Molecular Dynamics Analysis of NaOH Aqueous Solution Surface and the Sum Frequency Generation Spectra: Is Surface OH鈥?/sup> Detected by SFG Spectroscopy?

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• 作者：Takako Imamura ; Tatsuya Ishiyama ; Akihiro Morita
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：December 18, 2014
• 年：2014
• 卷：118
• 期：50
• 页码：29017-29027
• 全文大小：477K
• ISSN：1932-7455

文摘

We elucidated the phase-sensitive sum frequency generation (SFG) spectrum of NaOH aqueous solution by molecular dynamics simulation. The MD analysis reproduced the effects of NaOH on the imaginary 蠂⁽²⁾ spectrum, characterized with a positive (upward) shift in the amplitude in midfrequency region (3300鈥?600 cm^鈥?) and a negative (downward) shift in low frequency (3000鈥?200 cm^鈥?). We found that the positive shift is a consequence of electric double layers, while the negative shift is attributed to the first solvation shell of OH^{鈥?/sup>. The latter mechanism generally holds for electrolyte solutions, though it becomes conspicuous for the NaOH solution in the low-frequency tail region. These perturbation mechanisms evidence that OH鈥?/sup> at the surface is fully hydrated and not preferentially exposed to the surface.}