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

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 (NO 2 ) 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 NO 2 adsorption and charge transfer. This study highlights the importance of surface ligand engineering in the development of practical CQD gas sensors.