Syntheses Of Molybdenum-based Compound Composites And Their Applications In Electroanalytical Chemistry

Electrochemical sensor occupies an important place in analytical chemistry due to its many merits,such as small volume,low cost,rapid response,high sensitivity and strong anti-interference.Nanomaterials are widely used as electrode modification materials due to their large specific surface area and high catalytic activity,especially graphene,noble metal nanoparticles,transition metal oxides and sulfides.Three kinds of excellent electrochemical sensors,such as graphene-molybdenum dioxide,gold nanoparticles/graphene-molybdenum dioxide and gold nanoparticles/nitrogen doped graphene-molybdenum disulfide were designed and prepared based on the synergetic effect.The structure and morphology of chemical sensor was characterized in detail.The electrochemical performance was studied using cyclic voltammetry?CV?,electrochemical impedance method?EIS?,differential pulse voltammetry?DPV?,and chronometric Coulomb method.These sensors have been successfully used in determination of uric acid?UA?,dopamine?DA?and acetaminophen?AMP?.The thesis includes three aspects as follows:1.Reduced oxidized graphene?RGO?and molybdenum dioxide nanocomposites were prepared by thermalization.A novel RGO-MoO₂/GCE sensor was fabricated by dropping the modified material on glassy carbon electrode.The obtained sensor shows good electrocatalytic property toward the electrode reaction of DA and UA and their redox peaks can be well distinguished.As a result,these two analytes can be determined simultaneously with low detection limits of 0.68?mol/L?DA?and 1.06?mol/L?UA??S/N=3?,respectively.The proposed method is sensitive,rapid,accurate and selective,and can be employed for determining DA and UA in real samples.2.A novel electrochemical sensor Au NPS/RGO-MoO₂/GCE is prepared by a simple drop-casting and electrodeposition method.The sensor has good electrical conductivity and excellent electrocatalytic activity to DA and AMP.Based on excellent electrochemical performances of the sensors,a DPV method is developed for rapid and sensitive determination of DA and AMP with wide linear ranges of 0.6 to 260?mol/L?DA?and 0.05 to 320?mol/L?AMP?and low detection limits of 13 nmol/L?DA?and 7.2 nmol/L?AMP?.The developed method has been successfully applied in assay of commercially available Acetaminophen tablet and human urine samples with a satisfactory result.3.NRGO-MOS₂ nanocomposite was prepared by thiourea high temperature gasification method.NRGO-MOS₂ nanocomposite was modified on the electrode,and then gold nanoparticles were electrodeposited on the modified electrode to prepare a new Au NPs/NRGO-MOS₂/GCE electrochemistry sensor.The composite material shows good conductivity and excellent electrocatalytic activity,and has successfully achieved the simultaneous determination of AMP and DA.The method presents high sensitivity,good selectivity,stable performance and good application prospects.