Deposition and characterization of peptoid-gold nanoparticle composite films assembled at fluid interfaces

The ability to detect water pollutant levels rapidly and accurately is critical to assessing their immediate impacts on human health. Traditional surface enhanced Raman scattering (SERS) sensors based on colloidal gold nanoparticles (AuNPs) have successfully been used to detect low levels of pollutants in water. However, these sensors can be highly unstable when in the presence of complex sample matrices like those found in environmental samples. SERS sensors based on highly ordered two-dimensional AuNP arrays have the potential to overcome these limitations, but reproducibly preparing these arrays still remains a challenge. This study focuses on preparing highly ordered two-dimensional AuNP arrays at the air-water and oil-water interface using a combination of hydrophobically modified AuNPs and amphiphilic peptoid polymers. Peptoids are a relatively new class of peptidomimetics that are easily synthesized, more stable than peptides, and can be programmed to bind targets like pollutants with high sensitivity. The peptoid-AuNP composite arrays were assembled in a Langmuir Trough where surface pressure vs. area measurements were used to investigate the interactions between the peptoid and AuNP ligands. Raman spectroscopy, atomic force microscopy, and scanning electron microscopy were used to characterize composite films that had been deposited on solid substrates using the Langmuir-Blodgett method. Initial results suggest that the peptoid impacts the ordering of the AuNPs in composite films. These studies are critical to providing information on how the film will behave as a functional SERS sensor.