Structural information of biopolymer nanofibrils by infrared nanospectroscopy

Abstract Biopolymer nanofibrils, such as chitin and silk nanofibrils, are abundant and critical structural components in nature and materials engineering. However, characterizing these nanofibrils at single fibrillar scale is still a challenging task. Herein, infrared nanospectroscopy (nanoIR), a technique that combines the advances of both atomic force microscopy and infrared spectroscopy, was applied to detect the chemical and structural information of single chitin and silk nanofibrils. The results of this study reveal that nanoIR is a powerful approach to identify the single biopolymer nanofibrils with spatial resolution reaching up to ∼10 nm. In addition, for silk nanofibrils, the results support that nanoIR can be used to analyze the relative content of each secondary structure by deconvolution, because the content of each secondary structure is consistent with the results obtained from the deconvolution of the traditional infrared spectrum. However, the prerequisite for this semi-quantitative analysis is the use of high signal-to-noise ratio spectra, and characteristic peak positions of each secondary structure in nanoIR spectra were predetermined.