Montavon G, Hennig C, Janvier P, Grambow B
Laboratoire SUBATECH, 4 rue A. Kastler, BP 20722, 44307 Nantes Cedex 03, France.
J Colloid Interface Sci. 2006 Aug 15;300(2):482-90. doi: 10.1016/j.jcis.2006.04.053. Epub 2006 Apr 25.
The speciation of Eu complexed with polyacrylic acid (PAA) and alumina-bound PAA (PAA(ads)) was studied at pH 5 in 0.1 M NaClO(4). Structural parameters were obtained from (7)F(0) -->(5)D(0) excitation spectra measured by laser-induced fluorescence spectroscopy as well as from Eu L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra. The coordination mode was also investigated by infrared spectroscopy. To elucidate the nature of the complexed species, Eu-acetate complexes were used as references. The spectroscopic techniques show that two carboxylate groups with 2-3 (EuPAA) and 4-5 (EuPAA(ads)) water molecules are coordinated to Eu in the first coordination sphere. For EuPAA(ads), the coordination between carboxylate groups and Eu appears to be bidendate. A similar coordination is probable for EuPAA but the EXAFS data indicate a slightly distorted coordination. The results show that the degree of freedom of carboxylate groups is not the same for free or adsorbed PAA. For PAA, the degree of freedom is constrained by the flexibility of the methylene chain. When PAA is adsorbed on alumina, the polymer chains cannot any more be treated as independent chains. One may rather assume formation of aggregates that form an organic layer at the mineral surface presenting a complex arrangement of carboxylate groups.
研究了铕与聚丙烯酸（PAA）以及氧化铝负载的PAA（PAA(ads)）形成的配合物在pH为5的0.1 M高氯酸钠（NaClO₄）溶液中的物种形成情况。通过激光诱导荧光光谱测量的（⁷F₀）→（⁵D₀）激发光谱以及铕L(III)边扩展X射线吸收精细结构（EXAFS）光谱获得了结构参数。还通过红外光谱研究了配位模式。为了阐明配合物物种的性质，以乙酸铕配合物作为参考。光谱技术表明，在第一配位层中，两个羧基与2 - 3个（EuPAA）和4 - 5个（EuPAA(ads)）水分子与铕配位。对于EuPAA(ads)，羧基与铕之间的配位似乎是双齿的。EuPAA可能也有类似的配位，但EXAFS数据表明配位略有扭曲。结果表明，游离或吸附的PAA中羧基的自由度不同。对于PAA，自由度受亚甲基链柔韧性的限制。当PAA吸附在氧化铝上时，聚合物链不再能被视为独立的链。人们可以假定形成聚集体，这些聚集体在矿物表面形成一个有机层，呈现出羧基的复杂排列。
