An updated comprehensive review to help researchers understand nanozymes better and in turn to advance the field.

Nanozymes, the enzyme-mimicking nanomaterials, have been developed to overcome the low stability and high cost of natural enzymes. Unlike highly active and specific enzymes, however, the catalytic activities of nanozymes are moderate and lack specificity. To address these issues, herein we demonstrated an effective and general strategy to specifically enhance the peroxidase-mimicking activities of carbon nanozymes. By doping heteroatom nitrogen (N) into reduced graphene oxide (rGO) and mesoporous carbon (MC), their peroxidase-mimicking activities were enhanced by over 100- and 60-fold, respectively. Moreover, N-doping did not significantly affect the oxidase-, superoxide dismutase (SOD)-, or catalase-mimicking activities of rGO and MC, demonstrating a specific enhancement of the peroxidase-mimicking activities. To understand the origin of the specific enhancement, we performed density functional theory calculations to examine the catalytic reaction mechanisms responsible for the peroxidase-, catalase-, oxidase-, and SOD-mimicking activities of N-doped rGO (N-rGO). We revealed that N-rGO selectively activated H2O2 rather than O2 and •O2 – by forming and stabilizing radical oxygen species adjacent to the N sites of N-rGO. The radical oxygen species then oxidized peroxidase substrates, endowing N-rGO with peroxidase-mimicking activity. This study will aid in the rational design of highly active and specific peroxidase mimics and help elucidate the catalytic mechanisms of nanozymes.

Pesticides, widely used for pest control and plant growth regulation, have posed a threat to the environment and human health. Conventional methods to analyze pesticide residues are not applied to resource-limited areas because of their high cost, complexity, and requirements for expensive instruments (such as GC/MS and LC/MS). To address these challenges, herein we fabricated colorimetric nanozyme sensor arrays based on heteroatom-doped graphene for detection of aromatic pesticides. The active sites of nanozymes could be differentially masked when different pesticides were adsorbed on the graphene, which in turn resulted in the decrease of their peroxidase-mimicking activities. On the basis of this principle, five pesticides (i.e., lactofen, fluoroxypyr-meptyl, bensulfuron-methyl, fomesafen, and diafenthiuron) from 5 to 500 μM were successfully discriminated by the sensor arrays. In addition, discrimination for different concentrations of each pesticide and different ratios of two mixed pesticides were also demonstrated. The practical application of the sensor arrays was further validated by successfully discriminating the pesticides in soil samples. This work not only provides a facile and cost-effective method to detect pesticides but also makes a positive contribution to food safety and environmental protection.

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Schematic representation of biothol detection using gold alloy-based nanozyme sensor arrays.

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Correction for ‘Gold alloy-based nanozyme sensor arrays for biothiol detection’ by Junshu Lin et al., Analyst, 2020, DOI: 10.1039/d0an00451k.