Double layer micellar stabilization of gold nanocrystals by greener ionic liquid 1-butyl-3-methylimidazolium lauryl sulfate

We report the first synthesis of anisotropic gold nanocrystals (AuNC) prepared by a seeding approach using the greener ionic liquid, 1-butyl-3-methylimidazolium lauryl sulfate, [BMIM] [C12H25OSO3]. Crystal growth was successfully achieved by successive addition of growth solution containing HAuCl4 and ascorbic acid to 2.5-nm Au seeds. These nanocrystals were stabilized by the ionic liquid via a two layer micellar formation. SEM and TEM results showed Au nanocrystals with particle sizes ranging from 20 to 50 nm. Selected-area electron diffraction (SAED) and PXRD pattern gave indices that correspond to Au nanocrystals. Direct addition of ionic liquid to Au seeds in 3:1 volume ratio afforded the formation of Au nanoparticles. TEM image and UV-vis data revealed the formation of 20-50 nm Au nanocrystals. These results show that the greener ionic liquid, [BMIM] [C12H25OSO3], is a suitable reaction medium for the direct synthesis of larger Au nanoparticles from Au seeds. (C) 2010 Elsevier B.V. All rights reserved.