Heterodimer nanostructures induced energy focusing on metal film

TL;DR

This study investigates how size differences in heterodimer nanoparticles on metal films influence electromagnetic field focusing, revealing enhanced light concentration that benefits applications like SERS and solar energy conversion.

Contribution

It provides the first detailed analysis of size-induced electromagnetic redistribution in heterodimer nanoparticle systems on metal films, combining theoretical and experimental approaches.

Findings

Smaller nanoparticles focus more light energy on the film, up to 5 times more than larger ones.

The energy focusing depends on wavelength and size ratio of the nanoparticles.

Experimental SERS spectra confirm the theoretical predictions.

Abstract

As an interesting surface plasmon phenomenon discovered several years ago, electromagnetic field redistribution in nanoparticle dimer on film system provides a novel thought to enhance the light power on a plain film which could been widely used in surface enhanced Raman scattering (SERS), solar cells, photo-catalysis, etc. Homodimers on film are mainly investigated in past years, while the properties of heterodimers on film are still unclear. In this work, size difference induced electromagnetic field redistribution in Ag nanoparticle dimer on Au film system is investigated first. The results obtained from finite element method indicate that the smaller nanoparticle has much greater ability to focus light energy on Au film, which even reached more than 5 time compared to the larger one. Further researches indicate that this energy focusing ability has a strong relationship to the wavelength and diameter ration in dimer. Similar focusing phenomenon is found in the system of thick wire-smaller particle on film. Later, the SERS spectra collected in the small nanoparticle-large nanowire system provide an experimental evidence for this theoretic predication. Our results strengthen the understanding of surface plasmon on plane film and have potential application prospects in the surface plasmon related fields.