Hierarchical meso-macroporous iron-nitrogen-coordinated carbon nanozyme: Preparation, catalytic mechanism, and used as colorimetric sensor array for on-site discrimination and detection of multiple sulfides

As commonplace food preservatives or flavor regulators, excessive intake of sulfides can bring adverse effects to harm health. Nanozyme-based sensor array enables rapid and on-time detection and discrimination of sulfide in food samples.

A meso-macroporous iron-nitrogen-coordinated carbon nanozyme (mpFe-NCzyme) was synthesized and presented uniform spherical morphology with a meso-macroporous structure, resulting in large specific surface area, fully exposing and utilizing the active sites (Fe-N), and favoring the mass transport. Therefore, mpFe-NCzyme showed excellent peroxidase-like activity. Based on the different inhibitory effects of sulfides (Na₂S₂O₈, Na₂S, Na₂S₂O₃, and L-cysteine) on the peroxidase-like activity, a three-channel mpFe-NCzyme colorimetric sensor array for accurate sulfides identification and detection was constructed using three colorimetric reactions. The "fingerprints" of different colorimetric changes can be obtained using mpFe-NCzyme sensor array, and four sulfides could be well discriminated by principal component and hierarchical cluster analysis even at low concentration of 0.2 μM. The low of detections of mpFe-NCzyme sensor array for Na₂S₂O₈, Na₂S, Na₂S₂O₃ and L-Cys were 0.15 μM, 0.11 μM, 0.19 μM and 0.35 μM, respectively. The sensor array also provides excellent discrimination capability for mixed sulfides. Importantly, it has been successfully used to distinguish and detect sulfides in real samples with the recovery rates ranging from 95.9 % to 122.5 %. These relative standard deviations were less than 2.41 %, suggesting the reliable performance of the mpFe-NCzyme-based methods in real samples. Meanwhile, the sensor array exhibited good anti-interference capability and excellent identification for blind samples.

This research presents a novel nanozyme and promotes its application in the development of sensor array, which was used for effective detection and discrimination of sulfide in real samples.