CN104897765A - Method for detecting hydrogen peroxide and nitrite by electrochemical sensor based on dual-metal porphyrin coordination polymer - Google Patents

Abstract

A method for detecting hydrogen peroxide and nitrite with an electrochemical sensor based on a double metalloporphyrin coordination polymer, using a double metalloporphyrin coordination polymer CoTCPP-Cu or a CoTCPP-Cu/CNTs composite modified electrode as the work The electrode uses chronoamperometry to detect hydrogen peroxide or nitrite; the CoTCPP-Cu is a coordination polymer formed by self-assembly of bimetallic Co, Cu and tetrakis-(p-carboxyphenyl)porphyrin. The electrochemical sensor adopted in the method of the present invention is an amperometric sensor, has unique bimetallic activity, has the advantages of high sensitivity, simple detection method and wide application range, and the detection limit of hydrogen peroxide can reach 5.0×10 ^-7 M, the detection limit of nitrite can reach 2.5×10 ^-6 . The detection method of the invention has the characteristics of fast on-site detection, high sensitivity, low cost and the like.

Description

Method for detecting hydrogen peroxide and nitrite with electrochemical sensor based on double metalloporphyrin coordination polymer

technical field

The invention relates to an electrochemical detection method, in particular to a method for detecting hydrogen peroxide or nitrite with an electrochemical sensor based on a double metal porphyrin coordination polymer.

Background technique

Coordination polymers are a class of organic-inorganic hybrid materials that link metal ions or clusters with organic ligands through coordination bonds. , gas storage and separation, optical materials, magnetic materials, etc. (see: (a) SR Batten, SM Neville, DR Turner, Coordination Polymers: Design, Analysis and Application, 2008. (b) Chemical Society Reviews, 38 (2009 ).).). However, there are few studies on the use of coordination polymers as electrocatalysts for electrosensing (see: (a) Zhang, W., Wang, LL, Zhang, N., Wang, GF, Fang, B., 2009 .Functionalization of Single-Walled Carbon Nanotubes with CubicPrussian Blue and Its Application for Amperometric Sensing.Electroanalysis 21(21), 2325-2330.(b)Zhou, B., 2012.Co ^II /Zn ^II -(L-Tyrosine)Magnetic Metal-Organic Frameworks. European Journal of Inorganic Chemistry.).

Metal-porphyrin coordination polymers use metalloporphyrins as ligands (building blocks, skeleton parts) because of their biocompatibility and are used in biomimetic catalysis (see: (a) Liu, J.Y., et al. , Comparative study onheme-containing enzyme-like catalytic activities of water-soluble metalloporphyrins. Journal of Molecular Catalysis a-Chemical, 2002.179 (1-2), 27-33. (b) Vago, M., et al., Metalloporphyrinization: electropolymerization quartz crystal microgravimetric studies. Journal of Electroanalytical Chemistry, 2004.566(1), 177-185.). Metalloporphyrins are a class of conjugated ring compounds with stable π bonds, so they have properties such as light, electricity, catalysis, and biomimetic properties (see: (a) Kosal, M.E., et al., A functionalzeolite analogue assembled from metalloporphyrins.Nature Materials, 2002.1(2), 118-121.(b) Shultz, A.M., et al., A Catalytically Active, Permanently Microporous MOF with Metalloporphyrin Struts. Journal of the American Chemical Society, 2009.131(12), 4204-4205.(c ) Sheldon, R.A., Metalloporphyrins in Catalytic Oxidations. Marcel Dekker, 1994.). Therefore, metal-porphyrin coordination polymers are functional materials with excellent application prospects, and have potential advantages in both electrochemical and biological related fields.

Electrochemical sensors based on metal-porphyrin coordination polymers have not been reported yet. The detection of substances related to important biological processes (such as hydrogen peroxide) and nitrite in food has been an important topic in analytical chemistry, including electroanalytical chemistry. The electrochemical detection of hydrogen peroxide and nitrite involves electrocatalytic reduction and oxidation, respectively, and there are few reports on dual-functional electrochemical sensors using different active sites to detect different substances. (See: (a) Ammam, M., Easton, E.B., 2012. Novelorganic-inorganic hybrid material based on tris(2,2′-bipyridyl) dichlororthenium(II) hexahydrateand Dawson-type tungstopphosphate K-7H4PW 18O62center dot 18H(2 )O as a bifuctionalhydrogen peroxide electrocatalyst for biosensors. Sensors and Actuators B-Chemical 161(1), 520-527. (b) Bai, Y.H., Zhang, H., Xu, J.J., Chen, H.Y., 2008.Relationship between Nanostructure and Electrochemical/Biosensing Properties of MnO(2)Nanomaterials forH(2)O(2)/Choline. Journal of Physical Chemistry C 112(48), 18984-18990.).

Contents of the invention

The purpose of the present invention is to provide a method for detecting hydrogen peroxide or nitrite with an electrochemical sensor based on a double metal porphyrin coordination polymer.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A method for detecting hydrogen peroxide or nitrite with an electrochemical sensor based on a double metalloporphyrin coordination polymer, characterized in that the method uses an electrochemical sensor based on a double metalloporphyrin coordination polymer as a working An electrode for detecting hydrogen peroxide or nitrite by chronoamperometry;

The electrochemical sensor based on double metal porphyrin coordination polymers includes a base electrode, and the surface of the base electrode is modified with double metal porphyrin coordination polymers or double metal porphyrin coordination polymers/carbon nanotubes. Complex; the double metal porphyrin coordination polymer is meso-5,10,15,20-tetra-(p-carboxyphenyl) porphyrin double metal coordination polymer (CoTCPP-Cu), which is a double metal A coordination polymer formed by self-assembly of Co, Cu and tetrakis-(p-carboxyphenyl)porphyrin (TCPP) has the following structure

In the formula, CoTCPP is four-(p-carboxyphenyl) cobalt porphyrin;

where metal Co coordinates with the four Ns at the center of the tetrakis-(p-carboxyphenyl)porphyrin, and each metal Cu coordinates with the oxygen in the carboxyl groups from the four tetrakis-(p-carboxyphenyl)porphyrins, Each carboxyl group undergoes bidentate coordination with two metal Cus.

In the electrochemical sensor, the base electrode is preferably a glassy carbon electrode.

In the electrochemical sensor, the carbon nanotubes include single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs).

Described electrochemical sensor adopts following method to prepare:

CoTCPP-Cu is ultrasonically dispersed in deionized water to form a suspension, which is drip-coated on the surface of the base electrode and dried; then drip-coated with nafion solution on the electrode surface and dried to obtain the electrochemical sensor (CoTCPP -Cu modified electrode, denoted as electrochemical sensor-I).

Or, first drop-coat the carbon nanotube suspension on the base electrode and dry it, then drop-coat the CoTCPP-Cu suspension on the electrode surface and dry it; then drop-coat the nafion solution on the electrode surface and dry it , to prepare the electrochemical sensor (CoTCPP-Cu/CNTs modified electrode, denoted as electrochemical sensor-II).

The electrochemical sensor is based on double metal porphyrin coordination polymer CoTCPP-Cu, which is an amperometric sensor. The incorporation of carbon nanotubes can significantly improve its electrical sensing performance. The method of the invention adopts that the sensor has bimetallic activity, has unique redox bimetallic bifunctional electrochemical catalytic activity, and has good electrochemical sensing performance for the reduction of hydrogen peroxide and the oxidation of nitrite.

Specifically, according to the method of the present invention, the method for detecting hydrogen peroxide based on the electrochemical sensor comprises the following steps:

(1) prepare the described electrochemical sensor based on double metal porphyrin coordination polymer;

(2) chronoamperometry (i-t) measures the standard curve of hydrogen peroxide

Prepare hydrogen peroxide standard solution, use the electrochemical sensor based on the double metal porphyrin coordination polymer as the working electrode, the platinum electrode as the auxiliary electrode, and the saturated calomel electrode as the reference electrode to form a three-electrode system. Under the detection potential, the i-t curve of the hydrogen peroxide response current is obtained by chronoamperometry, and the i-c standard curve is obtained by drawing or linear regression;

Preferably, the detection potential is -0.20V～-0.55V, and the optimum working potential is -0.25V.

(3) Detection

Under the same conditions as step (2), perform electrochemical detection on the detection sample, read the response current, and calculate the hydrogen peroxide concentration according to the i-c standard curve.

According to the method of the present invention, the method for detecting nitrite based on the described electrochemical sensor comprises the following steps:

(1) prepare the described electrochemical sensor based on double metal porphyrin coordination polymer;

(2) Chronoamperometry (it) measures the standard curve of nitrite

Prepare a nitrite standard solution, use the electrochemical sensor based on the double metal porphyrin coordination polymer as the working electrode, the platinum electrode as the auxiliary electrode, and the saturated calomel electrode as the reference electrode to form a three-electrode system. Under the detection potential, the i-t curve of the nitrite response current is obtained by chronoamperometry, and the i-c standard curve is obtained by drawing or linear regression;

Preferably, the detection potential is 0.70V-0.95V, and the optimum working potential is 0.85V.

(3) Detection

Under the same conditions as step (2), perform electrochemical detection on the detection sample, read the response current, and calculate the nitrite concentration according to the i-c standard curve.

Beneficial effects of the present invention: According to the method for detecting hydrogen peroxide or nitrite of the present invention, the electrochemical sensor based on the metal-porphyrin coordination polymer has unique bimetallic electrocatalytic activity, and is a dual-functional electrochemical sensor. Chemical sensor with good electrocatalytic performance for substances such as hydrogen peroxide and nitrite. To further improve the performance of the sensor, the electrochemical sensor-II was prepared by metalloporphyrin coordination polymer/CNTs composite. The invention detects hydrogen peroxide or nitrite by electrochemical sensing technology, which solves the problems of slow detection speed, high cost and complicated operation in the current detection of hydrogen peroxide and nitrite in food, environment and industry, and has the advantages of The detection speed is fast, the sensitivity is high, and the cost is low.

The present invention will be described in detail below in conjunction with specific embodiments. The protection scope of the present invention is not limited by the specific embodiments, but by the claims.

Description of drawings

Figure 1 is the XRD spectrum of the double metalloporphyrin coordination polymer CoTCPP-Cu, including the XRD spectrum of the planar structure (marked with circles) and the XRD spectrum of interlayer spacing (marked with squares).

Fig. 2 is the infrared spectrogram (FTIR) of the double metal porphyrin coordination polymer CoTCPP-Cu.

Fig. 3 is an ultraviolet (UV) spectrogram of the double metalloporphyrin coordination polymer CoTCPP-Cu.

Fig. 4 is a transmission electron micrograph (A) and a scanning electron micrograph (B) of the double metalloporphyrin coordination polymer CoTCPP-Cu.

Fig.5 Cyclic voltammogram of electrochemical sensor-I, panel A: (a) bare glassy carbon electrode, without hydrogen peroxide; (b) bare glassy carbon electrode, 0.5mmolL ^-1 hydrogen peroxide; (c) electrochemical Sensor-I, without hydrogen peroxide; (d) Electrochemical sensor-I, 0.5 mmolL ^-1 hydrogen peroxide; Figure B: (a) bare glassy carbon electrode, without sodium nitrite; (b) bare glassy carbon electrode, 0.25 mmolL ^-1 sodium nitrite; (c) Electrochemical sensor-I, without sodium nitrite; (d) Electrochemical sensor-I, 0.25 mmolL ^-1 sodium nitrite.

Fig. 6 (A) Electrochemical sensor-I is to the current response figure of hydrogen peroxide at constant potential-0.25V, and the inset is the graph of current response to hydrogen peroxide concentration; (B) Electrochemical sensor-I is to sodium nitrite at The graph of the current response at a constant potential of 0.85 V, the inset is a plot of the current response versus the concentration of sodium nitrite.

Fig.7 Cyclic voltammogram of electrochemical sensor-II, panel A: (a) MWCNT-modified glassy carbon electrode without hydrogen peroxide; (b) MWCNT-modified glassy carbon electrode, 0.5mmolL ^{- 1} hydrogen peroxide; (c) Electrochemical sensor-II, without hydrogen peroxide; (d) Electrochemical sensor-II, 0.5 mmolL ^-1 hydrogen peroxide; Figure B: (a) Multi-walled carbon nanotubes modified glassy carbon Electrode, without sodium nitrite; (b) Multi-walled carbon nanotube modified glassy carbon electrode, 0.5mmolL ^-1 sodium nitrite; (c) Electrochemical sensor-II, without sodium nitrite; (d) Electrochemical sensor-II , 0.5mmolL ^-1 sodium nitrite.

Fig. 8 (A) Electrochemical sensor-II is to the current response diagram of hydrogen peroxide at constant potential -0.25V, the inset is the graph of current response to hydrogen peroxide concentration; (B) Electrochemical sensor-II is to sodium nitrite at The graph of the current response at a constant potential of 0.85 V, the inset is a plot of the current response versus the concentration of sodium nitrite.

Figure 9 Electrochemical Sensor-II detects the anti-interference of hydrogen peroxide (A) and sodium nitrite (B) respectively.

Detailed ways

The technical solution of the present invention will be described in further detail below through specific examples, but it must be pointed out that the following examples are only used to describe the content of the invention, and do not constitute limitations to the protection scope of the present invention.

The electrochemical sensor based on the double metal porphyrin coordination polymer according to the present invention is a double metal porphyrin coordination polymer CoTCPP-Cu modified electrode, that is, the double metal porphyrin coordination polymer CoTCPP is modified on the surface of the base electrode -Cu (electrochemical sensor-I); or a CoTCPP-Cu/MWNTs modified electrode, that is, first modify the base electrode with carbon nanotubes, and then modify the double metal porphyrin coordination polymer CoTCPP- on the electrode surface. Cu (electrochemical sensor-II).

The double metal porphyrin coordination polymer is meso-5,10,15,20-tetra-(p-carboxyphenyl) porphyrin double metal coordination polymer (CoTCPP-Cu), which is a double metal Co, Cu A coordination polymer formed by self-assembly with tetrakis-(p-carboxyphenyl)porphyrin (TCPP), in which metal Co coordinates with four Ns of the tetrakis-(p-carboxyphenyl)porphyrin center, and each metal Cu Coordinate with the oxygen in the carboxyl groups from four tetrakis-(p-carboxyphenyl) porphyrins respectively, and each carboxyl group is bidentately coordinated with two metal Cu; that is, it has the following structure

In the formula, CoTCPP is tetrakis-(p-carboxyphenyl)cobalt porphyrin.

Described meso-5,10,15,20-tetra-(p-carboxyphenyl)porphyrin bimetallic coordination polymer can be prepared by the following method:

CoTCPP and copper salt are respectively dissolved in DMF, and the copper salt solution prepared is added in the CoTCPP solution, and then the acid solution is added to obtain a mixed solution in which red flocs are separated out. In the mixed solution, CoTCPP: copper salt: the mole of acid The ratio is 1:4~40:100~400; the mixed solution is heated to 50~100°C for solvothermal reaction for 2~12 days, and the product is washed and dried to obtain the purple red powdery bimetallic complex polymer.

The coordination polymer prepared by the above method may contain components such as crystal water or solvent molecules.

Described electrochemical sensor adopts following method to prepare:

Ultrasonic disperse CoTCPP-Cu in deionized water to form a suspension, drop-coat the suspension on the surface of the base electrode, and dry it; then drop-coat the nafion solution on the surface of the electrode, and dry it to obtain the electrochemical sensor-I;

Or, first drop-coat the carbon nanotube suspension on the base electrode and dry it, then drop-coat the CoTCPP-Cu suspension on the electrode surface and dry it; then drop-coat the nafion solution on the electrode surface and dry it , to prepare the electrochemical sensor-II.

The electrocatalytic activity was measured by cyclic voltammetry, indicating that the electrochemical sensor has unique redox bimetallic bifunctional electrochemical catalytic activity, and can be used for electrochemical detection of hydrogen peroxide and nitrite.

The method for detecting hydrogen peroxide based on the electrochemical sensor comprises the following steps:

(1) Preparation of hydrogen peroxide standard solution

Prepare a set of standard solutions of hydrogen peroxide with different concentrations.

(2) cyclic voltammetry detection of hydrogen peroxide

In the PBS electrolyte with pH=7, the bare glassy carbon electrode or modified glassy carbon electrode is used as the working electrode, the platinum electrode is used as the auxiliary electrode, and the saturated calomel electrode is used as the reference electrode. The scanning speed was 100mV s ^-1 for cyclic voltammetry scanning. _The CV curves of the bare electrode and the electrochemical sensor with and without _hydrogen peroxide, respectively, the comparison indicates whether the sensor is responsive to H2O2. When the current increases with the increase of hydrogen peroxide concentration, it indicates that the electrochemical sensor can be applied to detect hydrogen peroxide.

(3) Chronoamperometry (i-t) detection of hydrogen peroxide

The electrochemical sensor is used to electrochemically detect hydrogen peroxide. Under the detection potential of -0.25V, the electrochemical sensor-I is continuously dripped with different concentrations and different amounts of peroxide in PBS (0.1M, pH=7) solution. After hydrogen, the response current gradually increases to obtain the i-t curve. The concentration corresponding to the current that is 3 times greater than the noise signal is the lowest detection limit. The linear range and sensitivity of the detection are obtained from the i-c standard curve.

Using the same detection principle, the i-t curve and the i-c standard curve are obtained at the detection potentials of -0.20 and -0.55V. In summary, the best working potential can be obtained as -0.25V.

(4) Detection

When detecting a sample, by reading the magnitude of the current, the concentration of hydrogen peroxide contained in the sample can be calculated according to the standard curve.

The method for detecting nitrite based on the described electrochemical sensor comprises the following steps:

(1) Prepare sodium nitrite standard solution

Prepare a set of standard solutions of sodium nitrite with different concentrations.

(2) Cyclic voltammetry detection of nitrite

In the PBS electrolyte with pH=7, the bare glassy carbon electrode or modified glassy carbon electrode is used as the working electrode, the platinum electrode is used as the auxiliary electrode, and the saturated calomel electrode is used as the reference electrode. The scanning speed was 100mV s ^-1 for cyclic voltammetry scanning. The CV curves of the bare electrode and the electrochemical sensor in the electrolyte solution with or without nitrite, respectively, the comparison indicates whether the sensor is responsive to nitrite. An increase in the response current indicates that the electrochemical sensor can be applied to detect nitrite.

(3) Chronoamperometry (it) detection of nitrite

Electrochemical sensor-I is used to electrochemically detect hydrogen peroxide. Under the detection potential of 0.85V, the electrochemical sensor continuously drops different concentrations and different amounts of nitrite in PBS (0.1M, pH=7) solution. The response current after the solution gradually increases to obtain the i-t curve. The concentration corresponding to the current that is 3 times greater than the noise signal is the lowest detection limit, and the linear range and sensitivity of the detection are obtained from the i-c standard curve.

(4) Detection

When detecting the sample, by reading the magnitude of the current, the concentration of the detected substance nitrite contained in the sample can be calculated according to the standard curve.

Example 1 Preparation of Bimetallic Coordination Polymer [Cu ₂ (Co-TCPP)(H ₂ O) ₂ ]·0.5DMF·5H ₂ O(CoTCPP-Cu)

Weigh 3mg (0.01mmol) of CoTCPP, add DMF 3mL to dissolve it; meanwhile weigh excess Cu(NO ₃ ) ₂ .3H ₂ O 100mg (0.4mmol), add DMF 2mL to dissolve it. Add the above-prepared Cu(NO ₃ ) ₂ solution into the CoTCPP solution, and add 1-4 mL of HNO ₃ (1M) while stirring, and finally obtain a mixed solution in which red flocs are precipitated. The mixed solution was placed in an oven at 65-100° C. for 5 days to obtain a purple-red powder. Filtered, washed with DMF, _H2O and EtOH respectively, and dried at room temperature.

The synthesis of CoTCPP can refer to literature: (a) Lindsey, J.S., H.C.Hsu, and I.C.Schreiman, SYNTHESISOF TETRAPHENYLPORPHYRINS UNDER VERY MILD CONDITIONS. Tetrahedron Letters, 1986.27(41): 4969-4970. (b) Kumar, A., et al ., One-pot general synthesis of metalloporphyrins. Tetrahedron Letters, 2007.48(41): 7287-7290.

The prepared bimetallic coordination polymer CoTCPP-Cu, XRD spectrum (Fig. 1) shows the characteristic peaks of planar structure (110), (320), (400), (330), (440) and (550)/(710 ), the interlayer spacing characteristic peaks (001), (002) and (004), the calculated interlayer spacing is 1.0nm. Infrared and ultraviolet spectra (Fig. 2, 3) show that Co coordinates with N in the porphyrin cavity, and Cu coordinates with carboxylic acid. In CoTCPP-Cu, the stretching vibration absorption peak of C=O in -COOH disappears at 1726cm ^-1 , indicating that -COOH has been fully coordinated, and the OH vibration absorption peaks of carboxyl groups at 1435cm ^-1 and 950cm ^-1 disappear, further illustrating -COOH Fully coordinated. 1604 and 1404cm ^-1 are the anti-symmetric Vas(COO-) and symmetric Vs(COO-) stretching vibrations of carboxylate ions, the difference between 1604 and 1404cm ^-1 is equal to 200cm ^-1 , the carboxyl group may interact with Cu(II) in a bidentate manner coordination. Figure 3 shows the ultraviolet spectrum, (a) TCPP absorbs spectrum in DMF, a strong peak S band appears at 420nm, and four low-energy Q bands appear at 515, 549, 590 and 646nm. (b) is the absorption spectrum of CoTCPP in DMF. Due to the coordination between the metal ion Co and the N in the porphyrin ring, the S band red shifts to 433nm, and the four Q bands become two, appearing at 548 and 595nm , the reduction of the Q-band absorption peak is because the porphyrin ligand belongs to the D _2h point group, and the complex belongs to the D _4h point group. (c) is the absorption spectrum of Cu-CoTCPP in DMF, the S band blue-shifted to 419nm, while the Q band was reduced to one, this is because the carboxyl O on the metalloporphyrin ring coordinates with Cu(II), improving The symmetry of the coordination polymer molecule. The change of UV-visible spectrum shows that the coordination polymer is a coordination polymer with CoTCPP as the structural unit. It can be seen from the SEM and TEM electron microscope images ( FIG. 4 ) that the CoTCPP-Cu is 100-200 nm fragments piled up into irregular particles with a width of 0.1-2 μm and a length of 0.5-3 μm.

Preparation of Embodiment 2 Electrochemical Sensor-I

(1) Polishing and cleaning of bare glassy carbon electrodes

Wash the glassy carbon electrode with secondary deionized water and ultrasonically for one minute, then polish it with alumina powder with a diameter of 0.3um for five minutes, wash the grinding cloth and the slurry on the electrode with secondary deionized water, and Put the glassy carbon electrode in the secondary deionized water for one minute, after repeated grinding and cleaning, finally dry the glassy carbon electrode for later use.

(2) Electrode modification

Ultrasonic dispersion of 5 mg of CoTCPP-Cu in 400 μL deionized water to form a suspension, 6 μL of the suspension was drop-coated on the surface of the glassy carbon electrode obtained in step (1), and dried; then drop-coated 2 μL of 1% nafion solution on the electrode surface , and dried to obtain the CoTCPP-Cu modified electrode, which is denoted as electric sensor-I.

Embodiment 3 Electrochemical sensor-1 is applied to the cyclic voltammetry scanning of hydrogen peroxide detection

(1) Preparation of hydrogen peroxide standard solution

Take 84 μL of 30% hydrogen peroxide solution, and dilute it to 4 mL. That is, a 0.2 mol L ^-1 hydrogen peroxide solution is prepared, and other concentrations are prepared in the same way.

(2) Cyclic voltammogram for hydrogen peroxide detection

The CV curves of the bare electrode and the electrochemical sensor-I with or without hydrogen peroxide in the PBS electrolyte at pH = 7, as shown in Figure 5A, a is the bare GCE, b is the bare GCE plus 0.5 mmolL ^-1 H ₂ O ₂ , a comparison with b shows that the bare GCE has no response to H ₂ O ₂ . cd is the addition of different concentrations of H ₂ O ₂ 0 and 0.5mmol L ^-1 to the electrochemical sensor-I. With the addition of hydrogen peroxide, the response of the reduction current is gradually enhanced, indicating that the electrochemical sensor-I has the ability to hydrogen peroxide reduction electrocatalytic activity.

Embodiment 4 electrochemical sensor-1 detects the optimization of hydrogen peroxide condition

Different detection potentials affect detection, determined by chronoamperometry (it).

Electrochemical sensor-I is used to electrochemically detect hydrogen peroxide, as shown in Figure 6A, under the detection potential of -0.25V, electrochemical sensor-I is added dropwise in PBS (0.1M, pH=7) solution After different concentrations (0.01mol L ^-1 , 0.02mol L ^-1 , 0.2mol L ^-1 ) and different amounts of hydrogen peroxide, the corresponding current gradually increases to obtain the it curve, and the corresponding current is 3 times larger than the noise signal Concentration is the minimum detection limit. Repeat the experiment for more than 5 times, and the minimum detection limit of the above method is 2.5×10 ^-6 M. The illustration in Figure 6A is the calibration curve of the response current and concentration of hydrogen peroxide, linear The equation is: Y=-1.01848-2.01421X, the linear range of the above detection is 7.0×10 ^-5 -4.7×10 ^-3 M (R=0.996), and the sensitivity is 23.5mA mol ^-1 L cm ^-2 .

Using the same detection principle, at the detection potential of -0.20V, the detection results obtained are: the minimum detection limit is 4.0×10 ^-5 M, the linear range is 4.4×10 ^-4 -7.3×10 ^-3 M, and the sensitivity is 3.5mA mol ^-1 L cm ^-2 ; at the same time, when the detection potential is -0.55V, the detection result is: the lowest detection limit is 7.5×10 ^-6 M, and the linear range is 7.5×10 ^-6 -3.71×10 ^-3 M with a sensitivity of 23.5 mAmol ^-1 Lcm ^-2 .

In summary, the best working potential can be obtained as -0.25V.

Embodiment 5 Electrochemical sensor-I is used for the detection of nitrite

(1) Prepare sodium nitrite standard solution

Weigh 0.1399g of sodium nitrite powder, then add 2.028mL of secondary deionized water to dissolve, that is to prepare 0.2mol L ^-1 , other concentrations are prepared in the same way.

(2) Cyclic voltammogram of electrochemical sensor-I detecting nitrite

As shown in Figure 5B, it is the CV curves of the bare electrode and the electrochemical sensor-I with or without sodium nitrite respectively, and the cyclic voltammetry of the bare glassy carbon electrode in the PBS electrolyte without nitrite (curve a ), the cyclic voltammetry of bare glassy carbon electrode in 0.5mmolL ^-1 nitrite PBS electrolyte (curve b), the cyclic voltammetry of electrochemical sensor-I without nitrite (curve c), electrochemical sensor Cyclic voltammetry (curve d) of -I in PBS electrolyte of 0.5mmolL ^-1 nitrite, the response of Co ^III /Co ^II oxidation current gradually increases, indicating that the electrochemical sensor-I has oxidation electrocatalysis for nitrite active.

Embodiment 6 electrochemical sensor-1 detects the it curve of nitrite

As shown in Figure 6B, under a constant voltage of 0.85V, continuously drop different concentrations (0.01mol L ^-1 , 0.02mol L ^-1 , 0.2mol L ^-1 ) and different amounts of nitrite to obtain electrochemical The current-time curve of the sensor-I response to nitrite, the inset is the calibration curve of the response current and concentration of sodium nitrite, the concentration corresponding to the current 3 times greater than the noise signal is the lowest detection limit, and the experiment is repeated more than 5 times It is concluded that the minimum detection limit of the above method is 5.0×10 ^-6 M, the linear range is 3.5×10 ^-5 -5.5×10 ^-3 M from the standard curve (Y=0.33214+0.72838X), and the sensitivity is 15.32 mA mol ^-1 L cm ^-2 .

Preparation of Embodiment 7 Electrochemical Sensor-II

(1) Polishing and cleaning of bare glassy carbon electrode: same as above-mentioned embodiment 1 step (1)

(2) Electrode modification

Drop-coat 6 μL of a suspension of multi-walled carbon nanotubes with a concentration of 5 mg/mL on the surface of the glassy carbon electrode obtained in step (1), and let it dry; Finally, 2 μL of 1% nafion solution was drip-coated on the surface of the electrode and dried to obtain a CoTCPP-Cu/MWNTs modified electrode, which was designated as electric sensor-II.

Embodiment 8 electrochemical sensor-II is used for the detection of hydrogen peroxide

As shown in Figures 7A and 8A, the electrochemical sensor-II has obvious reduction electrocatalytic activity for hydrogen peroxide, and different concentrations (0.01mol L ^-1 , 0.02mol L ^-1 , 0.2mol L ^-1 ) and different amounts of hydrogen peroxide to obtain the current-time curve of the electrochemical sensor-II response to hydrogen peroxide, with the concentration corresponding to the current 3 times greater than the noise signal as the minimum detection limit, repeated 5 times The above experiments show that the minimum detection limit of the above method is 5.0×10 ^-7 M; the illustration is the calibration curve of response current and concentration, the standard curve is Y=-0.56706-11.86815X, and the linear range is expanded to 5.0×10 ^{- 7} -6.2×10 ^-3 M (R=0.999), the detection sensitivity increased to 147.8mAM ^-1 cm ^-2 , and its electrocatalytic hydrogen peroxide reduction activity was significantly improved.

Embodiment 9 Electrochemical sensor-II is used for the detection of nitrite

Figure 7B is the CV curves of bare electrode and electrochemical sensor-II with or without nitrite. Accompanying drawing 8B is the current-time curve obtained by continuously dropping different concentrations (0.01mol L ^-1 , 0.02mol L ^-1 , 0.2mol L ^-1 ) and different amounts of sodium nitrite at a potential of 0.85V to be greater than the noise signal 3 The concentration corresponding to the double current is the minimum detection limit. Repeating the experiment more than 5 times, the minimum detection limit of the above method is 2.5×10 ^-6 M; the illustration is the calibration curve of the response current and concentration, and the equation of the standard curve It is Y=0.33214+0.72838X, and the linear range is expanded to 2.5×10 ^-6 -1.1×10 ^-3 M (R=0.9999), and its electrocatalytic nitrite oxidation activity is greatly improved.

The high selectivity of embodiment 10 electrochemical sensor-II

When detecting hydrogen peroxide, as shown in Figure 9A, add H ₂ O ₂ (0.5mmol), AA (0.5mmol), Glu (0.5mmol), DA (0.5mmol), UA (0.5 mmol), H ₂ O ₂ (0.5mmol) detection is not disturbed, indicating that the electrochemical sensor has high selectivity in the detection of hydrogen peroxide. At the same time, when detecting nitrite, as shown in Figure 9B, add KNO ₃ (0.5mmol), Zn(Ac) ₂ (0.5mmol), MgCl ₂ (0.5mmol), UA (0.5mmol) in sequence in the PBS electrolyte environment , Glu (0.5mmol), the detection is not disturbed, indicating that the electrochemical sensor has high selectivity in the detection of nitrite.

Claims (8)

1. the electrochemical sensor based on bimetallic porphyrin coordination polymer is detected the method for hydrogen oxide or nitrite, it is characterized in that, described method, using the electrochemical sensor based on bimetallic porphyrin coordination polymer as working electrode, adopts chronoamperometry to be detected hydrogen oxide or nitrite;

The described electrochemical sensor based on bimetallic porphyrin coordination polymer, comprises basal electrode, described basal electrode finishing bimetallic porphyrin coordination polymer or the compound of bimetallic porphyrin coordination polymer/carbon nano-tube; Described bimetallic porphyrin coordination polymer is meso-5,10,15,20-tetra--(to carboxyl phenyl) porphyrin thermometal coordination polymer, be designated as CoTCPP-Cu, be the coordination polymer that thermometal Co, Cu and four-(to carboxyl phenyl) porphyrin (TCPP) self assembly is formed, there is following structure

In formula, CoTCPP is four-(to carboxyl phenyl) Cob altporphyrin;

There is coordination in four N at wherein metal Co and four-(to carboxyl phenyl) porphyrin center, each Ni metal respectively with the oxygen coordination in the carboxyl from four four-(to carboxyl phenyl) porphyrin, each carboxyl and two Ni metal generation double coordinations.

2. the method being detected hydrogen oxide or nitrite according to claim 1, is characterized in that, in described electrochemical sensor, described basal electrode is glass-carbon electrode, and described carbon nano-tube is Single Walled Carbon Nanotube or multi-walled carbon nano-tubes.

3. the method being detected hydrogen oxide or nitrite according to claim 1, is characterized in that, described electrochemical sensor adopts following methods preparation:

A) CoTCPP-Cu ultrasonic disperse is formed suspending liquid in deionized water, this hanging drop is applied to basal electrode surface, dries; Drip at electrode surface again and be coated with nafion solution, dry, obtain described electrochemical sensor; Or

B) first on basal electrode, drip painting carbon nano tube suspension and dry, then described CoTCPP-Cu hanging drop being coated in described electrode surface and airing; Drip at electrode surface again and be coated with nafion solution, dry, obtained described electrochemical sensor.

4. the method being detected hydrogen oxide or nitrite according to claim 1, is characterized in that, described CoTCPP-Cu adopts following methods preparation:

CoTCPP and mantoquita are dissolved in DMF respectively, are joined by copper salt solution in CoTCPP solution, then add acid solution, obtain the mixed solution that red floccus is separated out, CoTCPP in mixed solution: mantoquita: the mol ratio of acid is 1: 4 ~ 40: 100 ~ 400; Described mixed solution is heated to 50 ~ 100 DEG C and carries out solvent thermal reaction 2 ~ 12 days, product washing, drying, can obtain thermometal coordination polymer described in amaranth flour powder.

5., according to the arbitrary described method being detected hydrogen oxide or nitrite of Claims 1-4, it is characterized in that, described method is detected hydrogen oxide, comprises the following steps:

(1) electrochemical sensor based on bimetallic porphyrin coordination polymer described in preparation;

(2) chronoamperometry measures the typical curve of hydrogen peroxide

Preparation Hydrogen peroxide standard solution, with the described electrochemical sensor based on bimetallic porphyrin coordination polymer for working electrode, platinum electrode is auxiliary electrode, saturated calomel electrode is contrast electrode composition three-electrode system, under constant detection current potential, adopt chronoamperometry to obtain the i-t curve of hydrogen peroxide response current, drafting or linear regression obtain i-c typical curve;

(3) detect

Under the condition identical with step (2), Electrochemical Detection is carried out to detection sample, reads response current, calculate concentration of hydrogen peroxide according to i-c typical curve.

6. the method being detected hydrogen oxide or nitrite according to claim 5, is characterized in that, described detection current potential is-0.20V ~-0.55V.

7., according to the arbitrary described method being detected hydrogen oxide or nitrite of Claims 1-4, it is characterized in that, described method detects nitrite, comprises the following steps:

(1) electrochemical sensor based on bimetallic porphyrin coordination polymer described in preparation;

(2) chronoamperometry measures the typical curve of nitrite

Preparation nitrite standard solution, with the described electrochemical sensor based on bimetallic porphyrin coordination polymer for working electrode, platinum electrode is auxiliary electrode, saturated calomel electrode is contrast electrode composition three-electrode system, under constant detection current potential, adopt chronoamperometry to obtain the i-t curve of nitrite response current, drafting or linear regression obtain i-c typical curve;

(3) detect

Under the condition identical with step (2), Electrochemical Detection is carried out to detection sample, reads response current, calculate nitrite concentration according to i-c typical curve.

8. the method being detected hydrogen oxide or nitrite according to claim 7, is characterized in that, described detection current potential is 0.70V ~ 0.95V.