An electrochemiluminescence sensor for detecting lead ion content in lithium hexafluorophosphate and an electrochemiluminescence analysis method

Abstract

The present invention provides an electrochemiluminescence sensor and an electrochemiluminescence analysis method for detecting the lead ion content in lithium hexafluorophosphate, which specifically belongs to the technical field of electrochemiluminescence analysis methods. The electrochemiluminescence sensor includes an electrode substrate, a PTCA / NH2-MIL-125 composite material modified on the surface of the electrode substrate, and a lead ion probe; the PTCA / NH2-MIL-125 composite material is a composite material composed of NH2-MIL-125 fixed by PTCA. In the electrochemiluminescence analysis, the electrochemical sensor is used as the working electrode, and the reference electrode and auxiliary electrode commonly used in the art are used to form a traditional three-electrode system. The detection range of this method is 1.0×10 ‑9 mol / L~1.0×10 ‑4 mol / L, the minimum detection limit is 6.3×10 ‑10 mol / L. The invention has high sensitivity, strong specificity and simple operation in detecting lead ions in lithium hexafluorophosphate.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemiluminescence analysis methods, and relates to an electrochemiluminescence sensor for detecting the content of lead ions in lithium hexafluorophosphate and an electrochemiluminescence analysis method. Background Art

[0002] As the electrolyte of ion sub-batteries, lithium hexafluorophosphate plays a pivotal role in the application of lithium-ion batteries. The control of lithium hexafluorophosphate production process and quality management of lithium hexafluorophosphate are not only related to the service life of lithium-ion batteries, but also directly affect the safety performance of lithium-ion batteries. Lead ion content is an important control indicator in lithium hexafluorophosphate. Excessive lead ion concentration in lithium hexafluorophosphate not only affects the charge and discharge performance of lithium-ion batteries, but also produces dendrites due to the reduction of lead ions at the cathode, piercing the diaphragm and causing the explosion of lithium-ion batteries. Therefore, the current lead ion content in lithium hexafluorophosphate is regulated to be below 1g / kg.

[0003] Currently, the methods reported for detecting lead ions in lithium hexafluorophosphate include spectrophotometry, plasma emission spectroscopy, and fluorescence. However, these methods are complex, time-consuming, costly, and have low detection sensitivity. Electrochemiluminescence (ECL) is a chemiluminescence caused by electrochemical reactions. It has attracted widespread attention due to its high sensitivity, strong reaction controllability, and simple instrumentation. It is a new analytical method with great development potential. Summary of the invention

[0004] The purpose of the present invention is to effectively control the lithium hexafluorophosphate production process, improve the sensitivity of lead ion detection in lithium hexafluorophosphate, and provide an electrochemiluminescence sensor and an electrochemiluminescence analysis method for detecting the lead ion content in lithium hexafluorophosphate. The electrochemiluminescence sensor of the present invention includes an electrode substrate, a PTCA / NH modified on the surface of the electrode substrate 2 -MIL-125 composite and lead ion probe; PTCA / NH 2 -MIL-125 composite material for PTCA-fixed NH 2 -MIL-125 composite material. Further, based on perylenetetracarboxylic acid (PTCA) fixed amino Ti-based MOFs (NH 2 -MIL-125), and then the lead ion probe (N) was modified with PTCA / NH 2 -MIL-125, the prepared N / PTCA / NH 2-MIL-125 is dripped onto the electrode substrate (the electrode substrate of the present invention is a commonly used electrode in an electrochemiluminescence sensor, for example, it can be a glassy carbon electrode (GCE), ITO or FTO, etc. The electrochemiluminescence sensor of the present invention is based on the selective combination of the lead ion probe (N) and the lead ions, which greatly improves the selectivity of the electrochemiluminescence sensor for lead ions. The electrochemiluminescence sensor based on the present invention can realize rapid detection of lead ions, has a simple method of use, and has high practical value.

[0005] Based on the electrochemiluminescent sensor of the present invention, an electrochemiluminescent method for detecting the content of lead ions in lithium hexafluorophosphate comprises the following steps: using electrochemiluminescence to analyze and detect lead ions in lithium hexafluorophosphate, wherein the electrochemiluminescent sensor is used as a working electrode for the electrochemiluminescent test in a three-electrode system used during the detection;

[0006] The structural formula of the lead ion probe is as follows

[0007] Furthermore, the auxiliary electrode and the reference electrode in the three-electrode system can be electrode materials commonly used in electrochemiluminescence detection, for example, a platinum electrode as the auxiliary electrode and Ag / AgCl as the reference electrode.

[0008] Furthermore, perylenetetracarboxylic acid (PTCA) immobilized amino Ti-based MOFs (NH 2 -MIL-125) composite material preparation includes: 2 -MIL-125 and PTCA were added to the ethanol solution, ultrasonically dispersed, centrifuged and washed with ethanol and deionized water respectively, and finally the washed product was placed in a drying oven and dried (the drying temperature is preferably 60°C) to obtain a light red powder, namely PTCA / NH 2 -MIL-125 composite material, the composite material is dispersed in DMF for use.

[0009] Furthermore, NH 2 -MIL-125 preparation includes: adding isopropyl titanate and 2-aminoterephthalic acid to a mixed solution of DMF and methanol, placing the obtained yellow milky liquid in a stainless steel autoclave lined with polytetrafluoroethylene, heating it in a vacuum drying oven, and after the autoclave is cooled, washing it with methanol and DMF three times respectively and centrifuging it to obtain a yellow powder, namely NH 2 -MIL-125. Furthermore, the preparation of PTCA includes: dissolving perylene tetracarboxylic dianhydride (PTCDA) in NaOH to obtain a yellow-green solution, dropping it into an HCl solution until it is completely precipitated, washing it with deionized water, and drying it to obtain a dark red powder, namely PTCA.

[0010] Further, the preparation of the electrochemiluminescent sensor includes taking the above PTCA / NH2 The DMF solution of the -MIL-125 composite material and the DMF solution of the lead ion probe are fully mixed, and then drop-coated on the cleaned glassy carbon electrode, and then placed under an infrared lamp for drying to obtain an electrochemiluminescent sensor. Specifically, the lead ion probe (N) can be prepared by the following method: 1,8-naphthalene diimide and naphthylethylenediamine are dissolved in ethanol, and the mixture is refluxed for reaction (generally for about 8 hours), and a reddish-brown solid is produced. After filtration, the product N is recrystallized from toluene.

[0011] The above-mentioned electrochemical luminescence method for detecting the content of lead ions in lithium hexafluorophosphate also includes the following steps:

[0012] (1) Containing potassium persulfate (K 2 S 2 O 8 Preparation of phosphate buffered saline (PBS) solution

[0013] Specifically, a 0.1 mol / L PBS buffer solution at pH 7.5 containing 0.05 mol / L K 2 S 2 O 8 PBS buffer solution.

[0014] (5) Preparation of standard solutions with different lead ion concentrations

[0015] Take a certain amount of 1000ppm lead ion standard solution and add 0.05mol / LK 2 S 2 O 8 A series of lead ion standard solutions with different concentrations were obtained in a 0.1 mol / L PBS buffer solution with a pH of 7.5, ranging from 1.0×10 -9 mol / L~1.0×10 -4 mol / L.

[0016] (6) Drawing of standard curve

[0017] The three-electrode system was placed in the above-mentioned solution containing a series of different concentrations of lead ions and 0.05 mol / L K 2 S 2 O 8 The samples were immersed in a 0.1 mol / L PBS buffer solution with a pH value of 7.5 for 15 min, and cyclic voltammetry was performed in the electrochemical window range of -1.6 to 0 V with a photomultiplier tube high voltage of 800 V and a scan rate of 0.1 V / s. The potential-luminescence intensity curve (E-ECL) was recorded, and a linear relationship between the difference in luminescence intensity before and after the addition of lead ions and the logarithmic value of the lead ion concentration was established to obtain the corresponding linear regression equation;

[0018] (7) Testing of samples to be tested

[0019] The sample to be tested is first pre-treated and tested under the same electrochemiluminescence test conditions as in step (6) above, and the luminescence intensity is recorded. The concentration of lead ions in the sample to be tested is calculated using the linear regression equation corresponding to the standard curve obtained in step (6).

[0020] In the electrochemiluminescent sensor of the present invention, PTCA and NH 2 -MIL-125 is tightly bound by electrostatic action, so the luminescence intensity of the electrochemiluminescence sensor is not only high but also stable. Based on the selective binding of lead ion probe N with lead ions, the electroluminescence intensity of the electrochemiluminescence sensor is linearly related to the concentration of lead ions. Compared with ordinary electrochemiluminescence sensors, the present invention has the following two significant advantages: the achievable detection range is 1.0×10-9mol / L to 1.0×10-4mol / L, and the minimum detection limit is 6.3×10-10mol / L. It has the advantages of higher sensitivity, stronger specificity, wide linear range and simple instrumentation of electrochemiluminescence analysis, and realizes the selective and rapid detection of lead ions in lithium hexafluorophosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The electrode N / PTCA / NH was modified before and after adding lead ions in the embodiment. 2 -Standard curve of the difference in luminescence intensity of MIL-125 / GCE and the logarithm of lead ion concentration. DETAILED DESCRIPTION

[0022] Example

[0023] (1) Perylenetetracarboxylic acid (PTCA) immobilized aminated Ti-based MOFs (NH 2 -MIL-125) composite material preparation

[0024] 2.4 mL of isopropyl titanate and 2.2 g of 2-aminoterephthalic acid were added to a mixed solution of 20 mL of DMF and 20 mL of methanol, and ultrasonically mixed. The obtained yellow milky liquid was poured into a 50 mL autoclave, heated at 150 ° C in a vacuum drying oven for 48 h, washed three times with methanol and DMF respectively, centrifuged, and dried at 60 ° C to obtain a yellow powder, namely NH 2 -MIL-125.

[0025] 0.1 g of perylene tetracarboxylic dianhydride (PTCDA) was dissolved in 10 mL of 0.1 M NaOH and stirred at 80 °C for 2 h to obtain a yellow-green solution. 1.0 M HCl was then added dropwise until complete precipitation. The solution was washed with deionized water and dried at 60 °C to obtain a dark red powder, namely PTCA.

[0026] 15 mg of NH 2 -MIL-125 and 5 mg of PTCA were added to 20 mL of ethanol solution, and after ultrasonication for 1 h, stirred at a stirring rate of 1080 rpm in a magnetic stirrer for 24 h. After stirring, centrifugation was performed and washed with ethanol and deionized water respectively. Finally, the washed product was placed in a vacuum drying oven and dried at 60 °C to obtain a light red powder, and 10 mg of the composite material was dispersed in 10 mL of DMF for use.

[0027] (2) Preparation of lead ion probe (N) solution

[0028] 0.54 g of 1,8-naphthalene diimide and 0.46 g of naphthylethylenediamine were dissolved in 30 mL of ethanol, and the mixture was refluxed for 8 h to produce a reddish brown solid. After filtration, it was recrystallized from toluene to obtain the product lead ion probe (N). Accurately weigh the lead ion probe (N) and dissolve it in 50 mL of de-DMF to a concentration of 5.0×10 -3 mol / L.

[0029] (3) Modified electrode N / PTCA / NH 2 -Preparation of MIL-125 / GCE

[0030] Take the above PTCA / NH 2 -MIL-125 DMF solution 1mL and lead ion probe (N) solution 100μL were mixed for 1 hour to obtain lead ion probe (N) modified PTCA / NH 2 -MIL-125 complex N / PTCA / NH 2 -MIL-125, take 2 μL of N / PTCA / NH 2 -MIL-125 is dropped onto the clean glassy carbon electrode to obtain the modified electrode N / PTCA / NH 2 -MIL-125 / GCE. N / PTCA / NH 2 -MIL-125 / GCE modified electrode is placed under an infrared lamp for drying to obtain an electrochemiluminescent sensor that can selectively detect lead ions in lithium hexafluorophosphate.

[0031] (4) Drawing of standard curve

[0032] The modified electrode was N / PTCA / NH 2 -MIL-125 / GCE was used as the working electrode, platinum electrode as the auxiliary electrode, and Ag / AgCl as the reference electrode to form a three-electrode system. The three-electrode system was placed in the above-mentioned 2 S 2 O 8The samples were immersed in PBS buffer solution for 15 min and then treated with 0.05 mol / L K 2 S 2 O 8 0.1 mol / L PBS buffer with pH = 7.5 was used as blank solution to detect the luminescence intensity.

[0033] The three-electrode system was placed in a series of lead ion concentrations (1.0×10 -9 , 1.0×10 -8 , 1.0×10 -7 , 1.0×10 -6 , 1.0×10 -5 , 1.0×10 -4 ) contains 0.05 mol / L K 2 S 2 O 8 In a 0.1 mol / L PBS buffer solution with a pH of 7.5, within the electrochemical window range of -1.6 to 0 V, the photomultiplier tube high voltage was 800 V, the scan rate was 0.1 V / s, and cyclic voltammetry scanning was performed to record the potential-luminescence intensity curve (E-ECL). The linear relationship between the difference in luminescence intensity before and after the addition of lead ions and the logarithmic value of the lead ion concentration was established, and the corresponding linear regression equation was obtained as follows: △I ECL =17705.78+1857.11LogC(mol / L), the correlation coefficient (R) is 0.998. The detection range of the linear regression equation is 1.0×10 -9 ~1.0×10 -4 mol / L, the minimum detection limit is 6.3×10 -10 mol / L.

[0034] (5) Sample testing

[0035] Accurately weigh 0.5 g of lithium hexafluorophosphate and add it to 100 mL of 0.05 mol / L K 2 S 2 O 8 The sample was placed in a 0.1 mol / L PBS buffer solution with a pH of 7.5 for electrochemiluminescence detection. The concentration of lead ions in the lithium hexafluorophosphate sample to be detected was calculated according to the linear regression equation corresponding to the above step (4). The results are listed in Table 1.

[0036] Comparative Example

[0037] (1) PTCA / NH 2 -Preparation of MIL-125 / GCE modified electrode

[0038] Use a microinjector to pipette 2 μL of 1.0 mg / mL PTCA / NH 2-DMF solution of MIL-125 material was dropped onto the clean surface of glassy carbon electrode and dried at room temperature to obtain PTCA / NH 2 -MIL-125 / GCE modified electrode was used as the working electrode for electrochemiluminescence test.

[0039] (2) Drawing of standard curve

[0040] PTCA / NH 2 -MIL-125 / GCE modified electrode was used as the working electrode, platinum electrode as the auxiliary electrode, and Ag / AgCl as the reference electrode to form a three-electrode system. 2 S 2 O 8 The luminescence intensity was detected by using a blank solution of 0.1 mol / L PBS buffer with a pH of 7.5. The three-electrode system was placed in a series of lead ion concentrations (1.0×10 -9 , 1.0×10 -8 , 1.0×10 -7 , 1.0×10 -6 , 1.0×10 -5 , 1.0×10 -4 ) contains 0.05 mol / L K 2 S 2 O 8 In a 0.1 mol / L PBS buffer solution with a pH of 7.5, in the electrochemical window range of -1.6 to 0 V, the photomultiplier tube high voltage was 800 V, and the scan rate was 0.1 V / s. Cyclic voltammetry scanning was performed, and the E-ECL curve was recorded. The linear relationship between the difference in luminescence intensity before and after the addition of lead ions and the logarithm of the lead ion concentration was established, and the corresponding linear regression equation was obtained.

[0041] (3) Sample testing

[0042] Accurately weigh 0.5 g of lithium hexafluorophosphate and add it to 100 mL of 0.05 mol / L K 2 S 2 O 8 The samples were placed in a 0.1 mol / L PBS buffer solution with a pH of 7.5 for electrochemiluminescence detection. The concentration of lead ions in the sample to be detected was calculated according to the linear regression equation corresponding to the above step (2). The results are listed in Table 1.

[0043] Table 1 Determination results of lead ions in lithium hexafluorophosphate (n=3)

[0044]

[0045] Note: 1#, 2# and 3# are different batches of lithium hexafluorophosphate, and the measurement results are the average value of 3 parallel tests.

[0046] As shown in Table 1, the lead ions in lithium hexafluorophosphate can be stably detected by the method of the present invention with high sensitivity, which is very close to the results of the ICP analysis method, verifying the accuracy of the method of the present invention. 2 -MIL-125 / GCE, due to the low sensitivity of the response to lead ions, lead ions in lithium hexafluorophosphate were not detected. From the above results, it can be seen that the present invention is feasible for detecting the content of lead ions in lithium hexafluorophosphate.

[0047] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Technicians in the relevant fields may make various corresponding changes without departing from the scope of the present invention. Therefore, all technical solutions formed by equivalent replacements or equivalent modifications belong to the protection scope of the present invention.

Claims

1. An electrochemiluminescent sensor for detecting the content of lead ions in lithium hexafluorophosphate, characterized in that: The invention comprises an electrode substrate, a PTCA / NH2-MIL-125 composite material modified on the surface of the electrode substrate, and a lead ion probe; the PTCA / NH2-MIL-125 composite material is a composite material composed of NH2-MIL-125 fixed by PTCA; The structural formula of the lead ion probe is ; When the lead ion content in lithium hexafluorophosphate is detected by electrochemiluminescence, the electrochemiluminescence sensor is used as the working electrode in the three-electrode system.

2. An electrochemiluminescence method for detecting the content of lead ions in lithium hexafluorophosphate, characterized in that: The following steps are involved: The lead ions in lithium hexafluorophosphate are analyzed and detected by electrochemiluminescence method, and the electrochemiluminescence sensor according to claim 1 is used as the working electrode of the electrochemiluminescence test in the three-electrode system used in the detection.

3. The electrochemical luminescence method for detecting the lead ion content in lithium hexafluorophosphate according to claim 2, characterized in that: The preparation method of the electrochemiluminescence sensor comprises: (1) NH2-MIL-125 and PTCA are added to an ethanol solution, ultrasonically dispersed, centrifuged and washed with ethanol and deionized water respectively, and finally the washed product is placed in a drying oven and dried to obtain a light red powder, i.e., a PTCA / NH2-MIL-125 composite material, and the composite material is dispersed in DMF for use; (2) Preparation of lead ion probe solution Dissolve the lead ion probe in DMF for later use; (3) Preparation of electrochemiluminescence sensor The DMF solution of the PTCA / NH2-MIL-125 composite material and the lead ion probe solution are fully mixed, and then drop-coated on the cleaned glassy carbon electrode, and then placed under an infrared lamp for drying to obtain the electrochemiluminescence sensor.

4. The electrochemiluminescence method for detecting the content of lead ions in lithium hexafluorophosphate according to claim 2 or 3, characterized in that: The following steps are also included: (1) Prepare PBS buffer solution containing K2S2O8; (2) Preparation of PBS buffer solutions containing different lead ion concentrations and 0.05 mol / L K2S2O8; Take a certain amount of 1000 ppm lead ion standard solution and add it to 0.1 mol / L PBS buffer solution with pH=7.5 containing 0.05 mol / L K2S2O8 to obtain a series of lead ion standard solutions with different concentrations ranging from 1.0×10 -9 mol / L~1.0×10 -4 mol / L; (3) Drawing of standard curve The three-electrode system was immersed in a series of PBS buffer solutions containing different lead ion concentrations and 0.05 mol / L K2S2O8 for a certain period of time, and the luminescence intensity was detected using a 0.1 mol / L PBS buffer solution with a pH of 7.5 containing 0.05 mol / L K2S2O8 as a blank solution; In the electrochemical window range of -1.6~0V, the photomultiplier tube high voltage was 800V, the scanning rate was 0.1V / s, and cyclic voltammetry scanning was performed to record the potential-luminescence intensity curve (E-ECL). The linear relationship between the difference in luminescence intensity before and after the addition of lead ions and the logarithm of the lead ion concentration was established, and the corresponding linear regression equation was obtained. (4) Testing of samples to be tested The sample to be tested is first pre-treated and then the pH is adjusted. The luminescence intensity is tested according to the test method in the above step (3), and then the lead ion concentration in the sample to be tested is calculated by a linear regression equation.

5. The electrochemiluminescence method for detecting the content of lead ions in lithium hexafluorophosphate according to claim 4, characterized in that: The PBS buffer solution described in step (1) contains 0.05 mol / L K2S2O8, the pH of the PBS buffer solution is 7.5, and its concentration is 0.1 mol / L; the immersion time of the electrochemiluminescence sensor in step (3) is 15 minutes.

6. The electrochemiluminescence method for detecting the content of lead ions in lithium hexafluorophosphate according to claim 4, characterized in that: The minimum detection limit is 6.3×10 -10 mol / L.

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