Hongpo Liu

Controlled Synthesis of Octahedral Platinum-Based Mesocrystals by Oriented Aggregation

Designed synthesis of noble metal mesocrystals is of great significance for a variety of applications. Here, the synthesis of octahedral Pt-Ag alloy mesocrystals with precisely controlled morphology, size, and exposing facets, formed by oriented aggregation of their crystallites, is reported. The critical role of bromide was revealed in regulating the overall octahedral morphology of the Pt-Ag mesocrystals, by bridging the interactions between the capping agent and the Ag-modified Pt crystallites. The size of the mesocrystals was precisely controlled in a broad range by tuning the number of the seeds, all retaining their octahedral morphology. Based on this understanding, octahedral Pt-Ag mesocrystals exposing {1 1 1} facets have been obtained in a highly controllable and reproducible manner. This material showed excellent electrocatalytic activity and stability in oxygen reduction reactions (ORR). It is hoped that the current synthesis provides new insights that pave the way to diverse faceted nanocrystals/mesocrystals for high-performance catalytic and many other applications.

Solid to Hollow Conversion of Silver Nanocrystals by Surface-Protected Etching

Although hollow silver nanocrystals possess unique plasmonic properties, there is a lack of robust strategies to synthesize such nanocrystals with high efficiency and controllability. To solve this problem, a new surface-protected etching strategy to convert solid Ag nanocrystals, which are widely available from conventional syntheses, into their hollow counterparts, producing a family of hollow Ag nanocrystals is reported. Hollow Ag nanospheres and nanotubes were prepared conveniently in this way. The key was the surface modification of Ag nanocrystals by a minor amount of Pt prior to a controllable etching process, which accounts for enhanced stability of the Ag surface and subsequent etching of Ag from the inner part of the nanocrystals while retaining the overall crystal morphology. These hollow Ag nanocrystals showed distinctive optical properties, as demonstrated by the enhanced optical transmittance of flexible electrodes fabricated with Ag nanotubes, compared to nanowires. These hollow Ag nanocrystals hold promise in different plasmonic and electronic applications.