Self-assembled large Au nanoparticle arrays with regular hot spots for SERS

Small. 2011 Aug 22;7(16):2365-71. doi: 10.1002/smll.201100686. Epub 2011 Jun 1.

Abstract

The cost-effective self-assembly of 80 nm Au nanoparticles (NPs) into large-domain, hexagonally close-packed arrays for high-sensitivity and high-fidelity surface-enhanced Raman spectroscopy (SERS) is demonstrated. These arrays exhibit specific optical resonances due to strong interparticle coupling, which are well reproduced by finite-difference time-domain (FDTD) simulations. The gaps between NPs form a regular lattice of hot spots that enable a large amplification of both photoluminescence and Raman signals. At smaller wavelengths the hot spots are extended away from the minimum-gap positions, which allows SERS of larger analytes that do not fit into small gaps. Using CdSe quantum dots (QDs) a 3-5 times larger photoluminescence enhancement than previously reported is experimentally demonstrated and an unambiguous estimate of the electromagnetic SERS enhancement factor of ≈10(4) is obtained by direct scanning electron microscopy imaging of QDs responsible for the Raman signal. Much stronger enhancement of ≈10(8) is obtained at larger wavelengths for benzenethiol molecules penetrating the NP gaps.

Keywords: Raman spectroscopy; gold nanoparticles; photoluminescence; quantum dots; self-assembly.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.