CN100410656C

CN100410656C - Method for preparing carbon nano-tube/poly L-cysteine composite modified glassy carbon electrode

Info

Publication number: CN100410656C
Application number: CNB2006100390722A
Authority: CN
Inventors: 王赪胤; 邵晓秋; 刘清秀; 杨功俊; 胡效亚
Original assignee: Yangzhou University
Current assignee: Yangzhou University
Priority date: 2006-03-21
Filing date: 2006-03-21
Publication date: 2008-08-13
Anticipated expiration: 2026-03-21
Also published as: CN1825105A

Abstract

The present invention relates to a method for preparing a composite decorative glass-carbon electrode from carbon nanotubes /polyL-cysteine, which comprises the following steps that firstly, after being purified, multi-walled carbon nanotubes are scattered in N, N-dimethylformamide solution, and then the scattered solution is dripped on the surface of the polished glass-carbon electrode and is dried by an infrared lamp; next, the glass-carbon electrode combined with the carbon nanotubes is placed in a solution containing L-cysteine-dilute hydrochloric acid so as to carry out electrochemical polymerization by the cyclic voltammetry; after the electrode polymerized with L-cysteine in a covalent way is taken out, the electrode is washed by secondary distilled water; thereby, the decorative electrode prepared from the carbon nanotubes/polyL-cysteine is obtained. The present invention has the advantages of easy electrode preparation, convenient experimental operation, high sensitivity and accuracy of measurement, good stability and repeatability, firm decorative layer of the electrode, and long service life; in addition, the cost of the electrode is low because the carbon nanotubes and the polyL-cysteine can be easily obtained with low price. Thereby, the electrode of the present invention is suitable for quickly testing the electrochemistry of uric acid and ascorbic acid in blood serum.

Description

The preparation method of carbon nano-tube/poly L-cysteine composite modified glass-carbon electrode

Technical field

The present invention relates to a kind of uric acid in the serum, dopamine, ascorbic acid preparation method of the carbon nano-tube/poly L-cysteine composite modified glass-carbon electrode of fast measuring simultaneously that realizes.

Background technology

Uric acid is the primary product of purine metabolism, and the undesired meeting of uric acid concentration causes numerous disease in people's body fluid, as gout, and antihyperuricemic etc.; The too high meeting of uric acid concentration causes renal failure and angiocardiopathy etc. in the blood.Therefore, the concentration of measuring uric acid in body fluid or the blood fast and accurately has very important significance in biological chemistry and clinical diagnosis.Clinically now enzyme connection colorimetric method for determining that adopt more, its advantage is a high selectivity, but is subjected to the influence of enzymatic activity, its poor stability, instrument cost an arm and a leg, sensitivity is low.Electrochemical determination is fast because of its speed, cost is low, sensitivity and accuracy advantages of higher have caused people's extensive concern.But in electrochemical rapid assay methods,, generally can't directly measure uric acid owing to be subjected to the interference of dopamine and ascorbic acid.

Carbon nano-tube has caused more and more researchers' interest since finding.Because the advantage of its uniqueness, the chemical stability as high conductivity, high-specific surface area, significant physical strength are become reconciled is widely used it in the fields such as electrode material of electroanalysis, nano electron device, battery.The electrode of having reported carbon nano tube type at present has carbon nano-tube carbon paste electrode [1], carbon nano tube modified solid electrode [2-3].L-halfcystine (cysteine) is one of important component of 20 kinds of basic protein of nature, has good electrochemical activity and biocompatibility.Because therefore its importance of compound in the life system caused researcher's interest.The L-halfcystine is one and contains the right molecule of zwitter-ion, be uniquely in 20 kinds of natural amino acids to have a sulfydryl (SH) compound of group, thereby thereby can make self-assembled modified electrode [4] with formation Au-S such as Au, Ag, Ag-S key, be used to measure Cobastab ₂, adrenaline etc.

The galvanochemistry modified electrode can reduce the overpotential of some redox material effectively, thereby reaches the purpose of separating or measuring simultaneously.Existing bibliographical information: Lin Xiangqin [5] unimolecular layer C-aminobutyric acid covalent modification glass-carbon electrode; Zare and Aguilar etc. [6-8] tetrabromo-p-benzoquinones decorating carbon paste electrode or multi-walled carbon nano-tubes gel mould modified glassy carbon electrode; Utilize carbon dust and PVC combination electrode can measure dopamine, uric acid and ascorbic acid simultaneously.But three's current peak resolution is limited in the existing method, and sensitivity is not high, and electrode preparation method is loaded down with trivial details, and the electrode modified material costliness is not easy to obtain, and biocompatibility is bad.So far also find no multi-walled carbon nano-tubes and L-halfcystine modified jointly in glass-carbon electrode and make the bibliographical information that composite modified electrode is used for measuring simultaneously uric acid, dopamine, ascorbic acid.

Summary of the invention

The objective of the invention is to provide a kind of and be used for fast, stable, sensitive, measure the preparation method of the carbon nano-tube/poly L-cysteine composite modified glass-carbon electrode of uric acid, dopamine, ascorbic acid exactly.

The technical scheme that the object of the invention realizes is, the preparation method of carbon nano-tube/poly L-cysteine composite modified glass-carbon electrode, be earlier with multi-walled carbon nano-tubes purified after, be scattered in N, in the dinethylformamide solution, then this dispersant liquid drop is added in the glass-carbon electrode surface of polishing, infrared lamp is oven dry down, glass-carbon electrode with the combined carbon nanotube places L-halfcystine-dilute hydrochloric acid solution to carry out electropolymerization with cyclic voltammetry again, the covalency polymerization electrode of L-halfcystine take out the back with the redistilled water flushing, make the carbon nano-tube/poly L-cysteine modified electrode.

Preparation method of the present invention has shown that carbon nano-tube is uniformly dispersed on the glass-carbon electrode surface, and carbon nano-tube and L-halfcystine the experiment proved that with covalent bonds, so decorative layer is quite firm.In liquid at the bottom of the dilute sulfuric acid, carry out voltammetric measuring, three well independently narrow shape volt-ampere peaks can appear in uric acid, dopamine, ascorbic acid on this modified electrode, and three's interspike interval differs successively and can reach 200mV, and peak resolution is higher than existing method.Three's peak current is than naked glass carbon in addition, and only carbon nano-tube-glass-carbon electrode increases obviously, and three's detectability also is higher than existing method simultaneously.The fast electrochemical that this electrode is directly used in uric acid in the serum, dopamine and ascorbic acid is measured, and the result is satisfactory, have fast, sensitive, stable, accurately, catalytic is high, electrode life is long.This electrode is applicable to the conventional determining of uric acid and ascorbic acid in the serum, for clinical analysis detection and medical diagnosis on disease provide a new way.Because carbon nano-tube and L-halfcystine are cheap and easy to get, so the electrode modified material cost is low, and its good biocompatibility; Be suitable for the analysis of various biological fluids.Simple, convenient experimental operation, quick that this electrode is made; The sample use amount is little, influences little to tested personnel; This method is measured sensitivity and accuracy height, has good stability and reappearance; The electrode modification layer is firm, and reach more than 6 months electrode life.

Description of drawings

Fig. 1 is sem photograph (XL-30E, ScanningElectron Microscopy, Philips, Netherlands) (surface topography map of carbon nano tube modified glass-carbon electrode) of carbon nano tube modified glass-carbon electrode;

Fig. 2 is sem photograph (XL-30E, Scanning Electron Microscopy, Philips, Netherlands) (surface topography map of carbon nano-tube/poly L-cysteine modified electrode) of carbon nano-tube/poly L-cysteine modified glassy carbon electrode;

Fig. 3 be that the x-ray photoelectron of carbon nano-tube/poly L-cysteine modified glassy carbon electrode can spectrogram (PHI-5300/ESCA, X-ray photoelectron spectroscopy, with Mg Ka as excitaton source);

Fig. 4 be the carbon nano-tube/poly L-cysteine modified glassy carbon electrode surperficial infared spectrum (IFS 66/S spectrometer, Bruker, Germany);

Fig. 5 is the differential pulse voltammogram of carbon nano-tube/poly L-cysteine modified glassy carbon electrode to uric acid, dopamine, ascorbic acid; Accumulating potential :+0.00V, enrichment time: 120s sweeps speed: 0.010Vs ^-1, pulse height: 0.050V, sensitivity: 1.0 * 10 ^-5AV ^-1, sweep limit: 0.0～1.0V, uric acid (UA) concentration is 4.0 * 10 ^-5MolL ^-1Dopamine (DA) concentration is 1.0 * 10 ^-4MolL ^-1Ascorbic acid (AA) concentration is 4.0 * 10 ^-4MolL ^-1, be contrast electrode with the saturated calomel electrode, platinum electrode is to electrode, end liquid: 0.05molL ^-1H ₂SO ₄(25 ℃).

Embodiment

The ultra-fine Al of 0.3 μ m, 0.05 μ m is used the glass-carbon electrode surface respectively in the pre-service of naked glass-carbon electrode ₂O ₃Suspending liquid polishes on silk, and ultrasonic cleaning five minutes in redistilled water then dries up stand-by at last with high pure nitrogen.

The purification process of carbon nano-tube places the dense HNO of 40mL with 10mg multiple-wall carbon nanotube (MWNCTs) ₃Middle stirring and refluxing 12h leaves standstill, and treats the CNT precipitation fully, the supernatant liquor that inclines, and the CNT precipitation is repeatedly washed with secondary water, shows pH neutrality until supernatant liquor.CNT is precipitated vacuum drying 24h.

The preparation of carbon nano tube modified electrode joins 10mL N with the multi-walled carbon nano-tubes of 1mg after the acidification, in the dinethylformamide (DMF), and ultrasonic dispersion 30min, (concentration is 0.1mgmL to obtain the solution of black homogeneous ^-1).Get 2 μ L carbon nano-tube dispersion liquids with microsyringe, drip, under infrared lamp, dry on the glass-carbon electrode surface of polishing.From the sem photograph (accompanying drawing 1 is described) of carbon nano tube modified electrode, carbon nano-tube being evenly distributed as can be seen on the glass-carbon electrode surface.

The preparation of carbon nano-tube/poly L-cysteine composite modified electrode places the glass-carbon electrode that is modified with carbon nano-tube to contain 0.0025molL ^-1The 0.04molL of L-halfcystine ^-1In the HCl solution, in-0.8V～2.2V (vs.SCE) potential range, with 200mVs ^-120 weeks of sweep velocity scan round (CHI660B electrochemical workstation, platinum filament is an auxiliary electrode, mercurous chloride electrode is a contrast electrode), take out then with the clean carbon nano-tube/poly L-cysteine modified electrode (MWCNTs/poly-L-cys/GCE) that promptly gets of redistilled water.From the sem photograph (accompanying drawing 2 is described) of this modified electrode clearly find out poly L-cysteine on the carbon nano tube modified electrode surface equably attached to carbon nano tube surface.This modified electrode is in 0.01molL ^-14 ℃ of refrigerators are preserved in the sulfuric acid.

The characteristic present of carbon nano-tube/poly L-cysteine composite membrane: as peak maximum on Fig. 3 is 399.46eV, show at electrode surface to be the combination of C-N key, this is consistent in the combination on glass-carbon electrode surface with bibliographical information amido cation radical, and L-halfcystine fixing on MWNTs/GCE also has been described simultaneously.The C=O stretching frequency of COOH group is at 1731cm as seen from Figure 4 ^-1, the stretching frequency of S-H is at 2387cm ^-1And 1159 and 1232cm ^-1It is respectively the stretching frequency of the NH-CH key of NH and tertiary carbon CH combination in C combines with N in the L-halfcystine in the glass-carbon electrode C-NH key and the L-halfcystine.Illustrate that carbon nano-tube and L-halfcystine are with covalent bonds, so decorative layer is firm.

With carbon nano-tube/poly L-cysteine composite modified electrode is that the three-electrode system of working electrode places the 20.0ml 0.05molL that contains uric acid, dopamine, ascorbic acid ^-1H ₂SO ₄In (25 ℃) end liquid ,+0.0V current potential stirring enrichment 120s, static then 30s, current potential is scanned up to+1.0V from 0.0V, adopts differential pulse voltammetry record i-E curve (accompanying drawing 5 is described), and the three goes out spike potential and is respectively UA:+0.71V; DA:+0.52V; AA:+0.32V.Go out spike potential and differ and reach about 200mV, peak resolution height is measured when being fit to the three.

Claims

1. the preparation method of a carbon nano-tube/poly L-cysteine composite modified glass-carbon electrode, it is characterized in that earlier behind the multi-walled carbon nano-tubes purifying, be scattered in N, in the dinethylformamide solution, then this dispersant liquid drop is added in the glass-carbon electrode surface of polishing, infrared lamp is oven dry down, the glass-carbon electrode that will be combined with carbon nano-tube again places and contains L-halfcystine-dilute hydrochloric acid solution and carry out electropolymerization with cyclic voltammetry, the covalency polymerization electrode of L-halfcystine take out the back with the redistilled water flushing, make the carbon nano-tube/poly L-cysteine modified electrode.