Colorimetric Detection Of Heavy Metal Residue Based On Colloidal Gold Paper Devices

Paper-based devices have the advantages of low cost,simple operation,and good bio-compatibility.Most detection methods can be implemented on paper-based devices,which are widely used in various fields.Gold nanomaterials have special optical properties and catalytic properties,so many detection methods are established.In this dissertation,paper-based devices combined with gold nanomaterial-based colorimetric detection methods were established for mercury and copper ions.1.A paper-based device for colorimetric detection of Hg²⁺was established based on the gold nanozyme.Hg²⁺can stimulate peroxidase-like activity of AuNPs,which can catalyze the color reaction of hydrogen peroxide?H₂O₂?and tetramethylbenzidine?TMB?from colorless to blue.The paper-based device was composed of three parts:test paper,absorption filter paper and the carrier of paper.AuNPs and Hg²⁺solution were dropped on detection zones of the paper-based device.As a reaction substrate,the test paper included multiple detection areas and a distribution area for simultaneous detection of different concentrations of Hg²⁺.By stacking the filter paper,the volume of the Hg²⁺solution increased to act to filter and concentrate regents and improve the sensitivity of the detection.Qualitative detection can be performed directly by visually recognizing color changes.The minimum concentration of Hg²⁺recognized by the naked eye was 50 nmol/L.The assay results were recorded by scanner and then colorimetric signal analysis was carried out by using ImageJ software.The linear range of Hg²⁺detection was 50 nmol/L?2000 nmol/L and the detection limit was 6.7 nmol/L.In addition,the paper-based device was also applied to detect tap water and lake water samples,and the rang of recovery was 80%?120%.2.A T-shaped test paper was established for colorimetric detection of Cu2+.The sulfhydryl groups of cysteine?Cys?can be bonded to the surface of AuNPs through the formation of Au-S bonds,which can cause AuNPs to aggregate,and the solution color was blue-purple.Cu²⁺can catalyze the oxidation of Cys to cystine.When the AuNPs solution was dispersed,the color turned red.The filter paper were treated by ethanol washing and wetting,and the test paper were designed as a T shape with a detection area and a sample area,so that the color development was uniform.The color can be directly recognized by the naked eye.With the Cu²⁺concentration increasing,the test paper turned from blue to red.The minimum concentration of Cu²⁺recognized by the naked eye was 50 nmol/L.The assay results were recorded by scanner and then the RGB of image was analyzed by using Image J.On the basis,Cu²⁺can be achieved the quantitative detection.The linear range of Cu²⁺detection was50 nmol/L?500 nmol/L and the detection limit was 24 nmol/L.In addition,the detection method was also applied to detect Cu²⁺in lake water samples.3.A test strip was established for colorimetric detection of Cu²⁺based on AuNPs.The nitrocellulose membranes were used as the reaction matrix,and the membranes were modified by PEI,then AuNPs can be capture to achieve enrichment of the detection signal.According the color change of AuNPs induced by Cys and Cu²⁺,Cu²⁺was qualitatively detected.The minimum concentration of Cu²⁺recognized by the naked eye was 10 nmol/L.In addition,Cu²⁺was quantitatively detected by analyzing the RGB of the image.The linear range of Cu²⁺detection was 10 nmol/L?70 nmol/L and the detection limit was 4.5 nmol/L.In addition,the detection method was also applied to detect Cu²⁺in tea samples,with certain accuracy and reliability.