Development of highly sensitive ZnO/In2O3 composite gas sensor activated by UV-LED

The photo-responsive behavior of ZnO/In2O3 composite sensors was investigated for detecting low concentrations of NO2 gas under 365 nm UV-LED irradiation at room temperature. The composite samples were prepared by the co-precipitation method with the appropriate components ratio to obtain superior sensing performance. The composition, structure, and optical properties of the synthesized sensing materials were characterized by EDS, XRD, SEM, XPS and UV–vis analyses. In terms of gas sensing performance, the synergistic effects of combined materials led to an enhanced response of the composite sensors, compared to those of pristine ZnO and In2O3 sensors under UV illumination. The considerable improvement in sensor response was attributed to the ZnO role in charge carrier mobility enhancement and low recombination rate of active charge carriers, as well as In2O3 contributions as radiation absorption centers and chemisorption promoters in the composite structure. It was found that the response of the composite gas sensor is largely dependent on the UV irradiance in which increasing the UV flux reduced the response, but shortened the response time.