Findings of Cp Maximum at 233 K for the Water within Silica Nanopores and Very Weak Dependence of the Tmax on the Pore Size
Findings of Cp Maximum at 233 K for the Water within Silica Nanopores and Very Weak Dependence of the Tmax on the Pore Size
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DOI：
10.1021/jp104970s
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发表时间：
2010-11-11
影响因子：
3.3
通讯作者：
Namba, Seitaro
中科院分区：
文献类型：
--
作者：
Nagoe, Atsushi;Kanke, Yasuhiro;Namba, Seitaro
低温水是如何形成具有某些网络结构的强氢键的，仍然是一个问题。采用绝热量热法测定了不同直径的二氧化硅MCM-41纳米孔内水的热容。他们发现了一个驼峰，其最大值分别为233 K和240 K的普通水和重水。最高温度基本上与孔隙直径无关，而最大值仅与孔隙中内部水分子的比例成正比。结果表明，体积水中的氢键形成过程与纳米孔水中的氢键形成过程基本相同，冷却时相邻水分子排列成四面体位置，但保持其网络结构不规则，形成强氢键，与冰的结构形成鲜明对比。
How low-temperature water develops the formation of strong hydrogen bonds with some network structure is still open to a question. Heat capacities of the water confined within silica MCM-41 nanopores with different diameters in the range 1.7-4.2 nm were measured by adiabatic calorimetry. They revealed a hump with its maximum at 233 and 240 K for ordinary and heavy water, respectively. The maximum temperatures were essentially independent of the pore diameter, whereas the maximum values increased only in proportion to the fraction of the internal water molecules within the pores. It was concluded that the manner in which the hydrogen-bond formation progresses in bulk water is essentially the same as that in nanopore water and that strong hydrogen bonds are formed on cooling by arranging the neighboring water molecules at tetrahedral positions but keeping their network structure irregular to make striking contrast with ice structure.