A comparative study on enhancer and inhibitor of glycine–nitrate combustion ZnO screen-printed sensor: detection of low concentration ammonia at room temperature

Abstract

We report a comparative study on enhancing and inhibiting the sensing performance of Sr-doped ZnO (Sr<inf>0.01</inf> Zn<inf>0.99</inf>O) and RuO<inf>2</inf>-activated Sr-doped ZnO heterostructured sensors towards the low concentration (? 50 ppm) of ammonia gas at ambient. Sub-microns sized with high specific surface area, high reactive, oxygen-deficient Sr-doped ZnO particles were synthesized at low temperature (196 °C) through facile glycine–nitrate solution combustion synthesis (SCS) method. Porous, adhered screen-printed film of Sr-doped ZnO with optical bandgap (3.22 eV) was dip-coated using 0.02 M RuCl<inf>3</inf> aqueous solution to obtain RuO<inf>2</inf> activation. Smaller crystallite size and lesser lattice distortion obtained with Sr-doping in ZnO enhance the gas response (S = 71) towards the 50 ppm of ammonia gas at room temperature. RuO<inf>2</inf>-activated Sr-doped ZnO sensor associated with lesser oxygen vacancies and a lower concentration of chemisorbed oxygen species due to passivation layer and no-spill-over activity of RuO<inf>2</inf>, which inhibits the gas response from 71 to 3. Sr-doped ZnO-based sensor shows high selectivity towards ammonia against 50 ppm of volatile organic compound (VOCs) vapor. Expeditious sensor kinetics (response time and recovery time) in the Sr-doped ZnO sensor was observed, in which smaller crystallite size offers a shorter distance for the diffusion of oxygen vacancies (V<inf>o</inf>). Ultra-high-sensitive and selective sensors with ease and economical fabrication offer feasibility in industries and domestic applications where detection of the less concentration ammonia vapor is crucial. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.