An improved synthesis of gold nanorods with tunable dimensions and localized surface plasmon resonance properties

Gold nanorods have been pursued due to their unique optoelectronic properties, which have led to potential uses in multiple applications. We sought to prepare gold nanorods that would potentially be used in biomedical applications, such as bio-imaging, photothermal therapies, and drug delivery systems. Typically in biomedical applications, gold nanorods with a localized surface plasmon resonance band that lies in the near infrared window between 650 to 1350 nm is highly desirable to obtain better images and an efficient photothermal effect over a range of depths within biological tissues. In addition, the dimensions of gold nanorods also play an important role in terms of cellular uptake and retention, as well as controlling the ratio between their absorbance and scattering properties. Thus, a primary goal of our study was to regulate dimensions and localized surface plasmon resonance of the gold nanorods to improve their potential utility in applications requiring both cellular uptake and photothermal triggered processes through the use of localized surface plasmon resonance bands in the near infrared “window”. We have modified the seed-mediated method by sequentially varying concentrations of hydrochloric acid and chloroauric acid to tune the dimensions, and thus the properties of the gold nanorods. The average dimensions of the gold nanorods were tuned from 24±4 nm in length and 7±1 nm in width, to 47±10 nm in length and 11±2 nm in width from these adjustments in the concentration of hydrochloric acid and chloroauric acid in the growth solution.