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Talks and Poster Presentations (with Proceedings-Entry):

G. Ramer, V. A. Aksyuk, A. Centrone:
"Quantitative Chemical Analysis at the Nanoscale - Using Thin Film Optics to Understand Photothermal Induced Resonance Signal Generation";
Talk: SciX 2018, Atlanta, GA (invited); 10-21-2018 - 10-26-2018; in: "SciX 2018", (2018), 1 pages.



English abstract:
PTIR (often also called AFM-IR) is a technique that allows chemical imaging with nanoscale lateral resolution (<20 nm) [1]. While previous theoretical models for PTIR showed that band positions and relative intensities in PTIR were in general comparable to those found in far-field transmission spectra [2], thin film optics simulations show, that this is not strictly true for a wide range of common sampling parameters. Most importantly, the relationship between the absorption coefficient and the PTIR signal escapes the linear regime for thick or strongly absorbing samples, which impedes quantitation of analytes.

Here, we use thin film optics simulations to calculate the influence of sample properties -thickness, homogeneity, refractive index, concentration, substrate - on the PTIR signal to derive sampling parameters that allow for quantitative PTIR measurements. The same thin film optics calculations can also be used in an algorithm that retrieves optical constants from PTIR spectra and thereby removes non-linearities in PTIR spectra. Thus, these complex refractive index spectra compare well to those collected in far-field, even if above sampling guidelines cannot be followed [3].


[1] Dazzi, A., and Prater, C.B., Chem Rev, 2016. DOI: 10.1021/acs.chemrev.6b00448
[2] Dazzi, A., Glotin, F., and Carminati, R. Journal of Applied Physics, 2010, 107, (12), pp. 124519
[3] Ramer, G., Aksyuk, V.A., Centrone, A. Analytical Chemistry, 2017, 89, (24), pp. 13524/13531

Keywords:
AFM-IR, infrared, QCL, spectroscopy, nanoscale, optics

Created from the Publication Database of the Vienna University of Technology.