Weiß Lennart J K, Nikić Marta, Simmel Friedrich C, Wolfrum Bernhard
Physics of Synthetic Biological Systems (E14), Department of Bioscience, School of Natural Sciences, Technical University of Munich, 80333, München, Germany.
Neuroelectronics, Munich Institute of Biomedical Engineering, School of Computation, Information and Technology, Technical University of Munich, 80333, München, Germany.
Small. 2025 Apr;21(16):e2410306. doi: 10.1002/smll.202410306. Epub 2025 Mar 13.
This study uses single-impact experiments to explore how the nanoparticles' surface chemistry influences their redox activity. 20 and 40 nm-sized silver nanoparticles are functionalized with alkanethiol ligands of various chain lengths (n = 3, 6, 8, and 11) and moieties (carboxyl ─COOH / hydroxyl ─OH), and the critical role of the particle shell is systematically examined. Short COOH-terminated ligands enable efficient charge transfer, resulting in higher impact rates and fast, high-amplitude transients. Even elevated potentials fail to overcome tunneling barriers for ligand lengths of n ≥ 6 and risk oxidizing the electrode, forming an insulating layer. Electrostatic interactions play a key role in governing reaction dynamics. In general, particles with a COOH-group exhibit higher impact rates and current amplitudes in KCl than those with an OH-group. This effect is more pronounced for 40 nm-sized particles; although, they rarely oxidize completely. The influence of electrolyte composition-concentration, pH, and a biologically relevant electrolyte-reveals that its impact on the redox activity can be as critical as that of the particle shell, with both determining particle adsorption and electron tunneling. These findings provide insights into the complex interdependencies at the electrode-particle-electrolyte interface, aiding the design of custom redox-active (silver) nanoparticles for ultrasensitive electrochemical sensing.
本研究采用单冲击实验来探究纳米颗粒的表面化学如何影响其氧化还原活性。20纳米和40纳米大小的银纳米颗粒用不同链长（n = 3、6、8和11）以及不同部分（羧基─COOH / 羟基─OH）的烷硫醇配体进行功能化处理，并系统地研究了颗粒外壳的关键作用。短的COOH端基配体能够实现高效的电荷转移，从而产生更高的冲击速率以及快速、高幅度的瞬态。对于n≥6的配体长度，即使是升高的电位也无法克服隧穿势垒，并且存在氧化电极的风险，从而形成绝缘层。静电相互作用在控制反应动力学方面起着关键作用。一般来说，带有COOH基团的颗粒在KCl中比带有OH基团的颗粒表现出更高的冲击速率和电流幅度。这种效应在40纳米大小的颗粒中更为明显；不过，它们很少会完全氧化。电解质组成（浓度、pH值）以及一种具有生物相关性的电解质的影响表明，其对氧化还原活性的影响与颗粒外壳的影响同样关键，二者共同决定颗粒的吸附和电子隧穿。这些发现为电极 - 颗粒 - 电解质界面处复杂的相互依存关系提供了见解，有助于设计用于超灵敏电化学传感的定制氧化还原活性（银）纳米颗粒。
