Engineering of magnetic peroxidase-like heterojunction nanozymes from homogeneous iron precursor by surface-initiated encapsulation for self-calibration colorimetric/fluorescence dual-mode analysis of Hg2 + ion in foods.

Abstract

The engineering of multi-modal optical sensors with improved detection accuracy is still a hot topic. Herein, the homologous heterostructured nanozyme with enhanced peroxidase (POD)-like activity was prepared by surface-initiated encapsulation of porphyrin-based metal-organic frameworks on magnetic ferroferric oxide (Fe3O4@TCPP-Fe) for self-calibration colorimetric/fluorescence dual-mode detection of Hg2+ in foods. The TCPP-Fe can be in-situ surface-initiated formed via coordination reactions between TCPP and Fe2+/Fe3+ released from Fe3O4. The "electron bridge" effect of Fe2+/Fe3+ accelerates electron transfer between Fe3O4 and TCPP-Fe, thereby significantly enhancing POD-like activities of Fe3O4@TCPP-Fe. The colorimetric/fluorescence dual-mode method for determination of Hg2+ was developed based on strong oxidability of reactive oxygen species, specific recognition of aptamer, optical properties of o-phenylenediamine, and separation/enrichment effect of magnetism. The limits of detection (LOD) and limits of quantification (LOQ) were 0.02 μg/L, 0.08 μg/L, and 0.01 μg/L, 0.04 μg/L for colorimetric and fluorescence modes, respectively. In addition, the detection accuracy was further confirmed by self-calibration process between colorimetric and fluorescence modes in complex food samples. It provides a novel strategy in enhancing POD-like activity for overcoming limitations of single-mode method in complex samples.