Enhanced peroxidase-like activity based on electron transfer between platinum nanoparticles and Ti 3 C 2 T X MXene nanoribbons coupled smartphone-assisted hydrogel platform for detecting mercury ions.

Background: Heavy metal pollution poses a serious threat to the ecological environment. Mercury ion (Hg ²⁺ ) is a class of highly toxic heavy metal ions, which is bioaccumulative, difficult to breakdown, and has a significant affinity with sulfur and thiol-containing proteins, which seriously affects environmental safety and human health. Nanozyme-based sensing methods are expected to be used to detect toxic heavy metal ions. However, the application of precious metal nanozymes to develop portable sensors with simplicity, high stability, and high sensitivity has not been explored to a large extent.
Results: In this paper, based on MXene's unique adsorption capacity for certain precious metal ions, PtNPs/Ti ₃ C ₂ T _X NR composites were successfully prepared by in-situ growth of Pt nanoparticles (PtNPs) on the surface of Ti ₃ C ₂ T _X MXene nanoribbons (Ti ₃ C ₂ T _X NR) using the hydrothermal technique. Experimental data revealed PtNPs/Ti ₃ C ₂ T _X NR exhibited superior peroxidase-like activity, attributed to the synergistic effect of well-dispersed ultrasmall PtNPs and electron transfer effect. Hg ²⁺ can significantly inhibit enzyme-like activity of PtNPs/Ti ₃ C ₂ T _X NR due to specific capture and partial in-situ reduction of PtNPs, so a colorimetric sensor was constructed for ultra-trace detection of Hg ²⁺ with a linear range of 0.2 nM and 400 nM. Furthermore, using the portable detecting capabilities of smartphones and hydrogel, a smartphone-assisted hydrogel sensing platform of Hg ²⁺ was constructed. Notably, the two-mode sensing platforms exhibited outstanding detection performance with LOD values as low as 15 pM (colorimetric) and 26 pM (hydrogel), respectively, superior to recently reported nanozyme-based Hg ²⁺ sensors.
Significance: Compared with other methods, the PtNPs/Ti ₃ C ₂ T _X NR-based dual-mode sensor designed in this paper has superior sensitivity, high selectivity, simple operation and portability. In particular, the dual-output sensing strategy enables self-confirmation of detection results, greatly improving the reliability of the sensor, and is expected to be used for the on-site determination of trace mercury ions.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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