Water Structure at the Buried Silica/Aqueous Interface Studied by Heterodyne-Detected Vibrational Sum-Frequency Generation
Water Structure at the Buried Silica/Aqueous Interface Studied by Heterodyne-Detected Vibrational Sum-Frequency Generation
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DOI：
10.1021/acs.jpcc.6b03275
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发表时间：
2016-05-05
影响因子：
3.7
通讯作者：
Tahara, Tahei
中科院分区：
文献类型：
--
作者：
Myalitsin, Anton;Urashirna, Shu-hei;Tahara, Tahei
利用多路外差振动和频率产生谱仪测量了埋藏二氧化硅/同位素稀释水（HOD-D2O）界面的络合物chi（(2)）光谱，以阐明不同ph值下二氧化硅/水界面上水的氢键结构和上下取向。数据表明，振动耦合（分子间和/或分子内耦合）在确定二氧化硅/水界面的chi(2))光谱特征中起着重要作用，并表明H2O光谱中的双重态特征并不代表二氧化硅/水界面的两种不同的水结构（即冰状结构和液体状结构）。虚chi（(2)）光谱的pH依赖性可以解释为：(1)h -向上取向的水向硅烷酸酯的氧原子提供氢键，同时伴随着由硅烷酸酯负电荷产生的电场取向的h -向上取向的水，(2)h -向上取向的水向中性硅烷醇氧提供氢键，(3)h -向下取向的水接受中性硅烷醇的氢键并向体积水分子提供氢键。HOD-D2O的OH延伸带的宽连续体和低频区的长尾代表了二氧化硅/水界面上强氢键的广泛分布，特别是在低pH下。
Complex chi((2)) spectra of buried silica/isotopically diluted water (HOD-D2O) interfaces were measured using multiplex heterodyne-detected vibrational sum frequency generation spectroscopy to elucidate the hydrogen bond structure and up/down orientation of water at the silica/water interface at different pHs. The data show that-vibrational coupling (inter- and/or intrarnolecular coupling) plays a significant role in determining the chi((2)) spectral feature of silica/H2O interfaces and indicate that the doublet feature in the H2O spectra does not represent two distinct water structures (i.e., the ice and liquid-like structures) at the silica/water interface. The observed pH dependence of the imaginary chi((2)) spectra is explained by (1) H-up oriented water donating a hydrogen bond to the oxygen atom of silanolate, which is accompanied by H-up water oriented by the electric field created by the negative charge of silanolate, (2) H-up oriented water which donates a hydrogen bond to the neutral silanol oxygen, and (3) H-down oriented water which accepts hydrogen bonds from the neutral silanol and donates hydrogen bonds to bulk water molecules. The broad continuum of the OH stretch band of HOD-D2O and a long tail in the low frequency region represent a wide distribution of strong hydrogen bonds at the silica/water interface, particularly at the low pH.