Light attenuation and optical absorption characteristics of graphene-chitosan nanomaterials-based quandary nanocomposites

Thermally evaporated Azure A chloride thin films were deposited on fluorine-doped tin oxide (FTO) substrates with thicknesses ranging from 75 to 175nm, and their structural, optical, and optoelectronic properties were systematically investigated. X-ray diffraction analysis indicates that the deposited films exhibit an amorphous structure, while optical measurements reveal strong absorption in the visible region with absorption coefficients on the order of 104-105cm-1. The optical bandgap shows a clear thickness dependence, with the lower-energy transition increasing from 1.27 to 1.57eV and the higher-energy transition decreasing from 3.5 to 2.8eV as the film thickness increases. Dispersion analysis reveals thickness-dependent refractive index and dielectric response, reflecting enhanced photon-matter interactions in thicker films. The optical conductivity and related parameters further confirm the influence of film thickness on charge carrier excitation under optical illumination. In addition, A simple Au/Azure A chloride/FTO device was fabricated to demonstrate the photoresponse behavior of the films under illumination. These results highlight the suitability of Azure A chloride thin films for optical and photonic applications.

Abstract This study examined the electronic band structure and optical characteristics of alpha-alumina (α-Al2O3) doped by indium (In), boron (B) and arsenic (As) using density functional theory (DFT). All the simulations have been carried out in the frame of the DFT function where the exchange-correlation potential is the generalized gradient approximation (GGA). In this work, the doping concentration of In, B, and As in place of Al atoms in Al2O3 was 8.33%. The electronic band structure, density of states (DOS) and optical properties were systematically calculated at the doped configurations. The electronic band structure analysis revealed that doped α-Al2O3 with In, B and As shows reduced optical band gap which dropped from 6.47 eV for undoped α-Al2O3 to 4.91, 4.25, and 3.25 eV, for the doped atoms, respectively. The corresponding DOS confirmed the emergence of dopant-induced states inside the gap region, shifting the optical absorption edge to lower photon energies. The red-shift in the optical absorption edge indicates enhanced absorption in visible spectral region for doped α-Al2O3 suggesting improved potential for visible-light-driven applications. The increase in refractive index reflects increased charge polarization in the doped α-Al2O3 material, which slows the phase velocity of photon in the material. Moreover, the sharp rise in optical conductivity for As-doped α-Al2O3 beyond the band-edge transitions is consistent with the observed optical absorption response. The calculated absorbance, reflectance, and transmittance spectra demonstrate that doped α-Al2O3 responds in the visible spectrum of the electromagnetic spectrum, while the undoped phase essentially transparent. Overall, the results demonstrate that doping is an effective strategy for tuning the electronic structure and optical properties of α-Al2O3. The calculated characteristics also suggest potential applicability of the investigated materials in photocatalytic systems. However, a detailed investigation of specific photocatalytic mechanisms requires further dedicated investigation.

Investigation of the structural, optical and electrical conductivity properties of Ga-doped ZnO nanoparticles

A graphene-integrated refractory metasurface absorber is proposed for broadband solar thermal energy conversion. Near-unity broadband absorptance across 300-2500nm is achieved through three concurrent mechanisms: free-space impedance matching, ground-plane-mediated transmission suppression, and multimodal electromagnetic energy dissipation distributed across spectrally coupled plasmonic and dielectric resonant channels. Spectral tunability without structural reconfiguration is demonstrated through electrostatic modulation of the graphene Fermi level, which enables reversible control of the optical sheet conductivity. Alternative material configurations incorporating caesium, gallium arsenide, copper, and strontium are evaluated through full-wave COMSOL Multiphysics simulations under periodic boundary conditions, with assessment of spectral bandwidth, resonance behaviour, and thermal robustness at elevated temperatures. A dielectric substrate thickness of approximately 4.1μm satisfies the quarter-wavelength Fabry-Perot cavity resonance condition, suppressing mid-infrared radiative emission and reducing parasitic thermal losses. A random forest regression surrogate model trained on 1,200 finite-element simulation samples, with five geometric and material input parameters and 500 estimators, maps the design space with R2 > 0.90 across most parameter configurations. Accuracy decreases to R2 approximately 0.63 near normal incidence, where overlapping resonances increase spectral complexity. The optimised configuration achieves a peak absorptance of 99.99% and a broadband solar-weighted average of 98.6%.

We present a machine learning-enhanced computational framework for predicting the optical properties of two-dimensional silicon arsenide (SiAs). By combining first-principles density functional theory (DFT) calculations with artificial neural networks (ANNs), decision trees (DTs), and random forest regression (RFR), we achieve accurate modeling of both absorption spectra and optical conductivity. Our results demonstrate that RFR delivers the highest quantitative accuracy ( R 2 = 1 . 000 , MAE = 0 . 0005 ), while ANNs provide the most physically realistic continuous spectra. Although DTs provide useful interpretability, their generalization performance is inferior to that of the other approaches. The machine learning models successfully reproduce all key features observed in the DFT calculations, including the prominent absorption peak at 5–6 eV. Detailed analysis of training dynamics reveals that ANNs maintain stable convergence over 500 epochs, while the ensemble approach of RFR effectively compensates for the overfitting tendencies inherent to individual DTs. This hybrid DFT-ML approach provides new insights into SiAs’ optoelectronic properties while establishing a generalizable workflow for accelerating the discovery of 2D materials with tailored optical responses. • A hybrid DFT-machine learning framework is developed for 2D SiAs optical spectra. • ANN, DT, and RFR models are trained to predict absorption and optical conductivity. • RFR achieves the highest accuracy with R² = 1.000 and MAE = 0.0005. • ANN produces smooth and physically realistic optical spectra across 500 epochs. • The DFT-ML workflow accelerates the discovery of 2D materials with tailored optics.

Integrated experimental and DFT study of dielectric relaxation and optical properties in the chlorobenzene-n-butyl alcohol.

Spectroscopic and DFT-based characterization of V(V)-alizarin red S complexes: Structural, optical, and photonic insights.

Abstract We report a broadband spectroscopic-ellipsometry study of high-quality (Cu, C)Ba2Ca3Cu4Oy thin films (hereafter abbreviated as (Cu, C)-1234), aimed at tracking the temperature dependence of the electronic structure from 0.5 to 4.2 eV. From the extracted complex dielectric function, we obtain the real optical conductivity σ1 (ω) and quantify spectral-weight redistribution in four energy windows that separate the low-energy intraband response in contrast to the mid- and high-energy Cu-O interband/charge-transfer excitations. Upon cooling, the spectra display a redistribution of optical spectral weight that spans more than 1 eV, far larger than the superconducting gap, indicating correlation effects beyond a weak-coupling picture. The low-energy intraband spectral weight is suppressed near a pairing-onset temperature Tconset and partially recovers below the zero-resistance temperature Tc0, while weight in Zhang-Rice-singlet and LHB-UHB charge-transfer channels increases, with the largest high-energy enhancement appearing at or just below Tc0. These observations may indicate a two-stage evolution of the electronic structure, in which precursor pairing or phase fluctuations first reduce the single-particle coherence, followed by further spectral reorganization at lower temperatures. However, considering the relatively broad resistive transition of the film, the observed spectral-weight changes may also be influenced by percolative superconductivity or by a distribution of local transition temperature in the film. This eV-scale spectral-weight redistribution may reflect related electronic or lattice effects discussed in previous studies of cuprates. Our results demonstrate that low- and high-energy electronic degrees of freedom are cooperatively involved in the superconducting transition of multilayer cuprates, thereby motivating layer-resolved spectroscopies and theoretical efforts to clarify the microscopic coupling mechanisms.

Using Trotter-Suzuki and Tight-Binding Time Propagation Method to calculate density of states and optical conductivity of non-metal doped graphitic heptazine carbon nitride

Biosensors have emerged as a rapidly evolving area of research, offering transformative potential across biomedical diagnostics, environmental monitoring, and pharmaceutical applications. Among the diverse range of biosensing technologies, graphene-based surface plasmonic resonance (SPR) biosensors have attracted particular interest due to their exceptional sensitivity, scalability for mass production, and cost-effective fabrication processes. This study explores the operational principles and current design methodologies of graphene-based SPR biosensors, with a special emphasis on the role of electrolyte gating and its impact on sensor performance. Furthermore, the influence of graphene’s quantum capacitance is investigated as a critical parameter for improving the accuracy and reliability of performance predictions in the proposed sensor configuration. Computational analysis of sensitivity and key performance metrics was conducted. Notably, key performance metrics of the sensor improved upon incorporating quantum capacitance effects into the simulation framework. At a β2-microglobulin concentration of 0.00118 g/L, the sensitivity increased to 174 GHz·g/L, the figure of merit reached 0.55 L/g, the quality factor was 0.01, the signal-to-noise ratio (SNR) rose to 0.008, and the detection accuracy (DA) reached 0.08 L/THz, demonstrating the significant impact of quantum capacitance on the sensor’s performance. These findings highlight the potential of quantum-electrostatic considerations to enhance the precision and efficacy of graphene-based SPR biosensors, paving the way for the development of next-generation biosensing platforms with improved analytical capabilities. Unlike conventional graphene SPR biosensors, which primarily detect refractive index changes near the graphene surface, our model explicitly considers the electrostatic effect of biomolecules on graphene’s Fermi energy. By modelling β2-microglobulin as a charged species, we compute the resulting electric double layer and incorporate quantum capacitance in series. This amplifies the charge-induced modulation of graphene’s optical conductivity, and, combined with a graphene perfect absorber design, leads to enhanced plasmonic resonance shifts. Consequently, our approach achieves higher sensitivity and more precise detection of biomolecular interactions compared to traditional simulations.

The effect of symmetry breaking on the optical properties of V₂CO₂ MXene and its Janus derivatives is systematically investigated using first-principles calculations. Janus structures are constructed by replacing one surface oxygen layer with halogen atoms (F, Cl, and Br), thereby inducing structural asymmetry. The thermodynamic stability of all configurations is confirmed through formation energy calculations. Optical properties are evaluated using density functional theory augmented with van der Waals corrections. Symmetry breaking is found to significantly modify the optical response of the material. The refractive index, dielectric function, reflectivity, optical conductivity and absorption coefficient are analyzed in detail. A gradual reduction in optical strength is observed in the order O > Br > Cl ≈ F. Notably, Br-functionalized Janus V₂CO MXene exhibits pronounced low-energy optical peaks, indicating enhanced polarizability and strong interband transitions. Furthermore, it shows superior optical performance in the near-infrared region compared to other halogen terminations. These results suggest that V₂COBr Janus MXene is a promising candidate for near-infrared photodetector applications.

Eco-friendly halide perovskites have garnered interest as viable options for next-generation optoelectronic and solar-energy technologies due to their adjustable bandgaps, robust light absorption, and excellent charge-transport properties. This study presents the inaugural comprehensive theoretical examination of the eco-friendly double perovskite 'Cs2SnGeCl6' through two methodologies: density functional theory (DFT) for elucidating the physical properties of this compound and SCAPS-1D simulations to assess its viability as an absorber layer in perovskite solar cells (PSCs). Using the advanced calculation functions in DFT, we confirm that Cs2SnGeCl6 is stable in terms of structure, mechanical stability, and thermodynamics, making it a good choice for solar energy harvesting. This stability is enhanced by positive phonon dispersion, a direct bandgap of around 1.837 eV derived by the application of TB-mBJ, a robust computational method characterized by significant absorption over the visible spectrum, and advantageous optical conductivity. Building on these electronic and optical insights, SCAPS-1D simulations were performed using DFT-derived parameters to model sixteen n-i-p device architectures incorporating newly engineered electron and hole transport layers. The best initial configuration, FTO/SnS2/Cs2SnGeCl6/CuGaO2 yielded a power conversion efficiency (PCE) of 20.31%, and after optimization, the PCE increased to 23.29%.

The present study examines the effect of pressure on a new cubic Na 2 LiYBr 6 on structural, electronic, elastic, and optical properties from 0 to 90 GPa. The purpose of this study is to employ pressure to reduce the electrical band gap of Na 2 LiYBr 6 in order to improve its optical characteristics and assess its potential for usage in optical electronic devices. Our results show that increasing pressure leads to a consistent reduction in both the lattice parameter and the overall cell volume. Based on the band-structure analysis, Na 2 LiYBr 6 exhibits a direct band gap at ambient pressure. The electronic band gap gradually narrows from 3.08 eV to 1.35 eV as the pressure increases to 90 GPa. The calculated elastic parameters confirm that the material remains mechanically stable up to 90 GPa, while also displaying noticeable anisotropy and a predominantly ductile nature. Importantly, the mechanical strength of the compound improves significantly under applied pressure. Furthermore, the dielectric function, refractive index, reflectivity, absorption, and other optical properties were evaluated within the 0-14 eV energy range under different pressure conditions. At 0 GPa, the static dielectric function ε 1 (0) for Na 2 LiYBr 6 is at its lowest (3.52). For 45 GPa, Na 2 LiYBr 6 is found to have the highest optical conductivity σ(ω) values at 9 eV (10.1 × 10 3 (Ω·cm) -1 ), indicating that they are appropriate for the UV region. These optica responses indicate that Na 2 LiYBr 6 perovskite can be employed in pressure-sensitive optoelectronic devices, including photodetectors, LEDs, and solar cells, due to its band gap tunability and improved mechanical stability

2D halide perovskites are promising materials for optoelectronics due to their strong excitonic effects and soft, dynamically active lattices. Synthesis conditions, particularly thermal annealing, play a critical role in tuning their structural and excitonic properties by influencing lattice vibrations and defect states. The impact of structural reorganization in 2D Ruddlesden-Popper (RP) n-butyl ammonium lead iodide (BA2PbI4) has been systematically characterized using various state-of-the-art experimental techniques, such as temperature-dependent X-ray diffraction (XRD), temperature-dependent photoluminescence (TDPL), temperature-dependent resonance Raman spectroscopy, terahertz time-domain spectroscopy (THz-TDS), transient absorption spectroscopy (TAS), and further supported by first-principles DFT calculations, reveals a direct link between thermal processing and structural dynamics. Raman spectra show broadened low-frequency modes in the annealed sample, indicative of enhanced lattice anharmonicity. THz-TDS reveals stronger phonon absorption near 2 THz, aligning with Raman-active modes and confirming increased lattice anharmonicity. The 2 THz phonon mode in the annealed film exhibits a nearly threefold increase in oscillator strength (OS), calculated by integrating the real part of the optical conductivity between 0.2 and 2.5 THz, increasing from 39.01 S m- 1 THz in the as-grown film to 146.19 S m- 1 THz after annealing, indicating enhanced exciton-phonon coupling; this is further complemented by TDPL measurements, which show more pronounced self-trapped exciton (STE) emission in the annealed film below ∼270 K, collectively corroborating strong exciton-phonon coupling. Transient absorption spectroscopy shows longer carrier lifetimes (∼1.7ns) in the annealed film vs. the as-grown (∼1.1ns), consistent with increased exciton localization. Thermal annealing boosts lattice dynamics and exciton-phonon coupling, offering a strategy for future low-dimension material design.

Due to its strong near-infrared (NIR) absorption and high thermal conductivity, graphene is considered an excellent nanophotothermal filler that can effectively improve the photothermal conversion performance of composites. In particular, graphene-polymer nanocomposites, new types of photothermal conversion materials, have broad application prospects in photothermal therapy, photothermal driving, and micro-/nanomachinery. Recent research results have shown that when the filling concentration of graphene nanosheets (GNSs) in the matrix reaches the percolation threshold, interface effects such as interface tunneling and Maxwell-Wagner-Sillars (MWS) polarization, the key factors affecting the photothermal conversion performance of such composites, will occur. Furthermore, graphene exhibits unique optical conductivity due to its strong interaction with light. To reveal how interface effects influence the photothermal conversion performance of these nanocomposites, the optical conductivity of graphene at near-infrared frequencies was introduced to modify the effective medium theory. By combining this with a photothermal conversion model, the photothermal conversion behaviors of GNS-polymer composites are discussed, taking into account the interface effects and optical conductivity characteristics of GNSs.

Highly transparent and conductive electrodes operating in the infrared (IR) are critically needed for a broad range of technologies, including light-emitting diodes, lasers and photodetectors, which are key building blocks of infrared cameras, LiDARs, and thermal systems such as IR heaters. While transparent conductive electrodes (TCEs) have seen substantial progress in the visible spectrum, their performance in the IR remains limited due to increased absorption and reflection caused by the plasma resonance of free carriers in conductive materials. Here, we demonstrate a large-area TCE based on a metal-integrated monolithic high-contrast grating (metalMHCG) fabricated on a GaAs substrate. This structure acts as an effective antireflection coating, achieving near-unity transmission of unpolarized mid- to far-infrared (M-FIR) light. The metalMHCG exhibits 94% transmission at a wavelength of 7 μm, corresponding to 135% relative to transmission through a flat GaAs-air interface, while maintaining an exceptionally low sheet resistance of 2.8 Ωsq-1. By simultaneously delivering excellent optical transparency and electrical conductivity, the metalMHCG establishes a new performance benchmark among M-FIR TCEs and provides a versatile platform for next-generation high-power optoelectronic devices.

Transparent conducting electrodes (TCEs) are essential for high-performance organic light-emitting diodes (OLEDs), particularly in transparent and flexible device architectures. Conventional TCEs such as indium tin oxide (ITO) suffer from mechanical brittleness and limited material availability, and often require sputtering processes that can damage underlying organic layers. In response, various alternatives including conductive polymers and nanomaterials or structure-based approaches of metallic films have been explored. However, many of these approaches still face limitations such as low conductivity, poor interfacial contact, or solvent compatibility issues that may degrade device performance. To overcome these challenges, we present a novel direct patterning strategy for top transparent metal mesh electrodes using the metal desorption behavior of solution-processed poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and a transfer printing method. By thermally evaporating silver onto patterned PVDF-HFP layers, we successfully fabricated metal mesh electrodes with high optical transmittance, low sheet resistance, and a maximum figure of merit exceeding 104 using the ratio of electrical conductivity to optical conductivity, which is among the highest reported for sub-micrometer transparent electrodes. This method does not require any lamination, or immersion in solvents or electrolytes, enabling direct integration onto sensitive organic layers. With improved transparency, the metal mesh electrodes were able to be applied as the top cathodes of OLEDs exhibiting comparable electroluminescence characteristics to those with conventional electrodes.

Study of polymer coatings implanted with high-energy ion beams

This study explores the structural, optical, and magnetic transformations in cobalt-doped cadmium selenide (CdSe:Co) thin films, synthesized via chemical bath deposition (0–11 mol%) and modeled using density functional theory (DFT). X-ray diffraction (XRD) confirms a cubic zinc-blende structure, where Co doping induces a transition to a highly crystalline state at 11 mol%, despite the emergence of a secondary CoSe 2 phase. Scanning electron microscopy (SEM) reveals a significant morphological shift from isolated macro-spheres to dense cauliflower-like polycrystalline clusters. UV-Vis spectroscopy demonstrates a systematic bandgap narrowing (2.06–1.98 eV) and a pronounced redshift in the absorption edge, while photoluminescence (PL) analysis exhibits concentration quenching with a unique intensity recovery at 11 mol%, attributed to dopant-induced localized state sequestration. Complementary DFT calculations using the SIESTA package provide a microscopic rationale for these observations, revealing a significant bond contraction (Co–Se: 2.42 Å) and strong sp − d exchange interactions. Spin-polarized density of states (DOS) and band structure analyses confirm the material's evolution into a diluted magnetic semiconductor (DMS) with a calculated spin magnetic moment of 3.00 μB per Co atom. Furthermore, theoretical optical conductivity shows enhanced infrared activity driven by intra-band d - d transitions. The convergence of experimental and theoretical results identifies Co doped CdSe as a versatile candidate for both high-efficiency solar energy conversion and advanced spintronic technologies.