巯基乙胺自组装膜表面润湿性的变化

报道了巯基乙胺自组装膜在不同的时间尺度内表面润湿性的特征变化.利用接触角滴定方法对其表面状态进行实时监控表明,自组装膜由固/液界面转移至固/气界面后,接触角在短时间内经历了一个快速升高过程和一个相对较慢的变化过程.从表面自由能的角度,讨论了该现象的机理.采用不同pH值的缓冲溶液进行接触角滴定,得到了巯基乙胺自组装膜的滴定曲线,从而确定表面pKb值为1.7±0.2.从接触角滴定曲线在长时间内的变化趋势中发现,pK_b值无显著变化,但曲线整体向上平移,并且滴定曲线中上下平台的差值随时间增长而减小.

Real-time Characterization for Surface Wettibility of Cysteamine Self-asembled Monolayers on Gold

The characteristic change of surface wettibility of cysteamine self-assembled monolayers was reported. Contact angle titration method was used to carry out the real time measurements of the surface wettibility of the monolayers which were formed by dipping gold substrate into dilute HSCH₂CH₂NH₂/CH₃CH₂OH solution. After the monolayers transfered from solid/liquid interface to solid/air interface, the contact angles of the monolayers underwent a sharp increase, then got down to a slow variation process. From the perspective surface free energy, the structural rearrangement of monolayers was considered as the main reason for such a phenomenon. The contact angle titration curve for basic group tailored SAM swas obtained by using a series of solutions with different pH values. The pK_b value of cysteamine SAM swas derived to be 1.7±0.2. Based on above characterization, the change of surface wettibility for the monolayers was further studied at a long time scale by taking account of changes in pK_b and △θ (difference between two plateaus of the contact angle titration curve).