Disclosure of the imidazolium cation coordination and stabilization mode in ionic liquid stabilized gold(0) nanoparticles |
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Authors: | Schrekker Henri S Gelesky Marcos A Stracke Marcelo P Schrekker Clarissa M L Machado Giovanna Teixeira Sergio R Rubim Joel C Dupont Jairton |
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Affiliation: | Laboratory of Molecular Catalysis, Institute of Chemistry, UFRGS, Av. Bento Gon?alves 9500, P.O. Box 15003, CEP: 91501-970, Porto Alegre, RS, Brazil. schrekker@iq.ufrgs.br |
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Abstract: | A surface-enhanced Raman spectroscopy (SERS) study of imidazolium ionic liquid stabilized gold(0) nanoparticles (GNPs) furnished previously unknown knowledge about the coordination and stabilization mode of the imidazolium cation. GNPs were prepared by hydrazine reduction of a chloroauric acid solution in 1-triethylene glycol monomethyl ether-3-methylimidazolium methanesulfonate 2 as ether-functionalized room-temperature ionic liquid (RTIL). UV-vis spectroscopy showed the presence of GNP aggregates as absorptions extended to the NIR region. A parallel coordination mode for the imidazolium cation of RTIL 2 on the GNP surface was observed by SERS, which occurred without the simultaneous coordination of the 1-triethylene glycol monomethyl ether-functionality. Instead of this, the ether-functionality was directed away from the GNP surface and acted as steric barrier between the GNPs/GNP aggregates, thus preventing further aggregation. These new insights suggest that the imidazolium cation is responsible for electrosteric stabilization. |
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