Centre Interdisciplinaire des Nanosciences de Marseille, CNRS and Aix-Marseille Université, Campus de Luminy, F-13288 Marseille Cedex 9, France.
J Phys Condens Matter. 2010 Jul 21;22(28):284110. doi: 10.1088/0953-8984/22/28/284110. Epub 2010 Jun 21.
This paper reports on a molecular simulation study of the thermodynamics, structure and dynamics of water confined at ambient temperature in hydroxylated silica nanopores of a width H = 10 and 20 Å. The adsorption isotherms for water in these nanopores resemble those observed for experimental samples; the adsorbed amount increases continuously in the multilayer adsorption regime until a jump occurs due to capillary condensation of the fluid within the pore. Strong layering of water in the vicinity of the silica surfaces is observed as marked density oscillations are observed up to 8 Å from the surface in the density profiles for confined water. Our results indicate that water molecules within the first adsorbed layer tend to adopt a H-down orientation with respect to the silica substrate. For all pore sizes and adsorbed amounts, the self-diffusivity of confined water is lower than the bulk, due to the hydrophilic interaction between the water molecules and the hydroxylated silica surface. Our results also suggest that the self-diffusivity of confined water is sensitive to the adsorbed amount.
本文报道了在环境温度下，水在宽度为 H = 10 和 20 Å 的羟化硅纳米孔中被限制时的热力学、结构和动力学的分子模拟研究。这些纳米孔中水分子的吸附等温线类似于实验样品中观察到的等温线；在多层吸附区，吸附量持续增加，直到由于流体在孔内的毛细冷凝而发生跳跃。在靠近硅石表面的地方观察到强烈的分层水，在限制水的密度分布中，在距表面 8 Å 以内观察到明显的密度振荡。我们的结果表明，第一层吸附水分子倾向于相对于硅石衬底采用 H 向下取向。对于所有的孔径和吸附量，由于水分子和羟化硅表面之间的亲水性相互作用，受限水的自扩散系数都低于本体水。我们的结果还表明，受限水的自扩散系数对吸附量敏感。
