Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 36 Bratislava, Slovak Republic.
J Colloid Interface Sci. 2011 May 15;357(2):322-30. doi: 10.1016/j.jcis.2011.01.069. Epub 2011 Jan 25.
Montmorillonite monoionic forms with alkali metal and NH(4)(+)-cations were prepared by ion exchange. The hydration properties and binding of the ions to montmorillonite surface and the swelling properties of the mineral specimens were analyzed. Whereas Na(+)- and Li(+)-ions were fully hydrated over a large range of conditions, large size K(+), NH(4)(+), and mainly Rb(+) and Cs(+) ions were apt to bind directly to the oxygen atoms on the mineral surface. The forms with large ions exhibited reduced hydration and swelling and the absence of macroscopic swelling of the respective aqueous colloids. The interaction of laser dye rhodamine 6G (R6G) in montmorillonite colloids was investigated by absorption and steady-state fluorescence spectroscopies. Significant effects of the properties of both the inorganic ions and swelling properties of colloidal dispersions on R6G molecular aggregation were observed. Large amounts of the molecular aggregates were formed in the colloids of Na(+)- and Li(+)-montmorillonites. The aggregates absorbed light at significantly lower wavelengths (~460 nm) with respect to the light absorption by monomers (535 nm). Fluorescence spectroscopy provided a key evidence for the assignment of the type of the aggregates: The emission of the aggregates at relatively low energies proved these assemblies are rather a mixed H-/J-type than ideal H-aggregates. The presence of parent inorganic cations of larger size led to a significant lowering of the amount of the R6G aggregates in favor of the monomers. Investigations of the evolution of the dye aggregation with time indicated basic features of dye aggregation reaction: The size of parent inorganic ions did not affect the reaction mechanism, but rather limited the extent of the reaction. Probably the forms with large inorganic ions, such as Rb(+) and Cs(+), did not provide sufficient surface for the formation of the large size assemblies of the dye. This property can be explained in terms of strong association of the large alkali metal ions to clay mineral surface, as well as to reduced swelling in the colloidal systems of respective forms.
蒙脱土单离子形式与碱金属和 NH(4)(+) - 阳离子通过离子交换制备。分析了离子对蒙脱土表面的水合性质和结合以及矿物标本的膨胀性质。虽然 Na(+) - 和 Li(+) - 离子在很大的条件范围内完全水合，但大尺寸的 K(+)、NH(4)(+)，主要是 Rb(+) 和 Cs(+) 离子易于直接与矿物表面的氧原子结合。具有大离子的形式表现出较低的水合作用和膨胀作用，并且各自的水胶体没有宏观膨胀。通过吸收和稳态荧光光谱研究了激光染料罗丹明 6G（R6G）在蒙脱土胶体中的相互作用。观察到无机离子的性质和胶体分散体的膨胀性质对 R6G 分子聚集的显著影响。在 Na(+) - 和 Li(+) - 蒙脱土胶体中形成了大量的分子聚集体。聚集体在比单体（535nm）更低的波长（~460nm）处吸收光。荧光光谱学为聚集体类型的分配提供了关键证据：聚集体的发射在相对较低的能量证明这些组装体是混合的 H-/J-型而不是理想的 H-聚集体。较大尺寸的母体无机阳离子的存在导致 R6G 聚集体的量显著降低，有利于单体。随着时间的推移研究染料聚集的演变表明了染料聚集反应的基本特征：母体无机离子的大小不影响反应机制，而是限制了反应的程度。可能具有较大无机离子的形式，如 Rb(+) 和 Cs(+)，没有为形成染料的大尺寸组装体提供足够的表面。这种性质可以用大的碱金属离子强烈结合到粘土矿物表面以及各自形式的胶体体系中膨胀性降低来解释。
