Naval Research Laboratory, Washington, DC 20375-5347, United States.
Langmuir. 2010 Dec 7;26(23):18144-54. doi: 10.1021/la103381r. Epub 2010 Nov 11.
Infrared attenuated total reflection spectroscopy has been used to study the interaction of DMMP vapor with SiO(2), Al(2)O(3), and AlO(OH) vs relative humidity (RH) and DMMP partial pressure (P/P(0)). For SiO(2) the growth with increasing RH of ice-like and liquid-like layers is seen in agreement with previous work. H↔D exchange during exposure to H(2)O and D(2)O indicates that the ice-like layer is more resistant to exchange, consistent with stronger H-bonding than in the liquid-like layer. Exposure of nominally dry SiO(2) to D(2)O indicates the existence of adsorbed H(2)O that does not exhibit an ice-like spectrum. The ice-like layer appears only at a finite RH. Exposure of SiO(2) to DMMP in the absence of intentionally added H(2)O shows the formation of a strongly bound molecular species followed by a liquid-like layer. The strong interaction involves SiO-H···O═P bonds to surface silanols and/or HO-H···O═P bonds to preadsorbed molecular H(2)O. At a finite RH the ice-like layer forms on SiO(2) even in the presence of DMMP up to P/P(0) = 0.30. DMMP does not appear to penetrate the ice-like layer under these conditions, and the tendency to form a such a layer drives the displacement of DMMP. Amorphous Al(2)O(3) and AlO(OH) do not exhibit an ice-like H(2)O layer. Both have a higher surface OH content than does SiO(2), which leads to higher coverages of H(2)O or DMMP at equivalent RH or P/P(0). At low P/P(0), for which adsorption is dominated by Al-OH···O═P bonding, a-Al(2)O(3) interacts with DMMP more strongly than does AlO(OH) as a result of the higher acidity of OH sites on the former. Up to RH = 0.30 and P/P(0) = 0.30, DMMP appears to remain bonded to the surface rather than being displaced by H(2)O. H(2)O appears to have little or no effect on the total amount of DMMP adsorbed on any of these surfaces, up to an RH of 0.30 and a P/P(0) of 0.30. The results have implications for the transport of DMMP and related molecules on oxide surfaces in the environment.
中红外衰减全反射光谱已被用于研究 DMMP 蒸气与 SiO2、Al2O3 和 AlO(OH)在相对湿度 (RH)和 DMMP 分压 (P/P0)下的相互作用。对于 SiO2，随着 RH 的增加，观察到冰状和液态层的生长，这与先前的工作一致。暴露于 H2O 和 D2O 时的 H↔D 交换表明，冰状层更不易交换，这与液态层中更强的氢键一致。暴露于 D2O 的名义干燥的 SiO2 表明存在吸附的 H2O，它不表现出冰状光谱。冰状层仅在有限的 RH 下出现。在没有故意添加 H2O 的情况下，将 DMMP 暴露于 SiO2 上，会先形成一个强结合的分子物种，然后是一个液态层。这种强相互作用涉及到 SiO-H···O═P 键与表面硅醇和/或 HO-H···O═P 键与预吸附的分子 H2O 的结合。在有限的 RH 下，即使在 DMMP 存在下，SiO2 上也会形成冰状层，直至 P/P0=0.30。在这些条件下，DMMP 似乎不会穿透冰状层，形成这种层的趋势推动了 DMMP 的置换。无定形 Al2O3 和 AlO(OH) 没有表现出冰状的 H2O 层。它们的表面 OH 含量均高于 SiO2，这导致在等效 RH 或 P/P0 下，H2O 或 DMMP 的覆盖率更高。在低 P/P0 下，吸附主要由 Al-OH···O═P 键合控制，α-Al2O3 与 DMMP 的相互作用比 AlO(OH)更强，这是由于前者 OH 位的酸性更高。在 RH=0.30 和 P/P0=0.30 以下，DMMP 似乎仍然与表面键合，而不是被 H2O 置换。H2O 似乎对这些表面上吸附的 DMMP 的总量几乎没有或没有影响，直至 RH 为 0.30 和 P/P0 为 0.30。这些结果对氧化物表面上 DMMP 和相关分子的传输具有重要意义。
