Preparation Of Nanozyme And Its Application Research In Hg²⁺ Detection

Nanozymes are one sort of new nanomaterials with enzymatic performance.Compared to natural enzymes,nanozymes possess many advantages such as low cost,high stability and the unique properties of nanomaterials,and,therefore,have broad application prospects in the fields of biochemical analysis,environmental monitor and so on.In this paper,two kinds of nanozymes,Cu S hollow nanospheres and Ag nanowire,were fabricated by solution reaction.The colorimetric reaction of 3,3’,5,5’-Tetramethylbenzidine（TMB）catalyzed by these two nanozymes in the heavy metal Hg²⁺enviroment was investigated systematically.Two kinds of portable nanosensor and an enrichment-detection integration strategy were developed for Hg²⁺detection.（1）Cu S hollow nanospheres,possessing an intrinsic peroxidase-like activity,were prepared by a simple water bath method.With the existence of hydrogen peroxide（H₂O₂）,the colorimetric reaction of TMB can be catalyzed by Cu S nanozymes.However,if there are Hg²⁺ions in the solution,the catalytic activity of Cu S nanospheres can be reduced due to the reaction between Hg²⁺and Cu S.Therefore,Hg²⁺detection can be achieved according to the absorbance of the described colorimetric reaction.The results show that the colorimetric assay can be affected by p H,temperature and the amounts of H₂O₂ and Cu S,with the optimum parameters being 3.6,40℃,25 m M and0.7～2.8 mg/L,respectively.Based on this,a portable and sensitive nanosensor for Hg²⁺detection was developed with the dynamic detection range and the limit of detection（LOD）for Hg²⁺being 5～400 ppb and 5 ppb,respectively.With the combination of the separation-enrichment technique for Hg²⁺and a commercial RGB sensor,an enrichment-detection integration strategy were developed for Hg²⁺detection,wherein Cu S nanozyme is used as Hg²⁺recognition unit,Hg²⁺enrichment/preconcentration carrier and signal amplifier/output unit.This strategy further reduces the LOD of nanosensor to 50 ppt,and possesses wide detection range（50 ppt～400 ppb）,satisfactory accuracy（deviation<10%）and reproducibility（recovery≈82%）.（2）the unmoditifed Ag nanowires（Ag NWs）were synthesized by a solvothermal method,with the length longer than 20μm and the diameter of 130～150 nm.The so-called amalgam alloy（Ag-Hg）can be formed according to the reaction between Ag NWs and Hg²⁺.The amalgam has the oxidase-like activity and can facilitates the colorimetric reaction of the TMB solution containing oxygen.Similarly,Hg²⁺detection can be achieved according to the absorbance of the described colorimetric reaction.The colorimetric assay can be affected by p H,temperature and the amount of Ag NWs,with the optimum parameters being 5,4℃ and 100μL,respectively.The developed nanosensor presents excellent selectivity for Hg²⁺,with the dynamic detection range and the LOD for Hg²⁺being 25～5000 ppb and 19.9 ppb,respectively.