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The Role of Onium Salts in the Pro‐Oxidant Effect of Gold Nanoparticles in Lipophilic Environments
Author(s) -
Baschieri Andrea,
Del Secco Benedetta,
Zaccheroni Nelsi,
Valgimigli Luca,
Amorati Riccardo
Publication year - 2018
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.201801110
Subject(s) - chemistry , onium , bromide , colloidal gold , nanoparticle , radical , counterion , thiol , organic chemistry , photochemistry , inorganic chemistry , chemical engineering , ion , engineering
Metal nanoparticles are reported to be toxic due to the generation of free radicals at their surface. Relatively inert thiol‐capped gold nanoparticles (AuNPs) have been reported to induce radical formation in the presence of hydroperoxides, which would conflict with their potential use as inert scaffolds for the design of novel nano‐antioxidants. With the aim of clarifying this aspect, we investigated the pro‐oxidant activity of dodecanethiol‐capped AuNPs (∼5 nm diameter), prepared through the Brust–Schiffrin synthesis, by oxygen‐uptake kinetic studies. The pro‐oxidant activity was found to be proportional to the impurities of the transfer agent tetraoctylammonium bromide (TOAB) left from the synthesis and decreased on repeated washing of the nanoparticles. Under identical settings similar batches of AuNP (∼9 nm diameter) prepared through the Ulman method without onium salts showed no pro‐oxidant behavior. The alternative onium phase‐transfer agents Oct 4 NBF 4 (Oct=octyl), Hex 4 NBF 4 (Hex=hexyl), and Hex 4 NPF 6 were comparatively investigated and showed lower pro‐oxidant activity depending on the counterion (Br − >PF 6 − >BF 4 − ).