Detection Of Small Nitrogenous Molecules Based On Acetylene Black And Metal Nanocomposites Modified Electrodes

Clinically relevant endogenous small molecules and ions include neurotransmitters,metabolites,vitamins,amino acids,dietary minerals,and other small biomolecules.In this section,we proposed several strateges for the detection of small molecules and ions,as follows:(1)biological logands are used as recognation probes,such as antibodies,biological receptors,aptamers,MIPs,enzymes,enzyme-mimicking metalloproteins,coenzymes,whole cells,affinity ligands,double-stranded nucleic acids,DNAzymes,and ionophores in case of ion detection;(2)electrocatalytic materials are applied to enhance the response on the surface of electrodes;(3)using nanostructured interfaces to amplify the signal and subsequently improve the temporal resolution of the sensor.Combinations of some of these stratages are designed to improve the analytical performance of biosensors.These thesis focus on the investigation of nanomaterials applied on electrochemical sensors for the simultaneous determination of guanine and adenine in calf thymus DNA samples.Tryptophan and dopamine have also been determined.Furthermore,we discussed the reaction mechanism of these substances on the surface of sensor.Our main research and results in aspects are as follows:1.A novel electrochemical sensor for simultaneous detection of guanine(G)and adenine(A)was prepared based on acetylene black(AB)-graphene oxide(GO)/poly diallyldimethylammonium chloride(PDDA)functionalized gold nanoparticles(AuNPs)through self-assembly method on surface of glassy carbon electrode(GCE).The surface morphologies of different composite modified electrodes were characterized by scanning electron microscopy(SEM),which indicated that the as-synthesized PDDA-AuNPs were successfully dispersed on the surface of AB-GO composite.The electrochemical behaviors of G and A were studied by cyclic voltammetry(CV),indicating that the AB-GO/PDDA-AuNPs composite film exhibited high electrocatalytic activity towards oxidation of guanine and adenine.Its mechanism is that formation of ?-? stacking interaction and strong electrostatic adsorption accelerate the electron transfer.The differential pulse voltammetry(DPV)was used for the simultaneous determination of G and A in 0.10 mol/L PBS(pH=6.0).Good linear relationships were obtained between the peak currents and the concentrations of G and A in the ranges from 0.15 to 20.0 ?mol/L and from 0.20 to 30.0 ?mol/L,respectively their with detection limits of 24.70 nM and 43.80 nM.Thus,the modified electrode possessed good selectivity,reproducibility and stability,and the proposed method was also valuable and useful to simultaneous detection of guanine and adenine in calf thymus DNA samples.2.A novel electrochemical sensor for detection of L-tryptophan(L-Trp)was prepared based on AB-GO/Citric acid(CA)functionalized Ferroferric oxide nanoparticles(Fe3O4)through self-assembly method on surface of GCE.The surface morphologies of different composite modified electrodes were characterized by SEM,Energy spectrum and XRD,which indicated that the as-synthesized CA-Fe3O4were successfully casted on the surface of AB-GO composite.The electrochemical behaviors of L-Try were studied by cyclic voltammetry(CV),That the AB-GO/Fe3O4-CA composite film exhibited high electrocatalytic activity towards oxidation of L-Try.The ?-? stacking interaction and strong electrostatic adsorption accelerate the electron transfer.The differential pulse voltammetry(DPV)was used for the determination of L-Try in 0.10 mol/L PBS(pH=4.6).A good linear relationships was obtained between the peak currents and the concentrations of L-Try were obtained in the ranges from 0.2 to 120.0 ?mol/L,with detection limits of 1.0×10-7mol/L.Therefore,the modified electrode possessed good selectivity,reproducibility and stability,and the proposed method was also valuable and useful to detection of L-tryptophan in The pig serum samples.3.Magnetic ferroferric oxide nanoparticles were synthesized by hydrothermal synthesis method.In addition,respectively,the preparation of PDDA functionalizd Pt nanoparticles,Fe3O4,and Fe3O4-PDDA-Pt nanomaterials modified GCE are used for dopamine analysis with differential pulse voltammetry and cyclic voltammetry.We optimized aseries of conditions to improved the performance proposed sensors such as influence of the different decoration materials,pH,sweep speed,the concentration and distractions.Fe3O4-Pt-PDDA modified GCE showed the remarkable electrochemical response compared with bare GCE and Fe3O4 modified GCE.The surface morphologies of different composite modified electrodes were characterized by SEM and Transmission Electron Microscope(TEM)Under the best experimental conditions,The peak current increased linearly with the concentration of dopamine in the range from 3.2×10-8 to 4.48×10-6mol/L,with a detection limit of 1.0×10-8.