Tin Dioxide Functionalized Single-Walled Carbon Nanotube (SnO2/SWNT)-Based Ammonia Gas Sensors and Their Sensing Mechanism

Tin oxide functionalized single-walled carbon nanotubes (SWNTs) were synthesized on prefabricated microelectrodes by an electrochemical process. The shape, morphology, valence state and crystal structure of tin oxide were controlled by varying the deposition potential (E), charge density (C), and subsequent calcining temperature (T) and their structure-related sensing performance toward ammonia (NH3) gas was characterized at 25 degrees C. Optimal sensing performance was obtained under the conditions of E = -0.625 V, C = 0.125 C/cm(2), T = 400 degrees C. The underlying NH3 sensing mechanisms of the SnO2/SWNTs hybrid nanostructures were studied, indicating that the higher Sn2+ dopants in SnO2 (obtained at a higher applied potential of -0.625 V) in the oxides as well as the greater active surface area (obtained at the optimal charge density of 0.125 C/cm(2)) and the lowest calcining temperature of 400 degrees C are the key factors in improving the sensing performance. Selectivity of the gas sensors was determined by exposing them to CO and NO2 at room temperature. (C) 2014 The Electrochemical Society. All rights reserved.