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. Author manuscript; available in PMC: 2018 Dec 19.
Published in final edited form as: Anal Chem. 2017 Dec 6;89(24):13524–13531. doi: 10.1021/acs.analchem.7b03878

Figure 1.

Figure 1

a) Sketch illustrating the PTIR setup and signal generation. The sample (blue) is placed on a ZnSe Prism (yellow) and illuminated from below with a pulsed, infrared laser beam (red). The sample locations that absorb IR light, heat up and expand during each laser pulse. The expansion induced motion of the AFM tip (gold), deflection signal, is detected by the AFM detector. b) time domain PTIR signal (ring-down). c) The fast Fourier transform (FFT) on the deflection signal, yields the amplitudes of the cantilever oscillation modes which are proportional to the local infrared absorption.