CN112964762A - Polyacid-based complex for preparing electrochemical sensor working electrode for detecting Cr (VI) and application thereof - Google Patents
Polyacid-based complex for preparing electrochemical sensor working electrode for detecting Cr (VI) and application thereof Download PDFInfo
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Abstract
A polyacid-based complex for preparing working electrode of electrochemical sensor for detecting Cr (VI) and its application are disclosed, whose molecular formula is: h3[Cu2(4‑dpye)2(PMo12O40)]；H[Cu2(4‑Hdpye)2(PMo12O40)(H2O)4]·2H2O; wherein 4-dpye and 4-Hdpye are deprotonated N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane (4-H)2dpye). The application of the polyacid-based complex in an electrochemical sensor for detecting Cr (VI) is as follows: grinding graphite powder and the polyacid-based complex, adding paraffin oil, stirring by a copper rod, filling into a quartz tube, and preparing the working electrode. The polyacid-based complex has good oxidation-reduction characteristicsThe sensor can be used as an electrochemical sensor for detecting Cr (VI) with low cost, convenient operation, high efficiency and high speed.
Description
Technical Field
The invention belongs to the field of electrochemical sensor material synthesis, and particularly relates to a polyacid-based complex for preparing a working electrode of an electrochemical sensor for detecting Cr (VI) and application thereof.
Background
Hexavalent chromium, Cr (VI), is one of the most common toxic metal contaminants, and has a higher solubility in water, usually Cr2O7 2-Or CrO4 2-The presence of ionic forms poses a serious threat to human health and the environment. The maximum allowable concentration of Cr (VI) in underground water is 50 mug.L specified by the world health organization-1. Therefore, the development of a simple, accurate, rapid and cheap sensor for measuring Cr (VI) in water is of great significance. In recent years, atomic absorption spectroscopy, fluorescence spectroscopy, chemiluminescence, and the like have been used for detecting cr (vi), however, these techniques require expensive equipment and time-consuming operations.
Polyoxometalates are known as polynuclear metal-oxygen clusters for their high negative charge, adjustable size and structural diversity. In recent years, it has been widely used as an electrocatalyst due to its excellent redox activity, stability and diversity. The polyacid-based metal-organic complex modified carbon paste electrode has the characteristics of simple preparation, reusability and the like, and is expected to be used for an electrochemical sensor for detecting Cr (VI).
Disclosure of Invention
The technical problem to be solved by the invention is to provide a polyacid-based complex for preparing a working electrode of an electrochemical sensor for detecting Cr (VI) and application thereof, wherein the synthesis method is simple, easy to crystallize, short in reaction time and high in synthesis yield; the polyacid-based complex has good redox characteristics, and can be used as an electrochemical sensor for detecting Cr (VI) quickly with low cost and high efficiency and is convenient to operate.
The technical solution of the invention is as follows:
a polyacid-based complex for preparing a working electrode of an electrochemical sensor for detecting Cr (VI), wherein the formula of the complex is as follows:
H3[Cu2(4-dpye)2(PMo12O40)]；
H[Cu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O；
wherein 4-dpye and 4-Hdpye are deprotonated N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane (4-H)2dpye)。
Further, the complex is H3[Cu2(4-dpye)2(PMo12O40)]The method comprises the following specific synthetic steps:
copper chloride, flexible bipyrimidine bisamide organic ligand and phosphomolybdic acid H3PMo12O40Adding the flexible bipyrimidine bisamide organic ligand into an ethanol solution, wherein the flexible bipyrimidine bisamide organic ligand is N, N' -bis (4-pyrimidinecarboxamide) -1, 2-ethane, and the flexible bipyrimidine bisamide organic ligand and H3PMo12O40The molar ratio of the organic ligand to the copper chloride is 3.5: 1-5: 1, the molar ratio of the flexible dipyrimidine bisamide to the copper chloride is 0.25: 1-0.35: 1, the volume ratio of water to ethanol in ethanol solution is 3: 1-4: 1, the mixture is poured into a screw-top transparent glass bottle, the bottle cap is screwed down, the temperature is raised to 85 DEG CAnd keeping the temperature for 2 hours under the condition of solvothermal, cooling to room temperature, removing supernatant, and washing the obtained blocky crystal for 2-4 times by using deionized water to obtain the copper complex of the flexible bipyrimidine bisamide organic ligand and the Keggin type polyacid.
Further, the complex is H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2And O, the specific synthetic steps are as follows:
copper chloride, bipyrimidine bisamide organic ligand and ammonium molybdate (NH)4)6Mo7O24·4H2Adding O and phosphorous acid with the concentration of 0.1mol/L into deionized water, wherein the flexible bipyrimidine bisamide organic ligand is N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane, the molar ratio of the flexible bipyrimidine bisamide organic ligand to ammonium molybdate is 5: 3-7: 3, the molar ratio of the flexible bipyrimidine bisamide organic ligand to copper chloride is 0.125: 1-0.35: 1, and phosphorous acid and (NH)4)6Mo7O24·4H2The molar ratio of O is 1: 0.15-1: 0.075, the volume ratio of water to 0.1mol/L phosphorous acid in the reaction system is 2.5: 1-5: 1, the reaction system is poured into a screw-top transparent glass bottle, a bottle cover is screwed tightly, the temperature is raised to 85 ℃, the temperature is kept for 6 hours under the hydrothermal condition, the temperature is reduced to room temperature, a supernatant is discarded, and the obtained bulk crystal is washed for 2-4 times by deionized water to obtain the copper complex of the flexible bipyrimidine bisamide organic ligand and the Keggin type polyacid.
Further, the copper chloride is CuCl2·2H2O。
Furthermore, the heating rate is 5-15 ℃/h during heating.
Complex H3[Cu2(4-dpye)2(PMo12O40)]And the complex H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2The synthesis method of O is simple and has short synthesis period. The amide group in the flexible bipyrimidine bisamide ligand is a polar group, so that the flexible bipyrimidine bisamide ligand has good hydrophilicity, the crystallization process in the synthesis of the Keggin type polyacid-based copper complex is accelerated, and the synthesis is shortenedThe period is two hours for the whole solvothermal reaction, and six hours for the hydrothermal reaction solution, so that the energy consumption is reduced, the synthesis cost is reduced, the synthesis yield is high, and the maximum yield can reach 72%.
The application of the polyacid-based complex in an electrochemical sensor for detecting Cr (VI) is provided.
The application of the polyacid-based complex in an electrochemical sensor for detecting Cr (VI) specifically comprises the following steps:
grinding 0.10g of graphite powder and 0.01g of polyacid-based complex for 30 minutes, adding 0.10mL of paraffin oil, stirring with a copper rod, filling into a quartz tube with an inner diameter of 2.4mm, penetrating the quartz tube from the top of the quartz tube with the copper rod, and establishing electric contact with the upper part of the mixture to obtain H3[Cu2(4-dpye)2(PMo12O40)]-CPE (1-CPE) and H [ Cu [)2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O-CPE (2-CPE) working electrode.
Application of complex in electrochemical sensor for detecting Cr (VI), wherein H is3[Cu2(4-dpye)2(PMo12O40)]-CPE (1-CPE) working electrode and HCu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2The response of the O-CPE (2-CPE) working electrode to Cr (VI) is as follows:
H3[Cu2(4-dpye)2(PMo12O40)]when the concentration range of Cr (VI) of CPE is 0.5 mu M-10 mu M, the electrode pair Cr (VI) presents a linear response relation, and the sensitivity is 0.312 mu A. mu.M-1The correlation coefficient is 0.999, and the detection limit is 0.127 mu M; the corresponding time is 2 s; the linear range is 0.5 mu M-5000 mu M;
H[Cu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2when the concentration range of Cr (VI) of the O-CPE is 0.5 mu M-10 mu M, the electrode presents a linear response relation to the Cr (VI), and the sensitivity is 0.278 mu A.mu M-1The correlation coefficient is 0.998, and the detection limit is 0.171 mu M; the corresponding time is 3 s; threadThe sex range is 0.5-5000 MuM.
And (3) performance detection:
(1) in the volume ratio of 1: the concentration of 1 is 0.1mol/L H2SO4And 0.5mol/L Na2SO4In aqueous solution, the electrocatalytic performance of 1-CPE and 2-CPE on Cr (VI) in the aqueous solution is researched by cyclic voltammetry;
(2) in the volume ratio of 1:0.1 mol/L H of 12SO4And 0.5mol/L Na2SO4In the aqueous solution, the amperometric response of the 1-CPE and the 2-CPE to the Cr (VI) detection is researched by a chronoamperometric current method, a standard curve graph of the Cr (VI) concentration and the current is obtained, and the detection line of the 1-CPE and the 2-CPE to the Cr (VI) detection is obtained by calculation.
The invention synthesizes two polyacid-based copper complexes with different structures, H, by taking N, N' -bis (4-pyrimidine formamido) -1, 2-ethane as a nitrogen-containing organic ligand, copper as a transition metal and compounds of different molybdenum sources through solvothermal and hydrothermal methods3[Cu2(4-dpye)2(PMo12O40)]And H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2The oxidation capability of Keggin type polyacid anions in O plays a main role in electrochemical performance, nitrogen atoms in a hybrid material consisting of nitrogen-containing organic ligands accelerate charge transfer between adjacent carbon atoms, the conductivity is improved, and therefore the synthesized H3[Cu2(4-dpye)2(PMo12O40)]And H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O has good electrocatalytic performance; synthetic Compound H3[Cu2(4-dpye)2(PMo12O40)]Is a two-dimensional layered structure formed by connecting two adjacent metal-organic chains by Keggin type polyacid serving as a tetradentate ligand to synthesize a compound H [ Cu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O is based on [ Cu ]2(4-Hdpye)2]nBinuclear metal-organic ring and discrete Keggin type polyThree-dimensional supramolecular structures formed by acid anions. The beneficial effects are as follows:
(1) the polyacid-based metal organic complex is a crystal with high crystallinity and a definite structure, is not easy to dissolve in water and electrolyte, and can improve the catalytic performance and stability;
(2) the electrochemical method for detecting Cr (VI) has the advantages of low cost, high efficiency, high testing speed and the like, and the carbon paste electrodes (1-CPE and 2-CPE) as working electrodes have the advantages of simple preparation, easy updating of electrode surfaces and reusability, and have good practical application value;
(3) when the synthesized modified carbon paste electrode prepared from the copper complex based on the flexible bipyrimidine bisamide ligand and the Keggin type polyacid is used as an electrochemical sensor to measure trace Cr (VI), both 1-CPE and 2-CPE have wide linear range (0.5-5000 mu M) and good anti-interference performance, and the compound 1H3[Cu2(4-dpye)2(PMo12O40)]The detection limit for detecting Cr (VI) is 0.127 mu M, compound 2H [ Cu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2The detection limit of O is 0.171 mu M, and the maximum allowable concentration of Cr (VI) in the groundwater which meets the requirements of the world health organization is 50 mu g.L-1(50ppb)。
(4) The using effect of the 1-CPE and the 2-CPE is comparable to that of the reported noble metal-based Cr (VI) electrochemical sensor and exceeds that of most reported polyacid-based electrochemical sensors.
Drawings
FIG. 1 is H synthesized according to the present invention3[Cu2(4-dpye)2(PMo12O40)]The crystal structure of (1);
FIG. 2 shows the synthesis of HCu according to the present invention2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2Crystal structure diagram of O;
FIG. 3 is H synthesized according to the present invention3[Cu2(4-dpye)2(PMo12O40)]PXRD diffractogram of (a);
FIG. 4 shows the synthesis of H [ Cu ] according to the present invention2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2PXRD diffractogram of O;
FIG. 5 shows that the synthesized 1-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4At different sweep rates (from inside to outside: 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 250, 300, 350, 400, 450 and 500 mVs) in aqueous solution-1) The insets are II-II' linear relation graphs of bipolar peak current and sweeping speed;
FIG. 6 shows that the synthesized 2-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4At different sweep rates (from inside to outside: 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 250, 300, 350, 400, 450 and 500 mVs) in aqueous solution-1) The insets are II-II' linear relation graphs of bipolar peak current and sweeping speed;
FIG. 7 is 0.1M H of Cr (VI) at different concentrations for 1-CPE synthesized according to the invention2SO4And 0.5M Na2SO4Cyclic voltammogram in solution (sweep rate 40 mV. s)-1)；
FIG. 8 is 0.1M H of different concentrations of Cr (VI) for 2-CPE synthesized by the present invention2SO4And 0.5M Na2SO4Cyclic voltammogram in solution (sweep rate 40 mV. s)-1)；
FIG. 9 shows that the synthesized 1-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4Amperometric response plots of Cr (VI) detection in solution at different voltages (-0.2V, -0.18V, -0.16V and-0.14V);
FIG. 10 shows that the synthesized 2-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4Amperometric response plots of Cr (VI) detection in solution at different voltages (-0.2V, -0.18V, -0.16V and-0.14V);
FIG. 11 shows that the synthesized 1-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4Ampere current response graphs (0.5. mu.M, 10. mu.M, 100. mu.M, 1000. mu.M/time) of Cr (VI) with different concentrations are continuously added into the solution;
FIG. 12 shows that the synthesized 2-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4Ampere current response graphs (0.5. mu.M, 10. mu.M, 100. mu.M, 1000. mu.M/time) of Cr (VI) with different concentrations are continuously added into the solution;
FIG. 13 shows that the synthesized 1-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4Calibration curves between current in solution and different Cr (VI) concentrations (0.5-10 μ M);
FIG. 14 shows that the synthesized 2-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4Calibration curves between current in solution and different Cr (VI) concentrations (0.5-10 μ M);
FIG. 15 shows that the synthesized 1-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4A calibration curve between the current in the solution and different Cr (VI) concentrations (0.5-5000 mu M);
FIG. 16 shows that the synthesized 1-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4A calibration curve between the current in the solution and different Cr (VI) concentrations (0.5-5000 mu M);
FIG. 17 shows that the synthesized 1-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4The solution was added with 100. mu.M Cr (VI) and metal ions (Cr)3+，Fe3+，Fe2+，Cu2+，Co2+，Ni2+，Zn2+，Cd2+，Na+，K+) Ampere current response graph of;
FIG. 18 shows that the synthesized 1-CPE of the present invention is at 0.1M H2SO4And 0.5M Na2SO4The solution was added with 100. mu.M Cr (VI) and metal ions (Cr)3+，Fe3+，Fe2+，Cu2+，Co2+，Ni2+，Zn2+，Cd2+，Na+，K+) Ampere current response graph.
Detailed Description
Example 1 Synthesis of H3[Cu2(4-dpye)2(PMo12O40)]Wherein 4-dpye isDeprotonated N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane (4-H)2dpye), structural formula:
0.20mmol of CuCl2·2H2O, 0.07mmol of N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane, 0.02mmol of H3PMo12O40Adding 6.0mL of deionized water and 2.0mL of absolute ethyl alcohol into a 20 mL screw-top transparent glass bottle in sequence, screwing the bottle cap, heating to 85 ℃ at a heating rate of 5 ℃/H, keeping the temperature for 2H to obtain dark green blocky crystals, cleaning for 3 times by using deionized water, and naturally drying at room temperature to obtain H3[Cu2(4-dpye)2(PMo12O40)]The yield was 72%. FIG. 1(a) shows a coordination environment diagram, a one-dimensional chain structure is shown in FIG. 1(b), a Keggin type polyacid coordination mode is shown in FIG. 1(c), a two-dimensional layered structure is shown in FIG. 1(d), and a PXRD diffraction pattern is shown in FIG. 3.
Example 2 Synthesis of H3[Cu2(4-dpye)2(PMo12O40)]Wherein 4-dpye is deprotonated N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane
0.20mmol of CuCl2·2H2O, 0.07mmol of N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane, 0.02mmol of H3PMo12O40Sequentially adding 8.0mL of deionized water and 2.0mL of absolute ethyl alcohol into a 20 mL screw-top transparent glass bottle, screwing the bottle cap, heating to 85 ℃ at a heating rate of 5 ℃/H, keeping the temperature for 2H to obtain dark green blocky crystals, cleaning for 3 times by using deionized water, and naturally drying at room temperature to obtain H3[Cu2(4-dpye)2(PMo12O40)]The yield was 58%. FIG. 1(a) shows a coordination environment diagram, a one-dimensional chain structure is shown in FIG. 1(b), a Keggin type polyacid coordination mode is shown in FIG. 1(c), a two-dimensional layered structure is shown in FIG. 1(d), and a PXRD diffraction pattern is shown in FIG. 3.
Example 3 Synthesis of H3[Cu2(4-dpye)2(PMo12O40)]Wherein 4-dpye isDeprotonated is N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane
0.40mmol of CuCl2·2H2O, 0.10mmol of N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane, 0.02mmol of H3PMo12O40Adding 6.0mL of deionized water and 2.0mL of absolute ethyl alcohol into a 20 mL screw-top transparent glass bottle in sequence, screwing the bottle cap, heating to 85 ℃ at a heating rate of 5 ℃/H, keeping the temperature for 2H to obtain dark green blocky crystals, cleaning for 3 times by using deionized water, and naturally drying at room temperature to obtain H3[Cu2(4-dpye)2(PMo12O40)]The yield was 62%. FIG. 1(a) shows a coordination environment diagram, a one-dimensional chain structure is shown in FIG. 1(b), a Keggin type polyacid coordination mode is shown in FIG. 1(c), a two-dimensional layered structure is shown in FIG. 1(d), and a PXRD diffraction pattern is shown in FIG. 3.
EXAMPLE 4 Synthesis of H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O, wherein 4-Hdpye is deprotonated N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane
0.20mmol of CuCl2·2H2O, 0.07mmol of N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane, 0.03mmol (NH)4)6Mo7O24·4H2O, 10.0mL of deionized water and 3.0mL of 0.1mol/L phosphorous acid are sequentially added into a 20 mL screw-top transparent glass bottle, the bottle cap is screwed down, the temperature is raised to 85 ℃ at the heating rate of 5 ℃/H and is kept constant for 6H to obtain light green blocky crystals, the blocky crystals are washed for 3 times by the deionized water and are naturally dried at room temperature to obtain H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O, yield 66%. FIG. 2(a) shows a coordination environment diagram, FIG. 2(b-d) shows a one-dimensional chain, a two-dimensional layer and a three-dimensional supramolecular structure, and FIG. 4 shows a PXRD diffraction pattern.
EXAMPLE 5 Synthesis of H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O, wherein 4-Hdpye is deprotonated N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane
0.20mmol of CuCl2·2H2O, 0.07mmol of N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane, 0.03mmol (NH)4)6Mo7O24·4H2O, 10.0mL of deionized water and 2.0mL of 0.1mol/L phosphorous acid are sequentially added into a 20 mL screw-top transparent glass bottle, the bottle cap is screwed down, the temperature is raised to 85 ℃ at the heating rate of 5 ℃/H and is kept constant for 6H to obtain light green blocky crystals, the blocky crystals are washed for 3 times by the deionized water and are naturally dried at room temperature to obtain H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O, yield 60%. FIG. 2(a) shows a coordination environment diagram, FIG. 2(b-d) shows a one-dimensional chain, a two-dimensional layer and a three-dimensional supramolecular structure, and FIG. 4 shows a PXRD diffraction pattern.
EXAMPLE 6 Synthesis of H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O, wherein 4-Hdpye is deprotonated N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane
0.40mmol of CuCl2·2H2O, 0.05mmol of N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane, 0.03mmol of (NH)4)6Mo7O24·4H2O, 10.0mL of deionized water and 4.0mL of 0.1mol/L phosphorous acid are sequentially added into a 20 mL screw-top transparent glass bottle, the bottle cap is screwed down, the temperature is raised to 85 ℃ at the heating rate of 5 ℃/H and is kept constant for 6H to obtain light green blocky crystals, the blocky crystals are washed for 3 times by the deionized water and are naturally dried at room temperature to obtain H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O, yield 52%. FIG. 2(a) shows a coordination environment diagram, FIG. 2(b-d) shows a one-dimensional chain, a two-dimensional layer and a three-dimensional supramolecular structure, and FIG. 4 shows a PXRD diffraction pattern.
In examples 1 to 3, the temperature rise rate may be any of 5 ℃ to 15 ℃/H, and a complex H can be obtained similarly3[Cu2(4-dpye)2(PMo12O40)]。
In examples 4 to 6, the temperature rise rate may be 5 ℃ C/h to 15 ℃ CAt any temperature, the complex H [ Cu ] can be obtained2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O。
Characterization of copper complexes based on bipyrimidine bisamide organic ligands and phosphomolybdic acid
(1) Powder diffraction characterization phase purity
The complete powder diffraction data were collected on a Rigaku D/Max-2500 diffractometer operating at 100mA and 40 kV. Copper target X-rays were used. Scanning was fixed and the receiving slit was 0.1mm wide. Density data collection uses a 2 theta/theta scan pattern with a scan range of 5 deg. to 50 deg., a scan speed of 5 deg./s, and a span of 0.02 deg./time. Data were fitted using the Cerius2 program and single crystal structure powder diffraction spectrum simulated transformation using Mercury 1.4.1.
As shown in fig. 3 to 4, the powder X-ray diffraction pattern of the copper complex based on the bipyrimidine bisamide organic ligand and the Keggin-type polyacid substantially coincided with the fitted XRD pattern, indicating that the complex is pure phase. (2) Determination of Crystal Structure
Single crystals of appropriate size were selected with a microscope and analyzed at room temperature using a Bruker SMART APEX II diffractometer (graphite monochromator, Mo-Ka,
) Diffraction data was collected. Scanning mode
The diffraction data were corrected for absorption using the SADABS program. Using Olex2, the structural problem was solved by the SHELXT structural solution program using eigenphases and the structure was optimized using least squares minimization using the SHELXL optimization package. Some of the parameters for compound 1 and compound 2 crystallographic diffraction point data collection and structure refinement are shown in table 1 below:
TABLE 1
Examples 1 to 13 synthetic H3[Cu2(4-dpye)2(PMo12O40)](Compound 1) and H [ Cu ] synthesized in examples 4 to 62(4-Hdpye)2(PMo12O40)(H2O)4]·2H2Electrochemical properties of O (Compound 2) modified carbon paste electrodes were investigated
Grinding 0.10g of graphite powder and 0.01g of compound 1 in an agate mortar for 30 minutes to mix uniformly, then adding 0.10mL of paraffin oil, and stirring with a copper rod to obtain a mixture; vertically placing a quartz tube with the inner diameter of 2.4mm on a horizontal table, filling the quartz tube with the mixture, compacting, grinding the mixture on the bottom surface of the quartz tube by using weighing paper, penetrating a copper rod into the quartz tube from the top of the quartz tube, and establishing electric contact with the upper part of the mixture to prepare the 1-CPE. In the same manner, compound 2 was used to prepare 2-CPE.
Blank CPE: grinding 0.10g of graphite powder in an agate mortar for 30 minutes to form smooth and uniform graphite powder, then adding 0.10mL of paraffin oil, and stirring with a copper rod to obtain a mixture; and vertically placing a quartz tube with the inner diameter of 2.4mm on a horizontal table, filling the quartz tube with the mixture, compacting, grinding the mixture on the bottom surface of the quartz tube by using weighing paper, penetrating a copper rod into the quartz tube from the top of the quartz tube, and establishing electric contact with the upper part of the mixture to prepare the CPE. Blank CPE did not have any compound.
1-CPE and 2-CPE as working electrodes (1-CPE H prepared as in example 1)3[Cu2(4-dpye)2(PMo12O40)]For example, H prepared in example 2 and example 33[Cu2(4-dpye)2(PMo12O40)]The effect is substantially the same. 2-CPE H [ Cu ] prepared as in example 42(4-dpye)2(PMo12O40)(H2O)4]·2H2O is H [ Cu ] prepared in example 5 and example 62(4-dpye)2(PMo12O40)(H2O)4]·2H2The O effect is basically the same), a platinum wire is used as a counter electrode, an Ag/AgCl electrode is used as a reference electrode, and 0.1M H is used2SO4And 0.5M Na2SO4The aqueous solution is used as electrolyte and electrochemical test is carried out.
First, study was conducted at 0.1M H2SO4And 0.5M Na2SO41-CPE and 2-CPE in aqueous solution at different scan rates (20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 250, 300, 350, 400, 450 and 500mV s)-1) Cyclic voltammetry behavior, fig. 5-6. In the potential range of +600 to-300 mV, there are three pairs of reversible redox peaks I-I ', II-II ' and III-III '. And the peak currents of 1-CPE and 2-CPE are directly proportional to the scan rate, indicating that the redox processes of 1-CPE and 2-CPE are surface controlled (inset in fig. 5-6).
Then, the electrocatalytic properties of 1-CPE and 2-CPE to cr (vi) in aqueous solution were investigated by cyclic voltammetry. With the addition of 0.1mM Cr (VI) solution, the three pairs of oxidation peak currents of 1-CPE and 2-CPE were significantly reduced, and the reduction peak currents were both significantly increased, indicating that 1-CPE and 2-CPE have good electrocatalytic reduction characteristics for Cr (VI), FIGS. 7-8.
The amperometric response of 0.1mM Cr (VI) solution was investigated with continuous addition at different potentials (-0.2V, -0.18V, -0.16V and-0.14V) using chronoamperometric current method with continuous stirring. The results show that the optimal potentials for detecting Cr (VI) by 1-CPE and 2-CPE are-0.18V respectively, and fig. 9-10. Then, at the above optimum potential, the detection of Cr (VI) by 1-CPE and 2-CPE was investigated by chronoamperometry. Within 0-100 seconds, no substance was added to smooth the baseline. Then, 2X 10 of water was added to the solution every 30 seconds-3mol/L of K2Cr2O7Solution 10. mu.L (0.5. mu.M/time) was added 20 times in total. Adding 2X 10 of the solution every 30s-3mol/L of K2Cr2O7The solution was 200. mu.L (10. mu.M/time) and added 9 times in total. Adding 4X 10 of the solution every 30s-2mol/L of K2Cr2O7The solution was added in a total of 9 times at 100. mu.L (100. mu.M/time). Finally, 4X 10 of water was added to the solution every 30s-2mol/L of K2Cr2O7Solution 1mL (1000. mu.M/time), 4 total additions, during which time the solution responds to electricityThe flow increases with increasing cr (vi) concentration as shown in fig. 11-12. 1-CPE and 2-CPE respond differently to Cr (VI). When the concentration range of Cr (VI) of the 1-CPE is 0.5-10 mu M, the electrode presents a linear response relation to the Cr (VI), and the sensitivity is 0.312 mu A. mu.M-1(correlation coefficient 0.999), detection limit 0.127 μ M (signal-to-noise ratio: 3); when the concentration range of Cr (VI) of the 2-CPE is 0.5-10 mu M, the electrode presents a linear response relation to the Cr (VI), and the sensitivity is 0.278 mu A.mu M-1(correlation coefficient 0.998) and detection limit 0.171. mu.M (signal-to-noise ratio: 3), as shown in FIGS. 13 to 14. The response times of the 1-CPE and the 2-CPE are 2s and 3s, respectively. It is noted that when 1-CPE and 2-CPE are used as electrochemical sensors to detect Cr (VI), both have a wide linear range of 0.5-5000 μ M, as shown in FIGS. 15-16. Specifically, as shown in table 2:
TABLE 2
| Sensitivity (. mu.A. mu.M)-1) | Correlation coefficient | Detection line (mu M) | Linear range (μ M) | Response time(s) | |
| 1-CPE | 0.312 | 0.999 | 0.127 | 0.5～5000 | 2.0 |
| 2-CPE | 0.284 | 0.999 | 0.167 | 0.5～5000μM | 3.0 |
Finally, 100. mu.M of Cr (VI) solution was added to 0.1M H with continuous stirring2SO4And 0.5M Na2SO4The current response of 1-CPE and 2-CPE increased significantly when in aqueous solution. Then a series of interference ions (Cr) of 100 μ M are added in sequence at the same time interval3+，Fe3+，Fe2+，Cu2+，Co2+，Ni2+，Zn2+，Cd2+，Na+，K+) These interfering ions were found to have little effect on the cr (vi) amperometric response. Subsequently, when cr (vi) is continuously added again, the amperometric current response increases again significantly. The detection of Cr (VI) by 1-CPE and 2-CPE has higher anti-interference capability and good selectivity, as shown in FIGS. 17-18.
The carbon paste modified electrodes 1-CPE and 2-CPE prepared from the compounds 1 and 2 have good electrocatalytic reduction characteristics to Cr (VI), and can be used as electrochemical sensors to detect Cr (VI) with high sensitivity. Of these, 1-CPE has a better detection effect than 2-CPE, which may be attributed to: the two-dimensional layered structure of compound 1 has a highly exposed active surface, which can facilitate charge transfer, compared to the three-dimensional supramolecular structure of compound 2, thereby enhancing electrocatalytic activity.
The above description is only exemplary of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A polyacid-based complex for preparing a working electrode of an electrochemical sensor for detecting Cr (VI), which is characterized in that:
the molecular formula of the complex is as follows:
H3[Cu2(4-dpye)2(PMo12O40)]；
H[Cu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O；
wherein 4-dpye and 4-Hdpye are deprotonated N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane (4-H)2dpye)。
2. The polyacid-based complex for preparing a working electrode of an electrochemical sensor for detecting Cr (VI) according to claim 1, wherein: the complex is H3[Cu2(4-dpye)2(PMo12O40)]The method comprises the following specific synthetic steps:
copper chloride, flexible bipyrimidine bisamide organic ligand and phosphomolybdic acid H3PMo12O40Adding the flexible bipyrimidine bisamide organic ligand into an ethanol solution, wherein the flexible bipyrimidine bisamide organic ligand is N, N' -bis (4-pyrimidinecarboxamide) -1, 2-ethane, and the flexible bipyrimidine bisamide organic ligand and H3PMo12O40The molar ratio of the flexible bipyrimidine bisamide organic ligand to the copper chloride is 3.5: 1-5: 1, the molar ratio of the flexible bipyrimidine bisamide organic ligand to the copper chloride is 0.25: 1-0.35: 1, the volume ratio of water to ethanol in ethanol solution is 3: 1-4: 1, the mixture is poured into a screw-top transparent glass bottle, a bottle cover is screwed, the temperature is raised to 85 ℃, the temperature is kept for 2 hours under the condition of solvothermal conditions, the temperature is reduced to room temperature, a supernatant is discarded, and the obtained bulk crystal is washed for 2 to 4 times by deionized water to obtain the copper complex of the flexible bipyrimidine bisamide organic ligand and the Keggin type polyacid.
3. The polyacid-based complex for preparing a working electrode of an electrochemical sensor for detecting Cr (VI) according to claim 1,the method is characterized in that: the complex is H [ Cu ]2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2And O, the specific synthetic steps are as follows:
copper chloride, bipyrimidine bisamide organic ligand and ammonium molybdate (NH)4)6Mo7O24·4H2Adding O and phosphorous acid with the concentration of 0.1mol/L into deionized water, wherein the flexible bipyrimidine bisamide organic ligand is N, N' -bis (4-pyrimidinecarboxamido) -1, 2-ethane, the molar ratio of the flexible bipyrimidine bisamide organic ligand to ammonium molybdate is 5: 3-7: 3, the molar ratio of the flexible bipyrimidine bisamide organic ligand to copper chloride is 0.125: 1-0.35: 1, and phosphorous acid and (NH)4)6Mo7O24·4H2The molar ratio of O is 1: 0.15-1: 0.075, the volume ratio of water to 0.1mol/L phosphorous acid in the reaction system is 2.5: 1-5: 1, the reaction system is poured into a screw-top transparent glass bottle, a bottle cover is screwed tightly, the temperature is raised to 85 ℃, the temperature is kept for 6 hours under the hydrothermal condition, the temperature is reduced to room temperature, a supernatant is discarded, and the obtained bulk crystal is washed for 2-4 times by deionized water to obtain the copper complex of the flexible bipyrimidine bisamide organic ligand and the Keggin type polyacid.
4. The polyacid-based complex for preparing a working electrode of an electrochemical sensor for detecting Cr (VI) according to claim 2 or 3, characterized in that: the chloride of copper is CuCl2·2H2O。
5. The polyacid-based complex for preparing a working electrode of an electrochemical sensor for detecting Cr (VI) according to claim 2 or 3, characterized in that: the heating rate is 5-15 ℃/h when the temperature is raised.
6. Use of a polyacid-based complex according to claim 1 in an electrochemical sensor for the detection of cr (vi).
7. Use of the polyacid-based complex according to claim 6 in an electrochemical sensor for the detection of Cr (VI), characterized in that: the method specifically comprises the following steps:
grinding 0.10g of graphite powder and 0.01g of polyacid-based complex for 30 minutes, adding 0.10mL of paraffin oil, stirring with a copper rod, and filling into a quartz tube with an inner diameter of 2.4mm to obtain H3[Cu2(4-dpye)2(PMo12O40)]-CPE working electrode and HCu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2An O-CPE working electrode.
8. Use of the polyacid-based complex according to claim 7 in an electrochemical sensor for the detection of cr (vi), characterized in that: the response of the working electrode to Cr (VI) is as follows:
H3[Cu2(4-dpye)2(PMo12O40)]when the concentration range of Cr (VI) of CPE is 0.5 mu M-10 mu M, the electrode pair Cr (VI) presents a linear response relation, and the sensitivity is 0.312 mu A. mu.M-1The correlation coefficient is 0.999, and the detection limit is 0.127 mu M; the corresponding time is 2 s; the linear range is 0.5 mu M-5000 mu M;
H[Cu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2when the concentration range of Cr (VI) of the O-CPE is 0.5 mu M-10 mu M, the electrode presents a linear response relation to the Cr (VI), and the sensitivity is 0.278 mu A.mu M-1The correlation coefficient is 0.998, and the detection limit is 0.171 mu M; the corresponding time is 3 s; the linear range is 0.5 mu M to 5000 mu M.
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| US3933879A (en) * | 1969-03-18 | 1976-01-20 | Exxon Research And Engineering Company | Chelated lithium aluminum compounds |
| US5788833A (en) * | 1995-03-27 | 1998-08-04 | California Institute Of Technology | Sensors for detecting analytes in fluids |
| CN101549288A (en) * | 2009-05-14 | 2009-10-07 | 北京化工大学 | Novel Dawson polyacid intercalation hydrotalcite composite material and method of preparing the same |
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