Interlinked Polyaniline/ZnO Nanorod Composite for Selective NO2 Gas Sensing at Room Temperature

Chemiresistive gas sensing has attracted extensive research attention in recent years, and the facile low-cost synthesis of sensitive materials is important for realizing practical use. One feasible approach is to create a gas-sensing nanocomposite network by infusing an easily processable conducting polymer into a solution-grown interlinking metal oxide nanomaterial. In this work, a polyaniline (PANi) and ZnO nanorod (NR) composite is synthesized for selective UV-activated NO2 gas sensing at room temperature. The nanocomposite comprises interlinking ZnO NRs that are partially covered by PANi, thus forming a charge transport network with abundant gas adsorption sites. Uniform and interlinking ZnO NRs are grown on a prepatterned silicon substrate by using a hydrothermal method, and PANi is prepared by using an in situ oxidative polymerization method. A PANi/ZnO 0.5 nanocomposite with uniform morphology is obtained by drop-casting a PANi solution on the ZnO NRs. The nanocomposite exhibits selective NO2 gas toward various gases including CH2O, NO, and NH3. The responses are 130% and 20920% for 0.05 and 2.5 ppm NO2, respectively. The low-concentration linear sensitivity is 11.7% ppb–1. Based on the Langmuir adsorption model, the adsorption and the desorption constants are determined to be 7.65 × 10–3 ppm–1 s–1 and 1.07 × 10–2 s–1, respectively. The excellent gas-sensing performance of the PANi/ZnO 0.5 nanocomposite is attributed to the formation of abundant p–n heterojunction adsorption sites.