Two-dimensional (2-D) gold nanoparticle self-assemblage is currently the subject of exploration for various applications in sensing, diagnostics, and catalysis. In particular, 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 that 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. We can take advantage of the plasmonic properties of these nanoparticles depending on how well the formation of the 2-D arrays can be controlled. Our lab has developed a unique strategy to prepare 2-D arrays of gold nanoparticles by embedding them into bilayer peptoid nanosheets prepared at the oil-water interface. The nanosheets are synthesized with plate-shaker automated agitation of vials containing the gold nanoparticles dissolved in toluene and an aqueous solution containing 2mM peptoid. Previous experiments using surface functionalized gold nanoparticles with twelve carbon chained ligands have been able to create interparticle gaps of slightly different sizes (3nm - 9nm) depending on the nanoparticle concentration used in the synthesis. It may be possible to control the interparticle distance of the 5nm gold nanoparticles within the nanosheets by using ligands of differing carbon chain lengths. In this experiment, we are assembling bilayer peptoid nanosheets using gold nanoparticles functionalized with octanethiol—having an eight carbon chain—at concentrations between 0.05 mg/mL and 2.5 mg/mL. We expect the octanethiol ligand to produce stable nanosheet structures with smaller inter-particle gaps between gold nanoparticles at the higher bulk nanoparticle concentrations.