Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a dopamine detection method based on copper-zinc-tin-sulfur alloy quantum dots, which has the advantages of low toxicity, good water solubility, high quantum efficiency, good biocompatibility, low cost, simple steps and low requirements on operators and instruments and equipment.
The technical purpose of the invention is realized by the following technical scheme:
dopamine detection method based on copper-zinc-tin-sulfur alloy quantum dots, and detection method based on H3PO4-HAc-H3BO3The method comprises the following steps of forming a dopamine detection system by using a buffer aqueous solution, a copper-zinc-tin-sulfur alloy quantum dot solution and a sample solution to be detected, detecting the fluorescence intensity of the dopamine detection system by using a fluorescence photometer, wherein the fluorescence intensity of the detection system is reduced along with the increase of the concentration of dopamine in the detection system, namely the fluorescence intensity shows a linear quenching relation; comparing with standard curve to obtain the concentration of dopamine in the detection system, detecting the dopamine by using the quantum dot quantitative detection of copper-zinc-tin-sulfur alloy, wherein the fluorescence of the dopamine is linearly quenched in the range of 0.2-300 micromoles/liter, and the fitting equation is that y is 782.572-3.821x +0.007x2,R20.985; y is the fluorescence intensity of the detection system, x is the concentration of dopamine in the detection system, and the lowest detection limit is 92 nmol/L.
In the detection method, after the concentration of the dopamine in the detection system is obtained, the concentration of the dopamine in the solution of the sample to be detected can be converted according to the composition of the detection system.
In the detection method, 50-400 mu L of copper-zinc-tin-sulfur alloy quantum dot solution is sequentially added into a centrifuge tube, and the concentration of the copper-zinc-tin-sulfur alloy quantum dots is 1-5 mmol/L; 100-1000. mu.L of 0.04mol/L H with pH 123PO4-HAc-H3BO3And (3) after the buffer solution is uniformly mixed, adding 40 mu L of sample solution to be detected, adding high-purity water to a constant volume of 4mL, fully mixing, standing for 50-60 minutes, and detecting by using a fluorescence spectrophotometer.
In the detection method, the concentration of the copper-zinc-tin-sulfur alloy quantum dots is preferably 1mmol/L, and the concentration of the copper-zinc-tin-sulfur alloy quantum dots is preferably 200 mu L3PO4-HAc-H3BO3The buffer solution is 200 mu L, 40 mu L of sample solution to be detected is added with high-purity water to be constant volume to 4 mL.
In the detection method, the used excitation wavelength is 300-500 nm; preferably, the excitation wavelength is 345-355 nm; the wavelength of a fluorescence emission peak is 400-600 nm; preferably, the wavelength of the fluorescence emission peak is 460 to 465 nm.
The copper-zinc-tin-sulfur alloy quantum dot is prepared by a hydrothermal preparation method according to the following steps:
step 1, uniformly dispersing copper salt, zinc salt and stannous salt in a solvent to form a dispersion system according to the molar ratio (mass ratio) of copper, zinc and tin of 2:1:1, wherein the solvent consists of water and soluble macromolecules, and the soluble macromolecules are used as a coating stabilizer;
in step 1, the concentration of copper ions ranges from 0.01 to 0.1 mol/L.
In step 1, the copper salt is one of copper chloride, copper nitrate, copper sulfate or copper acetate.
In step 1, the zinc salt is one of zinc chloride, zinc nitrate, zinc sulfate or zinc acetate.
In step 1, the stannous salt is one of stannous chloride, stannous nitrate, stannous sulfate or stannous acetate.
In step 1, the amount of the soluble polymer is 0.0008 to 0.6 part by mass, and the amount of water is 8 to 10 parts by volume, each part by mass being 1g and each part by volume being 1 mL.
In step 1, the soluble polymer is a macromolecular polymer containing amino or carboxyl groups, such as one of polyethyleneimine, polyethylene glycol and polyacrylic acid, and has a number average molecular weight of 10000 or less, such as a number average molecular weight of hundreds, e.g., 200 to 800, preferably 400 to 600; the number average molecular weight is of the order of thousands, e.g. 1000 to 8000, preferably 1000 to 2000.
Step 2, adding an aqueous solution of thiourea into the dispersion system in the step 1 and uniformly dispersing to form Cu2+、Zn2+、Sn2+S and a dispersible polymer; the molar ratio of thiourea to copper ions is at least 2: 1;
in step 2, the thiourea solution is added dropwise at a rate of 1-5 ml per minute.
In step 2, a mechanical stirring mode is adopted for uniform dispersion, and the stirring speed is 100-200 revolutions per minute.
In step 2, the molar ratio of thiourea to copper ions is (2-5): 1.
and 3, introducing inert gas into the dispersion system formed in the step 2 to remove dissolved oxygen, transferring the dispersion system into a reaction kettle, and reacting at 160-200 ℃ to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
In the step 3, the inert gas is nitrogen, helium or argon, and the introducing time is 15-30 min.
In step 3, the reaction is carried out at 180 to 200 ℃ for 6 to 48 hours.
After the copper-zinc-tin-sulfur alloy quantum dot solution is prepared, the solution is a light yellow solution, quantum dots (not powder but colloidal) can be obtained through drying, and the quantum dots can be uniformly dispersed in water. During detection, the water-soluble copper-zinc-tin-sulfur alloy quantum dot (water) solution obtained in the step 3 can be directly used, the concentration of the quantum dots in the solution obtained in the step 3 is calculated according to the feeding proportion, and the concentration of the quantum dots in the final detection system is calculated according to the composition of the detection system.
In the technical scheme of the invention, the temperature of 160-200 ℃ in the hydrothermal reaction provides conditions for generating the copper-zinc-tin-sulfur compound, the molar ratio of copper-zinc-tin-sulfur in the feeding is 2:1:1:4, wherein the element sulfur is slightly excessive, and the reduction and doping effects are simultaneously realized after the element sulfur is added into the system, so that the four elements are kept in stable molar ratio to generate Cu2Zn1Sn1S4Under the protection of nitrogen, dissolved oxygen is removed so that various metal salts are not oxidized to generate alloy compounds. The growth size of the alloy compound is properly controlled by adding PEI, on one hand, PEI is used as a stabilizer, so that a certain distance is reserved between generated alloy compound nano particles, and the quantum characteristic of the alloy compound nano particles with fluorescence performance is realized, and on the other hand, PEI is used as a coating agent, so that amino groups are carried on the surfaces of quantum dots as active functional groups, and the good combination with other substances can be realized.
The prepared quantum dots are characterized by using a TEM, and the synthesized novel quantum dots are uniform in size, nearly spherical in shape and 2 +/-0.5 nm in particle size; the novel quantum dots synthesized by the method are characterized by using an ultraviolet spectrophotometer (instrument model: UV-2600; manufacturing company: Shimadzu corporation, Japan), and can be demonstrated to have ultraviolet absorption at 345-355 nm, which is consistent with the fluorescence excitation wavelength, and emit fluorescence at 460-465 nm after being excited. FTIR is used for characterization, and comparison shows that the surface of the synthesized novel quantum dot is coated with polyethyleneimine, namely, amino is taken as an active group of the quantum dot, which indicates that the soluble polymer is successfully coated with the stable quantum dot, and a functional group (amino, hydroxyl or carboxyl) is taken as an active group.
Compared with the prior art, the invention provides a method for directly synthesizing hydrophilic Copper Zinc Tin Sulfide (CZTS) quantum dots in an aqueous solution. Copper zinc tin sulfide is widely applied to solar cell thin film materials, but regulation and synthesis of copper zinc tin sulfide are rarely reported to be used as quantum dots. The synthesis method provided by the invention has the advantages of low cost, simple steps and low requirements on operators and instruments and equipment, and the obtained copper-zinc-tin-sulfur quantum dots are uniform, stable, low in toxicity, good in water solubility, high in quantum efficiency and good in biocompatibility, and are good fluorescent markers.
The invention uses water-soluble inorganic salts of copper, zinc and stannous to prepare the water-soluble copper-zinc-tin-sulfur (CZTS) alloy quantum dots in a water phase. The method has the advantages of low cost, simple steps and low requirements on operators and instruments and equipment, and provides possibility for large-scale synthesis and preparation. The synthesized copper-zinc-tin-sulfur quantum dots are uniform, stable, low in toxicity, good in water solubility, high in quantum efficiency and good in biocompatibility, and are good fluorescent markers. The method for detecting the dopamine by using the label-free and non-modified alloy quantum dots as the fluorescent probe provided by the invention realizes the purpose of quantitatively detecting the dopamine without labels by preparing the specific fluorescent probe by utilizing the specific quenching phenomenon of the dopamine on the quantum dots, has high sensitivity and high accuracy, and has good application prospect in the detection of various actual samples.
Detailed Description
The above features and advantages of the present invention will become more apparent and readily appreciated from the following description of the exemplary embodiments thereof taken in conjunction with the accompanying drawings. The present invention will be described in further detail with reference to specific examples. The high-purity water is purchased from a water resource and water environment key laboratory (sold to the outside) of Tianjin university, the polyethyleneimine is purchased from Beijing Michalin biological reagent company Limited, and other inorganic reagents are purchased from Tianjin Kovar company Limited. Dispersing by a mechanical stirring device, wherein the stirring speed is 150 revolutions per minute.
Example 1-preparation of water-soluble Copper Zinc Tin Sulfide (CZTS) quantum dots is divided into the following steps:
A. 0.0008g of polyethyleneimine (PEI, number average molecular weight 10000) is weighed and dissolved in 9mL of water at room temperature of 20 ℃ to serve as a solvent of a salt solution;
B. taking the mass ratio of copper, zinc and tin as 2:1:1, dissolving copper chloride, zinc chloride and stannous chloride in the solution, fully stirring to uniformly disperse the copper chloride, the zinc chloride and the stannous chloride in the solution to prepare the copper-zinc-tin-containing copper-tin alloy2+、Zn2+、Sn2+The solution of (1), wherein the concentration range of copper ions is 0.04 mol/L;
C. slowly adding 5ml of thiourea aqueous solution into the system at a molar ratio of thiourea to copper ions of 2:1 per minute, and fully stirring to obtain Cu2+、Zn2+、Sn2+The coordination compound with the polymer PEI is well dispersed in the solution;
D. introducing nitrogen into the solution for 15 minutes, removing dissolved oxygen, transferring the solution into a reaction kettle, and heating the solution at the temperature of 180 ℃ for 48 hours to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
Example 2-preparation of water-soluble Copper Zinc Tin Sulfide (CZTS) quantum dots is divided into the following steps:
A. 0.2058g of polyethyleneimine (PEI, number average molecular weight 10000) is weighed and dissolved in 9mL of water at room temperature of 20 ℃ to serve as a solvent of a salt solution;
B. taking the mass ratio of copper, zinc and tin as 2:1:1, dissolving copper nitrate, zinc nitrate and stannous nitrate in the solution, fully stirring to uniformly disperse the copper nitrate, the zinc nitrate and the stannous nitrate in the solution to prepare the copper-zinc-tin-containing copper alloy2+、Zn2+、Sn2+The solution of (1), wherein the concentration range of copper ions is 0.04 mol/L;
C. slowly adding 5ml of thiourea aqueous solution into the system at a molar ratio of thiourea to copper ions of 2:1 per minute, and fully stirring to obtain Cu2+、Zn2+、Sn2+The coordination compound with the polymer PEI is well dispersed in the solution;
D. introducing nitrogen into the solution for 15 minutes, removing dissolved oxygen, transferring the solution into a reaction kettle, and heating the solution at the temperature of 180 ℃ for 48 hours to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
Example 3-preparation of water-soluble Copper Zinc Tin Sulfide (CZTS) quantum dots is divided into the following steps:
A. 0.3860g of polyethyleneimine (PEI, number average molecular weight 10000) is weighed and dissolved in 9mL of water at room temperature of 20 ℃ to serve as a solvent of a salt solution;
B. dissolving copper sulfate, zinc sulfate and stannous sulfate in the solution at a ratio of copper to zinc to stannum of 2:1:1, stirring to disperse the copper sulfate, zinc sulfate and stannous sulfate in the solution uniformly, and preparing the copper-zinc-stannum alloy containing Cu2+、Zn2+、Sn2+The solution of (1), wherein the concentration range of copper ions is 0.04 mol/L;
C. slowly adding 5ml of thiourea aqueous solution into the system at a molar ratio of thiourea to copper ions of 2:1 per minute, and fully stirring to obtain Cu2+、Zn2+、Sn2+The coordination compound with the polymer PEI is well dispersed in the solution;
D. introducing nitrogen into the solution for 15 minutes, removing dissolved oxygen, transferring the solution into a reaction kettle, and heating the solution at the temperature of 180 ℃ for 48 hours to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
Example 4-preparation of water-soluble Copper Zinc Tin Sulfide (CZTS) quantum dots is divided into the following steps:
A. 0.4280g of polyethyleneimine (PEI, number average molecular weight 10000) is weighed and dissolved in 9mL of water at room temperature of 20 ℃ to serve as a solvent of a salt solution;
B. taking the mass ratio of copper, zinc and tin as 2:1:1, dissolving copper acetate, zinc acetate and stannous acetate in the solution, fully stirring to uniformly disperse the copper acetate, zinc acetate and stannous acetate in the solution to prepare the copper-zinc-tin-containing copper-zinc-tin alloy2+、Zn2+、Sn2+The solution of (1), wherein the concentration range of copper ions is 0.04 mol/L;
C. slowly adding 5ml of thiourea aqueous solution into the system at a molar ratio of thiourea to copper ions of 2:1 per minute, and fully stirring to obtain Cu2+、Zn2+、Sn2+Coordination compounds with Polymer PEI and good DispersionIn solution;
D. introducing nitrogen into the solution for 15 minutes, removing dissolved oxygen, transferring the solution into a reaction kettle, and heating the solution at the temperature of 180 ℃ for 48 hours to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
Example 5-preparation of water-soluble Copper Zinc Tin Sulfide (CZTS) quantum dots was divided into the following steps:
A. 0.5640g of polyethyleneimine (PEI, number average molecular weight 10000) is weighed and dissolved in 9mL of water at room temperature of 20 ℃ to serve as a solvent of a salt solution;
B. dissolving copper acetate, zinc sulfate and stannous nitrate in the solution at a ratio of 2:1:1, stirring to disperse the mixture uniformly in the solution to obtain the final product containing Cu2+、Zn2+、Sn2+The solution of (1), wherein the concentration range of copper ions is 0.04 mol/L;
C. slowly adding 5ml of thiourea aqueous solution into the system at a molar ratio of thiourea to copper ions of 2:1 per minute, and fully stirring to obtain Cu2+、Zn2+、Sn2+The coordination compound with the polymer PEI is well dispersed in the solution;
D. introducing nitrogen into the solution for 15 minutes, removing dissolved oxygen, transferring the solution into a reaction kettle, and heating the solution at the temperature of 180 ℃ for 48 hours to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
Example 6-preparation of water-soluble Copper Zinc Tin Sulfide (CZTS) quantum dots is divided into the following steps:
A. 0.5640g of polyethyleneimine (PEI, number average molecular weight 10000) is weighed and dissolved in 9mL of water at room temperature of 25 ℃ to serve as a solvent of a salt solution;
B. dissolving copper chloride, zinc sulfate and stannous nitrate in the solution at a ratio of 2:1:1, stirring to disperse the copper chloride, zinc sulfate and stannous nitrate in the solution uniformly, and preparing the copper-zinc-tin-containing copper-zinc-tin alloy2+、Zn2+、Sn2+The solution of (1), wherein the concentration range of copper ions is 0.04 mol/L;
C. then, an aqueous solution of thiourea (3 ml per minute) was slowly added to the above systemThe molar ratio of the added copper ions to the added copper ions is 2:1, and Cu is formed after full stirring2+、Zn2+、Sn2+The coordination compound with the polymer PEI is well dispersed in the solution;
D. introducing nitrogen into the solution for 30 minutes, removing dissolved oxygen, transferring the solution into a reaction kettle, and heating the solution at the temperature of 180 ℃ for 48 hours to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
Example 7-preparation of water-soluble Copper Zinc Tin Sulfide (CZTS) quantum dots was divided into the following steps:
A. 0.5640g of polyethyleneimine (PEI, number average molecular weight 10000) is weighed and dissolved in 9mL of water at room temperature of 25 ℃ to serve as a solvent of a salt solution;
B. dissolving copper chloride, zinc sulfate and stannous nitrate in the solution at a ratio of 2:1:1, stirring to disperse the copper chloride, zinc sulfate and stannous nitrate in the solution uniformly, and preparing the copper-zinc-tin-containing copper-zinc-tin alloy2+、Zn2+、Sn2+The solution of (1), wherein the concentration range of copper ions is 0.04 mol/L;
C. slowly adding 3ml of thiourea aqueous solution into the system at a molar ratio of thiourea to copper ions of 2:1 per minute, and fully stirring to obtain Cu2+、Zn2+、Sn2+The coordination compound with the polymer PEI is well dispersed in the solution;
D. introducing nitrogen into the solution for 30 minutes, removing dissolved oxygen, transferring the solution into a reaction kettle, and heating the solution at the temperature of 180 ℃ for 7 hours to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
Example 8-preparation of water-soluble Copper Zinc Tin Sulfide (CZTS) quantum dots is divided into the following steps:
A. 0.5640g of polyethyleneimine (PEI, number average molecular weight 10000) is weighed and dissolved in 9mL of water at room temperature of 25 ℃ to serve as a solvent of a salt solution;
B. dissolving copper chloride, zinc sulfate and stannous nitrate in the solution at a ratio of 2:1:1, stirring to disperse the copper chloride, zinc sulfate and stannous nitrate in the solution uniformly, and preparing the copper-zinc-tin-containing copper-zinc-tin alloy2+、Zn2+、Sn2+The solution (a) of (b) is,wherein the concentration range of the copper ions is 0.04 mol/L;
C. slowly adding 3ml of thiourea aqueous solution into the system at a molar ratio of thiourea to copper ions of 2:1 per minute, and fully stirring to obtain Cu2+、Zn2+、Sn2+The coordination compound with the polymer PEI is well dispersed in the solution;
D. introducing nitrogen into the solution for 30 minutes, removing dissolved oxygen, transferring the solution into a reaction kettle, and heating the solution at the temperature of 180 ℃ for 15 hours to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
Example 9-preparation of water-soluble Copper Zinc Tin Sulfide (CZTS) quantum dots the following steps were divided:
A. 0.5640g of polyethyleneimine (PEI, number average molecular weight 10000) is weighed and dissolved in 9mL of water at room temperature of 25 ℃ to serve as a solvent of a salt solution;
B. dissolving copper chloride, zinc sulfate and stannous nitrate in the solution at a ratio of 2:1:1, stirring to disperse the copper chloride, zinc sulfate and stannous nitrate in the solution uniformly, and preparing the copper-zinc-tin-containing copper-zinc-tin alloy2+、Zn2+、Sn2+The solution of (1), wherein the concentration range of copper ions is 0.04 mol/L;
C. slowly adding 3ml of thiourea aqueous solution into the system at a molar ratio of thiourea to copper ions of 2:1 per minute, and fully stirring to obtain Cu2+、Zn2+、Sn2+The coordination compound with the polymer PEI is well dispersed in the solution;
D. introducing nitrogen into the solution for 30 minutes, removing dissolved oxygen, transferring the solution into a reaction kettle, and heating the solution at the temperature of 180 ℃ for 30 hours to obtain the water-soluble copper-zinc-tin-sulfur alloy quantum dot solution.
In the above examples, the changes of the luminescent properties were examined by increasing the amount of the coating stabilizer and prolonging the hydrothermal reaction time, respectively (1) increasing the amount of the coating stabilizer (i.e., soluble polymer) and adjusting the luminescent position of the copper zinc tin sulfur alloy quantum dot (from the uv region to the blue visible region) by adjusting the amount of the coating stabilizer; (2) the hydrothermal reaction time is prolonged, the luminous intensity of the quantum dots is enhanced, and the luminous intensity of the copper-zinc-tin-sulfur alloy quantum dots can be regulated and controlled by regulating the hydrothermal reaction time.
Firstly, the selectivity of the copper-zinc-tin-sulfur alloy quantum dot to dopamine is examined
(1) H at 0.04mol/L, 25 ℃, pH 12.003PO4-HAc-H3BO3Preparation of a buffer solution: preparing 100mL of mixed solution of three acids (the concentration is 0.04mol/L) of phosphoric acid, boric acid and acetic acid; adding sodium hydroxide solution with different volumes (the concentration is 0.2 mol/L); thirdly, the pH value is adjusted to 12.00 by an acidimeter and then the mixture is stored in a refrigerator for standby.
(2) 200 mu L of copper-zinc-tin-sulfur alloy quantum dot solution and 200 mu L of 0.04mol/L H are sequentially added into a centrifuge tube3PO4-HAc-H3BO3After the solution is uniformly mixed, 40 mu L of dopamine, threonine, methionine, leucine, isoleucine, histidine and lysine with the same concentration are added, and high-purity water is added to the mixture to reach a constant volume of 4 mL. Mixing well, standing for 60min, and detecting with fluorescence spectrophotometer. As can be seen from FIG. 9, the fluorescent probe (copper zinc tin sulfur alloy quantum dot) of the present invention has specific recognition on dopamine.
Then looking at the fluorescence intensity of the copper-zinc-tin-sulfur alloy quantum dots aiming at the dopamine with different concentrations
(1) H at 0.04mol/L, 25 ℃, pH 12.003PO4-HAc-H3BO3Preparation of a buffer solution: preparing 100mL of mixed solution of three acids (the concentration is 0.04mol/L) of phosphoric acid, boric acid and acetic acid; adding sodium hydroxide solution with different volumes (the concentration is 0.2 mol/L); thirdly, the pH value is adjusted to 12.00 by an acidimeter and then the mixture is stored in a refrigerator for standby.
(2) 200 mu L of copper-zinc-tin-sulfur alloy quantum dot solution and 200 mu L of 0.04mol/L H are sequentially added into a centrifuge tube3PO4-HAc-H3BO3After the solutions are mixed uniformly, 40 mu L of dopamine with different concentrations is added, and then high-purity water is added to the mixture to reach a constant volume of 4 mL. Mixing and standingAfter standing for 60 minutes, the reaction mixture was measured with a fluorescence spectrophotometer. As shown in fig. 6 and 8, the fluorescence intensity of the quantum dots is gradually reduced with the increase of the dopamine concentration, and the color of the alloy quantum dot solution is gradually deepened after dopamine with different concentrations is added.
The establishment of a standard curve for quantitatively detecting dopamine is carried out by adjusting the pH value of the buffer (water) solution and the adding amount of the quantum dot solution (prepared in example 6) to optimize the conditions for detecting dopamine:
example 1
(1) H at 0.04mol/L, 25 ℃, pH 6.003PO4-HAc-H3BO3Preparation of a buffer solution: preparing 100mL of mixed solution of three acids (the concentration is 0.04mol/L) of phosphoric acid, boric acid and acetic acid; ② adding sodium hydroxide water solution (the concentration is 0.2mol/L) with different volumes; regulating the pH value to 6.00 by an acidimeter and storing in a refrigerator for later use.
(2) 200 mu L of copper-zinc-tin-sulfur alloy quantum dot solution and 200 mu L of 0.04mol/L H are sequentially added into a centrifuge tube3PO4-HAc-H3BO3After the solutions were mixed well, 40. mu.L of a series of gradient concentration (100 nM-50. mu.M) dopamine solutions was added thereto, and then high purity water was added to make a volume of 4 mL. Mixing well, standing for 60min, and detecting with fluorescence spectrophotometer.
(3) And establishing a standard curve between the concentration of the dopamine and the fluorescence intensity by taking the concentration of the dopamine aqueous solution as an abscissa and the measured fluorescence intensity of the mixed solution as an ordinate.
Example 2
(1) H at 0.04mol/L, 25 ℃, pH 12.003PO4-HAc-H3BO3Preparation of a buffer solution: preparing 100mL of mixed solution of three acids (the concentration is 0.04mol/L) of phosphoric acid, boric acid and acetic acid; adding sodium hydroxide solution with different volumes (the concentration is 0.2 mol/L); thirdly, the pH value is adjusted to 12.00 by an acidimeter and then the mixture is stored in a refrigerator for standby.
(2) 50 mu L of copper-zinc-tin-sulfur alloy quantum dot solution and 200 mu L of 0.04mol/L H are sequentially added into a centrifuge tube3PO4-HAc-H3BO3After the solutions were mixed well, 40. mu.L of a series of gradient concentration (100 nM-50. mu.M) dopamine solutions was added thereto, and then high purity water was added to make a volume of 4 mL. After mixing well and standing for 40 minutes, the mixture was examined by a fluorescence spectrophotometer.
(3) And establishing a standard curve between the concentration of the dopamine and the fluorescence intensity by taking the concentration of the dopamine aqueous solution as an abscissa and the measured fluorescence intensity of the mixed solution as an ordinate.
Example 3
(1) H at 0.04mol/L, 25 ℃, pH 12.003PO4-HAc-H3BO3Preparation of a buffer solution: preparing 100mL of mixed solution of three acids (the concentration is 0.04mol/L) of phosphoric acid, boric acid and acetic acid; adding sodium hydroxide solution with different volumes (the concentration is 0.2 mol/L); thirdly, the pH value is adjusted to 12.00 by an acidimeter and then the mixture is stored in a refrigerator for standby.
(2) 200 mu L of copper-zinc-tin-sulfur alloy quantum dot solution and 1000 mu L of 0.04mol/L H are sequentially added into a centrifuge tube3PO4-HAc-H3BO3After the solutions were mixed well, 40. mu.L of a series of gradient concentration (100 nM-50. mu.M) dopamine solutions was added thereto, and then high purity water was added to make a volume of 4 mL. After mixing well and standing for 50 minutes, the mixture was examined by a fluorescence spectrophotometer.
(3) And establishing a standard curve between the concentration of the dopamine and the fluorescence intensity by taking the concentration of the dopamine aqueous solution as an abscissa and the measured fluorescence intensity of the mixed solution as an ordinate.
Example 4
(1) H at 0.04mol/L, 25 ℃, pH 12.003PO4-HAc-H3BO3Preparation of a buffer solution: preparing 100mL of mixed solution of three acids (the concentration is 0.04mol/L) of phosphoric acid, boric acid and acetic acid; adding sodium hydroxide solution with different volumes (the concentration is 0.2 mol/L); thirdly, the pH value is adjusted to 12.00 by an acidimeter and then the mixture is stored in a refrigerator for standby.
(2) 200 mu L of copper-zinc-tin-sulfur alloy quantum dot solution and 200 mu L of 0.04mol/L H are sequentially added into a centrifuge tube3PO4-HAc-H3BO3After the solution was mixed well, 40. mu.L of one was added theretoDopamine solution with series gradient concentration (100nM-50 μ M) is added with high-purity water to be constant volume to 4 mL. Mixing well, standing for 60min, and detecting with fluorescence spectrophotometer.
(3) And establishing a standard curve between the concentration of the dopamine and the fluorescence intensity by taking the concentration of the dopamine aqueous solution as an abscissa and the measured fluorescence intensity of the mixed solution as an ordinate.
Through optimization, the standard curve detection aiming at the dopamine can be realized in the embodiments 1 to 4, and the detection requirement of the fluorescence intensity can be considered, and H can be considered3PO4-HAc-H3BO3The pH of the buffer solution is 12, the copper-zinc-tin-sulfur alloy quantum dot solution is 200 mu L, the solution is kept for 50-60 min, the standard curve is shown in figure 7, the concentration of dopamine in the detection system is linearly quenched (quenched) in the range of 0.2-300 micromole/liter, and the fitting equation is that y is 782.572-3.821x +0.007x2,R20.985; y is the fluorescence intensity of the detection system, and x is the concentration of dopamine in the detection system. After the dopamine concentration corresponding to the fluorescence intensity is determined by comparing the standard curves, the dopamine concentration in the sample to be detected is determined by the detection system.
The patent is funded by a first level project ZX110185 of the national science foundation project 2137509, an innovative talent culture project of Tianjin ' 131 ', a youth project JCQNJC05800 of the Tianjin's natural science foundation, a project 52XB1510 of the Tianjin university doctor foundation and a project ZX0471601109 of the Tianjin university conversion of scientific and technological achievements.
The preparation method can be adjusted according to the process parameters recorded in the content of the invention, the preparation of the water-soluble copper-zinc-tin-sulfur alloy quantum dots and the detection of dopamine can be realized, and basically consistent performance is shown. The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.