Macroscopic deformation of a substrate as a new method for controlling geometry and plasmon-resonant properties of highly ordered planar ensembles of metal nanoparticles

Abstract

A new approach to creating highly ordered two-dimensional ensembles of nanoparticles with variable geometric parameters is proposed. It combines diblock copolymer micellar lithography and controlled deformation of a polymer substrate. The key feature of the approach is the formation of a monolayer of hexagonally packed metal precursor-containing micelles of an amphiphilic diblock copolymer on the surface of an isotropically stretched polymer plate. The average distance between micelle centers is 140 nm. Subsequent thermal treatment (or isotropic stretching) of the sample results in the shrinkage (or elongation) of the substrate, which enables one to vary the distance between micelle centers in a range of 80–200 nm while retaining hexagonal packing of the micelles in the monolayer. At the final stage, ensembles of hexagonally ordered gold nanoparticles are obtained by exposing the micellar films to air plasma. It is demonstrated that gold nanoparticles in these ensembles can be enlarged by seeded growth. The systematic study of the plasmon-resonant properties of the resulting ensembles shows that the gradual increase in the distance between 35-nm gold particles from 80 to 200 nm leads to an unexpected nonmonotonic shift of the maximum of localized surface plasmon resonance, which is, from our point of view, caused by the high degree of organization of nanoparticles on the substrate.