Preparation Of Novel Gold-platinum Heterostructures Via Selective Etching

Gold nanoparticles have shown promising potential in many fields, such as optical detection, biological imaging, photothermal therapy, and so on, due to their unique optical properties. The unique optical property can be adjusted by changing the structure, size and component of nanoparticles. Formation of heterostructure is an effective way to change the original structure by introducing foreign elements. Heterostructures not only collect the performance of a single material, but also produce unique properties after different materials efficiently assembled. Here, we obtained some novel gold-based hetero-nanostructures via selective etching. UV-vis absorption spectroscopy was used to track the reaction process and various characterization methods were conducted to identify the composition and structure of products. Reasonable reaction mechanism was also proposed and testified. The main results and progresses are summarized as follows:1. Dumbbell-like PtAu-Au nanorods were obtained by the lateral etching of gold nanorods by K2PtCl4, under the control of silver ion. By a series of well-designed control experiments, the reaction mechanism of the corrosion reaction was explored. Redox reaction between K2PtCl4 and gold occurred on the tips of gold nanorods at the beginning, due to the higher activity and less surface passivation of cetyltrimethylammonium bromide (CTAB). Meanwhile, the reduced Pt0 atoms could in-situ deposit on the end. The Pt shell protected the etched edges from further etching, changing the etching route and causing the unprotected Au on side facets to be etched. The present of silver ions can cause an increase amount of CTAB on the side of gold nanorods, inhibiting the deposition of Pt0 atoms. So the side of gold nanorods could be continually etched, leading to the reduction in effective radius. The dumbbell-like PtAu-Au nanorods exhibit a higher catalytic activity than that of Au nanorods and Au@PtAu core-shell nanorods in the reduction of p-nitrophenol at room temperature. The electronic effect and the unique structure in the dumbbell-like PtAu-Au nanorods can account for this result.2. The preparation of Au@PtAuAg hetero-nanoparticles was started from Au nanospheres, followed by further reactions with AgNO3, HAuCl4, K2PtCl4 and ascorbic acid (AA). And the whole process of the reaction was preliminarily explored by a series of well-designed control experiments. Because of the higher electrode potential of Au(Ⅲ)/Au and Ag(Ⅰ)/Ag, AuAg can be reduced by ascorbic acid preferentially, producing octahedron-like Au@AuAg nanoparticles. And then Pt (Ⅱ) was reduced to Pt0, depositing on the vertices of the as-obtained octahedron. The unprotected Au on side facets was etched by HAuCl4, resulting in the hetero-structure of Au@PtAuAg. This Au@PtAuAg hetero-nanoparticles have a potential application in catalysis, due to the superior catalytic performance of Pt.