Preparation Of Platinum-Based Nanozymes And Their Application In Rapid Visual Detection Of Mercury Ions

The current heavy metal ion pollution is becoming increasingly severe,posing a significant threat to human health.Mercury ion(Hg²⁺)is one of the most representative heavy metal ions,which is difficult to degrade and easily accumulated in biology.Once its level exceeds the standard,both human living environments and physical health will be adversely affected.Therefore,establishing a simple and sensitive mercury ion detection method is of great practical significance.In addition to the many mature traditional detection methods in recent years,colorimetric methods have received widespread attention due to their relatively low cost,more convenient operation,high sensitivity,and qualitative or semi-quantitative analysis with the naked eye.In this paper,we mainly utilize the excellent peroxidase-like activity of the prepared platinum-based nanomaterials to establish three mercury ion colorimetric detection methods.These nanomaterials include the sodium citrate-modified platinum nanoparticles,two-dimensional nanomaterials graphene oxide loaded with platinum nanoparticles,and mesoporous silica sphere-loaded Au NPs/PtNPs,respectively.（1）A colorimetric detection method for mercury ions based on sodium citrate-modified platinum nanoparticles.Based on the peroxidase-like activity of platinum nanoparticles modified with sodium citrate and the interaction between mercury and platinum,a rapid colorimetric method for detecting mercury ions in water was constructed.First,the synthesized sodium citrate-terminated platinum nanoparticles serve as nano-enzymes,which have excellent catalytic activity similar to peroxidase,catalyzing the color reaction between hydrogen peroxide（H₂O₂）and 3,3’,5,5’-tetramethylbenzidine（TMB）.Secondly,the reaction between mercury ions and platinum nanoparticles effectively inhibits the catalytic activity of the platinum nanozyme.Therefore,the quantitative detection method was established,which has outstanding advantages of a wide linear range（1-5000 n M）,sensitive detection limits,good reproducibility,and good selectivity.Finally,this method can be used to achieve rapid detection of mercury ions in tap water and lake water.（2）Label-free colorimetric detection of mercury ions based on graphene oxide/platinum nanoparticle nanoenzymes.A composite nano-enzyme with peroxidase-like activity was formed by in-situ reduction of platinum nanoparticles on the surface of two-dimensional nanosheet material graphene oxide.By using different characterization methods and stability experiments,a composite nanozyme that not only retains the peroxidase-like activity due to the platinum nanoparticles but also has good dispersion and stability on the surface of graphene oxide.A rapid and ultrasensitive colorimetric method for detecting mercury ions in water was established by using the catalytic substrate of the prepared nanozyme The detection method has the advantages of simple operation,excellent reproducibility.Finally,this method can be applied to the detection of mercury ions in real samples.（3）Label-free colorimetric detection of mercury ions by branched silicon nanoenzymes loaded with gold/platinum nanoparticlesBy utilizing the porous structure of branched silicon nanoenzymes to adsorb gold nanoparticles and platinum nanoparticles,the composite nanomaterial was prepared and characterized in terms of morphology,structure,and elemental composition.The experimental results showed that the prepared nanomaterial had excellent peroxidase-like activity,which could catalyze the oxidation of TMB in the presence of hydrogen peroxide,and its activity could be effectively inhibited by mercury ions.Based on the above findings,a colorimetric method for the detection of mercury ions was established.Under the optimal experimental conditions,there is a good linear relationship between absorbance and mercury ion concentration in the range of 0.1 n M to 10μM,and the detection limit was8.58 p M.The method was comparable to other methods,and the recovery rate of mercury ion detection in tap water,lake water,and polluted water was between 90.0%and 104.7%.This method has the potential in monitoring mercury ions in environmental water samples,demonstrating the feasibility of constructing a mercury ion detection platform.