Enhanced humidity-sensing performance with metallurgy-derived ZnO/GQDs nanocomposite

A cost effective relative humidity sensor based on ZnO/graphene oxide quantum dots (GQDs) was developed by the nanoarchitecturally-metallurgy techniques. Nanospherical-like structure of ZnO powders was prepared from Zn-rich Egyptian ore using the co-precipitation technique. Mono-dispersed graphene quantum dots (GQDs) were optimized by pyrolysis of citric acid. After forming the nanocomposite using a metallurgical pathway, the sensors were fabricated via a simple spin-coating technique. The sensors were tested across a broad humidity range (11 % to 97 % RH) at room temperature, with their sensing behavior evaluated at different frequencies to determine the optimal operating conditions. The humidity sensing characteristics of prepared materials, including sensitivity, stability, hysteresis, response/recovery times, and repeatability, were measured. The sensitivity of fabricated ZnO/GQDs sensors is 0.18 MΩ/RH, with faster response and recovery time than bare ZnO, enabling high robustness and sensing performance. These findings demonstrate an enhanced-sensing performance with ZnO/GQDs nanocomposite from cost-effective resources, providing a promising avenue for the development of on-chip humidity sensors with fast response, and repeatability over a wide range of humidity levels.