Preparation method and application of gold nano-cluster fluorescence sensor

Abstract

The invention discloses a preparation method and application of a gold nano-cluster fluorescence sensor. The preparation method comprises the following steps: uniformly mixing an amino acid solution and a chloroauric acid solution, adjusting the pH value to 2-11 by using a sodium hydroxide solution or a hydrochloric acid solution, and stirring for 2-20 hours by using a stirrer at the temperature of 50-100 DEG C to obtain the gold nano-cluster fluorescence sensor. The amino acid solution is one or more of a cysteine solution, a tryptophan solution, an L-proline solution, an L-histidine solution, a D-histidine solution, an L-methionine solution and an L-phenylalanine solution; the molar ratio of the amino acid solution to the chloroauric acid solution is (2-20): 1. Amino acid is used as a protective agent and a reducing agent, and the ligand-protected gold nano-cluster fluorescence sensor is formed through interaction of lone pair electrons and empty orbits of gold, pi-pi accumulation and the like. Specific recognition is realized based on electronic structure differences of different metal ions. The gold nano-cluster fluorescence sensor shows a remarkable response characteristic to target heavy metal ions and has excellent detection sensitivity. The used raw materials are cheap and easy to obtain, the synthesis process is convenient for large-scale production, and the method is suitable for being popularized to practical application scenes such as environmental monitoring, food safety and water quality analysis.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial synthesis and rapid detection, and in particular to a preparation method of a gold nanocluster fluorescence sensor and application thereof. Background Art

[0002] The acceleration of industrialization has promoted the development of social productivity, but also aggravated environmental pollution. 2+ ), cadmium (Cd 2+ ), chromium (Cr 3+ / Cr 6+ ), mercury (Hg 2+ ), copper (Cu 2+ ), zinc (Zn 2+ ) and other heavy metal ions not only pollute the surrounding soil and aquatic ecosystems, but can also enter the human body through air, food, and drinking water. Because these heavy metal ions are bioaccumulative and toxic, they can accumulate in the human body for a long time, causing irreversible health damage such as organ damage and cancer. For example, Cr 6+ Due to its strong oxidizing property, it has high mobility in the environment and can invade the human body through the respiratory or digestive tract, inducing malignant tumors such as lung cancer and nasopharyngeal cancer. 2+ After entering the human body, it will accumulate in the kidneys and bones for a long time, leading to renal failure by inhibiting the renal tubular reabsorption function, and interfering with calcium homeostasis to induce osteoporosis and "itai-itai disease"; and Cu 2+ As essential trace elements, excessive exposure can trigger oxidative stress and increase the risk of neurodegenerative diseases, etc. Therefore, the development of highly sensitive detection technologies to achieve real-time monitoring of trace heavy metals is of great significance for environmental pollution prevention and control and public health security.

[0003] Currently, the main methods for detecting heavy metal ions include atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography (IC), graphite furnace atomic absorption spectrometry (GF-AAS), and atomic fluorescence spectrometry (AFS). Although these methods offer high accuracy, they suffer from limitations such as cumbersome and time-consuming sample pretreatment, expensive equipment, and the need for specialized personnel and large laboratories, making them difficult to meet the demands of rapid on-site detection and real-time monitoring.

[0004] To overcome the limitations of traditional detection methods, a variety of new rapid and portable detection technologies have emerged in recent years, including electrochemical sensing, microfluidic chip technology, Raman spectroscopy, and fluorescence sensing. These detection methods offer strong specificity, simplicity, and convenience, overcoming the technical bottleneck that hinders traditional methods from achieving on-site real-time monitoring. Gold nanoclusters (AuNCs), as a new type of fluorescent nanomaterial, have attracted considerable attention in recent years due to their advantages over conventional fluorescent materials, including ultra-small size, high quantum yield, ease of surface modification, excellent optoelectronic properties, green and non-toxic properties, and ease of operation. Although existing fluorescence sensors based on gold nanoclusters have shown good sensitivity and diversified strategies in the detection of heavy metal ions, they generally have the following defects: complex preparation process: many methods require multi-step synthesis, ligand modification or encapsulation (such as metal organic framework ZIF-8 embedding), which are cumbersome and time-consuming, making it difficult to achieve rapid preparation and application; harsh synthesis conditions or the use of toxic materials: some fluorescent probes use Cd-based quantum dots or require high temperature and strong reducing agents, which do not meet the development needs of green and low toxicity; insufficient detection selectivity and anti-interference: most methods are easily affected by Cu during the detection process. 2+ 、Hg 2+ 、Fe 3+ 、Ag + Due to the interference of non-target ions such as ions, additional masking agents need to be added to enhance selectivity, which increases the complexity of the system; long response time and limited detection limit: some probes require long incubation times or have low sensitivity to target ions, which limits their application in trace detection and rapid response fields; high cost: the use of expensive materials or complex devices increases the cost of the overall detection system, which is not conducive to promotion and large-scale application.

[0005] Therefore, there is an urgent need to develop a fluorescent probe material with a simple synthesis method, green and environmentally friendly, sensitive detection, strong selectivity and no dependence on masking agents, so as to achieve rapid and accurate detection of heavy metal ions. Summary of the Invention

[0006] In view of the defects in the prior art, the present invention provides a preparation method of a gold nanocluster fluorescence sensor and its application.

[0007] The present invention provides a method for preparing a gold nanocluster fluorescence sensor, comprising the following steps: The amino acid solution and the chloroauric acid solution are mixed evenly, and the pH is adjusted to 2-11 using a sodium hydroxide solution or a hydrochloric acid solution. The mixture is stirred at a temperature of 50-100° C. for 2-20 h using a stirrer to obtain the gold nanocluster fluorescent sensor; preferably, the pH is 2-10.

[0008] In the present invention, pH affects the performance of gold nanoclusters by regulating the ionization state of amino acid functional groups. For example, under acidic conditions (pH 2-6), the thiol group of cysteine ​​exists in a protonated form and has strong reducing properties, which can effectively reduce Au³⁺ to Au 0 , promoting the nucleation of gold nanoclusters; after protonation, the imidazole ring of histidine binds to Au³⁺ through coordination, synergistically promoting nucleation. Under weak alkaline conditions (pH 8~10), the thiol group is partially deprotonated to -S − , its reducibility is slightly reduced, but it is comparable to Au 3+ The enhanced coordination ability of L-methionine facilitates the growth of gold nanoclusters. After deprotonation, the imidazole ring coordinates with the gold nanocluster surface via the lone pair of electrons on the nitrogen atom, enhancing cluster stability. Within the pH range of 2–10, the indole ring of tryptophan and the benzene ring of L-phenylalanine maintain a conjugated structure, enhancing the stability of the gold nanoclusters through π-π stacking. L-methionine contains a thioether bond, which stabilizes the gold nanoclusters through coordination. The pyrrolidine ring of L-proline helps maintain the dispersion of the gold clusters through hydrophobic interactions. At high pH, ​​the thiol groups are completely deprotonated, disrupting the gold nanocluster structure and significantly reducing the fluorescence quantum yield.

[0009] In the present invention, amino acids have a weak ability to reduce HAuCl4 at room temperature, and the molecular movement rate can be increased by heating. The present invention controls the temperature within the range of 50-100°C, and the nucleation rate of gold atoms is fast and the number is large, which is conducive to the formation of small-sized and evenly distributed fluorescent clusters; when the temperature is below 50°C, the reaction efficiency is low and gold clusters are not easy to form; when the temperature is above 100°C, cluster agglomeration, crystal growth or fluorescence quenching is easily caused.

[0010] In the present invention, sufficient time is required to ensure that Au³⁺ is completely reduced to Au 0 , and fully combine with amino acids to form stable gold clusters. If the time is too short, the nanoclusters are not fully formed, the fluorescence intensity is low, and the reproducibility is poor. If the time is too long, it is easy to cause particle agglomeration and ligand desorption, affecting the fluorescence performance.

[0011] The amino acid solution is one or more of a cysteine ​​solution, a tryptophan solution, L-phenylalanine, an L-proline solution, an L-histidine solution, a D-histidine solution, and an L-methionine solution. The present invention selects specific amino acids and utilizes the reducing and coordination capabilities of -SH, the π-π stacking effect of the indole ring / benzene ring, the hydrophobic effect of the pyrrolidine ring, and the coordination effect of the imidazole ring / thioether bond to effectively regulate the size and fluorescence properties of the gold nanoclusters.

[0012] The molar ratio of the amino acid solution to the chloroauric acid solution is (2-20):1. By controlling the ratio of amino acids to chloroauric acid, the present invention achieves a balance between reduction efficiency, nucleation stability, and fluorescence intensity. If the ratio is too low, insufficient amino acids will fail to fully reduce Au³⁺ or stabilize the generated gold clusters, leading to aggregation or the formation of large gold particles, resulting in fluorescence quenching. If the ratio is too high, the excess amino acids will inhibit nucleation growth, increase solution viscosity, affect reaction-diffusion efficiency, and easily cause fluorescence self-quenching.

[0013] In some embodiments, the concentration of the sodium hydroxide solution is 0.1 to 1 mol L -1 ; or the concentration of the hydrochloric acid solution is 0.1~1 mol L -1 The concentration is less than 0.1 mol L -1 When the pH regulation is weak, it is difficult to drive the reaction quickly and effectively; when the pH is higher than 1 mol L -1 When the system is too alkaline or acidic, it may destroy the amino acid molecular structure, leading to uncontrolled reaction or instability of the gold cluster. The present invention adjusts the pH by optimizing the appropriate concentration of acid / base to control the reaction rate, maintain the stability of the amino acid structure and enhance the reducing ability in the appropriate range.

[0014] In some embodiments, the stirrer is a magnetic stirrer or a mechanical stirrer, and the stirring speed is 600 rpm to 1500 rpm.

[0015] In some embodiments, the concentration of the amino acid solution is 0.01 to 0.1 mol L -1 The concentration of the chloroauric acid solution is 0.01~0.1 mol L -1 .

[0016] The present invention also provides a gold nanocluster fluorescence sensor obtained by the preparation method.

[0017] The present invention also provides application of the gold nanocluster fluorescence sensor in heavy metal ion detection.

[0018] In some embodiments, the heavy metal ion is Cd 2+ , Pb 2+ 、Cu 2+ and Cr 6+ Any one or more of .

[0019] A method for detecting heavy metal ion concentration comprises the following steps: (1) mixing the gold nanocluster fluorescent sensor obtained by the preparation method with a standard sample of the substance to be tested, incubating at room temperature, and measuring the fluorescence intensity or the rate of change of fluorescence intensity; (2) Draw a standard curve of fluorescence intensity or fluorescence intensity change rate versus the concentration of the standard substance to be tested or its logarithmic value; (3) mixing the gold nanocluster fluorescent sensor obtained by the preparation method with a sample to be tested, incubating at room temperature, and measuring the fluorescence intensity or the rate of change of fluorescence intensity; (4) Substitute the fluorescence intensity obtained in step (3) into the standard curve described in step (2) to calculate the concentration of heavy metal ions in the sample.

[0020] In some embodiments, the heavy metal ion is Cd 2+ , Pb 2+ 、Cu 2+ and Cr 6+ Any one or more of .

[0021] In summary, compared with the prior art, the present invention achieves the following technical effects: 1. The present invention uses amino acids (cysteine, tryptophan, L-proline, L-histidine, D-histidine, L-methionine, L-phenylalanine) as protective agents and reducing agents. Its molecular structure contains functional groups such as thiol (-SH), indole ring, pyrrolidine ring, imidazole ring, sulfide bond, benzene ring, amino group (-NH2), and carboxyl group (-COOH). Through the interaction of lone pair electrons with the empty orbital of gold and π-π stacking, a ligand-protected gold nanocluster fluorescent sensor is formed. Based on Cd 2+ , Pb 2+ 、Cu 2+ and Cr 6+ The differences in electronic structures of different metal ions enable specific recognition.

[0022] 2. The present invention can realize the identification and quantification of specific heavy metal ions without adding additional metal masking agents, and has strong anti-interference ability; the gold nanocluster fluorescent probe shows significant response characteristics to the target heavy metal ions and has excellent detection sensitivity, among which Cd 2+ The detection limit was as low as 5 μg L -1 ; It can also achieve synchronous detection of Cd²⁺ and Pb²⁺.

[0023] 3. The present invention uses a one-step hydrothermal reaction to complete the preparation of gold nanocluster fluorescent sensors, without the need for multi-step modification or complex post-processing, greatly reducing the difficulty of operation and time cost; the reaction system is mild, using amino acids as reducing agents and protective agents, without the need for toxic and harmful organic solvents or heavy metal precursors, which is in line with the concept of green chemistry.

[0024] 4. The raw materials used in the present invention are cheap and easily available, and the synthesis process is easy to scale up, making it suitable for practical application scenarios such as environmental monitoring, food safety, and water quality analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is the effect of different pH on the fluorescence properties of L-cysteine-gold nanoclusters in Example 1 of the present invention; (a) is a photo under a fluorescent light; (b) is a photo under an ultraviolet light.

[0027] Figure 2 This is the effect of different molar ratios on the fluorescence properties of L-cysteine-gold nanoclusters in Example 1 of the present invention; (a) the molar ratio is 2:1; (b) the molar ratio is 1:1.

[0028] Figure 3 The L-Cys@AuNCs sensor solution obtained at different synthesis times in Example 1 of the present invention and its reaction with Cd at a concentration of 28 mg / L 2+ Fluorescence spectra of the solution after reaction; (a) reaction time is 12 h; (b) reaction time is 24 h.

[0029] Figure 4 These are photos of gold nanoclusters modified with different amino acids and an ultrapure water control sample under 365° UV light according to Example 12 of the present invention; (a) ultrapure water; (b) serine; (c) aspartic acid; (d) L-tryptophan.

[0030] Figure 5 a) The L-Cys@AuNCs sensor of Example 1 of the present invention responds to different concentrations of Cd 2+ The response of the fluorescence spectrum of the standard solution; b) the change rate of fluorescence intensity and Cd 2+ Linear relationship graph of concentration.

[0031] Figure 6 The fluorescence intensity of L-Cys@AuNCs and Cd 2+ Linear relationship graph of concentration.

[0032] Figure 7 The fluorescence intensity of L-Cys@AuNCs and Pb 2+ Linear relationship graph of concentration.

[0033] Figure 8 The fluorescence intensity change rate of L-Trp@AuNCs in Example 12 of the present invention is related to the Cu 2+ Linear plot of the logarithmic concentrations.

[0034] Figure 9 The fluorescence intensity change rate of L-Trp@AuNCs in Example 12 of the present invention and Cr 6+ Linear plot of the logarithmic concentrations.

[0035] Figure 10 TEM images of Example 1 of the present invention; Figures a) and b) are TEM images of the gold nanocluster fluorescent probe; Figures c) and d) are TEM images of the gold nanocluster fluorescent probe and Cd 2+ TEM image after action.

[0036] Figure 11 FTIR spectra of L-Cys (a) and L-Cys@AuNCs (b) of Example 1.

[0037] Figure 12 This is the UV-visible absorption spectrum of L-Cys@AuNCs in Example 11 of the present invention.

[0038] Figure 13 L-Trp@AuNCs (a) and Cu 2+ (b) Cr 6+ (c) Hydration particle size distribution after treatment. DETAILED DESCRIPTION

[0039] To help those skilled in the art better understand the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

[0040] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. The materials and reagents used are all commercially available unless otherwise specified.

[0041] Example 1 The preparation method of the L-cysteine-gold nanocluster probe (L-Cys@AuNCs) in this preparation example is as follows: S1: L-cysteine ​​(concentration 0.01 mol L -1 ) and chloroauric acid (HAuCl4·3H2O, concentration 0.01 mol L -1 ) are sequentially added into the reaction container and mixed thoroughly to obtain a mixed solution; S2: adding a NaOH solution dropwise to the mixed solution in step S1 to adjust the pH of the mixed solution to 10 to obtain a mixed solution; S3: placing the mixed solution obtained in step S2 in an oil bath for heating reaction at a reaction temperature of 50° C. and magnetic stirring for 12 h to obtain a gold nanocluster fluorescent probe; S4: The gold nanocluster fluorescent probe obtained in S3 was stored at 4°C for use.

[0042] Example 2 The difference from Example 1 is that in S2, HCl solution is added dropwise to adjust the pH of the mixed solution to 2.

[0043] Example 3 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 3.

[0044] Example 4 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 4.

[0045] Example 5 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 5.

[0046] Example 6 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 6.

[0047] Example 7 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 7.

[0048] Example 8 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 8.

[0049] Example 9 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 9.

[0050] Example 10 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 11.

[0051] Example 11 The preparation method of the L-cysteine-gold nanocluster probe (L-Cys@AuNCs) in this preparation example is as follows: S1: L-cysteine ​​(concentration 0.1 mol L -1 ) and chloroauric acid (concentration of 0.1 molL -1) are sequentially added into the reaction container and mixed thoroughly to obtain a mixed solution; S2: adding a NaOH solution dropwise to the mixed solution in step S1 to adjust the pH of the mixed solution to 8 to obtain a mixed solution; S3: placing the mixed solution obtained in step S2 in an oil bath for heating reaction at a reaction temperature of 100° C. and magnetic stirring for 18 h to obtain a gold nanocluster fluorescent probe; S4: The gold nanocluster fluorescent probe obtained in S3 was stored at 4°C for use.

[0052] Example 12 The preparation method of the L-tryptophan-gold nanocluster fluorescent probe (L-Trp@AuNCs) in this preparation example is as follows: S1: L-tryptophan (concentration 0.01 mol L -1 ) and chloroauric acid (concentration 0.01 mol L -1 ) were added into the reaction container and mixed thoroughly to obtain a mixed solution; S2: adding HCl solution dropwise to the mixed solution in step S1 to adjust the pH of the mixed solution to 2 to obtain an acidic mixed solution; S3: placing the acidic mixed solution obtained in step S2 in an oil bath for heating reaction at a reaction temperature of 100° C. and magnetic stirring for 2 h to obtain a gold nanocluster fluorescent probe; S4: The gold nanocluster fluorescent probe obtained in S3 was stored at 4°C for use.

[0053] Comparative Example 1 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 12.

[0054] Comparative Example 2 The difference from Example 1 is that in S2, the pH of the mixed solution is adjusted to 13.

[0055] Comparative Example 3 The difference from Example 1 is that in S1, the molar ratio is 1:1.

[0056] Comparative Example 4 The difference from Example 1 is that in S3, the reaction was carried out under magnetic stirring for 24 h.

[0057] Comparative Example 5 The difference from Example 12 is that in S1, the amino acid is serine.

[0058] Comparative Example 6 The difference from Example 12 is that in S1, the amino acid is aspartic acid.

[0059] Performance Testing Test Example 1 Effect of different pH values ​​on the fluorescence properties of gold nanoclusters By detecting the fluorescence properties of L-Cys@AuNCs prepared in Examples 1 to 10 and Comparative Examples 1 to 2, the effects of different pH values ​​on their fluorescence properties were observed.

[0060] The results are as follows Figure 1 As shown in the figure, in the pH range of 2~11, the solution can be seen to fluoresce under 365 nm ultraviolet light; when the pH is ≥12, the fluorescence property disappears.

[0061] Test Example 2 Effects of Different Molar Ratios on the Fluorescence Properties of Gold Nanoclusters By detecting the fluorescence properties of L-Cys@AuNCs prepared in Example 1 and Comparative Example 3, the effects of different molar ratios on their fluorescence properties were observed.

[0062] The results are as follows Figure 2 As shown, when the molar ratio is 2:1 ( Figure 2 a), the solution is light yellow under visible light and fluorescence is visible under 365nm ultraviolet light; when the molar ratio is 1:1 ( Figure 2 b) The color is light yellow under visible light and there is no fluorescence under 365 nm ultraviolet light, indicating that the generation of fluorescence depends on the molar ratio between the amino acid solution and the chloroauric acid solution. Only when the two are enriched in a certain specific ratio can a complex with fluorescent properties be formed.

[0063] Test Example 3 Effect of Different Synthesis Times on the Fluorescence Properties of Gold Nanoclusters By detecting the fluorescence properties of L-Cys@AuNCs prepared in Example 1 and Comparative Example 4, the effects of different synthesis times on their fluorescence properties were observed.

[0064] The results are as follows Figure 3 As shown, the same concentration of Cd 2+ The fluorescence enhancements of the probe synthesized at 12 h (a) and 24 h (b) were approximately 44% and 7%, respectively.

[0065] Test Example 4 Effects of Different Amino Acids on the Fluorescence Properties of Gold Nanoclusters By detecting the fluorescence properties of the serine- and aspartic acid-modified gold nanoclusters prepared in Example 12 and Comparative Examples 5-6, the effects of different amino acids on the luminescence properties were observed.

[0066] The results are as follows Figure 4 As shown, under 365 nm ultraviolet light, ultrapure water ( Figure 4 a) As a blank control, serine ( Figure 4 b) and aspartic acid ( Figure 4c) The modified gold nanoclusters showed no fluorescence. Figure 4 The L-tryptophan of d is fluorescent. This phenomenon indicates that the functional groups (carboxyl and hydroxyl) of serine and aspartic acid are only weakly reducing and cannot reduce Au under this experimental condition. 3+ Reduced to Au 0 , it is difficult to achieve the nucleation and growth of gold nanoclusters, resulting in no fluorescence.

[0067] Test Example 5 Cd 2+ Concentration detection The gold nanocluster fluorescent probe prepared in Example 1 was used to 2+ The specific steps for concentration detection are as follows: S1: Configure CD 2+ The concentrations were 0, 5, 25, 100, 200, 250, 300, 400, 1000, 2500, 3000, 5000, and 10000 μg L -1 Standard solution of S2: The standard solution in step S1 was mixed with 100 μL of gold nanocluster fluorescent probe and incubated at room temperature for 1 min to obtain a mixed solution; S3: Measure the fluorescence intensity of the mixed solution in step S2, use 380 nm as the excitation wavelength, and measure the fluorescence emission spectrum in the range of 500-700 nm; then use Cd 2+ The concentration is the horizontal axis and the fluorescence intensity at 646 nm is the vertical axis to draw a standard curve.

[0068] The results are as follows Figure 5 As shown, Cd 2+ Concentration ranged from 0 to 5000 μg L -1 Within this range, the fluorescence enhancement efficiency is directly proportional to the ion concentration, and the linear equations are y=29.741x+227450.198, R 2 =0.995; good linearity, detection limit of 5 μg L -1 ; S4: Add the Cd 2+ The sample to be tested is mixed with the gold nanocluster fluorescent probe, and its fluorescence intensity is measured. The Cd of the sample to be tested can be calculated by substituting it into the standard curve obtained in step S3. 2+ concentration.

[0069] Test Example 6 Cd 2+ and Pb 2+ Simultaneous detection of concentration The gold nanocluster fluorescent probe prepared in Example 11 was used to 2+ and Pb 2+ The specific steps for simultaneous detection of concentration are as follows: S1: Configure CD 2+ Standard solutions with concentrations of 0, 0.5, 2.5, 10, 17.5, 25, 50, 100, 150, and 200 μM; S2: Configure Pb 2+ Standard solutions with concentrations of 0, 0.5, 2.5, 10, 50, 100, 150, 200, and 250 μM; S3: The standard solution in step S1 was mixed with 100 μL of gold nanocluster fluorescent probe and incubated at room temperature for 1 min to obtain a mixed solution; S4: Measure the fluorescence intensity of the mixed solution in step S3, use 365 nm as the excitation wavelength, measure the fluorescence emission spectrum in the range of 400-700 nm, and plot the fluorescence intensity at 587 nm against the Cd 2+ concentration standard curve.

[0070] The results are as follows Figure 6 As shown, Cd 2+ In the concentration range of 0~200 μM, the fluorescence intensity is directly proportional to the ion concentration, and the linear equation is y=57.69911x+17.40597 (R 2 =0.999); S5: The standard solution in step S2 was mixed with 100 μL of the gold nanocluster fluorescent probe, and incubated at room temperature for 1 min to obtain a mixed solution; S6: Measure the fluorescence intensity of the mixed solution in step S4, use 365 nm as the excitation wavelength, measure the fluorescence emission spectrum in the range of 400-700 nm, and plot the fluorescence intensity at 416 nm against the Pb 2+ concentration standard curve.

[0071] The results are as follows Figure 7 As shown, Pb 2+ In the concentration range of 0~250 μM, the fluorescence intensity is directly proportional to the ion concentration, and the linear equation is y=−2.59968x+851.95222 (R 2 =0.987); S7: Add the unknown concentration of Cd 2+ / Pb 2+ The sample to be tested is mixed with the gold nanocluster fluorescent probe, and its fluorescence intensity at 587 nm / 416 nm is measured. The Cd of the sample to be tested can be calculated by substituting it into the standard curve obtained in step S4 / S6. 2+ / Pb 2+ concentration.

[0072] Test Example 7 Cu 2+ Concentration detection The gold nanocluster fluorescent probe prepared in Example 12 was used to 2+ The specific steps for concentration detection are as follows: S1: Configure Cu 2+ Standard solutions with concentrations of 5, 10, 50, 100, 200, 300, 400, and 500 μM; S2: The standard solution in step S1 was mixed with 100 μL of gold nanocluster fluorescent probe and incubated at room temperature for 1 min to obtain a mixed solution; S3: Measure the fluorescence intensity of the mixed solution in step S2, use 370 nm as the excitation wavelength, measure the fluorescence emission spectrum in the range of 400-600 nm, and plot the fluorescence intensity at 470 nm against Cu 2+ concentration standard curve.

[0073] The results are as follows Figure 8 As shown, Cu 2+ In the concentration range of 5~500 μM, the fluorescence quenching efficiency is directly proportional to the logarithm of the ion concentration, and the linear equation is y=0.13513logx+0.05798 (R 2 =0.996).

[0074] S4: Add the unknown concentration of Cu 2+ The sample to be tested is mixed with the gold nanocluster fluorescent probe, and its fluorescence intensity is measured. The Cu ions of the sample to be tested can be calculated by substituting the fluorescence intensity into the standard curve obtained in step S3. 2+ concentration.

[0075] Test Case 8 Cr 6+ Concentration detection S1: Configure Cr 6+ Standard solutions with concentrations of 30, 40, 50, 100, 200, 300, 400, and 500 μM; S2: The standard solution in step S1 was mixed with 100 μL of gold nanocluster fluorescent probe and incubated at room temperature for 1 min to obtain a mixed solution; S3: Measure the fluorescence intensity of the mixed solution in step S2, use 370 nm as the excitation wavelength, measure the fluorescence emission spectrum in the range of 400-600 nm, and plot the fluorescence intensity at 470 nm against Cr 6+ concentration standard curve.

[0076] The results are as follows Figure 9 As shown, Cr 6+ In the concentration range of 30~500 μM, the fluorescence intensity is directly proportional to the logarithm of the ion concentration, and the linear equation is y=0.3405logx−0.43481 (R 2 =0.993); S4: The Cr 6+ The sample to be tested is mixed with the gold nanocluster fluorescent probe, and its fluorescence intensity is measured. The Cr of the sample to be tested can be calculated by substituting it into the standard curve obtained in step S3. 6+ concentration.

[0077] Test Example 9 Characterization of Gold Nanocluster Fluorescent Probe The gold nanocluster fluorescent probe prepared in Example 1 was characterized. Figures 10-11 shown.

[0078] Figure 10 Figures a) and b) are TEM images of the gold nanocluster fluorescent probe. As can be seen, the fluorescent probe is a spherical nanoparticle with an average particle size of approximately 7 nm and a well-aligned lattice spacing of 2.37 Å. Figure 10 c)~d) are the probe and Cd 2+ TEM image after the action. As can be seen from the figure, the probe and Cd 2+ The average particle size after the reaction was about 100 nm, indicating that the addition of Cd 2+ The subsequent fluorescence enhancement is caused by aggregation.

[0079] Figure 11 The infrared spectra of L-Cys@AuNCs are shown in Figure 2. By comparing L-Cys (a) and L-Cys@AuNCs (b), it is found that L-Cys has a high IR value at 2551 cm -1 The stretching vibration peak of the thiol group (-SH) appears at the IR spectrum of L-Cys@AuNCs, while this characteristic absorption peak disappears in the IR spectrum of L-Cys@AuNCs. This phenomenon indicates that the thiol group in the L-Cys molecule interacts with the gold nanoclusters, and this interaction leads to the cleavage of the S−H bond.

[0080] The gold nanocluster fluorescent probe prepared in Example 11 was characterized. Figure 12 shown.

[0081] Figure 12 The UV-visible absorption spectrum of L-Cys@AuNCs. When no heavy metal ions were added to the L-Cys@AuNCs probe, there was an obvious characteristic absorption peak at about 300 nm. 2+ and Cd 2+ After addition, the absorption peak intensity increased and a red shift occurred, indicating that heavy metal ions coordinated with the thiol groups on the surface of L-Cys@AuNCs. This interaction may form coordination bonds between S atoms and metal ions, changing the electronic structure or surface charge distribution of AuNCs, thereby causing the absorption peak shift.

[0082] The gold nanocluster fluorescent probe prepared in Example 12 was characterized. Figure 13 shown.

[0083] Figure 13 a is the dynamic light scattering spectrum of L-Trp@AuNCs. As can be seen from the figure, the average hydrated particle size of the probe is 12.9 nm, and the particle size distribution is mainly concentrated in the range of 10~16 nm; 2+ After the effect ( Figure 13 b), the average hydrated particle size increased to 33.4 nm, and the particle size distribution range widened to 20~70 nm; 6+ After the effect ( Figure 13 c), the average hydrated particle size increased to 48.9 nm, and the particle size distribution range widened to 30~70 nm, indicating that the addition of Cu 2+ Cr 6+ The subsequent fluorescence quenching is caused by aggregation.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a gold nanocluster fluorescence sensor, characterized in that: The steps include: The amino acid solution and the chloroauric acid solution are uniformly mixed, the pH value is adjusted to 2-11 using a sodium hydroxide solution or a hydrochloric acid solution, and the mixture is stirred at a temperature of 50-100° C. for 2-20 h using a stirrer to obtain the gold nanocluster fluorescent sensor; The amino acid solution is one or more of cysteine ​​solution, tryptophan solution, L-proline solution, L-histidine solution, D-histidine solution, L-methionine and L-phenylalanine; The molar ratio of the amino acid solution to the chloroauric acid solution is (2-20):

1.

2. The preparation method according to claim 1, characterized in that The concentration of the sodium hydroxide solution is 0.1~1 mol L -1 ; Or the concentration of the hydrochloric acid solution is 0.1~1 mol L -1 .

3. The preparation method according to claim 1, characterized in that The stirrer is a magnetic stirrer or a mechanical stirrer, and the stirring speed is 600 rpm to 1500 rpm.

4. The preparation method according to claim 1, characterized in that The concentration of the amino acid solution is 0.01~0.1 mol L -1 The concentration of the chloroauric acid solution is 0.01~0.1 mol L -1 .

5. The gold nanocluster fluorescent sensor obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the gold nanocluster fluorescence sensor according to claim 5 in the detection of heavy metal ions.

7. The use according to claim 6, characterized in that The heavy metal ion is Cd 2+ , Pb 2+ 、Cu 2+ and Cr 6+ Any one or more of .

8. A method for detecting heavy metal ion concentration, characterized in that: The steps include: (1) Mixing the gold nanocluster fluorescent sensor obtained by the preparation method according to any one of claims 1 to 4 with a standard sample of the analyte, incubating at room temperature, and measuring the fluorescence intensity or the rate of change of fluorescence intensity; (2) Draw a standard curve of fluorescence intensity or fluorescence intensity change rate versus the concentration of the standard substance to be tested or its logarithm; (3) mixing the gold nanocluster fluorescent sensor obtained by the preparation method according to any one of claims 1 to 4 with a sample to be tested, incubating at room temperature, and measuring the fluorescence intensity or the rate of change of fluorescence intensity; (4) Substitute the fluorescence intensity or fluorescence intensity change rate obtained in step (3) into the standard curve described in step (2) to calculate the concentration of heavy metal ions in the sample.

9. The method according to claim 8, characterized in that The heavy metal ion is Cd 2+ , Pb 2+ 、Cu 2+ and Cr 6+ Any one or more of .

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