Study On Functionalized Polypyrrole Nanocomposites-based Electrochemical Sensors

Due to the good electrical conductivity,unique redox properties and biocompatibility of polypyrrole,it has received extensive attent:ion.However,the disadvantages of poor dispersion and single performance limit the application of polypyrrole materials in electrochemical sensing.In this paper chemical or electrochemical methods were used to prepare functionalized polypyrrole nanocomposites by increasing the specific surface area of the composites and enhancing their dispersibility,so as to improve their electrochemical sensing performance.In this paper,the glassy carbon electrode and nickel foam porous electrode were used as substrates of electrode,and functionalized polypyrrole nanocompounds were used as modified materials to construct heavy metal ion electrochemical sensors and bioactive small molecule?uric acid,hydrogen peroxide,glucose?electrochemical sensors applied to the analysis of real samples.The main contents and experimental results of this thesis include:?1?Application of phytic acid functionalized polypyrrole/graphene oxide nanocomposites in detection heavy metal ionBased on the high surface area of GO,the excellent electric conductivity of PPy and the chelating ability of phytic acid,phytic acid?PA?-functionalized polypyrrole/graphene oxide?PPy/GO?nanocomposites was investigated and a heavy metal ion?Cd?II?and Pb?II??electrochemical sensor was constructed.PPy/GO nanocomposites were synthesized by in situ chemical oxidation polymerization on GO to form sandwich structure of polypyrrole-oxidized graphene-polypyrrole.The PPy/GO nanocomposites were functionalized with phytic acid?PA?molecules by electrostatic attraction.The structural features of the fabricated nanocomposites were confirmed by transmission electron microscopy?TEM?,attenuated total reflection infrared?ATR-IR?spectroscopy and Raman spectroscopy.Based on the chelating ability of phytic acid,a modified electrode was prepared on the glassy carbon electrode for the electrochemical detection of heavy metal ions.The results showed that the PA/PPy/GO modified electrode exhibited high electrochemical performance compared with the PPy/GO and PA/GO modified electrodes.The developed sensor was used for the electrochemical analysis of various trace metal ions by differential pulse voltammetry?DPV?.The modified electrode demonstrated to measure Cd?II?and Pb?II?with a linear working range of 5-150 ?g L-1.?2?Uric acid electrochemical sensor based on polytetraphenylporphyrin/polypyrrole/graphene oxide nanocompositesAccording to the unique conjugate structure and electrochemical activity of porphyrin,the polytetraphenylporphyrin?p-TPP?,polypyrrole and graphene oxide composites were prepared to be applied to electrochemical analysis for uric acid?UA?.The PPy/GO nanocomposites were synthesized by in-situ chemical oxidation polymerization.Microspheres loaded with p-TPP were mixed into the PPy/GO nanocomposite,p-TPP/PPy/GO composites were obtianed.The differential pulse voltammetry is main analytical testing method.The study found that electrochemical responses of p-TPP/PPy/GO modified electrode increased with increasing UA concentration in the range from 5 to 200 ?M?detection limit is 1.15 ?M?.The electrochemical response to uric acid of p-TPP/PPy/GO modified electrode has been significantly improved compared to GCEs modified with p-TPP or PPy/GO only.The main reason is due to the synergy between the two aspects.PPy/GO nanocomposites have a high surface area and excellent electric conductivity.The micro-spheres of the p-TPP can hinder the agglomeration of the PPy/GO nanocomposites during the drying procedure and increased contact area between electrode and electrolyte.The results also demonstrate that the modified electrode exhibited good selectivity toward UA even in the presence of AA and DA.?3?The preparation of nitrogen-doped carbon nanowire/molybdenum disulfide nanosheet composites and their application in high-sensitivity detection of hydrogen peroxide release from living cellsPolypyrrole nanowires/molybdenum disulfide nanosheets?PPy NWs/MoS2?were synthesized by hydrothermal method,nitrogen-doped carbon nanowires/molybdenum disulfide nanosheets?CN NWs/MoS2?nanocomposites were prepared by sintering.Transmission electron microscopy?TEM?,X-ray diffraction?XRD?,Raman spectroscopy and Fourier transform infrared spectroscopy?FTIR?were used to characterize nanocomposites.The PPy NWs were transformed into nitrogen-doped carbon nanowires after calcining.The flake-like MoS2 was annealed and its edge active sites were significantly increased.This result contributed to improve the electrochemical catalysis performance of CN NWs/MoS2 nanocomposites toward H2O2.The research indicated the CN NWs/MoS2 modified electrode has a good catalytic performance toward H2O2 determination by chronoamperometry with a wide linear range from 2 to 500 ?M,and a low detection limit of 0.937 ?M?S/N=3?.In addition,the fabricated electrochemical biosensor performed monitoring of H2O2 released from living cells at a low applied potential,and would be applied to the clinical diagnosis.?4?Application of nickel foam supported Co₃O₄ nanosheets/polypyrrole nanowires heterostructures in glucose electrochemical sensingThe nickel foam?NF?was a substrate of electrode.Firstly,the polypyrrole nanowires?PPy NWs?and Co?OH?2 nanosheets were electrodeposited on the NF to obtain Co?OH?2/polypyrrole?Co?OH?2/PPy?nanocomposites.Then,nickel foame-supported Co₃O₄ nanosheets/polypyrrole nanowires?Co₃O₄/PPy?porous electrode was prepared by calcining.The PPy NW as core and the Co₃O₄ NS as shell constructed the hierarchical nanocomposites to form a three dimensional micro-nano structure in the micropores of NF.Chronoamperometry was used to evaluate the sensitivity of the sensor toward glucose.Compared with NF,PPy/NF and Co?OH?2/PPy/NF electrodes,the introduction of the Co₃O₄ NSs can provide a high surface area and increase the catalytic oxidation activity of the electrode to glucose,the Co₃O₄/PPy/NF electrode exhibited higher electrocatalytic activity for the oxidation of glucose.The proposed glucose sensor showed linear electrochemical responses to glucose range in 2 ?M-0.70 mM and 0.70 mM-5 mM with a low detection limit of 0.74?M?S/N=3?.In addition,the prepared biosensor revealed good selectivity in the presence of electro-active species such as D-fructose,uric acid,ascorbic acid and hydrogen peroxide,and provided an excellent platform for the determination of glucose in real samples.?5?Ni-Co-S/PPy core-shell nanohybrid on nickel foam as a non-enzymatic electrochemical glucose sensorThe PPy NWs were served as skeletons for electrodeposition Ni-Co-S nanosheets by cyclic voltammetry.The ternary Ni-Co-S NSs as the shell and PPy NWs as the core on the flexible NF constructed the 3D micro/nano structure applied to electrochemical detection for glucose.The introduction of the interconnected Ni-Co-S NSs can provide accessible pathways for electrolyte and have high sensitivity to glucose.Compared with the NF and PPy/NF electrodes,the Ni-Co-S/PPy/NF micro/nanohybrid electrode exhibited higher catalytic activity towards electro-oxidation of glucose.The developed Ni-Co-S/PPy/NF electrode showed two linear electrochemical responses to glucose in the range from 2 ?M to 140 ?M and 0.14 mM to 2 mM and the detection limit is 0.82 ?M.Furthermore,the prepared biosensor demonstrated high selectivity to glucose in the presence of uric acid,ascorbic acid and D-fructose.