Fabrication of Core-Shell Structure of M@C (M = Se, Au, Ag2Se) and Transformation to Yolk-Shell Structure by Electron Beam Irradiation or Vacuum Annealing

Selenium Cc carbon core-shell spheres have been synthesized via a simple one-step hydrothermal carbonization process using sucrose and sodium selenite as precursors. Metal selenide or noble metal, e.g. Ag2Se or Au, can be easily encapsulated into the carbon shell by using the as-prepared Se@C core-shell samples as site templates, The transformation from core/shell to yolk/shell structure, e.g, Se@C, Au/Se@C and Ag2Se@C, can be achieved through thermal evaporation under electron beam irradiation or vacuum annealing to evaporate Se. The optical absorption of the samples can be tuned by varying the structure/compositions of the samples.