Optical Humidity Sensor Based on CdSe/ZnS Quantum Dots Modified by Porous Silica

Ultra-sensitive optical humidity sensors based on nanomaterials play important roles in the fields of science and industry. The related research has been reported, however, the underlying physical mechanism is still unclear. In order to clarify this point, and further improve the sensing performance, herein, optical humidity sensor based on porous silica/quantum dots (PS/QDs) hybrid nanoarchitecture has been developed. PS is selected to enhance emission of QDs due to its large surface roughness, which can improve light utilization. Under optimized conditions, the emission from the hybrid PS/QDs can be enhanced 6.5 times compared with the as-grown QDs. With the increase of relative humidity from 20% to 80%, the hybrid PS/QDs demonstrate excellent response, wide sensing range, fast response time (22-40 s), good selectivity, and repeatability. Based on laser spectroscopy, the sensing mechanism is ascribed to the passivation of the surface defects by water molecules, which results in enhanced emission. This work provides a simple and low-cost method to fabricate humidity sensors and shows promising applications in environmental detection.