Search Results (1,165)

ZnO–ZnCr₂O₄ heterojunction nanocomposites were synthesized via co-precipitation with nominal spinel loadings of 10, 20, and 30 wt.% (denoted ZnCr-10, ZnCr-20, ZnCr-30) to evaluate structure–property–performance relationships in photocatalytic dye degradation. Rietveld refinement of XRD data revealed actual crystalline phase fractions of 12.1%, 32.4%, and 39.9% ZnCr₂O₄, respectively, with systematic morphological evolution from dispersed nanoparticles (ZnCr-10) to densely agglomerated structures (ZnCr-30) observed by SEM. Optical analysis demonstrated that ZnCr-10 (apparent band gap 3.09 eV) retains ZnO-dominated absorption with moderate interfacial electronic coupling, while ZnCr-20 shows enhanced visible response (2.89 eV) through interface-mediated transitions. ZnCr-30 exhibits strong sub-bandgap absorption (1.63 eV) originating from defect states rather than intrinsic band narrowing. Photoluminescence studies under UV excitation revealed optimal radiative recombination suppression in ZnCr-10, consistent with efficient interfacial charge separation, whereas excessive loading (ZnCr-30) introduced defect-mediated recombination centers. Photocatalytic degradation of Rhodamine B (5 mg/L, 0.5 g/L catalyst, solar irradiation) followed the order: ZnCr-10 (k = 0.0307 min⁻¹) > ZnO (0.0203 min⁻¹) > ZnCr-20 (0.0230 min⁻¹) > ZnCr₂O₄ (0.0166 min⁻¹) > ZnCr-30 (0.0113 min⁻¹). The optimal ZnCr-10 performance is attributed to balanced interfacial contact between phases enabling charge separation without excessive agglomeration or defect accumulation. Operational parameters (pH 7, 50 mg/100 mL, 100 µL H₂O₂) were optimized, achieving 98% degradation in 60 min. This study demonstrates that photocatalytic enhancement in ZnO–spinel heterojunctions is governed by interfacial architecture and defect management rather than optical absorption alone, providing design principles for efficient solar-driven environmental remediation. Full article

Designing stable and multifunctional perovskite materials with tunable electronic and optical properties is crucial for advancing next-generation optoelectronic and high-temperature applications. In this study, the structural, electronic, optical, mechanical, and thermal properties of XYO₃ (X = Nb, Ta; Y = Ag, Au) cubic perovskites were systematically investigated using density functional theory (DFT). Each compound crystallized into a cubic perovskite structure and was found to be both thermodynamically and dynamically stable. Hybrid functional (HSE06) calculations indicate semiconducting behavior with band gaps of 1.885 eV (NbAgO₃), 1.298 eV (NbAuO₃), 3.074 eV (TaAgO₃), and 1.801 eV (TaAuO₃). The density-of-state analysis reveals strong hybridization between the O-2p and Nb/Ta-d orbitals, which hints at mixed ionic/covalent bonding. Optical properties exhibit large absorption coefficients (about 10⁶ cm⁻¹) in the ultraviolet range and at lower reflectivity, especially of NbAgO₃ and TaAgO₃, indicating efficient light absorption. NbAgO₃ and NbAuO₃ possess moderate direct band gaps, making them suitable for optoelectronic and photovoltaic applications, whereas the wide bandgap of TaAgO₃ is beneficial in ultraviolet optoelectronic devices. Mechanical analysis confirms the ductile nature of all compounds, with TaAuO₃ exhibiting the highest ductility. Thermal analysis indicates that NbAgO₃ and TaAgO₃ exhibit higher lattice rigidity and thermal conductivity, but NbAuO₃ and TaAuO₃ are more anharmonic and have higher thermal expansion. Overall, these results demonstrate the multifunctional potential of XYO₃ perovskites for applications in optoelectronics, photovoltaics, ultraviolet devices, flexible electronics, and high-temperature environments. Full article

Mg-doped ZnO (Zn_1−xMg_xO, x = 0.00–0.05) thin films were successfully grown on glass substrates with a c-axis orientation at 600 °C using the sol–gel dip-coating technique. The structural features, defect-related photoluminescence, and optical constants of the films were systematically investigated as a function of Mg concentration. X-ray diffraction (XRD) patterns confirmed a single-phase hexagonal wurtzite structure with a preferential (₀₀₂) orientation for all compositions, indicating the successful substitution of Mg²⁺ ions into the ZnO lattice. The crystallite size (D₀₀₂) was found to vary between 28.49 and 41.18 nm, while microstrain and stress exhibited non-monotonic behavior depending on Mg content. This behavior reveals a transition from compressive to tensile stress due to lattice distortion and defect formation. Photoluminescence (PL) spectra showed a dominant near-band-edge (NBE) ultraviolet emission, along with broad visible emissions extending from violet to red. Optical constants were accurately extracted using a double-facet-coated substrate (DFCS) model, combined with nonlinear curve fitting using the Nelder–Mead optimization algorithm. The films showed a strong absorption edge at about 370 nm and exceptional optical transparency (≈60–80%) in the visible spectrum. The systematic blue shift in the extinction coefficient with increasing Mg content confirms bandgap engineering in Zn_1−xMg_xO thin films. The refractive index dispersion was successfully modeled using the Cauchy relation, demonstrating composition-dependent tunable optical properties. Depending on the Mg content, the optical bandgap values ranged from approximately 3.265 to 3.315 eV. The band-edge states and optical constants are strongly affected by the combined effects of defect development, Mg-induced lattice distortion, and changes in optical dispersion. These results indicate that sol–gel-derived Mg-doped ZnO thin films with composition-dependent stress states, defect states, and tunable optical properties are promising candidates for UV photodetectors, optical coatings, and transparent optoelectronic devices. Full article

In the present paper, In₂O₃ NPs were synthesized by a wet-chemical method, in the absence and presence of the surfactant, and deposited as thin films on silicon substrates. After deposition, the films were subjected to rapid thermal annealing (RTA) at 550 °C, 750 °C, and 900 °C, for 300 s, under an inert atmosphere. The correlation between the morphological, structural, and optical characteristics, the wetting capacity of In₂O₃ films synthesized under different synthesis conditions, and the influence of the RTA treatment are presented. The vibrations of In-O bonds for In₂O₃ samples were confirmed using FTIR spectroscopy. Structural analysis shows that In₂O₃ NPs have a cubic crystalline structure, but with the increase in temperature at 900 °C, diffraction peaks characteristic of the tetragonal phase of indium appear, correlated with a decrease in lattice parameters, as a result of the crystallinity. The morphology of the In₂O₃ samples was studied by SEM, revealing predominantly spherical and uniformly distributed particles with nanometric sizes. The absorption spectra of the In₂O₃ NPs showed peaks in the ultraviolet region, and the high energy bandgap value of the In₂O₃ films varied between 3.28 and 4.33 eV, depending on the samples and RTA treatment. The contact angle measurements of In₂O₃ films determined the wetting capacity of the surface, reflecting changes in surface morphology and structure induced by the RTA process. The results suggest that In₂O₃ thin films with spherical nanoparticles, good wettability, and percolation can be used for the development of sensors with increased selectivity and sensitivity. Full article

Zinc oxide (ZnO) is currently one of the most significant wide-bandgap semiconductor materials, attracting extensive research across diverse fields including materials science, chemistry, physics, medicine, electronics, and power engineering. Its exceptional properties, such as high optical transparency, high electron mobility, chemical stability, and compatibility with low-cost fabrication techniques, have established ZnO as a versatile material with immense application potential. A critical application for ZnO is its role as a transparent conducting oxide (TCO) in modern optoelectronic and photovoltaic devices, as well as in sensors, transparent electronics, and spintronics. To meet the requirements of these advanced applications, precise control over the structural, optical, and electrical properties of ZnO thin films is essential. This is effectively achieved through the selection of specific synthesis methods and intentional modification techniques, such as doping. This review provides a comprehensive overview of the synthesis and modification of ZnO thin films, with a particular focus on how various dopants influence their fundamental characteristics. The work discusses a range of deposition techniques, including physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), sol–gel methods, spray pyrolysis, and other solution-based approaches. The novelty of this review lies in its comparative analysis of different doping strategies combined with various thin-film deposition techniques, highlighting how specific synthesis routes influence dopant incorporation and ultimately determine functional properties. Furthermore, recent advances in tailoring ZnO thin films are summarized, alongside the identification of key challenges and future research directions. Ultimately, this work aims to provide researchers with a systematic perspective on the synthesis–structure–property relationships in doped ZnO thin films to support the development of optimized materials for next-generation electronic and optoelectronic devices. This review, thus, serves as a comprehensive reference for researchers and engineers seeking to optimize the functionality of ZnO-based thin films for emerging technological applications. Full article

This paper presents a flipped-voltage-follower low-dropout regulator (FVF-LDO) for power supply rejection enhancement and low-power operation in CMOS transimpedance amplifiers for optical receiver applications. The proposed FVF-LDO ensures high stability and reliable regulation over a wide range of load conditions by employing a flipped-voltage follower for fast local feedback and improved power supply rejection, while a super-source follower enhances the transient response through increased current-driving capability. A bandgap reference with a 3-bit trimming DAC is adopted to compensate process variations and support stable LDO operations, achieving a temperature coefficient of 19.6 ppm/°C over a wide range of −25 °C to 125 °C. The FVF-LDO exhibits a 101 mV undershoot under a 100 µA-to-10 mA load step with a 100 ns edge time. When applied to an optoelectronic inverter-based active-feedback transimpedance amplifier (TIA), the regulated supply improves the power supply rejection ratio (PSRR) from −6 dB to −38.3 dB. The proposed optoelectronic TIA realized in a 180 nm CMOS process achieves 67 dBΩ transimpedance gain, 869 MHz bandwidth, 66 dB dynamic range, 6.68 pA/√Hz input-referred noise current spectral density, and 4.68 mW power consumption from a single 1.8 V supply. The proposed TIA chip occupies a core area of 940 × 162 µm². Full article

Zinc oxide (ZnO) nanomaterials have attracted widespread attention from researchers due to their morphology-dependent properties, eco-friendly characteristics, and potential as a sustainable photocatalyst with a broad range of applications. Therefore, in this study, three different ZnO nanostructures—nanosheets (NSs), nanoflowers (NFs), and nanorods (NBs)—were synthesized via a controlled precipitation method. Among these, NFs exhibited the highest photocatalytic efficiency. The obtained samples exhibited broad optical absorption edges extending into the visible region (corresponding to apparent energies of 1.81–2.09 eV), which is attributed to the sub-bandgap states induced by oxygen vacancies rather than intrinsic bandgap narrowing—far lower than the bandgap of bulk ZnO (3.37 eV). Their photocatalytic performance was evaluated by the degradation of Methyl Blue (MB), Methyl Orange (MO), and Rhodamine B (RhB) under UV or sunlight. Notably, the NFs achieved rapid degradation of MB and RhB within 90 min under UV irradiation without the addition of any H₂O₂, demonstrating their effectiveness and cost-effectiveness for practical applications. Although H₂O₂ inhibited the degradation of MB and RhB, it promoted the decomposition of MO. Furthermore, the ZnO NFs exhibited excellent recyclability in five consecutive degradation cycles. The self-synthesized ZnO nanomaterials in this study, with their broad-spectrum absorption, high stability, and eco-friendly properties, demonstrate their potential as an efficient and low-cost photocatalyst for large-scale wastewater treatment. Full article

In this study, a cellulose nanocrystal (CNC)-supported Ag–ZnO nanocomposite was synthesized via a hydrothermal route as a polymeric photocatalyst for efficient UV-A light-driven dye degradation. The renewable CNC framework provides abundant hydroxyl functional groups for nanoparticle anchoring, enhancing dispersion and interfacial charge transfer. Structural (XRD, FTIR, TEM, PL, and XPS) and thermal (TGA and DTG) analyses confirm successful incorporation of Ag nanoparticles and retention of CNC crystallinity. The composite exhibits a reduced optical bandgap (3.02 eV) and demonstrates superior photocatalytic activity, achieving 96% methylene blue (MB) degradation within 120 min. Enhanced performance is attributed to the synergistic effect of Ag-induced plasmonic excitation and CNC-facilitated charge migration, effectively suppressing ZnO photocorrosion. Moreover, the optimization of the parameters was conducted and found to be pH 7, a catalyst dose of 0.3 g L⁻¹, and an initial MB concentration of 10 ppm, which shows the best photocatalytic degradation reaction. The CNC/Ag–ZnO catalyst maintains 87% activity after five reuse cycles, showing good stability and reusability. The photostability of the CNC/Ag–ZnO catalyst was evaluated by ICP-MS, which measured Zn²⁺ concentration in the aqueous solution. Additionally, the degraded MB compounds were identified using GC-MS/MS analysis. This work highlights the potential of polymer-based biogenic supports for sustainable photocatalyst design and bridges polymer science with environmental remediation technology. Full article

In this study, the indium (In) composition in amorphous indium gallium zinc oxide (a-IGZO) thin films was systematically varied from 33% to 84% using a sol–gel process. Subsequently, aluminum/IGZO/aluminum (Al/IGZO/Al) metal–semiconductor–metal (MSM) UV photodetectors were fabricated to investigate the influence of composition on the structural, optical, and photoelectric properties. The results indicate that all films maintain an amorphous structure despite the increasing In content, while the ratio of oxygen vacancies, O_vac/(M-O + O_vac), rises from 36% to 52%. Concurrently, the optical bandgap decreases from 2.92 eV to 2.32 eV. Under a bias of 20 V, the dark current increases from 2.11 × 10⁻⁹ A to 1.90 × 10⁻⁵ A as the In content rises. When illuminated by a 360 nm LED with a power density of 8.6 mW/cm², the device with 60% In exhibits a photocurrent-to-dark-current ratio of approximately 10⁴, a responsivity of 19.45 A/W, and a specific detectivity of 8.19 × 10¹² Jones. The response time and recovery time of this device are 39.8 s and 577.4 s, respectively. These findings reveal a competitive relationship between enhanced optical absorption and defect generation induced by In composition, providing valuable guidance for the performance optimization of a-IGZO UV photodetectors through compositional engineering. Full article

The study of wide-bandgap nanomaterials has gained considerable attention in recent years, especially in the case of semiconductor oxides that exhibit full or partial optical transparency in fundamental research and technological applications. These include optoelectronic devices, gas sensors and photovoltaic cells, among others. The activation or adjustment of optical and structural properties, especially the bandgap and the parameters of unit cell lattice, can be achieved by varying the dopant concentration during the synthesis of semiconductor thin films in these applications. In this context, copper oxide has emerged as a valuable material, owing to its thoroughly analyzed structural behavior and its broad potential across multiple technological fields. The present work focuses on the synthesis of zinc-doped copper oxide (Zn_xCu_1−xO) thin films on silicon and quartz substrates through ultrasonic spray pyrolysis. The effects of varying the zinc doping concentration (0.0, 5.0, 10.0 and 20.0 at. %) on the morphological, structural, and optical characteristics of the Zn_xCu_1−xO films were analyzed. Scanning electron microscopy (SEM) analysis indicated a gradual increase in nanoparticle size, rising from 221 nm for CuO to approximately 322 nm for the Zn_0.2Cu_0.8O samples as the zinc content increased. Structural characterization via X-ray diffraction (XRD) confirmed a monoclinic crystal arrangement belonging to the $C_{2h}^6$ (c2/c) space group. As the percentage of zinc increased, the XRD peaks shifted to lower angles, consequently increasing the volume and crystal lattice parameters of the Zn_xCu_1−xO structure; this finding was additionally supported by a redshift observed in the Raman analysis. The transmittance spectra of the films showed low transmittance between 40 and 44%. The optical bandgap of the Zn_xCu_1−xO thin films was estimated from the transmittance data by applying the Tauc plot method. A decrease in the band gap was observed at higher doping concentrations. It can be confirmed that no secondary phases are observed at a doping level of 20.0 at. % of zinc, indicating good solubility of zinc in CuO. The analysis and discussion of these findings are included throughout this work to elucidate the controversies noted in the literature. Full article

This study reports the structural, optical, and photocatalytic properties of Nd-doped Al₂O₃ nanoparticles synthesized via a high-temperature solid-state reaction method. The impact of varying Nd concentrations (1%, 2%, and 3%) on the host lattice was investigated through X-ray diffraction (XRD), which confirmed the successful integration of Nd³⁺ ions and revealed a concentration-dependent lattice expansion. Diffuse Reflectance Spectroscopy (DRS) demonstrated characteristic 4f-4f transitions of Nd³⁺, while Tauc plot analysis indicated a systematic blue shift in the optical bandgap from 4.5 eV to 4.63 eV with an increasing dopant content. The photocatalytic efficiency was evaluated through the degradation of Basic Fuchsin (BF) dye under UV irradiation. The Al₂O₃:3% Nd sample exhibited superior performance, achieving an 83% degradation efficiency within 160 min, following pseudo-first-order Langmuir–Hinshelwood kinetics (k_obs = 0.02428 min⁻¹). Photoluminescence (PL) studies further corroborated the structural integrity and defect dynamics, showing a significant enhancement in NIR emission (880–920 nm) at higher doping levels without reaching the concentration-quenching threshold. These results suggest that Nd-doped Al₂O₃ nanoparticles are highly effective for environmental remediation and optoelectronic applications. Full article

In the pursuit of sustainable and flexible electronics, polymer-based conductive films offer a promising solution due to their biodegradability, mechanical flexibility, and cost-effective fabrication. This study presents the development of a highly conductive and flexible nanocomposite material based on polyaniline-grafted chitosan (PANI-g-Chs) and Vinavil (Vi, a vinyl glue specifically designed for enhancing the sealability of textiles and paper), serving as a matrix for applications in flexible electronics. The PANI-g-Chs nanocomposite was synthesized via in situ oxidative polymerization, where chitosan nanoparticles (Chs) served as a stabilizing template to prevent PANI aggregation, reducing the particle size from 1700 nm (pristine PANI) to 180 nm (PANI-g-Chs). The resulting composite exhibited exceptional electrical conductivity (77.79 S/m at 25 wt% PANI-g-Chs). Hall effect measurements showed that the carrier mobility increased up to 1162.7 cm²/V·s and the carrier density rose to 6.5.1017 cm⁻³, confirming efficient charge transport and network formation. Mechanical analysis revealed a 300% increase in the storage modulus for PANI-g-Chs, and thermal studies confirmed stability up to 300 °C. Optical characterization showed a reduced bandgap (3.6 eV) and extended π-conjugation, which are critical for optoelectronic applications. Application tests demonstrated stable conductivity under mechanical deformation, highlighting the material’s potential for use in flexible electronics, sensors, and sustainable conductive coatings. This work offers a viable alternative to conventional conductive polymers. Full article

Heterogeneous photocatalysis is one of the most versatile and widely studied photochemical approaches for the degradation of recalcitrant pollutants. Owing to its favorable physicochemical properties, titanium dioxide (TiO₂) remains one of the most investigated semiconductor photocatalysts. However, its wide band-gap energy (3.2 eV) restricts its photoactivity to the UV region, which represents only a small fraction of the solar spectrum. A major challenge in this field is therefore the development of TiO₂-based materials capable of operating efficiently under visible light irradiation, enabling the use of solar energy as a sustainable primary source. Several strategies have been explored to extend the optical response of TiO₂, among which elemental doping remains one of the most effective and commonly applied. In this work, we conducted systematic comparative analysis to evaluate the photocatalytic performance of TiO₂ modified through different doping approaches. Sixty-one scientific reports published between 2015 and 2025 were analyzed, comparing three categories of dopants: (i) metal dopants, (ii) non-metal dopants, and (iii) co-doping systems. In the first section, we discuss fundamental concepts of photocatalysis and recent advances in doping strategies and surface modifications aimed at enhancing the photocatalytic performance of TiO₂. In the second section, we present a comparative analysis based on 61 scientific reports focusing on TiO₂ doping and co-doping processes. Finally, this study summarizes the different categories of doped TiO₂ photocatalysts by comparing the photocatalytic performance employing an alternative performance metric. Full article

Solar-driven interfacial evaporation is a sustainable technology for freshwater production; however, the rational design of photothermal materials that simultaneously achieve full-spectrum solar absorption, minimized thermal loss, and efficient energy utilization remains a formidable challenge. Herein, we report a “post-treatment” defect engineering strategy to fabricate highly active, non-stoichiometric BTO (black TiO_2−x) via a hydrothermal-assisted atmospheric deoxygenation process. The precise modulation of oxygen vacancies (O_v) within the TiO₂ lattice effectively narrows its bandgap, facilitating a dramatic enhancement in both light-harvesting capacity and photothermal conversion efficiency. By integrating the BTO into a polyvinyl alcohol (PVA) hydrogel framework, we developed a 3D evaporator (TPVA) that synergistically couples superior optical trapping with attenuated thermal conductivity. Consequently, the O_v-enriched TPVA architecture achieves an impressive solar absorption of 94.3%, enabling a high-performance evaporation rate of 2.492 kg m⁻² h⁻¹ under 1 sun irradiation, which is approximately 5.0 times higher than that of direct seawater evaporation under the same conditions. This work underscores the efficacy of defect engineering in optimizing semiconductor photothermal materials and provides a promising strategy for the advancement of next-generation solar desalination technologies. Full article

Metal-chalcogenide compounds with perovskite-type compositions have drawn increasing attention for their optical properties for solar energy conversion. Herein, a new α-type polymorph of the ternary sulfide SrHfS₃ is described, crystallizing in the NH₄CdCl₃ structure type. The yellow-colored plate-shaped crystals were synthesized at 1173 K using an elemental tin flux in an evacuated sealed tube. Its crystal structure was characterized at room temperature using single crystal X-ray diffraction to form in the orthorhombic Pnma space group, with the refined cell parameters of a = 8.5041(4) Å, b = 3.8004(2) Å, c = 13.8935(6) Å, and V = 449.02(4) ų. The structure comprises five independent crystallographic sites, having one Sr, one Hf, and three S sites. The structure can be described as containing one-dimensional chains of distorted HfS₆ octahedra extending down the b-axis to form ${\displaystyle \genfrac{}{}{0pt}{}{1}{\infty }}[$HfS₃]²⁻ strips of edge-sharing octahedra. The Sr atoms act as charge-balancing space fillers in the structure. High-purity bulk samples of α-SrHfS₃ could be prepared for measurement of its bandgap by optical diffuse-reflectance spectroscopy, showing a direct bandgap of 2.1(1) eV. Results of electronic structure calculations are consistent with this bandgap and type. The conduction and valence band edges stem from the respective empty Hf d-orbitals and the filled S p-orbital states. In summary, crystal growth of the α-type polymorph of SrHfS₃ has been demonstrated using a Sn flux approach, which can facilitate future broader synthetic explorations at lower temperatures. Full article