A versatile, one-pot synthesis of gold nanostars with long, well-defined thorns using a lyotropic liquid crystal template

Abstract

We describe a simple, one-pot, silver-assisted synthesis of branched gold nanoparticles (GNPs) (nanostars) using Ag NO₃ and the mild reducing agent, ascorbic acid, in the presence of a lyotropic liquid crystal (LLC) template formed by Triton X-100 in water either in the hexagonal phase or the micellar phase above the critical micellar concentration. The LLC template is found to assist in the formation of well-defined nanostars with long, twinned thorns and provides the necessary colloidal stability that prevents the final nanostars from irreversible aggregation. In addition, the length of the thorns on the nanostars can be tailored by controlling the Au/Ag ratio in the growth solution. We discuss the contributions of the competing mechanisms that result in an optimal concentration of AgNO₃ for the synthesis of nanostars with considerably longer thorns, which is only possible in the LLC template that slows down the growth of the thorns on the initially formed GNP seeds.

Keywords:

• gold nanostars
• lyotropic liquid crystals
• template synthesis
• metal nanoparticles

Acknowledgements

We gratefully acknowledge the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canada Foundation for Innovation (CFI), the Manitoba Research and Innovation Fund (MRIF) and the Province of Manitoba (Science and Technology International Collaboration Fund) for financial support. TH additionally acknowledges support from Ohio Third Frontier’s Ohio Research Scholar Program at the Liquid Crystal Institute. All authors thank Dr. M.S. Freund for access and Dr. K. McEleney for help with XPS measurements, and A. Dufresne and Dr. Khan (all University of Manitoba) for assistance with all TEM experiments. Finally, LHC thanks the Government of Canada for a Canadian Commonwealth Scholarship.