Comparison of the peroxidase-like activity of unmodified, amino-modified, and citrate-capped gold nanoparticles

Abstract

The origin of the peroxidase-like activity of gold nanoparticles and the impact of surface modification are studied. Furthermore, some influencing factors, such as fabrication process, redox property of the modifier, and charge property of the substrate, are investigated. Compared to amino-modified or citrate-capped gold nanoparticles, unmodified gold nanoparticles show significantly higher catalytic activity toward peroxidase substrates, that is, the superficial gold atoms are a contributing factor to the observed peroxidase-like activity. The different catalytic activities of amino-modified and citrate-capped gold nanoparticles toward 3,3′,5,5′- tetramethylbenzidine (TMB) and 2,2′-azino-bis(3-ethylbenzothiazoline-6- sulfonic acid) diammonium salt (ABTS) show that the charge characteristics of the nanoparticles and the substrate also play an important role in the catalytic reactions. Nanoparticle enzyme mimics: The higher peroxidase-like activity of unmodified Au nanoparticles (NPs) compared to amino-modified or citrate-capped Au nanoparticles (see picture) reveals a role of superficial Au atoms. Different catalytic activities of amino-modified and citrate-capped Au NPs toward peroxidase substrates TMB and ABTS show that charge characteristics also play an important part. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.