Highly Sensitive Diethylamine Detection at Room Temperature Using g-C₃N₄ Nanosheets Decorated with CuO Hollow Polyhedral Structures

Abstract

Chemiresistive-based metal oxide semiconductor (MOS) gas sensors are widely used in gas sensing due to their advantageous properties. Graphitic carbon nitride (g-C 3 N 4 ) and metal oxide heterostructure materials can improve charge transport properties, selectivity, and sensitivity in MOS gas sensor materials. Herein, for the first time, CuO hollow polyhedral structures (HPSs) were synthesized via a hydrothermal technique and annealed at different temperatures, with the 400 °C annealed (CuO-400 HPSs) demonstrating remarkable sensing capabilities for diethylamine (DEA) gas at room temperature (RT). The x-g-C 3 N 4 nanosheets were decorated with CuO HPSs in varying amounts (x = 0.8, 1.8, 2.1, and 3.1 wt %) and then annealed at 400 °C for x-g-C 3 N 4 -CuO-400 hollow polyhedral heterostructures (HPHSs). Indeed, among the synthesized samples, the 1.8%-g-C 3 N 4 -CuO-400 HPHSs have a higher sensitivity to DEA (resistance change in gas (R g ) and air (R a ); R g /R a = 65 @ 20 ppm), a low detection limit (R g /R a = 6 @ 500 ppb), wide dynamic response (R g /R a = 190 @ 80 ppm), strong stability (30 days), and 21.6 times higher sensitivity than pure CuO at RT toward 20 ppm of DEA. The exceptional gas-sensing behavior can be attributed to various factors, including controlled annealing conditions that result in the formation of well-defined structures and greater porosity, efficient charge transfer properties resulting from an optimized ratio of g-C 3 N 4 to CuO in HPHSs, an abundance of defects, unsaturated Cu sites, and synergistic effects. The study presents a universal strategy for generating sensitive and selective g-C 3 N 4 -based composite materials for low-temperature gas sensors.