Acidic Gas Determination Using Indium Tin Oxide-Based Gas Sensors

This work has presented gas sensors based on indium tin oxide (ITO) for the detection of SO₂ and NO₂. The ITO gas-sensing material was deposited by radio frequency (RF) magnetron sputtering. The properties of gas sensing could be improved by increasing the ratio of SnO₂. The response characteristics of the gas sensor for detecting different concentrations of NO₂ and SO₂ were investigated. In the detection of NO₂, the sensitivity was significantly improved by increasing the SnO₂ ratio in ITO by 5%, and the response and recovery time were reduced significantly. However, the sensitivity of the sensor decreased with increasing SO₂ concentration. From X-ray photoelectron spectroscopy (XPS) analysis, the gas-sensitive response mechanisms were different in the atmosphere of NO₂ and SO₂. The NO₂ was adsorbed by ITO via physisorption but the SO₂ had a chemical reaction with the ITO surface. The gas selectivity, temperature dependence, and environmental humidity of ITO-based gas sensors were systematically analyzed. The high detection sensitivity for acidic gas of the prepared sensor presented great potential for acid rain monitoring.