Synthesis of Ag-coated polystyrene colloids by an improved surface seeding and shell growth technique

In this paper, an improved surface seeding and shell growth technique was developed to prepare Ag-polystyrene core shell composite. Polyethyleneimine (PEI) could act as the linker between Ag ions (Ag nanoparticles) and polystyrene (PS) colloids and the reducing agent in the formation of Ag nanoparticles. Due to the multi-functional characteristic of PEI, Ag seeds formed in-situ and were immobilized on the surface of PEI-modified PS colloids and no free Ag clusters coexist with the Ag “seeding” PS colloids in the system. Then, the additional agents could be added into the resulting dispersions straightly to produce a thick Ag nanoshell. The Ag nanoshell with controllable thickness was formed on the surface of PS by the “one-pot” surface seeding and shell growth method. The Ag-coverage increased gradually with the increasing of mass ratio of AgNO₃/PS. The optical properties of the Ag-PS colloids could be tailored by changing the coverage of Ag.