Search Results (2,886)

Angle-resolved photoemission spectroscopy (ARPES) clearly resolves surface-localized (SL) states, yet conventional density functional theory (DFT) band structures from slab calculations do not readily distinguish weakly confined SL states on surfaces such as Al(001), as traditional layer-threshold criteria fail for surfaces with long surface-state decay lengths. We establish a dual-criterion scheme using the surface ratio R and the localization integral L weighted by the inelastic mean free path (IMFP) to quantitatively distinguish SL states: R quantifies the surface-projected charge fraction, while L incorporates the photoelectron IMFP to mimic ARPES surface sensitivity, both evaluated within a fully converged 81-layer Al(001) slab that eliminates artificial inter-surface coupling. Band structures color-coded by R and L intuitively highlight SL states as bright yellow-white bands against red bulk backgrounds. Our calculations show that continuum SL features arise from multi-band hybridization (sharp surface resonances). Notably, R and L alone cannot separate absolute surface states from resonances. All DFT calculations were performed using the PBEsol exchange-correlation functional within the GGA framework, the PAW formalism, and an 81-layer Al(001) slab model. This work reveals the electronic nature of surface features on Al(001) and provides a quantitative SL-state identification tool that is conceptually transferable to other crystalline surfaces. Full article

The development of lightweight multifunctional materials integrating electromagnetic interference (EMI) shielding, Joule heating and flame retardancy is highly demanded for advanced electronics and aerospace systems. Herein, we fabricate graphene/Fe₃O₄@hollow glass microsphere (G/Fe₃O₄@HGM) composite foam with an ultralow density of 0.36 g/cm⁻³. The porous structure synergizes graphene’s conductivity, Fe₃O₄’s magnetism and HGM’s low thermal conductivity to optimize impedance matching. The foam delivers absorption-dominated EMI shielding with a maximum X-band shielding effectiveness (SE) of 60.1 dB and an average absorption coefficient of 0.56, which effectively suppresses secondary electromagnetic reflection pollution. The composite exhibits stable voltage-controllable Joule heating: the 25 wt% Fe₃O₄@HGM sample reaches 91.3 °C at 16 V, enabling rapid de-icing within 200 s and stable thermal maintenance at −20 °C. Flame tests confirm no combustion or structural collapse under open flame. This work provides a simple fabrication strategy for lightweight multifunctional materials applicable to aerospace stealth, electronic thermal management and anti-icing systems. Full article

This study presents a comprehensive investigation of the structural, morphological, and optical properties of aluminum phthalocyanine (AlPc) and silicon phthalocyanine (SiPc) thin films prepared by the close space sublimation (CSS) method, deposited at different evaporator temperatures of 350 °C, 400 °C, and 450 °C, including heterostructures incorporating an indium tin oxide (ITO) layer. Scanning electron microscopy revealed a clear temperature-dependent evolution of surface morphology, with both materials transitioning from isolated crystallites to dense, highly crystalline films. SiPc exhibited higher nucleation density and earlier film densification, while AlPc showed more pronounced grain growth at elevated temperatures, accompanied by crack formation due to internal stress. Optical absorption spectra indicated a red shift in absorption maxima with increasing deposition temperature, associated with improved crystallinity and reduced defect density. The presence of ITO significantly modified the optical response, introducing additional absorption features in the near-infrared region due to interference effects and free-carrier contributions. Fluorescence measurements revealed enhanced emission intensity with increasing temperature for AlPc, while SiPc showed weaker emission overall. The incorporation of ITO led to substantial fluorescence enhancement and the appearance of additional near-infrared emission bands, highlighting the importance of interface engineering. Transmittance spectra demonstrated that ITO-based heterostructures provide a balance between transparency and absorption, with selective attenuation in the 600–800 nm range, enabling band-stop filter behavior. Raman analysis revealed opposite temperature-dependent trends: increasing structural order in AlPc and gradual disorder in SiPc. X-ray diffraction confirmed the crystalline nature of both materials, showing temperature-induced improvements in crystallinity and crystallite size, as well as distinct differences in molecular packing and preferred orientation. These results demonstrate the potential of AlPc and SiPc thin films as functional optical materials with tunable structural and optical properties. Full article

A comprehensive beyond density functional theory study of the structural, energetic, and electronic properties of the technologically most relevant SiC polytypes 3C, 2H, 4H, and 6H-SiC, together with the single Shockley-type stacking fault (1SSF or 31SSF) in 4H-SiC, was conducted. Lattice constants computed at the PBEsol and HSE06 level match experimental values within 0.1% accuracy. Total energies evaluated at the random-phase approximation level yield a physically consistent hierarchy of polytypes with 3C-SiC as the most stable phase, which is in agreement with low-temperature experimental results. Quasiparticle band gaps computed with both the single-shot G0W0@PBE and the partially self-consistent GW0@PBE formulations quantitatively match well with the experimental values. The band structure of 31SSF reveals fault-induced sub-gap band splitting at the M point of 0.21 eV at the GGA level, which increases to 0.28 eV upon G0W0 correction. To our knowledge, this provides the first GW-level treatment of the 31SSF electronic structure in 4H-SiC. These results collectively provide a many-body perturbation theory (MBPT) level reference dataset for SiC polytypes and the commonly found stacking fault in 4H-SiC. Full article

Two-dimensional transition metal dichalcogenides (TMDCs) require highly controllable and scalable synthesis methods for successful integration into next-generation optoelectronic technologies. This study presents a modified two-step thermally assisted conversion approach for synthesizing 2D tungsten diselenide (WSe₂) by introducing an intermediate UV–ozone treatment. Magnetron-sputtered tungsten films are exposed to UV–ozone, converting the precursor into a uniform, dense layer of amorphous tungsten trioxide (WO₃) prior to the selenization process via chemical vapor deposition. X-ray photoelectron spectroscopy and Raman spectroscopy confirm the complete phase transition from the oxidized precursor to the 2H-WSe₂ crystal lattice. Morphological evaluations utilizing transmission electron microscopy and atomic force microscopy demonstrate that the ozonated precursors yield highly uniform, triangular flakes exceeding 5 µm in lateral size, effectively eliminating the unreacted WO₃ phases observed in untreated samples. Furthermore, the intermediate oxidation step finetunes the electronic band structure; the resulting WSe₂ exhibits an enhanced p-type character with a valence band maximum shift to 0.35 eV, a tuning attributed to residual oxygen doping. Optical characterizations reveal significantly improved transmittance in the visible spectrum, accompanied by excitonic absorption shifts indicative of reduced layer dimensionality. This intermediate ozonation strategy provides a highly effective pathway for producing high-quality WSe₂ nanosheets with tailored structural and optoelectronic properties. Full article

In the present work, thin TiO₂ films were obtained by the sol–gel spin-coating method on glass and ITO-covered glass substrates. The crystallization evolution of the thin films was studied by the X-ray Diffraction (XRD) technique. The results indicate that the films’ crystalline structure was greatly affected by substrate type. X-ray photoelectron spectroscopy (XPS) revealed the chemical states of the TiO₂ films and proved the formation of TiO₂ on ITO substrates. Field Emission Scanning Electron Microscopy (FESEM) showed that the TiO₂ films deposited on the ITO glass possessed a uniform and homogeneous surface morphology. The influence of optical properties (transmittance, reflectance, and optical band gap) on substrate type, the number of layers and annealing temperatures was determined. Spectroscopic data confirmed high transparency of the TiO₂ films obtained on ITO substrates as the transmittance in the visible spectral range was close to 85%. The obtained results reveal that thin TiO₂ films on ITO substrates can be an excellent candidate for photovoltaic and optoelectronic applications. Full article

Metal phthalocyanines (MPcs) possess outstanding thermal stability and versatile optical, catalytic, and semiconducting properties. Here, the effects of central metal ions, peripheral substituents, and substitution positions on the vibrational properties of MPcs were systematically investigated using Raman spectroscopy. The characteristic Raman band near 1530 cm⁻¹ exhibits systematic shifts with changing metal centers (NiPc > CoPc > CuPc > ZnPc), reflecting differences in metal-ligand interactions and electronic structure. Peripheral substituents and their positions further influence the Raman response through electronic effects, vibrational coupling, and resonance enhancement. In particular, four-substituted MPcs show greater Raman shifts than their three-substituted counterparts. The results reveal clear correlations between molecular structure and Raman characteristics, providing a useful framework for understanding and designing functional phthalocyanine-based materials. Full article

Metal/semiconductor heterojunctions for hot carrier photodetection have garnered significant attention. However, enhancing the quantum efficiency remains a critical challenge. Introducing lattice strain into metallic materials offers a viable approach to enhance the performance of TiN/TiO₂ hot electron photodetectors by effectively modulating their electronic structure. Herein, we investigate how strain influences the electronic structure of TiN and consequently affects the generation, transport, and injection processes of hot carriers using first-principles calculations. Subsequently, we evaluate the injection efficiency and responsivity of the TiN/TiO₂ photodetector through Monte Carlo simulations. We find that compressive strain renders the energy bands more delocalized and reduces the density of states DOS, leading to diminished hot electron generation, especially in the high-energy region above the Schottky barrier. This reduction suppresses electron–electron scattering, thereby increasing the hot electron lifetime and mean free path. Consequently, the hot electron injection efficiency is enhanced, ultimately improving the responsivity of TiN/TiO₂ photodetector by a factor of 1.3–2.4 over the incident photon energy range of 0.1–3 eV. Full article

This study examines the effects of nearly six years of outdoor storage on the chemical, thermal, structural, micromorphological, and mechanical properties of European hornbeam (Carpinus betulus L.) and Oriental beech (Fagus orientalis Lipsky) wood. Differences between fresh (control) and stored samples were characterised using attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, thermogravimetric/derivative thermogravimetric analysis (TGA/DTG), X-ray diffraction (XRD), scanning electron microscopy (SEM), and testing of compressive strength parallel to the grain. ATR-FTIR analysis points to alterations in carbohydrate- and lignin-related absorption bands after storage. TGA/DTG profiles suggest that hornbeam largely maintains its thermal degradation behaviour, whereas beech exhibits more pronounced shifts in thermal stability. XRD results indicate a reduction in crystallinity index (CrI) for both species. SEM observations of beech wood revealed filamentous structures within cell lumens, together with localised cell-wall disruption and microcracks, indicating more extensive microstructural modification than in hornbeam. Mechanical testing shows significant reductions in modulus of elasticity (MOE), with decreases of 32.2% in hornbeam and 28.4% in beech. Statistical evaluation confirms the significance and effect sizes of these changes. Overall, the findings demonstrate that long-term outdoor storage induces species-dependent degradation across molecular, microstructural, and macroscopic scales, ultimately compromising wood performance. Full article

In this study, zinc-doped magnesium ferrite (Zn_x-Mg_1−xFe₂O₄) nanoparticles were synthesized using a facile combustion method and investigated for their electrochemical sensing and photocatalytic applications. The structural, morphological, and optical properties of the synthesized nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDAX), Fourier-transform infrared spectroscopy (FTIR), Energy band gap (Eg) and UV-Vis spectroscopy. The synthesized Zn–MgFe₂O₄ nanoparticles exhibited crystallite sizes ranging from 18.7 to 27.9 nm with an optical band gap of 1.86–1.89 eV. The catalyst achieved degradation efficiencies of 78% for Eriochrome Black T and 85% for Methyl Orange within 120 min, while the electrochemical sensor exhibited excellent linearity toward HgCl₂ detection (R² = 0.99664), demonstrating the multifunctional capability of the synthesized nanostructure. The synergistic effects of Zn doping contributed to enhanced electrical conductivity, catalytic activity, and structural stability. The novelty of this work lies in the development of combustion-synthesized Zn–MgFe₂O₄ nanoparticles as a multifunctional material capable of simultaneously achieving efficient photocatalytic degradation of organic dyes and sensitive electrochemical detection of mercury chloride using a simple and scalable synthesis route. These findings demonstrate that Zn–MgFe₂O₄ nanoparticles hold significant potential for integrated environmental remediation and electrochemical sensing applications. Full article

The positional arrangement of BN and CC units in B₆C₆N₆ cyclic nanorings profoundly influences their stability, electronic structure, optical response, and reactivity. Here, we comparatively investigate eight positional isomers (C1–C8) using DFT and TD-DFT calculations. Among C1–C8, C1 is the most stable, and C8 is the most unstable in the range of 200–1000 K. Their relative stability is governed by B-N charge separation, homonuclear B-B and N-N defects (charge repulsion), and bond-angle distortion (ring tension). The HOMO–LUMO gaps range from 4.40 eV (C3) to 8.45 eV (C2), indicating distinct kinetic stability. Aromaticity analysis reveals that all isomers are nonaromatic. In the gas phase, the lowest-energy absorption bands of C1 and C3 are located at about 429 nm and 606 nm, respectively. Due to different transition mechanisms, namely locally excited (LE) for the former and charge-transfer (CT) for the latter, solvent polarity has dramatically different influence on these two absorption bands. Compared to their positions in the gas phase, these absorption bands are blue-shifted about 20 nm and 220 nm in water, respectively. Reactivity analysis identifies the B-B bond in C7 as the strongest electrophilic site (LEAE = −2.93 eV), with the surrounding framework serving as nucleophilic domains, endowing C7 with the strongest bifunctional reactivity. This work establishes a comprehensive structure–property map for B₆C₆N₆ isomers, providing guidance for designing BCN-based nanorings for catalysis, molecular recognition, and optoelectronics. Full article

Phenolic acids exhibit structure-dependent vibrational responses governed by aromatic substitution, π-conjugation, oxygenated functional groups, and molecular environment. In this work, p-coumaric, caffeic, trans-ferulic, and gallic acids were investigated through an integrated experimental Raman, density functional theory (DFT), and chemometric approach to establish molecular relationships between hydroxylation, methoxylation, conjugation, and Raman spectral behavior. Raman spectra were recorded in the solid state and in an ethanol/water (1:1, v/v) mixture. At the same time, DFT calculations were used to optimize the molecular structures, simulate Raman spectra, assign vibrational modes, and evaluate molecular electrostatic potential, frontier orbitals, electronic descriptors, and localized orbital locator maps. The solid-state Raman spectra provided the most resolved molecular fingerprints, with hydroxycinnamic acids exhibiting intense bands corresponding to aromatic and conjugated ν(C=C) modes. In contrast, gallic acid displayed a distinct hydroxybenzoic vibrational pattern dominated by phenolic C–O/O–H and carboxylic contributions. DFT-assisted assignments confirmed that the main spectral differences arise from coupled vibrations involving ν(C=C), ν(C=O), ν(C–O), δ(O–H), aromatic ring deformations, and methoxy-related modes. Molecular electrostatic potential (MEP) and localized orbital locator (LOL) analyses showed that oxygen-centered regions are the most electrostatically and electronically localized sites, thereby explaining the sensitivity of C–O, O–H, and C=O bands to solvent-mediated interactions. HOMO–LUMO analysis revealed extended frontier-orbital delocalization in hydroxycinnamic acids, in contrast to the more localized hydroxybenzoic electronic structure of gallic acid. Principal component analysis confirmed that solid-state Raman spectra provide stronger chemometric discrimination than solution spectra, with PC1 and PC2 explaining 79.0% of the total variance in the solid-state dataset. Overall, the results show that specific functional groups define the principal vibrational domains of the studied phenolic acids. In contrast, the exact band positions, relative intensities, and coupling patterns are additionally modulated by aromatic substitution, π-conjugation, electronic distribution, physical state, and molecular environment. Within the limitations of a single-conformer isolated-molecule model, the combined Raman–DFT–chemometric approach provides a comparative interpretation of the vibrational fingerprints of the four selected compounds. Full article

In existing research on non-contact damage by high-power microwave (HPM) systems to electronic systems such as seekers, challenges include high risk, high cost, and a scarcity of HPM-specific damage assessment models. To address this, this paper proposes a multi-port HPM damage level assessment model based on interval-valued intuitionistic fuzzy (IVIF) sets. Firstly, electromagnetic modeling and field-circuit coupling simulation of multi-target structures provide input data from field-circuit simulations. Secondly, a multi-indicator fuzzy matrix reflecting system damage uncertainty is formed using interval fuzzy membership functions. Thirdly, an information entropy-driven dynamic weighting mechanism weights each indicator’s fuzzy distribution characteristics, and hybrid weights are constructed by dynamic and fixed weights to optimize parameter range rationality. Finally, using hybrid weights and the exponential damage mapping function, we achieve probabilistic fusion of multiple parameters and determine damage levels from the probability results. Assessment shows that under the same incident field strength of 25 kV/m, electromagnetic simulation software-based simulation assigns a composite damage probability of 0.85 to L-band Port 5 and 0.096 to X-band Port 6, highlighting the contrast between the dominant L-band hotspot (Port 5) and the low X-band response at Port 6 under identical irradiation. Full article

Fibrinogen adsorption governs biological responses to implantable medical devices; however, surface properties influence the overall functionality of the biomaterial, and guided fibrinogen adsorption remains limited. In the present work, CaCO₃ was electrochemically deposited on commercial Ti at −1.6 V for 1 h, 2 h, and 3 h. Furthermore, the effects on fibrinogen adsorption were detailed by using dye-assisted scanning electron microscopy (d-SEM), X-ray photoelectron spectroscopy (XPS), and Fourier Transform Infrared Spectroscopy (ATR-FTIR). Longer deposition times produced thicker calcite layers with maximum surface coverage of 99.80 ± 0.40%, accompanied by progressively greater calcium-ion release, ranging from 3.5 mg·L⁻¹·cm⁻² (1 h) to 12.2 mg·L⁻¹·cm⁻² (3 h) over 240 min. The results show that electrochemically deposited calcite crystals for 3 h lead to the formation of sponge-like fibrinogen aggregates via calcium ion-mediated conformational activation, particularly by chelating with the histidine and carboxylate residues of the Bβ chain segment Gly-His-Arg-Pro (β15–β18). This structural reorganization was supported by XPS N 1s binding energy at 398.80 eV and a red shift in Amide I and Amide II bands in FTIR spectra. Overall, this study reveals that careful modification of surface chemistry can guide fibrinogen adsorption, which can be beneficial for advanced biomaterials to orchestrate tissue integration at the protein and cellular levels. Full article

The development of efficient visible-light-driven semiconductor photocatalysts is essential for scalable and sustainable green hydrogen production. Among ternary metal oxides, MV₂O₆ (M = Zn, Ni, Cu, Mn, Co, etc.) metavanadates have attracted considerable interest because of their narrow band gaps (~1.8–2.5 eV), strong visible-light absorption, and unique edge-sharing VO₆ octahedral framework that promotes charge separation. This review summarizes recent advances in the design, synthesis, and electronic engineering of MV₂O₆-based photocatalysts for solar water splitting. Since direct particulate overall water splitting has only been demonstrated for MnV₂O₆, whereas ZnV₂O₆, NiV₂O₆, and CuV₂O₆ have mainly been investigated as photoelectrodes, both particulate photocatalytic and photoelectrochemical (PEC) systems are critically examined. The review clearly distinguishes these two configurations, highlighting how PEC studies provide valuable insights into charge transport, interfacial processes, and reaction kinetics while recognizing the additional challenges associated with suspension-based photocatalysis. Fundamental crystal structures, electronic band alignments, and charge-transfer characteristics of MV₂O₆ compounds are discussed, followed by recent advances in synthesis strategies, including hydrothermal, sol–gel, and deep eutectic solvent (DES)-assisted methods, together with morphology and defect engineering. Particular attention is given to oxygen-vacancy formation and its influence on visible-light absorption and charge separation. Modification strategies, including elemental doping, cocatalyst loading, and the construction of Z-scheme and step-scheme (S-scheme) heterojunctions, are critically evaluated for improving photocatalytic efficiency. Finally, the review discusses the key challenges that limit practical applications, including unfavorable band-edge positions, rapid carrier recombination, sluggish surface reaction kinetics, photostability, and the need to establish composition–structure–activity relationships. Future perspectives emphasize rational materials design through advanced characterization, theoretical calculations, and scalable synthesis approaches to accelerate the development of efficient MV₂O₆ photocatalysts for solar-driven hydrogen production. Full article