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This study focuses on zinc-doped tin oxide nanoparticles (Zn-SnO 2 NPs) as promising humidity sensors. Through a chemical coprecipitation method, we synthesized Zn-SnO 2 NPs and explored the influence of calcination temperature on their properties. X-ray diffraction confirmed the tetragonal rutile structure, and morphological analysis revealed a cauliflower-like morphology with enhanced porosity after calcination. UV-Visible absorption spectroscopy and photoluminescence measurements demonstrated a blue shift in the absorption peak and significant emission peaks related to oxygen vacancies, indicating improved humidity sensing potential as increasing the calcination temperature. The controlled calcination process led to successful outcomes, precisely tuning the NPs structure and optical behavior for enhanced humidity sensing capabilities. Conductivity studies have highlighted the semiconducting behavior of the NPs and observed that an increase in calcination temperature reduces their conductivity. Notably, humidity sensing experiments revealed a remarkable response of 93% and an exceptional response time of 30 seconds for the calcined NPs, surpassing the uncalcined sample. The sensing mechanism involving physisorption, chemisorption, and capillary condensation of water molecules on the NPs surface was validated. Moreover, the stability test over two month demonstrated consistent and highly stable humidity sensing response, reaffirming the NPs potential as effective and reliable humidity sensors. [Display omitted] • Zn-SnO 2 NPs were synthesized by chemical co-precipitation method. • The effect of calcination temperature on morphological & optical traits was studied. • Surface defects & mesoporous morphology play an important role in humidity sensing. • Calcinated NP sensor's are high sensitive & reactive to humidity variations. • The high sensitivity low response time is achieved. [ABSTRACT FROM AUTHOR]

• Fabrication of ZnO and Cr doped ZnO NPs by adopting green and chemical methods. • Structural & optical contrasts in green vs. chemically synthesized ZnO & Cr-ZnO NPs. • Crucial insights into Cr-doped ZnO NPs behaviour. • Green Cr doped ZnO NPs: future photodegradation catalyst. • Potent anticancer activity by synthesized NPs. Herein, we focused on the combined investigation of physicochemical traits and multifunctional bioactivity of ZnO and Cr-doped ZnO NPs synthesized by chemical and green synthesis methods. The green synthesis was accomplished by utilizing Azadirachta Indica leaf extracts which include the phytochemicals azadirachtin and nimbolide function as prominent therapeutic agents in diagnosis. The XRD and TEM analysis evidences all the prepared NPs exhibit hexagonal wurtzite structure, and the change in crystallinity of ZnO NPs with Cr substitution has been examined. The optical properties show that Cr inclusion effectively changes the optical band gap of pure ZnO NPs, confirming the quantum confinement effect. The synthesized NPs were employed to investigate photocatalytic degradation of Rhodamine B (Rh B) dye in an aqueous environment under UV irradiation. The Rh-B dye effectively degraded within 180 min in the presence of synthesized nano catalyst at room temperature. Further, the synthesized NPs were subjected to investigate their bio-potency for microbicidal and cytotoxicity properties. The biosynthesized Cr-ZnO NPs exhibit significant cytotoxicity against A-549 lung cancer cells with the lowest IC 50 value (21.79 µg/ml) and also demonstrate good antioxidant activity with the highest percentage of inhibition 81.23 % as measured by the DPPH scavenging assay in contrast to other NPs. In addition, the chemically synthesized Cr-ZnO NPs found the highest inhibition activity (90.78 %) for antidiabetic efficiency of Alpha-amylase enzyme assay and also shows significant antibacterial activities with a higher zone of inhibition (17 mm) against gram-positive Bacillus cereus over other samples. Thus, this study highlights ZnO NPs versatile attributes, paving the way for promising biomedical and environmental uses. [Display omitted] [ABSTRACT FROM AUTHOR]

This study is aimed to synthesize zinc oxide nanoparticles (ZnO NPs) from Aloe barbadensis Miller leaf extract using the green synthesis method at room temperature. The biosynthesized NPs are characterized by X‐ray diffraction (XRD), UV–vis spectroscopy (UV–vis), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscope (SEM). The XRD pattern has revealed the hexagonal wurtzite structure with a crystallite size of 16 nm for synthesized ZnO NPs. The FTIR results display the formation of ZnO NPs and the presence of other functional groups. The UV–vis absorption spectrum shows an absorption band at 347 nm and the value of the bandgap is found to be 3.75 eV. The surface morphology of synthesized NPs is visualized by SEM images, it is observed that most of the NPs are needle in shape. Further, these NPs will find applications in biosensing and photocatalytic activity. [ABSTRACT FROM AUTHOR]

In the present work, zinc‐ferrite [ZnFe2O4] nanoparticles (NPs) are synthesized by the chemical coprecipitation method. The x‐ray diffraction pattern affirms the arrangement of the cubic spinel structure. SEM micrographs reveal the polyhedral crystal‐like shape. FTIR spectrum confirm the characteristic functional groups present in the spinel zinc ferrite NPs. The UV‐visible absorption and fluorescence spectra confirm that zinc ferrite NPs are optically active and hence can possess potential applications in light‐harvesting and photocatalytic activity. [ABSTRACT FROM AUTHOR]