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The discrimination of antioxidants is of great significance because of their essential roles in various biological processes and many diseases. Compared with the traditional lock-key sensing mode for single target detection at a time, sensor arrays can discriminate various antioxidants simultaneously. Nanomaterial-based sensor arrays have shown great promise for antioxidant discrimination; however, as far as it is known, none of them have been reported for discriminating antioxidants based on the catalytic reaction of intrinsic peroxidase-like activity of two-dimensional nanomaterials. To fill the gap, we herein unveil a colorimetric (e.g., UV–vis absorption) approach for antioxidant discrimination based on the three nanomaterial [graphene oxide, molybdenum disulfide (MoS2), and tungsten disulfide (WS2)]-catalyzed 3,3′,5,5′-tetramethylbenzidine (TMB)–hydrogen peroxide (H2O2) reaction system. In this sensor array, the antioxidants inhibit the reaction between TMB and H2O2, resulting in different colorimetric response patterns. The obtained patterns for five antioxidants, including ascorbic acid, cysteine, melatonin, uric acid, and glutathione (GSH), at the 60 nM level, were successfully discriminated using linear discriminant analysis both in buffer and serum samples.

Robust but ultrasensitive aptasensors with an ability to detect lower concentrations of heavy metal ions enable the detection of serious environmental and health issues. We herein develop a label-free aptasensor for ultrasensitive detection of the silver ion (Ag+) utilizing gold nanoparticle (AuNP) intensity measurement methodology by dark-field microscopy, which is based on target Ag+and exonuclease III (Exo III)-dependent DNA cleavage recycling amplification. In the presence of target Ag+, thymine (T) bases at two termini of hairpin DNA bind with Ag+through C–Ag+–C coordination to form a DNA duplex, Exo III can recognize the blunt 3′ end of the DNA duplex and digest it from the 3′ end to the 5′ direction. The released target Ag+then binds with another hairpin DNA via C–Ag+–C pairs. After many cycles of the digestion of the DNA duplex by Exo III, numerous remaining single-stranded DNA (ssDNA) are generated. These ssDNA are absorbed on the surface of AuNPs, enhancing the repulsion force between AuNPs, which further promotes the dispersion of AuNPs, leading to a significantly decreased intensity of yellow and red dots (aggregated AuNPs) under dark-field microscopy observation, in contrast to that of the blank solution (without target Ag+). On this basis, the detection limits of 41 and 39 fM were achieved for Ag+in Tris-HCl buffer and river water, respectively.