Surface Charge Density Determination in Water Based Magnetic Colloids: a Comparative Study

This work focuses on the systematic investigation of the two well-established methods of structural surface charge density determination on magnetic colloids, labeled as Single Potentiometric Method (SPM) and Potentiometric-Conductometric Method (PCM). To compare some important features of the methods we determined the structural surface charge density of magnetic colloids samples based on CoFe2O4@ɣ-Fe2O3 core-shell nanoparticles with three different mean sizes using both strategies. Concerning quickness, easiness and cost, the PCM has proved to be more advantageous than the SPM. Regarding the effectiveness, both methods were consistent in determining the saturation value of the structural charge, but the SPM was more accurate to describe the pH-dependence of the concentration of the charged surface sites. Considering the chemical safety, the methods are equivalent. Finally, both the SPM and PCM are reproducible and can be effectively applied to determine the saturation value of the surface charge density on magnetic colloids.本研究针对磁性胶体的结构表面电荷密度测定的两种成熟方法展开系统性探究，这两种方法分别被命名为单电位法（Single Potentiometric Method，SPM）与电位-电导联用法（Potentiometric-Conductometric Method，PCM）。为对比这两种方法的关键特性，本研究采用两种策略，对基于三种不同平均尺寸的CoFe2O4@ɣ-Fe2O3核壳纳米粒子制备的磁性胶体样品的结构表面电荷密度进行了测定。在便捷性、操作易用性与成本方面，电位-电导联用法已被证实优于单电位法。就测定有效性而言，两种方法在确定结构电荷饱和值时结果一致，但单电位法在描述带电表面位点浓度的pH依赖性方面更为精准。在化学安全性层面，两种方法表现相当。最终，单电位法与电位-电导联用法均具备良好的可重复性，均可有效用于测定磁性胶体的表面电荷密度饱和值。