Reaction of gold nanoparticles and tetracyano-quinoidal molecules. A spectrophotometric determination of the Au(0) content of gold nanoparticles

The interaction of gold nanoparticles (AuNPs) and typical tetracyano-quinoidal compounds such as bis(dicyanomethylene)-bithiophene and tetracyanoquinodimethane (TCNQ) has been investigated. AuNPs in toluene solution reduce the tetracyano-compounds to the radical anion as shown by UV-vis spectroscopy. The reaction, promoted by the bromide anion used as stabilizer for AuNPs, involves in the case of TCNQ the total amount of Au(0) in the nanoparticles. A spectrophotometric method for the evaluation of the Au(0) content of capped AuNPs in organic solution has been established and successfully applied to the analysis of dodecanethiol-capped AuNPs.