Spiked gold beads as substrates for single-particle SERS.

We introduce a new family of spiked particles resulting from the growth of high aspect ratio gold nanorods. Upon spike growth, elongated beads are obtained with sizes above 300 nm. Interestingly, and in contrast to smooth particles of the same size, these spiked-particles are not only able to sustain localized surface plasmon resonances and consequently enhance Raman signals, but are also big enough to be recognized by standard confocal optical microscopy. These spiked beads have been engineered into thin films to test their surface-enhanced Raman scattering (SERS) enhancing efficiency as a function of the particle density. Such films provide a high level of portability and easiness of use for "in-field" optical ultrasensitive analysis.