Water Phase Synthesis And Properties Research Of Au@Semiconductor Core/Shell Nanocrystals

In this paper, the hybrid noble metal@semiconductor core-shell nanocrystals synthesized by methods of non-expitaxial growth as well as cation exchange were studied. Moreover research on efficient photocatalytic evolution and photothermal performance had been done. The main contents and results of the present study are as follows:1. We have synthesized the Au@CdS core-shell nanocrystals with different shell thickness by cation exchange method in water phase, and the single crystal CdS shell and noble metal Au core in three-dimensional direction have clear direct contact interface. Because of the existence of plasmon Au nuclear, under the excitation of incident light, Au@CdS produced LSPR enhance efficient photon-generated electron/hole separation and electronic injection effect. Then we studied the water splitting performance of different samples, comparing to the pure CdS5 nm quantum dots, Au35nm@CdS5nm core-shell nanocrystals synthesised in the water phase has enhanced H2 evolution activity that manifested a dramatic enhancement of 240 times,up to 24mmol·h-1·g-1. And its apparent quantum yield reaches as high as 45%. Then we loaded noble metal Au and Pt on the Au@CdS core-shell nanocrystal shell surface by Photo-Deposition Method and obtained Au@CdS/Au, Au@CdS/Pt composite nanocrystals. Because noble metal Au and Pt can act as cocatalyst to capture and collect transitive electronic, hydrogen production efficiency was enhanced to 33mmol·h-1·g-1and 69 mmol·h-1·g-1, is 1.4 times and 2.9 times of Au35nm@CdS5nm. On the basis of the result of the experiment we carried on the finite difference time domain method（FDTD） to simulate the plasmon the distribution of near field and field intensity of different sizes of core-shell nanostructures in aqueous environment. And based on this, we bring up the theory of surface plasmon resonance enhanced hot electron injection theory to study the hydrogen production mechanism of Au@CdS core-shell nanocrystals.2. For the first time, we synthesized Au@Ag₃AuTe₂ core-shell nanocrystals structure, and analysised the crystal structure and composition of Au@Ag₃AuTe₂core-shell nanostructure through transmission electron microscope, x-ray energy spectra, x-ray powder diffraction et al method. At the same time, we study its effect on morphology and crystallinity of the products by adjusting the reaction temperature,reaction time, Te precursor addtion. The synthesis of Au@Ag3AuSe2 proved the universality of the synthetic method. Because the existence of plasmon Au nuclear makes Au@Ag₃AuTe₂ and Au@Ag3AuSe2 has unique optical properties, they has continuous and strong absorption in the near-infrared light area of the 700 nm to1200nm. Then we test the photo-thermal performance of Au@Ag₃AuTe₂ and Au@Ag3AuSe2 under 808 nm and 1064 nm laser, the photo-thermal conversion efficiency of Au@Ag₃AuTe₂ nanocrystals（200 ppm） can be up to 76.7% at 808 nm and 49.6% at 1064 nm respectively, the photo-thermal conversion efficiency of Au@Ag3AuSe2 nanocrystals（200 ppm） can be up to 50.7% at 808 nm and 34.1% at1064 nm respectively.