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Near-field IR orientational spectroscopy of silk

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posted on 2024-07-11, 13:40 authored by Meguya Ryu, Reo Honda, Aina Reich, Adrian Cernescu, Jing Liang Li, Jingwen Hu, Saulius JuodkazisSaulius Juodkazis, Junko Morikawa
Orientational dependence of the IR absorbing amide bands of silk is demonstrated from two orthogonal longitudinal and transverse microtome slices with a thickness of only ~100 nm. Scanning near-field optical microscopy (SNOM) which preferentially probes orientation perpendicular to the sample's surface was used. Spatial resolution of the silk-epoxy boundary was ~100 nm resolution, while the spectra were collected by a ~10 nm tip. Ratio of the absorbance of the amide-II C-N at 1512 cm-1 and amide-I C=O β-sheets at 1628 cm-11 showed sensitivity of SNOM to the molecular orientation. SNOM characterisation is complimentary to the far-field absorbance which is sensitive to the in-plane polarisation. Volumes with cross sections smaller than 100 nm can be characterised for molecular orientation. A method of absorbance measurements at four angles of the slice cut orientation, which is equivalent to the four polarisation angles absorbance measurement, is proposed.

Funding

Australian Research Council

Japan Society for the Promotion of Science

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ISSN

2076-3417

Journal title

Applied Sciences (Switzerland)

Volume

9

Issue

19

Article number

article no. 3991

Pagination

3991-

Publisher

MDPI AG

Copyright statement

Copyright © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Language

eng

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