Spatially Separated Self-Assembled Silver Dendrites for Highly Sensitive SERS Applications

Abstract: Even after more than four decades of rapid-pace advances, the adoption of Surface-Enhanced Raman Scattering (SERS) remains limited, due to the difficulties in fabrication of effective and affordable nanostructured surfaces or templates. From this point-of-view, self-assembly techniques of SERS substrates formation allowing fabrication of highly branched dendritic silver nanostructures, which are very promising for biosensor applications. However, these techniques suffer from the lack of control over the resulting structures. Herein, we propose an electroless wet-chemical approach for highly reproducible fabrication of spatially separated plasmonic active silver dendrites in a porous matrix of Si/SiO2 template via controlled self-assembly of silver in a limited volume. The proposed approach allows fabrication of spatially separated silver dendrites with sub-10-nm gaps between neighboring branches, which possessing strong electric field enhancement in a wide spectral range. The fabricated silver dendritic structures enable a SERS enhancement factor of ~10^8 and the analyte detection limit of ~10^-15 M, which is at the level of single molecule sensitivity. The comparison of simulation results with SERS experiments allows to distinguish the presence of electromagnetic and chemical contributions, which have a different effect at various analyte concentrations.