Seminar
Tuesday, October 30, 2018 - 12:00am
Graduate Student Le Wang will present
"Peak Force Infrared Microscopy: Correlative Infrared and Mechanical Imaging at sub 10 nm Spatial Resolution"
on October 30, 2018 at 4:10 PM in Neville Hall, Room 3
Abbe’s optical diffraction limit impedes nanometer-scale spatial resolution for conventional microscopy and spectroscopy. However, the combination of scanning probe microscopy and laser illumination provides new ways to bypass the diffraction limit. One of these imaging techniques, infrared scattering-type scanning near-field optical microscopy (s-SNOM), is to demodulate the near-field light scattering signal from a metallic AFM tip to locally enhance the optical field and probe the polaritonic properties of the sample.1-3 The other family of high spatial resolution imaging technique is action- or force-based infrared microscopy, which measures the light-induced thermal expansions in the sample4 or the photo-induced force from the dipole-dipole interaction between the tip and sample5-6. However, these techniques are not capable of providing multimodal chemical and mechanical correlations due to the constraints from instrumental complexities. Recently our research group has developed a new type of scanning probe microscopy: peak force infrared microscopy (PFIR).7 It combines the peak force tapping (an operational mode of AFM from Bruker Nano) with a synchronized pulsed mid-infrared light source, and enables chemical imaging, broadband spectroscopy and mechanical mapping at a spatial resolution of ~10 nm. In this presentation, I will describe the mechanism and technical details of PFIR microscopy, and its applications in characterizing soft polymers, urban aerosols (particulate matter PM2.5)8, as well as biological samples. The high spatial resolution and multimodal characterization ability of PFIR microscopy will provide a powerful analytical tool for nanoscale explorations across wide disciplines. References (1) Knoll, B.; Keilmann, F. Near-Field Probing of Vibrational Absorption for Chemical Microscopy. Nature 1999, 399, 134-137. (2) Wang, L.; Xu, X. G. Scattering-Type Scanning Near-Field Optical Microscopy with Reconstruction of Vertical Interaction. Nat. Commun. 2015, 6, 8973. (3) Wang, H.; Wang, L.; Jakob, D. S.; Xu, X. G. Tomographic and Multimodal Scattering-Type Scanning Near-Field Optical Microscopy with Peak Force Tapping Mode. Nat. Commun. 2018, 9, 2005. (4) Anderson, M. S. Infrared Spectroscopy with an Atomic Force Microscope. Appl. Spectrosc. 2000, 54, 349-352. (5) Nowak, D.; Morrison, W.; Wickramasinghe, H. K.; Jahng, J.; Potma, E.; Wan, L.; Ruiz, R.; Albrecht, T. R.; Schmidt, K.; Frommer, J.; et al. Nanoscale Chemical Imaging by Photoinduced Force Microscopy. Sci. Adv. 2016, 2, e1501571. (6) Wang, L.; Wang, H.; Vezenov, D. V. and Xu, X. G. Direct Measurement of Photo-Induced Force for Nanoscale Infrared Spectroscopy and Chemical-Sensitive Imaging. J. Phys. Chem. C 2018, 122, 23808-23813. (7) Wang, L.; Wang, H.; Wagner, M.; Yan, Y.; Jakob, D. S.; Xu, X. G. Nanoscale Simultaneous Chemical and Mechanical Imaging via Peak Force Infrared Microscopy. Sci. Adv. 2017, 3, e1700255. (8) Wang, L.; Huang, D.; Chan, C. K.; Li, Y. J.; Xu, X. G. Nanoscale Spectroscopic and Mechanical Characterization of Individual Aerosol Particles Using Peak Force Infrared Microscopy. Chem. Commun. 2017, 53, 7397-7400.