The 'lightning' gold nanorods: fluorescence enhancement of over a million compared to the gold metal

Gold nanorods capped with micelles and having an aspect ratio of 2.0-5.4 ar e found to fluoresce with a quantum yield which is over a million times tha t of the metal. For rods of the same width, the yield is found to increase quadratically while the wavelength maximum increases linearly with the leng th. We assign this emission to the electron and hole interband recombinatio n. The increase in the emission yield results from the enhancement effect o f the incoming and outgoing electric fields via coupling to the surface pla smon resonance in the rods. This is similar to the previously proposed fluo rescence and the Raman enhancement on noble metal rough surfaces. (C) 2000 Published by Elsevier Science B.V. All rights reserved.