The present investigation deals with the NO2 gas detection via nanostructured zinc oxide (ZnO) thin films harvested over a glass substrate via a simple and facile successive ion layer adsorption and reaction (SILAR) approach. ZnO nanostructured thin films are developed by different SILAR cycles (ZnO:15, ZnO:30, ZnO:45, ZnO:60). The physicochemical, optical, and morphological properties of prepared thin films are explored by various characterization techniques. The phase purity and grains size are confirmed by X‐ray diffraction (XRD) and Scherrer formula, which reveal the hexagonal phase structure with variant grain size (≈16–21 nm). The surface morphology of deposited films shows the well‐dispersion of ZnO nanoparticles, which is picturized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflectance (ATR). UV–Vis and FTIR spectroscopy elaborates on the optical properties and functional groups of ZnO films, respectively. Further, the sensing ability of ZnO thin films is studied with different concentrations (50–250 ppm) of NO2 gas in the span of 50 ppm by recording the resistance transient. The ZnO:30 thin‐film displays an enhanced gas sensing response of 1.42 GΩ at 100 °C compared to other synthesized films and at different temperature ranges. The ZnO:30 film shows the highly selective response toward the NO2 gas compared to other interference gas species. Thus, the present study highly recommends the investigated method for the ZnO thin film formation to be employed toward NO2 gas sensing.

In this report, we have prepared undoped and Mg-doped ZnO thin films by a modified successive ionic layer adsorption and reaction (SILAR) method. The structural, surface morphological, chemical compositional, and optical properties of pure and Mg-doped ZnO thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), ultraviolet-visible (UV-VIS) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. The XRD patterns of undoped and doped films have wurtzite crystal structures with preferential orientation along the (101) plane, without any secondary phases. Addition of Mg into host ZnO influenced surface morphology of the film. Predominant nanorods-like surface morphology of undoped ZnO turned to be predominant nanoflowers-like surface morphology after addition of Mg. UV-VIS spectra showed that the energy band gap of films increased with increase Mg doping concentration. EDS and FT-IR spectroscopy confirmed the successful Mg doping. Gas sensing properties of the undoped and Mg-doped ZnO thin films were tested based on the electrical resistance changes upon exposure to different concentrations of a NO 2 gas at 200°C operating temperature. Mg-doped ZnO (3 wt%) showed higher response compared to other wt% and exhibited the highest responses of 2.95, 9.51, and 9.93 when exposed to 25, 50, and 100 ppm concentrations of the NO 2 gas at 200°C, respectively. The response/recovery time of the Mg-doped ZnO thin film were 6/75, 14/88, and 14/89 s at 25, 50, and 100 ppm, respectively. Keywords Modified SILAR; Mg-doped ZnO; Flowers-like; NO 2 gas sensor 42 Chemical gas sensors based on semiconducting metal ox-43 ides play a pivotal role in detecting toxic and dangerous 44 substances, where considered promising alternatives to 45 measuring and detecting the amount of environmental pollu-46 tion due to their advantages such as low cost, high sensitivi-47 ty, and fast response [1, 2, 4]. 48 Zinc oxide nanostructures are the best metal oxides, due 49 to their interesting properties such as a wide band gap (ap-50 proximately 3.37 eV), a high exciton binding energy (60 51 meV), non-toxicity, and chemical stability. ZnO nanostruc-476 477 478 479 480 481 All articles published on e-J. Surf. Sci. Nanotechnol. are licensed 482 under the Creative Commons Attribution 4.0 International (CC BY 483 4.0). You are free to copy and redistribute articles in any medium 484 or format and also free to remix, transform, and build upon articles 485 for any purpose (including a commercial use) as long as you give 486 appropriate credit to the original source and provide a link to the 487 Creative Commons (CC) license. If you modify the material, you 488 must indicate changes in a proper way.489

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In this study, Mg doped ZnO thin films were successfully prepared using the modified SILAR approach throughout various numbers of deposition cycles. XRD data shows the prepared films have a ZnO wurtzite hexagonal structure. The crystalline size and crystallinity were found to be increased by increasing the number of deposition cycles. FESEM showed there are nanoparticles and nanorods on the surface, with random distribution in the case of the sample synthesized with 30 cycles, while the agglomeration of nanoparticles to form a maize-like structure and flower-like morphology was predominant in the case of the sample with 40 cycles. The UV-VIS transmittance spectra showed a decrease in transmittance by increasing the number of deposition cycles, and the increment of energy band gap by increasing the number of deposition cycles was found. The response of the samples towards NO2 gas at 200 °C operating temperature was found to be enhanced in the case of the sample prepared at 40 cycles as compared to the sample prepared at 30 cycles.

In the present work, synthesis of CuO, ZnO and CuO/ZnO Nonocomposites and their properties have been investigated. CuO, ZnO and CuO/ZnO NC were synthesized using the co-precipitation method. The nanocomposite materials were structural, morphological and optical properties characterized by X-ray diffraction (XRD), Field Emission Scanning Electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), UV-Vis Spectroscopy. The results of the XRD analysis exhibited that the pure CuO, ZnO and CuO/ZnO NC has a nanometer size with an average of 15.19 nm. The UV-vis analysis showed that the CuO, ZnO and CuO/ZnO NC has a band-gap of 3.31 and 2.35 eV. FTIR investigation revealed that the vibration of ZnO was observed at 561 cm-1 whereas CuO was at 602 cm-1 and composites 612 cm-1. The FESEM-EDX analysis revealed that the ZnO has a hexagonal structure whereas the CuO has a monoclinic structure. HIGHLIGHTS Present investigation deals with CuO, ZnO, and CuO/ZnO composites nanoparticles harvested as Co-Precipitation Method Various characterisation techniques were used to investigate the structural, optical, and morphological features of produced nanoparticles composites Investigation the effects of different properties of the CuO, ZnO and CuO/ZnO composites nanoparticles as well as Co-Precipitation method GRAPHICAL ABSTRACT