On-demand microfluidic synthesis of silver nanoparticles for SERS detection of organic compounds: A preliminary feasibility study for astrobiology applications.

The detection of organic molecules at trace concentration levels remains a critical challenge for astrobiology research. While Raman spectroscopy is a powerful and well-established technique for planetary surface investigations, its intrinsic sensitivity often limits the detection of low-abundance biomarkers. Surface-Enhanced Raman Spectroscopy (SERS) offers orders-of-magnitude signal enhancement but has so far faced significant limitations for space applications, particularly in terms of reproducibility, stability, and long-term operability. In this work, we present the development and validation of a microfluidic chip specifically designed for the on-chip synthesis of plasmonic silver colloids and their direct application to SERS analysis. The system enables the controlled and reproducible generation of fresh SERS-active colloids immediately prior to analysis. The system was tested using the ExoMars Raman Laser Spectrometer Simulator (RLS-SIM) to analyze nucleobases (as biomarker proxies) directly on chip. Detection limits between 10-7 and 10-11 M were achieved, representing an improvement of up to seven orders of magnitude compared to conventional Raman measurements. These results demonstrate the strong potential of combining microfluidics and SERS for highly sensitive, reproducible, and compact analytical platforms compatible with planetary exploration constraints. The proposed approach represents a significant step toward the implementation of Raman/SERS hybrid systems for future astrobiology missions aimed at the detection of trace organic compounds on planetary surfaces.