New Insight into the Chemical Nature of the Plasmonic Nanostructures Synthesized by Reduction of Au(III) with Sulfide Species

MARÍA ANA HUERGO; CHRISTOPH MAIER; CAROLINA VERICAT; M. SERGIO MORENO; M. SERGIO MORENO; ROBERTO SALVAREZZA; ROBERTO SALVAREZZA; LISANDRO GIOVANETTI; FÉLIX REQUEJO; LISANDRO GIOVANETTI; FÉLIX REQUEJO; MARÍA ANA HUERGO; CHRISTOPH MAIER; CAROLINA VERICAT

LANGMUIR

AMER CHEMICAL SOC

Año: 2017 vol. 33 p. 6785 - 6793

0743-7463

We have studied the products of the controversial synthesis of HAuCl4 with Na2S, which include gold nanostructures (Au NSs) that absorb in the near-infrared (NIR) and are highly promising for photothermal therapies and other nanomedical applications. From high resolution transmission electron microscopy, X-ray absorption spectroscopy and small angle X-ray scattering we have found that only metallic gold nanostructures are formed as a result of this synthesis, with no detectable amount of gold sulfide or other oxidized gold species that could account for the NIR absorption. Different sulfur species are adsorbed on the Au NSs, mainly sulfides (monomeric sulfur) and polysulfides, similarly to what is found on planar gold surfaces, therefore precluding the idea that thiosulfate or other oxidized species are the actual reducing agents for Au(III) ions. The presence of strongly adsorbed S species, which are difficult to remove from the gold surface, is of great importance for their applications as regards toxicity and the use of post-functionalization strategies to anchor biomolecules and/or to increase circulation time after administration.