Laboratory of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Department of Inorganic and Analytical Chemistry, University of Geneva, CH-1205 Geneva, Switzerland.
J Colloid Interface Sci. 2014 Feb 15;416:190-7. doi: 10.1016/j.jcis.2013.10.049. Epub 2013 Nov 13.
The interaction of the cationic dye methylene blue (MB) with titanate nanowires (TiONWs) was investigated in different pH environments using visible spectroscopy and electrophoresis on thin films as well as in aqueous suspension. The surface charge of the TiONWs depends on the pH and ionic strength leading to positive charge under acidic and negative under alkaline conditions. The TiONWs have the same adsorption capacity on films and in suspensions at neutral pH while under alkaline conditions they are able to adsorb significantly more MB in suspension due to their higher surface area. Detailed adsorption studies in water revealed that dye cations form monomers, dimers and larger aggregates of H-type (face-to-face) on the TiONW films. The results indicate that below pH = 4.0 the TiONWs' external surface consists of Brøntsted acid sites capable of protonating MB. It was suggested that reversible indicator role of MB molecule dimers probes the TiONW surface acidity (Brøntsted sites).
采用可见光谱法、薄膜电泳和水悬浮液电泳研究了在不同 pH 环境下，阳离子染料亚甲蓝（MB）与钛酸盐纳米线（TiONWs）的相互作用。TiONWs 的表面电荷取决于 pH 值和离子强度，在酸性条件下带正电荷，在碱性条件下带负电荷。TiONWs 在中性 pH 值下在薄膜和悬浮液中具有相同的吸附能力，而在碱性条件下，由于其表面积更大，它们能够在悬浮液中吸附更多的 MB。在水中的详细吸附研究表明，染料阳离子在 TiONW 薄膜上形成单体、二聚体和更大的 H 型（面对面）聚集体。结果表明，在 pH 值低于 4.0 时，TiONWs 的外表面由能够质子化 MB 的 Brøntsted 酸位组成。有人提出，MB 分子二聚体的可逆指示剂作用探测了 TiONW 表面酸度（Brøntsted 位）。
