Fabrication Of Novel Carbon/Ionic Liquid Electrode And Their Application In Bio/Chemical And Environment Analysis

Chemically modified electrode is the molecular design on the electrode surface, which fixs excellent chemical properties of molecules, ions, polymer design on the electrode surface. The electrode has a specific chemical and electrochemical properties, rich electrochemical electrode materials, extends the field of electrochemical research. It has been used in life science, analytical science, electronics, environmental science, energy science and materials science and other aspects. Focusing on some key issues of biosensors fabrication, how to immobilize biological component onto transducer surface with high stability and high activity, environment analysis, how to fast and sensitively determine heavy ions. This dissertation concentrated on the use of various materials and modification methods to prepare a series novel carbon ionic liquid electrode. Then, the fabricated electrochemical biosensors or sensor were applied to bio/chemical and environment analysis. Their structure, characteristics and performances have been investigated by electrochemical methods such as cyclic voltammetry (CV), current-time curve (i-t), square wave anodic stripping voltammetry (SWASV), and differential pulse voltammetry (DPV), technologies such as scanning electron microscopy (SEM), and transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), etc. The main points of this dissertation are summarized as follows:(1) A new kind of multiwall carbon nanotubes (MWCNTs) modified carbon ionic liquid electrode was constructed by multiwall carbon nanotubes (MWCNTs), graphite powder and ionic liquid n-octylpyridinum hexafluorophosphate (OPPF6). The optimal condition for MWCNTs, graphite powder and OPPF6composite preparation was selected as1:4:5(mass ratio). The electrochemical behaviors of the MWCNTs-CILE was investigated by using [Fe(CN)6]4/3-as probe and compared with carbon ionic liquid electrode (CILE). The results indicated that the novel composite electrode had a better response to H2O2, NADH and glucose due to its high catalytic performance of MWCNTs and the strong electronic transmission performance and collaborative catalysis of OPPF6.(2) A colloidal gold-modified carbon ionic liquid electrode was constructed by mixing colloidal gold-modified graphite powder with a solid room temperature ionic liquid n-octyl-pyridinium hexafluorophosphate (OPPF6). Glucose oxidase (GOD) was entrapped in this composite matrix and maintained its bioactivity well and displayed excellent stability. The effect conditions of pH, applied potential and GOD loading were examined. The proposed biosensor responds to glucose linearly over concentration range of5.0×10-6to1.2×10-3and2.6×103to1.3×10-2mol L-1, and the detection limit is3.5×10-6mol L-1. The response time of the biosensor is fast (within10s), and the life time is over two months. The effects of electroactive interferents, such as ascorbic acid, uric acid, can be significantly reduced by a Nafion film casting on the surface of resulting biosensor.(3) A novel glucose biosensor was fabricated through electropolymerization of biochemical preoxidized o-phenylenediamine and glucose oxidase on Prussian blue-modified carbon ionic liquid electrode. The Prussian blue-modified carbon ionic liquid electrode was shown good catalytic redox capability to H2O2. The effect conditions of pH and applied potential were examined. The proposed biosensor responds to glucose linearly over concentration range of5.0×10-6to2.1×10-3mol L with the detection limit of2.0×10-6mol L-1. The results were satisfactory.(4) A simple sensor based on bare carbon ionic liquid electrode was fabricated for simultaneous determination of dihydroxybenzene isomers in0.1mol L-1phosphate buffer solution (pH6.0). The oxidation peak potential of hydroquinone was about0.136V, catechol was about0.240V and resorcinol0.632V by differential pulse voltammetric measurements, which indicated that the dihydroxybenzene isomers could be separated absolutely. The sensor showed wide linear behaviors in the range of5.0×10-7-2.0×10-4mol L-1for hydroquinone and catechol,3.5×10-6-1.535xl0-4mol L-1for resorcinol, respectively. And the detection limits of the three dihydroxybenzene isomers were5.0×10-8,2.0×10-7,5.0×10-7mol L-1, respectively (S/N=3). The proposed method could be applied to the determination of dihydroxybenzene isomers in artificial wastewater, and the recovery was from93.9%to104.6%.(5) An8-hydroxy quinoline-immobilized bentonite (HQ-bentonite) modified carbon ionic liquid electrode (HQB-CILE) for the simultaneous determination of ultral-trace lead and cadmium was developed. The immobilization of8-hydroxy quinoline onto bentonite was carried out and the FT-IR spectroscopy was done to observe. Trace analysis of the selected heavy metals was performed by square-wave anodic stripping voltammetry (SWASV). The oxidation of two metals yielded well-defined, separated peaks. The peak currents at about-0.364V for Pb2+and-0.884V for Cd2+were measured. The affecting factors containing supporting electrolyte, pH of solution, accumulation time, deposition potential, amount of hydroxyapatite and possible interferences were investigated. The sensor exhibited linear behavior in the range of5.0×10-10-1.5×10-7mol L’for lead and cadmium (correlation coefficients:0.9955and0.9947, respectively) with detection limits of1.0×10-10mol L-1for lead and 2.Ox10-10mol L-1for cadmium. The results indicate that the sensor is sensitive and effective for the simultaneous determination trace of lead and cadmium.(6) A novel carbon ionic liquid electrode (CILE) modified with polythionine (PTh)/multi-walled carbon nanotubes (MWCNTs) composite was fabricated and used for the detection of the reduced nicotinamide adenine dinucleotide (NADH). The PTh/MWCNTs composite modified electrode was successfully prepared by electrochemical polymerizing of thionine in neutral media on the MWCNTs. The cyclic voltammetric response indicated that the PTh/MWCNTs/CILE was able to mediate the oxidation of NADH in phosphate buffer, with a low over potential0.03V. Amperometric experiment showed that sensitive and stable response of NADH could be obtained at PTh/MWCNTs/CILE within5s. The linear range for NADH determination was from0.8to422μmol L-1with a detection limit of2.6×10-7mol L-1(S/N=3). The wider linear range, lower detection limit and faster current response of the NADH implied that the new method combined PTh/MWCNTs composite with CILE should be of interest and potential for developing NAD+(the oxidation form of P-nicotinamide adenine dinucleotide)-dependent dehydrogenase enzymes based biosensors.(7) Cu nanoparticles/carbon nanotube/chitosan (Cunano/CNTs/CS) film was one-step electrodeposited onto the glassy carbon electrode (GCE), which fabricated a Cunano/CNTs/CS/GCE sensor to detect nitrite. One-step electrodeposition of CNTs and Cunano with the chitosan (CS) hydrogel was achieved, and the whole procedure takes only several minutes. Scanning electron microscopy (SEM) image demonstrated that the Cu nanoparticles coated on CNTs/CS were uniform, with an average size of30nm. The effects of Cu2+, CNTs and CS concentration in the mixture together with electrodeposition time and determination conditions such as applied potential, pH value on the current response of Cunano/CNTs/CS/GCE toward nitrite were optimized to obtain the maximal sensitivity. In addition, electrochemical experiments revealed that the modified electrode showed high electrocatalytic activity to the reduction of nitrite ion (NO2). The linear range for the detection of NO2was1.0×10-/M to2.5x10-3M, and the response was very fast (less than2s). A low detection limit of2.4×10-8M (S/N=3) for NO2-was achieved.