Silver-nanoparticle-conjugated polypeptide brushes for surface-enhanced raman scattering

A soft surface-enhanced Raman scattering (SERS) substrate was fabricated based on a three-dimensional (3D) structure of biocompatible end-tethered poly(L-lysine) ("t-PLL") with a brushlike configuration conjugated with silver nanoparticles (Ag NPs) (Ag NP-t-PLL film). The conjugation procedures were carefully adjusted to generate the films with different interval widths (W) between Ag NPs and diameters (D) of Ag NPs. The resulting film was then characterized by zeta potential, CD spectropolarimeter, and scanning electron microscopy. Furthermore, the studies of SERS enhancements using Ag NP-t-PLL film as a substrate were performed. The significant increases of SERS enhancements have been obtained as W/D was decreased from 0.9 to 0.2. Our results not only afford a facile fabrication of a 3D soft substrate for SERS with high sensitivity and biocompatibility but also offer great potentials for the development of new biosensors.