Abstract: Sandwich-like PbS nanocrystals(NCs)/rGO composites were prepared by one-step solution method.The crystal structure and surface morphology of the samples were characterized by X-ray diffraction and Field emission scanning electron microscopy.The gas sensor was fabricated with external heating to test its gas properties.The results show that PbS NCs are decorated uniformly on the rGO sheet with a 3-D sandwich-like structure in the composites.The composite has good gas sensing properties to NH3 at room temperature.PbS NCs/rGO composites possess a quite good gas response towards ammonia gas, the response of 1000 ppm NH3 is 3.45, which is obviously enhanced compared with pure PbS NCs and rGO.The composite has the detection limit of 1 ppm to NH3 gas with a good selectivity.The gas sensing mechanism shows the rGO in the composite acts as a carrier transport layer while the 3-D structure increases the gas diffusion rate and adsorption area.The composite is expected to be widely used in NH3 detection at room temperature due to its special structure and excellent gas sensing performance.

Key words: Sandwich-like PbS nanocrystals(NCs)/rGO composites were prepared by one-step solution method.The crystal structure and surface morphology of the samples were characterized by X-ray diffraction and Field emission scanning electron microscopy.The gas sensor was fabricated with external heating to test its gas properties.The results show that PbS NCs are decorated uniformly on the rGO sheet with a 3-D sandwich-like structure in the composites.The composite has good gas sensing properties to NH3 at room temperature.PbS NCs/rGO composites possess a quite good gas response towards ammonia gas, the response of 1000 ppm NH3 is 3.45, which is obviously enhanced compared with pure PbS NCs and rGO.The composite has the detection limit of 1 ppm to NH3 gas with a good selectivity.The gas sensing mechanism shows the rGO in the composite acts as a carrier transport layer while the 3-D structure increases the gas diffusion rate and adsorption area.The composite is expected to be widely used in NH3 detection at room temperature due to its special structure and excellent gas sensing performance.