The Study Of Visual Sensor Based On Gold Nanoparticles And Graphene Oxide Functional Nanomaterials

The noble metal nanoparticles belong to metal nanomaterials with large specific surface area,high surface energy,excellent optical,electrochemical activity and catalysis properties,Which are widely used in the construction of biological and chemical sensors,detection of heavy metal ions,and catalysis field.Graphene oxide is a new type of carbonaceous nanomaterial.It is an important derivative of graphene.The surface is rich in oxygen-containing functional groups,which makes it have good hydrophilicity and biocompatibility.Because the graphene oxide has large specific surface area and can be functionalized,which composed of nanocomposites with metal nanoparticles has a greater application prospect,both can produce novel physical and chemical properties.It not only enriches the original intrinsic properties of the two nanomaterials,but also give it new features to the composite materials.In this dissertation,based on gold nanoparticles and graphene,three kinds of visualization sensors were constructed for the detection of heavy metal ions.The main contents ware summarized as follows:1.Citrate-stabilized gold nanoparticles were prepared by using chloroauric acid as a precursor solution,trisodium citrate as a reducing agent and stabilizer,followed by heating under reflux and stirring,and the solution shows wine red.The sensor has a obvious response to Cr³⁺,and the detection process can analyzed by naked eye observation and quantitatively by UV-visible absorption spectrum.There was a good linear relationship between the ratio of absorbance at 670 nm and 522 nm and the concentration of Cr³⁺ in the range of 0.15 ?M to 5.0 ?M.The limit of detection was calculated to be 0.20 ?M and the lowest concentration visible to the naked eye was1.0 ?M.The method has the advantages of simple operation,time saving,low cost,visualization of test results,high sensitivity and selectivity,and can be realised rapid detection of Cr³⁺in water samples.2.Based on the above study,using the catalytic properties of gold nanoparticles,graphene oxide?GO?as a matrix,polyethyleneimine?PEI?as a cross-linking agent,PEI and AuNPs were bonded to GO surface by chemical bond and coordination bond respectively to form Au/PEI/GO nanocomposites.First,the catalytic performance of Au/PEI/GO nanocomposites was researched and found it can catalyze the degradation of MB?methylene blue?from blue to colorless.More importantly,this nanocomposite has peroxidase-like activity,When Hg²⁺ is present,can be catalyzed the reaction of H₂O₂ with 3,3',5,5'-tetramethylbenzidine?TMB?in citric acid-disodium hydrogen phosphate buffer,lead to TMB from the colorless changed to blue.Therefore,Hg²⁺is detected by naked eye colorimetric methed,The naked eye detection limit of 10 n M,and the UV-vis detection linear range is 10⁶00 n M with a limit of detection was 0.47 n M.In addition,the sensor can be used for the detection of Hg²⁺in tap water and Yellow River water with a limit of detection of 10 n M,demonstrating good selectivity and sensitivity.3.From the above we can know,the nanocomposites formed by AuNPs and GO have more excellent properties.Therefore,in this chapter,both AuNPs and Fe₃O₄ NPs have different functional nanoparticles were attached to the surface of GO with coordination bonds to form Au/Fe₃O₄/GO nanohybrids.It was characterized by a series of analytical techniques.The experimental results show that the sensor achieves efficient detection of Hg²⁺ with a wide linear range?0.1⁴00 n M?and a lower detection limit?0.39 n M?.Because of the introduction of magnetic Fe₃O₄ NPs into the nanomaterials,make the Au/Fe₃O₄/GO nanohybrids has superparamagnetism,and can effectively remove Hg²⁺ adsorbed on the surface of AuNPs,and further realize the recycling of the nanohybrids material.