The Complex And Interesting Optical Properties

1923 Words Aug 6th, 2015 8 Pages
1. Introduction

The complex and interesting optical properties can be shown clearly on Nanostructured metals the collective oscillations of the conduction electrons termed plasmons lead to most striking phenomenon encountered in these structures are resonances . Plasmon modes exist in a number of geometries and in various metals — most importantly in noble metals such as gold, copper and silver. Under certain circumstances plasmons are excited by light, which leads to strong light scattering and absorption and an enhancement of the local electromagnetic field. In 1989, based upon calculations, Neeves and Birnboim proposed that a composite spherical particle with a dielectric core and a metallic shell could produce SPR modes with a much larger range of wavelengths. The first nanoshells were made by Zhou et al. In the 1990’s. They used a Au2S core surrounded by a gold shell. Variations of these shells made it possible to shift the standard gold colloid plasmon resonance peak from ~520 nm up to ~900 nm. There was a limit however, of less than 40 nm on the size of nanoshell that they could achieve due to the chemistry of their synthesis reactions. The process also produced large amounts of gold colloid as a secondary product which gave an additional absorption peak at ~520 nm. Halas and coworkers synthesized a new type of gold nanoshell that overcame many of the limitations of the Au2S core type nanoshell. The new method replaced the Au2S core with a silica core and made it…
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