Twinned nanoparticle structures for surface enhanced Raman scattering

Abstract

This work dealt with the preparation of twinned nanostructures for the optimization of substrates for SERS. At first GaP nanocones with hexagonal bases were prepared on GaP substrates by metal organic vapour phase epitaxy (MOVPE) at 650 °C. The substrates were then covered with Ag nanoparticles by RF sputtering. The Ag nanoparticles had very short inter–particle distances if they formed from thin Ag layers. The nominally 5 nm thick Ag layer resulted in the formation of an Ag nanoparticle assemblage with inter–particle distances shorter than 5 nm. The GaP nanocones and Ag nanoparticles worked in synergy to yield a substantial increase of SERS signal. This was verified with Rhodamine 6G molecules (at a concentration of 10-6M) at the typical Raman lines of 611 cm−1 and 773 cm−1. The enhancement of SERS was estimated to be as high as 106 for the nanocone substrate decorated with Ag nanoparticles from a nominally 5 nm thick Ag layer.