Ahmed Waqqar, Bhatti Arshad Saleem, van Ruitenbeek Jan M
Department of Physics, COMSATS Institute of Information Technology, Park Road, Islamabad, 44000 Pakistan.
Huygens-Kamerlingh Onnes Laboratory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands.
J Nanopart Res. 2017;19(3):115. doi: 10.1007/s11051-017-3815-9. Epub 2017 Mar 17.
Seed-mediated methods are widely followed for the synthesis of Au nanorods (NRs). However, mostly dilute concentrations of the Au precursor (HAuCl) are used in the growth solution, which leads to a low final concentration of NRs. Attempts of increasing the concentration of NRs by simply increasing the concentration of HAuCl, other reagents in the growth solution and seeds lead to a faster growth kinetics which is not favourable for NR growth. Herein, we demonstrate that the increase in growth kinetics for high concentrations of reagents in growth solution can be neutralised by decreasing the pH of the solution. The synthesis of the NRs can be scaled up by using higher concentrations of reagents and adding an optimum concentration of HCl in the growth solution. The concentration of HAuCl in the growth solution can be increased up to 5 mM, and 10-20 times more NRs can be synthesised for the same reaction volume compared to that of the conventional seed-mediated method. We have also noticed that a cetyltrimethylammonium bromide (CTAB)-to-HAuCl molar ratio of 50 is sufficient for obtaining high yield of NRs.
种子介导法被广泛用于合成金纳米棒（NRs）。然而，生长溶液中大多使用稀浓度的金前驱体（HAuCl），这导致NRs的最终浓度较低。通过简单提高HAuCl、生长溶液中的其他试剂以及种子的浓度来增加NRs浓度的尝试，会导致生长动力学加快，而这对NR生长不利。在此，我们证明，通过降低溶液的pH值，可以抵消生长溶液中高浓度试剂导致的生长动力学增加。通过使用更高浓度的试剂并在生长溶液中添加最佳浓度的HCl，可以扩大NRs的合成规模。生长溶液中HAuCl的浓度可以提高到5 mM，与传统种子介导法相比，相同反应体积下可以合成多10至20倍的NRs。我们还注意到，十六烷基三甲基溴化铵（CTAB）与HAuCl的摩尔比为50足以获得高产率的NRs。
