A fluorescent / colorimetric dual-mode sensor for hydrogen sulfide detection and a preparation method thereof

Abstract

The application discloses a fluorescent / colorimetric dual-mode sensor for hydrogen sulfide detection and a preparation method thereof. The method comprises the following steps: synthesizing gold nanoclusters and metal-organic framework materials in situ to obtain a gold nanocluster / metal-organic framework composite material, uniformly mixing the composite material and sodium alginate to obtain a casting solution, and then dropping the casting solution on a substrate to perform scraping, molding and cleaning to obtain a gold nanocluster / metal-organic framework hydrogel membrane sensor. The sensor not only has a significant improvement in the fluorescence performance, but also can respond to hydrogen sulfide in the fluorescence and colorimetric channels respectively, and has the advantages of high sensitivity and high selectivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of fluorescent sensing technology, and relates to a fluorescent / colorimetric dual-mode sensor for hydrogen sulfide detection and a preparation method thereof. BACKGROUND

[0002] Hydrogen sulfide (H2S) is a colorless, toxic, flammable gas with a rotten egg smell at low concentrations, mainly produced in industries such as mining, pigment processing and oil refining, which poses a serious threat to human health and the environment. Even exposure to low concentrations of hydrogen sulfide can have adverse effects on the eyes and respiratory system, while high concentrations can cause asthma, coma, suffocation and even death. Therefore, the United States Occupational Safety and Health Administration (OSHA) stipulates that the allowable occupational exposure limit of hydrogen sulfide is 10 ppm for 8 hours. At the same time, hydrogen sulfide is also an endogenous gas transmitter existing in mammalian tissues, which plays a crucial role in various physiological and pathological processes. Abnormal levels of hydrogen sulfide are associated with Alzheimer's disease, asthma, cirrhosis, diabetes and other diseases. Considering the importance of hydrogen sulfide in the environment and physiology, it is of great significance to develop simple, efficient and real-time hydrogen sulfide monitoring technology.

[0003] Compared with traditional hydrogen sulfide detection techniques (such as chromatography and electrochemistry), these techniques are usually limited by complex operation, high cost, bulky equipment and low sensitivity. Fluorescent probe-based analysis is a more suitable method for on-site detection due to its fast response, easy operation and visualization. However, these fluorescent sensors still face challenges in practical applications such as complex synthesis, poor optical stability, weak single-channel signal interference, etc. In addition, fluorescence detection is easily disturbed by external light sources and needs to be operated in a dark environment. For example, gold nanoclusters (AuNCs) have attracted widespread attention in H2S detection due to their low toxicity, large Stokes shift, excellent optical stability and good biocompatibility. However, the luminescence efficiency of AuNCs is still relatively low due to excessive energy loss of ligand movement.

[0004] Based on this, the application uses porous materials to immobilize AuNCs, which embeds AuNCs in porous materials to improve their luminescence efficiency by using spatial confinement effect. Porous MOFs are assembled from metal ions and organic ligands, which have the advantages of easy synthesis, strong designability, rich luminescence sites, etc. By carefully designing the structure and fluorescence properties of this composite material, multi-channel efficient H2S detection based on AuNCs is realized. Among them, Pb-MOF can produce a visible color change due to the strong affinity between Pb clusters and H2S, which can be used as a colorimetric signal for H2S detection. This combination not only provides an ideal platform for efficient immobilization of AuNCs, but also endows the sensor with dual-channel detection capability of fluorescence and color, and excellent anti-interference ability, realizing rapid detection of hydrogen sulfide. SUMMARY

[0005] The present application aims at the deficiencies of the prior art, and provides a fluorescent / colorimetric dual-mode sensor for hydrogen sulfide and a preparation method thereof.

[0006] The technical scheme adopted by the present application is as follows:

[0007] The preparation method of the fluorescent / colorimetric dual-mode sensor for hydrogen sulfide detection comprises the following steps: in-situ compounding gold nanoclusters and lead-based metal-organic framework material to obtain a gold nanocluster / metal-organic framework composite material, then uniformly mixing the composite material with sodium alginate to prepare a casting solution, and then taking the casting solution on a substrate for scraping, shaping and cleaning to obtain the sensor.

[0008] In the above technical scheme, further, the gold nanoclusters are prepared by mixing chloroauric acid tetrahydrate with water, then adding glutathione solution, and heating and stirring, wherein the molar ratio of chloroauric acid tetrahydrate to glutathione is 1:1.5-2.

[0009] Further, the in-situ compounding specifically comprises the following steps: first, preparing a metal salt solution of lead-based metal-organic framework and an organic ligand solution at a certain temperature, then adding a gold nanocluster solution to the organic ligand solution, and then dropping the metal salt solution into the solution, stirring and reacting at the temperature, washing with deionized water after the reaction, filtering and drying to obtain the gold nanocluster / metal-organic framework composite material.

[0010] Further, the metal salt is lead nitrate, lead acetate or lead chloride.

[0011] Further, the molar ratio of the metal salt to the organic ligand is 1:1-2.

[0012] Further, the mass ratio of the gold nanoclusters to lead in the lead-based metal-organic framework material is 1:40-60.

[0013] Further, the gold nanocluster / metal-organic framework composite material and sodium alginate are added to water to mix and stir to obtain a casting solution, the casting solution is scraped on a substrate, then immersed in a calcium nitrate solution at a certain concentration for cross-linking and shaping, and then washed with water to obtain a thin film, i.e. the fluorescent / colorimetric dual-mode sensor for hydrogen sulfide detection.

[0014] Further, the mass concentration of sodium alginate in the casting solution is 0.02-0.05 g / mL, and the concentration of calcium nitrate is 30-50 mM.

[0015] Further, the thickness of the thin film is 150-400 μm.

[0016] The fluorescence / colorimetric dual-mode sensor for detecting hydrogen sulfide is prepared by any of the above methods, and is applied to on-site detection of hydrogen sulfide.

[0017] The principle of the present application is that the gold nanoclusters are introduced into the metal-organic framework material by in-situ compounding, and a composite material with dual-mode response performance is constructed. Due to the space constraint effect of Pb-MOF, the intramolecular motion of gold nanoclusters is limited, so that the fluorescence intensity of the gold nanocluster / metal-organic framework composite material is significantly improved. In addition, the material ingeniously combines the excellent fluorescence characteristics of gold nanoclusters and the chemical reaction characteristics of Pb clusters in MOF, so as to realize high sensitivity and high selectivity detection of hydrogen sulfide in the fluorescence and colorimetric channels.

[0018] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0019] (1) Compared with pure gold nanoclusters, the fluorescence performance of the gold nanocluster / metal-organic framework composite material prepared by the present application is significantly improved.

[0020] (2) Compared with gold nanoclusters, the sensor prepared by the present application has the advantages of rapid response, high sensitivity and high selectivity to hydrogen sulfide.

[0021] (3) The colorimetric and response dual-response characteristics of the sensor prepared by the present application can provide two different signals for self-verification and self-correction, thereby improving the reliability of detecting hydrogen sulfide.

[0022] (4) The thin film of the present application can realize portable real-time detection of hydrogen sulfide after being soaked in actual hydrogen sulfide solution for 3-5 minutes.

[0023] (5) Compared with the metal-organic framework powder probe, the thin film of the present application avoids the agglomeration between metal-organic framework material powders, exposes more reaction sites, and improves the sensitivity and accuracy of detection. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a preparation process schematic diagram of the gold nanocluster / metal-organic framework composite material of the present application;

[0025] Figure 2 is the fluorescence emission spectrum of pure gold nanoclusters, metal-organic framework material and gold nanocluster / metal-organic framework composite material of the present application under 395nm excitation.

[0026] Figure 3 is the fluorescence response of (b) gold nanoclusters and (a) gold nanocluster / metal-organic framework composite material to a certain concentration of H2S.

[0027] Figure 4 are the fluorescence and colorimetric images of the gold nanocluster / metal-organic framework hydrogel film of the present application exposed to different concentrations of hydrogen sulfide. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be further illustrated below in combination with examples, but these examples do not limit the protection scope of the present application, and various modifications or variations made by those skilled in the art on the basis of the technical solutions of the present application without creative labor are still within the protection scope of the present application.

[0029] Example 1:

[0030] (1) Preparation of gold nanoclusters: Mix chloroauric acid tetrahydrate (1%, 0.8 mL) with 8.7 mL of ultrapure water, then add 0.3 mL of glutathione solution (100 mM). Stir gently at 70°C for 24 h to successfully obtain a gold nanocluster solution, and store at 4°C for subsequent experiments.

[0031] (2) Preparation of gold nanocluster / metal-organic framework material: First, dissolve 0.36 mmol of lead nitrate hexahydrate (120 mg) in 4 mL of deionized water to prepare a lead nitrate solution. Take a 100 mL reaction container, dissolve 0.36 mmol of 1,3,5-benzenetricarboxylic acid (75.6 mg) in 36 mL of deionized water, and stir vigorously at 63°C for 1 h. Add 2 mL of the synthesized gold nanoclusters to the ligand solution, then slowly add the lead nitrate solution to the reaction mixture, and continue stirring at 63°C for 1 h. After the reaction is completed, wash with deionized water, filter, and dry at 60°C for 12 h to obtain a gold nanocluster / metal-organic framework composite material Figure 1 ).

[0032] (3) Preparation of hydrogel film: Take sodium alginate powder (100 mg) and gold nanocluster / metal-organic framework composite material (33 mg), add deionized water (5 mL), and dissolve with mechanical stirring. Let stand for 40 min to eliminate air bubbles to obtain a casting solution. Use a pipette to take a small drop of the above solution and drop it on a glass sheet, then use a doctor blade to spread it into a thin film. Then place the glass sheet in a calcium nitrate aqueous solution (30 mM) for shaping, with a shaping time of 3 min. Take out the thin film and wash it with deionized water to obtain a gold nanocluster / metal-organic framework hydrogel film with a mass fraction of 25%, and the thin film thickness is 250 μm.

[0033] Explore the luminescence performance of the sensor. Compared with pure gold nanoclusters, the fluorescence intensity of the gold nanocluster / metal-organic framework composite material is enhanced by 5 times (as shown in Figure 2 ), which significantly improves the luminescence performance of gold nanoclusters.

[0034] The fluorescence response performance of this sensor to hydrogen sulfide was investigated. With the addition of a certain concentration of hydrogen sulfide, the fluorescence quenching rate of this sensor for hydrogen sulfide reached as high as 73% compared to pure gold nanoclusters. Figure 3 This significantly improved the detection sensitivity. Furthermore, when the hydrogel film was exposed to different concentrations of hydrogen sulfide, the fluorescence intensity gradually decreased; under ultraviolet light irradiation, the orange-red fluorescence of the film gradually weakened; and under natural light, the film color could be observed to change from white to dark brown. Figure 4 This indicates that the sensor has a good dual-mode response to hydrogen sulfide analytes.

[0035] Example 2

[0036] (1) Preparation of gold nanoclusters: Chloroauric acid tetrahydrate (1%, 0.8 mL) was mixed with 8.7 mL of ultrapure water, and then 0.2 mL of glutathione solution (200 mM) was added. The mixture was gently stirred at 70 °C for 24 h to successfully obtain the gold nanocluster solution, which was then stored at 4 °C for subsequent experiments.

[0037] (2) Preparation of gold nanoclusters / metal-organic framework composite material: First, 0.1 mmol of lead acetate trihydrate (37.93 mg) was dissolved in 1 mL of deionized water to prepare an aqueous solution of lead acetate. In a 20 mL reaction vessel, 0.1 mmol of 1,3,5-pyromellitic acid (21 mg) was dissolved in 10 mL of deionized water, and the mixture was stirred vigorously at 63 °C for 1 h. 0.5 mL of the synthesized gold nanoclusters was added to the ligand solution, and then the lead acetate solution was slowly added to the reaction mixture. The mixture was stirred at 63 °C for another 1 h. After the reaction was complete, the mixture was washed with deionized water, filtered, and dried at 60 °C for 12 h to obtain the gold nanoclusters / metal-organic framework composite material.

[0038] (3) Preparation of hydrogel film: Take sodium alginate powder (80 mg) and gold nanoclusters / metal-organic framework composite material (20 mg), add them to deionized water (5 mL), dissolve them by mechanical stirring, and let stand for 40 min to eliminate bubbles to obtain casting solution. Use a pipette to draw the above solution, drop a small drop onto a glass slide, and use a doctor blade to coat it into a film. Then place the glass slide in Ca(NO3)2 aqueous solution (40 mM) to form it. The forming time is 3 min. Take out the film and wash it with deionized water to obtain a gold nanoclusters / metal-organic framework hydrogel film with a mass fraction of 20% and a film thickness of 200 μm.

[0039] The luminescence performance of the sensor was investigated. Compared with pure gold nanoclusters, the fluorescence intensity of the gold nanocluster / metal-organic framework composite material was increased by 2 times, significantly improving the luminescence performance of the gold nanoclusters.

[0040] The fluorescence response performance of the sensor to H2S was explored. After adding a certain concentration of hydrogen sulfide, the fluorescence quenching rate of the sensor to hydrogen sulfide was as high as 65%, significantly improving the sensitivity of detection. In addition, the fluorescence intensity of the hydrogel film gradually decreased when exposed to different concentrations of hydrogen sulfide, and the orange-red fluorescence of the film gradually weakened under the irradiation of ultraviolet light. Under natural light, the color of the film changed from white to dark brown, indicating that the sensor had good dual-mode response to hydrogen sulfide analyte.

[0041] Example 3

[0042] (1) Preparation of gold nanoclusters: Mix chloroauric acid tetrahydrate (1%, 1 mL) with 8.7 mL of ultrapure water, then add 0.2 mL of glutathione solution (150 mM). Stir gently at 70°C for 24 h to successfully obtain a gold nanocluster solution, and store at 4°C for subsequent experiments.

[0043] (2) Preparation of gold nanocluster / metal-organic framework composite material: First, dissolve 0.2 mmol of lead chloride (55.6 mg) in 2 mL of deionized water to prepare a lead chloride aqueous solution. Take a 50 mL reaction container, dissolve 0.2 mmol of 1,3,5-benzenetricarboxylic acid (42 mg) in 20 mL of deionized water, and stir vigorously at 63°C for 1 h. Add 1 mL of the synthesized gold nanoclusters to the ligand solution, then slowly add the lead chloride solution to the reaction mixture, and continue stirring at 63°C for 1 h. After the reaction is complete, wash with deionized water, filter, and dry at 60°C for 12 h to obtain a gold nanocluster / metal-organic framework composite material.

[0044] (3) Preparation of hydrogel film: Take sodium alginate powder (120 mg) and gold nanocluster / metal-organic framework composite material (25 mg), add deionized water (5 mL), and dissolve with mechanical stirring. Let stand for 40 min to eliminate air bubbles to obtain a casting solution. Use a pipette to take a small drop of the above solution and apply it to a glass sheet using a doctor blade to form a thin film. Then place the glass sheet in a calcium nitrate aqueous solution (50 mM) for 3 min to form a film. Remove the film and wash it with deionized water to obtain a gold nanocluster / metal-organic framework hydrogel film with a mass fraction of 17%, and the film thickness is 300 μm.

[0045] The luminescence performance of the sensor was explored. Compared with pure gold nanoclusters, the fluorescence intensity of the gold nanocluster / metal-organic framework composite material was enhanced by 3 times, significantly improving the luminescence performance of the gold nanoclusters.

[0046] The fluorescence response performance of the sensor to H2S was explored. After adding a certain concentration of hydrogen sulfide, the fluorescence quenching rate of the sensor to hydrogen sulfide was as high as 73% compared with pure gold nanoclusters, and the sensitivity of detection was significantly improved. In addition, the fluorescence intensity of the hydrogel film gradually decreased when exposed to different concentrations of hydrogen sulfide, and the orange-red fluorescence of the film gradually weakened under the irradiation of ultraviolet light; under natural light, the color of the film could be observed to change from white to dark brown, which indicated that the sensor had good dual-mode response to hydrogen sulfide analyte.

[0047] The above-described embodiments are only some of the preferred solutions of the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, any technical solutions obtained by equivalent replacement or equivalent transformation shall fall within the protection scope of the present application.

Claims

1. A method for the preparation of a fluorescent / colorimetric dual mode sensor for hydrogen sulfide detection, characterized by, The application relates to a sensor for detecting hydrogen sulfide, comprising: The gold nanocluster / lead metal-organic framework composite material is mixed with sodium alginate to prepare a casting solution, the casting solution is coated on a substrate, crosslinking and molding are carried out, and then the sensor is obtained after cleaning; The in-situ compounding comprises the following steps: first, a metal salt solution of a lead metal-organic framework and an organic ligand solution at a certain temperature are prepared, a gold nanocluster solution is added to the organic ligand solution, then the metal salt solution is added dropwise, stirring and reaction are carried out at the temperature, after reaction, the product is washed with deionized water, filtered and dried to obtain the gold nanocluster / lead metal-organic framework composite material.

2. A process for the preparation of a fluorescent / colorimetric dual mode sensor for hydrogen sulfide detection as claimed in claim 1, wherein, The gold nanocluster solution is prepared by mixing chloroauric acid tetrahydrate with water, adding glutathione solution and heating and stirring, wherein the molar ratio of chloroauric acid tetrahydrate to glutathione is 1:1.5-2.

3. A process for the preparation of a fluorescence / colorimetric dual mode sensor for hydrogen sulfide detection as claimed in claim 1, wherein, The metal salt is lead nitrate, lead acetate or lead chloride.

4. The process for the preparation of a fluorescent / colorimetric dual mode sensor for hydrogen sulfide detection as claimed in claim 1, wherein, The molar ratio of the metal salt to the organic ligand is 1:1-2.

5. The method for the preparation of fluorescent / colorimetric dual mode sensor for hydrogen sulfide detection as claimed in claim 1, wherein, The mass ratio of the gold nanocluster to lead in the lead metal-organic framework material is 1:40-60.

6. The method for the preparation of fluorescent / colorimetric dual mode sensor for hydrogen sulfide detection as claimed in claim 1, wherein, The gold nanocluster / lead metal-organic framework composite material and sodium alginate are mixed in water to obtain a casting solution, the casting solution is coated on a substrate, then the substrate is immersed in a calcium nitrate solution with a certain concentration to perform crosslinking and molding, and then the substrate is washed with water to obtain a film, which is a fluorescent / colorimetric dual-mode sensor for detecting hydrogen sulfide.

7. The method for the preparation of fluorescent / colorimetric dual mode sensor for hydrogen sulfide detection as claimed in claim 6, wherein, The mass concentration of sodium alginate in the casting solution is 0.02-0.05 g / mL, and the concentration of the calcium nitrate solution is 30-50 mM.

8. The method for the preparation of fluorescent / colorimetric dual mode sensor for hydrogen sulfide detection as claimed in claim 7, wherein, The thickness of the film is 150-400 mu m.

9. A fluorescence / colorimetric dual mode sensor for hydrogen sulfide detection, characterized in that, The sensor is prepared by the method in any one of claims 1-8 and is used for on-site detection of hydrogen sulfide.

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