Investigation of physicochemical properties of ZnO nanoparticles for gas sensor applications

Zinc oxide nanoparticles (ZnO NPs) have been prepared using a natural tea-assisted auto-combustion method. Prepared ZnO NPs were heated at 350 °C and their structural, vibrational, optical, and morphological properties were investigated. The role of natural tea and heat treatment on the physicochemical properties of ZnO NPs was analyzed. The structure, lattice constant, and crystallite size of ZnO NPs were investigated through X-ray diffraction analysis (XRD). The crystallite size of as-synthesized and heat-treated samples are found to be 5.8 and 9.4 nm. The functional groups and vibrational modes of prepared and heat-treated ZnO NPs were analyzed by FT-IR spectroscopy. The energy band gap of as-synthesized is 3.13 eV while it is 3.08 eV for the heat-treated ZnO NPs. The nanoscale range of the particles is confirmed by TEM micrographs of heat treated ZnO NPs, which agree well with the crystallite size determined by XRD. The particle colloidal stability of heat treated ZnO NPs is good. The sensing ability of ZnO NPs was evaluated with various sensor measurements, and the ZnO NPs showed good sensor response to different gases. ZnO NPs show outstanding sensor response to ethanol gas compared to the other test gases.