Bowyer Walter J, Xu Wenying, Demas J N
Department of Chemistry, Hobart and William Smith Colleges, Geneva, New York 14456, USA.
Anal Chem. 2009 Jan 1;81(1):378-84. doi: 10.1021/ac8016554.
Polymer-supported luminescent metal complexes represent an important class of oxygen, pH, and ion sensors. The diffusion properties of the analyte into the sensing film are important for rational sensor and support design and development. We describe a technique using lifetime measurements in the frequency domain for determining the diffusion coefficient of hydrochloric acid through various polymeric pH sensor films. Two types of polymers are doped with [Ru(4,7-diphenyl-1,10-phenanthroline)2(4,4'-dicarboxy-2,2'-bipyridine)]Cl2. We monitor the phase shift of luminescence (from which we calculate the apparent lifetime, tau(app)) versus time after applying a step increase in the aqueous HCl concentration at the surfaces of the film. We model the decrease in tau(app) as a function of time using the diffusion coefficient of HCl in the polymer as the only adjustable parameter. The model accurately predicts the lifetime versus time curves, and the resulting diffusion coefficients are highly dependent on the polymer. Relative to bulk water, diffusion of protons within very hydrophilic hydrated D4 polymer (a polyethylene oxide cross-linked siloxane ring polymer) films is hindered approximately 4-fold, while within a more hydrophobic sol gel it is hindered by over 1 order of magnitude. The methodology is adaptable for measuring diffusion coefficients of a variety of analytes in different sensor films as long as the bound and unbound forms luminescence and the excited states have different lifetimes.
聚合物负载的发光金属配合物是一类重要的氧、pH值和离子传感器。分析物向传感膜内的扩散特性对于合理设计和开发传感器及其载体至关重要。我们描述了一种利用频域寿命测量来测定盐酸在各种聚合物pH传感器膜中的扩散系数的技术。两种类型的聚合物被掺杂了[Ru(4,7 - 二苯基 - 1,10 - 菲咯啉)2(4,4'-二羧基 - 2,2'-联吡啶)]Cl2。在膜表面的盐酸水溶液浓度阶跃增加后，我们监测发光的相移（由此计算表观寿命，tau(app)）随时间的变化。我们将tau(app)随时间的下降作为函数进行建模，将HCl在聚合物中的扩散系数作为唯一的可调参数。该模型准确地预测了寿命随时间的曲线，并且所得的扩散系数高度依赖于聚合物。相对于大量水，质子在非常亲水的水合D4聚合物（一种聚环氧乙烷交联硅氧烷环聚合物）膜内的扩散受阻约4倍，而在疏水性更强的溶胶 - 凝胶中，扩散受阻超过1个数量级。只要结合态和非结合态发光以及激发态具有不同的寿命，该方法就适用于测量各种分析物在不同传感器膜中的扩散系数。
