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Near-field IR orientational spectroscopy of silk

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journal contribution
posted on 2019-01-01, 00:00 authored by M Ryu, R Honda, A Reich, A Cernescu, Jingliang LiJingliang Li, J Hu, S Juodkazis, J 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 − 1 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.

History

Journal

Applied Sciences (Switzerland)

Volume

9

Article number

ARTN 3991

Pagination

1 - 8

Location

Basel, Switzerland

Open access

  • Yes

eISSN

2076-3417

Language

English

Publication classification

C Journal article, C1 Refereed article in a scholarly journal

Issue

19

Publisher

MDPI