Centre d'Investigació en Nanociència i Nanotecnologia, CIN2(CSIC-ICN), Edifici CM-7, Esfera UAB, Campus de la UAB, E-08193, Bellaterra, Spain.
J Chem Phys. 2011 Mar 28;134(12):124705. doi: 10.1063/1.3571453.
Water molecules strongly interact with freshly cleaved (011) surfaces of L-alanine single crystals at low relative humidity (below 10%) promoting diffusion of L-alanine molecules. Species mobility is enhanced above ~40% leading to the formation of two-dimensional islands with long-range order through Ostwald ripening. Scanning force microscopy experiments reveal that both, islands and terraces, are identical in nature (composition and crystallographic structure) but a relevant friction asymmetry appearing upon water-surface interaction evidences that orientation dependent properties exist between them at the molecular level. We interpret this observation as due to water incorporation in the topmost surface crystal structure. Eventually, for high humidity values, surface dissolution and roughening occur.
水分子在低相对湿度（低于 10%）下与 L-丙氨酸单晶的新切割（011）表面强烈相互作用，促进 L-丙氨酸分子的扩散。在相对湿度高于约 40%时，物种迁移率增强，导致通过奥斯特瓦尔德熟化形成具有长程有序的二维岛。扫描力显微镜实验表明，岛和台地在本质上是相同的（组成和结晶结构），但在水-表面相互作用时出现的相关摩擦不对称性表明，它们在分子水平上存在取向依赖性的性质。我们将这一观察解释为由于水的掺入到最顶层的表面晶体结构中。最终，在高湿度值下，表面溶解和粗糙化发生。
