Stabilization of PbS colloidal-quantum-dot gas sensors using atomic-ligand engineering

Abstract

Colloidal quantum dots (CQDs) are promising materials candidates for next-generation semiconductor gas sensors, due to their high surface activity and solution-processability. Despite the improved sensitivity demonstrated by PbS CQDs, their long-term stability remains a challenge for practical applications. In this paper, we propose a stabilization strategy for PbS CQD gas sensors by using atomic-ligand engineering. The oleic acid ligands surrounding PbS CQDs are replaced by halide ligands (Cl–, Br– and I–, respectively) via a phase-transfer ligand exchange method. The sensitivity and long-term stability of the PbS CQD gas sensor towards nitrogen dioxide (NO2) at room temperature are impressively improved. The excellent humidity stability of the iodine ligand exchanged PbS CQD gas sensor is also demonstrated. The mechanism is investigated by real-time electrical measurement, combined with operando diffuse reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis. The results indicate that the large atomic radius and high binding energy of iodide ligands enhance surface passivation and provide favorable conditions for NO2 adsorption and charge transfer. This study highlights the importance of surface ligand engineering in the development of practical CQD gas sensors.