Chemoresistive NH3 gas sensor at room temperature based on the carbon gel-TiO2 nanocomposites

A resistive sensor based on films of carbon gel-TiO2 nanocomposites prepared with different percentages of TiO2 by a sol-gel process, was developed to determine ammonia gas. A thin film of carbon gel-TiO2 nanocomposites dispersed in poly(vinylidenfluoride) and deposited on glass slides containing silver electrodes are used as NH3 sensor. The resistance of the films at a potential difference of 1.0 V was determined in the presence of NH3, CO2, C2H5OH, CH3OH, C4H10O and C4H8O2 gases with concentrations in the range of 0–1000 ppm. The response of the resistive sensor expressed as response sensitivity -Response (%)- increases linearly as the gas concentration increases from 0.2 to 18.8. The sensor response is obtained at room temperature, 25ºC, and under UV irradiation. The response increase with the increase of wt.% of TiO2 in the material. The sensor based on a carbon-TiO2 nanocomposite with 50 wt.% of TiO2 presents the best performance in terms of sensitivity (sensor response ~18.8 for 100 ppm NH3), selectivity (selectivity factor for NH3 is about ~5.8 against C4H8O2, C4H10O and ~4.5 for CO2, CH3OH, C2H5OH), stability (both long-term and short-term) and influence of humidity. Additionally, this prepared film possesses the advantages of low power consumption, cost-effectiveness and selective detection ability for NH3 sensing.