SERS substrates based on polymer-protected self-assembled plasmonic films with gold nanoparticles as enhancing element of a microfluidic sensor

We report a self-assembled plasmonic film of 20 nm gold nanoparticles with a protective polymer matrix enabling detection of SERS signals in flow-through microfluidic chips, various environments and pH ranging from 3 to 9, and with a temperature applicability limit of ∼150 °C. Proposed SERS substrate as a sensing platform has demonstrated the retention of its enhancement characteristics with transfer from stationary spectroscopy to microfluidic systems, as well as the ability to be reused and quickly respond to changes in the analyte. The detection limit of such a system based on a model analyte (pseudoisocyanine) in an isopropanol solution was determined as 10⁻¹² M. Our SERS-based sensor have demonstrated clear visibility for real analytes, such as solutions containing various amino acids with different side chains, even at a concentration as low as 10⁻⁵ M.