Abstract
Surface-enhanced Raman scattering is an effective analytical method that has been intensively applied in the field of identification of organic molecules from Raman spectra at very low concentrations. The Raman signal enhancement that makes this method attractive is usually ascribed to the noble metal nanoparticle (NMNP) arrays which can extremely amplify the electromagnetic field near NMNP surface when localized surface plasmon resonance (LSPR) mode is excited. In this work, we report a simple, facile, and room-temperature method to fabricate large-scale, uniform gold nanoparticle (GNP) arrays on ITO/glass as SERS substrates using a promoted self-assembly deposition technique. The results show that the deposition density of GNPs on ITO/glass surface increases with prolonging deposition time, and nanochain-like aggregates appear for a relatively longer deposition time. It is also shown that these films with relatively higher deposition density have tremendous potential for wideband absorption in the visible range and exhibit two LSPR peaks in the extinction spectra because the electrons simultaneously oscillate along the nanochain at the transverse and the longitudinal directions. The SERS enhancement activity of these GNP arrays was determined using 10-6 M Rhodamine 6G as the Raman probe molecules. A SERS enhancement factor as large as approximately 6.76 × 106 can be obtained at 1,363 cm-1 Raman shift for the highest deposition density film due to the strong plasmon coupling effect between neighboring particles.
Highlights
Surface-enhanced Raman scattering (SERS) has been considered as a highly sensitive and convenient analytical tool to detect chemical and biological molecules [1,2,3,4,5,6,7]
SERS provides an extreme signal enhancement over traditional Raman spectrum intensity due to the effect of localized surface plasmon resonances (LSPR), which is an optical phenomenon arising from the collective oscillation of conduction electrons in a noble metallic nanostructure when the electrons are disturbed from their equilibrium positions [8,9]
To obtain tremendous SERS signal enhancement ability, numerous available approaches such as electron beam lithography (EBL) [14,15], nanoimprintation [16,17], nanosphere lithography (NSL) [18], mask-assisted deposition (MAD) [19], vacuum evaporation, and other strategies have been proposed to fabricate well-ordered or random nanostructures [20,21], which composed of uniform noble metal (Au or Ag) nanoparticles
Summary
Surface-enhanced Raman scattering (SERS) has been considered as a highly sensitive and convenient analytical tool to detect chemical and biological molecules [1,2,3,4,5,6,7]. Nanoimprintation, NSL, and MAD methods can provide large-scale uniform noble metallic structure array, but the preparation process is complicated and the gap between particles cannot be reduced to sub-10 nm. The self-assembly method is widely used to fabricate highly large-scale-ordered two-dimensional noble metal particle films (Au or Ag) consisting of metal nanoparticles such as nanosphere, nanorod, nanocube, and nanotriangular on ITO/glass or Si substrates [22,23,24,25,26]. Such selfassembly method usually require complicated preparation processes and special substrate surface modifications. Exploring a new simple method that directly assembles large-scale NMPs on a no-special surface-treated substrate is still a formidable challenge
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