Morphology-Controlled Synthesis of Hybrid Nanocrystals via a Selenium-Mediated Strategy with Ligand Shielding Effect: The Case of Dual Plasmonic Au-Cu_2-xSe.

Abstract

Integrating a plasmonic metal and a semiconductor at the nanoscale is of great importance for exploring their optical coupling properties. However, the synthesis and fine structural control of such nanostructures remain challenging. Herein we report the facile aqueous-phase Se-mediated overgrowth of metal selenides onto Au nanocrystals. Taking plasmonic Cu_2-xSe as an example, the introduction of a Se template allows deposition of large Cu_2-xSe crystalline grains onto Au nanocrystal seeds in various shapes, including spheres, rods, and plates. Moreover, the configuration of Au-Cu_2-xSe hybrids can be tuned from core-shell to heterodimer structure by controlling the growth behavior of the Se template. Se overgrowth depends critically on the absorption strength of stabilizers on Au seeds: a strongly absorbing stabilizer inhibits isotropic overgrowth, which is in agreement with molecular dynamics simulations. The resultant Au-Cu_2-xSe hybrid nanocrystals possess multiple surface plasmon resonance modes. Finally, our synthetic strategy can be extended to prepare other Au-metal selenide hybrids such as Au-Ag₂Se and Au-CdSe with controllable morphologies.