Gold nanocluster as well as preparation method and application thereof

Abstract

The invention discloses a gold nanocluster and a preparation method and application thereof, and belongs to the technical field of metal cluster materials, and the preparation method comprises the following steps: preparing BSA-AuNCs by taking bovine serum albumin as a template and ascorbic acid as a reducing agent through a chemical reduction method; the invention further discloses the gold nanocluster and application of the gold nanocluster in hexavalent chromium fluorescence detection. The method is used for fluorescence and visual detection of hexavalent chromium, is simple and efficient in operation, has high sensitivity and selectivity, and can accurately detect low-concentration hexavalent chromium. And the method has strong anti-interference capability and wide application prospects in the fields of biosensing, medical diagnosis, environmental monitoring and the like, and particularly provides a reliable and effective method for on-site rapid detection of hexavalent chromium.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal cluster materials, and particularly relates to a gold nanocluster and a preparation method and application thereof. BACKGROUND

[0002] Chromium is a heavy metal, which exists in various oxidation states, and Cr(III) and Cr(VI) are the main forms of chromium in nature. In industrial production, Cr(VI) is mainly used in pigments, textiles, electroplating, leather making, and also used in the manufacture of catalysts. Large-scale industrial exploitation and production increase the discharge of Cr(VI)-containing wastewater, which causes great harm to the environment and human health. Therefore, the detection of Cr(VI) is very important. At present, the methods for detecting Cr(VI) mainly include cyclic voltammetry, colorimetry, fluorescence method, and inductively coupled method. Among them, the fluorescence analysis method for detecting Cr(VI) has the advantages of low cost, rapid analysis, and simple operation.

[0003] As a new type of nanomaterial, noble metal nanoclusters have attracted much attention since they were discovered. They have good light stability, long fluorescence lifetime, and large Stokes shift, which makes them widely used in biological sensing, environmental detection, cell imaging, and disease detection. Among these noble metal nanoclusters, gold nanoclusters (AuNCs) have been more widely studied due to their high luminescence intensity, high stability, and biocompatibility. At present, in order to improve the stability of AuNCs, small thiol molecules, polymers, DNA, and proteins are used as templates for the synthesis of AuNCs. Among them, AuNCs prepared by using proteins such as bovine serum albumin (BSA), egg protein, and human transferrin as templates are widely used due to their mild synthesis conditions and environmental friendliness. Different preparation methods can obtain AuNCs with different physicochemical properties, which can be widely used in different fields. However, the AuNCs prepared by the existing technology have not been directly used for the detection of Cr(VI).

[0004] Therefore, how to provide AuNCs capable of accurately detecting Cr(VI) is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0005] To solve the above technical problems, the application provides a gold nanocluster and a preparation method and application thereof.

[0006] To achieve the above purpose, the application provides the following technical solutions.

[0007] A preparation method of gold nanoclusters, which uses bovine serum albumin as a template and ascorbic acid as a reducing agent to prepare gold nanoclusters BSA-AuNCs by chemical reduction.

[0008] Preferably, the method comprises the following steps:

[0009] After mixing the bovine serum albumin solution and the chloroauric acid solution, the ascorbic acid solution is added, the pH is adjusted, and the reaction is continuously stirred, and the solution of the gold nanoclusters is obtained after the reaction is completed.

[0010] Beneficial effects: Ascorbic acid in the system can reduce gold ions to gold atoms, and bovine serum albumin (BSA) can prevent the generated gold atom clusters from aggregating by using its special structure, such as steric hindrance stabilization effect, electrostatic stabilization effect, coordination stabilization effect, and dynamic barrier effect, so as to maintain the stability of the nanoclusters.

[0011] Preferably, the concentration of the bovine serum albumin solution is 20.0 mg / mL; and / or,

[0012] The concentration of the chloroauric acid solution is 10.0 mmol / L; and / or,

[0013] The concentration of the ascorbic acid solution is 0.35 mg / mL.

[0014] Preferably, the volume ratio of the bovine serum albumin solution, the chloroauric acid solution, and the ascorbic acid solution is 5:5:0.08.

[0015] Preferably, the pH is adjusted to 12.

[0016] Preferably, the temperature of the stirring reaction is 37℃, and the time is 12h.

[0017] A gold nanocluster prepared by the preparation method.

[0018] The application of a gold nanocluster as described above in the fluorescence detection of hexavalent chromium.

[0019] Preferably, the application is the use of test paper detection, which specifically includes the following steps:

[0020] The qualitative filter paper is soaked in the solution of the BSA-AuNCs, and after the soaking is completed, the BSA-AuNCs test paper is obtained by air drying, and the hexavalent chromium solution is drop-coated on the BSA-AuNCs test paper, so that the visual fluorescence detection of hexavalent chromium can be realized.

[0021] Beneficial effects: The BSA-AuNCs test paper is prepared by soaking method in the present application, so that the intuitive, rapid, and visual detection of Cr(VI) can be realized. All experimental results show that the BSA-AuNCs can be used as an effective probe to detect Cr(VI) in water samples.

[0022] Preferably, the pH of the hexavalent chromium solution is 6; and / or, the detection time after the addition of the hexavalent chromium solution in the solution is 1-20min.

[0023] Preferably, the content of hexavalent chromium is detected in a solution, specifically comprising the following steps:

[0024] After diluting the gold nanoclusters, the fluorescence value F1 is measured in a buffer solution; then the fluorescence value F2 is measured after adding a hexavalent chromium solution; and the content of Cr(VI) is detected according to the quantitative relationship between the fluorescence quenching value ΔF and the concentration of Cr(VI) added in the system.

[0025] Wherein, the ΔF=F1-F2.

[0026] More preferably, specifically comprising the following steps:

[0027] The BSA-AuNCs are diluted 10 times with ultrapure water, 1.00 mL of the BSA-AuNCs diluent is added to 1.50 mL of a pH 6.0 citric acid-sodium citrate buffer solution, and the fluorescence value F1 is measured on a fluorescence spectrophotometer; then the fluorescence value F2 is measured after adding a Cr(VI) solution; and finally the content of Cr(VI) is detected according to the quantitative relationship between the fluorescence quenching value ΔF (ΔF=F1-F2) and the concentration of Cr(VI) added in the system.

[0028] Compared with the prior art, the present application has the following advantages and technical effects:

[0029] The gold nanoclusters prepared by using bovine serum albumin as a template and ascorbic acid as a reducing agent have uniform particle size, good biocompatibility and stability, and excellent fluorescence performance. The test paper prepared by the present application is used for fluorescence and visual detection of hexavalent chromium, and has the advantages of simple operation, high efficiency, high sensitivity and selectivity, and can accurately detect low-concentration hexavalent chromium. The test paper has strong anti-interference ability, and has wide application prospects in the fields of biosensing, medical diagnosis and environmental monitoring, and especially provides a reliable and effective method for on-site rapid detection of hexavalent chromium. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which form a part of the present application, are used to provide a further understanding of the present application, and the illustrative embodiments thereof and their descriptions serve to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0031] Figure 1 TEM images (a) of BSA-AuNCs obtained in Example 1, fluorescence spectrum and ultraviolet-visible spectrum (b), TEM images (d) of BSA-AuNCs obtained in Comparative Example 1, and TEM images (e) of BSA-AuNCs obtained in Comparative Example 2;

[0032] Wherein, the insert in a is a particle size distribution graph (c); and the insert in b is an optical photograph of BSA-AuNCs under visible light and ultraviolet light.

[0033] Figure 2 Fluorescence spectra of BSA-AuNCs before (1) and after (2) adding Cr(VI) in Example 1; the inset is the photo of BSA-AuNCs under UV light before (right) and after (left) adding Cr(VI);

[0034] Figure 3 UV-Vis absorption spectra of BSA-AuNCs in Example 1;

[0035] Wherein, a is BSA-AuNCs in Example 1; b is BSA-AuNCs+Cr(VI); c is Cr(VI) (1.00×10 - 4 mol / L); d is BSA;

[0036] Figure 4 Fluorescence decay curves of BSA-AuNCs solution before and after adding Cr(VI) solution;

[0037] Wherein, a is before adding Cr(VI), i.e. cCr(VI)=0.00 mol / L; b is after adding Cr(VI), i.e. cCr(VI)=1.00×10 -4 mol / L;

[0038] Figure 5 Mechanism diagram of BSA-AuNCs for detecting Cr(VI) in Example 1;

[0039] Figure 6 TEM image of BSA-AuNCs+Cr(VI) in Example 1;

[0040] Figure 7 Influence of pH on the response sensitivity of BSA-AuNCs to Cr(VI);

[0041] Figure 8 Influence of buffer solution type on the response sensitivity of BSA-AuNCs to Cr(VI);

[0042] Figure 9 Selectivity of BSA-AuNCs to Cr(VI) (Cr(VI)=1.00×10 -6 mol / L);

[0043] Figure 10 Influence of reaction time on the fluorescence intensity of the system;

[0044] Figure 11 Influence of determination temperature on the response of BSA-AuNCs to Cr(VI);

[0045] Figure 12 Fluorescence spectra and linear relationship of BSA-AuNCs with different concentrations of Cr(VI);

[0046] Wherein, a is the response spectrum curve; b is the piecewise linear curve; c is the linear curve in high concentration region; d is the linear curve in low concentration region;

[0047] Figure 13 Visual detection of Cr(VI) based on BSA-AuNCs test paper obtained in Example 1;

[0048] Figure 14 Blank control of filter paper and Cr(VI);

[0049] Figure 15 Effect of reaction time on detection of Cr(VI) by BSA-AuNCs test paper;

[0050] Figure 16 Selectivity of BSA-AuNCs test paper for detection of Cr(VI). DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0052] In order to make the above objectives, characteristics and advantages of the present application more apparent and understandable, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0053] Unless otherwise specified, the raw materials in the embodiments of the present application are obtained by commercial purchase;

[0054] Among them, chloroauric acid trihydrate (HAuCl4·3H2O, 99.0 %, National Pharmaceutical Chemical Reagent Co., Ltd.);

[0055] Freeze-dried bovine serum albumin (BSA, 97 %, Beijing Aoboxing Biotechnology Co., Ltd.);

[0056] L-ascorbic acid (L-AA, Jindong Tianzheng Fine Chemical Reagent Factory);

[0057] The basic reagents (analytical reagent grade) such as disodium hydrogen phosphate-potassium hydrogen phosphate (pH = 6), citric acid-sodium citrate (pH = 6), BR buffer solution (pH = 6), sodium hydroxide (NaOH), potassium dichromate (K2Cr2O7), disodium ethylenediaminetetraacetate (EDTA-2Na) were purchased from Titan Scientific Co., Ltd. (Shanghai, China).

[0058] Unless otherwise specified, the room temperature or normal temperature in the embodiments of the present application refers to 25 ± 3℃.

[0059] Example 1

[0060] A preparation method of gold nanoclusters, comprising the following steps:

[0061] 5.00 mL of BSA (20.0 mg / mL) and 5.00 mL of HAuCl4·3H2O (10.0 mM) aqueous solution were mixed at 37℃ under vigorous stirring, 80 μL of L-AA (0.35 mg / mL) was added after stirring for 2 min, and the stirring was continued, 5 min later, the pH of the solution was adjusted to about 12 by 1.00 mol / L NaOH, and then the stirring was continued at 37℃ for 12 h, thereby obtaining a gold nanocluster solution, which was recorded as BSA-AuNCs. The obtained BSA-AuNCs were stored at 4℃ for standby.

[0062] Comparative Example 1

[0063] The difference from Example 1 is only that L-AA is not added. The remaining process steps and parameters are the same as those of Example 1.

[0064] Comparative Example 2

[0065] The difference from Example 1 is only that the reducing agent L-AA is replaced by an equal volume and concentration of sodium borohydride.

[0066] Application Example 1

[0067] The application of gold nanoclusters in detecting Cr(VI) in water, comprising the following steps:

[0068] The BSA-AuNCs were diluted 10 times with ultrapure water, 1.00 mL of the diluted solution was mixed with 1.50 mL of citric acid-sodium citrate buffer solution with pH of 6. The fluorescence value F1 (λ ex =360 nm, slit width 5 nm) was measured on a fluorescence spectrophotometer, then 50 μL of Cr(VI) standard solution or sample with different concentrations was added, the fluorescence value F2 was measured, and the content of Cr(VI) was detected according to the quantitative relationship between the fluorescence quenching value ΔF (ΔF = F1-F2) and the concentration of Cr(VI) added into the system.

[0069] Application Example 2-10

[0070] Application of gold nanoclusters in visual detection of Cr(VI) in water, comprising the following steps:

[0071] (1) Cut qualitative filter paper into 2x4 cm filter paper pieces, immerse the filter paper pieces in the BSA-AuNCs solution obtained in Example 1 for 3 min, adsorb BSA-AuNCs onto the filter paper through hydrophilic interaction and hydrogen bonding, take out and dry in the dark, to obtain BSA-AuNCs test paper.

[0072] (2) Prepare Cr(VI) solutions with concentrations of 1.00x10 -2 mol / L (Application Example 2), 1.00x10 -3 mol / L (Application Example 3), 1.00x10 -4 mol / L (Application Example 4), 1.00x10 -5 mol / L (Application Example 5), 1.00x10 -6 mol / L (Application Example 6), 1.00x10 -7 mol / L (Application Example 7), 1.00x10 -8 mol / L (Application Example 8), 1.00x10 -9 mol / L (Application Example 9), and 1.00x10 -10 mol / L (Application Example 10), respectively, and spray them on the obtained BSA-AuNCs test paper, and observe the color of the test paper under ultraviolet light after natural air drying, to realize colorimetric detection of Cr(VI).

[0073] Comparative Application Example 1

[0074] The difference between Application Examples 2-10 and Comparative Application Example 1 is only that the BSA-AuNCs test paper is replaced by qualitative filter paper, and the specific steps include:

[0075] Cut qualitative filter paper into 2x4 cm filter paper pieces, and prepare Cr(VI) solutions with concentrations of 1.00x10 -2 mol / L (Comparative Application Example 1), 1.00x10 -3 mol / L (Comparative Application Example 2), 1.00x10 -4 mol / L (Comparative Application Example 3), 1.00x10 -5 mol / L (Comparative Application Example 4), 1.00x10 -6 mol / L (Comparative Application Example 5), 1.00x10 -7 mol / L (Comparative Application Example 6), 1.00x10 -8 mol / L (Comparative Application Example 7), 1.00x10-9 mol / L (comparative application example 8), 1.00 x 10 -10 mol / L (comparative application example 9) and distilled water (comparative application example 10) were sprayed on the obtained filter paper, and after natural air drying, the color of the test paper was observed under ultraviolet lamp.

[0076] Technical effects:

[0077] 1. Performance characterization

[0078] The BSA-AuNCs obtained in Example 1 and Comparative Examples 1-2 were characterized by transmission electron microscopy (TEM), fluorescence spectrum and ultraviolet-visible absorption spectrum, and the results are shown in Figure 1 .

[0079] Figure 1 As shown in part a of the figure, the BSA-AuNCs have uniform particle size, uniform dispersion and no agglomeration phenomenon, and the particle size analysis results show that the average size is about 1.5 nm. Figure 1 In part b of the figure, curve 1 is the ultraviolet-visible absorption spectrum of the diluted BSA-AuNCs aqueous solution, and from the figure it can be seen that the BSA-AuNCs have no obvious absorption in the ultraviolet-visible region; Figure 1 Curves 2 and 3 in part b of the figure are fluorescence spectrum graphs of the BSA-AuNCs solution diluted by 20 times, wherein from curve 2 it can be seen that the maximum excitation wavelength of the BSA-AuNCs is 360 nm, and from curve 3 it can be seen that the maximum emission wavelength of the BSA-AuNCs is 610 nm. Figure 1 The insets in part b of the figure are photographs of the BSA-AuNCs under natural light (left) and ultraviolet lamp (right), respectively, wherein the BSA-AuNCs appear brownish yellow under natural light and emit strong red fluorescence under 365 nm ultraviolet lamp irradiation. In addition, by comparing part a and parts d-e, it can be seen that the gold nanoclusters synthesized without L-AA in Comparative Example 1 have larger particle size, and there are fewer gold nanocluster particles in the TEM field after the same dilution, indicating that the concentration of the synthesized gold nanoclusters is smaller. The gold nanoclusters synthesized by replacing L-AA with sodium borohydride in Comparative Example 2 are in an obvious aggregated state, and the solution has no fluorescence, indicating that fluorescent gold nanoclusters are not synthesized.

[0080] 2. Mechanism research

[0081] 2.1 Fluorescence spectrum test

[0082] It was found that Cr(VI) can quench the fluorescence of BSA-AuNCs. The fluorescence spectrum test results of Example 1 before and after the addition of Cr(VI) are shown in Figure 2 . Figure 2The inset figure is the photo of BSA-AuNCs under UV light before (right) and after (left) adding Cr(VI). It can be obviously seen from the inset figure that the red fluorescence of BSA-AuNCs is obviously weakened after adding Cr(VI). Comparing curve 1 and curve 2, the fluorescence intensity value of BSA-AuNCs is obviously reduced after adding Cr(VI). In order to verify the quenching mechanism, the BSA-AuNCs before and after adding Cr(VI) and the Cr(VI) and BSA solutions are scanned by ultraviolet-visible absorption spectrum, and the results are shown in Figure 3 Fig. 2, wherein curve a shows that the absorption spectrum of BSA-AuNCs obtained in Example 1 shows strong absorption in the short wave region, but no obvious peak shape, indicating that the size is less than 2 nm; curve b is the absorption spectrum of BSA-AuNCs after adding Cr(VI). Comparing curves a and b, it can be seen that a new strong absorption peak appears at 360 nm in the absorption spectrum of BSA-AuNCs after adding Cr(VI), which overlaps with the absorption peak of Cr(VI) at 360 nm in curve c, indicating that there is fluorescence quenching caused by internal filter effect in the system. The TEM image of BSA-AuNCs after adding Cr(VI) shows that a large number of large-sized nanoparticles appear in the solution Figure 6 , which is speculated to be that Cr(VI) destroys the combination of BSA and AuNCs, leading to the weakening of the protection of BSA on AuNCs, so that the gold nanoclusters gradually aggregate into large-sized gold nanoparticles, thereby losing fluorescence.

[0083] 2.2. Fluorescence lifetime

[0084] In order to further explore the interaction between Cr(VI) and BSA-AuNCs, the fluorescence lifetime of BSA-AuNCs before and after adding Cr(VI) is determined, and the results are shown in Figure 4 Fig. 3, wherein part a represents BSA-AuNCs without adding Cr(VI), and part b is the fluorescence lifetime decay curve of BSA-AuNCs after adding Cr(VI). Table 1 shows the fitting results of fluorescence lifetime.

[0085] Table 1 Comparison table of fluorescence lifetime

[0086]

[0087] Note: τ is the fluorescence lifetime value, χ 2 is chi-square test.

[0088] It can be seen that the fluorescence lifetime τ0 of BSA-AuNCs is 2.78 ns, while the fluorescence lifetime τ of BSA-AuNCs with added Cr(VI) is 2.71 ns, which is basically unchanged. τ0 / τ≈1, τ0 / τ≠F0 / F, indicating that the quenching of BSA-AuNCs by Cr(VI) is carried out in a static quenching manner.

[0089] In summary, the mechanism of Cr(VI) quenching of BSA-AuNCs fluorescence in this invention is as follows: Figure 5 As shown, specifically, after adding Cr(VI) to the BSA-AuNCs solution, Cr(VI) disrupts the binding between BSA and AuNCs, causing the AuNCs to detach from the BSA surface and aggregate in the solution to form large gold nanoparticles, thus losing fluorescence. Simultaneously, according to... Figure 6 The TEM results also show that large-sized gold nanoparticles are generated after the addition of Cr(VI), further supporting this hypothesis.

[0090] 3. The effect of different reaction times on the detection effect

[0091] The fluorescence of the test strips obtained from Application Examples 11-16 was observed under a 365 nm UV lamp, and the results are as follows. Figure 15 As shown, the red fluorescence of the BSA-AuNCs test paper gradually weakens with increasing time, and the fluorescence of the test paper almost disappears completely after 5 minutes. This should be similar to the quenching effect of Cr(VI) in the solution on BSA-AuNCs. With the increase of time, Cr(VI) interacts fully with BSA-AuNCs, which increases the degree of fluorescence quenching. Therefore, it is necessary to control the observation and measurement time during the test.

[0092] 4. The Influence of Different Metals on Detection Results

[0093] Prepare the same concentration (1.00×10⁻⁶) -7 Na (mol / L) + Ca 2+ Zn 2+ Co 2+ Mg 2+ Ni 2+ Al 3+ Fe 2+ Cu 2 + Cr 3+ solution and 1.00×10 -7 A mol / L Cr(VI) solution containing Cu 2+ and Ni 2+The above metal ion solution was sprayed on the BSA-AuNCs test paper by using the same method as in Application Example 10, and the fluorescence of the BSA-AuNCs test paper was observed under the ultraviolet lamp after the same time of action. The results are shown in Figure 16 As can be seen, only after the action of Cr(VI), the red fluorescence on the test paper is obviously weakened, while other metal ions have no obvious fluorescence quenching effect on the test paper, which is consistent with the results measured in the solution, indicating that the BSA-AuNCs test paper still has good selectivity to Cr(VI).

[0094] 5. Influence of pH of different systems on detection effect

[0095] Based on the method of Application Example 1, BR buffer solution with pH=5~11 was prepared, and the influence of different pH values on the detection of Cr(VI) by BSA-AuNCs was investigated. The results are shown in Figure 7 As can be seen, the ΔF of the system basically remains unchanged before and after the addition of Cr(VI) when the pH is between 5 and 11, but the fluorescence quenching value is higher when the pH is 6.

[0096] 6. Influence of selection of buffer solution on detection effect

[0097] Based on the method of Application Example 1, four different buffer solutions with pH=6 (BR buffer solution, disodium hydrogen phosphate-potassium dihydrogen phosphate, citric acid-sodium citrate, and disodium hydrogen phosphate-sodium dihydrogen phosphate) were selected to study the influence of buffer solution on the detection system. The results are shown in Figure 8 As can be seen, when the buffer solution is citric acid-sodium citrate, the fluorescence quenching degree of Cr(VI) on BSA-AuNCs is the largest.

[0098] 7. Interference test

[0099] Based on the method of Application Example 1, common cations (Na + , Ca 2+ , K + , Zn 2+ , Co 2+ , Mg 2+ , Ni 2+ , Al 3+ , Fe 2 + , Cu 2+ , Cr 3+ ) were selected for interference determination. The experimental results (Figure 9) show that when the concentration of interference ions is 100 times that of Cr(VI), except for Cu 2+ , Ni 2+ , other metal ions have little effect on the experimental determination, and it is inferred that Cu 2+ , Ni2+ The fluorescence quenching of the system should be caused by the combination of the characteristics of BSA-AuNCs and Cu 2+ and Ni 2+ . The interference of Cu 2+ and Ni 2+ to the determination can be eliminated by adding EDTA masking agent, indicating that BSA-AuNCs has good selectivity to Cr (VI).

[0100] 8. Effect of action time on detection effect

[0101] Based on the method of application example 1, the fluorescence intensity of BSA-AuNCs after adding Cr (VI) was measured at room temperature. As shown in Figure 10 , the fluorescence intensity of BSA-AuNCs after adding Cr (VI) decreased sharply within 20 min and remained stable after 20 min. Therefore, the detection time of Cr (VI) was selected after 20 min of action.

[0102] 9. Effect of action temperature on detection effect

[0103] Based on the method of application example 1, the fluorescence quenching degree of BSA-AuNCs by Cr (VI) was measured at room temperature (25 ℃), 40, 60, 80, and 90 ℃, respectively. The results showed that the detection effect was the best at room temperature Figure 11 within the experimental determination range, so the determination was selected at room temperature.

[0104] 10. Cr (VI) detection performance of BSA-AuNCs

[0105] The detection results of application example 2 are shown in Figure 12 . It can be seen that the fluorescence intensity of BSA-AuNCs decreases with the increase of Cr (VI) concentration within the range of 9.00×10 -7 ~ 1.00×10 -5 mol / L, and ΔF is segmented linear with Cr (VI) concentration, and the linear regression equations are ΔF=1.56×10 7 ×c+218.08 (R2=0.992), ΔF=1.55×10 8 ×c+89.97 (R 2 =0.991), and the detection limit is 4.90 nmol / L (S / N=3).

[0106] 11. Sample determination and standard addition recovery experiment were carried out on application example 1, which specifically includes the following steps: under the optimized experimental conditions, the content of Cr(VI) in the water sample was calculated by measuring the water sample according to the method of application example 1. Then different concentrations (2.00×10 -7 , 4.00×10 -7 , 6.00×10 -7 mol / L) of Cr(VI) standard solution were added to the water sample, the fluorescence signal after adding standard was measured, and the standard addition recovery rate was calculated. The experimental results are shown in Table 2:

[0107] Table 2 Sample determination results (n=3)

[0108]

[0109] It can be seen that the recovery rate of the method provided by the application is between 97.3 ~ 101.9 %, and the relative standard deviation is less than 2.0 %, which indicates that the method provided by the application has high reliability.

[0110] 12. Detection of BSA-AuNCs test paper for Cr(VI)

[0111] Take the test paper obtained in step (2) of application example 2-10, mark it as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and take another blank filter paper as a control (marked as blank). The prepared BSA-AuNCs test paper was observed under 365 nm ultraviolet lamp, and the filter papers 1-10 showed red fluorescence (part A in the middle), indicating that BSA-AuNCs was fixed on the filter paper, and blank had no luminescence, indicating that the filter paper itself had no fluorescence. Figure 13

[0112] Take 10 colorimetric tubes, and prepare different concentrations (1.00×10 -2 ~ 1.00×10 -10 mol / L) of Cr(VI) standard solution in 1-9. Spray equal amounts of different concentrations of Cr(VI) standard solution on 1-10 test papers, and observe under 365 nm ultraviolet lamp after air drying. The results show that the fluorescence of BSA-AuNCs test paper is weakened, and with the gradual increase of Cr(VI) concentration, the test paper gradually changes from red fluorescence to no fluorescence (part B in the middle, the concentration of Cr(VI) increases from left to right). Figure 13

[0113] ​​The control experiment is used to exclude the influence of filter paper and Cr(VI) solution on the test results. 10 pieces of cut filter paper are marked as 1, 2, 3, 4, 5, 6, 7, 8, 9, blank, and placed under the ultraviolet lamp (part A in FIG. 14), then 1-9 test papers are sprayed with different concentrations (1.00×10 -2 ~ 1.00×10 -10 mol / L) of Cr(VI) solution (blank is distilled water), and naturally dried under 365 nm ultraviolet lamp. The results are shown in part B of FIG. 14. It can be seen that all test papers have no fluorescence, indicating that the filter paper and Cr(VI) have no fluorescence, which does not interfere with the visual fluorescence detection. Figure 14

[0114] The same concentration (1.00×10 -7 mol / L) of Na + , Ca 2+ , Zn 2+ , Co 2+ , Mg 2+ , Ni 2+ , Al 3+ , Fe 2+ , Cu 2 + , Cr 3+ solution and 1.00×10 -7 mol / L Cr(VI) solution (EDTA is added to mask Cu 2+ and Ni 2+ solution) are prepared, and these metal ion solutions are sprayed on the BSA-AuNCs test paper according to the method for detecting Cr(VI) as described above, and then the fluorescence of the BSA-AuNCs test paper is observed under the ultraviolet lamp. As shown in FIG. 16, it is found that only when Cr(VI) is used, the red fluorescence on the test paper is weakened, and other metal ions have no fluorescence quenching effect on the test paper, which is consistent with the results of solution determination, indicating that the BSA-AuNCs test paper still has good selectivity to Cr(VI).

[0115] In summary, the BSA-AuNCs test paper prepared in the experiment can realize rapid and simple visual detection of Cr(VI).

[0116] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.​

Claims

1. A method for preparing gold nanoclusters, characterized in that, The gold nanoclusters BSA-AuNCs are prepared by a chemical reduction method using bovine serum albumin as a template and ascorbic acid as a reducing agent.

2. The method for preparing gold nanoclusters according to claim 1, characterized in that, The method comprises the following steps: After mixing the bovine serum albumin solution and the chloroauric acid solution, the ascorbic acid solution is added, the pH is adjusted, and the reaction is continuously stirred, and the solution of the gold nanoclusters is obtained after the reaction is completed.

3. The method for preparing gold nanoclusters according to claim 2, characterized in that, The concentration of the bovine serum albumin solution is 20.0 mg / mL; and / or The concentration of the chloroauric acid solution is 10.0 mmol / L; and / or The concentration of the ascorbic acid solution is 0.35 mg / mL.

4. The method for preparing gold nanoclusters according to claim 3, characterized in that, The volume ratio of the bovine serum albumin solution, the chloroauric acid solution and the ascorbic acid solution is 5:5:0.

08.

5. The method for preparing gold nanoclusters according to claim 2, characterized in that, The pH is adjusted to 12.

6. The method for preparing gold nanoclusters according to claim 2, characterized in that, The stirring temperature is 37°C, and the stirring time is 12 h.

7. The gold nanoclusters prepared by the method of any one of claims 1-6.

8. The gold nanoclusters of claim 7 are used in the fluorescence detection of Cr(VI).

9. Use according to claim 8, characterized in that, The method comprises the following steps: The qualitative filter paper is soaked in the solution of the gold nanoclusters, and is dried after the soaking is completed to obtain a BSA-AuNCs test paper; and the Cr(VI) solution is drop-coated on the BSA-AuNCs test paper, so that the visual fluorescence detection of Cr(VI) can be realized.

10. Use according to claim 8, characterized in that, The method comprises the following steps: After the gold nanoclusters are diluted and added to a buffer solution, the fluorescence value F1 is measured; then the Cr(VI) solution is added, and the fluorescence value F2 is continuously measured; and the content of Cr(VI) is detected according to the quantitative relationship between the fluorescence quenching value ΔF and the concentration of Cr(VI) added into the system. The ΔF=F1-F2.

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