A scalable screen-printed high performance ZnO-UV and Gas Sensor: Effect of solution combustion

Abstract

In the present study, scalable screen-printed Zinc Oxide (ZnO) based sensor was demonstrated to sense ultra-violet irradiation and gases such as ammonia (NH<inf>3</inf>), ethanol (C<inf>2</inf>H<inf>5</inf>OH), liquefied petroleum gas (LPG), chlorine (Cl<inf>2</inf>) and hydrogen sulphide (H<inf>2</inf>S). A facile solution combustion synthesis (SCS) route was adopted to synthesize high purity, homogeneous, nanocrystalline and highly reactive ZnO with favourable morphologies, microstructural parameters for the sensing performance using low-cost and less-violent fuels such as urea, citric acid and glycine. Fuel impacts on uniform particle size distribution, bond length, grain size, lattice strain enhanced the gas sensing potential in the synthesized powders. Films were fabricated by depositing synthesized powders on the glass substrate via screen printing approach using Na-carboxy methyl cellulose as a binder, water as a solvent and annealed at 500 °C for 2 h in ambient. Non-stoichiometric, phase pure and adhered thick films with optical band gap (3.17-3.25 eV) imparted gas sensing properties because of recombination of an electron-hole pair and intrinsic defects. ZnO films obtained from glycine-fuel system exposed to 100 ppm of NH<inf>3</inf>, C<inf>2</inf>H<inf>5</inf>OH, Cl<inf>2</inf> and 50 ppm of H<inf>2</inf>S, exhibited good gas sensitivity of ~8, 5, 3 and 10 at an operating temperature of 50, 100, 200 and 100 °C respectively with a faster response and recovery speed. But, high sensitivity ~6 to 100 ppm of LPG at 350 °C in ZnO films from citric acid fuel-system. ZnO films obtained from glycine fuel system showed a high response to UV irradiation for exposing time of 90s. Low cost, high-performance sensor can be fabricated for the dual applications - alarming to prolonged exposure to harmful UV radiation and detection of a series of toxic and damaging gases. © 2019 Elsevier Ltd