Ppb level ammonia detection of 3-D PbS quantum dots/reduced graphene oxide nanococoons at room temperature and Schottky barrier modulated behavior

Abstract

The development of novel sensing materials is the key issue for the effective detection of ammonia gas at room temperature. In the present work, the novel 3-D cocoon-like architectures of PbS quantum dots (QDs)/reduced graphene oxide (rGO) composites are self-assembled by using one-step liquid phase method, and the formation process may be vividly depicted by the natural formation process of the ‘silk cocoons’. 3-D PbS QDs/rGO nanococoons show a good detection limit of 750 ppb towards ammonia gas at room temperature, which is significantly enhanced compared with those of pure PbS QDs and rGO. Meanwhile, the gas sensing response will be greatly decreased with the increasing of the working temperature and there is no response at 150 °C, resulting from Schottky barrier modulation. The abnormal dependence of the gas response on the working temperature may be a unique fingerprint calibration for the ammonia detection. In addition, 3-D PbS QDs/rGO nanococoons have a relatively good selectivity towards ammonia gas at room temperature compared with ethanol, acetone and so on, and the long term test proves that they possess an excellent sensing stability. The sensing enhancement at room temperature may be due to the 3-D special architecture and well-combined interfaces of 3-D PbS QDs/rGO nanococoons, which may favor for the absorption of the gas molecules and the fast charge transport from PbS QDs to rGO, respectively.