Actinomorphic ZnO microneedles decorated with SnO2 nanospheres: synthesis, characterization and optical studies

This work has extensively described the construction and characterization of actinomorphic ZnO microneedles decorated with SnO2 nanospheres. Hydrothermal treatment was utilized to fabricate needle-like ZnO microstructures using zinc nitrate tetrahydrate precursor in HMT aqueous solution. ZnO microneedles were then decorated with SnO2 nanospheres using tin (II) chloride dihydrate precursor via the co-precipitation deposition technique to form ZnO–SnO2 heterojunctions. A variety of techniques were employed for characterization of the structure, composition, morphology, and optical properties of the as-produced samples. The XRD and HRTEM results confirmed the formation of the tetragonal rutile SnO2 nanoparticles on the hexagonal wurtzite ZnO microstructures. The existence of surface functional groups and chemical bonding was investigated through FT-IR and Raman spectroscopy. FESEM images confirmed actinomorphic needle-like morphologies for both undecorated and decorated samples. EDS analysis verified the existence of Zn, Sn, and O elements. UV–Vis DRS results revealed a blue shift in the adsorption band-edge towards smaller wavelengths after decorating. Photoluminescence spectroscopy was used to examine the recombination rate of photogenerated electron-holes and the presence of structural defects.