Band Gap Analysis Research Articles

Optimizing Charge Separation and Transport: Enhanced Photoelectrochemical Water Splitting in α-Fe2O3/CZTS Nanorod Arrays

This study explores the enhancement of α-Fe2O3 (hematite) nanorod arrays for photoelec-trochemical applications by constructing a Cu2ZnSnS4 (CZTS) heterojunction. While α-Fe2O3 offers good stability, a low cost, and environmental benefits, its efficiency is limited by slow oxygen evolution kinetics, high carrier recombination rates, and low conductivity. By introducing CZTS, a material with strong light absorption and charge transport properties, we enhance the separation of photogenerated charge carriers, reduce charge transfer resistance, and increase the carrier concentration, thereby boosting the overall photoelectrochemical performance. The experimental results show that a modified FC-15 photoanode achieves a photocurrent density of 3.40 mA/cm2 at 1.60 V vs. RHE, a substantial increase compared to 0.40 mA/cm2 for unmodified α-Fe2O3. Band gap analysis reveals a reduced band gap in the FC-15 material, enhancing light absorption and boosting the photoelectrocatalytic performance. In photoelectrochemical water-splitting tests, the FC-15 photoanode achieves a hydrogen production rate of 41.6 μmol/cm2/h, which is significantly improved over the unmodified sample at 5.64 μmol/cm2/h. These findings indicate that the CZTS/α-Fe2O3 heterojunction effectively promotes charge separation, enhances charge transport, and improves light absorption, substantially increasing photocatalytic efficiency. This heterojunction approach offers new insights and technical strategies for developing photocatalytic materials with potential applications in renewable energy.

Tuning the surface structure of zinc oxide nanorods by oxide entities of Ni for enhanced degradation of chlorophenoxy herbicide and chlorinated phenols

The surface of hexagonal ZnO was subjected to preliminary treatment with Ni2+ ions that transformed into a homogeneously coated layer by air calcination process in the loading range of 0.3–5 % with respect to the weight of ZnO support. The enhanced absorption in the visible region evidenced the formation of a visible light-responsive oxide entities of Ni2+ and Ni3+ that was further authenticated by multiple edges of variable energy in bandgap analysis. The photoluminescence (PL) spectra revealed the potential role of surface oxides in prolonging the life span of photon-induced excitons. The majority formation of Ni2O3 among the oxide entities, as the surface layer was substantiated by XRD and XPS analysis. The homogeneity, texture, and microstructure of the coated layer were examined by FESEM and HRTEM analysis. The charge retention ability as a function of the thickness of the coated layer was estimated by chronopotentiometry whereas the SPIES measurements coupled with Mott-Schottky analysis facilitated the fetching of the flat band potential as well as the semiconducting electrical nature of the coated materials. The loading of the catalysts as well as the impregnation level for optimum degradation/removal was evaluated in sunlight exposure for the removal of 4-chlorophenol (4-CP). The catalyst with optimum activity i.e. 0.5 % Ni2+ impregnated ZnO, was tested for the removal of potential carcinogens that included 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 2,4-dichlorophenoxyacetic acid (2,4-D). The progress of the removal process was monitored by HPLC, and the extracted data was used for kinetic studies. The efficacy of the synthesized catalysts was further evaluated for the removal of a concoction of chlorophenol isomers i.e., 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,5-dichlorophenol (2,5-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP), both in complete spectrum and visible region (400–800 nm) natural sunlight exposure and established the kinetics of the degradation process.

Plants-extracts mediated CuS nanoparticles: An effective antibacterial agent

Antibacterial activity of plant-mediated synthesized CuS nanoparticles against gram-positive Bacillus subtilis and gram negative Pseudomonas putida is studied in this presented work. A facile hydrothermal approach was followed to synthesize spherical shaped CuS nanoparticles using flowers extract of Tagetes patula (S1), leaves extract of Azadirachta indica (S2), and bark extract of Terminalia arjuna (S3). Crystal phase identification, average crystallites size, surface morphology, absorbance spectra and energy band gap analyses of samples were further determined using XRD, SEM, and UV-DRS spectroscopy respectively. Furthermore, under irradiation of visible light, antibacterial activity of marigold flowers mediated (S1), neem leaves mediated (S2), and arjuna bark mediated (S3) CuS samples were studied. XRD data confirmed the marigold mediated CuS sample has relatively smaller crystallites size of 10.67 nm. The estimated band gap energies for respective S1, S2, and S3 samples are 174 eV, 175 eV, and 177 eV. The antibacterial analysis of S1 sample displays its excellent antibacterial activity with the formation of relatively large inhibition zones of 29 mm and 30 mm diameters, against Bacillus subtilis and Pseudomonas putida respectively. The demonstrated antibacterial activity of biocompatible CuS nanoparticles suggests their potential use in biomedical applications.

Self-powered γ-In2Se3/p-Si heterojunction for photodetection: exploring humidity and light intensity dependent photoresponse

In this study, high-quality γ-In2Se3 thin films were successfully deposited on p-Si substrates via the RF sputtering technique. Structural characterization using XRD and Raman spectroscopy confirmed the formation of the hexagonal γ-phase of In2Se3 film. FESEM analysis revealed the presence of small, homogeneous, and well-defined grains in the prepared γ-In2Se3 film. EDS analysis confirmed the stoichiometric composition (∼ 2:3) of the In2Se3 films. XPS further validated the presence of In, Se, and Si elements in the deposited films. Band gap analysis using UV-visible spectroscopy yielded a value of 1.96 eV for the γ-In2Se3 film. Integration of γ-In2Se3 with p-type Si enhanced photoresponsivity of 47.9 mA/W, photosensitivity of 282, and photo detectivity of 8.45 × 1010 Jones. The self-powered γ-In2Se3/p-Si heterojunction-based photodetector exhibited rapid rise time attributed to the type II band alignment structure, facilitating efficient electron-hole pair separation and minimizing recombination. Furthermore, humidity and light intensity-dependent photodetector properties of γ-In2Se3/p-Si heterojunction photodetector were also investigated. An increase in photocurrent from 271 to 291 µA was observed with rising humidity levels, indicating the device’s sensitivity to humidity variations. Furthermore, light intensity dependence studies revealed a linear relationship between photocurrent and incident light intensity, demonstrating the device’s reliable response across various illumination levels.

Multi-functional periodically heterogeneous structures for energy harvesting and vibration attenuation-effects of piezoelectricity and shunting circuits

Abstract We explore a kind of metamaterial plate structures intended for simultaneous energy harvesting and vibration control. These structures are designed using a periodically perforated piezoelectric plate (the matrix) with elastic inclusions situated in the holes and serving for the resonators. The design options comprise two- and three-phase configurations related to the mechanical connection between the matrix and inclusions. By introducing a singularity—the focal spot created as a defect in the perfectly periodic structure and using the theory of super-cell, an enhanced piezoelectric energy harvester is obtained. It is observed that such a meta-structure serves as a dual-purpose system: efficiently capturing vibrational energy at a focal spot while maintaining the overall vibration attenuation throughout the structure. The band gap analysis based on the Bloch’s wave decomposition theory shows that by concentrating energy and halting vibration propagation, approximately 10 times energy harvesting enhancement and a remarkable 100 dB reduction in vibrations are achieved simultaneously. Besides the passive response of these meta-structures, we consider its extension by an external electric circuit (EC). Such modified configurations enable to exploit ‘actively’ the piezoelectric plate property to transmit the mechanical response between two, or more distant locations. Due to nonlocal interactions introduced by means the controllable EC, we consider optimization of the EC impedance to reduce the vibrations at a selected location of the whole structure without any external energy supply. The computational study discovers perspectives and benefits of designing such active self-powered meta-structures.

Charge transport properties and photostability of microcrystalline cellulose derived from Gigantochloa scortechinii-supported ZnO for enhanced acetaminophen degradation

A facile chemical mixing procedure was utilized to fabricate microcrystalline cellulose (MCC) derived from Gigantochloa scortechinii-supported ZnO photocatalysts, with different MCC content. The successful incorporation of ZnO onto the MCC surfaces was characterized by multitudinous characterization techniques. The photocatalytic evaluation studies were carried out under a very low UVC light intensity (9 W) against acetaminophen (ACE) in the aqueous solution. The MCC-supported ZnO (0.5:1) composites photocatalyst demonstrated a rapid and enhanced performance within 180 min under normal conditions, with a two-time higher value of rate constant k (1.12 ×10−2 min−1) as compared to pristine ZnO. The improved efficiency under UVC irradiation was associated with the excellent separation capability of photoexcited charge carriers, ease of electron migration, and electrons’ mediators by the MCC in the composite photocatalyst, as demonstrated by the band gap and photoluminescence analyses. The major reactive species were found to be hydroxyl radicals (•OH) and photoexcited holes (h+). The best photocatalyst has high photostability since it can be recycled up to five times towards ACE degradation without any regeneration step.

Band gap generation in cantilever beams through periodic material removal

Traditional methods for generating band gaps in beams usually involve adding periodic elements like tuned mass dampers or masses, or applying complex geometrical changes. This research suggests a subtraction-based method achieved by removing material in the thickness direction through straightforward machining operations, thus forming periodic cells. The numerical studies start with band gap analysis, using periodic theory to assess different periodic cell configurations. This is followed by numerical and experimental studies on cantilever beams, each containing a set number of these periodic cells. Non-contact vibration measurements are conducted on one plain and six machined aluminum beams using a multipoint laser vibrometer and an automated impact hammer. The experimental findings corroborate the band gaps predicted by the numerical model, confirming the effectiveness of this approach. The study notes that the optimal periodicity of the cells and the contrast in thickness vary with the beam’s dimensions, and that the thickness contrast markedly affects the quantity, width, and intensity of the resulting band gaps. These results indicate that (1) periodic material removal in beam-like structures allows improved vibration reduction while mass is reduced, and (2) manufacturing can play a key role in vibration control in simple structures.

Possible metal oxide cathode materials for Al-ion batteries: A first principle study

This study investigates various Aluminum (Al) -ion oxide cathode materials, considering their structural properties/stability, cell voltage, band gap analysis, and electrical/ion-diffusion rate-capability. The studied materials are AlMn2O4, AlMoO3, AlTiO2, AlV2O5, AlLiCo2O4, and AlCo2O4. The calculations are conducted using Density Functional Theory (DFT) methods, specifically Generalized Gradient Approximation (GGA) and GGA + U. We employ various noble approaches and techniques to assess the properties of the materials. The findings reveal structural stability after deintercalation of Al ion for all the considered structures. AlMn2O4 exhibits the highest stability due to its strong structural framework, while TiO2 is suspected for this property. Voltage estimation suggests higher possible voltages for AlCo2O4 and AlLiCo2O4 materials, despite not being experimentally examined. Calculated intrinsic-like and extrinsic-like band gaps demonstrate the highest conduction for AlCo2O4. Evaluation of rate-capability recognizes the highest electrical/ion-diffusion rate-capability for AlCo2O4 and AlLiCo2O4. Finally, this study introduces two new superior electrode materials for Al-ion batteries (AIBs), i.e. AlLiCo2O4 and AlCo2O4, with promising properties for future AIBs.

Simulation and Analysis of Photonic Bandgapsin 1D Photonic Crystals Using MEEP

This study presents a comprehensive simulation and analysis of photonic band gaps in one-dimensional (1D) photonic crystals using the open-source software MEEP. Photonic crystals, with their periodic structures, exhibit photonic bandgaps that prevent the propagation of specific wavelengths of light, making them crucial for various optical applications. Unlike previous studies that primarily focused on theoretical and experimental methods, this research introduces a novel computational approach that enhances the accuracy and flexibility of modeling these bandgaps. Through detailed simulations, we explore the impact of different structural parameters on the photonic bandgap properties, providing valuable insights into optimizing these crystals for practical use. Our findings demonstrate significant improvements in the design and understanding of 1D photonic crystals, particularly in tailoring bandgaps for specific applications in optical devices. This work contributes to the advancement of photonic crystal technology by offering a robust framework for their analysis and application.

MoC nanoparticles embedded in superior thin g-C3N4 nanosheets for efficient photocatalytic activity

Photogenerated charge carrier transfer efficiency in graphitic carbon nitride (g-C3N4) based heterostructures depended strongly on the interface nature. In this paper, MoC nanoparticles less than 5 nm were implanted in superior thin g-C3N4 nanosheets to create high charge carrier separation and transfer efficiency. Cubic MoC in N-doped graphitic carbon was first fabricated using dicyandiamide and ammonium molybdate tetrahydrate at 800 °C. The MoC nanoparticles were homogeneously implanted in g-C3N4 nanosheets by further thermal polymerization of bulk g-C3N4 prepared using melamine and MoC/C composites to create a Schottky junction which was confirmed by band gap analysis and free radical capture test. Melamine and dicyandiamide also play important role to create highly efficient catalysts. The MoC nanoparticles revealed fine crystallinity. A well-developed interface between MoC and g-C3N4 was observed. Because of high conductivity of MoC, well-developed interface, and co-catalyst role of MoC, the MoC/g-C3N4 junction exhibited ideal photocatalytic activity for dye degradation and water splitting. The kinetic constant rate of Rhodamine B degradation using a MoC/g-C3N4 sample created by optimized conditions was 0.061 min−1 which was 8.7 times of that of pristine g-C3N4 nanosheets. In the case of without co-catalyst addition, the photocatalytic hydrogen generation rate using this composite sample was 233.0 μmol g−1 h−1 which was 15.2 times of that of initial g-C3N4 nanosheets. These results supply an efficient approach for the first time to homogeneously distribute small cubic MoC nanoparticles in superior thin g-C3N4 nanosheets to construct heterostructures and greatly reduce photogenerated charge carrier recombination.

Research on out-of-plane vibration band gap calculation of two-dimensional periodic grillage structures based on spectral element method

The vibration of ship and marine structures directly impacts their structural performance and noise levels. Therefore, the vibration band gap characteristics of two-dimensional periodic grillage structures are investigated based on spectral element method in this article. Firstly, the governing motion equation of out-of-plane vibration of periodic grid structures is established in light of the Bloch theorem, and the shear spring oscillator system is introduced to simulate the first-order vertical shear vibration of bottom plate. As a result, the periodic oscillator coupling grid structure model can be proposed. Based on the periodic grid structures, the influence of material distribution on vibration band gap is obtained. Meanwhile, the dispersion relations and vibration transmission of periodic coupling model are calculated and the coupling effect of local resonance system on the band gap characteristics is analyzed. At last, a general approach for equating periodic grillage unit to numerical model is outlined and summarized on basis of the similarity of dynamic properties. The effectiveness and accuracy of the numerical method in out-of-plane vibration band gap analysis of periodic grillage structures are validated through the computation and model test.

Utilization of copper chromite-reduced graphene oxide nanocomposite for the wastewater remediation and effective supercapacitive performance

This article has detailed the growth of virgin copper chromite nanoparticles (CuCr2O4 NPs) and reduced graphene oxide sheet (rGO)-based CuCr2O4 nanocomposite through the process of reflux condensation method and calcination process. When exposed to visible light, these two synthesized nanomaterials exhibit enhanced photocatalytic activity which helps in the degradation of organic dyes such as methylene blue. Numerous characterization methods, including FTIR, UV–visible analysis, and XRD, verify the creation of these nanomaterials. The CuCr2O4-rGO nanocomposite's semiconductor nature is confirmed by the band gap analysis using Tauc's formula. The CuCr2O4 NPs grown on the rGO surface have a dimension of 6 nm, according to the TEM study and particle distribution graph. To find the reason for the enhanced photo-activity, we have proposed a photocatalytic mechanism which is supported by photoluminescence result. Recyclability in five more cycles is used to measure the stability of the nanocomposite, and it is found that photocatalytic efficiency does not significantly decline up to five cycles. When exploring the CuCr2O4-rGO nanocomposite as a material for supercapacitor electrodes, it showcased a remarkable specific capacity of 681.43 F/g at 0.5 A g−1. Moreover, the CuCr2O4-rGO nanocomposite electrode displayed a long-term life cycle, retaining 93.8 % of its initial capacity after 1200 cycles, paired with a commendable Coulombic efficiency of 95.31 % and outstanding power and energy density of 1504 W/kg and 23.66 Wh/kg respectively.

Ferromagnetism, bandgap, and impedance analysis of Mn-doped SnO2 synthesized by single-step wet chemical approach

Ferromagnetism, bandgap, and impedance analysis of Mn-doped SnO2 synthesized by single-step wet chemical approach

Tuning MXenes Towards Their Use in Photocatalytic Water Splitting

Finding appropriate photocatalysts for solar‐driven water (H2O) splitting to generate hydrogen (H2) fuel is a challenging task, particularly when guided by conventional trial‐and‐error experimental methods. Here, density functional theory (DFT) is used to explore the MXenes photocatalytic properties, an emerging family of two‐dimensional (2D) transition metal carbides and nitrides with chemical formula Mn+1XnTx, known to be semiconductors when having Tx terminations. More than 4,000 MXene structures have been screened, considering different compositional (M, X, Tx, and n) and structural (stacking and termination position) factors, to find suitable MXenes with a bandgap in the visible region and band edges that align with the water‐splitting half‐reaction potentials. Results from bandgap analysis show how, in general, MXenes with n = 1 and transition metals from group III present the most cases with bandgap and promising sizes, with C‐MXenes being superior to N‐MXenes. From band alignment calculations of candidate systems with a bandgap larger than 1.23 eV, the minimum required for a water‐splitting process, Sc2CT2, Y2CT2 (Tx = Cl, Br, S, and Se) and Y2CI2 are highlighted as adequate photocatalysts.

Effect of various polymer types on Fe2O3 nanocomposite characteristics: insights from microstructural morphological, optical and band gap analyses

Effect of various polymer types on Fe2O3 nanocomposite characteristics: insights from microstructural morphological, optical and band gap analyses

Salicylaldehyde salicyloyl hydrazone and its copper(II) complex: synthesis, characterization, DFT, optical band gap, antibacterial activity, and molecular docking analysis

A complex of Cu(II) with a bidentate Schiff base, salicylaldehyde salicyloyl hydrazone (SSH), was synthesized by refluxing copper(II) chloride with this ligand. The formation of the complex, the nature of bonding, and the geometry of the complex were established via physicochemical and spectroscopic techniques. The composition of the complex was found to be a 1:2 metal-ligand ratio as Cu(SSH)2. Electronic absorption spectral studies revealed that the copper adopts a distorted tetrahedral geometry upon complexation with SSH. The optical band energy for the complex was determined from absorption spectroscopy. The obtained band gap of 2.66 eV characterizes the complex as a semiconductor. The most stable conformations of the Schiff base (SSH) and Cu(SSH)2 complex have been computed, shedding light on their structural and electronic properties, and highlighting their potential reactivity and stability. The ligand exhibits a higher reactivity towards electrophiles, while the complex displays a greater affinity for nucleophiles. The in vitro antibacterial analysis with agar cup well method and in silico molecular docking analysis indicate that both the ligand and its complex with copper have potency to inhibit bacterial infections. Based on their growth inhibition, minimum inhibitory concentration (MIC) values, and robust interaction with studied proteins of the pathogens, these compounds hold a prospective avenue for the advancement of antibiotics.

Comparative Analysis of Hydrogen Molecule Interaction with B-Au and N-Au Co-Doped Graphene Nanoribbons: DFT Insights

In the present study, B and N atoms are co-doped with Au atom in graphene nanoribbons and has been analysed for hydrogen molecule interaction with the aid of Density Functional Theory. A comparative analysis is carried out between N-AuG and B-AuG substrate towards H2 molecule. The structural as well as electronic properties of the optimized structures have been studied. Different theoretical parameters which include adsorption energy, charge redistribution, and bandgap analysis have been computed to determine the effectiveness of substrate.

New bandgap analysis method for metamaterial structures using variational principle

This paper presents an efficient bandgap analysis method for metamaterial structures based on variational principle and linear expression technique. This is in view of the challenges in constructing a displacement function that satisfies the Bloch boundary when applying the traditional energy method to analyze the dispersion relations of metamaterial structures. Also, the inclusion of the wave numbers in the displacement function leads to inefficient computation. While there have been methods, such as virtual springs, proposed to deal with such problems, issues remain to be resolved. The main idea of the current paper is the solution of linear uncorrelated coefficients by processing the constraints. In this way, the unknown coefficients in the equations of motion can be linearly expressed, thereby allowing the equations to become variational. Both Gaussian elimination and null-space techniques are used to implement the method. The solution procedures of the two techniques are detailed and demonstrated by using one-dimensional and two-dimensional metamaterial structures. The accuracy of the method is verified by comparing the results with those from using finite element method. The calculation efficiency is compared with that of the traditional energy method in terms of both the matrix dimension and the number of the points of wave numbers. The results show that the method has a much higher calculation efficiency than that of the traditional energy method. The method proposed in this paper is free of convergence problems in dealing with boundary problems. Furthermore, in the discussion of combined periodic structures, it is shown that the method still has good geometrical applicability to structures containing multiple boundary conditions, showing great potential in solving complex engineering problems.

Optoelectronic and transport properties of Lead-Free halide based Na2AgTlZ6 (Z = Cl, Br, I) double perovskites for energy harvesting applications

The bandgap engineering and deliberate band edge manipulation of perovskites make them potential candidates for the photovoltaic industry. Here we theoretically investigate the structure, density of states, and photovoltaic and thermoelectric characteristics of Na2AgTlZ6 (Z = Cl, Br, I) using WIEN2k code. The incorporation of Br and I at the Cl site caused the increase in lattice constant which leads to the decrease in bulk modulus and Debye temperature. The computed values of Poisson (<0.26) and Pugh (<1.75) ratio verified their brittle nature. The bandgap analysis reveals direct bandgap nature and bandgap value lie in the visible region for parent composition and infrared and far infrared when Cl is replaced with Br and I. The density of state plots uncovers the shifting of energy states in valence and conduction bands towards the Fermi level with the increasing number of electrons in the halogens. The increase in the value of dielectric constant, refractive index, and shifting of peaks towards lower energy value is witnessed with atomic number of halogen atoms. The viability of these compositions for thermoelectric devices is further confirmed when electrical conductivity and Seebeck coefficient dependent Figure of merit and power factor are evaluated in the temperature range of 200–800 K. In addition, the anisotropic nature of studied compositions is explored through the computation of the modulus of elasticity including Young’s modulus, Shear modulus in addition to compressibility, and Poisson’s ratio.

Effect of poling on photocatalytic activity with SrBi4Ti4O15 catalyst

AbstractThis research article is related to a bismuth oxide‐layered pseudo‐perovskite ferroelectric material and its capabilities in the area of photocatalysis. SrBi4Ti4O15 (SBT) catalyst was prepared via a solid‐state reaction followed by calcination at 950°C sustained over 4 h. X‐ray diffraction, X‐ray photoelectron spectroscopy, bandgap analysis, Raman spectroscopy, and scanning electron microscopy confirmed the successful synthesis of the SBT catalyst. The photocatalysis capability was checked on a methylene blue (MB) model dye. The poling of the SBT catalyst was performed under 2 kV/mm of electric field. The poling of the catalyst material played a crucial role in enhancing the photocatalytic activity. Moreover, the effect of volume (k(v)), initial concentration (k(ic)) of the MB dye, amount of catalyst (k(c)), and intensity (k(i)) of the light were examined and analyzed by the mathematical model. This study suggested that higher intensity and amount of catalyst enhance photocatalytic activity, whereas higher concentration and volume of dye suppress the photocatalytic activity. The amount of catalyst showed the highest effect on the photocatalytic activity. The rate constant is influenced by these factors and the order of influence is k(c) &gt; k(i) &gt; k(v) ≃ k(ic).