Brandel Clément, ter Horst Joop H
Normandie Université, Crystal Genesis Unit, SMS, Université de Rouen, EA3233, IMR 4114, F-76821 Mont Saint-Aignan Cedex, France.
Faraday Discuss. 2015;179:199-214. doi: 10.1039/c4fd00230j. Epub 2015 Apr 13.
A large variation is observed in induction times measured under equal conditions in 1 ml solutions. Ruling out experimental errors, this variation originates from the nucleation process. The induction time distribution is explained by the stochastic nature of nucleation if the number of nuclei formed is approaching 1 per vial. Accurate heterogeneous crystal nucleation rates were determined from the induction time distributions on a 1 ml scale for racemic diprophylline in two solvents. The difference in nucleation behaviour in the two solvents originates from the energy barrier for nucleation, which is much higher in the solvent in which induction times are much longer. In addition the pre-exponential factor for the crystal nucleation rate in both solvents is rather low compared to predictions using Classical Nucleation Theory. Unfortunately, concentration and surface characteristics of the effective heterogeneous particles are not known which clouds a further molecular interpretation.
在1毫升溶液中于相同条件下测量的诱导时间存在很大差异。排除实验误差后，这种差异源于成核过程。如果每个小瓶中形成的核数接近1个，则诱导时间分布可以用成核的随机性质来解释。从两种溶剂中消旋二羟丙茶碱在1毫升规模上的诱导时间分布确定了准确的非均相晶体成核速率。两种溶剂中成核行为的差异源于成核的能垒，在诱导时间长得多的溶剂中能垒要高得多。此外，与使用经典成核理论的预测相比，两种溶剂中晶体成核速率的指数前因子都相当低。不幸的是，有效非均相颗粒的浓度和表面特性未知，这使得进一步的分子解释变得模糊不清。
