A kind of all-solid-state calcium ion selective electrode based on high hydrophobic copper sulfide and application

Abstract

The application discloses a kind of full solid-state calcium ion selective electrode based on high hydrophobic copper sulfide and its preparation method and application.It includes the transduction layer coated on the surface of electrode, the preparation of the material of transduction layer includes: copper source, CTAB is dissolved into anhydrous ethanol, then sulfur powder is added, and the mixture is uniformly dispersed by ultrasonic;The material of transduction layer is obtained by carrying out solvothermal reaction to the mixed solution and post-treatment to the reaction precipitate.The application adopts one-step solvothermal method to control CuS by adding different amounts of CTAB surface hydrophobicity, prepares different nano-structure CuS-CTAB as transduction layer modification to glassy carbon electrode surface, and constructs calcium ion selective membrane on its surface to build calcium ion selective electrode with CuS-CTAB as transduction layer.CuS-CTAB has large specific capacitance and excellent hydrophobicity, and as transduction layer, it can accelerate the ion-electron conduction rate, inhibit the formation of interface water layer, and improve the stability of electrode potential.

Description

Technical Field

[0001] This invention belongs to the field of ion-selective electrodes and relates to the detection of calcium ions. Specifically, it relates to an all-solid-state calcium ion-selective electrode based on highly hydrophobic copper sulfide, its preparation method, and its application. Background Technology

[0002] Ca 2+ Calcium ions are crucial ions in nature, participating in various life activities in the human body, such as regulating gene expression and assisting in neurotransmitter transmission. Therefore, the detection of calcium ions is essential. Among numerous detection methods, electrochemical methods offer advantages such as high detection sensitivity, low detection limit, and simple operation. All-solid-state ion-selective electrodes are potentiometric electrochemical sensors composed of an ion-selective membrane, a transduction layer, and a conductive substrate. The most important component is the transduction layer, responsible for the interconversion of ion and electron signals. However, insufficient capacitance of the transduction layer material and the formation of a water layer between the transduction layer and the ion-selective membrane can lead to an unclear interface potential, causing instability in the electrode potential during measurement. Therefore, designing and developing a high-capacitance, hydrophobic transduction layer is essential for stabilizing the electrode potential.

[0003] CuS, with its high theoretical specific capacity and excellent conductivity, is widely used in batteries, supercapacitors, and other fields. It can be degraded by Cu... 2+ / Cu 3+ The redox reaction of CuS provides excellent redox capacitance through the insertion and extraction of anions in the aqueous phase. However, CuS nanomaterials synthesized by solvothermal methods typically exhibit poor hydrophobicity. Therefore, hydrophobic modification of CuS while maintaining high redox capacitance is essential for stabilizing the electrode potential as a transconducting layer material. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an all-solid-state calcium ion selective electrode based on highly hydrophobic copper sulfide, its preparation method, and its application. This invention is based on a large capacitance controlled by the hydrophobic surface of CTAB and a hydrophobic CuS-CTAB transconducting layer material.

[0005] The specific technical solution of the present invention is as follows:

[0006] A fully solid-state calcium ion selective electrode includes a transconducting layer coated on the electrode surface, wherein the preparation method of the transconducting layer material includes the following steps:

[0007] (1) Dissolve copper source and CTAB in anhydrous ethanol, then add sulfur powder and ultrasonically disperse to obtain a uniform mixture;

[0008] (2) The mixture in step (1) is subjected to a solvothermal reaction, and the reaction precipitate is post-treated to obtain the material of the transconducting layer.

[0009] In a further step, the molar ratio of copper source to sulfur powder in step (1) is 2 mmol: 4 mmol, and the mass of CTAB added is 25-75 mg for every 2 mmol of copper source added.

[0010] Preferably, the molar ratio of the copper source to the sulfur powder is 2 mmol: 4 mmol, and for every 2 mmol of copper source added, the mass of CTAB added is 50 mg.

[0011] In a further embodiment, the solvothermal reaction in step (2) is to heat at 120-180℃ for 8-18 hours; the post-treatment refers to washing and vacuum drying.

[0012] In a further embodiment, the all-solid-state calcium ion selective electrode is suitable for calcium ion concentrations of 10... -1 -10 -9 The detection limit for M is 10. -7.5 M.

[0013] In a further embodiment, the contact angle of the material of the all-solid-state calcium ion selective electrode transduction layer is 128.5°-153.9°.

[0014] The second objective of this invention is to provide a method for preparing an all-solid-state calcium ion selective electrode, comprising the following steps:

[0015] (1) The material of the transconducting layer is ultrasonically dispersed in deionized water to prepare a dispersion;

[0016] (2) The dispersion in step (1) is dripped onto the surface of the glassy carbon electrode and dried to obtain an electrode coated with a transconductance layer;

[0017] (3) The calcium ion selective membrane solution is applied in batches to the top of the electrode coated with the transconductance layer, and after drying, the all-solid calcium ion selective electrode is obtained.

[0018] In a further embodiment, the concentration of the dispersion in step (1) is 4-32 mg / mL.

[0019] In a further step, the glassy carbon electrode in step (2) needs to be pretreated. The pretreatment includes grinding the glassy carbon electrode in 0.3 μm and 0.05 μm alumina dispersions, followed by ultrasonic cleaning in nitric acid aqueous solution, ethanol and deionized water, and finally drying under argon flow.

[0020] In a further embodiment, the calcium ion selective membrane solution in step (3) is obtained by mixing calcium ion carrier II (ETH 129), sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), 2-nitrophenyl octyl ether (o-NPOE) and polyvinyl chloride (PVC), then adding tetrahydrofuran (THF), and stirring at room temperature until a transparent solution is obtained.

[0021] The third objective of this invention is to provide an application of the aforementioned all-solid-state calcium ion selective electrode for the detection of calcium ions.

[0022] In this invention, the transconducting layer is prepared using a one-step solvothermal method by adding different amounts of CTAB to modulate the surface hydrophobicity of CuS, thus preparing CuS-CTAB nanomaterials. Then, CuS-CTAB is dispersed in deionized water and ultrasonically dispersed. The dispersion is then drop-dropped onto the surface of a glassy carbon electrode as the transconducting layer. Finally, a calcium ion selective film is drop-dropped onto its surface to form an all-solid-state calcium ion selective electrode.

[0023] Since CTAB is a cationic surfactant with sixteen carbon atoms, modifying CuS with CTAB can not only significantly improve its hydrophobicity through the attachment of nonpolar alkyl chains, but also adjust the morphology and structure to bring about an additional increase in capacitance, thus simultaneously satisfying the hydrophobic and high capacitance characteristics of the transconducting layer.

[0024] Therefore, this invention uses CTAB to hydrophobically modulate CuS as the transconducting layer material for an all-solid-state calcium ion selective electrode. While maintaining a large redox capacitance, it exhibits excellent hydrophobic properties, with a maximum contact angle of 153.9°. Among them, CuS-50CTAB prepared by adding 50mg of CTAB has the largest specific surface area, excellent redox capacitance, and high hydrophobicity with a contact angle of 138.4°.

[0025] The all-solid-state calcium ion selective electrode prepared by this invention has great application prospects and commercial value. At the same time, the excellent hydrophobic properties of the transconducting layer material may also provide some inspiration for other electrocatalysis fields.

[0026] Furthermore, the all-solid-state calcium ion selective electrode constructed using CuS-50CTAB as the transconducting layer in this invention exhibits good selectivity and a low detection limit for calcium ion detection. The prepared electrode is capable of detecting calcium ions at 10... -1 -10 -7 Within the linear range of M, it exhibits a near-Nernst response of 28.23 mV / dec for calcium ions, and the detection limit for calcium ions reaches 10. -7.5 M. Meanwhile, due to the excellent hydrophobicity of its transduction layer material, this calcium ion selective electrode contains almost no interfacial water layer between the transduction layer and the ion selective membrane, exhibiting excellent stability and reproducibility. Attached Figure Description

[0027] Figure 1 (a)-(h) are scanning electron microscope images of CuS-CTAB prepared with CTAB addition amounts of 0 mg, 25 mg, 50 mg, 75 mg, 100 mg, 125 mg, 150 mg and 175 mg, respectively;

[0028] Figure 2 X-ray diffraction patterns of CuS-CTAB nanomaterials prepared with different CTAB addition amounts;

[0029] Figure 3 Contact angle test results of CuS-CTAB nanomaterials prepared with different CTAB addition amounts;

[0030] Figure 4 N2 adsorption-desorption curves of CuS-CTAB nanomaterials prepared with different CTAB addition amounts;

[0031] Figure 5 Cyclic voltammetry curves of CuS-CTAB nanomaterials prepared with different CTAB addition amounts on a glassy carbon electrode with a diameter of 3 mm.

[0032] Figure 6 Cyclic voltammetry curves of CuS-50CTAB nanomaterial loaded with different concentrations on a glassy carbon electrode with a diameter of 3 mm are shown.

[0033] Figure 7 A fully solid-state calcium ion selective electrode with CuS-50CTAB nanomaterials as the transduction layer at 10 -1 -10 -9 (a) Potential response diagram; (b) Calibration curve diagram obtained in MCaCl2 solution;

[0034] Figure 8 (a) reversibility; (b) short-term stability; (c) long-term stability were measured for an all-solid-state calcium ion selective electrode with CuS-50CTAB nanomaterials as the transduction layer. Detailed Implementation

[0035] The present invention will be further explained below with reference to the embodiments and accompanying drawings, but is not limited to the present invention.

[0036] The reagents and materials used in the following examples are as follows:

[0037] Copper nitrate trihydrate [Cu(NO3)2·3H2O], sulfur powder, hexadecyltrimethylammonium bromide (CTAB), and tetrahydrofuran (THF) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., anhydrous ethanol was purchased from China National Pharmaceutical Chemical Reagent Co., Ltd., and calcium ion carrier II (ETH 129), sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), 2-nitrophenyl octyl ether (o-NPOE), and polyvinyl chloride (PVC) were purchased from Sigma-Aldrich.

[0038] All reagents used in this experiment can be used directly without further purification.

[0039] Example 1

[0040] Dissolve 0.4832g Cu(NO3)2·3H2O and an appropriate amount of CTAB (0-175mg) in 70mL of anhydrous ethanol, then add 0.1282g sulfur powder and ultrasonically disperse for 30 minutes.

[0041] The above mixed solution was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene and heated at 180 °C for 12 hours. The precipitate was collected by centrifugation and washed three times with water and ethanol, respectively. Finally, the precipitate was collected and vacuum dried at 60 °C to obtain CuS-CTAB nanomaterials with different transconductance layers.

[0042] Example 2

[0043] Based on the CuS-CTAB nanomaterials prepared in Example 1, scanning electron microscopy, X-ray diffraction (XRD), and contact angle measurements were performed. The results are shown in [reference needed]. Figure 1-3 .

[0044] Figure 1 Scanning electron microscopy (SEM) images of CuS-CTAB prepared with CTAB additions of 0 mg, 25 mg, 50 mg, 75 mg, 100 mg, 125 mg, 150 mg, and 175 mg, respectively, are shown in (a)-(h). The SEM images reveal that CuS-CTAB consists of a flower-like structure assembled from nanosheets. A small amount of CTAB promotes the flower-like growth of CuS, while excessive CTAB inhibits CuS growth. Furthermore, the nanosheets gradually become thinner with the addition of CTAB. Figure 2 As can be seen from the X-ray diffraction pattern, the X-ray diffraction pattern of CuS-CTAB is similar to that of CuS standard spectrum. Figure 1 This can be classified as hexagonal CuS (JCPDS#06-0464), and the addition of CTAB did not cause a shift in the crystal plane. Figure 3 The contact angle test showed that the addition of CTAB caused the contact angle to increase first and then decrease sharply, reaching a maximum of 153.9°.

[0045] Based on the CuS-CTAB nanomaterial with a contact angle greater than 90° prepared in Example 1, N2 adsorption-desorption curves were tested, and the results are shown in [reference]. Figure 4 .

[0046] Figure 4 The N2 adsorption-desorption curves show that when the amount of CTAB added is 0-75 mg, the specific surface area of ​​the obtained CuS-CTAB nanomaterials first increases and then decreases, with CuS-50CTAB having the largest specific surface area.

[0047] Example 3.

[0048] The preparation of CuS-50CTAB transconducting layer material and the construction of an all-solid-state calcium ion selective electrode based on CuS-50CTAB as the transconducting layer are as follows:

[0049] (1) Preparation of CuS-50CTAB:

[0050] 0.4832 g Cu(NO3)2·3H2O and 50 mg CTAB were dissolved in 70 mL of anhydrous ethanol, and 0.1282 g sulfur powder was added. The mixture was ultrasonically dispersed for 30 minutes. The resulting solution was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene and heated at 180 °C for 12 hours. The precipitate was collected by centrifugation and washed three times with water and ethanol, respectively. Finally, the precipitate was collected and vacuum dried at 60 °C to obtain the transconducting layer material CuS-50CTAB.

[0051] (2) Preparation of GC / CuS-50CTAB:

[0052] First, the glassy carbon electrode (3 mm in diameter) was polished on a polishing cloth in 0.3 μm and 0.05 μm alumina dispersions. Then, it was ultrasonicated for five minutes in a 1:5 mixture of HNO3 and H2O, ethanol, and deionized water. The electrode was then dried under an argon flow for later use.

[0053] Weigh 4-32 mg of CuS-50CTAB and disperse it in 1 mL of deionized water. Sonicate for 30 minutes to prepare CuS-50CTAB dispersions of different concentrations (4, 8, 12, 16, 20, 24, 28, 32 mg / mL). Take 5 μL of the aforementioned CuS-50CTAB dispersion and drop it onto the surface of a glassy carbon electrode. Dry at room temperature for 6 h to obtain different GC / CuS-50CTAB electrodes.

[0054] (3) GC / CuS-50CTAB / Ca 2+ Preparation of -ISE:

[0055] Mix 4.68 mg calcium ion carrier II, 2.16 mg NaTFPB, 235.44 mg o-NPOE and 117.72 mg PVC, add 3 mL THF, and stir at room temperature for 3 h until a clear solution is obtained to obtain a membrane mixture solution.

[0056] Then, 100 μL of the membrane mixture solution was drop-coated onto the top of the GC / CuS-50CTAB electrode in batches of 10 μL each time. After the drop-coating was completed, the electrode was placed in a fume hood to dry for 12 hours. After drying, an all-solid-state calcium ion selective electrode with CuS-50CTAB as the transconducting layer was obtained.

[0057] Example 4.

[0058] Based on the different CuS-CTAB transconducting layer materials with contact angles greater than 90° prepared in Example 1, GC / CuS-CTAB electrodes were prepared according to step (2) in Example 3. Specifically, CuS-CTAB dispersions obtained by dripping different amounts of CTAB-modified CuS onto a glassy carbon electrode. A glassy carbon electrode (GCE, 3 mm diameter) was used as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl (3 mol / L KCl) as the reference electrode, forming a three-electrode system. The electrochemical performance of different CuS-CTAB electrodes was tested using cyclic voltammetry (CV) in 0.1 M KCl solution using a CHI760E electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd., China). (See [link to CHI760E electrochemical workstation]). Figure 5 ).

[0059] Depend on Figure 5 Cyclic voltammetry curves show that with the addition of CTAB, the current area of ​​the CuS-CTAB CV curve first increases and then decreases. This may be because the increased specific surface area provides more active sites, which is consistent with the previous results of the N2 adsorption-desorption curve test showing an increase followed by a decrease in specific surface area. Among them, the CV curve obtained with the CuS-50CTAB modified electrode has the largest current area.

[0060] Example 5.

[0061] Based on the GC / CuS-50CTAB loaded with different concentrations of CuS-50CTAB (4, 8, 12, 16, 20, 24, 28, 32 mg / mL) obtained in Example 3(2) above, cyclic voltammetry (CV) tests were performed in 0.1 M KCl solution (see [link to example 3]). Figure 6 ).

[0062] Depend on Figure 6 The cyclic voltammetry curves show that as the concentration of CuS-50CTAB increases, the current area of ​​the CV curve first increases and then decreases slightly. The current area of ​​the CV curve reaches its maximum when the concentration is 24 mg / mL. Therefore, 24 mg / mL is the optimal concentration of CuS-50CTAB.

[0063] Example 6.

[0064] Based on the GC / CuS-50CTAB / Ca obtained in Example 3 above, with CuS-50CTAB as the transduction layer... 2+ -ISE performs potential detection of calcium ions in solution, specifically:

[0065] GC / CuS-50CTAB / Ca 2+ -ISE is initially set to 1.0×10 -3M was activated in CaCl2 solution for 24 h, and then placed in 1.0 × 10⁻⁶ solution. -9 Activation was performed in CaCl2 solution of M for 48 h. Using a CHI760E electrochemical workstation, 10... -9 -10 -1 The potential response of the CaCl2 solution of M was tested, and the corresponding (a) potential response diagram and (b) calibration curve were plotted. See [reference needed]. Figure 7 .

[0066] from Figure 7 It can be seen that the all-solid-state calcium ion selective electrode based on CuS-50CTAB as the transduction layer achieves calcium ion selectiveness at a calcium ion concentration of 10 -1 -10 -7 M exhibits near-Nernst response (28.23 mV / dec) calcium ion detection over a wide linear range, with a detection limit reaching 10. -7.5 M,R 2 =0.999.

[0067] Example 7.

[0068] Based on the all-solid-state calcium ion selective electrode with CuS-50CTAB as the transduction layer obtained in Example 3 above, a reversibility test was conducted. The electrode was repeatedly immersed in 0.1M CaCl2 and 0.1mM CaCl2 solutions seven times in sequence, and the potential response was measured and the electrode potential change curve was recorded. Figure 8 As shown in Figure a, when the electrode is alternately used to measure the potential in two solutions, the potential fluctuation when the potential is stable in solutions of the same concentration is around 1 mV, indicating that the electrode has excellent reversibility. The stability of the electrode is evaluated through chronopotential testing and long-term stability testing, as shown in Figure a. Figure 8 As shown in Figures b and c, GC / CuS-50CTAB / Ca 2+ The short-term stability of the -ISE electrode is 2.64 μV / s, and the long-term stability is 1.23 ± 0.13 μV / h, indicating that the electrode has excellent stability.

[0069] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to the embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A fully solid-state calcium ion selective electrode based on highly hydrophobic copper sulfide, comprising a transconducting layer coated on the electrode surface and a calcium ion selective film on top of the electrode coated with the transconducting layer, characterized in that: The method for preparing the material of the transduction layer includes the following steps: (1) Dissolve copper source and CTAB in anhydrous ethanol, then add sulfur powder and ultrasonically disperse to obtain a mixture; the molar ratio of copper source and sulfur powder is 2 mmol: 4 mmol, and the mass of CTAB added is 25-75 mg for every 2 mmol of copper source added. (2) The mixture in step (1) is subjected to a solvothermal reaction, and the reaction precipitate is post-treated to obtain the material of the transconducting layer; wherein the solvothermal reaction is heating at 120-180℃ for 8-18 hours.

2. The all-solid-state calcium ion selective electrode according to claim 1, characterized in that: The molar ratio of copper source to sulfur powder is 2 mmol: 4 mmol, and for every 2 mmol of copper source added, the mass of CTAB added is 50 mg.

3. The all-solid-state calcium ion selective electrode according to claim 1, characterized in that: The post-processing mentioned in step (2) refers to washing and vacuum drying.

4. The all-solid-state calcium ion selective electrode according to claim 1, characterized in that: The contact angle of the transconducting layer material of the all-solid-state calcium ion selective electrode is 128.5°-153.9°.

5. The method for preparing the all-solid-state calcium ion selective electrode according to any one of claims 1-4, characterized in that: Includes the following steps: (1) The material of the transconducting layer is ultrasonically dispersed in deionized water to prepare a dispersion; (2) The dispersion in step (1) is dripped onto the surface of the glassy carbon electrode and dried to obtain an electrode coated with a transconductance layer; (3) The calcium ion selective membrane solution is applied in batches to the top of the electrode coated with the transconductance layer, and after drying, the all-solid calcium ion selective electrode is obtained.

6. The preparation method according to claim 5, characterized in that: The concentration of the dispersion in step (1) is 4-32 mg / mL; In step (2), the glassy carbon electrode needs to be pretreated. The pretreatment includes grinding the glassy carbon electrode in 0.3 μm and 0.05 μm alumina dispersions, followed by ultrasonic cleaning in nitric acid aqueous solution, ethanol and deionized water, and finally drying under argon flow.

7. The preparation method according to claim 5, characterized in that: In step (3), the calcium ion selective membrane solution is obtained by mixing calcium ion carrier II, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, 2-nitrophenyl octyl ether and polyvinyl chloride, then adding tetrahydrofuran and stirring at room temperature until a transparent solution is obtained.

8. The application of the all-solid-state calcium ion selective electrode as described in any one of claims 1-4, characterized in that: It is used to detect calcium ions.

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