外球表面配合物的振动特性：硫酸盐离子吸附在金属（水合）氧化物上的实例。

Vibrational characteristics of outer-sphere surface complexes: example of sulfate ions adsorbed onto metal (hydr)oxides.

机构信息

LECIME-UMR7575, CNRS-ENSCP, 11 Rue Pierre et Marie Curie, 75231 Paris, Cedex 05, France.

出版信息

Langmuir. 2011 Jun 7;27(11):6830-5. doi: 10.1021/la200514z. Epub 2011 May 6.

DOI:10.1021/la200514z

Abstract

The vibrational characteristics of outer-sphere complexes of sulfate at several mineral oxide-water interfaces were investigated by in situ attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. In the IR spectra obtained from surface outer-sphere complexes, only one peak of the asymmetric stretching vibrational mode υ(3) similar to that of free sulfate ion SO(4)(2-) in aqueous solution is observed. However, on the investigated (hydr)oxide surfaces of Al(3+), Ti(4+), Fe(2+/3+), Cr(3+), Ce(4+), Cu(2+), Y(3+), Zn(2+), and Nd(3+), a shift of up to 14 cm(-1) was found, which was correlated to the polarizing power of the metal cations. A high polarizing power was found to result in a stronger shift of υ(3) compared to that of the aqueous SO(4)(2-) ion. Furthermore, the impact of the metal oxide structure on the characteristics of the formed outer-sphere complex was negligible because different Al and Fe (hydr)oxides did not show any changes in the respective IR spectra. Finally, the ionic strength (1-10(-4) M) and pH (6.8-3.1) have been modified to change the surface potential, showing no direct influence on the spectra (i.e., on the geometry of the outer-sphere complex).

摘要

采用原位衰减全反射傅里叶变换红外光谱（ATR FT-IR）技术研究了硫酸盐在几种矿氧化物-水界面的外层配合物的振动特性。在从表面外层配合物获得的红外光谱中，仅观察到类似于水溶液中游离硫酸盐离子 SO(4)(2-)的不对称伸缩振动模式 υ(3)的一个峰。然而，在所研究的 Al(3+)、Ti(4+)、Fe(2+/3+)、Cr(3+)、Ce(4+)、Cu(2+)、Y(3+)、Zn(2+)和 Nd(3+)的（水合）氧化物表面上，发现 υ(3)发生了高达 14 cm(-1)的位移，这与金属阳离子的极化能力有关。发现高极化能力导致 υ(3)的位移比水溶液中的 SO(4)(2-)离子更强。此外，金属氧化物结构对形成的外层配合物的特性的影响可以忽略不计，因为不同的 Al 和 Fe（水合）氧化物在各自的红外光谱中没有显示出任何变化。最后，改变离子强度（1-10(-4) M）和 pH 值（6.8-3.1）以改变表面电位，这对光谱（即外层配合物的几何形状）没有直接影响。