Application Of Electrochemical Sensor Based On Nanomaterials-ionic Liquid Composites

Electrochemical sensor using electrode as transducer element, which have theadvantage of nice selectivity, quick analysis speed, low in cost as well as easyminiaturization and automation. It is widely used in the fields of industry, agriculture,clinical medical and environmental analysis, and is becoming one of the most activeresearch fields in the analytical chemistry. The goal of the research work is theachievement of good stability and sensitivity of the electrochemical sensors by usingthe characteristics of nano-materials and ionic liquid. The studies are significant inorder to broaden the application range of ionic liquid and to enrich research content ofelectrochemical sensors. The main contents are as following:1. A novel composite membrane, comprising of nanosized manganese dioxides（nano-MnO₂） and ionic liquid1-butyl-3-methylimidazolium hexafluorophosphate（[BMIM][PF₆]）, was developed on the glassy carbon electrode （GCE） by way of thefilm forming of chitosan （CHIT）. The characteristics of the[BMIM][PF₆]/MnO₂/CHIT/GCE were studied by cyclic voltammetry andelectrochemical impedance spectroscopy （EIS）. EIS was applied to the detection ofthe target DNA according to the increase of the electron transfer resistance of theelectrode surface after the hybridization of the probe DNA with its complementarytarget DNA sequence. Under optimal conditions, the dynamic range for detecting thesequence-specific DNA of the Escherichia coli gene was from2.0×1013mol/L to2.0×106mol/L, and the detection limit was2.4×1014mol/L.2. A new [BMIM][PF₆]-MnO₂-CHIT/GCE modified electrode was fabricatedvia the film forming by chitosan （CHIT）, which was based on [BMIM][PF₆] andnano-MnO₂as modifiers. In Britton-Robinson buffer solution, the electrochemicalbehavior of baicalin at the modified electrode was studied. The cyclic voltammetry curves ofbaicalin at [BMIM][PF₆]-MnO₂-CHIT/GCE show a pair of sensitive and reversible redoxpeaks. The changes of the oxidation peak currents with baicalin concentration wereexamined by differential pulse voltammetry. The calibration curve was linear in theconcentration range of1.0×10-9～1.0×10-5mol/L, with a detection limit of1.0×10-10mol/L.3.[BMIM][PF₆]-MnO₂-CHIT/GCE modified electrode was fabricated. Theelectrochemical behavior and determination of ethamsylate （ETH） on the electrode were investigated by cyclic voltammetry and differential pulse voltammetry. The differentialpulse voltammetry peak current of ETH in [BMIM][PF₆]-MnO₂-CHIT/GCE showed goodlinear relationship in the range of ETH concentration of5.0×10-7⁵.0×10-4mol/L, with adetection limit of5.0×10-8mol/L.4. A novel nanocomposite, comprising of graphene sheet （GR） and ionic liquid1-butyl-3-methylimidazolium hexafluorophosphate （[BMIM][PF₆]）, was developed onthe glassy carbon electrode （GCE） for the simultaneous determination ofhydroquinone and catechol in0.10mol/L acetate buffer solution （pH5.0）. At theGR-[BMIM][PF₆]/GCE, both hydroquinone and catechol can cause a pair ofquasi-reversible and well-defined redox peaks. Under the optimized condition, thecathodic peak current were linear over ranges from5.0×107mol/L to5.0×105mol/Lfor hydroquinone and from5.0×107mol/L to5.0×105mol/L for catechol, with thedetection limits of1.0×108mol/L and2.0×108mol/L, respectively.