Thermal Analysis of Gold-Containing Bilayer Peptoid Nanosheets

The plasmonic properties of gold nanoparticles may have applications in detecting organic contaminants in freshwater. The sensing capabilities arise from the opto-electronic properties of plasmonic gold nanoparticles which result from light induced localized surface plasmon resonance (LSPR). Specific frequencies of light generate a strong oscillating electromagnetic field between nanoparticles. Thus, contaminants situated between gold nanoparticles can be detected using plasmonic sensing techniques. The Robertson lab has developed a unique strategy to prepare 2D arrays of gold nanoparticles by embedding them into bilayer peptoid nanosheets prepared at the organic-aqueous interface. Previous experiments using surface functionalized gold nanoparticles with twelve carbon chained ligands resulted in interparticle gaps of slightly different sizes (3nm - 9nm) depending on the nanoparticle concentration used in the synthesis. It is possible to functionalize gold nanoparticles of varying ligand density. Thus, it may be possible to control the interparticle distance of the 5 nm gold nanoparticles within the nanosheets by using AuNPs of varying ligand density on their surfaces. This study explores the assembly of bilayer peptoid nanosheets using gold nanoparticles functionalized with octanethiol. Nanoparticles were functionalized on-site and surface ligand densities were quantified using thermogravimetric analysis. The composition of bilayer nanosheets were identified and quantified using TGA-FTIR-MS. We expect that the surface density of octanethiol ligands will vary by concentration of ligand added during nanoparticle functionalization and that nanoparticles with greater ligand densities will produce stable nanosheet structures with smaller inter-particle gaps between gold nanoparticles. Results from this study will be critical to optimizing the properties of the sheets so that they can be used as effective pollutant sensors.