Fabrication And Application Of Electrochemical Sensors Based On Low-dimensional Carbon And Its Composite Nanomaterials

In recent years,low-dimensional carbon nanomaterials,such as one dimensional carbon nanotubes and two dimensional graphene,have become the hot topics in materials and other disciplines due to their unique structures and physical,chemical properties such as ultra-larger surface area,excellent thermal conductivity and electrical conductivity.They also have been developed as indispensable framework materials in a new generation of sensors except widely used in the field of energy storage,supercapacitors.Functionalized nanocomposites based on low-dimensional carbon materials with other materials are utilized to construct electrochemical sensors with high sensitivity,simple operation,fast response,good selectivity and low detection limit.The excellent properties and synergic effects of the components in composites must be considered during the preparation of electrochemical sensors.It is of great significance in basic research and practical application.In this paper,we utilized several methods to design and fabricate novel stable and sensitive electrochemical sensing platforms based on graphene and its derivatives,carbon nanotubes with other materials such as conducting polymers,amino acids,carbon nitride and so on.These sensors were used for the determination of many species,such as environmental pollutants,biological molecules,organic pharmaceutical molecules,energetic materials,and glucose.Analytical performance of these sensors were evaluated.This research work includes the following six parts:(1)Electrochemical determination of 4-nitrophenol at a poly(carbazole)/N-doped graphene modified glassy carbon electrodePolycarbazole(PCZ)/nitrogen-doped graphene(N-GE)composite was prepared by electropolymerization of carbazole on the N-GE modified glass carbon electrode(N-GE/GCE)for fabricating a novel electrochemical sensor for 4-nitrophenol(4-NP).The redox behavior of 4-NP at a PCZ/N-GE/GCE was investigated by cyclic voltammetry,compared with the bare GCE,reduced graphene oxide(RGO),N-GE and PCZ modified GCEs.The results indicate that all modified electrodes show the enhanced reduction peak currents.However,the PCZ/N-GE/GCE exhibits the highest peak current and most positive reduction potential of 4-NP.It reflects the PCZ/N-GE composite has the best electrocatalytic activity to 4-NP.The reduction peak current was linear with the concentration of 4-NP in the range of 8×10-7?2×10-5 M with the detection limit of 0.062 ?M(3S/N).The sensor based on PCZ/N-GE/GCE was also applied to the detection of 4-NP in real water samples.(2)Simultaneous detection of dopamine and uric acid using a poly(L-lysine)/graphene oxide modified electrodeA novel,simple and selective electrochemical method was investigated for the simultaneous detection of dopamine(DA)and uric acid(UA)on a poly(L-lysine)/graphene oxide modified glassy carbon electrode(PLL/GO/GCE)by differential pulse voltammetry(DPV).Compared to other modified electrodes,the PLL/GO/GCE exhibited an increase in the anodic potential difference and a remarkable enhancement in the current responses for both UA and DA.For the simultaneous detection of DA and UA,the detection limits of 0.021 and 0.074 ?M were obtained,while 0.031 and 0.018 ?M were obtained as the detection limits for the selective detection of UA and DA,using DPV in the linear concentration ranges of 0.5 to 20.0 and 0.5 to 35 ?M,respectively.The proposed modified electrode was successfully implemented in the simultaneous detection of DA and UA in human blood serum,urine and dopamine hydrochloride injection with satisfactory results.(3)Simultaneous determination of acetaminophen and dopamine using an in-situ polymerization of L-lysine and graphene oxide modified electrodeA poly(L-lysine)-graphene oxide(PLL-GO)composite was synthesized via in-situ polymerization of monomer L-lysine and GO to modify glassy carbon electrode(GCE).Electrochemical behaviors of acetaminophen(AP)and dopamine(DA)at the PLL-GO/GCE were thoroughly studied by cyclic voltammetry and DPV.The DPV peak currents increased linearly with their concentrations in the range from 1.0 to 10.0 ?M,10 to 40.0 ?M for DA and 2.0 to 40.0 ?M for AP,respectively.The lower detection limits were found to be 0.21 ?Mfor DA and 0.11 ?M for AP,respectively.The proposed modified electrode was successfully implemented in the concentration detection of DA and AP in pharmaceutical samples and blood serum.The obtained results were found to be satisfactory.(4)NTO sensor based on a glassy carbon electrode modified with porous C3N4 and multi-walled carbon nanotubes compositesThree kinds of carbon nitride with different morphologies were prepared by different methods and characterized by the transmission electron microscopy,scanning electron microscopy,X-ray photoelectron spectra,Fourier transform infrared spectroscopy and BET.The composite combining porous C3N4(m-CN)and multi-walled carbon nanotubes(MWCNT)was used to modify GCE by casting procedure.The GCE modified with m-CN/MWCNT showed excellent electrocatalytic activity to the reduction of 3-nitro-1,2,4-triazol-5-one(NTO)compared with the other composites(such as b-CN-MWCNT and CNNs-MWCNT).The enhanced catalysis activity is contributed to the larger surface area of m-CN and the synergic effect of m-CN and MWCNT.Under optimum conditions,the reduction peak current of NTO was linear with the concentration in the range of 0.8-150 ?M with the detection limit of 0.017?M.The modified electrode also had good selectivity without the interference of other energetic materials.(5)One-pot fabrication of graphitic-N-rich nitrogen-doped graphene:Application in determination of acetaminophen for enhanced electro-redox activityGraphitic-N-rich nitrogen_doped graphene was synthesized by hydrothermal reducing of graphene oxide with doping agent 2-aminopyridine.High resolution Nls spectra illustrated that pyridine-N,pyrrole-N,and graphitic-N are the main N states.The as-synthesized nitrogen-doped graphene with high content of graphitic-N showed the higher electro-catalysis activity than graphitic-N-free nitrogen-doped graphene towards the redox of acetaminophen,suggesting graphitic-N are crucial active sites.And it was devoted in the determination of acetaminophen with a detection limit of 0.38 ?M.(6)Amperometric nonenzymatic determination of glucose based on nickel and nitrogen doped grapheneNickel nanoparticles modified glassy carbon electrode(Ni/GCE)and Nickel/nitrogen doped graphene modified GCE(Ni/N-GE/GCE)were developed by using an electro-deposition method at a constant potential.Nickel hydroxide/N-doped graphene modified GCE(Ni(OH)2/N-GE/GCE)was fabricated by cyclic voltammetry.The kinetics and electrocatalytic reaction mechanism of glucose at the different kinds of modified electrodes were explored.The results show that the Ni(OH)2/N-GE/GCE displays the highest electrocatalytic activity towards the oxidation of glucose solution compared with the Ni/GCE and Ni/N-GE/GCE.