Journal: Nature Communications
Article Title: Nanoscale probing of electron-regulated structural transitions in silk proteins by near-field IR imaging and nano-spectroscopy
doi: 10.1038/ncomms13079
Figure Lengend Snippet: ( a ) Schematics of IR nano-spectroscopy using AFM–IR: pulses of IR radiation emitted by an IR QCL (output range: 1,460–1,780 cm −1 , swept by a step size: 1 cm −1 ) were used to illuminate the sample, causing a rapid thermal expansion of silk nanostructures due to local absorption enhancement at various stages picked by the AFM tip, corresponding to the absorption spectroscopic signatures. ( b , c ) The AFM–IR spectra on amorphous and crystalline silk thin films are consistent with the conventional bulk FTIR spectra. ( d , e ) Spectra of a crystalline silk thin film with embedded amorphous silk nanopatterns of ∼30 nm fabricated using EBL, characterized by attenuated total reflection IR (ATR-IR) and AFM–IR, respectively. AFM–IR offers a considerable advancement ( × ∼1,000improvement spatially) in distinguishing nanoscale structural heterogeneity. ( f ) AFM–IR spectra of electron-induced structural transitions in silk proteins. PSD, position sensing detectors; PZT, lead zirconate titanate (Pb[Zr x Ti 1-x ]O3); EC- QCL, external cavity quantum cascade laser.
Article Snippet: To obtain high-resolution optical images and spectroscopic information to map out the nano-chemical and nano-mechanical properties of silk proteins at the molecular level, an s-SNOM (NeaSNOM, Neaspec GmbH, Germany) is coupled to a tunable IR quantum cascade laser (QCL, Daylight Solutions Inc., USA) covering the broad IR spectra of the amide I and II bands over the range from 1,495 to 1,790 cm −1 ( ).
Techniques: Spectroscopy