Construction And Application Of Visual Sensor Based On Gold Nanoparticles

The visual detection methods are based on the optical signal to realize the detection of the target object by observing the color change of the solution with the naked eye.They have many advantages,such as simple operation,low cost,rapid response and visual detection.In various nanomaterials,gold nanoparticles?Au NPs?are used widely in the construction of visualization sensors due to their unique physical and chemical properties and excellent optical properties.A series of sensors can be designed based on the local surface plasmon resonance effect of Au NPs,that is,if the morphology and dispersion degree of Au NPs are changed that the color of the system will change accordingly;Au NPs can form stable gold amalgam structure with mercury to improve its catalytic performance,which accelerate the reaction of the chromogenic agent with the substrate,and detect the target via the change of color in this system;Au NPs have mimicking enzyme activities,for instance,citrate-stable Au NPs with glucose oxidase-like activity,which can be used in combination with other nanoenzyme materials possed peroxidase-like activity for glucose detection.In this paper,the local surface plasmon resonance effect,gold amalgam catalytic performance and glucose oxidase-like activity of Au NPs are discussed to build a new visual detection platform to realize the colorimetric detection of Cr³⁺,Cr⁶⁺and glucose.The main work of this paper is as follows:1.Preparation of gold nanoparticles and visual detection of Cr³⁺in wide range of pHIn this chapter,a new method to prepare Au NPs was presented successfully.That is to say,we obtained Au NPs with small size,good stability and uniform dispersion via the sodium borohydride was used to reduce chloroauric acid in buffer solution of citric acid-disodium hydrogen phosphate with different pH values.A simple,fast,highly selective and sensitive method was proposed for colorimetric detection of Cr³⁺based on the local surface plasmon resonance effect of Au NPs.The principle is that Cr³⁺can induce Au NPs aggregation to change the color of the solution.2.Study on the catalytic activity of small-sized gold nanoparticles and visual detection of Cr⁶⁺Based on the previous work,we synthesized the small-sized Au NPs at room temperature used the method described in the second chapter.We have successfully prepared gold amalgam nanocomposites?Au@Hg?and found they have oxidoreductase-like activity and could greatly accelerate the reaction of Cr⁶⁺and TMB to give an intense blue product.Therefore,using Cr⁶⁺with strong oxidizing properties,a new colorimetric method was established to detect Cr⁶⁺based on gold amalgam catalyst.3.Preparation of liposome-coated gold nanoparticle and visual detection of glucoseIn this chapter,inspired by the intrinsic glucose oxidase property of gold nanoparticles and high loading ability of liposomes,a liposome-mediated artificial enzyme tandem catalytic system was constructed for the one-step glucose detection.In the presence of Au NPs,glucose is oxidized into gluconic acid by oxygen to produce hydrogen peroxide;Next,the chromogenic agent is oxidized into colored product by the as-produced hydrogen peroxide,where the reaction is catalyzed by intrinsic peroxidase Fe₃O₄ NPs.The colorimetric detection method of glucose were established via combining multi-enzyme with liposomes and built a multi-enzyme tandem catalytic system to realize colorimetric quantitative determination of glucose without the help of natural enzymes successfully.