| Ionic liquids (ILs) are ionic compounds that consist of ions entirely,and exit in liquid state at ambient or even far below ambient temperatures.ILs have been widely used in the study of electrochemical sensors due totheir unique chemical and physical properties, such as good conductivity,high chemical and thermal stability, wide electrochemical windows etc.. ILscan be not only used as solvent and electrolyte but also used to modifyelectrodes. The sensor can be used in wide areas and have advantages atsensitive, productive etc.. In this thesis, the carbon ionic liquid electrode isconstructed by using pyridinium type ionic liquid as binder, which ismodified to apply in biological and environmental sensing. The creativeworks of this thesis are summarized as follows:1. A novel carbon ionic liquid electrode (CILE) modified withpolythionine (PTh)/multi-walled carbon nanotubes (MWCNTs) compositewas fabricated and used for the detection of the reduced nicotinamideadenine dinucleotide (NADH). The PTh/MWCNTs composite modifiedelectrode was successfully prepared by electrochemical polymerizing ofthionine in neutral media on the MWCNTs. The cyclic voltammetricresponse indicated that the PTh/MWCNTs/CILE was able to mediate theoxidation of NADH in phosphate buffer, with a low over potential 0.03 V.Amperometric experiment showed that sensitive and stable response ofNADH could be obtained at PTh/MWCNTs/CILE within 5 s. The linearrange for NADH determination was from 0.8 to 422μmol L-1 with adetection limit of 2.6×10-7 mol L-1 (S/N = 3). The wider linear range, lowerdetection limit and faster current response of the NADH implied that thenew method combined PTh/MWCNTs composite with CILE should be ofinterest and potential for developing NAD+(the oxidation form ofβ-nicotinamide adenine dinucleotide)-dependent dehydrogenase enzymesbased biosensors.2. Deoxyribonucleic acid (DNA) was electrochemically deposited on acarbon ionic liquid electrode (CILE) to give a biosensor with excellentredox activity towards paraquat as shown by cyclic voltammetry anddifferential pulse voltammetry. Experimental conditions were optimized with respect to sensing paraquat by varying the electrochemical parameters,solution pH, and accumulation time of DNA. Under the optimizedconditions, a linear relation exists between the reduction peak current andthe concentration of paraquat in the range from 5×10-8 mol L-1 to 7×10-5mol L-1, with a detection limit of 3.6×10-9 mol L-1. The utility of themethod is illustrated by successful analysis of paraquat in spiked real watersamples.3. A colloidal gold-modified carbon ionic liquid electrode wasconstructed by mixing colloidal gold-modified graphite powder with a solidroom temperature ionic liquid n-octyl-pyridinium hexafluorophosphate(OPPF6). Glucose oxidase (GOD) was entrapped in this composite matrixand maintained its bioactivity well and displayed excellent stability. Theeffect conditions of pH, applied potential and GOD loading were examined.The proposed biosensor responds to glucose linearly over concentrationrange of 5.0×10-6 to 1.2×10-3 and 2.6×10-3 to 1.3×10-2 M, and the detectionlimit is 3.5×10-6 M. The response time of the biosensor is fast (within 10 s),and the life time is over two months. The effects of electroactiveinterferents, such as ascorbic acid, uric acid, can be significantly reducedby a Nafion film casting on the surface of resulting biosensor.4. In this paper, a 8-hydroxy quinoline-immobilized bentonite modifiedcarbon ionic liquid electrode (HQ-B/CILE) for the simultaneousdetermination of lead and cadmium was developed. The 8-hydroxyquinoline-immobilized bentonite which combines with ionic liquid plays animportant role in remarkable responses of metals. The affecting factorscontaining supporting electrolyte, pH of solution, accumulation time,deposition potential, amount of hydroxyapatite and possible interferenceswere investigated. The sensor exhibited linear behavior in the range of0.5×10-9-1.5×10-7 mol L-1 for lead and cadmium (correlation coefficients:0.995 and 0.994, respectively) with detection limits of 1×10-10 mol L-1 forlead and 2×10-10 mol L-1 for cadmium. The results indicate that the sensoris sensitive and effective for the simultaneous determination of lead andcadmium. |
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