Nanoscale chemical mapping of laser-solubilized silk

TL;DR

This study demonstrates nanoscale IR mapping to chemically characterize laser-solubilized silk, revealing its amorphous state with high spatial resolution and confirming the technique's reliability compared to synchrotron IR.

Contribution

It introduces a method for nanoscale chemical mapping of silk using laser-induced amorphization and IR spectroscopy, achieving high spatial resolution and specificity.

Findings

Nanoscale IR mapping can distinguish amorphous from crystalline silk.

Laser irradiation induces amorphization detectable by IR spectroscopy.

High spatial resolution (~20 nm) is achievable in chemical imaging.

Abstract

A water soluble amorphous form of silk was made by ultra-short laser pulse irradiation and detected by nanoscale IR mapping. An optical absorption-induced nanoscale surface expansion was probed to yield the spectral response of silk at IR molecular fingerprinting wavelengths with a high ~20 nm spatial resolution defined by the tip of the probe. Silk microtomed sections of 1-5 micrometers in thickness were prepared for nanoscale spectroscopy and a laser was used to induce amorphisation. Comparison of silk absorbance measurements carried out by table-top and synchrotron Fourier transform IR spectroscopy proved that chemical imaging obtained at high spatial resolution and specificity (able to discriminate between amorphous and crystalline silk) is reliably achieved by nanoscale IR. A nanoscale material characterization using synchrotron IR radiation is discussed.