Facile one-step hydrothermal synthesis of a ZnO–CuO/cellulose-derived carbon nanocomposite for enhanced room-temperature ammonia sensing

A ternary ZnO/CuO/cellulose-derived carbon (CBC) heterostructure was synthesized via a one-step hydrothermal process for efficient room-temperature detection of ammonia (NH 3 ) with effective selectivity. The integration of n-type zinc oxide and p-type copper oxide within the conductive CBC network facilitates rapid charge transfer while providing abundant adsorption sites. Characterization by XRD, XPS, and TEM confirmed the presence of crystalline ZnO and CuO species uniformly dispersed throughout the porous CBC matrix. The composite sensor demonstrated a response value of 29.2% to 100 ppm NH 3 , with rapid response and recovery times (38 s and 41 s). UV-Vis diffuse reflectance spectroscopy indicated a reduced bandgap (3.10 eV), suggesting enhanced visible-light absorption and improved charge separation. The sensor exhibited reasonable repeatability over a 30-day continuous detection cycle in a 200 ppm ammonia environment. In addition, the sensor maintained stable response characteristics over five consecutive sensing cycles at 200 ppm NH 3 . The synergistic effect of p-n heterojunctions combined with the conductive CBC framework effectively enhances surface reactivity. Meanwhile, although the composite features a flexible and biodegradable carbon backbone, its integration potential for wearable Internet of Things (IoT) devices remains to be thoroughly investigated, and further optimization of mechanical endurance is required before practical application. Overall, this low-cost, eco-friendly composite meets the urgent demand for timely ammonia detection in areas such as environmental assessment.