Highly sensitive humidity sensors based on Li-C3N4 composites on porous graphene flexible electrodes

This study aimed to develop highly-sensitive and flexible humidity sensors based on graphitic carbon nitride doped lithium chloride to form sheet-like Li-C3N4 on porous graphene electrodes. Using a large specific surface area as sensing composites, the synthesized Li-C3N4 composites could greatly improve the sensitivity of humidity sensors. The porous graphene was induced on the polyimide film using an ultraviolet laser combined with farinfrared irradiation as a flexible electrode. The Li-C3N4 sensing composites drop-cast on the porous graphene surface formed the Li-C3N4/graphene nanosheets. Surface morphology, structure analysis, and elemental composition of Li-C3N4 and porous graphene were analyzed. Li-C3N4-based humidity sensors showed an outstanding sensing performance in a wide measuring range of 11-97% relative humidity (RH), with small humidity hysteresis (RH of 2.4%), rapid response and short recovery times (4.1 s and 18.7 s, respectively), high response (99.68%), and response stability. Based on the Li-C3N4 humidity sensor with a high sensitivity, the proposed flexible sensors were applied for human breath sensing, skin humidity sensing, and non-contact sensing of a fingertip.

Automated summary

This study developed highly-sensitive and flexible humidity sensors based on graphitic carbon nitride doped lithium chloride. The sensors showed outstanding sensing performance with small humidity hysteresis, rapid response and recovery times, high response, and response stability. The proposed sensors were successfully applied for human breath sensing, skin humidity sensing, and non-contact sensing of a fingertip.