1H fast MAS NMR studies of hydrogen-bonding interactions in self-assembled monolayers.
1H fast MAS NMR studies of hydrogen-bonding interactions in self-assembled monolayers.
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DOI：
10.1021/ja029008u
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发表时间：
2003-04
影响因子：
15
通讯作者：
S. Pawsey;M. Mccormick;S. D. De Paul;R. Graf;Y. S. Lee;L. Reven;H. Spiess
中科院分区：
文献类型：
--
作者：
S. Pawsey;M. Mccormick;S. D. De Paul;R. Graf;Y. S. Lee;L. Reven;H. Spiess
采用（1）H快魔角自旋（MAS）、HETCOR和（1）H双量子（DQ）MAS固体核磁共振实验研究了羧基膦酸在金属氧化物表面吸附形成的结构。二酸HO（2）C（CH（2））（n）PO（3）H（2）（n = 2，3，11和15）分别吸附在平均粒径为20，30和5 nm的TiO（2）和两种ZrO（2）粉末上。羧基烷基膦酸通过膦酸酯基团选择性地结合，形成具有侧基羧酸基团的单层。而偶极耦合的P-OH质子在TiO（2）上被检测到，在ZrO（2）上仅存在孤立的残余P-OH基团，这反映了膦酸在这两种基底上的相对结合强度。通过对类似单层体系HO（2）C（CH（2））（7）SH包覆的金纳米粒子的比较（1）H MAS NMR研究，发现单层/空气界面处的氢键网络相当无序，至少对于沉积在非平面基底上的自组装膜而言是如此。而只有氢键的同二聚体发生在本体二酸，羧基和膦酸基团之间的氢键存在于ZrO（2）纳米粉末上的二酸的多层。
The structures formed by the adsorption of carboxyalkylphosphonic acids on metal oxides were investigated by (1)H fast magic angle spinning (MAS), heteronuclear correlation (HETCOR), and (1)H double-quantum (DQ) MAS solid-state NMR experiments. The diacids HO(2)C(CH(2))(n)PO(3)H(2) (n = 2, 3, 11, and 15) were adsorbed on TiO(2) and two types of ZrO(2) powders having average particle sizes of 20, 30, and 5 nm, respectively. Carboxyalkylphosphonic acids bind selectively via the phosphonate group, forming monolayers with pendant carboxylic acid groups. Whereas dipolar coupled P-OH protons are detected on TiO(2), there are only isolated residual P-OH groups on ZrO(2), reflecting the relative binding strengths of phosphonic acids on these two substrates. From a comparative (1)H MAS NMR study with an analogous monolayer system, HO(2)C(CH(2))(7)SH coated gold nanoparticles, the hydrogen-bonding network at the monolayer/air interface is found to be quite disordered, at least for SAMs deposited on nonplanar substrates. Whereas only hydrogen-bonded homodimers occur in the bulk diacids, hydrogen bonding between the carboxylic and phosphonic acid groups is present in multilayers of the diacids on the ZrO(2) nanopowder.