The role of oxygen in plasmon-driven transformation of silver nanoparticles

Abstract

Plasmon-driven transformation (PDTr) of silver nanoparticles is a very valuable tool for formation of various anisotropic silver nanostructures. PDTr involves two steps: slow surface dissolution of silver nanoparticles, and redeposition of dissolved silver by the photocatalytic reduction of Ag+ cations. Photocatalytic reduction of Ag+ occurs preferentially at such places of silver nanostructures, at which strong surface plasmons are excited (usually sharp edges, tips). Therefore, during PDTr the inhomogeneity of nanoparticles may increase. Up to now all synthesis of Ag nanoparticles utilizing PDTr have been carried out in the solution containing dissolved oxygen. In this contribution we have shown that when another oxidising agent (e.g., 1,4-benzoquinone) is present in the reaction mixture, the PDTr of silver nanoparticles can be carried out even in the deoxidised solution. Moreover, using oxidising agents other than oxygen allows for some modification of the PDTr process (especially synthesis of smaller Ag nanostructures). Explanation of the observed phenomenon is proposed (involving complete oxidation by the dissolved oxygen of some very small Ag clusters).