Two-dimensional assembled PVP-modified silver nanoprisms guided by butanol for surface-enhanced Raman scattering-based invisible printing platforms

Abstract

This study proposes a methodology for the fabrication of two-dimensional assembled colloidal nanocrystals based on the classical theory for the surface excess of a short-chain alcohol (butanol) in an aqueous mixture and Rayleigh–Bénard–Marangoni convection caused by temperature and/or surface tension gradients due to the volatilization of butanol at the air–water interface. When polyvinylpyrrolidone (PVP)-modified anisotropic silver nanoprisms dispersed in butanol were added into the water phase, the nanoprisms were guided to the air–water interface via adsorbed butanol together with free butanol and formed dense two-dimensional assemblies through the lateral attraction between nanoprisms as the adsorbed butanol was volatilized. The obtained dense film composed of silver nanoprisms exhibited surface-enhanced Raman scattering (SERS) activity, and in particular, the activity was largely enhanced by low-pressure plasma treatment. A SERS-based invisible printing platform that could only be recognized by x–y SERS mapping was demonstrated with the patterned nanoprism films.