Shape-selective purification of gold nanorods with low aspect ratio using a simple centrifugation method

This work presents a new and simple procedure for the shape selective purification of gold nanorods from a mixture of rods and spheres. Previously reported methods were time-consuming and revealed several drawbacks such as low yields and difficulty to recover the purified nanoparticles. Additionally, they were mostly applied to high aspect ratio (AR) nanorods. Our process is based on only simple and short centrifugation steps in order to precipitate specifically gold nanospheres. Samples containing low AR nanorods (AR?<?6) were selected to perform the purification process. The supernatant content was followed by UV-Visible absorption spectroscopy after each centrifugation step. Then, transmission electron microscopy (TEM) allowed extract the purification efficiency thanks to shape analyses performed on more than 1000 nanoparticles. These results showed that our centrifugation process was applied successfully to three sizes of nanorods (2.4, 3.7, and 5.3). High purification yields of 72 and 78% were attained for AR?=?3.7 and AR?=?5.3 nanorods, respectively.