Solution-Processed Metal Oxides and Their Thin Films/Coatings Towards Antifouling and Gas Sensing Applications

Abstract

In the current study, metal oxides and their thin films/coatings were developed through solution-phase methods as an approach to antifouling and gas sensing applications. Thermal decomposition-processed facile spray pyrolyzed pure WO3 films were successfully fabricated by utilizing minimal sophisticated facilities. Compared to uncoated substrates, all the coated substrates exhibited an enhancement in scratch hardness. The attained relatively better scratch hardness was ascribed to the existence of a well-established WO3 film. The demonstrated WO3 films were hydrophilic natured (WCA < 31°) and after chemical modification with OTS, the films revealed hydrophobicity (WCA > 120°) due to the formation of water-repellant OTS-SAM on the surface. Solution-combustion-processed spin coated pristine and Ti-doped ZnO films responded to NH3 gas at room temperature. Pristine ZnO film revealed better gas sensing performance than doped films at all concentrations of NH3 gas. The maximum gas response of 34.7 and high selectivity were perceived in pristine ZnO film at 100 ppm of NH3 gas. Room temperature detection of NH3 gas was also accomplished in respective spin-coated air and vacuum-annealed pristine, Nb-doped TiO2 films fabricated through the solution combustion method. Compared to other films, a relatively superior gas response was traced at all NH3 gas concentrations by vacuum-annealed pristine TiO2 film. The film exhibited the highest gas response of ~16 and selectivity towards 100 ppm of NH3 gas. Solution-combustion-derived spin coated Ti and Zn co-doped In2O3 films were polycrystalline without any secondary dopant oxide phases, and the films revealed transparency (>85%) in the visible region. Screen-printable particle-free aqueous solution combustible inks with a combustion temperature of ~280 °C were utilized to fabricate undoped In2O3, Sn doped In2O3, Zn doped In2O3, Sn and Zn co-doped In2O3 screen- printed films. All the screen-printed films sensed ethanol gas at room temperature, and the undoped screen-printed film performed comparatively better gas sensing. A maximum gas response of 17.3 and high selectiveness towards 100 ppm of ethanol gas were discerned in the stated film. The evolution of the BSO/LBSO phase from the intermediate phases was evidenced between 500 ºC and 600 ºC. The pure BSO/ LBSOphase with non-appearance of intermediate phases was recognized at 800 ºC and above, in LaxBa1-x SnO3-δ (x = 0, 0.05, 0.1 and 0.15) powders, synthesized through the polymerized complex method. A progressive augmentation in the electrical conductivity of BSO-based pellets was recognized with La doping.