Rapid Crystallization of l-Alanine on Engineered Surfaces by Use of Metal-Assisted and Microwave-Accelerated Evaporative Crystallization

Abstract

This study demonstrates the application of metal-assisted and microwave-accelerated evaporative crystallization (MA-MAEC) technique to rapid crystallization of L-alanine on surface engineered silver nanostructures. In this regard, silver island films (SIFs) were modified with hexamethylenediamine (HMA), 1-undecanethiol (UDET), and 11-mercaptoundecanoic acid (MUDA), which introduced -NH(2), -CH(3) and -COOH functional groups to SIFs, respectively. L-Alanine was crystallized on these engineered surfaces and blank SIFs at room temperature and using MA-MAEC technique. Significant improvements in crystal size, shape, and quality were observed on HMA-, MUDA- and UDET-modified SIFs at room temperature (crystallization time = 144, 40 and 147 min, respectively) as compared to those crystals grown on blank SIFs. Using the MA-MAEC technique, the crystallization time of L-alanine on engineered surfaces were reduced to 17 sec for microwave power level 10 (i.e., duty cycle 100%) and 7 min for microwave power level 1 (duty cycle 10%). Raman spectroscopy and powder x-ray diffraction (XRD) measurements showed that L-Alanine crystals grown on engineered surfaces using MA-MAEC technique had identical characteristic peaks of L-alanine crystals grown using traditional evaporative crystallization.