Colloidal nanoparticle materials have attracted great interest due to their unique physicochemical properties and broad application prospects. Among them, plasmonic metal-based hybrid nanoparticles especially plasmonic metal-semiconductor core?shell or heterostructure hybrids are receiving extensive attention due to enhanced or even unconventional optical and electric properties arising from the interactions between their constituents. Despite tremendous progress achieved so far on the synthesis of plasmonic metal-semiconductor hybrid nanoparticles in organic solvents, aqueous synthesis methods are still urgently required as the localized surface plasmon resonances (LSPRs) of noble metals such as Au are highly shape dependent, and the anisotropic Au nanorods or nanoplates can be synthesized only in aqueous phase.

Recently, a team of researchers, led by Prof. JIANG Jiang at Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences (CAS) proposed a facile aqueous-phase Se-mediated overgrowth of a plasmonic semiconductor Cu_2-xSe on Au nanocrystals to fabricate Au-Cu_2-xSe hybrid nanoparticles. The synthesis involved first growing an intermediate Se shell on Au seeds, irrespective of Au morphology and facets (0-2D Au nanocrystals in shapes such as dots, rods, and plates can all be used as seeds), and subsequently converting it to Cu_2-xSe in the presence of various stabilizers at room temperature (30 ^oC) in the aqueous phase. Moreover, they found the stabilizers influenced the growth mode of Se templates due to their different adherence to the Au surface, as well as the subsequent transformation process as a result of stabilizer-Cu_2-xSe interaction. Consequently, the morphology of Au-Cu_2-xSe hybrids could be tuned from core-shell to heterodimer with varied stabilizers.

This Se-mediated process for metal-metal selenide synthesis represents an exciting addition to the rapidly expanding library of chemical reactions that produce hybrid nanoparticles. Following this strategy, structurally controlled Au-Ag₂Se hybrids can be also synthesized. Further, the resulting Au-Cu_2-xSe hybrids can be transformed to Au-CdSe hybrids with excellent morphology retention by cation-exchange reaction. The successful deposition of various metal selenides onto plasmonic Au nanocrystals with arbitrary morphologies lays the foundation for future study on their plasmon-exciton interactions and plasmonic coupling effects.

The elemental analyses of hybrid nanoparticles in this work were supported by Yang Xianfeng from South China University of Technology. This work was funded by the Ministry of Science and Technology (No. 2016YFA0200700) and Natural Science Foundation of China (No. 21473243).