Development of a SERS-Based Sensor for Monitoring Air Quality in Space Cabin Environments

A surface enhanced Raman scattering (SERS) spectroscopy-based sensor is being developed for monitoring volatile organic compounds in air aboard spacecraft. The features of the sensor will include high sensitivity, high selectivity, a low impact design in terms of size and weight, and no chemical waste production. The key components of the sensor are a laser source, a SERS-active substrate and a spectrograph with an array detector. The sensor substrates are based on silver or gold metal and provide an adsorber surface for the targeted compounds. The metal surfaces can be coated with a polymer or a self-assembled monolayer of a thiol-linked organic compound to protect the surface and increase the adsorption of analytes to the surface. Chemical modification of the coating will allow the selectivity of the sensor to be “tuned” to favor the adsorption of specific analytes. Several metal surfaces are under investigation, including surface bound monolayers of gold or silver nanoparticles, silver-coated membranes, silver- and gold-coated silica particles and thermally evaporated films of gold or other metals. Studies are being performed to evaluate the relative merits of the surfaces and emphasis is being placed on optimizing preparation of the surfaces and their analytical utility for trace measurements. The current results indicate that parts per million levels of model analytes are readily measured at two different silver surfaces and that picogram masses can be detected.