硼酸对赖氨酸盐酸盐在半胱氨酸自组装膜上晶体生长的影响

研究了利用半胱氨酸自组装膜对诱导L-赖氨酸盐酸盐晶体生长的影响。实验发现,赖氨酸盐酸盐优先在水溶液内而不是在自组装膜表面成核生长为晶体,这是首次发现自组装单层对赖氨酸盐酸盐的成核有抑制作用。对自组装单层上的成核机理进行了探讨,2种氨基酸正电荷间的排斥作用可能是自组装膜抑制赖氨酸盐酸盐成核的原因。在赖氨酸盐酸盐溶液中加入了等摩尔硼酸,XRD结果表明,硼酸晶体优先生长在自组装单层上。而析出后的硼酸晶体又加速促进了赖氨酸盐酸盐的结晶析出。扫描电子显微镜表征发现,加入硼酸后赖氨酸盐酸盐晶体的形貌发生了很大变化,由原来的块状变为针状。实验结果表明,加入硼酸,可以加速赖氨酸盐酸盐的晶体生长并可以调控晶体的形貌和取向。

Effect of Boric Acid on the Crystallization of L-Lysine Monohydrochloride Dihydrate on Self-Assembled Monolayers of L-Cysteine

We investigated the effect of boric acid on the crystallization of L-lysine monohydrochloride dihydrate on self-assembled monolayer(SAM) of L-cysteine.SAM of L-cysteine was employed to induce the crystallization of L-lysine monohydrochloride dehydrate(LMH).It was found that the crystals of LMH grew preferentially in solution rather than on the SAM.That the SAM did not promote but inhibit the nucleation of LMH was found firstly in the research field of inducing crystals by SAM.This unusual result may largely due to the repulsion between the positive charges of the LMH and L-cysteine.The LMH-boric acid(n(LMH)∶n(H3BO3)=1∶ 1) system was introduced to study further.The XRD results showed that diffraction peaks at 14.9° and 27.9° corresponding to the lattice plane of(101) and(112) appeared first.It means that boric acid prefer to grow on the SAM of L-cysteine.Then the LMH crystallization was improved remarkably after the crystallization of boric acid.After 24 h,we obtained diffraction peaks corresponding to the LMH lattice plane of(101) and(112).The SEM results showed that the appearance of the LMH crystal also changed greatly,from massive on the SAM to needle form on boric acid crystals.The above results demonstrated that boric acid could be used to accelerate the growth speed of LMH and affect its crystal morphology significantly.