Fabrication of Carbon-Based Micro-and Nanocomposites and Electrochemical Applications

Author:Niu Xue Liang

Supervisor:sun wei


Degree Year:2018





Carbon-based micro-and nanomaterials are carbon materials deriving from different carbon sources with micro-and nano-scale structures.Graphene(GR)is a new kind of two dimensional carbon material with only one-atom thickness.Porous carbon is a three dimensional(3D)material with micro-and nano-structures.Currently,graphene-based nanomaterials are widely used in the construction of various electrochemical sensors,endowing the electrode with increased specific surface area,rich active sites and excellent electrochemical catalytic activities.However,nanomaterials tend to accumulate,which limits the excellent properties.Fabrication of three-dimensional graphene(3DGR)can not only solve the problem of easy agglomeration of graphene(GR),but also can be used as a carrier for compounding with nanomaterials,exerting their advantages and synergistic effects,and improving the performance of the modified electrode.In addition,the biomass porous carbon(BPC)can also be used as a nanomaterial carrier to prepare BPC-nanomaterial composites due to its rich micro-nanoscale channels and large specific surface area.Uniform distribution of nanomaterials are achieved by preparation of 3DGR and BPC based composites.Performance of the electrode modified with the composites can be effectively improved.This thesis mainly focuses on the preparation of GR,3DGR,BPC and their nanocomposites,the fabrication of novel modified electrodes,and their applications in electrochemical biosensor and detection of flavonoids.1.A nanosensing electrode was constructed with gold nanoparticles(Au NPs)and GR as modifiers and traditional stainless steel acupuncture needle(AN)as substrate electrode(GR/Au NPs/AN),which was applied to sensitive determination of rutin.The electrode modification process was achieved through stepwise electrodeposition of Au NPs and GR on AN surface.The morphology and characteristics of GR/Au NPs/AN were investigated by scanning electron microscopy(SEM)and electrochemical techniques.Voltammetric behaviors of rutin on the as-explored sensing platform were carefully studied with the electrochemical parameters calculated.Electrochemical quantitative method for rutin determination was further established by good linearity between the oxidation peak currents and rutin concentrations with two sections(0.08~10.0 μmol/L and 20.0~200.0 μmol/L)and alow detection limit(0.025 μmol/L,3S0/S).This GR/Au NPs/AN was used to the detection of rutin in tablet and human urine samples.2.A three-dimensional reduced graphene oxide aerogel(3D-r GA)with excellent porous framework was synthesized via one-step hydrothermal technique.The characteristics and performances of 3D-r GA were checked by SEM,Transmission electron microscopy(TEM),Brunner-Emmet-Teller(BET),X-ray diffraction(XRD),Raman,Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS)and electrochemical methods,which exhibited good properties including unique porous structure,large surface area and excellent conductivity.3D-r GA was further used as the modifier on carbon ionic liquid electrode(CILE)to construct a modified electrode,which was applied to sensitive and selective determination of quercetin.Electrochemical responses of quercetin were accelerated with a pair of symmetrical cyclic voltammetric peaks in good shape appeared and the electrochemical parameters were calculated.The sensitive oxidation response of quercetin from differential pulse voltammetry(DPV)was verified.Under the selected conditions,electroanalysis of quercetin was established by plotting the oxidation peak currents against quercetin concentrations with linear regression analysis.A wider linear range from 0.1μmol/L to 100.0 μmol/L was obtained with a detection limit of 0.065 μmol/L(3S0/S).This as-explored approach could be successfully utilized for quercetin detection in Ginkgo tablets.3.Pt nanocrystal decorated 3DGA was synthesized via a one-step hydrothermal method with the morphology and structure characterized by SEM,TEM,XPS,XRD,Raman and BET.Then a new modified electrode was fabricated with Pt-3DGA-horseradish peroxidase(HRP)suspension and Nafion solution coated on CILE.The performances of Nafion/Pt-3DGA-HRP/CILE were further checked by various methods with the well-maintained 3D structure,good retention of bioactivity of HRP and the enhanced electrochemical ability.Direct electrochemistry of HRP was investigated with a pair of well-shaped redox peaks appeared at-0.307 V(Epc)and-0.229 V(Epa)and the peak-to-peak separation was 78 m V.Electrochemical parameters including electron transfer coefficient(α)and heterogeneous electrode reaction rate constant(ks)were calculated to be 0.52 and 3.35 s-1.Electrocatalytic activity of Nafion/Pt-3DGA-HRP/CILE towards the reduction of trichloroacetic acid(TCA)was checked in detail,and wide detection range of 0.5~42.0mmol/L was obtained by plotting the catalytic peak currents against TCA concentrations.Nafion/Pt-3DGA-HRP/CILE could be successfully utilized for the analysis of TCA contents in real samples.4.Au-Ag-3DGA with good three-dimensional pore structure was synthesized through one-step hydrothermal method.The characteristics and performances of Au-Ag-3DGA were characterized by SEM,TEM,BET,XRD,Raman,XPS and electrochemical methods.Au-Ag-3DGA was decorated on CILE surface to obtain a new modified electrode(Au-Ag-3DGA/CILE),which was applied to investigate the electrochemical behaviors of baicalein.Electrochemical behaviors of baicalein were accelerated with the oxidation peak current increased and the electrochemical parameters such as α and ks were calculated as 0.58 and 3.066 s-1.The sensitive oxidation response of baicalein from DPV was verified.A novel electrochemical method for baicalein analysis was established by plotting the oxidation peak currents against quercetin concentrations with three linear sections of 1×10-4 ~ 1×10-2 μmol/L,1×10-2 ~ 0.1 μmol/L and 0.1 ~ 10.0 μmol/L obtained,accompanied with a low detection limit of 0.065 μmol/L(3S0/S).This as-explored approach could be successfully utilized for quercetin detection in Ginkgo tablets.5.BPC was prepared by calcination technique with banyan leaves as carbon source,and then Au NPs-BPC was prepared by hydrothermal method.The morphology,structure and composition of Au NPs-BPC were characterized by SEM,TEM,XRD,Raman and XPS techniques.The results show that BPC has good micron-sized pores with Au NPs evenly anchored on the surface.Au NPs-BPC was further used to construct a functional interface of the modified electrode,which was used to investigate the electrochemical behaviors of luteolin.The electrode reaction mechanism was studied with α and ks calculated as 0.51 and1.99 s-1.The peak currents are linearly with luteolin concentrations in two sections of 0.15 ~1.8 μmol/L and 1.8 ~ 10.0 μmol/L,with a detection limit of 0.07 μmol/L(S0/S).This method could be successfully utilized for quercetin detection in Duyiwei capsules.