Ag⁺-Gated Surface Chemistry of Gold Nanoparticles and Colorimetric Detection of Acetylcholinesterase

Chemical regulation of enzyme-mimic activity of nanomaterials is challenging because it requires a precise understanding of the surface chemistry and mechanism, and rationally designed applications. Herein, Ag⁺-gated peroxidase activity is demonstrated by successfully modulating surface chemistry of cetyltrimethylammonium bromide-capped gold nanoparticles (CTAB-AuNPs). A surface blocking effect of long-chain molecules on surfaces of AuNPs that inhibit peroxidase activity of AuNPs is found. Ag⁺ ions can selectively bind on the surfaces of AuNPs and competitively destroy CTAB membrane forming Ag⁺@CTAB-AuNPs complexes to result in enhanced peroxidase activity. Ag⁺@CTAB-AuNPs show the highest peroxidase activity compared to similar-sized citrate-capped and ascorbic acid-capped AuNPs. Ag⁺@CTAB-AuNPs can potentially develop into analyte-responsive systems and exhibit advantages in the optical sensing field. For example, the Ag⁺@CTAB-AuNPs system shows an enhanced sensitivity and selectivity for acetylcholinesterase activity sensing compared to other methods.