Research On Low-dimensional Carbon Nanomaterials Based Electrochemical Biosensors

Due to the characteristics of favorable selectivity,high sensitivity,rapid and exact analysis,easy operation and low cost,electrochemical sensors have been widely used in some fields,including environment monitoring,food detection and biomedical detection,etc.Carbon nanomaterials have excellent physical and chemical characteristics,which are beneficial to improve the micro-structure of electrode surface and have become a hotspot in the field of electrochemical sensors.Carbon nanomaterials can be combined with other materials and the composites further improve the properties of electrochemical sensors.In this work,four kinds of composites were prepared through combining low dimension carbon nanomaterials(carbon nanohorns and carbon nanodots)with other materials,and used for the construction of electrochemical sensors.Based on these sensors,electrocatalytic activities toward small biological molecules were furtherly studied.The main contents of this work were as follows:(1)A novel poly(2-aminopyridine)(PAP)/single walled carbon nanohorns(SWCNH)based sensor was successfully fabricated by electropolymerization method and studied by cyclic voltammetry and electrochemical impedance spectroscopy.Owing to the synergistic effect of PAP and SWCNH,as-prepared PAP/SWCNH/GCE showed excellent electrocatalytic activity towards H2O2.The currents showed a linear dependence on the concentration of H2O2 in the range of 5.0×10-5～8.0×10-3 mol L-1 and the detection limit was calculated as 3.6×10-6 mol L-1(S/N=3).(2)SWCNH was used as matrix in the preparation of phosphomolybdic acid(PMo12)by electropolymerization method and we prepared PMo12/SWCNH composite.As-prepared PMo12/SWCNH/GCE showed electrocatalytic activity towards oxidation of glucose at low oxidation potential and exhibited sensitive linear amperometric responses to glucose in concentration range of 3.5×10-5～4.0×10-3 mol L-1.The limit of detection was calculated as 2.4×10-6 mol L-1(S/N=3).(3)Cu2+ and ammonium tetrathiomolybdate were simultaneously reduced in one pot and subsequently as-prepared composite dried in air to obtain molybdenum disulfide-cuprous oxide(MoS2-Cu2O)composite,and carbon quantum dots(CQDs)were used for modified electrode due to the large specific surface area and good electron charge transfer properties.Based on MoS2-Cu2O composite and CQDs,we obtained MoS2-Cuu2O/CQDs/GCE,which showed electrocatalytic activity towards oxidation of nitrite.As-prepared electrode exhibited sensitive linear amperometric responses to nitrite in concentration range of 1.0×10-5～6.0×10-3 mol L-1.The limit of detection was calculated as 1.8×10-6 mol L-1(S/N = 3).(4)CQDs were used as matrix in the preparation of poly(β-cyclodextrin)(β-CD)by electropolymerization method and we prepared β-CD/CQDs composite.As-prepared β-CD/CQDs/GCE showed electrocatalytic activity towards oxidation of dopamine(DA),uric acid(UA)and tryptophan(Trp)at oxidation potential of 0.16,0.31 and 0.73 V,respectively,realizing the simultaneous determination of them in one system.As prepared modified electrode exhibited linear responses in the concentration ranges of 4.0×10-6～2.2×10-4 mol L-1 for DA,3.0×10-7～2.0×10-4 mol L-1 for UA and 5.0×10-6～2.7×10-4 mol L-1 for Trp,respectively.The detection limits were down to 1.4×10-7 mol L-1 for DA,1.0×10-8 mol L-1 for UA and 1.6×10-7 mol L-1 for Trp(S/N = 3),respectively.In summary,four kinds of modified electrodes,PAP/SWCNH/GCE,PMo12/SWCNH/GCE,MoS2-Cu2O/CQDs/GCE and β-CD/CQDs/GCE,were prepared in this thesis,and applied in electrochemical biosensors.As-prepared modified electrodes have the characteristics of high electro-catalysis,excellent selectivity and stability,which have promising prospects in electrochemical biosensors.