Non-hydrostatic pressure-induced phase transitions in self-assembled diphenylalanine microtubes

The structural phase transitions in diphenylalanine microtubes caused by an increase in the non-hydrostatic pressure have been examined. Raman scattering investigations have been carried out and the results obtained have been interpreted and analyzed. Spectral variations in the ranges of phenyl ring vibrations and high-frequency oscillations of NH and CH groups have been analyzed. Under pressures of up to 9.8 GPa, four spectral anomalies indicative of the occurrence of phase transitions have been observed. The transitions under pressures of 1.7 and 4 GPa are shown to be reversible. The transition at 5.7 GPa is accompanied by partial sample amorphization.