Reproducibly synthesize gold nanorods and maintain their stability

Gold nanorods (AuNRs) provide unique optical features due to their surface electrons. They have become one of the most rapidly developed optical nanomaterials in recent years. The seed-mediated growth method is the most common approach for the synthesis of gold nanorods (AuNRs). However, the reproducibility for making AuNRs with the same absorption wavelength has proven to be a challenge. In addition, the stability of the produced AuNRs is also a concern. To reproducibly synthesize AuNRs and maintain their stability, in this work a number of factors that affect the reproducibility of AuNRs in the seed-mediated growth method were studied systematically. Particularly, the effect of L-ascorbic acid during the synthesis of AuNRs was studied in detail. The effects of other factors, such as the amount of NaBH4 in the gold seed preparation and reaction temperature, were studied as well. Our results showed that the aspect ratio of produced AuNRs was affected by several factors. The amount of L-ascorbic acid (L-AA) played an important role among these factors. Afterwards, the long term and the short term stability of AuNRs in various conditions were studied. Under the optimum conditions, the AuNR samples were stable for at least nine months.