Peng Rui, Khan Muhammad Asadullah, Wu Jiao, Chen Zhen
Department of Applied Chemistry, School of Natural Science, Anhui Agricultural University, Hefei, Anhui 230036, China.
Langmuir. 2022 Apr 5;38(13):4121-4128. doi: 10.1021/acs.langmuir.2c00218. Epub 2022 Mar 25.
monitoring of microemulsion-based nanoparticle synthesis is significant for understanding the particle formation mechanism and for advancing controlled nanoparticle synthesis by this means. In this study, the processes of silica nanoparticle synthesis in a CTAB/-hexanol/cyclohexane/ammonia microemulsion were monitored via dielectric spectroscopy and in real time, with the influences of the water content and precursor concentration being considered. Two dielectric relaxations in addition to a water-induced one were observed in the frequency range of 1 MHz to 3 GHz, which persist throughout the synthesis processes. It is suggested that the lower-frequency relaxation is ascribed to interfacial polarization and the higher-frequency one is caused by the orientational polarization of the ion pair consisting of a counterion and a surfactant polar group. The latter and water-induced relaxations were found to be barely changed during the synthesis processes, while the former changes obviously with synthesis time. The evolution of the lower-frequency relaxation and direct current conductivity with synthesis time are presented and discussed, on the basis of which the particle formation process is inspected from a dielectric spectroscopic point of view.
监测基于微乳液的纳米颗粒合成对于理解颗粒形成机制以及推进通过这种方法进行的可控纳米颗粒合成具有重要意义。在本研究中，通过介电谱实时监测了在CTAB/正己醇/环己烷/氨水微乳液中二氧化硅纳米颗粒的合成过程，并考虑了水含量和前驱体浓度的影响。在1 MHz至3 GHz的频率范围内，除了水诱导的弛豫外，还观察到两种介电弛豫，它们在整个合成过程中持续存在。研究表明，低频弛豫归因于界面极化，高频弛豫是由抗衡离子和表面活性剂极性基团组成的离子对的取向极化引起的。发现后者和水诱导的弛豫在合成过程中几乎没有变化，而前者随合成时间明显变化。给出并讨论了低频弛豫和直流电导率随合成时间的演变，在此基础上从介电谱的角度考察了颗粒形成过程。
