A method for detecting toxic heavy metals

Abstract

The invention discloses a method for detecting toxic heavy metals, belonging to the technical field of heavy metal detection. The method comprises the following specific detection steps: Step 1. Stirring bovine serum albumin and chloroauric acid in an oil bath, and preparing gold nanoclusters in an alkaline solution after the reaction is completed; Step 2. Preparing metal organic skeleton-coated gold nanoclusters by gold nanoclusters, polyethyleneimine, 2-methylimidazole and zinc nitrate. The metal organic skeleton-coated gold nanoclusters prepared by the invention can sensitively detect heavy metal ions in the environment, and the detection is convenient and fast, low in cost, quick in reaction, and high in specificity, and can achieve the detection of heavy metal ions Cu 2+ and Co 2+ Specific detection without interference from other metal ions and other substances.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy metal detection, and in particular relates to a method for detecting toxic heavy metals. Background Art

[0002] With the development of modern industry and agriculture, the pollution of the environment by metal ions has become a global problem. Copper and cobalt, as representative heavy metal materials, are widely used due to their excellent performance. However, due to their wide application in mining, printing and dyeing, and agricultural production, excessive accumulation may cause serious environmental pollution and ecosystem imbalance. At the same time, copper ions can enter the human body through the food chain and exist for a long time, causing health hazards that cannot be ignored, such as Alzheimer's disease, Wilson's disease, and Menkes syndrome. Studies have shown that if people are exposed to cobalt ions for a long time, it will cause abnormal increase in red blood cells and changes in serum protein composition, damage to some organs, and even chromosome aberrations and normal cell degeneration. Therefore, in modern society, more and more attention is paid to the remediation of heavy metal pollution in the environment. Before the remediation of heavy metal pollution, it is necessary to detect heavy metals in the environment.

[0003] In recent years, fluorescence analysis has gradually become a popular and important analyte detection technology due to its advantages of simple manufacturing, simple operation, high sensitivity, accuracy and selectivity. Various new fluorescent nanomaterials have been developed for the detection of metal ions. However, some materials still have inherent defects, such as the toxicity of quantum dots and the difficulty in purifying carbon dots, which limit their practical applications. Therefore, it is necessary to establish a simple, accurate and safe method to determine metal ions in actual samples. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a simple, accurate and safe heavy metal detection method.

[0005] The technical solution adopted to solve the above technical problems is: a toxic heavy metal detection method, including the following specific detection steps:

[0006] Step 1. BSA and chloroauric acid are reacted by stirring in an oil bath, and after the reaction is completed, gold nanoclusters are prepared in an alkaline solution;

[0007] Step 2. Prepare metal organic framework-coated gold nanoclusters by using gold nanoclusters, polyethyleneimine, 2-methylimidazole and zinc nitrate;

[0008] Step 3. Take 300-310 μL of the heavy metal sample to be tested, add 500-510 μL of metal organic framework-coated gold nanoclusters to mix, fill the volume to 1 mL with water, measure the fluorescence intensity, and determine the heavy metal content by the fluorescence intensity;

[0009] Cu in heavy metal samples 2+ The concentration and the fluorescence intensity of the metal organic framework-coated gold nanoclusters are linearly related in the concentration range of 0.1-100 μM, and the regression equation is y=-2.60x+768.544(R 2 =0.995), LOD is 0.073 μM, x is Cu 2+ concentration, y is the fluorescence intensity;

[0010] Co in heavy metal samples 2+ The concentration and the fluorescence intensity of the metal organic framework-coated gold nanoclusters are linearly related in the concentration range of 0.1-100 μM, and the regression equation is y=-11.383x+2211.781(R 2 =0.992), LOD is 0.082 μM, x is Co 2+ concentration, and y is the fluorescence intensity.

[0011] Furthermore, the specific steps of step one are as follows:

[0012] Aa. Mix bovine serum albumin and chloroauric acid by ultrasonication, place in an oil bath at 50-55°C and stir for 2-3 minutes to react;

[0013] Ab. After the reaction is completed, quickly add alkaline solution and continue the reaction for 6-7 hours until the solution color turns brown to obtain gold nanoclusters.

[0014] Furthermore, the specific steps of step 2 are as follows:

[0015] Ba. Add zinc nitrate dropwise to the gold nanoclusters in step 1 and stir for 2-3 minutes to obtain solution 1;

[0016] Bb. Take polyethyleneimine and 2-methylimidazole and stir for 2-3 minutes to obtain solution 2;

[0017] Bc. Solution 1 and solution 2 were mixed, incubated for 12-13 hours, washed three times with methanol, and dried in an oven at 40-45°C to obtain metal organic framework-coated gold nanoclusters;

[0018] Bd. Disperse metal organic framework-encapsulated gold nanoclusters in 0.01 mol·L -1 Store in PBS.

[0019] Furthermore, the concentration of bovine serum albumin in step 1 is 50 mg mL -1 , and the dosage is 15-18mL.

[0020] Furthermore, the concentration of chloroauric acid in step 1 is 10 mmol·L -1, the dosage of chloroauric acid is 10.0-10.3mL.

[0021] Furthermore, the alkaline solution in step 1 is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 1 mol·L -1 , the dosage of sodium hydroxide solution is 1.0-1.5ml.

[0022] Furthermore, in step 2, the amount of the gold nanoclusters used is 2.5-2.8 ml, the amount of polyethyleneimine used is 2.0-2.4 ml, the amount of 2-methylimidazole used is 4.0-4.5 ml, and the amount of zinc nitrate used is 4.0-4.4 ml, and the purity of the polyethyleneimine and 2-methylimidazole is analytical grade.

[0023] The beneficial effects of the present invention are as follows: the present invention synthesizes gold nanoclusters modified with bovine serum albumin in aqueous solution by a simple and green method; the bovine serum albumin (BSA) on the surface of the gold nanoclusters can promote crystallization and induce the formation of a protective molecular sieve-imidazole skeleton coating under mild conditions; the gold nanoclusters thus obtained show stable emission in a wide pH range; at the same time, the metal organic framework of the present invention, as a porous material, has a large porosity, a large internal specific surface area, good chemical stability and thermal stability, and the detection stability is greatly improved, and it can be used for Cu 2+ and Co 2+ Specific detection has strong pertinence for heavy metal poisoning detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The excitation spectrum and emission spectrum of gold nanoclusters (a), transmission electron microscopy (b) and high-resolution transmission electron microscopy (c);

[0025] Figure 2 The fluorescence intensity bar graph of gold nanoclusters after adding different volumes of bovine serum albumin;

[0026] Figure 3 The scanning electron microscope image (a) of the metal framework molecular sieve-imidazole framework, the scanning electron microscope image (b) of the fluorescent nanocomposite material, the X-ray diffraction image (c) and the Zeta potential image (d);

[0027] Figure 4 The fluorescence emission spectra at different excitation wavelengths (a), excitation spectra and emission spectra (b); molecular sieve-imidazole framework, metal organic framework-coated gold nanoclusters, gold nanoclusters emission spectra (c), and fluorescence stability of metal organic framework-coated gold nanoclusters (d);

[0028] Figure 5 For different concentrations of Cu 2+ Fluorescence emission spectra of fluorescent nanocomposites in the presence of (a), Cu2+ Linear relationship between concentration and fluorescence intensity of fluorescent nanocomposites (b), different concentrations of Co 2+ Fluorescence emission spectra of fluorescent nanocomposites in the presence of (c) and Co 2+ Linear relationship between concentration and fluorescence intensity of fluorescent nanocomposites (d);

[0029] Figure 6 This is a comparison chart of the degree of fluorescence intensity quenching of fluorescent nanocomposites after adding different interfering substances. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] like Figure 1 As shown, a toxic heavy metal detection method of this embodiment includes the following specific detection steps:

[0032] Step 1. BSA and chloroauric acid are reacted by stirring in an oil bath. After the reaction is completed, gold nanoclusters are prepared in an alkaline solution. The specific steps are as follows:

[0033] Aa. Add 15mL of 50mg mL -1 10 ml of bovine serum albumin with a concentration of 10 mmol L -1 The chloroauric acid was mixed by ultrasonic wave and placed in an oil bath at 50°C and stirred for 2 min to react;

[0034] After the reaction is completed, an alkaline solution is quickly added and the reaction is continued for 6 hours until the solution turns brown to obtain gold nanoclusters. The alkaline solution is a sodium hydroxide solution with a concentration of 1 mol·L -1 , the amount of sodium hydroxide solution used is 1ml.

[0035] Step 2. Prepare metal organic framework-coated gold nanoclusters by using gold nanoclusters, polyethyleneimine, 2-methylimidazole and zinc nitrate. The specific scheme is as follows:

[0036] Ba. Add zinc nitrate dropwise to the gold nanoclusters in step 1 and stir for 2 min to obtain solution 1;

[0037] Bb. Take polyethyleneimine and 2-methylimidazole and stir for 2 minutes to obtain solution 2;

[0038] Bc. Solution 1 and solution 2 were mixed, incubated for 12 h, washed three times with methanol, and dried in an oven at 40 ° C to obtain metal organic framework-coated gold nanoclusters;

[0039] Bd. Disperse metal organic framework-encapsulated gold nanoclusters in 0.01 mol·L -1 PBS preservation;

[0040] The amount of gold nanoclusters used was 2 ml, the amount of polyethyleneimine used was 2 ml, the amount of 2-methylimidazole used was 4 ml, and the amount of zinc nitrate used was 4 ml.

[0041] Step 3. Take 30 μL of the heavy metal sample to be tested, add 500 μL of metal organic framework-coated gold nanoclusters to mix, fill the volume to 1 mL with water, measure the fluorescence intensity, and determine the heavy metal content;

[0042] Cu in heavy metal samples 2+ The concentration and the fluorescence intensity of the metal organic framework-coated gold nanoclusters are linearly related in the concentration range of 0.1-100 μM, and the regression equation is y=-2.60x+768.544(R 2 =0.995), LOD is 0.073 μM, x is Cu 2+ concentration, y is the fluorescence intensity;

[0043] Co in heavy metal samples 2+ The concentration and the fluorescence intensity of metal organic framework-coated gold nanoclusters showed a linear relationship in the concentration range of 0.1-100 μM, and the regression equation was y = -11.383x + 2211.781 (R2 = 0.992), the LOD was 0.082 μM, x was the Co2+ concentration, and y was the fluorescence intensity;

[0044] The purity of polyethyleneimine and 2-methylimidazole was analytical grade.

[0045] Characterization of Gold Nanoclusters:

[0046] like Figure 1 As shown in (a), the gold nanoclusters show a maximum emission at 670 nm under excitation at 470 nm. Figure 1 As shown in (b), gold nanoclusters are well dispersed in water, e.g. Figure 1 (c) The lattice spacing of the gold nanoclusters shown is 0.22 nm.

[0047] Characterization of Metal-Organic Framework-Encapsulated Gold Nanoclusters:

[0048] like Figure 3 As shown in (a), the molecular sieve-imidazole framework shows a rhombic dodecahedron structure; Figure 3 As shown in b, the metal organic framework-coated gold nanoclusters show a rhombic dodecahedron structure, but the size is slightly smaller than that of the molecular sieve-imidazole framework. Figure 3As shown in (c), the X-ray diffraction pattern of the molecular sieve-imidazole framework has a reflection peak at 2θ=7.3°, which is related to the 110 plane, indicating that its crystal is composed of 12 {110} planes. The X-ray diffraction pattern of the metal organic framework-coated gold nanoclusters has a reflection peak at 2θ=7.3°, which is related to the 110 plane, proving that the metal organic framework-coated gold nanoclusters are similar to the crystal structure of the molecular sieve-imidazole framework, such as Figure 3 As shown in (d), the Zeta potential of the gold nanoclusters is negative, the Zeta potential of the molecular sieve-imidazole framework is positive, and the Zeta potential of the nanocomposite material is positive, but lower than that of the molecular sieve-imidazole framework.

[0049] like Figure 4 As shown in Figures 4(a) and 4(b), under the excitation wavelength of 300-480nm, the fluorescence emission of the metal organic framework-encapsulated gold nanoclusters is always at 670nm, does not red-shift with the change of the excitation wavelength, and has the strongest fluorescence emission under the excitation wavelength of 370nm. Figure 4 As shown in (c), under 370nm excitation, the molecular sieve-imidazole framework has no fluorescence emission. Compared with pure gold nanoclusters, the fluorescence of the gold nanoclusters encapsulated by the molecular sieve-imidazole framework is significantly enhanced. Figure 4 As shown in (d), the metal organic framework-encapsulated gold nanoclusters can stably maintain their fluorescence properties for 1 h, indicating that they have anti-photobleaching properties.

[0050] Quantitative Detection of Cu by Metal-Organic Framework-Encapsulated Gold Nanoclusters 2+ and Co 2+ :

[0051] 500 μL of metal organic framework-coated gold nanoclusters were mixed with 300 μL of Cu 2+ and Co 2+ Mix, fill volume to 1 mL with water and measure fluorescence intensity.

[0052] like Figure 5 As shown in (a), the fluorescence intensity of metal organic framework-coated gold nanoclusters at 670 nm increases with the increase of Cu 2+ decreases with increasing concentration, such as Figure 5 As shown in (b), Cu 2+ The concentration and the fluorescence intensity of the metal organic framework-coated gold nanoclusters are linearly related in the concentration range of 0.1-100 μM, and the regression equation is y=-2.60x+768.544(R 2 =0.995), LOD is 0.073 μM. Figure 5 As shown in (c), the fluorescence intensity of metal organic framework-coated gold nanoclusters at 670 nm increases with the increase of Co 2+ decreases with increasing concentration, such as Figure 5 As shown in (d), Co2+ The concentration and the fluorescence intensity of the metal organic framework-coated gold nanoclusters are linearly related in the concentration range of 0.1-100 μM, and the regression equation is y=-11.383x+2211.781(R 2 =0.992), and the LOD was 0.082 μM.

[0053] Metal-organic framework-coated gold nanoclusters for Cu 2+ and Co 2+ Selectivity:

[0054] Ca 2+ , K + , Fe 3+ 、Na + , Hg 2+ , Pb 2+ Mg 2+ 、Ni 2+ 、Zn 2+ 、SO4 2- , C l - PO4 3- , alanine, cysteine, threonine, lysine, aspartic acid, glucose, sucrose, lactose, ascorbic acid, uric acid and other interfering substances were added to the fluorescent nanocomposite material, and the concentration of each substance was 10 μM, such as Figure 6 As shown, in Cu 2+ and Co 2+ In the presence of interfering substances, the fluorescence intensity is quenched to the minimum, while in the presence of interfering substances, the fluorescence intensity does not change significantly. The results show that the metal organic framework-coated gold nanoclusters have an important effect on the Cu 2+ and Co 2+ The detection has good selectivity.

[0055] The applicability of metal organic framework-coated gold nanoclusters was investigated using the standard addition method:

[0056] As shown in Table 1, Cu 2+ The recovery rate was 96.91-103.23%, and the relative standard deviation was less than 4.3% (n=3). As shown in Table 2, Co 2+ The recovery rate was 98.45-101.09%, and the relative standard deviation was less than 3.2% (n=3). The results showed that the detection method had good practicability in actual sample detection.

[0057] Table 1Cu 2+ The spike recovery

[0058]

[0059] Table 2Co 2+ The spike recovery

[0060]

[0061]

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention.

Claims

1. A method for detecting toxic heavy metals, characterized in that: The specific detection steps include the following: Step 1. BSA and chloroauric acid are reacted by stirring in an oil bath, and after the reaction is completed, gold nanoclusters are prepared in an alkaline solution; Step 2. Prepare metal organic framework-coated gold nanoclusters by using gold nanoclusters, polyethyleneimine, 2-methylimidazole and zinc nitrate; Step 3. Take 300-310 μL of the heavy metal sample to be tested, add 500-510 μL of metal organic framework-coated gold nanoclusters to mix, fill the volume to 1 mL with water, measure the fluorescence intensity, and judge the heavy metal content by the fluorescence intensity. and Specific detection of Heavy metal samples The concentration and the fluorescence intensity of the metal organic framework-coated gold nanoclusters are linearly related in the concentration range of 0.1-100 μM, and the regression equation is y=-2.60x+768.544( =0.995), LOD is 0.073 μM, x is concentration, y is the fluorescence intensity; Heavy metal samples The concentration and the fluorescence intensity of the metal organic framework-coated gold nanoclusters are linearly related in the concentration range of 0.1-100 μM, and the regression equation is y=-11.383x+2211.781( =0.992), LOD is 0.082 μM, x is concentration, y is the fluorescence intensity; The specific steps of step one are as follows: Aa. Mix bovine serum albumin and chloroauric acid by ultrasonication, place in an oil bath at 50-55°C and stir for 2-3 minutes to react; Ab. After the reaction is completed, an alkaline solution is quickly added and the reaction is continued for 6-7 hours until the solution color turns brown to obtain gold nanoclusters; The specific steps of step 2 are as follows: Ba. Add zinc nitrate dropwise to the gold nanoclusters in step 1 and stir for 2-3 minutes to obtain solution 1; Bb. Take polyethyleneimine and 2-methylimidazole and stir for 2-3 minutes to obtain solution 2; Bc. Solution 1 and solution 2 were mixed, incubated for 12-13 hours, washed three times with methanol, and dried in an oven at 40-45°C to obtain metal organic framework-coated gold nanoclusters; Bd. Metal organic framework-coated gold nanoclusters were dispersed in 0.01 mol· PBS preservation; The concentration of bovine serum albumin in step 1 is 50 mg·m , and the dosage is 15-18mL; The concentration of chloroauric acid in step 1 is 10 mmol. , the dosage of chloroauric acid is 10.0-10.3mL; The alkaline solution in step 1 is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 1 mol· , the dosage of sodium hydroxide solution is 1.0-1.5ml; In step 2, the amount of the gold nanoclusters is 2.5-2.8 ml, the amount of polyethyleneimine is 2.0-2.4 ml, the amount of 2-methylimidazole is 4.0-4.5 ml, and the amount of zinc nitrate is 4.0-4.4 ml, and the purity of the polyethyleneimine and 2-methylimidazole is analytical grade; Will , , , , , , , , , , , , alanine, cysteine, threonine, lysine, aspartic acid, glucose, sucrose, lactose, ascorbic acid or uric acid were added as interfering substances to the fluorescent nanocomposites at a concentration of 10 μM. and In the presence of interfering substances, the fluorescence intensity is quenched to the minimum, while in the presence of interfering substances, the fluorescence intensity does not change significantly. The results show that the metal organic framework-coated gold nanoclusters have an and The detection has good selectivity.

Images