Large Scale Synthesis of Near-Monodisperse Gold Nanorods and their Assembly into 3D Anisotropic Single Crystals Eugene R. Zubarev, William Marsh Rice University, DMR Funding from the SSMC program allowed us to develop the synthesis and functionalization of well-defined gold nanorods that are completely nontoxic and therefore suitable for biomedical applications of these nanostructures. We were able to demonstrate that a quantitative replacement of conventional CTAB coating with a thiolated cationic surfactant leads to high stability of nanorods in pure water and much higher cellular uptake of these particles. Breast cancer cells treated with these nanorods retain their ability to proliferate even after 2 million nanorods enter their interior. This new nanomaterial opens up new avenues for more efficient photothermal treatment of cancer and optical imaging of tumors. (Angew. Chem. Int. Ed. 2012, 51, ). In a parallel study, we developed a synthesis of novel nanostructures whose shape resembles a starfruit. Fast reductive deposition of gold on the surface of pre-formed gold nanorods results in anisotropic overgrowth and the formation of extremely rough surface. The initial pentagonal cross- section of the nanorods transforms into a star-like object due to a difference in the rate of gold deposition on the sides and edges of the nanorods. These novel structures were found to be particularly effective in detecting the presence of organic molecules by surface enhanced Raman spectroscopy (SERS). The rough surface was shown to be beneficial in comparison with smooth surface of analogous nanorods and the enhancement factor was found to be at least 25 times greater for the startfruit-like particles. (Langmuir 2012, 28, ). A B

Large Scale Synthesis of Near-Monodisperse Gold Nanorods and their Assembly into 3D Anisotropic Single Crystals Eugene R. Zubarev, William Marsh Rice University, DMR Broader Impacts: The nanostructures developed in this project may have an immediate impact in the area of biomedical applications. Due to their unique ability to transform infrared light into heat, gold nanorods can be used effectively for killing cancer cells upon irradiation with near-infrared light, which is otherwise harmless to biological tissue. This concept has been realized and attempted with many different gold nanostructures, but there were several technical challenges associate with conventional nanomaterials. Many of them are not sufficiently stable in aqueous solution and therefore cannot be administered intravenously. Other metallic particles which have a fairly long blood circulation time often have a poor cellular uptake, such as pegylated nanostructures (picogram quantities per cell). This small weight fraction may explain a somewhat limited success to date of photothermal oblation of tumor cells, which is strongly dependent on the actual number of nanorods present inside the cells. Therefore, these newly developed structures can help biomedical researchers to overcome many existing limitations of photo-thermal therapy of cancer. A B Figure 2. Bright field optical microscopy image of a breast cancer cell treated with gold nanorods. Up to 2 million nanorods can enter each cancer cell and generate a large amount of heat during laser irradiation. The use of thiolated cationic molecules shown in front is critical for solution stability and low toxicity of the nanorods developed in this project.