Copper nanoparticles (CuNPs) possess a promising antibacterial and antifungal activity with low-cost reagent and fabrication. In this study, we report the antifungal activity of pure CuNPs against Fusarium oxysporum ( F . oxysporum ) and Phytophthora capsici ( P . capsici ). CuNPs were prepared by reducing Cu ²⁺ from copper(II) chloride dihydrate via a green chemical reduction agent using ascorbic acid as both reducing agent and antioxidant agent in aqueous media and polyvinylpyrrolidone as a stabilizer. The effect of the solution pH, reduction time, ascorbic-acid-to-Cu ²⁺ molar ratio, role of stabilizing agent polyvinylpyrrolidone to particle size of CuNPs were studied. The antifungal activity of CuNPs at different concentrations and different particle sizes against two plant pathogenic fungi F . oxysporum and P . capsici has been tested by the agar disc diffusion technique. Characterizations were carried out by X-ray diffraction measurements, transmission electron microscopy, and ultraviolet–visible light, which revealed that the CuNPs obtained at different synthesis conditions have different particles size, resulting in different antifungal activities. The synthesized CuNPs demonstrated significant antifungal activity against F . oxysporum and P . capsici . F . oxysporum and P . capsici were entirely inhibited at the concentration of CuNPs of 30 ppm after 3 days of incubation and 7.5 ppm after 1 day of incubation, respectively. Our results suggest that synthesized CuNPs can be used as a novel antifungal agent in agriculture to control the plant pathogenic fungi of F . oxysporum and P . capsici .

Effective La-doped SrTiO₃ (Sr_1−xLa_xTiO₃, x = 0–0.1 mol.% La-doped) nanocubes were successfully synthesized by a hydrothermal method. The influence of different La dopant concentrations on the physicochemical properties of the host structure of SrTiO₃ was fully characterized. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) revealed that the Sr²⁺ in the crystal lattice of SrTiO₃ was substituted by La³⁺. As a result, the absorption region of the Sr_1−xLa_xTiO₃ could be extended to visible light. Scanning electron microscopy (SEM) images confirmed that their morphologies are associated with an increased surface area and an increased La-doping concentration. The decrease in the photoluminescence (PL) intensity of the dopant samples showed more defect levels created by the dopant La⁺³ cations in the SrTiO₃ structure. The photocatalytic activities of Sr_1−xLa_xTiO₃ were evaluated with regard to the degradation of 2-naphthol at typical conditions under artificial solar light. Among the candidates, Sr_0.95La_0.05TiO₃ exhibited the highest photocatalytic performance for the degradation of 2-naphthol, which reached 92% degradation efficiency, corresponding to a 0.0196 min⁻¹ degradation rate constant, within 180 minutes of irradiation. Manipulating the structure of Sr_1−xLa_xTiO₃ nanocubes could produce a more effective and stable degradation efficiency than their parent compound, SrTiO₃. The parameters remarkably influence the Sr_1−xLa_xTiO₃ nanocubes’ structure, and their degradation efficiencies were also studied. Undoubtedly, substantial breakthroughs of Sr_1−xLa_xTiO₃ nanocube photocatalysts toward the treatment of organic contaminants from industrial wastewater are expected shortly.

The symmetric nano morphologies, asymmetric electronic structures, and as well as the heterojunctions of the developed photocatalytic systems perform a vital role in promoting light absorption, separation of electron and hole pairs and charge carrier transport to the surface when exposed to near-infrared (NIR) light. In this present work, we synthesized hematite (α-Fe₂O₃) nanoparticles (NPs) by a facile hydrothermal method and studied their structural, optical, and photocatalytic properties. Powder X-ray diffraction (XRD) confirmed the rhombohedral phase of the α-Fe₂O₃ NPs, and Fourier transform infrared spectroscopy (FT-IR) was used to investigate symmetric and asymmetric stretching vibrations of the functional groups on the surface of the catalysts. The optical bandgap energy was estimated to be 2.25 eV using UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and scanning electron microscopy (SEM) images indicated sphere like morphology. The oxidation and reduction properties of α-Fe₂O₃ NPs were analyzed by cyclic voltammetry (CV). The α-Fe₂O₃ NPs were utilized for the degradation of methylene blue (MB) dye under natural sunlight. The experimental results demonstrate that the degradation efficiency was achieved at 33% in 2 h, and the pseudo-first-order rate constant was calculated to be 0.0033 min⁻¹.

Gas-sensing technology has witnessed significant advancements that have been driven by the emergence of graphene quantum dots (GQDs) and their tailored nanocomposites. This comprehensive review surveys the recent progress made in the construction methods and applications of functionalized GQDs and GQD-based nanocomposites for gas sensing. The gas-sensing mechanisms, based on the Fermi-level control and charge carrier depletion layer theory, are briefly explained through the formation of heterojunctions and the adsorption/desorption principle. Furthermore, this review explores the enhancements achieved through the incorporation of GQDs into nanocomposites with diverse matrices, including polymers, metal oxides, and 2D materials. We also provide an overview of the key progress in various hazardous gas sensing applications using functionalized GQDs and GQD-based nanocomposites, focusing on key detection parameters such as sensitivity, selectivity, stability, response and recovery time, repeatability, and limit of detection (LOD). According to the most recent data, the normally reported values for the LOD of various toxic gases using GQD-based sensors are in the range of 1–10 ppm. Remarkably, some GQD-based sensors exhibit extremely low detection limits, such as N-GQDs/SnO₂ (0.01 ppb for formaldehyde) and GQD@SnO₂ (0.10 ppb for NO₂). This review provides an up-to-date perspective on the evolving landscape of functionalized GQDs and their nanocomposites as pivotal components in the development of advanced gas sensors.