Unravelling electrochemical transformations of individual silver nanoparticles by hyperspectral dark-field microscopy

Kristina Tschulik, Ruhr University Bochum, Bochum, Germany
Kevin Wonner, Ruhr University Bochum, Bochum, Germany
Mathies V. Evers, Ruhr University Bochum, Bochum, Germany

Albeit silver nanoparticles are frequently used in industries, consumer products and medicine, their reactivity, degradation mechanism and stability are poorly understood. Those particles are now found more often in nature, water bodies and living things. Thus, there is an increase demand to enhance the analytical methods to detect and characterize those particles in a reliable, fast and cheap way. The electrochemical conversion of Ag nanoparticles is a well-studied method to study these properties. Nevertheless, electrochemical techniques are limited and therefore, some reactions and conversion process at the nanoscale are not fully understood today. Hence, similar experiments by different research groups, show different results and cause controverse debates occasionally. In this work simultaneous in situ opto- and spectro-electrochemical dark-field microscopy studies of silver nanoparticles are realized for the first time in a newly designed transparent electrochemical cell with optical and hyperspectral imaging. The electrochemical nanoparticleocidation is performed in different electrolyte solutions, thus changing the reaction mechanism of the particles and following the transition simultanously. Full dissolution was obtained for silver in potassium thiocyanate solutions and for gold in aqueous hydrochloric acid. Furthermore, even particle composition changes were visualized by monitoring their individul spectral response during electrochemical potential cycles.

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