Facile synthesis of improved room temperature gas sensing properties of TiO2 nanostructures: Effect of acid treatment

Abstract

TiO2 nanoparticles were synthesized via a simple hydrothermal method in a sodium hydroxide (NaOH) aqueous solution and washed with distilled water and different concentrations of hydrochloric acid which acted as the morphological/crystallographic controlling agent. Microscopy analysis showed that the size of the TiO2 nanoparticles could be easily tailored and tuned by varying the HCl concentration. The phase transformation from a mixture of anatase and rutile phases to pure anatase phase was observed at higher HCl concentration. The particle sizes were reduced while the Brunauer–Emmett–Teller surface area increased when increasing the HCl concentration, thus resulting in higher sensing response and selectivity to NO2 at room temperature. The X-ray photoelectron spectroscopy, photoluminescence and electron paramagnetic resonance studies also revealed that the 1.0 M sample contain high relative concentration of oxygen vacancy and Ti4+ and Ti3+ interstitial defect states which played a vital role modulating the sensing properties.