Abstract

In this paper, a colloidal-quantum-dot-based flexible gas sensor capable of detecting nitrogen dioxide with fast response and recovery at room temperature was demonstrated, owning to its small particle size, room temperature processing and ligand adjustable surface activity. Lead sulfide (PbS) colloidal quantum dots (CQDs) was first synthesized using the well-established colloid chemistry method. The sensor was fabricated simply but very effectively via spin coating of the CQDs onto alumina, polyester and paper substrates patterned with interdigitated Au ohmic electrodes under ambient atmosphere. The original oleic acid cladding on the surface of CQDs was washed with the methanol solution of sodium nitrite. Field emission scanning electron microscopy and atomic force microscopy characterization of the film morphology revealed some small cracks presented in the film, facilitating the penetration of gas molecules. At room temperature, the flexible CQD sensors showed sensitivity, response time and recovery time of sensor are 3.44, 5 s and 131 s, respectively, towards 5ppm NO₂. It also exhibited high selectivity and reproducibility towards NO₂ among the gas tested (NO₂, SO₂, NH₃ and H₂S). The flexible NO₂ sensors were further investigated under various bending curvature or subjected to intensive mechanical bending (up to 5000 times) and showed no minus degradation. Room temperature detection, high sensitivity, full recovery, good selectivity, and outstanding reliability and robustness make our PbS CQD gas sensors very competitive for many NO₂ detection applications.

© 2013 Optical Society of America