Room-Temperature Turkevich Method: Formation of Gold Nanoparticles at the Speed of Mixing Using Cyclic Oxocarbon Reducing Agents

Abstract

We demonstrate a facile and reproducible means of producing quasi-spherical, colloidally stable gold nanoparticles (AuNPs) on the basis of rapid room-temperature mixing of aqueous solutions of HAuCl4 and a cyclic oxocarbon diacid (squaric acid, SA; croconic acid, CA; or rhodizonic acid, SR) or ascorbic acid (AA) as dual reducing and capping agent. Although these reducing agents generally produced larger particles than those derived from the classical Turkevich method (using citrate in boiling water) and achieved a lower nanoparticle size uniformity in our hands (i.e., 30.4 ± 8.6, 33.1 ± 9.3, 29.9 ± 6.3, and 29.7 ± 7.6 nm for SA, AA, CA, and SR, respectively, compared with 15.8 ± 3.7 nm for citrate), the method is versatile and exceptionally convenient as fairly monodisperse AuNPs can be made “on-demand” within seconds by simple mixing in the absence of heating. A preliminary investigation into the effects of reaction parameters, such as synthesis temperature and the molar ratio of reducing agent to HAuCl4...