A guide to nanoscale IR spectroscopy: resonance enhanced transduction in contact and tapping mode AFM-IR
Jeffrey Schwartz, Devon Jakob, Andrea Centrone
Infrared (IR) spectroscopy is a broadly applicable, composition sensitive analytical technique. By leveraging the high spatial resolution of atomic force microscopy (AFM), the photothermal effect, and wavelength-tunable lasers, AFM IR enables IR spectroscopy and imaging with nanoscale (< 10 nm) resolution. The transduction of a sample's photothermal expansion by an AFM probe tip ensures the proportionality between the AFM IR signal and the sample absorption coefficient, producing images and spectra that are comparable to far-field IR databases and easily interpreted. This convergence of capabilities has spurred robust research efforts to extend AFM IR capabilities and, in parallel, has enabled AFM IR to impact numerous fields. In this tutorial review, we present the latest technical breakthroughs in AFM IR nanoscale spectroscopy and imaging and discuss its working principles, distinctive characteristics, and best practices for different AFM IR measurement paradigms. Central to this review, appealing to both expert practitioners and novices alike, is the meticulous understanding of AFM IR signal transduction, which is essential to take full advantage of AFM IR capabilities. Here, we critically compile key information and discuss instructive experiments detailing AFM IR signal transduction and provide guidelines linking experimental parameters to the measurement sensitivity, lateral resolution, and probed depth. Additionally, we provide in-depth tutorials on the most employed AFM IR variants (resonance-enhanced and tapping mode AFM IR), discussing technical details and representative applications. Finally, we briefly review recently developed AFM IR modalities (peak force tapping IR and surface sensitivity mode) and provide insights on the next exciting opportunities and prospects for this fast-growing and evolving field.
, Jakob, D.
and Centrone, A.
A guide to nanoscale IR spectroscopy: resonance enhanced transduction in contact and tapping mode AFM-IR, Chemical Society Reviews, [online], https://doi.org/10.1039/D2CS00095D, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=934097
(Accessed October 4, 2022)