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Novel Ascorbic Acid Based Ionic Liquids for the In Situ Synthesis of Quasi‐Spherical and Anisotropic Gold Nanostructures in Aqueous Medium
Author(s) -
Dinda Enakshi,
Si Satyabrata,
Kotal Atanu,
Mandal Tarun K.
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800006
Subject(s) - ionic liquid , ascorbic acid , in situ , nanostructure , anisotropy , aqueous medium , materials science , aqueous solution , chemical engineering , ionic bonding , nanotechnology , chemistry , organic chemistry , ion , catalysis , optics , physics , food science , engineering
A series of newly designed ascorbic acid based room temperature ionic liquids were successfully used to prepare quasi‐spherical and anisotropic gold nanostructures in an aqueous medium at ambient temperature. The synthesis of these room temperature ionic liquids involves, first, the preparation of a 1‐alkyl (such as methyl, ethyl, butyl, hexyl, octyl, and decyl) derivative of 3‐methylimidazolium hydroxide followed by the neutralization of the derivatised product with ascorbic acid. These ionic liquids show significantly better thermal stability and their glass transition temperature ( T g ) decreases with increasing alkyl chain length. The ascorbate counter anion of these ionic liquids acts as a reducing agent for HAuCl 4 to produce metallic gold and the alkylated imidazolium counter cation acts as a capping/shape‐directing agent. It has been found that the nature of the ionic liquids and the mole ratio of ionic liquid to HAuCl 4 has a significant effect on the morphology of the formed gold nanostructures. If an equimolar mixture of ionic liquid and HAuCl 4 is used, predominantly anisotropic gold nanostructures are formed and by varying the alkyl chain length attached to imidazolium cation of the ionic liquids, various particle morphologies can formed, such as quasispherical, raspberry‐like, flakes or dendritic. A probable formation mechanism for such anisotropic gold nanostructures has been proposed, which is based on the results of some control experiments.