Engineered SERS Substrates with Multiscale Signal Enhancement: Nanoparticle Cluster Arrays
2009; American Chemical Society; Volume: 3; Issue: 5 Linguagem: Inglês
10.1021/nn800836f
ISSN1936-086X
AutoresBo Yan, Anupama Thubagere, W. Ranjith Premasiri, L. D. Ziegler, Luca Dal Negro, Björn M. Reinhard,
Tópico(s)Biosensors and Analytical Detection
ResumoDefined nanoparticle cluster arrays (NCAs) with total lateral dimensions of up to 25.4 μm × 25.4 μm 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 (Λ) between 1 < n < 20 and 50 nm ≤ Λ ≤ 1000 nm, respectively. Investigations of the Rayleigh scattering spectra and surface-enhanced Raman scattering (SERS) signal intensities as a function of n and Λ 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 affect the SERS signal enhancement for edge-to-edge separations Λ < 200 nm. The observed dependencies of the Raman signals on n and Λ indicate that NCAs support a multiscale signal enhancement which originates from simultaneous inter- and intracluster coupling and |E|-field enhancement. The NCAs provide strong and reproducible SERS signals not only from small molecules but also from whole bacterial cells, which enabled a rapid spectral discrimination between three tested bacteria species: Escherichia coli, Bacillus cereus, and Staphylococcus aureus.
Referência(s)