EPR study of dialkyl nitroxides as probes to investigate the exchange of solutes between the ligand shell of monolayers of protected gold nanoparticles and aqueous solutions.
EPR spectroscopy has been used to study the interaction of para-substituted benzyl hydroxyalkyl nitroxides with the monolayer of water-soluble protected gold cluster made by a short alkyl chain and a triethylene glycol monomethyl ether unit. The inclusion of nitroxide probes in the more hydrophobic environment of the monolayer gave rise to a reduction of the value of both nitrogen and beta-proton hyperfine splittings. The spectra also showed selective line broadening attributed to modulation of the spectroscopic parameters as the result of exchange between free and complexed nitroxide. The rate constants were obtained by analyzing the EPR line shape variations as functions of nanoparticle concentration and temperature. This represents, to the best of our knowledge, the first determination of rate constants for the solubilization of organic substrates in a monolayer-protected cluster.
Department of Organic Chemistry A. Mangini, University of Bologna, Via San Donato 15, 40127, Bologna, Italy. lucarini@alma.unibo.it
Marco
M
Lucarini
Paola
P
Franchi
Gian Franco
GF
Pedulli
Paolo
P
Pengo
Paolo
P
Scrimin
Lucia
L
Pasquato
D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008024:Ligands; D036103:Nanotechnology; D009589:Nitrogen Oxides / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D012996:Solutions; D014867:Water / Q000737:chemistry
D005609:Free Radicals; D008024:Ligands; D009589:Nitrogen Oxides; D012996:Solutions; D014867:Water; D011092:Polyethylene Glycols; C035053:triethylene glycol monoethyl ether; D006046:Gold