Electrochemiluminescence Of CdS Quantum Dots And Its Synergistic Electrochemiluminescence With Ru(bpy)₃²⁺

Electrochemiluminescence(ECL)detection technique takes advantages including high-sensitivity,high-selectivity,simple equipment,excellent temporal and spatial controllability,and has been widely used in the field of analytical chemistry.Tris(2,2'-bipyridyl)ruthenium(II)(Ru(bpy)32+)is a kind of classical ECL reagents and Quantum dots(QDs)is a new-type of luminescent reagents.They all have advantages in ECL detection and possess high ECL intensity in different electrode potential.In order to explore the relationship between the two different light emitting materials,we mixed them up and studied the ECL characteristics of the hybrid system in this paper.And we explored interaction between them by different means and got the conclusion that QDs could enhance the ECL of Ru(bpy)32+.A new ECL method has been established for the determination of catechol in real samples and obtained satisfactory results.This paper consists of four chapters:(1)Synthesis and characteristic of CdS quantum dots and its ECL detection of L-cysteineSynthesized 3-mercaptopropionic acid(MPA)capped CdS QDs by hydrothermal method and morphology characteristics and optical properties were charactered by Transmission electron microscope(TEM),UV-vis spectrophotometer and fluorospectrometer.The ECL measurements were performed with MPI-A/B ECL analyzer and we found CdS QDs produce a strong,stable ECL signal in-1.4 V(vs Ag/AgCI).However,the signal could be quenched by gold nanoparticles(Au NPs)due to electrochemiluminescence energy transfer(ECL-ET)of QDs to Au NPs.L-cysteine(L-cys)can restore the ECL signal because of its capture of Au NPs,which interrupts the ECL-ET.This increase in ECL intensity depends on the concentration of L-cys and can be used for L-cys measurements.The detection limit was 1.6 nM(S/N=3).This method exhibited high sensitivity and selectivity toward L-cys in the presence of other amino acids and can successfully detect L-cys in real urine samples.(2)Enhancement of Ru(bpy)3z+-based electrochemiluminescence by CdS QDs and its applicationThe ECL behavior of CdS QDs-Ru(bpy)32+ system was studied and we found that CdS QDs can enhance the anodic ECL of Ru(bpy)32+ in the absence of other coreactant.The effects of several factors such as the acidity of buffer solution,concentration of CdS QDs and Ru(bpy)32+,scan rate were investigated.On the basis of quenching effect of catechol on the anodic ECL of the CdS QDs-Ru(bpy)32+ system,a new ECL method has been established for the determination of catechol in the range of 10-8 to 10-5 mol/L,the detection limit was 5.5 nM(S/N = 3).This method can be used in the detection of catechol in tea sample which get a satisfactory results.(3)The construction and application of CdS QDs/Ru(bpy)32+ ECL sensorFixed the luminescent material on the surface of electrode to form a sensor,which can not only save the reagents and improve the sensitivity,but also enable rapid on-line analysis.On the basis of third chapter,L-Cysteine was used as linking agent which could covalently conjugate to multiwalled carbon nanotubes(MWCNTs)and AuNPs via amide bond and Au-S bond,and then dispersing them in chitosan solution,which was mixed with Ru(bpy)32+,to obtain MWCNTs-cys-AuNPs/CHIT-Ru(bpy)32+ nanocomposites.And finally drop CdS QDs and nanocomposites on the surface of glass carbon electrode to form a new ECL sensor for catechol detection.By optimizing the experimental conditions,the proposed ECL sensor exhibited excellent assay performances in determination of catechol with a wide linear range(5.0×10-9?1.0×10-5mol/L),low detection limit(1.1 × 10-9 mol/L),good reproducibility and acceptable stability.