Directed Calcium Chloride Coalescence Method for Preparation of Silver Nanocubes

Abstract

Controlling the size, shape, and structure of metal nanoparticles is very important because of the strong correlation between these parameters and their resulting optical, electrical, and catalytic properties. This paper describes a directed calcium chloride coalescence method, based upon incubating a silver colloid with an aqueous solution of CaCl₂, for preparation of silver nanocubes with a particle size of 270 to 950 nm. The method avoids the use of nonvolatile surfactants and polymers, which may be adsorbed onto the silver nanocubes and interfere with their possible applications in catalysis and analytical devices based on surface-enhanced Raman scattering (SERS) spectroscopy. The nanocubes show good SERS activity in the presence of adsorbed 4-mercaptobenzoic acid (4-MBA) with excitation at 632.8 nm, and the enhancement factor reaches ∼7 × 10⁵. The nanocubes are produced in a simple and cost-effective way, and they are expected to play an important role in the development of SERS-based analytical devices. The method may represent a novel route for preparation of metal nanocubes, which is a subject of intense interest.