CN110596220B - Preparation method of quantum dot electrode for simultaneously carrying out fluorescence and electrochemical detection on metal ions - Google Patents
Preparation method of quantum dot electrode for simultaneously carrying out fluorescence and electrochemical detection on metal ions Download PDFInfo
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Abstract
The invention discloses a preparation method of a quantum dot electrode for simultaneously carrying out fluorescence and electrochemical detection on metal ions. Mixing the zinc sulfide quantum dot solution with an isometric sodium alginate solution, adding calcium carbonate powder, and uniformly mixing to obtain zinc sulfide quantum dot and sodium alginate electrodeposition liquid; and co-depositing the obtained zinc sulfide quantum dots and the sodium alginate electrodeposition liquid on an ITO glass electrode to obtain a quantum dot containing electrode capable of simultaneously carrying out fluorescence and electrochemical detection on metal ions. The electrode prepared by the invention can achieve better detection effect on the detected substances, has the characteristics of simple and convenient preparation method, simple operation, environment-friendly and pollution-free preparation process and low cost, and has good application prospect in the fields of biosensing and detectors.
Description
Technical Field
The invention belongs to the technical field of materials, and particularly relates to a preparation method of a quantum dot electrode for simultaneously carrying out fluorescence and electrochemical detection on metal ions.
Background
The electrodeposition technology has the advantages of simple operation, mild reaction conditions, time and space selectivity, controllability and the like, and is widely applied to the fields of drug controlled release, sensors, energy storage materials and the like. The controllable assembly of the stimulation responsive natural macromolecules can be realized on the surface of the electrode by utilizing the electrodeposition technology, and the codeposition of nano Materials (such as carbon nano tubes, quantum dots and the like) and the natural macromolecules can also be realized, so that a novel functional material and a biological electronic device which can be applied to different fields of environmental detection analysis, biosensors and the like are constructed [ Journal of Materials Chemistry B,2016,4(19):3331-3338 ].
Quantum dots, also known as semiconductor nanocrystals, are typically nanomaterials composed of group II-VI or III-V atoms, typically 2-10nm in size. The quantum dot is a fluorescent nano material, has excellent optical performance, high stability, long service life, adjustable emission spectrum, wide excitation spectrum, large Stokes shift, narrow and symmetrical emission spectrum and can effectively avoid spectrum overlapping phenomenon when being applied. It is worth noting that some researchers have conducted research on the application of quantum dots to the field of detection. For example, Noipa et al, using Fe3+ to modify cysteamine-terminated cadmium sulfide quantum dots, prepared a novel fluorescence sensor that showed high selectivity to pyrophosphate and was useful for fluorescence detection of pyrophosphate in aqueous media [ Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy,2014,118: 17-23 ]; freeres et al modified cadmium selenide/zinc sulfide core-shell quantum dots with redox protein cytochrome C, and fixed the modified quantum dots on the surface of an ITO glass electrode for electrochemical detection of epinephrine [ Microchemical Journal,2018,139: 18-23 ]. Therefore, the work shows that the quantum dots have good application prospect in the field of fluorescence detection or electrochemical detection. In recent years, compared with some quantum dots containing heavy metal ions (such as cadmium sulfide quantum dots and cadmium selenide quantum dots) which are widely applied at present, some quantum dots containing no heavy metal ions, particularly zinc sulfide quantum dots, have the characteristic of low toxicity, so that the application of the quantum dots in the aspects of environmental detection and analysis and biosensing is more and more concerned.
Sodium alginate is a linear polysaccharide extracted from seaweed, and has the advantages of wide source, environmental protection, no toxicity, excellent biocompatibility and the like. It is worth mentioning that sodium alginate can coordinate with divalent cations (such as calcium ion) and form a gel, so that the sodium alginate solution is transformed into gel [ Progress in Polymer Science,2012,37(1): 106-. Taira et al utilize the ion-responsiveness of sodium alginate to place electrodes within a gelatin hydrogel containing sodium alginate and calcium carbonate particles, and under the action of a voltage, calcium ions are released from the calcium carbonate particles due to acidification produced by electrolysis of water on the electrodes to form a calcium-alginate hydrogel within the gelatin, the formed calcium alginate hydrogel is trapped within the gelatin, which then acts as a supporting scaffold, and is then processed to produce a patterned calcium alginate/gelatin hydrogel [ Electrochimica Acta 2018,281:429-436 ].
In summary, quantum dots have good application prospects in the field of detection and analysis, however, the application of quantum dots to detection only involves the application of quantum dots to single fluorescence detection or electrochemical detection, and does not involve the cooperative detection of quantum dots in two ways of fluorescence detection and electrochemical detection.
Disclosure of Invention
The invention aims to provide a method for preparing a quantum dot electrode capable of simultaneously carrying out fluorescence and electrochemical detection on metal ions, the prepared electrode can achieve a better detection effect on a detected substance, and has the characteristics of simple preparation method, simplicity in operation, environment-friendly and pollution-free preparation process and low cost, and the prepared quantum dot electrode has a good application prospect in the fields of biosensing and detectors.
In order to achieve the purpose, the technical scheme is as follows:
the preparation method of the quantum dot electrode for simultaneously carrying out fluorescence and electrochemical detection on metal ions comprises the following steps:
1) adding a zinc nitrate solution into a 3-mercaptopropionic acid solution, uniformly mixing, and adjusting the pH value to 11.5-12.5 by using tetrapropyl ammonium hydroxide; sequentially adding a sodium sulfide solution and a zinc nitrate solution, uniformly mixing, and then adjusting the pH value to 11.5-12.5 by using tetrapropyl ammonium hydroxide; placing the mixture in a water bath at the temperature of 90-95 ℃ for reacting for 2-4 h, and cooling to room temperature to obtain a zinc sulfide quantum dot solution;
2) mixing the obtained zinc sulfide quantum dot solution with an isometric sodium alginate solution, adding calcium carbonate powder, and uniformly mixing to obtain zinc sulfide quantum dot and sodium alginate electrodeposition liquid;
3) and co-depositing the obtained zinc sulfide quantum dots and the sodium alginate electrodeposition liquid on an ITO glass electrode to obtain a quantum dot containing electrode capable of simultaneously carrying out fluorescence and electrochemical detection on metal ions.
According to the scheme, the preparation process of the zinc sulfide quantum dot solution in the step 1 is as follows:
dissolving 0.6-1.2 g of zinc nitrate hexahydrate in 50-100 ml of deionized water, and magnetically stirring until the zinc nitrate is fully dissolved to obtain a zinc nitrate solution for later use; dissolving 0.25-0.50 g of sodium sulfide nonahydrate in 50-100 ml of deionized water, and magnetically stirring until the sodium sulfide is fully dissolved to obtain a sodium sulfide solution for later use; dissolving 56-112 mul of 3-mercaptopropionic acid in 36-72 ml of deionized water, and magnetically stirring until the 3-mercaptopropionic acid is fully dissolved to obtain a 3-mercaptopropionic acid solution for later use;
adding 2-4 ml of the zinc nitrate solution into the 3-mercaptopropionic acid solution, magnetically stirring for 10-15 minutes, uniformly mixing, and adjusting the pH value of the mixed solution to be 11.5-12.5 by using tetrapropyl ammonium hydroxide; rapidly adding 4-8 ml of the sodium sulfide solution into the mixed solution within 2-4 seconds, and magnetically stirring for 5-10 minutes; then dropwise adding 6-12 ml of zinc nitrate solution at a dropwise adding speed of 1-2 drops per second under magnetic stirring, and adjusting the pH value of the mixed solution to 11.5-12.5 by using tetrapropyl ammonium hydroxide after dropwise adding; and (3) placing the obtained mixed solution in a water bath at the temperature of 90-95 ℃ for reacting for 2-4 hours, and cooling the mixed solution to room temperature after the reaction is finished to obtain the zinc sulfide quantum dot solution.
According to the scheme, the preparation process of the sodium alginate solution used in the step 2 is as follows:
and adding 4-6 g of sodium alginate solid powder into a beaker filled with 200-300 ml of deionized water, and carrying out magnetic stirring for 4-6 hours to fully dissolve the sodium alginate powder so as to obtain a sodium alginate solution with the mass percentage of 2-3%.
According to the scheme, 0.08-0.10 g of calcium carbonate powder is added into 8-10 ml of a mixed solution of a zinc sulfide quantum dot and sodium alginate in the step 2.
According to the scheme, the co-deposition process of the zinc sulfide quantum dots and the sodium alginate electrodeposition liquid on the ITO glass electrode in the step 3 is as follows:
an ITO glass electrode is used as an anode, a platinum sheet electrode is used as a cathode, the two electrodes are placed in parallel in the zinc sulfide quantum dot and sodium alginate electrodeposition liquid, the two electrodes are inserted into the electrodeposition liquid 1-2 cm below the liquid level, the interval between the two electrodes is 0.8-1.2 cm, and a direct-current power supply is adopted to apply a voltage of 3.5-4.5V for electrodeposition for 10-20 minutes; and after the electrodeposition is finished, immediately taking the anode ITO glass electrode out of the electrodeposition solution, washing the surface of the electrode for 3-5 times by using deionized water, and preparing the ITO glass electrode with the surface containing quantum dots.
According to the scheme, the ITO glass electrode comprises the following pretreatment processes:
the method comprises the steps of cutting ITO glass into a rectangle with the length of 3-5 cm and the width of 0.8-1.5 cm, washing the rectangle with hydrochloric acid, acetone and deionized water with the molar concentration of 0.1-0.15M for 3-5 times, and then placing the rectangle in the deionized water for ultrasonic cleaning for 5-10 minutes.
According to the scheme, the platinum sheet electrode comprises the following pretreatment processes:
washing the surface of the platinum sheet electrode with hydrochloric acid, acetone and distilled water with the molar concentration of 0.1-0.15M for 3-5 times, and then placing the platinum sheet electrode in deionized water for ultrasonic cleaning treatment for 5-10 minutes.
The quantum dot containing electrode prepared by the method is used as a working electrode, a platinum wire electrode is used as a counter electrode, and a calomel electrode is used as a reference electrode; dripping the metal ion solution to be detected into the system, and carrying out electrochemical detection on the metal ions by using an electrochemical workstation; meanwhile, the content quantum dot electrode after electrochemical detection can be taken out, and the fluorescence intensity of the content quantum dot electrode can be detected by a fluorescence spectrophotometer.
The technical principle of the invention is as follows: sodium alginate is a linear polysaccharide extracted from seaweed and capable of forming a gel by complexation with some divalent cations (e.g. calcium ions) and thereby converting the sodium alginate solution to a gel. By utilizing the ion-responsive sol-gel conversion performance of sodium alginate, the codeposition of zinc sulfide quantum dots and sodium alginate can be carried out on an ITO glass electrode by adopting an electrodeposition technology, namely, a mixed solution of zinc sulfide quantum dots containing calcium carbonate powder and sodium alginate is used as an electrodeposition solution, the ITO glass electrode is used as an anode, a platinum sheet is used as a cathode, and the codeposition of the zinc sulfide quantum dots and the sodium alginate is directly carried out on the ITO glass electrode. In the electrodeposition process, the electrochemical reaction generated by the anode can enable the surface of the anode electrode to generate hydrogen ions, the hydrogen ions can react with calcium carbonate near the surface of the anode to generate calcium ions, and at the moment, sodium alginate near the surface of the anode and the calcium ions can generate coordination action to generate sol-gel transformation, so that sodium alginate gel containing quantum dots is formed on the surface of the anode ITO glass electrode, and a quantum dot electrode capable of simultaneously performing fluorescence and electrochemical detection on metal ions is constructed.
The quantum dot utilized by the invention is a novel fluorescent nano material, and has the characteristics of high stability, long service life, excellent optical performance and the like. The zinc sulfide quantum dots do not contain heavy metal elements, so compared with some quantum dots (such as cadmium sulfide quantum dots) which are widely applied at present and contain heavy metal ions, the zinc sulfide quantum dots have the characteristic of low toxicity. At present, quantum dots have good application prospects in the field of fluorescence detection or electrochemical detection, and therefore, the application of quantum dots in the aspects of environmental detection and analysis and biosensing is receiving more and more attention. The sodium alginate electrodeposition technology is utilized to construct a quantum dot containing electrode capable of carrying out fluorescence detection and electrochemical detection on metal ions, and the constructed quantum dot containing ITO glass electrode can carry out cooperative detection on detected substances (such as copper ions) by adopting two modes of fluorescence detection and electrochemical detection.
The ITO glass electrode, namely the indium tin oxide glass electrode, is prepared by depositing a layer of indium tin oxide film on the basis of soda-lime-based or silicon-boron-based substrate glass, has good photoelectric property, belongs to one of transparent conductive oxides, and has the property of an n-type semiconductor. The ITO glass electrode has high conductivity, good mechanical hardness, good chemical stability and high visible light transmittance, so that the ITO glass can be directly used as an electrode for electrodeposition, a working electrode for electrochemical detection and for fluorescence detection, co-deposition of zinc sulfide quantum dots and sodium alginate can be directly carried out on the ITO glass electrode, and the constructed quantum dot electrode can be used for carrying out cooperative detection on detected substances by adopting two modes of fluorescence detection and electrochemical detection.
The invention has the beneficial effects that:
1) the quantum dot electrode which is constructed by the invention and can simultaneously carry out fluorescence detection and electrochemical detection on metal ions not only can carry out electrochemical detection on some metal ions (such as copper ions) by a cyclic voltammetry method, a differential pulse voltammetry method, an alternating current impedance method and the like, but also can carry out fluorescence detection on some metal ions (such as copper ions) by utilizing the change of the fluorescence intensity of zinc sulfide quantum dots. Therefore, the constructed quantum dot electrode can be used for cooperatively detecting the detected substance by adopting two modes of fluorescence detection and electrochemical detection, so that a better detection effect is achieved, and the quantum dot electrode has a good application prospect in the fields of sensors, detectors and the like.
2) The anodic electrodeposition technology of the natural high-molecular sodium alginate can regulate and control electrodeposition conditions (such as electrodeposition time, voltage, current density and the like) in the electrodeposition process, and can control the thickness and the shape of the prepared electrodeposited film; the preparation method is simple, mild in condition, green and environment-friendly; compared with a cathode electrodeposition technology, the sodium alginate anode electrodeposition technology is utilized to obtain a deposition film on the surface of the electrode, the surface of the deposition film is flat and smooth and has no bubbles, and the application of the constructed quantum dot-containing electrode in the aspect of detection is facilitated.
3) The quantum dot electrode preparation method can perform fluorescence and electrochemical detection on metal ions simultaneously, and the quantum dots utilized by the method are zinc sulfide quantum dots which do not contain heavy metal ions and have the advantages of low toxicity, no pollution and environmental protection; the electro-deposition natural polymer is sodium alginate, and has the advantages of wide source, low cost, good biocompatibility, no toxicity, environmental protection and the like. Therefore, the zinc sulfide quantum dots and the sodium alginate have good application prospects in the fields of biosensing, biological detection and biomedicine due to the characteristics of the zinc sulfide quantum dots and the sodium alginate.
Drawings
FIG. 1: example 1 a photograph of a fluorescent film of quantum dot-containing ITO electrode under a 302nm ultraviolet lamp (left) and a photograph of quantum dot-free ITO glass electrode under a 302nm ultraviolet lamp (right) constructed by electrodeposition technique;
FIG. 2: the quantum dot electrode constructed in the embodiment 1 adopts a three-electrode system (an ITO glass electrode containing quantum dots is used as a working electrode, a platinum wire electrode is used as a counter electrode, and a calomel electrode is used as a reference electrode) to carry out electrochemical differential pulse voltammetry detection on copper ions;
FIG. 3: the quantum dot electrode constructed in example 1 was used for fluorescence spectrum detection of copper ions.
Detailed Description
The following examples further illustrate the technical solutions of the present invention, but should not be construed as limiting the scope of the present invention.
Example 1
A method for preparing a quantum dot electrode capable of simultaneously carrying out fluorescence and electrochemical detection on metal ions comprises the following steps:
1) preparing zinc sulfide quantum dots and sodium alginate electrodeposition liquid: taking 4g of sodium alginate solid powder, adding the sodium alginate solid powder into a beaker filled with 200ml of deionized water, and carrying out magnetic stirring for 4 hours to fully dissolve the sodium alginate powder to obtain a sodium alginate solution with the mass percentage of 2% for later use;
dissolving 0.6g of zinc nitrate hexahydrate in 50ml of deionized water, and magnetically stirring until the zinc nitrate is fully dissolved to obtain a zinc nitrate solution for later use; dissolving 0.25g of sodium sulfide nonahydrate in 50ml of deionized water, and magnetically stirring until the sodium sulfide is fully dissolved to obtain a sodium sulfide solution for later use; dissolving 56 mu l of 3-mercaptopropionic acid in 36ml of deionized water, and magnetically stirring until the 3-mercaptopropionic acid is fully dissolved to obtain a 3-mercaptopropionic acid solution for later use;
adding 2ml of the zinc nitrate solution into a 3-mercaptopropionic acid solution, magnetically stirring for 10 minutes, uniformly mixing, and adjusting the pH value of the mixed solution to 12 by using tetrapropyl ammonium hydroxide; then 4ml of sodium sulfide solution is rapidly added into the mixed solution within 2 seconds, and magnetic stirring is carried out for 5 minutes; then 6ml of zinc nitrate solution was added dropwise to the mixed solution under magnetic stirring at a dropping rate of 1 drop per second, and after the addition was completed, the pH of the mixed solution was adjusted to 12 with tetrapropylammonium hydroxide. Then, placing the mixed solution in a water bath at 90 ℃ for reaction for 2 hours, and cooling the mixed solution to room temperature after the reaction is finished to obtain a zinc sulfide quantum dot solution for later use;
taking 4ml of zinc sulfide quantum dot solution and the sodium alginate solution with the same volume, and uniformly mixing the two solutions under magnetic stirring; then adding 0.08g of calcium carbonate powder into 8ml of mixed solution of zinc sulfide quantum dots and sodium alginate, and uniformly mixing under magnetic stirring to obtain zinc sulfide quantum dots and sodium alginate electrodeposition solution for later use;
2) preparation of ITO glass electrode: cutting ITO glass into a rectangle with the length of 3 cm and the width of 0.8 cm, washing the rectangle for 3 times by using hydrochloric acid, acetone and deionized water with the molar concentration of 0.1M respectively, and then placing the rectangle in the deionized water for ultrasonic cleaning for 5 minutes for later use; in addition, the surface of the platinum sheet electrode is respectively washed for 3 times by hydrochloric acid, acetone and distilled water with the molar concentration of 0.1M, and then is placed in deionized water for ultrasonic cleaning treatment for 5 minutes for later use;
3) co-depositing zinc sulfide quantum dots and sodium alginate on an ITO glass electrode: using an ITO glass electrode as an anode and a platinum sheet as a cathode, placing two electrodes in parallel in the zinc sulfide quantum dot and sodium alginate electrodeposition liquid obtained in the step 1), inserting the electrodes into the electrodeposition liquid with the distance of 1 cm below the liquid level and the distance of 1.2 cm between the two electrodes, and applying a voltage of 3.5V by using a direct current power supply to perform electrodeposition for 10 minutes; after the electrodeposition is finished, immediately taking the anode ITO glass electrode out of the electrodeposition liquid, washing the surface of the electrode for 3 times by using deionized water, and preparing the ITO glass electrode with quantum dots on the surface, namely the quantum dot-containing electrode capable of simultaneously carrying out fluorescence and electrochemical detection on metal ions;
4) carrying out fluorescence and electrochemical cooperative detection on metal ions by using the electrode containing the quantum dots: adopting a three-electrode system, taking the quantum dot electrode prepared in the step 3) as a working electrode, taking a platinum wire electrode as a counter electrode, and taking a calomel electrode as a reference electrode; dripping the metal ion solution to be detected into the system, and carrying out electrochemical detection on the metal ions by using an electrochemical workstation; meanwhile, the content quantum dot electrode after electrochemical detection can be taken out, and the fluorescence intensity of the content quantum dot electrode can be detected by a fluorescence spectrophotometer.
FIG. 1 is a photograph of the fluorescent light of a quantum dot-containing ITO electrode constructed by electrodeposition technique in example 1 of the present invention under a 302nm ultraviolet lamp (left), and a photograph of a control quantum dot-free ITO glass electrode under a 302nm ultraviolet lamp (right). The graph shows that a layer of obvious film is arranged on the constructed ITO electrode containing the quantum dots, namely a zinc sulfide quantum dot/sodium alginate film obtained by electrodeposition on the surface of the ITO electrode by utilizing an electrodeposition technology, and the film shows very obvious blue fluorescence under the irradiation of a 302nm ultraviolet lamp, which indicates that the zinc sulfide quantum dots exist in the film; however, the comparative ITO glass electrode without quantum dots (sodium alginate film without zinc sulfide quantum dots obtained by electrodeposition on the surface of ITO electrode using electrodeposition technology) has a distinct film, but the film does not show fluorescence under the irradiation of a 302nm ultraviolet lamp; the results show that the ITO electrode containing the quantum dots can be constructed and obtained by utilizing the sodium alginate anode electrodeposition technology, and the electrodeposited zinc sulfide quantum dots still have fluorescence properties.
Fig. 2 shows that the quantum dot-containing electrode constructed in example 1 of the present invention adopts a three-electrode system (ITO glass electrode containing quantum dots is a working electrode, platinum wire electrode is a counter electrode, and calomel electrode is a reference electrode) to perform electrochemical differential pulse voltammetry detection of copper ions. Taking a sodium chloride solution with the mass fraction of 0.9% as a buffer solution, adding 100 mul of 0.01M copper sulfate solution into the system by using a liquid-transfering gun, setting the initial voltage position to be-0.5V and the termination voltage to be 0.3V, and testing a differential pulse voltammetry curve; then, the above steps are repeated by using copper sulfate solutions with different concentrations (0.02M, 0.03M, 0.04M and 0.05M respectively) to obtain a series of differential pulse voltammetry curves. From the differential pulse voltammogram in the figure, it can be found that the peak current is higher as the concentration of copper sulfate (copper ions) added in the system is higher, and these results show that the electrochemical detection of copper ions can be performed by using the quantum dot ITO electrode constructed in example 1 of the present invention.
FIG. 3 shows the fluorescence spectrum detection of copper ions by the quantum dot electrode constructed in example 1 of the present invention. Immediately taking out the quantum dot-containing ITO electrode from a detection system after the electrochemical test of the quantum dot-containing ITO electrode is finished, and performing a fluorescence spectrum test by adopting a Shimadzu spectrophotometer RF-5501PC in Japan and setting an excitation wavelength to be 280 nm; then, the above steps were repeated for the above different copper sulfate solution concentrations (0.02M, 0.03M, 0.04M, 0.05M), and fluorescence spectrum was measured by setting the excitation wavelength to 280nm using a Shimadzu spectrophotometer RF-5501PC, Japan. From the fluorescence spectrum in the figure, it can be seen that the fluorescence intensity of the quantum dots on the electrode gradually decreases with the gradual increase of the concentration of the added copper sulfate, and these results show that the fluorescence detection of the copper ions can be performed by using the quantum dot ITO electrode constructed in embodiment 1 of the present invention. In summary, the quantum dot ITO electrode constructed in embodiment 1 of the present invention can perform fluorescence detection and electrochemical detection on copper ions simultaneously, that is, perform cooperative detection on copper ions by using two ways of fluorescence detection and electrochemical detection simultaneously.
Example 2
A preparation method of a quantum dot electrode capable of simultaneously carrying out fluorescence detection and electrochemical detection on metal ions comprises the following steps:
1) preparing zinc sulfide quantum dots and sodium alginate electrodeposition liquid: taking 6g of sodium alginate solid powder, adding the sodium alginate solid powder into a beaker filled with 300ml of deionized water, and carrying out magnetic stirring for 6 hours to fully dissolve the sodium alginate powder to obtain a sodium alginate solution with the mass percentage of 3% for later use;
dissolving 1.2g of zinc nitrate hexahydrate in 100ml of deionized water, and magnetically stirring until the zinc nitrate is fully dissolved to obtain a zinc nitrate solution for later use; dissolving 0.50g of sodium sulfide nonahydrate in 100ml of deionized water, and magnetically stirring until the sodium sulfide is fully dissolved to obtain a sodium sulfide solution for later use; dissolving 112 mul of 3-mercaptopropionic acid in 72ml of deionized water, and magnetically stirring until the 3-mercaptopropionic acid is fully dissolved to obtain a 3-mercaptopropionic acid solution for later use;
adding 4ml of the zinc nitrate solution into a 3-mercaptopropionic acid solution, magnetically stirring for 15 minutes, uniformly mixing, and adjusting the pH value of the mixed solution to 11.5 by using tetrapropyl ammonium hydroxide; then 8ml of sodium sulfide solution is rapidly added into the mixed solution within 4 seconds, and magnetic stirring is carried out for 10 minutes; then, 12ml of zinc nitrate solution was added dropwise to the mixed solution under magnetic stirring at a dropping rate of 2 drops per second, and after the addition was completed, the pH of the mixed solution was adjusted to 11.5 with tetrapropylammonium hydroxide. Then, placing the mixed solution in a water bath at 95 ℃ for reaction for 4 hours, and cooling the mixed solution to room temperature after the reaction is finished to obtain a zinc sulfide quantum dot solution for later use;
taking 5ml of zinc sulfide quantum dot solution and the sodium alginate solution with the same volume, and uniformly mixing the two solutions under magnetic stirring; then adding 0.10g of calcium carbonate powder into 10ml of mixed solution of zinc sulfide quantum dots and sodium alginate, and uniformly mixing under magnetic stirring to obtain zinc sulfide quantum dots and sodium alginate electrodeposition solution for later use;
2) preparation of ITO glass electrode: cutting ITO glass into a rectangle with the length of 5 cm and the width of 1.5 cm, washing the rectangle with hydrochloric acid, acetone and deionized water with the molar concentration of 0.15M for 5 times, and then placing the rectangle in the deionized water for ultrasonic cleaning treatment for 10 minutes for later use; in addition, the surface of the platinum sheet electrode is respectively washed for 5 times by hydrochloric acid, acetone and distilled water with the molar concentration of 0.15M, and then is placed in deionized water for ultrasonic cleaning treatment for 10 minutes for later use;
3) co-depositing zinc sulfide quantum dots and sodium alginate on an ITO glass electrode: using an ITO glass electrode as an anode and a platinum sheet as a cathode, placing two electrodes in parallel in the zinc sulfide quantum dot and sodium alginate electrodeposition liquid obtained in the step 1), inserting the two electrodes into the electrodeposition liquid 2 cm below the liquid level, and applying a voltage of 4.5V by using a direct current power supply to perform electrodeposition for 20 minutes, wherein the interval between the two electrodes is 1.2 cm; after the electrodeposition is finished, immediately taking the anode ITO glass electrode out of the electrodeposition solution, washing the surface of the electrode for 5 times by using deionized water, and preparing the ITO glass electrode containing quantum dots on the surface, namely a quantum dot containing electrode capable of simultaneously carrying out fluorescence and electrochemical detection on metal ions;
4) carrying out fluorescence and electrochemical cooperative detection on metal ions by using the electrode containing the quantum dots: adopting a three-electrode system, taking the quantum dot electrode prepared in the step 3) as a working electrode, taking a platinum wire electrode as a counter electrode, and taking a calomel electrode as a reference electrode; dripping the metal ion solution to be detected into the system, and carrying out electrochemical detection on the metal ions by using an electrochemical workstation; meanwhile, the content quantum dot electrode after electrochemical detection can be taken out, and the fluorescence intensity of the content quantum dot electrode can be detected by a fluorescence spectrophotometer.
Example 3
A preparation method of a quantum dot electrode capable of simultaneously carrying out fluorescence detection and electrochemical detection on metal ions comprises the following steps:
1) preparing a zinc sulfide quantum dot and a sodium alginate electrodeposition solution: taking 5g of sodium alginate solid powder, adding the sodium alginate solid powder into a beaker filled with 250ml of deionized water, and carrying out magnetic stirring for 4 hours to fully dissolve the sodium alginate powder to obtain a sodium alginate solution with the mass percentage of 2.5% for later use;
dissolving 0.6g of zinc nitrate hexahydrate in 50ml of deionized water, and magnetically stirring until the zinc nitrate is fully dissolved to obtain a zinc nitrate solution for later use; dissolving 0.25g of sodium sulfide nonahydrate in 50ml of deionized water, and magnetically stirring until the sodium sulfide is fully dissolved to obtain a sodium sulfide solution for later use; dissolving 56 mu l of 3-mercaptopropionic acid in 36ml of deionized water, and magnetically stirring until the 3-mercaptopropionic acid is fully dissolved to obtain a 3-mercaptopropionic acid solution for later use;
adding 2ml of the zinc nitrate solution into a 3-mercaptopropionic acid solution, magnetically stirring for 10 minutes, uniformly mixing, and adjusting the pH value of the mixed solution to 12 by using tetrapropyl ammonium hydroxide; then 4ml of sodium sulfide solution is rapidly added into the mixed solution within 2 seconds, and magnetic stirring is carried out for 5 minutes; then 6ml of zinc nitrate solution was added dropwise to the mixed solution under magnetic stirring at a dropping rate of 1 drop per second, and after the addition was completed, the pH of the mixed solution was adjusted to 12 with tetrapropylammonium hydroxide. Then, placing the mixed solution in a water bath at 90 ℃ for reaction for 2 hours, and cooling the mixed solution to room temperature after the reaction is finished to obtain a zinc sulfide quantum dot solution for later use;
taking 5ml of zinc sulfide quantum dot solution and the sodium alginate solution with the same volume, and uniformly mixing the two solutions under magnetic stirring; then adding 0.10g of calcium carbonate powder into 10ml of mixed solution of zinc sulfide quantum dots and sodium alginate, and uniformly mixing under magnetic stirring to obtain zinc sulfide quantum dots and sodium alginate electrodeposition solution for later use;
2) preparation of ITO glass electrode: cutting ITO glass into a rectangle with the length of 5 cm and the width of 1.5 cm, washing the rectangle for 3 times by using hydrochloric acid, acetone and deionized water with the molar concentration of 0.1M respectively, and then placing the rectangle in the deionized water for ultrasonic cleaning for 5 minutes for later use; in addition, the surface of the platinum sheet electrode is respectively washed for 3 times by hydrochloric acid, acetone and distilled water with the molar concentration of 0.1M, and then is placed in deionized water for ultrasonic cleaning treatment for 5 minutes for later use;
3) co-depositing zinc sulfide quantum dots and sodium alginate on an ITO glass electrode: using an ITO glass electrode as an anode and a platinum sheet as a cathode, placing two electrodes in parallel in the zinc sulfide quantum dot and sodium alginate electrodeposition liquid obtained in the step 1), inserting the two electrodes into the electrodeposition liquid 2 cm below the liquid level, and applying a voltage of 3.5V by using a direct current power supply to perform electrodeposition for 10 minutes, wherein the interval between the two electrodes is 0.8 cm; after the electrodeposition is finished, immediately taking the anode ITO glass electrode out of the electrodeposition solution, washing the surface of the electrode for 5 times by using deionized water, and preparing the ITO glass electrode containing quantum dots on the surface, namely a quantum dot containing electrode capable of simultaneously carrying out fluorescence and electrochemical detection on metal ions;
4) carrying out fluorescence and electrochemical cooperative detection on metal ions by using the electrode containing the quantum dots: adopting a three-electrode system, taking the quantum dot electrode prepared in the step 3) as a working electrode, taking a platinum wire electrode as a counter electrode, and taking a calomel electrode as a reference electrode; dripping the metal ion solution to be detected into the system, and carrying out electrochemical detection on the metal ions by using an electrochemical workstation; meanwhile, the content quantum dot electrode after electrochemical detection can be taken out, and the fluorescence intensity of the content quantum dot electrode can be detected by a fluorescence spectrophotometer.
Claims (5)
1. The preparation method of the quantum dot electrode for simultaneously carrying out fluorescence and electrochemical detection on metal ions is characterized by comprising the following steps of:
1) dissolving 0.6-1.2 g of zinc nitrate hexahydrate in 50-100 ml of deionized water, and magnetically stirring until the zinc nitrate is fully dissolved to obtain a zinc nitrate solution for later use; dissolving 0.25-0.50 g of sodium sulfide nonahydrate in 50-100 ml of deionized water, and magnetically stirring until the sodium sulfide is fully dissolved to obtain a sodium sulfide solution for later use; dissolving 56-112 mul of 3-mercaptopropionic acid in 36-72 ml of deionized water, and magnetically stirring until the 3-mercaptopropionic acid is fully dissolved to obtain a 3-mercaptopropionic acid solution for later use;
adding 2-4 ml of the zinc nitrate solution into the 3-mercaptopropionic acid solution, magnetically stirring for 10-15 minutes, uniformly mixing, and adjusting the pH value of the mixed solution to 11.5-12.5 by using tetrapropylammonium hydroxide; rapidly adding 4-8 ml of the sodium sulfide solution into the mixed solution within 2-4 seconds, and magnetically stirring for 5-10 minutes; then dropwise adding 6-12 ml of zinc nitrate solution at a dropwise adding speed of 1-2 drops per second under magnetic stirring, and adjusting the pH value of the mixed solution to 11.5-12.5 by using tetrapropyl ammonium hydroxide after dropwise adding; placing the obtained mixed solution in a water bath at the temperature of 90-95 ℃ for reacting for 2-4 hours, and cooling the mixed solution to room temperature after the reaction is finished to obtain a zinc sulfide quantum dot solution;
2) mixing the obtained zinc sulfide quantum dot solution with an isometric sodium alginate solution, adding calcium carbonate powder, and uniformly mixing to obtain zinc sulfide quantum dot and sodium alginate electrodeposition liquid;
3) co-depositing the obtained zinc sulfide quantum dots and the sodium alginate electrodeposition liquid on an ITO glass electrode to obtain a quantum dot containing electrode capable of simultaneously carrying out fluorescence and electrochemical detection on metal ions; the co-deposition process is as follows:
an ITO glass electrode is used as an anode, a platinum sheet electrode is used as a cathode, the two electrodes are placed in parallel in zinc sulfide quantum dot and sodium alginate electrodeposition liquid, the distance between the two electrodes is 1-2 cm below the liquid level, the distance between the two electrodes is 0.8-1.2 cm, and a direct current power supply is adopted to apply a voltage of 3.5-4.5V for electrodeposition for 10-20 minutes; and after the electrodeposition is finished, immediately taking the anode ITO glass electrode out of the electrodeposition liquid, washing the surface of the electrode for 3-5 times by using deionized water, and preparing the ITO glass electrode with the quantum dots on the surface.
2. The method for preparing a quantum dot electrode for simultaneously performing fluorescence and electrochemical detection on metal ions according to claim 1, wherein the preparation process of the sodium alginate solution used in the step 2 is as follows:
and adding 4-6 g of sodium alginate solid powder into a beaker filled with 200-300 ml of deionized water, and carrying out magnetic stirring for 4-6 hours to fully dissolve the sodium alginate powder so as to obtain a sodium alginate solution with the mass percentage of 2-3%.
3. The method for preparing a content quantum dot electrode for simultaneously carrying out fluorescence and electrochemical detection on metal ions according to claim 1, wherein 0.08-0.10 g of calcium carbonate powder is added into 8-10 ml of a mixed solution of zinc sulfide quantum dots and sodium alginate in step 2.
4. The method for preparing a quantum dot electrode for simultaneously performing fluorescence and electrochemical detection on metal ions according to claim 1, wherein the ITO glass electrode comprises a pretreatment process of:
the method comprises the steps of cutting ITO glass into a rectangle with the length of 3-5 cm and the width of 0.8-1.5 cm, washing the rectangle with hydrochloric acid, acetone and deionized water with the molar concentration of 0.1-0.15M for 3-5 times, and then placing the rectangle in the deionized water for ultrasonic cleaning for 5-10 minutes.
5. The method for preparing a quantum dot electrode for simultaneously performing fluorescence and electrochemical detection on metal ions as claimed in claim 1, wherein the platinum sheet electrode comprises a pretreatment process of:
washing the surface of the platinum sheet electrode with hydrochloric acid, acetone and distilled water with the molar concentration of 0.1-0.15M for 3-5 times, and then placing the platinum sheet electrode in deionized water for ultrasonic cleaning treatment for 5-10 minutes.
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