Identification of Nanoscale Polymer Structures by AFM Based Infrared Nanospectroscopy

Nanoscale resolved imaging & spectroscopy (nano-IR) using tip-enhanced infrared (IR) microscopy & spectroscopy [1] achieves spatial resolution of &lt; 10-20 nm enabling chemical identification of polymer nanostructures at unprecedented length scales and sensitivity.<br/><br/>Infrared nanospectroscopy is based on scattering-type Scanning Near-field Optical Microscopy (s-SNOM) or tapping AFM-IR (local detection of photothermal expansion) and enables bypassing the diffraction limit of light and to achieve a wavelength-independent spatial resolution. In this work we demonstrate identification of PMMA, PC and PVAC polymer nanostructures based on the comparison of measured nano-IR absorption spectra with ATR-FTIR reference spectra. Tuning the infrared laser source to specific frequencies (e.g. 1735cm^-1 for PMMA or 700cm^-1 for PS) enables to selectively map the spatial distribution of materials with sensitivity down to few nm thin particles. Nano-IR measurements on easy-to-handle silicon membrane filters compatible with microplastic analysis routines are demonstrated.<br/><br/>Nano-IR identification of polymer nanostructures has already been demonstrated for analysis of small micro- and nano-plastics which are difficult to access by other methods [2,3]. Further, weathering of PET was compared to fresh samples verified the high quality of nano-IR based material identification.<br/><br/>Lastly, introducing a novel liquid/flow cell design based on a liquid reservoir capped by an ultrathin SiN-membrane, we will demonstrate s-SNOM nano-imaging and spectroscopy of polymer micro- and nano-particles and living cells [4] immersed in aqueous environment.<br/><br/>References:<br/>[1] F. Keilmann, R. Hillenbrand, Phil. Trans. Royal Society A, 362, 787–805, (2004).<br/>[2] M. Meyns, et al., Analytical Methods, 15, 606 (2022)<br/>[3] M. Goikoetxea, et al., Marcomolecules, 54, 995 (2021)<br/>[4] K. Kaltenecker, et al., Scientific Reports, 11, 21860 (2021)