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In recent years, considerable efforts have been devoted to the construction of efficient enzyme mimetics, which have significant advantages of simple synthesis and good stability. In this paper, we prepared novel graphene oxide–gold (GO–AuNP) nanohybrids that exhibited fascinating peroxidase-like activity and could catalyze the oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) by H2O2, while simultaneously developing a blue color in an aqueous solution. Furthermore, single-stranded DNA (ssDNA) were able to resist the salt-induced aggregation of GO–AuNP nanohybrids, whereas double-stranded DNA (dsDNA) did not inhibit salt-induced GO–AuNP nanohybrids aggregation. Based on these unique properties, we developed a label-free colorimetric method for the detection of Hg2+and Pb2+. In the presence of Hg2+or Pb2+, ssDNA formed a hairpin-like or a quadruplex structure, and these conformational changes facilitated the salt-induced aggregation of GO–AuNP nanohybrids, leaving behind a transparent supernatant after centrifugation. After incubation with TMB and H2O2, the colorimetric signal of the centrifugal supernatant was significantly decreased compared to that in the absence of Hg2+or Pb2+. The response to Hg2+and Pb2+were in the range of 0–50 μM. Finally, this simple and sensitive sensor could be successfully applied for the detection of Hg2+and Pb2+in river water.

For the first time, gold nanoclusters were found to exhibit high fluorescence enhancement ability based on the metal-enhanced fluorescence (MEF) effect, which can effectively enhance the fluorescence of fluorescein isothiocyanate (FITC). By means of this phenomenon, Au nanoclusters have been successfully used in the construction of a fluorescence-enhanced sensing platform for the detection of protooncogene.

A recent study reported by Higuchi's group has shown that Pt–DNA complexes possess peroxidase enzymatic activity similar to natural peroxidases. In this study, we prepared Pt–DNA complexes and demonstrated their use in catalyzing the oxidation of a peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2to the oxidized product which provided a colorimetric detection of H2O2. As low as 3.92 × 10−4mol L−1H2O2could be detected with a linear range from 9.79 × 10−4to 1.76 × 10−2mol L−1viaour method. Furthermore, PVDF membranes were employed to increase sensitivity and decrease the detection limit of H2O2, enabling a two-fold improvement in the detection sensitivity as compared with the above counterparts. More importantly, a sensitive and selective method for glucose detection was developed using glucose oxidase (GOx) and the as-prepared Pt–DNA complexes. We realized the test of glucose as low as 10−7mol L−1by the color change, which was comparable to or even better than the existing methods, and identified the concentration of glucose in Sprite with the naked eye without referring to any sophisticated apparatus. The detection platforms for H2O2and glucose developed in the present work showed great potential for applications in the future.