Preparation And Application Of Chitosan-Based Molecularly Imprinted Electrochemical Sensors

Molecularly imprinted polymers（MIPs）have strong specific recognition ability to template molecules and are suitable for constructing highly selective electrochemical sensors.However,traditional MIPs generally suffer from poor electrical conductivity,complicated preparation procedures,complex solvents and slow elution and enrichment,which affect their application to some extent.In order to improve the situation,researchers have tried different measures,including adopting new methods and reagents to prepare MIPs.Chitosan（CS）is a kind of cheap natural polymer with non-toxic and rich active groups.In recent years,it has attracted much attention as a functional monomer for preparing MIPs.CS-MIPs prepared by different methods show good performance.Nanomaterials have many excellent characteristics such as large specific surface area,strong electrical conductivity and good catalysis,thus they have huge potential in improving sensitivity and developing new electrochemical sensors.Here,nanomaterials are combined with CS-MIPs to construct rutin electrochemical sensors to improve the analytical performance of sensors.The main research contents are as follows:1.A rutin imprinted composite film modified GCE was prepared by simple mixing and then dripping,using chitosan as functional polymer,rutin as template molecule,glutaraldehyde as crosslinking agent and ionic liquid functionalized graphene-carbon nanotubes（GN-CNTs-IL）as the doping material.The composite and imprinted electrode were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and electrochemical technique.The influences of some factors affecting the performance of the imprinted electrode such as the amount of ionic liquid,the concentration of chitosan,the mass ratio of chitosan to rutin,the coating amount,the solution p H and the elution time,were explored.The experimental results showed that the molecularly imprinted composite had a porous structure and high electrical conductivity,GN-CNTs-IL exhibited obvious sensitization effect on the electrochemical sensing of rutin.Under the optimized conditions,the obtained MIP/GN-CNTS-IL/GCE sensor presented good response to rutin,with a wide linear detection range(i.e.0.01-200.0μmol L^-1),a low detection limit(i.e.6μmol L^-1),high selectivity,good reproducibility and stability.The sensor has been successfully applied for the detection of rutin in real samples.2.A molecularly imprinted polymer/Au nanoparticles-Mo S₂-graphene/GCE sensor was fabricated and used for the electrochemical detection of rutin.The rose-like Au nanoparticles-Mo S₂-graphene composite（Au NPs-Mo S₂-GN）was fabricated by a one-pot hydrothermal method.Graphene acted as an efficient matrix for the growth of Mo S₂nanoflower（NF）,and the edges of the Mo S₂NF subsequently loaded Au NPs.The Au NPs-Mo S₂-GN composite had large specific surface area,good conductivity and high catalysis,and showed excellent electrochemical response to rutin.To improve the selectivity,rutin imprinted chitosan film was electrodeposited on the Au NPs-Mo S₂-GN/GCE.The obtained molecularly imprinted sensor had strong adsorption capacity for rutin.Under the optimized conditions,the sensor showed a low detection limit(i.e.4 nmol L^-1)and a wide detection range(i.e.0.01-45.0μmol L^-1).It also displayed high stability and selectivity.When the sensor was applied to the determination of rutin in real samples satisfactory results were achieved.The strategy can also be applied to the preparation of electrochemical sensors for other polyhydroxyl substances.