A Selective Resistive CO Gas Sensor Based on Bio-waste Derived 2D-CaO Nanoplates

Abstract

This study marks the inaugural documentation of the synthesis of fine calcium oxide (CaO) nanoplates (NPs) with average length of ≈ 97 nm and breadth of ≈ 50 nm derived from eggshell bio-waste, without using additional chemical agents. This environment friendly approach not only exemplifies sustainable material science but also paves the way for the development of a highly specific sensor capable of detecting minute concentration of CO gas, offering both ecological and economic benefits. The fabricated CaO NPs showed cubic crystal phase and band gap ≈ 3.65 eV, lattice constant ≈ 0.485 nm with semiconducting nature having activation energy of ≈ 0.21 eV. Prominent defects of oxygen vacancies and calcium interstitials were observed. The resistive gas sensor made with CaO NPs showed selective detection of CO among different gases (CO2, NH3, CO, NO2) and VOCs (acetone, ethanol). The device showed highest response (≈ 3.45 ± 0.17) at the operating temperature of 300ºC for 150 ppm of CO gas. The device response time varies from (75 ± 3.75) s to (140 ± 7) s, whereas the recovery time varies (80 ± 4.1) s and (255 ± 12.75) s. The device showed sensitivity of 0.43 ± 0.094 ppm−1 with LOD ≈ 14.4 ± 1.15 ppm. The sensor showed long time stability along with good anti-humidity responsive nature.