Nanoplasmonic Chitosan Nanofibers as Effective SERS Substrate for Detection of Small Molecules

The use of surface enhanced Raman spectroscopy (SERS) is limited by low reproducibility and uniformity of the response. Solving these problems can turn the laboratory use of SERS into real-world application. In this regard, soft SERS-active substrates can enable portable instrumentation and reduce costs in the fabrication of SERS-based sensors. Here, plasmonic free-standing films made of biocompatible chitosan nanofibers and gold nanoparticles are engineered by a simple protocol varying the concentration of chloroauric acid. The concentration and distribution of gold nanoparticles in films are controlled in a predictable way, and SERS spectra for the standard 2-naphthalenethiol with concentration less than 10^-15 M are acquired in a reproducible way. The statistical analysis reveals a relatively high and locally uniform performance of SERS with an enhancement factor of 2 × 10⁵ for 86% of the points on the imaged area of the SERS substrate. Potential SERS detection of small molecules, both Rhodamine 6G and d-Glucose, in the micromolar range is demonstrated.