Room Temperature Ammonia Gas Sensing Using MnO<sub>2</sub>-Modified ZnO Thick Film Resistors

Abstract

Pure ZnO thick film, prepared by screen-printing technique, was almost insensitive to NH 3 . Pure ZnO thick films were surface modified with MnO 2 by dipping them into 0.01 M aqueous solution of manganese chloride (MnCl 2 ) for different intervals of time and fired at 500˚C for 12 h. The grains of MnO 2 would disperse around the grains of ZnO base material. The MnO 2 modified ZnO films dipped for 30 min were observed to be sensitive and highly selective to NH 3 gas at room temperature. An exceptional sensitivity was found to low concentration (50 ppm) of NH 3 gas at room temperature and no cross sensitivity was observed even to high concentrations of other hazardous and polluting gases. The effects of surface microstructure and MnO 2 concentrations on the sensitivity, selectivity, response and recovery of the sensor in the presence of NH 3 and other gases were studied and discussed. The better performance could be attributed to an optimum number of surface misfits in terms of MnO 2 on the ZnO films.

Temperature Optimized Ammonia and Ethanol Sensing Using Ce Doped Tin Oxide Thin Films in a Novel Flow Metric Gas Sensing Chamber

“…After the optimum temperature the resistance of the film was observed to increase with increase in temperature as shown in Figure 8. This behaviour in sensor response was reported in various metal oxide systems while sensing various gases [24,29].…”

“…Ammonia {NH 3 } is a colourless gas characterized by irritating or pungent smell. Exposure to high concentration of ammonia is a threat to human health and 50 ppm is the lowest limit of ammonia that can be sensed by perception of smell [29]. Even below this lower limit, it causes irritation to human eyes, to skins, and even to the respiratory system.…”

Enhancement of Electrochemical Oxidation of Ammonia and Ammonium Carbonate over Pt Black Catalysts through Interaction with Manganese Dioxide Nanoparticles

“…13,29 Catalytic composition and mass of composites of Pt black and MnO 2 used in this study are summarized in Table 2. Figures 3 and 4 showed the oxidation activities of ammonia and ammonium carbonate with various types of MnO 2 and composition with respect to Pt black catalyst, respectively.…”

Ultraviolet photodetection characteristics of Zinc oxide thin films and nanostructures

“…This readsorption is a slow process and significantly lengthens the relaxation time constant for the devices [23][24][25][26][27]. This slow transient can be expressed by an exponential function as [22] I t = I d + (I p − I d )e − t τ ( ) Where I (t) is the transient current, I d is the current measured in dark, Ip is the current measured under UV illumination, t is the time after turning off UV light.…”