Band Gap Energy Research Articles

Advanced spectroscopic approach for exploring the structural, optical, and electronic properties in dye-functionalized chitosan biopolymers

This study employed advanced spectroscopic techniques to investigate the structural and optical properties of chitosan (CS) biopolymer films modified with natural dyes from Cosmos Sulphureus Cav. (CSC) flowers. FTIR results indicated that the inclusion of CSC dyes led to broader absorbance and decreased transmittance. Distinct absorption regions were identified, and the optical energy band gap (OEBG), transport gap, and exciton binding energy were calculated using Tauc’s method. The OEBG was found to be 5.44 eV for CS while for CS-CSC dye samples, it dropped to 2.24 eV and The Urbach energy increased from 0.44 eV to 0.60 eV, indicating the presence of high tail states in the band gap region. The electron–phonon interaction was found to increase from 11.35 to 15.58. The oscillator energy values (4.13 eV-2.33 eV) at low energies obtained using Wemple-DiDomenico model are found to be close to OEBGs using Tauc’s model. Additionally, from the Drude-Lorentz model the N/m* was found to increase from 1.69 × 1052 to 1.27 × 1054. The third order non-linear polarizability parameter, the linear optical susceptibility and the non-linear index of refractions were all found to increase upon increasing the CSC dye concentrations.

Characterising Optical Properties of Doped Metal Complex Nanocomposite Films with PVA/PVAC for Optoelectronics

This study investigates the optical properties of nanocomposite films made from polyvinyl alcohol (PVA), polyvinyl acetate (PVAC), and a 50/50 polyblend of PVA and PVAC, doped with varying concentrations 0, 3, 6, and 9 wt.% of the metal complex Fluoro pentaamine cobalt (III) fluoride [Co(NH₃)₅F]F₂ (FACF). The films were prepared using a solvent casting method and analysed with a computerised UVـــVISـــIR spectrophotometer over the wavelength range of 250–850 nm. Key optical parameters, including the refractive index, extinction coefficient, and optical conductivity, were determined through absorption studies. The optical absorbance increased with higher FACF concentrations. UV-Vis spectra were used to estimate the band gap energies and investigate the electronic transitions from the valence band to the conduction band. A decrease in the band gap for allowed direct transitions was observed: from 4.0 eV to 2.55 eV for PVA, 4.1 eV to 2.6 eV for PVAC, and 4.35 eV to 2.6 eV for the polyblend as the FACF content increased. Additionally, both the extinction coefficient and refractive index increased with higher FACF concentrations. These nanocomposite films show potential for use in photovoltaic cells, optical sensors, LEDs, photodetectors and other luminescent devices, though further research is needed. KEYWORDS absorbance spectrum, casting method, energy gap, polyblend, polyvinyl acetate, polyvinyl alcohol

Influence of Janus structure on the thermoelectric performance of the α-Se monolayer

Aiming at exploring whether the Janus structure is beneficial to improving the thermoelectric (TE) performance, we systematically study the TE properties of the α-Se-monolayer-based Janus structures including α-SSe2 and α-TeSe2 monolayers. In comparison with the semiconducting α-Se monolayer, the Janus α-SSe2 and α-TeSe2 monolayers are still kept to be indirect semiconductors but with suppressed energy bandgaps. Moreover, the phononic thermal conductance will be suppressed with other parameters like Seebeck coefficients, electrical conductances, and electronic thermal conductances being changed correspondingly. The TE figures of merit ZTs of the Janus α-SSe2 and α-TeSe2 monolayers are always greater than that of the α-Se monolayer, indicating that the Janus structure should be a potential scheme used to improve the TE performance of materials.

Study of morphology, phase composition, optical properties, and thermal stability of hydrothermal zirconium dioxide synthesized at low temperatures.

Oxide nanoparticles exhibit unique features such as high surface area, enhanced catalytic activity, and tunable optical and electrical properties, making them valuable to various industry applications as well as for the development of new research projects. Nowadays, ZrO2 nanoparticles are widely used as catalysts and precursors in ceramic technology. Hydrothermal synthesis with metal salts is one of the most common methods for producing stable tetragonal-phase zirconium dioxide nanoparticles. However, hydrothermal synthesis requires relatively high process temperatures (160-200°C) and the use of advanced heat-resistant autoclaves capable of maintaining high pressure. This paper investigates how different precursors (ZrOCl₂·8H₂O and ZrO(NO₃)₂·2H₂O) and synthesis temperatures (110-160°C) affect the phase composition, optical properties, size, and shape of ZrO₂ nanoparticles produced by hydrothermal synthesis without calcination. In addition, the effect of temperature exposure in the range of 100-1000°C on the phase stability of the synthesized nanoparticles was studied. X-ray diffraction and Raman spectroscopy techniques were used to determine the structure and phase composition, while the optical properties were examined through the analysis of transmission and absorption spectra in the visible and UV ranges. It was found that the obtained particles at synthesis temperatures of 110-130°C have predominantly cubic c-ZrO2 phase, which changes to monoclinic phase when heated above 500°C. Analysis of visible and UV spectroscopy data reveals that the experimental samples have pronounced absorption in the middle UV range (200-260nm) and have an energy band gap Eg varying from 4.8 to 5.1eV. The hydrothermal powders synthesized in this study can be used as absorbers in the mid-UV range and as reinforcing additives in the preparation of technical ceramics.

Preparation and characterization of CuBO2-based photocatalysts and doped variants

An eco-friendly CuBO2-based photocatalyst has been doped by a lanthanide for the first time. Gd3+ and Gd3+/Bi3+-doped CuBO2 are synthesized by the hydrothermal method to study their magnetic properties. Then they are analyzed by XRD, UV-Vis, SEM, and VSM. The maximum amount of doping is x= 0 − 1.5% in Cu1–3xGd3xBO2 and Cu1–3xBi3x/2Gd3x/2BO2 formulas as they are analyzed in XRD. For concentrations higher than x = 2%, the additional peak indicates that doping is incomplete. The XRD pattern of CuBO2 confirms that its crystal structure is a hexagonal one with the R3 ̅m space group. According to UV-Vis analysis, the bandgap energies are 2.711, 2.753, and 2.765 for CuBO2 and doped systems. Additionally, the morphology of particle sizes is confirmed according to SEM images. Meanwhile, the magnetic properties of synthesized material are studied by VSM, and the doped compound exhibited higher magnetic properties than CuBO2, which is associated with the exchange interaction of electron and d spins in Gd3+ and Bi3+. The study aims to provide insights into the magnetic properties of lanthanide-doped CuBO2-based photocatalysts, potentially paving the way for developing improved magnetic materials for various applications.

Description of excitonic absorption using the Sommerfeld enhancement factor and band-fluctuations

Abstract One of the challenges of excitonic materials is the accurate determination of the exciton binding energy and bandgap from optical measurements. The difficulty arises from the overlap of the discrete and continuous excitonic absorption at the band edge. Many researches have modeled the shape of the absorption edge of such materials on the seminal formulation proposed by Elliott in 1957 (Phys. Rev. 108 1384–9) and its several modifications such as non-parabolic bands, magnetic potentials and electron–hole-polaron interactions. However, exciton binding energies obtained from optical absorption often vary strongly depending on the chosen ‘Elliott formula’. Here, we propose an alternative and rather simple approach, which has previously been successful in the determination of the optical bandgap of amorphous, direct and indirect semiconductors, based on the band-fluctuations (BFs) model. In this model, the fluctuations due to disorder, temperature or lattice vibrations give rise to the well known exponential shape of band tail states. The formulation results in an analytic equation for the fundamental absorption with 6 parameters only. To test it, the binding energy and optical bandgap of GaAs and the family of tri-halide perovskites ( MAPbX 3 ), X = Br , I , Cl , over a wide range of temperatures, are obtained by fitting the modified Elliott model. The results for the bandgap, linewidth and exciton binding energy are in good agreement with reports based on non-optical measurements. Moreover, due to the polar nature of perovskites, the retrieved binding energies can be compared with those computed with a model proposed by Kane (1978 Phys. Rev. B 18 6849). In the latter model, the exciton is surrounded by a cloud of virtual phonons interacting via the Frölich interaction. As a consequence, the upper bound for the binding energy of the exciton-polaron system can be estimated. These results are in good agreement with the optical parameters obtained with the proposed Elliott equation including BFs.

Cu-ZnO/CuO porous heterostructures for adsorption of lead ion

The pure ZnO and Cu-ZnO/CuO (CuZC) heterostructures had been successfully synthesized using an orange fruit peel extract-based solution combustion synthesis approach. The XRD result revealed the wurtizite phase structure of ZnO NPs with a crystallite size of 12 nm for the CuZC heterostructures. The indirect UV–vis-DRS analysis revealed the band gap energy of ZnO NPs and CuZC heterostructure to be 3.16 and 2.95 eV, respectively. Porous morphology and absence of impurities were confirmed from the FESEM-EDS and TEM/HRTEM analyses. The lead (Pb) ion adsorption potential of NPs was analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES) technique. The removal efficiency for CuZC heterostructure at an initial Pb ion concentration of 20 mg/L is 96.3 %. Based on the adsorption kinetics and isotherm models fitting value, dominance of the chemisorption adsorption process was confirmed. The doped NPs have the potential to be used as an effective and favorable adsorbent material for remediation of heavy metal ions from water solutions.

Bacterial allantoin mediated optimally biosynthesized silver nanoparticles exhibit antioxidant, antibacterial, and seed germination promoting activities

The biosynthesis of silver nanoparticles (AgNPs) presents a sustainable, cost-effective, and scalable alternative to conventional synthesis techniques. This study investigates microbial allantoin as a biogenic reducing agent for the synthesis of AgNPs, emphasizing their antioxidant, antibacterial, and seed germination enhancement properties. Optimally synthesized allantoin-mediated AgNPs exhibited a crystalline size of 3.66 nm with a band gap energy of 3.39 eV. Scanning Electron Microscopy (SEM) analysis showed spherical nanoparticles with an average particle size of 84 nm, while particle size analysis revealed a zeta potential of −26.7 mV and a hydrodynamic diameter of 137.1 nm. The AgNPs displayed significant free radical scavenging activity, achieving 58% and 70% inhibition in H₂O₂ and DPPH assays, respectively. Furthermore, these AgNPs demonstrated substantial antibacterial activity against both Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa. Additionally, allantoin-mediated AgNPs promoted germination in Cicer arietinum seeds within 48 h, indicating their potential as plant growth stimulants. This pioneering study on microbial allantoin-derived AgNPs suggests promising applications across pharmaceuticals, environmental science, and cosmetic fields.

An investigation on structural, morphological, thermal, optical, and antibacterial properties of chitosan-oleic acid (CH-OA) composite thin films

Recent researches show an increasing interest in developing polymer composite films to improve their properties for use in biodegradable food packaging and optoelectronic applications. For this purpose, this study aims to fabricate and characterize chitosan-oleic acid (CH-OA) composite films for different optical applications. Solution casting process was used to prepare CH-OA composite films. XRD patterns of the films showed that the addition of OA up to 3.0 % (v/w) reduced their crystalline structure. The morphology of the composites was studied using SAED and SEM. SAED patterns indicated good mixing ability between OA and CH, while SEM analysis revealed the heterogeneous surface of the films and proved the incorporation of OA into the CH matrix. The thermal stability of the films was studied using DSC and TGA analyses of the composites, and their thermograms indicated the interactions between CH and OA which improved their thermal stability. The optical properties of the films were performed in the spectral region of 250–2500 nm. The near-infrared results showed that increasing the OA concentration can lead to strong local interactions between OA and other groups in the CH matrix. The transmittance spectra of CH-OA composites at UV wavelength ≤ 400 nm showed values ​​close to 0 %, indicating that all the films have UV-blocking features. Significant changes in color and opacity parameters were detected. In the visible range (400–700 nm), the absorption coefficients, absorption indices and refractive indices of the films were evaluated. The absorption edges, Urbach energies, direct and indirect energy band gaps were in the ranges of 2.491–1.849 eV, 0.591–2.008 eV, 2.698–2.578 eV and 2.167–1.422 eV, respectively, as well as the refractive index decreased from 1.837 to 1.735 to 1.149–1.119 by increasing the OA concentration to 3.0 % (v/w). The produced composites have high optical conductivities up to 1010S−1 indicating good photoresponse and enhanced electronic excitation due to increased absorption coefficient of the film. The Wemple-DiDomenico model was used to evaluate the dispersion energies and related parameters. The values ​​of dispersion energy and oscillator energy decreased from 12.388 to 1.327 eV and 6.7268 to 5.7525 eV, respectively, with the OA content increasing to 3.0 % (v/w). The swelling degree and degradation rate were also determined and the results showed an improvement in the swelling and degradation ability of the films. The composites showed the appearance of inhibition zones indicating antibacterial activity against Bacillus cereus, Staphylococcus aureus, and Escherichia coli. These obtained results indicate that CH-OA composite films exhibited better physico-chemical properties with significant improvement and thus can be used in biodegradable food packaging and optoelectronic devices.

Synthesis, Spectral Characterization, Antimicrobial Activity, DFT Calculations, Molecular Docking and ADME Studies of Novel Schiff Base Co(II), Ni(II), Cu(II) and Zn(II) Complexes Derived from 4-nitro-ortho-phenylenediamine.

A condensation reaction was carried out between 4-nitro-ortho-phenylenediamine and 5-bromosalicyaldehyde to synthesize a novel Schiff base ligand 2,2'-[(1E,1'E)-(4-nitro-1,2-phenylene) bis (azaneylylidene) bis (methaneylylidene)] bis (4-bromophenol) [NB] in the current investigation. This was followed by the synthesis of metallic complexes comprising the Co(II), Ni(II), Cu(II) and Zn(II) transition metal ions. A hexadentate environment encircling metal complexes was corroborated by the results of varied spectroscopic methods that were employed to unravel the structure of the ligand and metal complexes. The Tauc's plot and Urbach energy were utilized for quantifying the optical energy band gap to provide insight into optical characteristics. The Coats-Redfern method of thermal analysis was implemented to do the kinetic and thermodynamic calculations. Furthermore, DFT studies were performed to predict geometrical structures and the stability of the compounds. Thorough investigation to evaluate their biological efficacies, docking studies was executed against COVID-19 main protease (PDB-7VAH), Dengue virus NS2B/NS3 protease (PDB-2FOM) and Mycobacterium Tuberculosis (PDB-5AF3). Apart from this, in silico ADMET studies were also accomplished for elucidation of drug likeness characteristics and the results attained disclose the significant proficiency of synthesized compounds. Besides this, antimicrobial studies were assessed with different microbial strains and result validates cobalt and zinc complexes as most potent against the selected bacterial and fungal strains.

Reaching medium entropy oxides with rocksalt structure based on cluster-plus-glue-atom model: A case study of Co-Ni-Cu-Zn-O system with tunable optoelectrical properties

Mg–Co–Ni–Cu–Zn–O is the firstly reported high entropy oxide (HEO) which has great promise in optoelectrical applications. However, the multicomponent and decreased configurational entropy by extracting one element from (Mg, Co, Ni, Cu, Zn) makes it difficult to synthesize single-phase medium entropy oxides (MEOs) especially when the cations are non-equimolar. In this paper, we synthesized different compositional-type of non-equimolar Co–Ni–Cu–Zn–O MEOs possessing single-phase rocksalt structure guided by the cluster-plus-glue-atom model. Interestingly, Co21Ni43Cu16Zn16O96 and Co17Ni47Cu16Zn16O96 have the lowest single-phase formation temperature (850 °C) when the total cation content is kept unchanged. Further increase or decrease of Co/Ni content (none, little, more) will increase the difficulty of single-phase formation ability and temperature (900–1200 °C). It is suggested the single-phase formation ability of Co–Ni–Cu–Zn–O MEOs is closely related to the Gibbs free energy (ΔG) and average cation-size difference (δ). The linear decrease of Co content and increase of Ni content can monotonously enlarge the energy band gap (Eg) from 1.52 eV to 1.93 eV and increase the electrical impedance with five orders of magnitude (∼103 Ω–∼108 Ω), which may be valuable in the fields of optoelectrical devices.

Constructing ZnO/NiO Nanocomposites as a Photocatalyst and Investigating Photocatalytic Effectiveness for Wastewater Treatment.

The goal of the present work is to create ZnO/NiO nanocomposites (NCs) for the photocatalytic destruction of organic contaminants using the co-precipitation technique. To investigate physiochemical characteristics, FT-IR, UV visible spectroscopy, SEM, and XRD were used. The ZnO hexagonal phase and the NiO cubic phase in the ZnO/NiO NCs were verified by the diffraction pattern. NCs were discovered to have larger average crystallite sizes. The bandgap energy calculated from the Tauc plot for the ZnO is 3.02 and 2.74 eV for the ZnO/NiO NC's. SEM analysis revealed the morphological study and particle size was calculated using the histogram technique and found to be 124.5 nm for the ZnO and 49.2 nm for the ZnO/NiO NCs. Photocatalytic degradation in the presence of sunlight showed 72.8% degradation of Methylene blue (MB) for the ZnO and 79.2% for the ZnO/NiO NCs. The increase in the photocatalytic capablity for the NCs is attributed to the synergistic effect between ZnO and NiO which effectively separated charge carriers preventing greater recombination rate. The robustness of ZnO/NiO NCs as a catalyst option was shown by their exceptional performance.

Influence of Bi2O3 on structural and optical characteristics of PbO⋅B2O3⋅Bi2O3⋅SiO2 glasses

In this study, the influence of Bi2O3 on the structural and optical characteristics of the glass samples with the molar composition of 17PbO⋅23B2O3⋅xBi2O3⋅(60-x)SiO2, prepared using the conventional melt quenching approach, is described. X-ray diffraction spectra reveal the amorphous nature of the prepared series. Density (D), molar volume (Vm), glass transition temperature (Tg), and other physical parameters have been evaluated. FTIR spectra show the presence of bismuth as [BiO3] and [BiO6] structural units and of borate as [BO3] and [BO4] structural units. It is found that the increase in non-bridging oxygens can be attributed to the increase in cut-off wavelength and decrease in bandgap energy with the rise in bismuth concentration. Urbach's energy values demonstrate that the presence of Bi2O3 in the existing glass system might affect the defect concentration. All glass samples possess a high refractive index suggesting that the current glasses may be useful for developing non-linear optical systems.

Electroabsorption in InGaAs and GaAsSb p-i-n photodiodes

The application of an electric field to a semiconductor can alter its absorption properties. This electroabsorption effect can have a significant impact on the quantum efficiency of detector structures. The photocurrents in bulk InGaAs and GaAsSb p-i-n photodiodes with intrinsic absorber layer thicknesses ranging from 1 to 4.8 μm have been investigated. By using phase-sensitive photocurrent measurements as a function of wavelength, the absorption coefficients as low as 1 cm−1 were extracted for electric fields up to 200 kV/cm. Our findings show that while the absorption coefficients reduce between 1500 and 1650 nm for both materials when subject to an increasing electric field, an absorption coefficient of 100 cm−1 can be obtained at a wavelength of 2 μm, well beyond the bandgap energy when they are subject to a high electric field. The results are shown to be in good agreement with theoretical models that use Airy functions to solve the absorption coefficients in a uniform electric field.

Eco-friendly fabrication of copper oxide nanoparticles using peel extract of Citrus aurantium for the efficient degradation of methylene blue dye

This study presents a simple, sustainable, eco-friendly approach for synthesizing copper oxide (CuO) nanoparticles using Citrus aurantium peel extract as a natural reducing and stabilizing agent. The synthesized CuO and CuO-OP were characterized using various techniques, including surface area measurement (SBET), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), and high resolution transmission electron microscope (HRTEM). DRS analysis determines band gap energy (Eg) of 1.7 eV for CuO and 1.6 eV for CuO-OP. FTIR confirmed the presence of Cu–O bond groups. The XRD and HRTEM results revealed monoclinic and spherical nanostructures, with average particle sizes ranging from 53.25 to 68.02 nm, as determined via Scherer’s equation. EDX analysis indicated incorporation of carbon (1.6%) and nitrogen (0.3%) from the peel extract. The synthesized CuO and CuO-OP NPs exhibited excellent photocatalytic efficiencies for methylene blue dye under UV irradiation, reaching 95.34 and 97.5%, respectively, under optimal conditions; the initial dye concentration was 100 mg/L, the pH was 10, the catalyst dosage was 1 g/L, and the contact time was 120 min. Isothermal studies showed that the adsorption of MB onto the nanoparticles followed the Freundlich isotherm model (R2 = 0.97 and 0.96). Kinetic studies indicated that the degradation followed pseudo-first-order kinetics, with rate constants (K1) of 0.0255 min−1 for CuO and 0.033 min−1 for CuO-OP. The sorption capacities were calculated as 98.19 mg/g for CuO and 123.1 mg/g for CuO-OP. The energy values obtained from the Dubinin–Radushkevich isotherm were 707.11 and 912.87 KJ mol−1, suggesting that chemisorption was the dominant mechanism.

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

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

Fabrication of CuS-MoO3 nanocomposite for high-performance photocatalysis and biosensing

The design and development of highly efficient nanostructure materials for photocatalytic and electrochemical applications is very necessary. In this study, CuS-MoO3 nanocomposite (NCs) was fabricated using a simple wet impregnation process and the photodegradation potential for 8 major hazardous dyes and electrochemical sensing of Dopamine was investigated. X-ray diffraction (XRD), Fourier transform - Infrared spectroscopy (FTIR), UV-Vis spectroscopy (UV-Vis), Photoluminescence spectroscopy (PL), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Transmission Electron Microscopy (TEM) were employed for characterization. Fabricated NCs are made up of CuS in the hexagonal phase and MoO3 in the orthorhombic phase, both of which react to UV light. Optical and electrochemical impedance spectroscopy (EIS) results show that improved photocatalytic performance is related to increased UV light spectrum sensitivity, inhibited charge carrier recombination, and decreased band gap energy in the NCs. Experimental findings showed that CuS-MoO3 (CMS) NCs had substantially more photocatalytic degradation activity than pure MoO3 and CuS nanoparticles (NPs). The prepared CMS NCs were then used for electrochemical analysis of Dopamine (DA). Electroanalytical results showed that the CMS NCs had enhanced electrochemical activity towards DA. The constructed sensor has a limit of detection of (6.61 µM) and proved that it is capable of being a sensor.

Molecular engineering in thizolo[5,4-d]thiazole-based donor-acceptor covalent organic framework Induced high-efficient photosynthesis of H2O2

Covalent organic frameworks (COFs), as a newly emerging kind of porous and crystalline materials, serve as an ideal template for hydrogen peroxide (H2O2) photosynthesis. However, the vision of achieving high efficiency and selectivity in H2O2 photosynthesis is greatly hindered by the large exciton binding energy and limited charge separation efficiency influenced by the molecular structure of the building blocks. Herein, we developed three newly designed COFs with a donor–acceptor (D-A) structure and incorporated regulatory units (fluorine, F, and methoxyl, OCH3) in the D-A pathway through molecular engineering to optimize electronic structure, the availability of activate sites, charge kinetics and O2 activation capacity. Due to electron-donating effect, OCH3-functionalization (NIES-COF-3) can strengthen the intramolecular electron transfer and interaction with O2. This results in a reduction of the energy barrier of the rate-determining step (*O2 → *OOH) and excellent O2-to-H2O2 photocatalytic activity under visible light irradiation, delivering an H2O2 production rate of 3238.4 μmol g−1h−1 and a high apparent quantum yield of 3.17 %. In addition, F-functionalization (NIES-COF-2) primarily reduces the band-gap energy and improve the O2 adsorption capacity compared to unfunctionalized NIES-COF-1. This work unveils insight into the catalytic activity-optimization mechanism of molecular engineering in the D-A structure and provides important references for photocatalysts.

Effect of an Electrical Field Applied to the Metal Capping Layer on the Electrical Properties of SiZnSnO Thin‐Film Transistors for Touch Sensor Application

Thin‐film transistors (TFTs) have been studied for their high mobility and stability to facilitate the development of TFT‐based touch sensors and electronic devices. A metal capping (MC) layer on the back channel of Si–Zn–Sn–O(SZTO) TFTs has been proposed to improve the electrical properties. MC, when adopted on the channel layer, has low resistance, leading to an improvement in the mobility of the TFT. The mobility of Ti/Al MC TFT has improved from 20.7 to 37.9 cm2 V−1 s compared to the pristine TFTs. Applying a potential voltage to the MC layer sensitively modulates the I–V characteristics of the TFT. The present study applies a voltage of 60 mV, similar to that of the human body, to MC‐TFTs to explore their possibilities as human touch sensors. The sensitivity and the energy bandgap modulation are also discussed.

Influence of ZnO on structural magneto-optical dielectric and antibacterial properties of NiFe2O4 (ZnO-NiFe2O4) nanocomposites prepared by sol–gel method

The present work investigates the structural, optical, magneto-dielectric and antibacterial characteristics of ZnO-NiFe2O4 nanocomposites (NCs). Spinel NiFe2O4 and ZnO powders were synthesized individually by the sol–gel method. Then by using the ultrasonification technique, a series of (1-x)NiFe2O4+xZnO (x = 0.0, 0.15, 0.30, and 0.45) NCs were prepared. Powder XRD pattern confirms the existence of both spinel NiFe2O4 and ZnO peaks in the nanocomposites. The observation reveals that as the amount of ZnO in the nanocomposite, there is an increase in the lattice constant from 8.372 Å to 8.383 Å. The addition of ZnO in the nanocomposites broadens the light-absorbing range and raises the band gap (eV) energy from 1.7 eV to 2.5 eV. The dielectric constant measured at 1 kHz decreased from 496 to 403 as the ZnO content in the nanocomposite increased. However, the dielectric constant for NF0.4/ZnO0.6 NCs measured at 1 kHz increased from 403 to 583 for an applied magnetic field of 7000 Oe. Spinel NiFe2O4 with ZnO content shows lesser saturation magnetization (Ms) and coercivity compared to pure NiFe2O4. The magneto-capacitance (MC%) as a function of the magnetic field for all composition shows a positive response. NF0.55/ZnO0.45 (40 µg/ml) NCs showed better antimicrobial activity as compared to NiFe2O4 (40 µg/ml). This study may extend the scope of this composite as an electrode material in supercapacitors.