Synthesis, Coating And Catalytic Property Of Gold Nanoparticles

Noble metal nanoparticles(NPs) with the superior performance have become a research hotspot in the last two decade. In particular, gold(Au) NPs have been most extensively studied with a big variety of applications, such as sensing, biomedicine, catalysis, etc. In our work, we synthesized Au, Au@Si O2, Au@C, Janus Au-Si O2 and Janus Au-Ag NPs, and investigated the morphology, optical and catalytic properties and stability of the products.Water-soluble Au NPs were synthesized using seed growth method and fully coated with Si O2 and carbon, respectively using improved-St?ber and hydrothermal synthesis methods. The catalytic properties of Au@Si O2 and Au@C NPs with the same shell thickness and gold concentration were investigated. Moreover, Au@C NPs with different shell thickness were synthesized to study the influence of the carbon shell on catalytic property. The results show that Au@Si O2 NPs have superior catalytic properties over Au@C. The underlying reason was attributed to different pore size of C and Si O2 shell. Using SF method, it is shown that the pore size of carbon nanospheres is about only about one-third as that of Si O2.Janus Au-Si O2 NPs are synthesized with Si O2 coated on one hemisphere of Au NPs which were pre-modified by two different molecules(4-MPAA and PAA, respectively). Besides the morphology, the catalytic properties of the Janus NPs were explored. It is found that the catalytic capability of the Janus NPs is slightly higher than that of the same Au NPs fully covered by Si O2. After post-treatment under ultraviolet irradiation and washing in ethanol, the catalytic properties of the Janus NPs can be largely improved. Furthermore, the Janus NPs were collected after the reaction. Their morphology as well as the optical and catalytic results reveals the excellent recyclability and stability of the post-treated Janus Au-Si O2 NPs.In addition, we synthesized Au NPs with one weakly coated hemisphere and one strong-bonded coating side. Based on such NPs, Janus Au-Ag NPs were synthesized through deposition of Ag on the gold nucleation cites. The catalytic and optical properties of the resultant Janus Au-Ag NPs were studied. The UV-vis results show a specific absorption peak attributed by SPR of Au-Ag Janus morphology besides the peaks corresponding to monometallic Au and Ag NPs. The catalytic property of Au-Ag Janus nanoparticles was examined as comparison to Au nanoparticles. The results demonstrate that the catalytic property of the Janus NPs is remarkably improved compared with that of Au NPs. However, the stability of the Janus NPs in the catalytic reaction is not preferred. Si O2-coated Au-Ag Janus nanoparticles may be performed in the future work upon this issue.