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

Two different solvothermal synthesis routines are used to fabricate CdS nanocrystals with different morphologies and sizes. Anhydrous ethylenediamine (en) is chosen as solvent, CdCl2. 2.5H2O and thiourea (H2NCSH2N) as the cadmium source and sulfur source respectively in the first method. CdS Nanocrystals are prepared at different reaction temperatures (160 ℃-220 ℃) 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 ℃ are recrystallized under 200 ℃ 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 X-ray 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 ℃, when the temperature is rasied to higher than 160 ℃, the products are CdS nanorods. Meanwhile, the morphologies of the recrystallisation products under 200 ℃ 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.