Chemical Deposition and Stabilization of Plasmonic Copper Nanoparticle Films on Transparent Substrates

Preparation of supported copper nanostructures has been scarce, compared to the more noble metals Ag and Au, mainly due to the lower stability of Cu toward corrosion in aqueous solutions and oxidation in air, either during or after preparation. Still, as a markedly inexpensive metal, Cu might present an attractive substance, if suitable Cu nanoparticle (NP) deposition and stabilization methods could be developed. Here, we present the first case of glass substrates coated with Cu or Cu2O NPs using wet chemical deposition (CD), performed under well-defined conditions optimized for obtaining each of the two nanoparticulate deposits. Cu NP films were also obtained by chemical reduction of the Cu2O NP films, thereby achieving improved size uniformity. The Cu NP films display a prominent surface plasmon (SP) band in the visible range. The dependence of the SP absorbance on the local dielectric environment is shown to provide a useful tool for monitoring Cu NP corrosion processes and their inhibition. Stabilization of the Cu NP films by treatment with the corrosion inhibitor benzotriazole (BTAH), shown here for the first time, enabled study of the films' plasmonic properties, such as their refractive index sensitivity (RIS), a basic property in sensing applications. The measured RIS values are similar to those of typical gold NP films. Introduction of an effective, low-cost, and scalable method for the preparation of stable supported Cu and Cu2O NP films may open the way to a variety of plasmonic and other applications.