Negligible absorption of radiofrequency radiation by colloidal gold nanoparticles

We report quantitative measurement of heat generation in Au-nanoparticle colloidal solutions induced by radiofrequency (RF) electromagnetic waves (13.56 MHz; 25 W). The possible role of Au nanoparticles in RF heating was systematically investigated by separating the metal nanoparticles away from the colloidal solutions by centrifugation. Contrary to the previously made assumption in this field, it is found that Au nanoparticles do not contribute to RF energy absorption. The electrical conductivity measurement of the solutions with and without Au nanoparticles reveals that the Joule heating via ionic conduction in the electrolyte solutions is the dominant mechanism of RF-radiation-to-thermal conversion.

Graphical abstractThe radiofrequency heating of gold nanoparticle colloidal solutions is found to be due to the Joule heating of ionic solution, not due to RF energy absorption of gold nanoparticles.Figure optionsDownload full-size imageDownload high-quality image (81 K)Download as PowerPoint slideHighlights► Gold nanoparticles were physically separated from the Au-NP colloidal solutions by centrifugation. ► RF heating and electrical conductivity measurements were performed. ► RF heating of colloidal solutions is caused by ionic conduction Joule heating of background solution. ► Au nanoparticles do not contribute to RF energy absorption.