Preparation of nano-t-Se with different Particle sizes and Particle sizes dependence of the melting Thermodynamics
Selenium nanomaterials have unique optical, electrical, magnetic and health care functions. Selenium nanomaterials with different particle sizes have different properties and performances, and the thermal stability of selenium nanoparticles has a key impact on its properties and performances. In this paper, nano-t-Se was prepared by precursor-ultrasonic conversion method. Firstly, the effects of reducing agent dosage, ultrasonic frequency and time on the particle sizes of nano-t-Se were studied, and t-Se nanoparticles with different particle sizes were prepared. Then, the melting thermodynamic properties of nano-t-Se with different particle sizes were determined by DSC. The influence of particle sizes on the melting temperature and thermodynamic properties of nano-t-Se were discussed. The experimental results showed that the precursor-ultrasonic conversion method was a reliable method for preparing t-Se nanoparticles with different particle sizes. By controlling the amount of the reducing agent, ultrasonic frequency and time, the controllable preparation of nano-t-Se with the required particle sizes can be realized. It was found that the particle sizes had significant effects on the melting temperature and the thermodynamic properties of nano-t-Se, and the melting temperature, melting enthalpy and melting entropy of nano-t-Se decreased with the particle sizes decreased, respectively. When the particle sizes of nano-t-Se decreased from 52.1 nm to 17.4 nm, the initial melting temperature decreased from 218.02 ℃ to 213.82 ℃, the melting enthalpy decreased from 5.496 kJ·mol-1 to 3.962 kJ·mol-1, the melting entropy decreased from 5.182 J·mol-1·K-1 to 4.136 J·mol-1·K-1. Except that, It was also found that the initial melting temperature, melting enthalpy and melting entropy of nano-t-Se showed a good linear relationship with the reciprocal of the particle sizes in the experimental particle sizes range, respectively. The controllable preparation method of nano-t-Se with different particle sizes and the particle sizes dependence of the melting temperature and the melting thermodynamic properties can provide important guidance for the preparation, research and application of nano-t-Se.