Nitrogen-doped Carbon-based Materials And Conducting Polymer For Electrochemical Sensors

Electrochemical sensors as relatively common electrochemical detection devices in the field of analytical detection have the merits of rapid response,simple operation,portability and low cost.Selecting appropriate modified materials can improve the performance of sensors in many aspects including detection limit,sensitivity,selectivity and stability.Therefore,the development of novel electrode materials to construct electrochemical sensors is a crucial research topic in the field of analytical sensing.Owing to their advantages of abundance,low cost and outstanding chemical stability,carbon materials have received much attention in many research fields.However,the intrinsic catalytic activity of carbon materials cannot meet the demands of sensors.It is vital to modify carbon materials in order to endow them with new physicochemical properties and promote the catalytic abilities.The incorporation of heteroatoms into the carbon framework can not only alter the conductivity of the materials,but also increase the electrocatalytic capability and stability.In comparison with carbon atoms,the N atoms which possess an extra valence electron and more electronegativity have been widely used to prepare heteroatom-doped carbon materials,since it can effectively regulate the charge distribution of carbon frameworks,induce the production of active sites and increase the electron transfer efficiency.Furthermore,the transition metal-based carbon materials obtained by introducing extra transition metal into the N-doped carbon can integrate the advantages of N atoms and transition metal,which can not only enrich the structure of carbon materials,but also promote the electron transfer capability and electrochemical sensing performance.On the other hand,the stability is an important indicator to measure the performance of sensors.Compared with coating approach,the electrode modified by electrochemical polymerization of small organic molecules has higher stability.Conducting polymer is a kind of conductive macromolecules with conjugated structure.Under the application of external electric field,electrons can undergo directional migration in the backbone of polymer,leading to the conductivity of polymer.The merits of conducting polymer include excellent electrochemical activity,high conductivity,favorable biocompatibility and stability,which are the characteristics required in the field of sensing.Based on the above analysis,conducting polymer can be utilized to modify the surface of the electrode via electrochemical polymerization method,which can improve the performance of the sensor in terms of conductivity,stability and sensitivity.Therefore,this paper focuses on the construction of electrochemical sensors with N-doped carbon materials and conducting polymer for the detection of hydrogen peroxide（H₂O₂）,dopamine（DA）and DNA bases.Works of this paper are as follows:1.Three-dimensional（3D）N-doped porous carbon nanosheets（3D-NS）were synthesized via a one-pot pyrolysis using glucose and melamine as raw materials.In this process,melamine can serve as the precursor for the formation of sheet-like graphitic carbon nitride（g-C₃N₄）,an N-rich raw material and a pore-forming agent.The incorporation of N atoms can effectively regulate the charge distribution of sp² carbon,induce the structural defects and improve the electron transfer rate.As a result of above features,the 3D-NS based electrochemical sensor can be applied to sensitively detecting H₂O₂.In addition,the electrochemical sensor displays excellent performance in the determination of H₂O₂ in human serum samples,demonstrating a promising prospect for the detection of H₂O₂ in real samples.2.The melamine cyanurate（MC）aggregates were prepared through the intermolecular self-assembly,and then mixed with glucose and Co（NO₃）₂ to fabricate cobalt nanoparticles（Co NPs）embedded in walnut-like N-doped porous carbon microsphere（Co@NCS）by pyrolysis and acid etching.The large specific surface area,porous architecture and high conductivity of Co@NCS could boost the diffusion of electrolyte,supply more active sites and accelerate the electron transfer.Simultaneously,the peroxidase-like activity of Co NPs can promote the electrocatalytic activity toward H₂O₂.Co@NCS-based sensing platform has decent sensitivity and selectivity.The obtained sensor can be used to determine H₂O₂ in human serum samples and released from living cells,revealing the potential applications in the field of physiological sensing.3.Core-shell structured ZIF-L@ZIF-67 was synthesized at room temperature using two-dimensional（2D）leaf-like ZIF-L as confined growth template.Co,N co-doped carbon composite material（Co@NCNTs/NC）can be obtained after one-step thermal annealing and acid etching of ZIF-L@ZIF-67.The obtained composite material not only has the mixed-dimensional architecture which composed of one-dimensional（1D）carbon nanotubes and 2D porous carbon sheets,but also possesses the advantages of high surface area,excellent conductivity and enormous active sites.The electrochemical sensor based on Co@NCNTs/NC creates a signal amplification platform for the electrochemical detection of DA and can be feasibly applied to sensitively determine DA content in human serum samples.4.A novel electrochemical sensor based on 2-（4-bromophenyl）-1-phenyl-1H-phenanthro[9,10-d]-imidazole（PPI）is fabricated by a one-step electrochemical method.The bromophenyl group can expand the planar structure of the PPI,induce theπ-conjugated extension and enhance the capability of charge transfer.The phenyl group at N1 position could modulate the intermolecular interaction.Due to the extendedπ-conjugation structure,interaction with the bases viaπ-πinteractions and cross-link microwire-like skeleton,the electrochemical sensor designed with conducting polymer（poly（PPI））can be applied in simultaneous determination of DNA bases with well-separated peak potentials.Moreover,poly（PPI）/GCE can be examined by detecting bases in fish sperm samples with high accuracy.