Fachbereich Physik, Philipps Universität Marburg, Marburg, Germany.
Chemphyschem. 2010 Feb 22;11(3):730-5. doi: 10.1002/cphc.200900849.
Ion sensors based on colloidal nanoparticles (NPs), either as actively ion-sensing NPs or as nanoscale carrier systems for organic ion-sensing fluorescent chelators typically require a charged surface in order to be colloidally stable. We demonstrate that this surface charge significantly impacts the ion binding and affects the read-out. Sensor read-out should be thus not determined by the bulk ion concentration, but by the local ion concentration in the nano-environment of the NP surface. We present a conclusive model corroborated by experimental data that reproduces the strong distance-dependence of the effect. The experimental data are based on the capability of tuning the distance of a pH-sensitive fluorophore to the surface of NPs in the nanometer (nm) range. This in turn allows for modification of the effective acid dissociation constant value (its logarithmic form, pK(a)) of analyte-sensitive fluorophores by tuning their distance to the underlying colloidal NPs.
基于胶态纳米粒子 (NPs) 的离子传感器，无论是作为主动离子感应 NPs 还是作为有机离子感应荧光螯合剂的纳米级载体系统，通常需要带电荷的表面才能实现胶体稳定。我们证明，这种表面电荷会显著影响离子结合并影响读出。因此，传感器的读出不应取决于离子的总体浓度，而应取决于 NP 表面纳米环境中的局部离子浓度。我们提出了一个结论性的模型，该模型得到了实验数据的证实，可以再现这种强烈的距离依赖性效应。实验数据基于在纳米 (nm) 范围内调整 pH 敏感荧光团与 NPs 表面之间距离的能力。这反过来又可以通过调整它们与下面的胶体 NPs 的距离来修饰分析物敏感荧光团的有效酸离解常数值 (其对数形式，pK(a))。
