Structure of water layers at hydrophilic surfaces

Near strongly attractive surfaces, liquid structure differs noticeably from the bulk one. This is caused by the packing effect due to the localization of molecules in a plane(s) parallel to the wall and by specific fluid-wall interactions, such as H-bonds. Density oscillations of liquids near solid substrates were observed in experiments [143, 144, 417-419] and in numerous computer simulations of confined fluids. Besides, fluids with strongly anisotropic interactions (such as water) unavoidably undergo orientational ordering near the wall. It is important to know the character of this ordering and its intrusion into the bulk liquid. In the present section, we consider structural properties of adsorbed water layers in the liquid, bilayer, and monolayer phases. 

Numerous simulation studies of liquid water near various smooth and structured surfaces were reported (see Refs. [28, 32, 206] for more details). Near the surface, water molecules show orientational 

Density profiles of liquid water, which coexists with a vapor at T = 300 K near surfaces of various hydrophobicity/hydrophilicity, are shown in Fig. 79. In the case of a strongly hydrophobic surface 

Ordering of water within the surface layer can be characterized by the in-plane pair correlation functions go-o( ) between the water oxygens in this layer only. In a bulk liquid, there are three main maxima of go-o( ) maximum at about 2.75 A corresponds to the H-bonded neighbors in the first coordination shell maxima at about 4.5 A and 6.8 A reflect tetrahedral arrangement of neighbors in the second and third coordination shells (see lower curve in Fig. 83). Additional maximum of go-o( ) appears in 

Near strongly hydrophilic surfaces, water structures in the two surface layers are not very sensitive to the presence of bulk liquid water. In-plane pair correlation functions go-o(r) between the water oxygens in the first surface layer are shown in Fig. 84. When the first adsorbed water layer is covered by the second and subsequent water layers, its structure practically remains the same. Second water layer also shows maximum of go-o(r) at about 5.5 A when only two water layers are adsorbed at the 

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