Preparation Of Canbon-based Nano-composites And Their Applications For The Detection Of Phenols In Electrochemical Sensors

In recent years,on account of its large surface area,high electrocatalytic activity and fast electron-transfer rate,nanomaterials have been highly appreciated from scholars in the field of science.Electrochemical sensors have become the most widely used analytical methods depended on its advantages of high sensitivity,low cost,easy operation and fast response.With the rising of nanotechnology and the further research on nanomaterials,it had every reason to use nanomaterials which modified on the surface of electrodes for the determination of phenolic substance by electrochemical sensors.Therefore,we synthesized carbon nanotubes(CNT-COOH),graphene oxide(GO),carbon nanocages(CNCs)and amine-functionalized metal organic framework(NH₂-MIL-125)and investigated the properties of these nanomaterials by various characterization methods in the paper.Then a simple hydrothermal reaction was chosen to prepare the composite materials between CNT-COOH and NH₂-MIL-125 or CNCs,GO and NH₂-MIL-125,and to explore the electrochemical performance of these composite materials.Finally,these composite materials were applied to detect phenolic substance by electrochemical sensors.The main research work are as follows:(1)NH₂-MIL-125/CNT-COOH composite was obtained by one-step reaction of CNT-COOH and NH₂-MIL-125,then immobilized on the surface of glassy carbon electrode(GCE)and designated as NH₂-MIL-125/CNT-COOH/GCE.Transmission electron microscope(TEM)was used to characterize the morphology of the materials,Raman spectra was used to study molecular structures,the X-ray diffraction(XRD)was carried out to investigate lattice structures,Fourier transform infrared(FTIR)spectra was recorded to study the major functional groups of the materials,and thermogravimetric analysis(TGA)was used to estimate thermal stabilities.Meanwhile cyclic voltammetry(CV),differential pulse voltammetry(DPV)and electrochemical impedance spectroscopy(EIS)were used to characterize the electrochemical properties of the electrode.The conductivity,sensitivity and electrocatalytic activity of the prepared electrochemical sensor showed a great improvement,due to the synergistic effect produced from the combination of excellent properties of two materials.Meanwhile,NH₂-MIL-125/CNT-COOH composite showed excellent selectivity,lower detection limits and a wider linear range for the simultaneous detection of catechol(CC)and hydroquinone(HQ).(2)A template method that employed Fe₃O₄ as a template and ethanol as a carbon source was used to synthesize the cubic structure of carbon layer coated Fe₃O₄ particles,and carbon nanocages(CNCs)were obtained after pickling and removing Fe₃O₄ particles.The composite(CNC/CNT-COOH)was further synthesized from CNCs and CNT-COOH.The structure characteristics and thermostability of composite was characterized by TEM,FTIR,XRD,Raman and TGA.CNCs/CNT-COOH/GCE modified electrode was obtained by immobilizing the composite on the surface of glassy carbon electrode.Meanwhile the electrochemical properties of composite was characterized by these electrochemical methods containing CV,DPV and EIS.The experimental results indicated that CNCs/CNT-COOH composite showed a higher conductivity with higher sensitivity,good linearity over a wide range of stability,and lower detection limit for electrochemical detection of bisphenol A.(3)A solvothermal reaction method for the preparation of nanocomposite(NH₂-MIL-125/RGO)was established from NH₂-MIL-125 and graphene oxide(GO).Then morphology,lattice structures,surface functional groups and thermal stability of composite was investigated by TEM,FTIR,XRD,Raman and TGA.The results showed that NH₂-MIL-125 was successfully modified on the surface of RGO.NH₂-MIL-125/RGO/GCE modified electrode was prepared by modifying the composite on the surface of glassy carbon electrode with a drop coating method,then electrochemical performance of the prepared electrode was studied by electrochemical method of CV,DPV and EIS.Under the optimal conditions,NH₂-MIL-125/RGO/GCE electrode manifested a good selectivity,lower detection limit and wide linear range for electrochemical determination of bisphenol A(BPA).Finally,NH₂-MIL-125/RGO/GCE showed a good results for the determination in real samples.