Preparation And Luminescent Properties Of Metal Sulfides Nanocrystals Micro Structure

Semiconductor nanocrystals (NCs) have attracted considerable attention due to the unique optical and electrical properties. They exhibit high fluorescence quantum efficiency, high light stability and superior mobility, which have wide application prospects in lighting, display, solar cells, and detectors, etc. In this paper, CdS and EuxS NCs were synthesized by employing stearate, sulfur, octadecylamine and other "green" chemical composition as precursors. EuxS/ZnS, Er2S3/ZnS, PbS/ZnS, PbS/CdS core/shell NCs were synthesized via hot solution phase chemistry using a nucleation-doping strategy. In addition, the luminescence properties of nanocrystals are concerned and discussed, The detailed contents are as follows:1. CdS NCs with different reaction time were synthesized by thermal decomposition method at two different temperatures. The intensity of the trap emission gradually decreases as the reaction time increases in contrast with that of the band-edge emission, which is explained by LaMer model. The synthesis of CdS NCs at lower temperature produced white light emission under UV excitation mainly due to the smaller particle size; CdS NCs with larger particle size prepared in the higher temperature have a broad emission across500-700nm under the excitation of blue light with460nm, consequently, mixing with the remaining blue light to produce white light. Furthermore, white light-emitting devices used CdS NCs as the intrinsic emitting layer was investigated.2. EuxS NCs were synthesized by thermal decomposition and the luminescence properties of NCs at different times were discussed. All of EuxS NCs emit white light. EuxS/ZnS core/shell NCs were synthesized by a nucleation-doping strategy. Moreover, emission intensity of EuxS/ZnS NCs has been significantly improved compared to that of EuxS NCs. Er2S3/ZnS NCs was synthesized by a nucleation-doping strategy. The emission intensity of Er3+strongly increases with increasing overcoating temperature, which was interpreted by the enhancing diffusion of Er3+ions. Besides, IR-LEDs were fabricated combining commercial red GaAs LEDs.3. PbS/ZnS and PbS/CdS core/shell NCs with different precursor molar of Pb/S were synthesized by a nucleation-doping strategy. In larger the proportion of Pb, the PbS/CdS NCs show excellent near-infrared light-emitting properties, their absorption and emission have a blue shift with increase reaction time, which is due to cation diffusion and exchange in the reaction process, and the alloying is formed at core/shell boundary. In the proportion of Pb is very small, PbS/CdS NCs showing unique visible light-emitting properties, to achieve white light emission.In addition, the spectra of PbS/ZnS NCs also exhibited blue shift.