Study on secondary structural transition of nano‐TiO 2 modified silk fibroin composite films by two‐dimensional Raman correlation spectroscopy and solid‐state 13 C‐NMR spectroscopy

By a sol–gel processing, the nano‐TiO 2 / silk fibroin (SF) composite films were prepared. One‐dimensional (1D) Raman, two‐dimensional (2D) correlation Raman spectroscopy, and 13 C cross‐polarization magic‐angle‐spinning nuclear magnetic resonance ( 13 C CP‐MAS NMR) were used to characterize the structural evolution of SF as the nano‐TiO 2 content increased from 0 to 0.4 wt%. The experimental data demonstrated that the secondary structures in the pure SF film and nano‐TiO 2 / silk fibroin (SF) composite films were random coil, α‐helix and β‐sheet structures. The nano‐TiO 2 particles formed in the SF films might induce partial structural transitions from random coil and Silk I (α‐helix) to Silk II ( β ‐sheet). The transition identified by 2D‐Raman correlation spectra was the following order: silk I‐like structure, silk I (α‐helical structure), Silk II‐like structure, and Silk II (β‐sheet structure). POLYM. COMPOS., 36:121–127, 2015. © 2014 Society of Plastics Engineers