High-Yield Synthesis of Gold Nanorods with Longitudinal SPR Peak Greater than 1200 nm Using Hydroquinone as a Reducing Agent

While gold nanorods have been extensively studied and used in many biological, plasmonics, and sensing applications, their conventional seed-mediated synthesis still presents a number of limitations. Its high sensitivity to the concentration of the reducing agent (ascorbic acid) leads to problems with reliability as well as extremely poor yield of ionic-to-metallic gold conversion, which is only ∼15%. In addition, the synthesis of high purity nanorods with longitudinal surface plasmon resonance (LSPR) peak higher than 1000 nm is particularly difficult utilizing this technique. This report demonstrates the use of hydroquinone for the synthesis of gold nanorods which addresses these two major limitations. By replacing ascorbic acid with a large excess of hydroquinone, rods with LSPR up to 1230 nm can be synthesized with a high degree of purity, reliability, and near quantitative conversion of gold ions to metallic gold. The growth of the rods is tracked by TEM utilizing a thiolation reaction to halt their growth. Finally, the effect of changing various parameters including hydroquinone, seed, gold, and silver concentration is examined, demonstrating the tunability of the procedure over the broad range of attainable LSRPs from 770 to 1230 nm.