The ability to precisely assemble gold nanoparticles (AuNPs) in two-dimensions (2D) is important for fabricating devices that rely on the opto-electronic properties of AuNPs in close proximity, including sensors and catalysts. Nanoparticle assembly at fluid interfaces is a common method to easily prepare 2D AuNP arrays. However, it is challenging to control the exact spacing between AuNPs, a critical parameter in reliable sensors and catalysts, at these surfaces. This study focuses on using amphiphilic peptoid polymers, a class of sequence specific peptidomimetics, to direct the 2D patterning of hydrophobically modified AuNPs at fluid interfaces. The peptoids used in this study readily assemble at fluid interfaces, forming solid-like monolayers that are highly ordered. These monolayers can serve as templates for ordered AuNP assembly, whereby the hydrophobic groups of the peptoid monolayer interact with the hydrophobic AuNP ligands. We show that peptoid-AuNP composite films can be fabricated at both the air-water and the toluene-water interface. At the air-water interface, films were prepared in a Langmuir trough and deposited onto solid substrates. Surface pressure vs. area measurements of the films in the trough along with optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) images of the deposited films indicate that the peptoid monolayer is essential for forming a uniform 2D AuNP array. At the toluene-water interface, aqueous-soluble peptoids and toluene-soluble AuNPs were allowed to self-assemble into highly elastic films that were examined using an optical tesiometer. Results indicate synergism in peptoid-AuNP co-assembly at this fluid interface. Compression of the composite films resulted in film collapse and formation of pepotid-AuNP nanosheets. Optical microscopy, SEM, and AFM images of the nanosheets provide evidence for a structure in which AuNPs are embedded in a pepotid bilayer. Our results suggest that there are multiple avenues for using amphiphilic peptoids to control the 2D assembly of AuNPs at fluid interfaces, forming films that have potential uses as sensors and catalysts.

Peptoid monolayers as versatile templates for the two-dimensional assembly of hydrophobically modified gold nanoparticle at fluid interfaces

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.