RUI: Plasmonic Nanoparticle Sandwiches: Using Peptoid Nanosheets as Platforms for Free-Standing Nanoparticle Arrays

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With support from the Macromolecular, Supramolecular and Nanochemistry (MSN) and Chemical Measurement and Imaging (CMI) programs in the Division of Chemistry, Ellen Robertson and her students at Union College are developing methods to prepare two dimensional (2D) molecular nanosheets that incorporate gold and silver nanoparticles. Two-dimensional arrays of gold and silver nanoparticles are promising sensors for detecting hydrophobic pollutants in water, but it is critical that: 1) the arrays remain stable in water; and 2) that the packing arrangement of the particles within the arrays is controllable. Dr. Robertson and her students are using the oil-water interface as a platform to direct the assembly of nanoparticles between two thin molecular layers that are highly water-stable. The discoveries of the Robertson research team could lead to the development of sensors capable of detecting low levels of hydrophobic pollutants in water. This project will help prepare undergraduates at Union for careers and/or graduate studies in STEM (science, technology, engineering and mathematics) by providing hands-on research opportunities for three to five undergraduates each year, with an intentional emphasis on increasing participation of groups underrepresented in STEM; by establishing a collaboration between the Robertson lab at Union College with an R1 institution, enabling undergraduate students to work in a graduate lab setting; and by integrating the research into Union College’s nanotechnology curriculum, engaging a greater number of students. The specific molecular layers that the Robertson lab uses to produce water-stable 2D nanoparticle arrays are composed of amphiphilic peptoid polymers, a relatively new class of peptidomimetics. These polymers form water-stable bilayer peptoid nanosheets through a mechanism at fluid interfaces that involves monolayer assembly and collapse. When carried out at the oil-water interface, hydrophobically functionalized nanoparticles dispersed in the oil phase are incorporated into the peptoid nanosheet hydrophobic interior. By varying the properties of the nanoparticles used in the nanosheet synthesis (i.e., concentration, ligand, core size, and material), Dr. Robertson and her students aim to control the structural and opto-electronic properties of the gold and silver nanoparticle-embedded nanosheets. The effects of the synthesis conditions will be assessed through a variety of characterization techniques, including UV-visible spectroscopy, Raman microscopy, light microscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Nanosheets with promising opto-electronic properties will be tested for their ability to serve as surface enhanced Raman scattering (SERS) sensors to detect hydrophobic pollutants, such as polychlorinated biphenyls, in water.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.