Investigation into Low Temperature Behavior of Boson Peak of Natural Polymer Starch by Terahertz Time-Domain and Low-Frequency Raman Spectroscopies

Abstract

The boson peak (BP) dynamics of semicrystalline starch was investigated using terahertz time-domain spectroscopy (THz-TDS) and low-frequency Raman spectroscopy. The BP of starch was observed around 1.0 THz in the α(ν)/ν2 spectrum obtained by THz-TDS, where α(ν) is absorption coefficient. Comparing with the previous study of glucose glass, we found that the BP frequency of starch was about 10 % lower than that of the glucose glass, and the value of α(ν)/ν2 was about 30 % smaller than the glucose glass. The results suggest that the origin of absorption around BP frequency is the dipole moment of the hydroxyl group and the α(ν) is proportional to the number of hydroxyl groups per unit volume.