Study On Melamine Electrochemiluminescence Sensors Based On Ru?bpy?₃²⁺-Doped Silica Nanoparticles

Electrochemiluminescence?ECL?which combined of electrochemistry and chemiluminescence has been widely used in food safety due to its good stability and high sensitivity.As a famous luminophor,Ru?bpy?₃²⁺has been vastly applied and the immobilization of Ru?bpy?₃²⁺onto the electrode has become attractive in ECL studies.In this paper,Ru?bpy?₃²⁺was embedded in silica nanoparticles thus formed Ru?bpy?₃²⁺-doped silica nanoparticles?RUDS?to reduce the consumption of Ru?bpy?₃²⁺.And then,RUDS was combined with functional multi-walled carbon nanotubes?CMWCNTs?with good conductivity and molecularly imprinted polymer?MIP?with specific recognition ability to improve the sensitivity and selectivity of ECL sensors,respectively.Based on the sensitization effect of MEL to the ECL of Ru?bpy?₃²⁺,two new types of solid phase ECL sensors with RUDS/CMWCNTs and RUDS/MIP modified electrodes have been built to detect melamine?MEL?rapidly and sensitively.The main contents include the following parts:In chapter 1,the development process,features and basic principles of ECL and molecular imprinting technology and the detection methods of MEL were introduced briefly;in addition,the progress of Ru?bpy?₃²⁺on solid state ECL research were elaborated in detail.In chapter 2,a new type of MEL ECL sensor was set up by RUDS/CMWCNTs/Nafion modified glassy carbon electrode.RUDS were prepared by the reverse microemulsion method.In this chapter,as the Ru?bpy?₃²⁺molecules can be well fixed in Si-O-grid structure,the stability of the sensor was greatly improved,moreover,by the good conductivity of the CMWCNTs,the sensitivity of the MEL sensor was enhanced.The effect of the pH of buffer solution,scan rate,the concentration and the amount of mixture modified on the electrode were investigated.Under the optimization of experimental conditions,the linear range obtained by the RUDS/CMWCNTs/Nafion modified electrode was from 5×10^-13 mol L^-1to 1×10^-7 mol L^-1 with a correlation coefficient of 0.9951,and the distinguished detection limit?S/N=3?was 1×10^-13 mol L^-1.The method was applied to the detection of MEL in milk with the spiked recoveries ranging from 99%to 102%.In chapter 3,a MEL sensor with high selectivity and high sensitivity was built by coupling extraction effect of molecular imprinting technique and high sensitivity of ECL method.In this work,MEL MIP was prepared by precipitation polymerization method with MEL as the template molecule.Due to the large amount of specific binding sites,MEL can be enriched from the solution to electrode surface.Modifying electrodes with RUDS and MEL MIP,a new type of MEL ECL sensor was fabricated.The effect of the pH of buffer solution,the electrode incubation time,the concentration and the amount of mixture modified on the electrode were investigated.Moreover,the selectivity and the reusability of the sensors were studied in the experiment.Under the optimization of experimental conditions,the ECL signals exhibited a good linear response to the logarithmic MEL concentration ranging from 1×10^-12 to 1×10^-7 mol L^-1?r=0.9964?with a distinguished detection limit?S/N=3?of 1×10^-13 mol L^-1.In conclusion,we used CMWCNTs and MIP as the sensitive element to build two types of MEL ECL sensors with high sensitivity and selectivity,respectively.These sensors were applied to detect MEL in milk samples with satisfactory spiked recoveries.