Energy Gap Research Articles

Investigating the electronic properties of edge glycine/biopolymer/graphene quantum dots

This study systematically investigated four types of graphene quantum dots (GQDs) AHEX, ZTRI, ZHEX, and ATRI, and their interactions with glycine to form GQD-glycine complexes. Utilizing density functional theory (DFT) and the PM6 semiempirical method, the study analyzed electronic properties and structure-activity relationships. Global reactivity indices were calculated using Koopmans’ theorem, and quantitative structure-activity relationship (QSAR) parameters were assessed via SCIGRESS 0.3. The study further explored interactions using density of states (DOS) and quantum theory of atoms in molecules (QTAIM) analyses. Key findings revealed that glycine interaction significantly increased the total dipole moment (TDM) and decreased the HOMO/LUMO energy gap (ΔE) for the GQD-glycine complexes. Notably, ZTRI/glycine showed a TDM of 4.535 Debye and a reduced ΔE of 0.323 eV, indicating enhanced reactivity. Further interactions with cellulose, chitosan, and sodium alginate identified the ZTRI/glycine/sodium alginate composite as the most reactive, with a TDM of 8.020 Debye and the lowest ΔE of 0.200 eV. This composite also exhibited the highest electrophilicity index (56.421) and lowest chemical hardness (0.145 eV), underscoring its superior reactivity and stability. DOS analysis revealed that biomolecules contributed the most to molecular orbitals, with carbon atoms contributing the least. QTAIM analysis confirmed the greater stability of the ZTRI/glycine/sodium alginate complex compared to other studied composites. These results highlight the enhanced reactivity and stability of GQDs when interacting with glycine and sodium alginate.

Unveiling the charge density wave mechanism in vanadium-based Bi-layered kagome metals

The charge density wave (CDW), as a hallmark of vanadium-based kagome superconductor AV3Sb5 (A = K, Rb, Cs), has attracted intensive attention. However, the fundamental controversy regarding the underlying mechanism of CDW therein persists. Recently, the vanadium-based bi-layered kagome metal ScV6Sn6, reported to exhibit a long-range charge order below 94 K, has emerged as a promising candidate to further clarify this core issue. Here, employing micro-focusing angle-resolved photoemission spectroscopy (μ-ARPES) and first-principles calculations, we systematically studied the unique CDW order in vanadium-based bi-layered kagome metals by comparing ScV6Sn6 with its isostructural counterpart YV6Sn6, which lacks a CDW ground state. Combining ARPES data and the corresponding joint density of states (DOS), we suggest that the VHS nesting mechanism might be invalid in these materials. Besides, in ScV6Sn6, we identified multiple hybridization energy gaps resulting from CDW-induced band folding, along with an anomalous band dispersion, implying a potential electron-phonon coupling-driven mechanism underlying the formation of the CDW order. Our finding not only comprehensively maps the electronic structure of V-based bi-layer kagome metals but also provides constructive experimental evidence for the unique origin of CDW in this system.

Synthesis and Density Functional Theory Study on the Functionalization of Carbon Nanotube Conjugates with Amino Compounds and Their Application in Dyeing Processes

AbstractThis study investigates the functionalization of graphene nanotube (GNTs) conjugates with an amino compound called 1‐amino‐2‐hydroxy‐4‐naphthalene sulfonic acid (AHNSA‐GNTs). The study also evaluates the potential application of these conjugates in dyeing processes. The goal is to modify GNTs to enhance their interaction with dyes, thus improving the efficiency of dyeing textiles and the colorfastness of the resulting products. Multiple characterization methods, such as X‐ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to get a better look at the composites. The findings of the study indicate that AHNSA‐GNTs composites improve dye retention on wool fibers, which leads to a reduction in the consumption of excess dye and water. Density Functional Theory (DFT) calculations were utilized to investigate the electronic properties and binding energies of the functionalized CNTs, providing insights into the molecular interactions between the CNTs and amino compounds. Overall, this study highlights the promising applications of graphene nanotubes in sustainable textile processes. Frontier molecular orbitals (FMOs) and global reactivity descriptors serve as key tools for understanding the stability and chemical reactivity of compounds. These tools were used to calculate FMOs and electronic parameters of compounds 1 and 2 at the B3LYP/6‐31G(d) level of theory. The study examined the highest occupied molecular orbital (HOMO)‐lowest unoccupied molecular orbital (LUMO) energy gap, which provides insights into molecular stability and reactivity. Various physical properties were derived from these calculations, including electron affinity (EA) and ionization potential (IP) to LUMO and HOMO energies. Compound 2 emerged as the most efficient electron donor, possessing the highest HOMO energy, while compound 1 excelled as the best electron acceptor with the highest LUMO energy.

Engineering high-brightness and long-lived organic room-temperature phosphorescence via systematic molecular design.

We report a systematic molecular design in BF2bdk-based afterglow emitters with photoluminescence quantum yields up to 46.3% and lifetimes around 1 s. Suitable excited-state types, diverse excited state species, relatively small singlet-triplet energy gaps and strong dipole-dipole interactions are critical in determining the afterglow properties.

A DFT Analysis of Structural and Electronic Features of [Mo(CO)6‐n(SiX)n] (n=1, 2 and 3, and X=O, S, Se and Te) Complexes

AbstractDFT was used to analyze the molecular and electronic structures of the mono, di‐ and tri‐substituted isomers of [Mo(CO)6‐n(SiX)n] (where, X=O, S, Se, Te) and they were compared to the Mo(CO)6 complex. The total energy of all the complexes indicates that the trans isomer is slightly more stable than the cis isomer, but the stability of the fac and mer isomers is comparable. The HOMO‐LUMO energy gap of the complexes was determined and it indicated that the energy gap of the newly designed complexes is smaller than that of the parent complex Mo(CO)6 (1), ranging from 3.45–5.08 eV for the complexes 2–21. The FMO analysis of 2–21 showed that they are more reactive than complex 1. Insights on the bonding nature of these complexes are provided by the NPA, NBO, and EDA studies. The bond contribution from the Si atom in the Mo−Si bond is greater than that from the Mo atom, based on the NBO study. However, the C atom contributes more to the Mo−CO bond as well. Atomic charges on the Mo atom have a higher negative charge and the Si atom shows a positive charge in all the complexes. This study provides valuable information about the isolobal and isoelectronic nature of different substitutions of Si−X bonds at different positions instead of CO molecule in [Mo(CO)6].

Investigation of thermally induced surface composition and morphology variation of magnetron sputtered Sb2Se3 absorber layer for thin film solar cells

One of the most promising semiconductor materials for the development of sustainable thin-film solar cell technology is antimony selenide (Sb2Se3). Its excellent optical and electrical properties have drawn attention lately for potential application in thin-film solar cells. In this study, Sb2Se3 films deposited using the direct current (DC) magnetron sputtering technique have been subjected to a post-annealing process without an extra selenium supply at temperatures between 150 and 450 °C. Without an extra selenium supply, the impact of post-annealing temperature on the surface composition as well as the physical properties of the fabricated films was investigated. The overall evaluations revealed that the post-annealing temperature is highly efficient in altering the physical properties of the Sb2Se3 absorber thin films. We further observed that the post-annealing process improved the crystallization and the heat treatment temperature quite affected preferential orientation. The surface morphology of films exhibited structural deformation at high post-annealing temperatures (> 350 °C). According to optical and electrical characterizations, respectively, the optical energy gap and the resistivity of Sb2Se3 films reduced with an increment in the post-annealing temperature. Based on the XPS result, the variation in temperature of post-annealing led to a change in the surface composition of the films. The findings on the growth of Sb2Se3 thin films indicate the existence of an intermediate growth temperature that permits the growth of Sb2Se3 films to be optimized. The study’s conclusions can serve as a guide to the growth of Sb2Se3 thin films with the desired crystallinity, surface morphology, and composition for thin film solar cell applications.

Effect of Electron-Donating Substituents and an Electric Field on the ΔEST of Selected Imidazopyridine Derivatives: A DFT Study.

A series of thermally activated delayed fluorescent (TADF) molecules having an imidazopyridine acceptor, a benzene linker, and a 9,9-dimethyl-9,10-dihydroacridine donor are designed and examined using a quantum chemical approach. The above framework spatially separates the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), minimizing their overlap, ultimately resulting in a reduced energy gap between the excited singlet and triplet states (ΔEST). The impact of electron-donating substituents (-Me, -Et, -t-Bu, -OMe, and -NMe2) on the donor moiety of the parent molecule 2-(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)imidazo[1,2-a]pyridine-3,6-dicarbonitrile (Ac-CNImPy) is investigated. The calculated results revealed that for a given substituent, the para-substituted derivatives exhibit relatively less ΔEST, compared to that of the respective ortho- and meta derivatives. The value of ΔEST decreased with an increase in the electron-donating capacity of the substituent. Additionally, the ΔEST of the disubstituted derivatives is found to be less than that for the monosubstituted derivatives. The charge transport studies revealed that molecules with strong electron-donating substituents act as electron transporters. The effect of an external electric field (EEF) on ΔEST of the parent molecule Ac-CNIMPY and its derivative is also examined and revealed that the ΔEST can be further reduced by applying an electric field of appropriate strength in a direction perpendicular to the dipole moment of the molecule and in the plane of the acceptor moiety.

Comparative study of structural, opto-electronic properties of Cs2TiX6-based single halide double perovskite solar cells: computational and experimental approach

This research work represents a comparative study of the structural, optical, and electronic properties of Cs2TiX6 single halide perovskite solar cell (PSC). The entire work has been carried out by experimental work under ambient conditions and followed by the DFT method. Absorbing material structural parameters (lattice constant, shape), and band gap energy can be easily estimated from the DFT approach which can be compared with the result of experimental work. Our study shows Cs2TiBr6 PSC has better band gap energy of 1.80 eV (numerically) and 1.82 eV (experimentally), open circuit voltage 0.58 V, short circuit current 2.55 mA cm−2 for the photovoltaic application. Also, the higher Zeta potential value of Cs2TiBr6 PSC indicates that it has better material stability and is less volatile compared to Cs2TiI6, Cs2TiCl6, and Cs2TiF6 PSCs. TEM images and the SAED pattern of the active layers show a higher degree of crystallite nature of the PSCs.On the other look, investigated PSC materials Cs2TiBr6, Cs2TiI6, Cs2TiCl6, and Cs2TiF6 have shown visible light emission edges at 358 nm, 375 nm, 363 nm, 735 nm wavelength, and the optical performance area of the Cs2TiBr6, Cs2TiI6, Cs2TiCl6, Cs2TiF6 samples is recorded up to 700 nm, 760 nm, 540 nm, and 660 nm wavelength, respectively.

Assessing the electromagnetic shielding effectiveness of coconut coir composites with varying iron particle concentrations

This study investigates the electromagnetic shielding effectiveness of Coconut Coir-based Porous Carbon (CCPC) composites with varying iron (Fe) particle concentrations, specifically focusing on four different weight ratios of CCPC/Fe-80, CCPC/Fe-60, CCPC/Fe-40, and CCPC/Fe-20. The novelty of this work lies in the use of sustainable coconut coir as a base material, emphasizing its eco-friendly and cost-effective attributes for Electromagnetic interference (EMI) shielding applications. The significance of varying iron particle concentrations is highlighted to optimize electromagnetic shielding effectiveness. Comprehensive analyses were conducted on these composites. X-Ray Diffraction (XRD) analysis confirmed the presence of crystalline Fe particles and amorphous carbon, with crystalline sizes determined via Williamson-Hall (W-H) plot, Scherrer Equation, and Strain Size Plot (SSP) ranging from 17.33 nm to 18.01 nm for the former. Raman spectroscopy revealed distinctive D and G bands, with intensity ratios indicating a slight increase in structural disorder with higher Fe content. UV-Visualization spectroscopy demonstrated distinct absorption peaks, with higher Fe content resulting in more pronounced absorbance and lower band gap energies. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analyses provided detailed insights into the material's microstructure and elemental composition, confirming the successful integration of Fe particles within the porous carbon matrix. Vector Network Analyzer (VNA) testing measured the reflection loss (RL), showing values in the range of −26.4 dB to −20.2 dB, for 2 mm thick samples, corresponding to electromagnetic wave attenuation of over 99%. These results underscore the potential of CCPC/Fe composites, particularly in applications requiring effective Electromagnetic (EM) wave attenuation. This research offers a sustainable and cost-effective solution, contributing significantly to the field of materials science by enhancing electromagnetic compatibility in various technological applications.

Why Does the Optimal Tuning Method of the Range Separation Parameter of a Long-Range Corrected Density Functional Fail in Intramolecular Charge Transfer Excitation Calculations?

We performed intra- and intermolecular charge transfer (CT) excitation energy calculations of (a) conjugated carbon chain [H2N–(CH=CH)n–X] and (b) its equidistant H2NH∙∙∙HX (n = 2~8) with various electron acceptors (X = NH2, OH, Cl, CHO, CN, and NO2) using EOM-CCSD, time-dependent (TD) Hartree–Fock (HF) and various density functional theory (DFT) functionals, such as BLYP, B3LYP, long-range corrected (LC) DFT, and LC-DFT with an optimally tuned (OT) range separation parameter (µ) using Koopman’s theorem to investigate the effect of the electron-withdrawing (or -donating) strength of end-capped functional group (X) and CT distance (R) on intra- and intermolecular CT excitation energies. As the electron-withdrawing strength of X increases, both intra- and intermolecular CT excitation energies tend to decrease, since energy gaps between orbitals corresponding to CT excitations (e.g., HOMO and LUMO) decrease. However, the effect of the electron-withdrawing group on intramolecular CT excitation energy is negligible (at most 0.5 eV). OT-LC-DFT shows accurate intermolecular CT excitation energy, but worse results in intramolecular CT excitation energy than LC-DFT with the default µ value (0.47). Therefore, we conclude that the optimal tuning method is not effective in predicting intramolecular CT excitation energy. While intermolecular CT excitation energy has excitonic binding energy with asymptotic behavior to CT distance that is not affected by the choice of range separation parameter, intramolecular CT excitation energy is affected by orbital relaxation energy, which strongly depends on the choice of range separation parameter, which makes the OT method of range separation parameter ineffective in predicting intramolecular CT excitation energy as well as local excitation with high accuracy.

Investigating the antioxidant potential and mechanism of a hydrazide bioactive component of garlic: insights from density functional theory calculations, drug-likeness and molecular docking studies.

Glutathione remains one of the most efficient antioxidant compounds in living systems, and the biological abilities of hydrazides have been well documented in literature. This study highlights the phytochemical constituents of garlic and the separation of the bioactive benzoic acid, 4-chloro- 1-(4-methoxyphenyl) hydrazide (BA4C) using gas chromatography-mass spectroscopy (GC-MS) technique. Preliminary phytochemical screening reveals the presence of alkaloids, saponins, flavonoids, tannins, terpenoids, steroids and phenols. Computationally, compound BA4C was optimized using the B3LYP/aug-cc-PVDZ DFT method. Spectroscopic studies of the compound involved analysis of the vibrational FT-IR frequencies and the modes of vibrations. Frontier molecular orbitals analysis records an energy gap of 4.3391eV; NBO studies reveal that the compound has strong perturbation energies of 246kcal/mol and 269kcal/mol among its intramolecular interactions such as *C12 - C13 to *C14 - C15 and *C11 - C16 to *C14 - C15, respectively. According to the visualization of non-covalent interactions, steric repulsions were observed at the core of the phenyl and benzene rings. However, other regions of the compound depict a significant balance of forces between steric repulsions and van der Waals forces. To significantly deduce the reducing power of compound BA4C, electrons were found to be highly localized at the methoxy and hydrazide moieties significantly implying their propensity to donate electrons to oxidized systems. Furthermore, ADMET analysis reveals that the compound has two hydrogen donors. Most significantly, the compound binds to NADPH dehydrogenase (5V4P) and glutathione reductase (1XAN) with binding energies of - 6.0kcal/mol and - 8.0kcal/mol showing considerable favourable binding feasibility as well as forming plural hydrogen bonds with the amino acid residues. Notably, BA4C was bonded at the active site of 1XAN, which implies the ability of the compound for the reduction of oxidized glutathione.

A facile route derived solar selective nickel-cobalt oxide thin films via spraying process

Abstract This work focuses on understanding the role of annealing temperature on the solar selective performance of nickel-cobalt oxide thin films successfully sprayed onto Al substrates using the spray pyrolysis technique. The synthesized nickel-cobalt oxide thin films (~ 725± 20 nm thick) were post annealed at (400, 500 and 600) °C. The XRD and FESEM outcomes appeared high crystalline quality with crystal grains in the range of (27 – 52) nm and improved surface morphology for the sprayed thin films. The optical properties reflect solar absorptance ~ (85.2 %) and the thermal emittance ~ (4.45 %). The hardness and the Young’s modulus were (19.1 GPa) and (104 GPa) respectively. The aforementioned results are for the film annealed at 600 °C. The prepared and post annealed nickel-cobalt oxide thin films show band gap energies in the range of (1.15 – 1.38) eV. The nickel-cobalt oxide thin films also possess excellent thermal stability at higher temperature which makes them interesting candidate for solar absorbing and thermal collector applications.

Mechanical and Electronic properties of ZnIV1-xIVxN2 (IV=Si, Ge and Sn) with varied concentrations: First-principles calculations

This study employed first-principles calculations to explore the mechanical and electronic properties of ZnIV1-xIVxN2 (IV=Si, Ge, Sn) at varying concentrations. Adding Si enhances elasticity, brittleness, and hardness by reinforcing Zn/IV-N ionic bonding, while Sn addition diminishes these properties. Electronic band structures indicate that antibonding states mostly arise from IV p orbitals hybridized with N s orbitals, impacting energy bandgaps. Bader charge analysis confirms enhanced ionic bonding with Si addition and weakened bonding with Sn, consistent with IV ion sizes and charges influencing bond lengths and hybridization strengths. Our study suggests that the ductility of ZnIVN2 can be improved while maintaining its UV absorption properties by using ZnGe1-xSixN2 with x = 0.25,0.50 and ZnSi1-xSnxN2 with x = 0.25, which is dynamically stable. These compounds exhibit energy gaps of 3.29–3.83 eV and 3.52 eV, respectively. In ZnGe1-xSixN2, the energy gap ranges from 4.62 to 2.82 eV, while in ZnGe1-xSnxN2, it spans from 1.16 to 2.82 eV. For ZnSi1-xSnxN2, the energy gap extends from 4.62 to 1.16 eV. The Sn p + N s hybridization is weakest compared to the Ge p + N s and Si p + N s hybridizations, respectively, resulting in a lower energy antibonding state for ZnSnN2 > ZnGeN2 > ZnSiN2. This leads to the observed bandgap differences.

Preparation, Characterization, In Vitro Biological Evaluation, DFT Calculations, and Molecular Docking Investigations of 1H-Imidazole-2-Carboxylic acid and Histidine-Based Mixed-Ligand Complexes.

Mixed-ligand complexes incorporating 1H-Imidazole-2-Carboxylic acid (IMCA) and Histidine (LHIS) show promise for biomedical and biotechnological applications. This study synthesizes and characterizes FeIMCALHIS, CoIMCALHIS, and NiIMCALHIS coordination compounds using metal chloride salts (FeCl3.6H2O, CoCl2.6H2O, NiCl2.6H2O) in ethanolic solutions. The complexes are characterized by spectroscopic methods (IR, UV-vis, and mass spectra), elemental analysis, conductivity, magnetic, and thermal analysis. Molar conductivity indicates their non-electrolytic nature. UV-vis spectra reveal absorption bands with pathochromic shifts, and electronic spectra show characteristic metal-ligand transitions, indicating their structural configuration and coordination geometry. 3D geometry optimization shows six-coordination around Fe(III) and Co(II) in FeIMCALHIS and CoIMCALHIS, and four-coordination around Ni(II) in NiIMCALHIS. Analysis of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) suggests decreased electron donation ability upon coordination. Electronic structure parameters (HOMO, LUMO, ionization potential, energy gap, electron affinity, chemical potentials, and electronegativity) provide further insights into stability and reactivity. The metal complexes exhibit enhanced antimicrobial, antioxidant, and anti-inflammatory activity compared to individual ligands, with FeIMCALHIS showing notable antimicrobial activity. Molecular docking analysis reveals strong binding interactions with target proteins, highlighting their potential therapeutic applications.

Green synthesised Mn3O4 and poly (o-phenylenediamine) for antimicrobial textile-based supercapacitor applications

The advancement of wearable supercapacitors (SCs) has recently garnered a lot of attention owing to their ease of fabrication into textiles, low cost, long cycle life, fast charging and discharging, high efficiency, and ability to bridge the energy and power gap between conventional capacitors and batteries. The present study focuses on the development of wearable textile-based SC electrodes using green-synthesised manganese oxide nanoparticles functionalised on poly(o-phenylenediamine) reinforced to a polymer nanocomposite. The prepared nanocomposite was characterized using spectroscopic techniques such as UV-visible spectroscopy, Fourier transform infrared spectroscopy, x-ray diffraction studies, and scanning electron microscopy to validate the incorporation of metal oxide nanoparticles into the polymer matrix. The thermal properties were studied using thermogravimetric analysis and differential scanning calorimetry. The electrochemical performance of the bare polymer and the nanocomposite was evaluated using cyclic voltammetry, galvanostatic charge-discharge, and impedance spectroscopy techniques. An impressive specific capacitance of 213 Fg-1was achieved at a current density of 1 Ag-1for the polymer nanocomposite and even after 1000 cycles a capacitance retention of 89% was observed. Enhanced antimicrobial activity was also observed for the nanocomposite against both gram-negative and gram-positive bacteria. Based on these attributes, the fabricated device can be used as an efficient antimicrobial wearable SC.

Divergent features of collective gravitational quantum excitations

In this research, we study different aspects of collective gravitational quantum excitations in the framework of the quantum multistream model. The energy dispersion of collective electrostatic (plasmon) and gravitational excitations or as we call gravity quasiparticle (GQ) are derived using the nonrelativistic and relativistic models and many parameters such as the effective mass, phase, and group speed of quasiparticle excitations are studied, in detail. It is shown that, unlike plasmons with a forbidden energy gap, all positive and negative energy values are allowed for GQs. However, unlike plasmon with a dual-tone nature of collective excitations, the GQs are found to be single-tone with either wave-like or particle-like oscillations being strongly damped. The linear phase-space evolution of GQs indicates that they evolve similarly to the classical system of particles in the center of the mass frame in which the force due to self-consistent gravitational potential plays the role of interparticle forces. It is shown that the damping of wavelike or particle-like excitations in GQ energy dispersion leads to three distinct phenomena of gravitational expansion (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E>0$$\\end{document}), stable matter (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E=0$$\\end{document}) and gravitational collapse (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E<0$$\\end{document}), respectively. The Hubble-Lemaitre-like relation is obtained from the generalized probability current for GQs. The quantum gravitational interference effect is also studied.

Microscopic analysis of relaxation behavior in nonlinear optical conductivity of graphene

Abstract We produce a general formalism to study the interband dynamical optical conductivity in the nonlinear regime of graphene in the presence of a quantum bath comprising phonons and electrons. When a quantum solid of graphene is subjected to an intense electric field in the optical frequency range, the observation of a nonlinear response is facilitated by formulating a quantum master equation of the density operator associated with the Hamiltonian encapsulated in a spin-boson model of dissipative quantum statistical mechanics. Our results reveal the nonlinear steady-state regime's population inversion and decoherence. The present method enables us to investigate further the nonlinear interband optical conductivity of pristine and gapped graphene characterized by a single dimensionless parameter at finite temperatures. The effects of different bath spectra for phonons and electrons are examined in detail. {\color{red} The temperature dependence of conductivity reveals that changing temperature can enable us to make the transition from the linear to the nonlinear regime for fixed optical field parameters.} Interestingly, a fascinating switching-like behavior is observed for the low-temperature optical conductivity of the gapped graphene while we vary the energy gap as well as the frequency of the externally applied field. Although our general formulation can address a variety of nonequilibrium responses of the two-band system, it also facilitates a connection with the phenomenological modeling of nonlinear optical conductivity.

Synergistic charge-transfer dynamics of novel D-D-A-π-A framework containing indoline-benzo[d][1,2,3]thiadiazole based push-pull sensitizers: from structural engineering to performance metrics in photovoltaic solar cells.

Dye-sensitized solar cells (DSSCs) present a convincing substitute for conventional silicon-based solar cells because of their possible lower manufacturing costs and versatile uses. Electron injection and dye regeneration processes are important in meeting the need for photosensitizers with improved efficiency and stability. Aimed at enhancing the performance and efficiency of DSSCs, this study focuses on the structural engineering to performance metrics of novel indoline-benzo[d][1,2,3]thiadiazole based push-pull sensitizers (LHZ1 to LHZ9) with D-D-A-π-A framework. The current study provides insights into the photovoltaic and optoelectronic properties of the investigated dyes, which are significantly influenced by the modification of auxiliary donors (D), internal acceptors with thiophene as a spacer, and cyanoacrylic acid (A) as the terminal acceptor. These modifications enhance rapid charge transfer among the dyes, highlighting the critical role of dye-semiconductor interactions. The suitability of developed sensitizers for DSSCs applications is confirmed by executing quantum methods like NBO, TDM, FMO, DOS, Eb, ΔGreg, ΔGinject, VRP, and ICT parameters qCT (e-), DCT ( ), H index ( ), ∆( ), t index ( ), and μCT (D). All of the investigated dyes have HOMO levels lower than the electrode I-/I3-'s redox potential (-4.8 eV) and LUMO values that are appropriately higher than the conduction band of TiO2 (-4.0 eV). The novel dyes showed a closing of the energy gap (2.38-1.84 eV). The LHZ7 and LHZ8 molecules with the lowest Eg (1.97 eV and 1.84 eV) demonstrated the highest absorption (up to 746 nm > 402 nm for LHZ), which was caused by the insertion effect of varied donors and internal acceptors. Almost all photosensitizers appeared with remarkable properties, i.e., red-shifted absorption maxima (746 nm), lowest Ex (1.66 eV), Eb (0.02 eV), and highest values of LHE (0.958). The TDM analysis revealed high charge density on HOMO of donor and LUMO of acceptors in designed dyes. DOS analysis revealed that the donor parts of the molecules delocalized the highest occupied molecular orbitals of dye particles. The electronic properties predicted by the NBO analysis showed that donor groups donate high and faster transfer of charge, and internal acceptor groups rapidly accept them. The electron injection (ΔGinject) and dye regeneration (ΔGreg) analysis of photosensitizers attached with TiO2 proved efficient charge transfer properties from the donor of newly designed dyes onto the conduction band of TiO2. This study, also supported by the thermodynamic stability of dyes with negative values of Gibbs free energy, revealed that the performance of the designed dyes is augmented by modifying the donor and internal acceptors of the reference photosensitizer for effective application in the experimental community. All of the dyes are suitable for DSSCs based on the calculated parameters. Still, the LHZ9 dye proved proficient in applying dye-sensitized solar cells due to its remarkable properties, i.e., lowest gap and red-shifted absorption maxima.

Using the Plasma Jet Method to Create Zinc Nanoparticles and Study Their Structural and Optical Properties as an NH3 Gas Sensor

In this work, zinc nanoparticles were prepared using the low-temperature plasma method at different times 3 min, 5 min, 7 min, 9 min, where the initial reactions of zinc lead to the formation of nanoparticles. The metal interacts with the ionized plasma under different conditions and may turn into an oxide such as exposing the sample to air and raising the temperature of the solution a few degrees as a result of high voltage and within a certain range. The atmospheric pressure plasma system acts as the cathode, while the zinc metal strip acts as the anode. A series of techniques were used, including the use of X-ray diffraction (XRD), ultraviolet-visible spectroscopy and scanning electron microscopy (FESEM). The X-ray diffraction results showed that the samples have polycrystalline structures with hexagonal and cubic structures with a time difference, and the X-ray diffraction results showed the conversion of zinc particles into zinc oxides. FESEM images reveal particle size and shape. The ZnO nanoparticles prepared by the mentioned method seem to form different nanoshapes such as starfish and mushroom nanoparticles. The UV-visible results showed that the samples had an energy gap of about 3.4 eV at a time of 3 min, and this value decreases with increasing reaction time. The appearance of zinc oxides increases gradually with the passage of time. These results provide credibility for the fabrication of ZnO nanostructures for use in future gas sensing applications, despite the inhomogeneity of particle size among ZnO particles, the sensor was also fabricated to detect nitrogen gas (NH3) with different concentrations (17.25 ppm, 46.38 ppm, 78.58 ppm). at room temperature. The ZnO sample showed the highest sensitivity (88.1%) at 7 min. The sensitivity showed different results and increased with reaction time and gas concentration. However, response and recovery time are moderate and decrease as reaction time increases.

Indirect-to-direct bandgap transition in GaP semiconductors through quantum shell formation on ZnS nanocrystals

Although GaP, a III-V compound semiconductor, has been extensively utilized in the optoelectronic industry for decades as a traditional material, the inherent indirect bandgap nature of GaP limits its efficiency. Here, we demonstrate an indirect-to-direct bandgap transition of GaP through the formation of quantum shells on the surface of ZnS nanocrystals. The ZnS/GaP quantum shell with a reverse-type I heterojunction, consisting of a monolayer-thin GaP shell grown atop a ZnS core, exhibits a record-high photoluminescence quantum yield of 45.4% in the violet emission range (wavelength = 409 nm), validating its direct bandgap nature. Density functional theory calculations further reveal that ZnS nanocrystals, as the growth platform for GaP quantum shells, play a crucial role in the direct bandgap formation through hybridization of electronic states with GaP. These findings suggest potential for achieving direct bandgaps in compounds that are constrained by their inherent indirect energy gaps, offering a strategy for tailoring energy structures to significantly improve efficiencies in optoelectronics and photovoltaics.