Electrospun Carbon Nanocomposites:Preparation And Applications In Organic Pesticides Sensors

With the widespread application of pesticides,the problem of pesticide residues has became the focus of attention.Therefore,the development of a fast and convenient detection method for pesticides is significance to human health.Electrochemical sensors were widely used in the quantitative analysis of pesticide residues due to their advantages of high sensitivity,fast response,low cost and good portability.Electrode materials is the key parameter in electrochemical sensors,so it is particularly important to develop electrode materials with simple preparation methods,low cost and high catalytic activity.Because of their excellent chemical stability,catalytic activity and biocompatibility,porous carbon,NiCo₂S₄ and TiC have received extensive attention in the field of electrochemical sensors.However,the problem of agglomeration makes its effective surface area reduced,resulting in a weakened electrochemical detection signal.Electrospun carbon nanofibers（CNF）has the advantages of large specific surface area and good conductivity.When nanomaterials are loaded onto CNF,they can effective solve the agglomeration phenomenon of nanomaterials,improving the conductivity and effective surface area of materials.In this thesis,porous carbon nanocomposite membranes（MHC/GCNF）,needle-shaped NiCo₂S₄ loaded graphitized carbon nanofibers（NiCo₂S₄/GCNF）and TiC nanoparticles（NPs）loaded CNF membranes（TiC/CNF）were prepared,and used to construct electrochemical sensors for the detection of organic pesticides,the specific contents are as follows:（1）Using electrospinning and hydrothermal-carbonization techniques,a porous graphitized carbon fiber membrane（MHC/GCNF）with three-dimensional self-supporting structure was prepared.The morphology and structure of MHC/GCNF were characteried by scanning electron microscope（SEM）,transmission electron microscope（TEM）,Raman（Raman）and X-ray electron spectroscopy（XPS）.The results showed that carbon whiskers on the fibers were hooked with each other,forming a bubble-like three-dimensional multi-level porous structure.Acetylcholinesterase（AChE）was loaded onto the MHC/GCNF to construct an electrochemical sensor for the detection of organophosphorus pesticides.Electrochemical results showed that the constructed sensor displayed a low detection limit（3.3 fM,S/N=3）and a wide linear range（0.01 pM-100 nM,R²=0.995）,and the sensor showed excellent stability and reproducibility.（2）Using a simple two-step hydrothermal method,a NiCo₂S₄ nanoneedle array anchored on electrospun graphitized carbon nanofiber（NiCo₂S₄/GCNF）with a three-dimensional porous structure was prepared and applied to the pesticide pyrimethanil（PMT）detection.Experiments showed that with the synergic effect of NiCo₂S₄ and GCNF,the oxidation peak current of PMT was enhanced,and the oxidation peak potential was also reduced.The sensor displayed good sensing performance,the linear range was 0.5-550μM（R²=0.999）,the detection limit was as low as 0.167μM（S/N=3）with good anti-interference ability.（3）TiC NPs-loaded carbon nanofiber films（TiC/CNF）was prepared by electrospinning and carbothermal methods.The morphology and structure of TiC/CNF were characterized by SEM,TEM and Raman techniques.The results showed that TiC NPs were well dispersed and tightly embedded in the CNFs framework.TiC/CNF was modified on the surface of GC electrode to construct an electrochemical sensor of pyrimethanil（PMT）.Electrochemical results showed that the oxidation peak current of TiC/CNF was enhanced,the linear range of TiC/CNF sensor was wide（0.1-600μM,R²=0.998）with low detection limit（33 nM,S/N=3）,showing good reproducibility and anti-interference.In addition,due to its good biocompatibility and excellent electrocatalytic capability,TiC/CNF can effective load AChE.It achieved excellent sensing performance,such as wide linear range（0.05pM-5000 nM,R²=0.998）and low detection limit（16.7 fM）.The electrochemical sensor also exhibited good stability and excellent anti-interference,and can be used for real sample detection.TiC/CNF was expected to become a new electrode material for the preparation of highly efficient sensors.