| Pesticides play an important role in guaranteeing crops yield.However,as highly toxic chemicals,the unscientific and irrational use of pesticides will pose serious problems.Therefore,it is of great necessity to realize the real-time,accurate and rapid detection of pesticide residues in the environment.As the real-time detection method,electrochemical biosensors are promising alternatives which can replace traditional pesticides detection techniques.It is noteworthy that the electrode interface is the soul of the electrochemical sensing system,various multifunctional electrode materials have been designed and facricated,which can not only satisfy the steady immobilization of biomolecules,but also render the electrochemical sensor the best electrochemical performance,sensing property and long-term stability.Transition metal oxides（TMOs）have aroused extensive research enthusiasm as electrode modification materials due to their low cost and high catalytic activity.The mainly purpose of this thesis is to improve the electrochemical performance of TMOs via three aspects:the design of TMOs morphology,the regulation of TMOs components and the construction of TMOs heterogeneous structures.Meanwhile,electrochemical acetylcholinesterase biosensors based on these modified TMOs are constructed,the influences of the modified TMOs on electrode interface properties and the catalytic principle are explored.These biosensors with better pesticide detection performance,stability and anti-interference ability are supposed to meet the requirements of the field real-time pesticides monitoring.The research details and achievements are as follows:（1）Octahedral Cu O with porous and hollow structure was designed and synthesized.Comparing with big Cu O nanocrystals,the surface of the octahedral Cu O was composed of a large number of small Cu O nanoparticles,which endowed the octahedral Cu O with ultra-high hydrophilicity,electrical conductivity and catalytic activity.Together with the conductive mesoporous carbon,the ACh E-CS/PO-Cu O NPs-400/MCs/GCE electro-chemical sensor was constructed.Benefiting from the unique porous hollow structure of the octahedral Cu O,as well as its hydrophilic and electrochemical properties,the sensor exhibited an extremely low ATCh detection voltage（0.25 V）and excellent anti-interference capability compared to other ACh E sensors（0.65 V）.The Km value for the catalytic reaction to ATCh was 215μmol/L,indicating that the porous hollow and hydrophilic Cu O could effectively maintain the biological activity of ACh E.Ultimately,the detection range and detection limit of ACh E-CS/PO-Cu O NPs-400/MCs/GCE to methamidophos were 3.54×10-13～7.09×10-7 mol/L and 4.85×10-14 mol/L;for monocroto-phos,they were 4.48×10-13～4.48×10-7 mol/L and 1.07×10-14 mol/L;and for fenitrothion,they were 3.61×10-13～3.61×10-7 mol/L and 1.80×10-14 mol/L.（2）3D peony like M-Co3O4（M=Ni,Fe,Cu）structured by porous ultra-thin two-dimensional nanosheets was successfully developed by regulating the components of bimetallic TMO.The 3D structural M-Co3O4（3DH-Co Ni-O NSs）with good structural stability showed excellent electrochemical catalytic activity and electrical conductivity in contrast to pristine Co3O4.The in-plane pores and the open channels of M-Co3O4 not only provided convenient paths for material transmission,but also provided a very large active area and outstanding conductivity for the developed electrochemical sensing interfaces.Coupling with the conductive and biocompatible graphdiyne,the ACh E-CS/GDY/3DH-Co Ni-O NSs/GCE electrochemical sensor was developed,which showed the strongest response current to ATCh.The Km value of the enzyme reaction of the sensor was 119μmol/L,indicating that the immobilized ACh E on bimetallic TMO still held good catalytic activity and high affinity to the substrate.Due to the special porous three-dimensional structure of the M-Co3O4 electrode materials,the electronic modulation resulting from the introduction of doped metal atoms,and the synergistic effect between the composites,the biosensor displayed better detection sensitivity(detection limits were 3.6×10-13 mol/L for dipterex and 3.3×10-14 mol/L for omethoate,respectively)and wide detection range(dipterex:3.88×10-12 to 3.88×10-6 mol/L;omethoate:4.69×10-13 to 4.69×10-7 mol/L)than those reported in the literatures.（3）The"sandwich"structural mixed TMO of Mn Ox@Ce O2@N-C nanowires with high catalytic activity and high stability were successfully fabricated.Due to the heterogeneous interface between Mn Ox skeleton and Ce O2 nanoparticles,the valence state ratio of Ce was readjusted to make it more catalytic active.The presence of N-C in the outer layer avoided the agglomeration of Ce O2 nanoparticles,stabilizing their morphology and catalytic activity.Thus,the enzyme electrochemical sensor modified with Mn Ox@Ce O2@N-C achieved the fastest enzyme-substrate equilibrium,and the smallest Km value（91μmol/L）of enzyme-catalyzed ATCh reaction.Under the optimal conditions,the ACh E-CS/Mn Ox@Ce O2@N-C/GCE electrochemical sensor was used to detect two typical carbamate pesticides,the detection range of carbaryl was 5×10-14～1×10-7 mol/L,and the detection limit was 1.05×10-14 mol/L,while the detection range of carbofuran was1×10-13～1×10-7 mol/L,and the detection limit was 8.09×10-14 mol/L.In addition,the sensor owned a good recovery rate（92%～106%）in the actual sample analysis. |
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