Forces between nitrogen-containing self-assembled monolayers (SAMs) and zirconia particles in aqueous solutions
作者:Jing-Jong Shyue、Yin Tang、Mark R. De Guire*
DOI:10.1039/b405788k
日期:——
An atomic force microscope was used to measure the interaction forces between siloxane-anchored organic self-assembled monolayers (SAMs) with nitrogen-containing surface groups on silicon and micron-sized zirconia spheres in aqueous electrolyte solutions. The surface groups studied were alkylammonium salt and amines (primary, secondary, and tertiary). The pH of the solutions ranged from 2.5 to 9 (controlled by adding NaOH or HCl), and their ionic strength was held constant at 0.022 m
(by adding NaCl). The results indicated that the alkylammonium salt surface exhibits a standard Debye double layer, whereas all of the amine surfaces exhibited a Stern layer, i.e. a charge inversion layer. The observed interactions were similar for SAMs formed from surfactants of two different alkyl chain lengths (11 and 16). The corresponding electrostatic interactions comprise the dominant part of the DLVO interactions under the conditions studied. The observed forces were consistent with film deposition results: vanadia films, but not titania films, form on alkylammonium salt surfaces; whereas both titania and vanadia films deposit on amine surfaces.
利用原子力显微镜测量了硅氧烷锚定有机自组装单层(SAM)与硅和微米大小的氧化锆球表面含氮基团在电解质水溶液中的相互作用力。研究的表面基团为烷基铵盐和胺(伯、仲、叔)。溶液的 pH 值范围为 2.5 至 9(通过添加 NaOH 或 HCl 控制),离子强度恒定为 0.022 m(通过添加 NaCl)。结果表明,烷基铵盐表面呈现出标准的德拜双电层,而所有胺表面都呈现出斯特恩层,即电荷反转层。对于由两种不同烷基链长(11 和 16)的表面活性剂形成的 SAM,观察到的相互作用也类似。在所研究的条件下,相应的静电相互作用是 DLVO 相互作用的主要部分。观察到的作用力与薄膜沉积结果一致:在烷基铵盐表面形成的是二氧化钒薄膜,而不是二氧化钛薄膜;而在胺表面沉积的则是二氧化钛和二氧化钒薄膜。