Room temperature operated flexible La-ZnO/MWCNTs sensor for ppb level carbon monoxide detection
Gulshan Verma, Vikas Kumar Pandey, Monsur Islam, Mahesh Kumar, Ankur Gupta
Abstract
Abstract The advancement of gas sensors with ppb level concentration experiences profound challenges. In this research, Lanthanum (La)-Zinc Oxide (ZnO)/multi-walled carbon nanotubes (MWCNTs) composites were successfully fabricated and loaded on a flexible polyimide substrate where interdigitated electrodes (thickness: 300 µ m and spacing: 300 µ m) were prepared using a laser carbonation technique for room temperature (RT) carbon monoxide (CO) gas detection. The synthesized composites were characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, UV – visible spectrophotometry, x-ray diffraction, and Fourier transform infrared spectroscopy. When compared to the La-ZnO composite, the addition of MWCNTs on the synthesized composite-based sensor exhibited ∼8 times higher response than La-ZnO to 100 ppm CO at 27 °C. The response of the La-ZnO/MWCNTs composite sensors to 20 ppm CO was tested at six different relative humidity (RH) levels ranging from 0% to 90% in the increments of 20% RH. These sensors exhibited humidity tolerant properties, as evidenced by their responses to different humidity levels. Even when exposed to 90% RH, the sensor only showed ∼13% reduction in response compared to 0% RH, indicating that it is a humidity tolerant sensor. Furthermore, the La-ZnO/MWCNTs sensor has excellent selectivity and can detect low CO concentrations of 100 ppb. As a result, the proposed high-performance flexible sensor has a lot of potential for use in wearable devices to sense CO gas at RT for trace level detection.