溶剂热再结晶合成由纳米颗粒自组装成的一维CdS纳米棒

Solvothermal recrystallized synthesis of one-dimensional CdS nanorods self-assembled from nanoparticles

采用两种不同的溶剂热路径合成出了不同形貌和尺寸的CdS纳米晶,一种是以无水乙二胺(en)为溶剂,CdCl_2·2.5H_2O和硫脲(H_2NCSH_2N)为镉源和硫源,在不同反应温度(160℃—220℃下制备出了CdS纳米晶,讨论温度对CdS纳米晶生长的影响;另一种是以en为溶剂,将在160℃下合成的产物在200℃下原位再结晶生长2—8 h,分析原位生长时间对CdS纳米晶生长的影响.通过X射线衍射(XRD)、扫描电子电镜(SEM)和透射电子电镜(TEM)等表征产物的物相、形貌和微结构,分析可知:两种路线合成的产物均为六方相CdS;当温度为160℃时,产物形貌为纳米颗粒状,当温度高于160℃时,产物为CdS纳米棒状;同时,在200℃下原位再结晶生长不同时间后发现产物形貌由纳米颗粒转变为纳米棒,通过场发射扫描电镜(HRTEM)分析可知:纳米棒是由零维纳米颗粒自组装而成.最后,讨论了影响产物CdS纳米晶形貌转变的因素和纳米棒的生长机理.

Two different solvothermal synthesis routines are used to fabricate CdS nanocrystals with different morphologies and sizes. Anhydrous ethylenediamine （en） is chosen as solvent, CdCI2. 2.5H20 and thiourea （H2NCSH2N） as the cadmium source and sulfur source respectively in the first method. CdS Nanocrystals are prepared at different reaction temperatures （160 °C-220 °C） and the influence of the reaction temperature on the growth of CdS nanocrystals is discussed. In the other routine, anhydrous ethylenediamine （en） is also chosen as solvent. The synthesized products at 160 °C are recrystallized under 200 °C for 2-8 h. The influence of the recrystallisation time on the growth of CdS Nanocrystal is discussed. The in-situ analysis of effect of the growth time on the growth of CdS nanocrystals is performed. The phase, morphology and crystallographic structure of CdS nanocrystals are investigated by Xray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） respectively. The results show that both products exhibit pure hexagonal structures, the morphology of the product is nanoparticles at the temperatures below 160 °C, when the temperature is rasied to higher than 160 °C, the products are CdS nanorods. Meanwhile, the morphologies of the recrystallisation products under 200 °C for different times are found to convert from nanoparticles into nanorods gradually. The nanorods are composed of zero-dimensional particles through self-assembly process which could be demonstrated by field emission scanning electron microscopy （HRTEM） analysis. Finally, the factors that influence the morphology changes of CdS nanocrystals and the mechanism of the growth of nanorods are discussed.