Engineered Sers Substrates Employing Nanoparticle Cluster Arrays with Multiscale Signal Enhancement
Defined nanoparticle cluster arrays (NCAs) with total lateral dimensions of up to 25.4 [mu]m by 25.4 [mu]m have been fabricated on top of a 10 nm thin gold film using template guided self-assembly. This approach provides precise control of the structural parameters in the arrays allowing a systematic variation of the average number of nanoparticles in the clusters (n) and the edge to edge separation (?) between 1 < n < 20 and 50 nm =?=1000 nm, respectively. Investigations of the Rayleigh scattering spectra and surface enhanced Raman scattering (SERS) signal intensities as a function of n and ? reveal direct near-field coupling between the particles within individual clusters, whose strength increases with the cluster size (n) until it saturates at around n = 4. Our analysis shows that strong near-field interactions between individual clusters significantly affects the SERS signal enhancement for edge-to-edge separations ? < 200 nm. The observed dependencies of the Raman signals on n and ? indicate that NCAs support a multiscale signal enhancement which originates from simultaneous inter- and intra-cluster coupling and ¦E¦- field enhancement. The NCAs provide strong SERS signals of bacterial cells thus enabling a rapid and reliable spectral identification of bacteria.
REINHARD BJOERN MARCUS [US]; DAL NEGRO LUCA [US]
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