One-pot synthesis of gold nanoshells with high photon-to-heat conversion efficiency

A new one-pot method for the preparation of gold nanoshells on amino-functionalized silica nanoparticles is presented together with the determination of their heat release efficiency. The synthesis of silica nuclei and the growth of a thin gold capping layer was done in the same pot; upon controlling the experimental conditions, it was possible to keep the final diameter of the hybrid nanoparticles below 30 nm, with a gold layer of 6 nm. Photoacoustic measurements carried out on gold nanoshell suspensions demonstrate that heat release occurs with an efficiency close to unity, regardless of the chemical nature of the stabilizer on the gold surface. The effectiveness of gold nanoshells in converting photons into heat has been tested by inducing thermal denaturation of nanoshell-coupled EGFP (enhanced green fluorescent protein). These measurements indicate that the thermal effects detected in gold nanostructures are long-range phenomena, which are potentially useful in photothermal treatments, but should be taken into account when designing gold-based devices or using gold surfaces to enhance optical signals. © 2009 American Chemical Society.