Solvent molecules dominated phase transition of amorphous Se colloids probed by in-situ Raman spectroscopy

The solid-liquid interfacial interactions between nanoparticles and solvent molecules plays an important role in the growth and phase transition of nanoparticles in colloidal solution. Selenium (Se) colloids with amorphous phase (a-Se) are initially synthesized by laser ablation of Se target in deionized water, which are subsequently collected and redispersed in three typical polar aprotic solvents, including dimethyl formamide, acetone and ethyl acetate. A liquid phase in-situ Raman spectroscopy (LPRS) is used to monitor the phase transition of a-Se to trigonal Se (t-Se) colloids in various polar aprotic solvents under room temperature and pressure. Corresponding results reveal that the kinetics of phase transition from a-Se to t-Se is a kind of power function. Moreover, it is interesting that the rate of phase transition of a-Se colloids in various solvents increases in proportion to the polarity of solvents molecules, namely a-Se colloids display the fastest phase transition in dimethyl formamide, then followed by acetone and ethyl acetate in turn. These findings demonstrate that polar aprotic solvent molecules have strong correlation with solid-liquid interfacial interactions and dominate the kinetics of phase transition of a-Se colloids.