Islam Gazi Jahirul, Arrigan Damien W M
School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia; Department of Chemistry, University of Barishal, Barishal, 8254, Bangladesh.
School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
Talanta. 2024 Dec 1;280:126598. doi: 10.1016/j.talanta.2024.126598. Epub 2024 Jul 20.
Dendrimers are macromolecules with well-defined three-dimensional structures, sizes and surface charges. In this work, four generations of poly(amidoamine) (PAMAM) dendrimers were investigated at the micro-interface between two immiscible electrolyte solutions (μITIES) to understand their electrochemical responses as simple models of ionised macromolecules. Cyclic voltammetry (CV) across a range of aqueous phase pH revealed that all four generations (G0-G3) presented diffusion-controlled ion-transfer from aqueous to organic phase, while the reverse transfers from organic to aqueous phase varied with both pH and the dendrimer generation. The larger dendrimers (G2 and G3) show an adsorption behaviour at pH ≤ 3.5, but show a diffusional response at pH ≥ 6. On the other hand, the smaller dendrimers (G0 and G1) always show a diffusional response and are not impacted by the pH. This indicates that more highly charged dendrimers condense at the interface. The reverse scan of CVs showed that an increased applied potential was required to remove (desorb) these polycations from the interfaces in comparison to smaller, less charged species. Diffusion coefficients (D) were estimated, showing a decrease with increasing generation. Limits of detection for these dendrimers by CV at the μITIES were 0.4, 0.2, 0.7 and 0.5 μM for G0 to G3, respectively, while differential pulse voltammetry lowered the LODs (0.07, 0.05, 0.09 and 0.08 μM, respectively). These study shows that the μITIES provides a simple way to detect and evaluate the electrochemical behaviour of ionised macromolecules, providing a simple illustration of detection mechanism with diffusion or adsorption processes.
树枝状大分子是具有明确三维结构、尺寸和表面电荷的大分子。在这项工作中，研究了四代聚（酰胺胺）（PAMAM）树枝状大分子在两种不混溶电解质溶液的微界面（μITIES）处的情况，以了解它们作为离子化大分子的简单模型的电化学响应。在一系列水相pH值范围内进行的循环伏安法（CV）表明，所有四代（G0 - G3）均呈现从水相到有机相的扩散控制离子转移，而从有机相到水相的反向转移则随pH值和树枝状大分子的代数而变化。较大的树枝状大分子（G2和G3）在pH≤3.5时表现出吸附行为，但在pH≥6时表现出扩散响应。另一方面，较小的树枝状大分子（G0和G1）总是表现出扩散响应，且不受pH值影响。这表明电荷更高的树枝状大分子在界面处凝聚。CV的反向扫描表明，与较小、电荷较少的物种相比，需要增加施加电位才能从界面去除（解吸）这些聚阳离子。估计了扩散系数（D），结果表明其随代数增加而降低。通过CV在μITIES处对这些树枝状大分子的检测限，G0至G3分别为0.4、0.2、0.7和0.5μM，而差分脉冲伏安法降低了检测限（分别为0.07、0.05、0.09和0.08μM）。这项研究表明，μITIES提供了一种检测和评估离子化大分子电化学行为的简单方法，并通过扩散或吸附过程对检测机制进行了简单说明。
