Fabrication and Application of Electrochemical Sensors Based on Surface Molecular-imprinting on Graphene-Carbon Nanotubes Composites

Author:Yang Li Te

Supervisor:zeng bai zhao


Degree Year:2017





Three-dimension(3D)graphene-carbon nanotubes(GN-CNTs)composites,constructed with one-dimension(ID)CNTs and two-dimension(2D)graphene sheets,have wide applications in supercapacitors,solar cells and catalysts due to their remarkable properties,such as high surface-to-volume ratio,good thermal/conductive characteristic and excellent catalytic activity.When combined with metal nanomaterials and ionic liquids(ILs),their catalytic activity,dispersibility and stability in solvents can be further improved,thus exhibit good application prospect in electrochemical sensors.Molecularly imprinted polymers(MIPs)can recognize template molecules,when they are used to construct electrochemical sensors,the selectivity can be improved.In this thesis,3D GN-CNTs based composites are adopted to modify glassy carbon electrode(GCE)and MIPs are used as recognition element to construct electrochemical sensors for the detection of several biological molecules containing hydroxy groups.The main contents are summarized as follows:1.Fabrication of molecularly imprinted graphene-carbon nanotubes composite film modified electrode for the determination of rutinA simple hydrothermal method was used to prepare 3D netlike graphene-carbon nanotube nanocomposites(GN-CNTs).The composite was coated on GCE and rutin imprinted polypyrrole was prepared by voltammetry on the modified GCE.The influences of mass ratio of GN and MWCNTs,the ratio of monomer to template and potential cycle number for electropolymerization on the response of the resulting sensor were explored.Meanwhile,the influences of pH of buffer solution and adsorption time were investigated and optimized.Under the optimal conditions,the linear response range of rutin was 0.01-1.0 μM,the detection limit was 5.0 nM(S/N = 3)and the sensitivity was 926μA/mmol·L-1·mm2.The sensor showed good sensitivity and selectivity and was successfully applied to the determination of rutin in food samples(i.e.buckwheat tea and orange juice).2.Electrochemical determination of eugenol using a netlike molecularly imprinted poly(p-aminothiophenol-co-p-aminobenzoic acids)film on ionic liquid functionalized graphene-carbon nanotubes composite modified electrodeNetlike graphene-carbon nanotubes-ionic liquid(GN-CNTs-IL)composite was synthesized by hydrothermal process,which could keep stable in water.Then a porous molecularly imprinted poly(p-aminothiophenol-co-p-aminobenzoic acid)film was prepared on the GN-CNTs-IL modified GCE by cyclic voltammetry.For the imprinting,the template molecule used was eugenol,the supporting electrolyte was 25 mM tetrabutylammonium perchlorate ethanol solution,and the concentration ratio of p-aminothiophenol and p-aminobenzoic acid was 1:3.After optimizing the preparation and measurement conditions,the obtained sensor showed a linear response to eugenol in the concentration range of 0.5-20 μM,and the limit of detection was 0.1 μM(S/N = 3).The sensor had good selectivity and 10-fold analogues(i.e.vanillin,methyl eugenol,paeonol and methyl isoeugenol)did not interfere with determination.In addition,it also displayed good reproducibility and practicability,and was successfully applied to detect eugenol in curry powder,perfume,and capsule samples.3.Fabrication of novel quercetin electrochemical sensor based on molecularly imprinted poly(para-aminobenzoic acid)on Pd NPs-porous graphene-carbon nanotubes compositeThe porous GO(pGO)was prepared by etching ordinary GO with KMnO4 and H2O2.Na2PdCl4 was introduced in homogeneous pGO-CNTs mixture and then pGN-CNTs supported Pd NPs was prepared through hydrothermal process.The Pd NPs/pGN-CNTs composite was characterized by transmission electron microscopy(TEM),N2 sorption isotherms,cyclic voltammetry,etc.The composite had large specific surface area,good electrocatalytic activity and conductivity.A quercetin(QR)imprinted electrochemical sensor was fabricated via electropolymerization of para-aminobenzoic acid(p-ABA)on the 3D Pd/pGN-CNTs modified GCE.The imprinting factor of QR was 3.14,which was higher than those of other five analogues.This indicated that the MIP sensor had stronger affinity to QR than toward other species.Owing to the synergistic effect of the Pd/pGN-CNTs and the molecularly imprinted poly(p-ABA),the electrochemical sensor presented high sensitivity and selectivity.The sensor was successfully applied to the detection of QR in real samples.In addition,theoretical calculations based on density functional theory(DFT)was conducted.The result indicated that there was strong hydrogen bond between the template(QR)and the monomer(p-ABA),and their combining mode was proposed.4.Preparation of Au NPs/graphene-carbon nanotubes-ILs-molecularly imprinted poly(3,4-ethylenedioxythiophene)composite for the electrochemical determination of resveratrol.Au NPs/GN-CNTs-ILs composites were fabricated by one-step hydrothermal method.The introduction of ILs made the size of Au NPs formed on GN-CNTs decrease,while it improved the dispersion of the composite in aqueous solution.Owing to the strong interaction between Au NPs and the S atoms in poly(3,4-ethylenedioxythiophene)(PEDOT),the MIP film stably adhered to the substrate.The addition of sodium dodecylbenzene sulfonate(SDBS)in the polymerization solution improved the solubility of the functional monomer and the template molecule in water,which facilitated the formation of molecularly imprinted film.The imprinted film prepared by such way had high stability and could be used repeatedly.The obtained sensor showed a linear response to eugenol in the concentration range of 0.10-10 μM with a limit of detection of 0.08μM(S/N = 3).The sensor was applied to the determination of resveratrol in red wine,blueburry jam,and peanut red skin samples,and the recoveries for standards added were 93.0-103%.5.Ionic liquid functionalized graphene-carbon nanotubes-AuPd alloy nanoparticles-molecularly imprinted copolymer composite for the electrochemical determination of paracetamolGN-CNTs supported AuPd alloy nanoparticles were prepared via one-pot hydrothermal method in the presence of IL(i.e.1-hydroxyethy 1-3-methyl imidazolium bis[(trifluoromethyl)sulfonyl]imide).The IL not only promoted the formation of small AuPd alloy nanoparticles,but also acted as a "spacer" to prevent the π-π stacking and aggregation of GN sheets and CNTs.The obtained AuPd/GN-CNTs-IL composite had large surface area and high electrocatalysis.The electrochemical sensor for paracetamol(PCM)determination was fabricated by electrochemical imprinting on AuPd/GN-CNTs-IL modified GCE,using carbazole and pyrrole as monomers.The PCM imprinted poly(carbazole-co-pyrrole)exhibited good recognition for PCM and had high stability.It presented a good linear response to PCM from 0.10 to 10 μM with a high sensitivity of 501 μA/mol·L-1·mm2.The sensor could be used for the detection of PCM in real samples.In addition,it was successfully applied to monitor the concentration change of PCM in urine from a patient with fever colds.