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 SnO 2 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 SnO 2 nanospheres using tin (II) chloride dihydrate precursor via the co-precipitation deposition technique to form ZnO–SnO 2 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 SnO 2 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.