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An efficient and environmentally friendly combustion technique was employed to produce ZnO nanopowders with different Eu concentrations (from 0.001 g to 5 g). The structural morphology of the Eu2O3-ZnO nanocomposites was examined using XRD, SEM, and infrared spectroscopy (FT-IR). In addition, UV-Vis diffuse reflectance spectroscopy was also used to investigate the effects of europium (Eu) dopant on the optical behaviors and energy bandgaps of nano-complex oxides. The photocatalytic degradation efficiency of phenol and methylene blue was investigated using all the prepared Eu2O3-ZnO nanostructured samples. Photocatalytic effectiveness increased when europium (Eu) doping ratios increased. After adding moderate Eu, more hydroxyl radicals were generated over ZnO. The best photocatalyst for phenol degradation was 1 percent Eu2O3-ZnO, while it was 0.5 percent Eu2O3-ZnO for methylene blue solutions. The obtained Eu2O3-doped ZnO nanostructured materials are considered innovative, promising candidates for a wide range of nano-applications, including biomedical and photocatalytic degradation of organic dyes and phenol.

A lanthanum oxide (La2O3)-ZnO nanostructured material was synthesized in the proposed study with different La2O3 concentrations, 0.001 g to 5 g (named So to S7), using the combustion method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transformation infrared spectroscopy (FT-IR) were utilized for investigating the structure, morphology, and spectral studies of the La2O3- ZnO nanomaterials, respectively. The results obtained from previous techniques support ZnO’s growth from crystalline to nanoparticles’ fine structure by changing the concentrations of lanthanum oxide (La2O3) dopants in the host matrix. The percentage of ZnO doped with La- influences the ZnO photocatalytic activity. SEM analysis confirmed the grain size ranged between 81 and 138 nm. Furthermore, UV-Vis diffuse reflectance spectroscopy was performed to verify the effects of La2O3 dopants on the linear optical properties of the nano-composite oxides. There was a variation in the energy bandgaps of La2O3-ZnO nanocomposites, increasing the weight concentrations of lanthanum dopants. The AC electrical conductivity, dielectric properties, and current–voltage properties support the enactment of the electrical characteristics of the ZnO nanoparticles by adding La2O3. All the samples under investigation were used for photodegradation with Rhodamine B (RhB) and Methylene Blue (MB). In less than 30 min of visible light irradiation, S4 (0.5 g) La2O3-ZnO reached 99% of RhB and MB degradation activity. This study showed the best photocatalytic effect for RhB and MB degradation of 0.13 and 0.11 min−1 by 0.5 g La2O3-ZnO. Recycling was performed five times for the nanocatalysts that displayed up to 98 percent catalytic efficiency for RhB and MB degradation in 30 min. The prepared La2O3-ZnO nanostructured composites are considered novel candidates for various applications in biomedical and photocatalytic studies.

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.

To eliminate imidacloprid insecticide from wastewater, nanocalcite was grafted onto the surface of pretreated polyester fabric. The process of seeding was followed by the low temperature hydrothermal method for the growth of nanocalcite for the functionalization of fabric. The goal of this study was to improve the hydrophilicity of the nanocalcite photocatalyst that had been grafted onto the surface of polyester fabric (PF) using acidic and basic prewetting techniques. The morphological characteristics, crystalline nature, surface charge density, functional groups of surface-modified nanocalcite @ PF were determined via SEM, XRD, FTIR, and Zeta potential (ZP), respectively. Characterization results critically disclosed surface roughness due to excessive induction of hydroxyl groups, rhombohedral crystal structure, and high charge density (0.721 mS/cm). Moreover, contact angle of nanocalcite @ PF was calculated to be 137.54° while after acidic and basic prewetting, it was reduced to 87.17° and 48.19°. Similarly, bandgap of the as fabricated nanocalcite was found to be 3.5 eV, while basic prewetted PF showed a reduction in band gap (2.9 eV). The solar photocatalytic mineralization of imidacloprid as a probe pollutant was used to assess the improvement in photocatalytic activity of nanocalcite @ PF after prewetting. Response surface methodology was used to statistically optimize the solar exposure time, concentration of the oxidant, and initial pH of the reaction mixture. Maximum solar photocatalytic degradation of the imidacloprid was achieved by basic prewetted nanocalcite @ PF (up to 91.49%), which was superior to acidic prewetted fabric and as-fabricated nanocalcite @ PF. Furthermore, HPLC and FTIR findings further indicated that imidacloprid was decomposed vastly to harmless species by basic prewetted nanocalcite @ PF.

The green synthesis of metal oxide nanoparticles is an eco-friendly, rapid, and cost-effective development of novel technologies. The catalyst of nickel oxide (NiO) nanoparticles has been synthesized by the green route's method using Lantana camara Linn and nickel chloride. It was found that plant-mediated synthesis of nickel oxide nanoparticles can greatly enhance the antibacterial and photocatalytic activity at very low concentrations. The synthesized plant-mediated NiO nanoparticle was characterized by the structural and optical properties, morphology, and composition of NiO nanoparticles (NPs) with the help of various techniques such as Ultra Violet (UV) spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Particle Size Analyzer (PSA), Fluorescence Spectroscopy (FL) and the photocatalytic activity studies were investigated. The antimicrobial activity was carried out against Gram-positive and Gram-negative bacteria and NiO NPs showed inhibitory activity in both strains of bacteria with excellent selectivity against Gram-positive bacteria.

The purpose of this study is to present an “environmental catalyst” possessing both thermocatalytic activity and visible-light activity for the decomposition of organic pollutants. Molecule-sized MnOx clusters are highly dispersed on the surface of TiO2 (anatase/rutile = 4/1 w/w, P-25, Degussa) by the chemisorption-calcination cycle technique using Mn(acac)3 complex as a precursor (MnOx/TiO2). The thermo- and photo-catalytic activities of MnOx/TiO2 were studied for the degradation of 2-naphthol used as a model water pollutant. In contrast to the FeOx/TiO2 system, MnOx/TiO2 exhibits high thermocatalytic activity exceeding those of bulk β-β-MnO2 and Mn2O3. Also, visible-light activity is induced by the surface modification of TiO2 with MnOx clusters, whereas its UV-light activity decreases.

Photocatalytic optical fibers are promising materials for degrading organic pollutants in wastewater, owing to their low light mass transfer resistance, their high efficiency of light utilization, and their inhibition of photocatalyst deactivation. In particular, optical fibers have been applied for the removal of phenols, dyes, organic acids and antibiotics in wastewater. Yet, optical fibers have limitations such as poor photocatalytic activity and low sustainability. Here, we review the principle and use of photocatalytic optical fibers, including photocatalytic quartz and plastic optical fibers, for the degradation of the organic pollutants in water. We present methods to enhance photocatalytic activity, light utilization efficiency, and adhesion strength by using TiO2-based photocatalytic coatings.

Anatase/rutile mixed-phase TiO2 nanoparticles were synthesized through a simple sol-gel route with further calcination using inexpensive titanium tetrachloride as a titanium source, which effectively reduces the production cost. The structural and optical properties of the prepared materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis adsorption. The specific surface area was also analyzed by Brunauer–Emmett–Teller (BET) method. The anatase/rutile mixed-phase TiO2 nanocomposites containing of rod-like, cuboid, and some irregularly shaped anatase nanoparticles (exposed 101 facets) with sizes ranging from tens to more than 100 nanometers, and rod-like rutile nanoparticles (exposed 110 facets) with sizes ranging from tens to more than 100 nanometers. The photocatalytic activities of the obtained anatase/rutile mixed-phase TiO2 nanoparticles were investigated and compared by evaluating the degradation of hazardous dye methylene blue (MB) under ultraviolet light illumination. Compared to the commercial Degussa P25-TiO2, the mixed-phase TiO2 nanocomposites show better photocatalytic activity, which can be attributed to the optimal anatase to rutile ratio and the specific exposed crystal surface on the surface. The anatase/rutile TiO2 nanocomposites obtained at pH 1.0 (pH1.0-TiO2) show the best photocatalytic activity, which can be attributed to the optimal heterojunction structure, the smaller average particle size, and the presence of a specific exposed crystal surface. The enhanced photocatalytic activity makes the prepared anatase/rutile TiO2 photocatalysts a potential candidate in the removal of the organic dyes from colored wastewater.

This article reviews the recent developments in the synthesis, antibacterial activity, and visible-light photocatalytic bacterial inactivation of nano-zinc oxide. Polycrystalline wurtzite ZnO nanostructures with a hexagonal lattice having different shapes can be synthesized by means of vapor-, liquid-, and solid-phase processing techniques. Among these, ZnO hierarchical nanostructures prepared from the liquid phase route are commonly used for antimicrobial activity. In particular, plant extract-mediated biosynthesis is a single step process for preparing nano-ZnO without using surfactants and toxic chemicals. The phytochemical molecules of natural plant extracts are attractive agents for reducing and stabilizing zinc ions of zinc salt precursors to form green ZnO nanostructures. The peel extracts of certain citrus fruits like grapefruits, lemons and oranges, acting as excellent chelating agents for zinc ions. Furthermore, phytochemicals of the plant extracts capped on ZnO nanomaterials are very effective for killing various bacterial strains, leading to low minimum inhibitory concentration (MIC) values. Bioactive phytocompounds from green ZnO also inhibit hemolysis of Staphylococcus aureus infected red blood cells and inflammatory activity of mammalian immune system. In general, three mechanisms have been adopted to explain bactericidal activity of ZnO nanomaterials, including direct contact killing, reactive oxygen species (ROS) production, and released zinc ion inactivation. These toxic effects lead to the destruction of bacterial membrane, denaturation of enzyme, inhibition of cellular respiration and deoxyribonucleic acid replication, causing leakage of the cytoplasmic content and eventual cell death. Meanwhile, antimicrobial activity of doped and modified ZnO nanomaterials under visible light can be attributed to photogeneration of ROS on their surfaces. Thus particular attention is paid to the design and synthesis of visible light-activated ZnO photocatalysts with antibacterial properties