Construction And Application Of Electrochemical Biosensors Based On Carbon-based Nanomaterials And Precious Metals

Electrochemical biosensors involve the comprehensive utilization of subject knowledge such as chemistry,biology,physics and materials,and gradually develop detectors with high sensitivity,corresponding strength,short response time and low price.Nucleic acid or catalyst is used as a modified material.When the modified material reacts with the detection substance,it will cause changes in current,potential,resistance and accumulation to achieve the purpose of detection..Through the rise of carbon-based nanomaterials,especially the discovery of graphene,carbon dots,and carbon nanotubes,new solutions are provided.Biocompatibility,absorbed conductivity,and rich surface physical groups can be stably modified on the susceptor,providing a good substrate support for more and more stable ground-loading modification materials.The establishment of has attracted wide attention.In the end,noble metal nanoparticles have excellent electrocatalysis.Therefore,this paper combines the excellent conductivity of carbon-based nanomaterials with the catalytic activity of noble metals,and carried out the following work.1.Carboxylate-reduced graphene oxide?COOH-r GO?-based auxiliary signal amplification and duplex-specific nuclease?DSN?-assisted target recovery based on mi RNA-21?micro RNA-21?Ultra-sensitive detection.First,the aptamer?Capture DNA,c DNA?was modified on the surface of the gold electrode?GE?by Au-S bond.Second,COOH-r GO and the signal molecule Methylene blue?MB?self-assembled into the c DNA through?-?stacking and electrostatic interaction,respectively.The presence of COOH-r GO increases the specific surface area of the sensor,causing more MB to self-assemble on the electrode surface,which plays the role of signal amplification.When the target mi RNA-21 is present,it will hybridize with the c DNA to form a hybrid double-strand,triggering DSN to cleave the c DNA/mi RNA-21 hybrid double-stranded c DNA,and release mi RNA-21 to participate in the next round of hybridization.After DSN action,the length of the c DNA on the electrode surface becomes shorter,resulting in the weakening of the DPV signal of MB.Under the optimal experimental conditions,the detection range of mi RNA-21 0.05-5 f M,and the detection limit 0.01 f M.At the same time,the constructed electrochemical biosensor shows excellent selection even under similar mi RNA sequences.The electrochemical biosensor showed good applicability in the experiment of recovering the target mi RNA-21 from human serum samples,and achieved satisfactory results.2.Electrochemical biosensors of hydroquinone?HQ?and hydroquinone?CC?were constructed based on bimetal Pt Au nanoparticles modified carbon fibers?CF?.First,CF is sonicated with mixed acid?concentrated sulfuric acid and concentrated nitric acid?to obtain activated carbon fiber?ACF?.The activated carbon fiber increases the surface roughness,making the material easier to modify and stable.In order to enhance the catalytic performance,bimetal Pt Au was co-deposited by a metal precursor solution,so that the bimetal Pt Au nanoparticles were uniformly modified on the surface of the ACF.The ACF modified with bimetal Pt Au nanoparticles has good conductivity and good catalytic effect on HQ and CC,and realizes simultaneous detection of HQ and CC.Under the optimal experimental conditions,the detection limits for HQ and CC reach 0.280?M and 0.019?M,and they can be applied to the actual sample recovery experiments.3.Based on bimetallic Pt Pd nanoparticles and Ionic liquid-Carbon dots?IL-CDs?modified carbon fibers,an electrochemical biosensor based on hydrogen peroxide?H₂O₂?was constructed.First,using acetonitrile and ionic liquid?BMIMPF₆?as raw materials,IL-CDs were synthesized by bottom-up electrochemical method,and they were modified on the surface of ACF by electrodeposition.In order to test the catalytic performance,bimetal Pt Pd was electrodeposited by a metal precursor solution,thereby modifying the bimetal Pt Pd nanoparticles on the surface of IL-CDs/ACF.The ionic liquid molecule bridged on the surface of IL-CDs can provide sufficient binding sites for the nucleation of bimetallic Pt Pd nanoparticles and increase the nucleation rate of the metal,which helps to form on the IL-CDs/ACF assembly Dense and finer bimetal Pt Pd nanoparticles.Thanks to the assistance of IL-CDs to form denser and finer bimetal Pt Pd nanoparticles,it has excellent electrocatalytic performance for H₂O₂.Under the optimal experimental conditions,the detection range of H₂O₂ is 2-6561?M,and the detection limit is 0.29?M.It can also be applied to the recovery of actual samples of milk,serum,and urine.Sensitive detection of H₂O₂released in A549cells.4.Based on the ionic liquid-assisted formation of three-dimensional graphene nanosheets?Ionic liquid-reduced graphene oxide?IL-r GO?and carbon dots?CDs??modified carbon fibers,a dopamine?DA?electrochemical biology was constructed.sensor.First,graphene was electrodeposited on ACF using ionic liquid?[BMIM][BF₄]?as electrolyte,and ACF coated with 3D graphene nanosheets was prepared.Then CDs were further electrodeposited on IL-r GO/ACF.During the IL electrolyte electrodeposition process,the IL molecules were grafted onto the graphene nanosheets through the cation-?interaction between the imidazole ring of[BMIM][BF₄]and the?surface of graphene,thereby limiting the graphene nanometers.The restacking of the sheets promotes the formation of three-dimensional graphene nanosheet layers.The three-dimensional graphene nanosheets wrapped on the ACF not only have good electrical conductivity,but also provide a large specific surface area for the deposition of carbon dots.In addition,CDs have abundant carboxyl groups on the surface,which can interact with amine functional groups in DA through electrostatic interactions,improve the specificity of DA,and significantly enhance the redox reaction of DA.Under the optimal experimental conditions,the detection range of DA is 0.30-8.00?M,and the detection limit is13 n M.It can also be applied to the recovery of actual samples of serum and urine.