synthesis and characterization of a novel molecular salt crystal, 2-methylquinolinium-5-sulphosalicylate monohydrate (MQSSA), obtained through an equimolar reaction between donors (D) and acceptors (A) employing crystal engineering principles. The resulting proton transfer complex, MQSSA, crystallized into a monoclinic crystal system with space group P21/C, as revealed by SCXRD analysis. Significant peaks observed in PXRD analysis confirmed the crystallinity and purity of the material. FT-IR and FT-Raman spectroscopy were employed to analyze various functional groups present in the molecule. UV–Vis-NIR spectroscopy provided insights into absorbance transmittance, lower cutoff wavelength, and optical band gap, suggesting it's suitability for diverse optical applications, while characteristic emission was identified using PL measurements. Thermal stability was assessed via TG-DTA and TG-DSC techniques. Nonlinear absorption coefficient (β), nonlinear refractive index (n2), and third-order nonlinear susceptibility (χ3) were quantified using the Z-scan technique. Hirshfeld surface analysis and fingerprint plots were utilized to gain insight into intermolecular interactions and atomic arrangements within the MQSSA crystal, emphasizing the roles of crystal structure in H...H and O...H/H...O interactions. Additionally, quantum computational methods were employed to evaluate various molecular-level electronic characteristics, including molecular orbitals, molecular electrostatic potential maps, and first and second-order nonlinear optical (NLO) polarizability, providing insights into the molecular-level NLO response properties.