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ZnO is a potential candidate for providing an economic and environmentally friendly substitute for energy storage materials. Therefore, in this work, Fe-doped ZnO nanostructures prepared using the microwave irradiation procedure were investigated for structural, morphological, magnetic, electronic structural, specific surface area and electrochemical properties to be used as electrodes for supercapacitors. The X-ray diffraction, high-resolution transmission electron microscopy images, and selective-area electron diffraction pattern indicated that the nanocrystalline structures of Fe-doped ZnO were found to possess a hexagonal wurtzite structure. The effect of Fe doping in the ZnO matrix was observed on the lattice parameters, which were found to increase with the dopant concentration. Rods and a nanosheet-like morphology were observed via FESEM images. The ferromagnetic nature of samples is associated with the presence of bound magnetic polarons. The enhancement of saturation magnetization was observed due to Fe doping up to 3% in correspondence with the increase in the number of bound magnetic polarons with an Fe content of up to 3%. This behavior is observed as a result of the change in the oxidation state from +2 to +3, which was a consequence of Fe doping ranging from 3% to 5%. The electrode performance of Fe-doped ZnO nanostructures was studied using electrochemical measurements. The cyclic voltammetry (CV) results inferred that the specific capacitance increased with Fe doping and displayed a high specific capacitance of 286 F·g−1 at 10 mV/s for 3% Fe-doped ZnO nanostructures and decreased beyond that. Furthermore, the stability of the Zn0.97Fe0.03O electrode, which was examined by performing 2000 cycles, showed excellent cyclic stability (85.0% of value retained up to 2000 cycles) with the highest specific capacitance of 276.4 F·g−1, signifying its appropriateness as an electrode for energy storage applications.

Molybdenum disulfide (MoS2) has gained attention for its promising gas-sensing capabilities due to its high surface area and tunable electronic properties. In this study, we investigate the time-dependent growth (under constant conditions) of sputtered MoS2 films on ZnO nanorods and their impact on NO2 sensing performance. ZnO nanorods, synthesized via a hydrothermal method, provide a high-surface-area template to enhance charge transport and gas adsorption. Gas-sensing experiments revealed a strong correlation between MoS2 thickness and NO2 response, with the 25-min-sputtered MoS2 film exhibiting the highest response of 20.9%. The synergistic interaction between MoS2 and ZnO nanorods facilitated charge transfer and enhanced adsorption sites for NO2 molecules. These findings emphasize the critical role of time-dependent growth of MoS2 film in modulating gas-sensing performance and provide insights into designing high-sensitivity NO2 sensors at room temperature. This study contributes to the development of hybrid MoS2/ZnO nanostructures for next-generation environmental monitoring applications.

Developing various nanosensors with superior performance for accurate and sensitive detection of some physical signals is essential for advances in electronic systems. Zinc oxide (ZnO) is a unique semiconductor material with wide bandgap (3.37 eV) and high exciton binding energy (60 meV) at room temperature. ZnO nanostructures have been investigated extensively for possible use as high-performance sensors, due to their excellent optical, piezoelectric and electrochemical properties, as well as the large surface area. In this review, we primarily introduce the morphology and major synthetic methods of ZnO nanomaterials, with a brief discussion of the advantages and weaknesses of each method. Then, we mainly focus on the recent progress in ZnO nanosensors according to the functional classification, including pressure sensor, gas sensor, photoelectric sensor, biosensor and temperature sensor. We provide a comprehensive analysis of the research status and constraints for the development of ZnO nanosensor in each category. Finally, the challenges and future research directions of nanosensors based on ZnO are prospected and summarized. It is of profound significance to research ZnO nanosensors in depth, which will promote the development of artificial intelligence, medical and health, as well as industrial, production.

Transition metal dichalcogenide (TMD) MoS2 and WS2 monolayers (MLs) deposited atop of crystalline zinc oxide (ZnO) and graphene-like ZnO (g-ZnO) substrates have been investigated by means of density functional theory (DFT) using PBE and GLLBSC exchange-correlation functionals. In this work, the electronic structure and optical properties of studied hybrid nanomaterials are described in view of the influence of ZnO substrates thickness on the MoS2@ZnO and WS2@ZnO two-dimensional (2D) nanocomposites. The thicker ZnO substrate not only triggers the decrease of the imaginary part of dielectric function relatively to more thinner g-ZnO but also results in the less accumulated charge density in the vicinity of the Mo and W atoms at the conduction band minimum. Based on the results of our calculations, we predict that MoS2 and WS2 monolayers placed at g-ZnO substrate yield essential enhancement of the photoabsorption in the visible region of solar spectra and, thus, can be used as a promising catalyst for photo-driven water splitting applications.

Due to its antibacterial activity against clinical bacterial pathogens at the time of tissue development, zinc oxide (ZnO) is considered one of the most important metal oxide nanostructured materials. In this study, ZnO nanostructures were prepared using Aloe vera gel juice, which is easy, inexpensive, and ecofriendly. The nanostructures of ZnO were characterized using a variety of analytical techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and dynamic light scattering (DLS). As a result of the XRD study, the hexagonal phase of ZnO with the structure of wurtzite has been identified. ZnO material with high heterogeneity morphology has been observed by SEM analysis. As-prepared ZnO nanostructures were tested for their antibacterial activity against the newly discovered pathogen of catfish. A ZnO sample prepared with a high concentration of Aloe vera gel possessed an inhibition zone of 13.21±0.04 mm, whereas a ZnO sample prepared with a low concentration of Aloe vera juice had an inhibition zone of 6.23±0.02 mm and a pure ZnO sample had an inhibition zone of 3.31±0.03 mm. Furthermore, we examined the effectiveness of the ZnO nanostructures on bacterial strains based on the type of nanoparticles applied to the commercial strains. In addition to their modified surface properties, small particle size, and highly toxic effects for the killingof bacterial cell growth, the Aloe vera juice assisted ZnO nanostructures demonstrated excellent antibacterial activity against the catfish pathogens

This paper studied the photocatalytic degradation of methylene blue (MB) using polymeric membrane impregnated with ZnO nanostructures under UV-light and sunlight irradiation. ZnO nanoparticles and ZnO nanowires were prepared using the hydrothermal technique. Cellulose acetate polymeric membranes were fabricated by the phase inversion method using dimethylformamide (DMF) as a solvent and ZnO nanostructures. The structural properties of the nanostructures and the membranes were investigated using XRD, SEM, FTIR, and TGA measurements. The membranes were tested for photocatalytic degradation of MB using a UV lamp and a sunlight simulator. The photocatalytic results under sunlight irradiation in the presence of cellulose acetate impregnated with ZnO nanoparticles (CA-ZnO-NP) showed a more rapid degradation of MB (about 75%) compared to the results obtained under UV-light irradiation degradation (about 30%). The results show that CA-ZnO-NP possesses the photocatalytic ability to degrade MB efficiently at different levels under UV-light and sunlight irradiation. Modified membranes with ZnO nanoparticles and ZnO nanowires were found to be chemically stable, recyclable, and reproducible. The addition of ZnO nanostructure to the cellulose membranes generally enhanced their photocatalytic activity toward MB, making these potential membranes candidates for removing organic pollutants from aqueous solutions.

Non-enzymatic glucose has been detected using highly sensitive ZnO/Zn nanostructures produced with the cold atmosphere plasma (CAP) technique. Electrochemical nanobiosensors use an electrode as a transducer and a biological element as a diagnostic component. This work presents an interesting and novel method for the surface modification of Zn foil using dielectric barrier discharge (Ar/O) plasma at different exposure times, which leads to the formation of a thin layer of ZnO. Many tests were performed to characterise and ensure the efficiency of the samples as biological sensors. The photoluminescence (PL) test for ZnO/Zn nanostructures showed a shift at the vertex, confirming the reaction in all PL spectra with a strong UV emission peak. High-resolution XPS spectra contained Zn 2p 1/2 , Zn 2p 3/2 and O s 1 peaks. The Raman spectra contained two strong peaks, E 1 high at 77.5 nm and E 2 low at 522 nm, and one weak peak, A 1 Low at 1524.8 nm. Distributed nanosheets were observed using FE-SEM at an exposure time of 30 s with thickness ranging from 16.3 to 80.7 nm and nanoparticles of different sizes ranging from 31 to 259.3 nm at an exposure time of 60 s. The shape of the nanoparticles changed from nanoparticles to a form resembling brain fibrosis with diameters between 75.7 and 189.8 nm at 90 s. The sensing current of the ZnO/Zn nanostructure biosensors increased with plasma exposure times of 30, 60, and 90 s to 1.99, 2.3, and 2.9 mA respectively. The response time changed with plasma exposure time (0.82, 0.32, and 0.48 s), as did the correlation coefficient ( R 2 = 0.8922, 0.9432, and 0.9476). Graphical abstract

Anti-bacterial activity of biologically synthesized zinc oxide (ZnO) nanostructures has engrossed great attention around the globe due to distinctive nanotechnological applications. Biogenic ZnO nanostructures have prominent anti-bacterial properties as compared to bulk because small sized nanostructures exhibit larger surface area leading to improved particle surface-reactivity. This study reveals that biologically synthesized ZnO nanostructures are bio-compatible, stable and have longer shelf life due to presence of phytochemicals which acts as stabilizing and capping agents during synthesis process. The anti-bacterial mechanism of ZnO nanostructures includes production of reactive oxygen species (ROS) such as hydrogen peroxide H 2 O 2 , OH − and O 2 −2 . The ROS provides major toxicity mechanism which includes destruction of cell wall due to interaction of ZnO nanostructures. Sometimes, ZnO nanostructures have increased anti-bacterial activity due to surface imperfections and ROS generation in dark. Interaction between ZnO nanostructures and bacterial cell causes mitochondrial weakness, intra-cellular outflow, and oxidative stress which eventually inhibits bacterial growth and kills the whole cell. This review describes anti-bacterial activity of biologically synthesized ZnO nanostructures by previously reported literature and tests used to examine anti-bacterial activity, influence of UV illumination, ZnO unique features i.e. size, concentration, morphology, and defects. Furthermore, it also presents significant anti-bacterial applications of ZnO nanostructures particularly in food packaging industry, pharmaceutical industry and other health care applications.

In this work, ZnO has been synthesized with a variety of nanomorphologies, including nanorods (NRs), nanodiscs (NDs), and nanorods/nanodiscs (NRs/NDs), to enhance CO 2 gas detection at room temperature. The ZnO nanostructures were made by combining the successive ionic layer adsorption and reaction (SILAR) strategy and the chemical bath deposition (CBD) method. The time of CBD varied from 6 to 12 h. Several techniques, including X-ray diffraction (XRD) spectroscopy, energy-dispersive X-ray (EDAX) spectrometry, optical spectrophotometer, and field emission scanning electron microscopy (FE-SEM), were used to investigate the manufactured ZnO nanostructures. The FE-SEM demonstrates that by increasing the deposition period of CBD from 6 to 12 h, the shape of ZnO nanostructures changed from NRs/NDs to NDs. According to the XRD, all ZnO nanostructured samples exhibit hexagonal wurtzite structures with (002) preferred orientation. Additionally, the crystallite size along orientation (002) increases from 63 to 65 nm as the deposition duration increases from 6 to 12 h. The bandgap of ZnO was reduced from 3.62 to 3.31 eV. When the deposition time is increased from 6 to 12 h, the sensitivity increases from 8.46 to 28.7%, the detection limit rises from 4.65 to 9.95 SCCM, and the limit of quantification rises from 15.52 to 33.16 SCCM. Moreover, the ZnO @ 12 h sensors has excellent selectivity as well since it reacts to CO 2 with a higher response sensitivity than it does to other gases like hydrogen and ammonia.

In recent years, organic pollutants have become a global problem due to their negative impact on human health and the environment. Photocatalysis is one of the most promising methods for the removal of organic pollutants from wastewater, and oxide semiconductor materials have proven to be among the best in this regard. This paper presents the evolution of the development of metal oxide nanostructures (MONs) as photocatalysts for ciprofloxacin degradation. It begins with an overview of the role of these materials in photocatalysis; then, it discusses methods of obtaining them. Then, a detailed review of the most important oxide semiconductors (ZnO, TiO2, CuO, etc.) and alternatives for improving their photocatalytic performance is provided. Finally, a study of the degradation of ciprofloxacin in the presence of oxide semiconductor materials and the main factors affecting photocatalytic degradation is carried out. It is well known that antibiotics (in this case, ciprofloxacin) are toxic and non-biodegradable, which can pose a threat to the environment and human health. Antibiotic residues have several negative impacts, including antibiotic resistance and disruption of photosynthetic processes.