Tuning the electrical properties of colloidal nanoalloys by varying their composition

Colloidal nanoalloys have been shown to have combined advantageous properties of their metallic constituents. However, the research on the electrical properties of colloidal nanoalloys is still lacking. We report an electrical properties study of gold-silver nanoalloys of various compositions suspended in Milli-Q water using impedance spectroscopy. We model the impedance spectra with an equivalent electrical circuit that consists of a constant phase element (CPE) in series with a parallel of a resistor and a capacitor. Through this model, we can extract information about the conductivity, relative permittivity, and electrode/solution interface properties of the colloidal nanoalloys. We have found that the conductivity and relative permittivity increase almost linearly with the increase of gold molar fraction in the solution. This means that the electrical properties of colloidal nanoalloys can be easily tuned by varying their composition. A possible direct application of these findings is for tailoring nanoparticles as contrast agents in applications such as electrical impedance tomography.