The retention, release, and detection of metallic complexes in polymeric hydrogels are of interest in drug delivery, analytical chemistry, and water remediation. The electrochemistry of the redox complexes inside the hydrogel could be affected by the viscoelastic properties of the gel, local ionic force and pH, and interactions (e.g., hydrophobic) between the complex and the polymer chains. In this work, it is shown that a simple setup, consisting of a disk electrode pressed on the hydrogel, allows to perform electrochemistry of a redox couple: Tris(1,10-phenanthroline)iron(II) (Fe(phen)₃ ²⁺) inside a hydrogel matrix. The behavior is compared with the same couple in solution, and it is found that the electrochemical properties of the redox couple are strongly affected by the presence of the hydrogel matrix. The cyclic voltammogram of the hydrogel loaded with complex shows a response, which suggests electrochemical-chemical mechanism. The chemical step is likely linked to a catalytic oxidation of free hydrated Fe²⁺ ions present inside the hydrogel together with the redox complex. Since Fe²⁺ ions have small charge transfer constants on the glassy carbon electrodes, only the catalytic current is observed. Indeed, when excess ligand (phenanthroline) is absorbed inside the hydrogel, the measured cyclic voltammograms show a single reversible oxidation/reduction step. It seems that the complexation equilibrium shifts toward the complex, making the free iron concentration negligible. Accordingly, the cyclic voltammetry shape and peak potential difference agree with a reversible oxidation/reduction. Additionally, the peak currents of the cyclic voltammograms show a linear dependence with the square root of time, as predicted by a Randles-Sevcik equation. However, the measured currents are smaller than the simulated ones. The differences are in agreement with simulations of the cyclic voltammograms where the migration of the redox species is considered. Chronoamperometry is used to measure the mass transport of redox species inside the hydrogel. It is found that the current transients still obey Cottrell’s equation, but the diffusion coefficients obtained from the slopes of Cottrell’s plots have to be corrected for migration effects. The effective diffusion coefficient of Fe(phen)₃ ²⁺ measured inside the hydrogel (D _Red-hydrogel = 5.5 (±0.5) × 10⁻⁸ cm² s⁻¹) is ca. 80 times smaller than the one measured in solution (D _Red-solution = 4.4 (±0.5) × 10⁻⁶ cm² s⁻¹). The simple setup has a true semi-infinite boundary condition, which allows characterizing the hydrogel in the same condition as the bulk material and easily changing both the redox species and the hydrogel structure.

聚合物水凝胶中金属络合物的保留，释放和检测在药物输送，分析化学和水修复方面具有重要意义。水凝胶内部氧化还原络合物的电化学可能会受到凝胶的粘弹性，局部离子力和pH以及络合物与聚合物链之间的相互作用（例如疏水性）的影响。在这项工作中，表明了一个简单的装置，该装置由一个压在水凝胶上的圆盘电极组成，可以执行氧化还原对的电化学反应：Tris（1,10-phenothroline）iron（II）（Fe（phen）₃ ^{2 +}）在水凝胶基质中。将其行为与溶液中的相同偶对进行了比较，发现水凝胶基质的存在强烈影响氧化还原偶对的电化学性质。负载复合物的水凝胶的循环伏安图显示了响应，这表明了电化学-化学机理。该化学步骤很可能与存在于水凝胶中的氧化铁配合物的游离水合Fe ²⁺离子的催化氧化有关。由于Fe ²⁺离子在玻璃碳电极上的电荷转移常数较小，仅观察到催化电流。实际上，当过量的配体（菲咯啉）被吸收到水凝胶中时，测得的循环伏安图显示出一个可逆的氧化/还原步骤。看来络合平衡向络合物移动，使游离铁浓度可忽略不计。因此，循环伏安法的形状和峰电位差与可逆的氧化/还原相一致。此外，循环伏安图的峰值电流与时间的平方根呈线性关系，如Randles-Sevcik方程所预测。但是，实测电流小于模拟电流。差异与考虑了氧化还原物质迁移的循环伏安图的模拟一致。计时安培法用于测量水凝胶内部氧化还原物质的质量传递。已经发现，当前的瞬变仍然服从于Cottrell方程，但是从Cottrell曲线的斜率获得的扩散系数必须针对迁移效应进行校正。Fe（phen）的有效扩散系数 在水凝胶内部测得的₃ ²⁺（D _{Red-水凝胶} = 5.5（±0.5）×10 ^-8  cm ²  s ^-1）为ca。比溶液中测得的溶液小80倍（D _红色溶液 = 4.4（±0.5）×10 ^-6  cm ²  s ^-1）。简单的设置具有真正的半无限边界条件，可以在与块状材料相同的条件下表征水凝胶，并轻松改变氧化还原物种和水凝胶结构。