A Contactless Method for Measuring the Redox Potentials of Metal Nanoparticles

The standard redox potentials of metal nanoparticles are important for understanding their chemical properties. Traditionally, these redox potentials are measured by using voltammetry. Although voltammetry is fast and cost-effective, loading or landing the nanoparticles on electrodes alters their electrochemical properties, posing a challenge for accurately determining their intrinsic redox potentials. Here, a contactless method was developed utilizing chemical assays and the Nernst equation to measure the standard reduction potentials of gold nanoparticles in their colloidal state. To showcase the versatility and accuracy of this Nernstian approach, the reduction potentials were measured for a size range of 5.0-73 nm, revealing their scaling law and dependence on the nanoparticle surface energy.