Department of Chemical Engineering, Kyung Hee University, Yongin-si, Gyeonggi-do, Korea.
Anal Chem. 2013 May 7;85(9):4790-6. doi: 10.1021/ac400585c. Epub 2013 Apr 17.
A quartz crystal microbalance (QCM) technique is developed for the in situ analysis of the cooling crystallization processes of crystal nucleation and growth. In contrast to conventional techniques based on property changes in the solid or solution phase, the proposed QCM technique simultaneously exploits property changes in both the solid and solution phases, such as the solid mass and liquid viscosity, to analyze the crystallization processes. When initially cooling the solution, an increase in the solution viscosity is reflected in the QCM responses for the resonant frequency and resonant resistance. With further cooling, the resonant frequency and resonant resistance sharply change at the induction point of crystal nucleation, as the viscous liquid film on the sensor suddenly shifts to an elastic solid phase. Thereafter, the QCM responses are mainly controlled by the suspension viscosity due to simultaneous crystal nucleation and growth with further cooling. As a result, the QCM responses allow accurate measurement of the induction point and metastable zone width during the cooling crystallization. Additional mechanistic information on the crystallization, including molecular cluster formation, crystal nucleation, and crystal growth, is also extracted from a resonant frequency-resistance plot (F-R plot) of the QCM responses when varying the cooling conditions.
石英晶体微天平(QCM)技术被开发用于原位分析晶体成核和生长的冷却结晶过程。与传统基于固相与液相中性质变化的技术不同，所提出的 QCM 技术同时利用固相与液相中的性质变化，如固相质量和液相粘度，来分析结晶过程。在最初冷却溶液时，溶液粘度的增加反映在 QCM 响应的共振频率和共振电阻上。随着进一步冷却，当传感器上的粘性液膜突然转变为弹性固相时，在晶核诱导点处，共振频率和共振电阻急剧变化。此后，随着进一步冷却时的同时成核和生长，QCM 响应主要受悬浮液粘度的控制。因此，QCM 响应可以准确测量冷却结晶过程中的诱导点和亚稳区宽度。通过改变冷却条件，从 QCM 响应的共振频率-电阻图（F-R 图）中还提取了有关结晶的其他机制信息，包括分子簇形成、晶体成核和晶体生长。
