Application Of Graphene-based Nanocomposites For Electrochemical Sensors

Due to the fast response,low detection limit,high sensitivity,and ease of operation,electrochemical sensor has become the most common detection device in the field of analytical chemistry.Electrode modified materials can effectively improve the selectivity and sensitivity of the sensor.Thus,the development of novel modified materials has been the most important research topic in the field of electrochemical sensors.Graphene,a two-dimensional(2D)sheet with hexagonal lattice,has attracted more attention owing to large specific surface area,high mechanical strength,superior electrical conductivity,and great biocompatibility.In recent years,graphene also serves as an ideal matrix material for the synthesis of functional composites,which not only preserves the excellent properties of individual components,but also introduces the synergetic effect into sensing system.Metalloporphyrin,an efficient mimetic enzyme,can optimize its structure and property by functionalization,leading to remarkable stability and catalytic activity.Combining the polymer with graphene can improve not only the stability of porphyrin but also the sensitivity and selectivity of the sensor.On the other hand,metal sulfides have better cycling stability than conducting polymers.And their application has become broader with the emergence of diverse morphologies.The pure nanostructure is usually aggregated during growth process,which not merely decreases the effective surface area but also greatly limits the electrochemical performance.Thus,graphene is used as a carrier to support the generation of nanostructures,contributing to preparing nanocomposite with different structure,controlled morphology and variable performance.These sensors based on the above nanocomposites exhibit enhanced sensing performances.In summary,this paper aims to fabricate the biosensors with graphene-porphyrin and graphene-metal sulfides composites for dopamine and glucose sensing.1.Linking with strong electron-withdrawing fluorine atoms,a starburst dendritic molecule,5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin iron(?)chloride(FeTFPP),is designed and synthesized.Subsequently,the FeTFPP polymer(poly(FeTFPP))is achieved via a simple electrochemical method.Here,the poly(FeTFPP)performs three functions:Electrochemical recognition(owing to the hydrogen bonding between the strongly electronegative fluorine atoms and dopamine(DA);Biomimetic microenvironment(owing to interaction between porphyrin core and DA);Electrocatalysis(owing to remarkable catalytic ability of iron(?)ion).A biomimetic sensor is constructed by the poly(FeTFPP)film and graphene(rGO)sheet(rGO-poly(FeTFPP))for DA sensing.Due to the synergetic effect between poly(FeTFPP)and rGO sheet,the obtained sensor exhibits wide linear range,excellent reproducibility,high stability,and great selectivity.2.Linking with the butoxycarbonyl(BOC)protection of proline,a new tailed metalloporphyrin,nickel(?)5-[4-N-(tert-Butoxycarbonyl)-L-prolinecoxylpropyloxy]phenyl-10,15,20-triphenylporphyrin(NiTBLPyP),is designed and synthesized.And the NiTBLPyP polymer(poly(NiTBLPyP))is achieved through the electrochemical polymerization.Subsequently,a noncovalent nanohybrid of poly(NiTBLPyP)with rGO sheet(rGO-poly(NiTBLPyP))was prepared for the ultrasensitive and selective detection of DA.The introduction of proline can tune the energy level and electronic structure,which effectively promote the catalytic process of dopamine.Furthermore,the synergetic effect between rGO and poly(NiTBLPyP)amplifies the electrochemical signals.Under optimum conditions,the proposed sensor shows a wide linear range of 0.01-200 ?M and a low detection limit of 1.40 nM.3.Copper sulfide nanoflakes-reduced graphene oxide(rGO/CuSNFs)composite is successfully synthesized via one-pot hydrothermal method and exploited as the electrode material for the fabrication of the non-enzymatic glucose sensor.Due to the combination of the advantages of CuSNFs and rGO sheet,the rGO/CuSNFs composite exhibits great current amplification and electrocatalytic activity towards glucose oxidation,effectively improving the sensitivity and selectivity of the sensor.The non-enzymatic glucose sensor shows wide linear range,low detection limit,great reproducibility,long-term storage stability and the excellent anti-interference ability.Furthermore,the sensor can be feasibly applied to detect glucose in real samples.4.Using GO and Bi(NO3)3·5H2O as the precursor,thioacetamide(TAA)as sulfur source and reducing agent,Bi2S3 nanorods anchored over GO sheets(rGO/Bi2S3)are successfully synthesized via a one-pot hydrothermal process,where in-situ generation of Bi2S3 nanorods and reduction of GO occurred simultaneously.Moreover,the controlled synthesis of rGO/Bi2S3 nanocomposite with tunable size is achieved by adjusting the dosage of GO.Because of the particular construction of as-prepared nanocomposite and the synergistic effect between rGO sheets and Bi2S3 nanorods,the rGO/Bi2S3 film can effectively accelerate electron transport and extend catalytic active sites,leading to the remarkable electrochemical performance for dopamine sensing.Under the optimum conditions,the sensor shows excellent sensitivity and selectivity toward the dopamine sensing.Furthermore,the sensor can be feasibly applied to detect glucose in human serum and urine samples.