Nanozymes for Detection of Metal Ions

Large-scale mining, manufacturing, groundwater extraction, groundwater depletion and uncontrolled discharge of industrial waste have caused severe heavy metal ion pollution of the world's environment. Therefore, rapid detection of such toxic metal ions is imperative. However, it is difficult to operate in field conditions, as conventional detection methods require sophisticated instruments and skilled personnel. Recently, nanozyme-based assays have been found to have the potential to replace traditional methods due to their portability, simplicity and high sensitivity to detect metal ion concentrations.

Heavy metal ion detection systems based on nanozymes enable rapid and inexpensive screening by using simple instruments. Therefore, they are convenient for use in field operations, especially in remote regions of the world. Creative Enzymes offers nanozymes and schemes for the detection of metal ions.

Analysis of Ag⁺ with Nanozyme

• Creative Enzymes designs a platinum nanozymes with peroxidase-like activity. A colorimetric sensor for the detection of Ag⁺ in water was constructed based on the attenuation of the simulated enzyme activity due to the adsorption of Ag⁺ at its surface-active site and the reduced degree of the H₂O₂-TMB chromogenic reaction.
• It has the advantages of high sensitivity, fast response, and strong anti-interference ability, which can meet the needs of Ag detection in tap water.

Fig. 1 Schematic illustration of the principle of Pt nanozyme assay for colorimetric detection of Ag⁺.

• We also use amino acids to regulate the peroxidase-like activity of Pd nanozymes. The modified enzyme by amino acids has a smaller size, higher content, and better hydrophilicity, thus its catalytic ability for the H₂O₂-TMB color reaction is significantly improved. Nanozymes enable accurate and specific determination of Ag⁺ in water.

Analysis of Hg²⁺ with Nanozyme

• Based on the interaction between Hg²⁺ and cysteine, we develop a colorimetric sensor using carbon dots with peroxidase mimetic enzymes. Cysteine is able to inhibit the production of cationic radicals and prevent the appearance of blue oxidation products of the substrate TMB. However, Hg²⁺ has a strong affinity for cysteine, which allows the color product blue cations to form normally, and the chromaticity increases with Hg²⁺ concentration.
• Hg²⁺ enhances the peroxidase activity of chitosan-modified Au nanozymes by aggregation-induction. Therefore, we establish a label-free, simple, and rapid visual detection method for Hg²⁺.

Analysis of Fe²⁺ with Nanozyme

• Although Fe²⁺ is an essential metal ion for human body, its excessive intake will also cause a great threat to human health. Therefore, it is important to establish a fast measurement method for this ion to protect human health.
• Previous studies have shown that Fe²⁺ can significantly enhance the activity of MoS₂ nanozymes. Based on this synergistic enhancement, we construct label-free colorimetry and fluorescence sensors for Fe²⁺ determination in water.

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