M. Jones
University of Texas at Austin,
United States
Keywords: s-SNOM, infrared spectroscopy, microplastics, plasmons
Summary:
Scattering-scanning near-field optical microscopy (s-SNOM) is a scanning probe technique which couples an atomic force microscope (AFM) with a Fourier transform infrared spectrometer (FTIR). This technique allows the user to collect infrared absorption at a nanoscale, far below the diffraction limit of infrared light (approximately 2 microns). Our instrument can both collect single wavelength images of samples, as well as collect spectra at single locations under the cantilever tip. With this we are able to push the boundaries of what systems can be studied with infrared spectroscopies. We highlight two ongoing systems of interest we have studied with our setup, which demonstrates the broadness in applications of this method. Current work has focused studying microplastic degradation, an application relevant to sustainability and pollution reduction. It is well known that plastics break down in the environment through both physical and chemical weathering caused by the ocean and solar radiation. These plastics leach micro and nano sized particles into the water system. The physical characteristics of this degradation process at a nano scale are less understood, and our ongoing research seeks to fill this gap. Effort has gone into roughness analysis of artificially aged plastics through topographic image analysis, giving us a nano sized view of physical changes through time. Additionally, infrared imaging can give us a nano-sized view of chemical changed induced from aging. We have also studied new meta-material systems, with a focus on plasmonic indium tin oxide nanocrystals (ITO NCs). These superlattice materials are self-assembled and have applications in controlling optical and chemical phenomena. S-SNOM allows for the direct measurement of plasmonic hot spots between NCs. This, coupled with changing fabrication parameters allows for the direct design of these superlattice's near-field response.