Sulfur quantum dot fluorescent probe for detecting nitrophenol isomer as well as preparation and application of sulfur quantum dot fluorescent probe
Rhodamine 6G functional sulfur quantum dots were prepared through assembly-fission method, and used for dual-mode fluorescence sensing of nitrophenol and β-Gal, which solved the problem of poor detection accuracy and convenience in the prior art and achieved high sensitivity and environmentally friendly testing effects.
Patent Information
- Application Number
- CN202411417681.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-11
- Publication Date
- 2025-01-10
AI Technical Summary
The prior art has poor accuracy and convenience in detecting nitrophenol and β-Gal activities, and the sensing systems are mostly single-emitting fluorescence, which are greatly affected by the environment, have high cost, complex methods, low selectivity and sensitivity.
Rhodamine 6G functional sulfur quantum dots (Rho-6G-SQDs) were prepared by assembly-fission method, using it as a fluorescent probe, and dual-mode fluorescence sensing is achieved by using internal filtration effect and static quenching, combined with colorimetric detection, to achieve High sensitivity detection of p-nitrophenol isomers and β-Gal activities.
It realizes accurate and convenient detection of the activity of p-nitrophenol isomer and β-Gal, with high sensitivity, good linear relationship, simple operation, strong selectivity, and environmentally friendly, pollution-free, and stable fluorescence performance.
Smart Images
Figure CN119286504A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of analysis and detection, and specifically relates to a sulfur quantum dot fluorescent probe for detecting nitrophenol isomers and a preparation method and application thereof. Background Art
[0002] Sulfur quantum dots are a new type of environmentally friendly metal-free quantum dots. Like traditional metal-free quantum dots, they have adjustable photoluminescence properties, good dispersibility, small size, high photostability and unique antibacterial properties. Therefore, sulfur quantum dots have become a research hotspot in recent years.
[0003] Nitrophenol compounds are highly toxic and easily accumulate in water. When nitrophenol compounds enter the human body, they will be converted into carcinogens. Excessive intake will cause symptoms that endanger human health, such as dizziness, convulsions and coma. Nitrophenol is an important nitroaromatic compound. It is not only an important environmental pollutant, but also a dangerous explosive, posing a huge threat to the environment and human safety. Therefore, it is very important to effectively detect trace nitrophenol in the environment.
[0004] So far, various methods have been widely used in the sensing analysis of nitrophenol, including high performance liquid chromatography, electrochemical method, gas chromatography, colorimetry, capillary electrophoresis, etc. These methods are mostly limited by the reliance on large instruments, professional operators, cumbersome sample pretreatment and time-consuming defects. Compared with these methods, fluorescence method has the advantages of high sensitivity, good selectivity, rapid response and simple sample preparation. At present, the fluorescence detection of nitrophenol is mainly carried out by constructing fluorescent probes such as carbon dots, metal organic frameworks, covalent organic frameworks, hydrogels, etc. for the fluorescence detection of nitrophenol compounds, which has the advantages of simplicity, high efficiency and convenience. However, the sensing systems constructed based on these fluorescent probes are mostly single emission fluorescence sensing systems, and their accuracy is greatly affected by the environment in the detection of actual samples.
[0005] β-galactosidase (β-Gal), also known as lactase-phenylpropanol hydrolase, relieves lactose intolerance, so it is very important to monitor the activity of β-Gal in food and exogenous enzyme supplements. Currently, several media and systems for detecting β-Gal activity have been successfully constructed, including colorimetry, chemiluminescence, and fluorescence. However, most of these methods use the detection or imaging of intracellular β-Gal, which has the disadvantages of high cost, complex methods, low selectivity and sensitivity. Summary of the invention
[0006] In view of the problems of poor accuracy and convenience in the actual detection of nitrophenol at present, the present invention provides a sulfur quantum dot fluorescent probe for detecting nitrophenol isomers and its preparation and application.
[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing a sulfur quantum dot fluorescent probe for detecting nitrophenol isomers comprises the following steps: adopting an assembly-fission method, taking rhodamine 6G as a passivating agent and a fluorescent reference substance, adding sublimated sulfur powder and rhodamine 6G into a solution under alkaline conditions, mixing them evenly under magnetic stirring conditions, heating them for reaction after they are fully dissolved, dialyzing the filtrate and then freeze-drying them to obtain a white flocculent solid, namely, rhodamine 6G-sulfur quantum dots Rho-6G-SQDs.
[0008] Furthermore, the mass ratio of the sublimated sulfur powder to rhodamine 6G is (4-5):(0.1-0.3); and the solution is a NaOH solution with a concentration of 32 g / L.
[0009] Furthermore, the temperature of the heating reaction is 180°C, and the reaction time is 6 hours; the freeze-drying time is 12 to 24 hours; and the dialysis purification refers to dialysis in a dialysis bag with a molecular weight cutoff of 3500Da for 12 to 24 hours, and the water is changed twice every 6 hours.
[0010] Furthermore, the sulfur quantum dot fluorescent probe has a spherical structure and an average particle size of 7.65±0.5 nm; when the sulfur quantum dot fluorescent probe is excited at a wavelength of 310 nm, the fluorescence spectrum of the sulfur quantum dot fluorescent probe has relatively stable fluorescence emission peaks at wavelengths of 414 nm and 516 nm.
[0011] The application of sulfur quantum dot fluorescent probe for detecting nitrophenol isomers in the dual-mode fluorescence sensing system of nitrophenol isomers is based on the inner filter effect and static quenching between nitrophenol and Rho-6G-SQDs. The ratio fluorescence quenching of Rho-6G-SQDs is accompanied by a change in the color of the solution. Under ultraviolet light, the sensing system solution produces a color change from yellow to green, thereby realizing dual-mode, i.e., ratio fluorescence and smartphone colorimetric detection capabilities.
[0012] Furthermore, the optimal detection conditions of the fluorescence sensing system are: the concentration of Rho-6G-SQDs is 35 mg / mL, the pH of the PBS buffer system is 8.0, and the reaction time is 2 min.
[0013] Furthermore, the three isomers of p-nitrophenol all have dual-channel responses of fluorescence and colorimetry. o- Nitrophenol, m- Nitrophenol and p The three isomers of -nitrophenol have different responses, and the specific fluorescence quenching amplitudes are: o- Nitrophenol< m -Nitrophenol< p- Nitrophenol, and p-The fluorescence quenching of nitrophenol is accompanied by a red shift in the fluorescence wavelength at 414 nm.
[0014] Application of sulfur quantum dot fluorescent probe for detecting nitrophenol isomers in the ratiometric fluorescence sensing system of β-galactosidase (β-Gal) activity. In the presence of β-galactosidase (β-Gal), p-nitrophenyl-β-d-galactoside (PNPG) is hydrolyzed to generate p-nitrophenol ( p -NP), based on p-nitrophenol ( p The static quenching between Rho-6G-SQDs and Rho-6G-NPs was used to measure the fluorescence intensity of Rho-6G-SQDs, thus realizing the ratiometric fluorescence determination of β-Gal activity.
[0015] The invention discloses an application of a sulfur quantum dot fluorescent probe for detecting nitrophenol isomers in a ratiometric fluorescence sensing system for β-galactosidase (β-Gal) activity. The optimal detection conditions of the ratiometric fluorescence sensing system are as follows: the concentration of Rho-6G-SQDs is 10 mg / mL, the optimal concentration of the substrate p-nitrophenyl-β-d-galactoside (PNPG) is 20 mM, the optimal pH value for the system is 7.5, the incubation temperature is 37°C, the action time of p-nitrophenyl-β-d-galactoside (PNPG) and the enzyme is 6 min, and the activity of p-nitrophenol ( p The binding time of NPs and Rho-6G-SQDs was 4 min.
[0016] The application of sulfur quantum dot fluorescent probe for detecting nitrophenol isomers in α-glucosidase (α-Glu) ratio fluorescence sensing system can specifically hydrolyze its substrate p-nitrophenyl-α-D-pyranoglucoside into p-nitrophenol ( p -NP), based on p-nitrophenol ( p The static quenching between Rho-6G-SQDs and Rho-6G-NP was realized by measuring the fluorescence intensity of Rho-6G-SQDs to achieve the ratiometric fluorescence determination of α-glucosidase (α-Glu) activity.
[0017] Compared with the prior art, the present invention has the following advantages: The present invention uses cheap sulfur powder as a sulfur source, uses rhodamine 6G as a passivator and a fluorescent reference substance, and the obtained rhodamine 6G functionalized sulfur quantum dots have the characteristics of bimodal emission, good fluorescence performance and light stability. When the excitation wavelength is 310 nm, it has fluorescence peaks of different intensities at wavelengths of 414 nm and 516 nm, and the peak shape of the fluorescence emission peak is good. The preparation process of the sulfur quantum dots is simple to operate, and it is a green and pollution-free preparation method. The prepared sulfur quantum dots show a spherical structure, good dispersibility, an average particle size of 7.67±0.5 nm, and a quantum yield of 0.04.
[0018] The present invention also provides the application of sulfur quantum dots prepared according to the preparation method in dual-mode recognition of nitrophenol isomers. When Rho-6G-SQDs react with nitrophenol isomers respectively, the fluorescence is significantly reduced, and the color change in the system can be observed under ultraviolet light. This shows that Rho-6G-SQDs can realize dual-mode recognition sensing of nitrophenol isomer molecules.
[0019] The present invention also provides the application of sulfur quantum dots in the dual-mode recognition of nitrophenol isomers. o -Nitrophenol and p -nitrophenol reaction, the two fluorescence peaks showed a ratiometric decrease, while Rho-6G-SQDs and m - When nitrophenol reacts, the intensities of the two fluorescence peaks decrease linearly, but not proportionally. The color change of the system can be observed under ultraviolet light. This shows that Rho-6G-SQDs can realize dual-channel detection sensing of nitrophenol isomer molecules. o -、 m -、 p The relationship between the fluorescence change and color change of the Rho-6G-SQDs-nitrophenol system and the corresponding system was used to establish a standard curve for the recognition and detection of nitrophenol isomers. With the increase of the concentration of nitrophenol components, the fluorescence intensity of the Rho-6G-SQDs-nitrophenol system decreased significantly, and the color changed from yellow to green. The changes in fluorescence intensity and color were consistent with the o -、 m -、 p The concentration of -nitrophenol showed a good linear relationship.
[0020] The preparation method of synthesizing rhodamine 6G sulfur quantum dots by a reactor method disclosed in the present invention is environmentally friendly, simple, has simple and easy steps, and has stable fluorescence performance. The Rho-6G-SQDs prepared by the method have a bimodal emission characteristic that can be ratiometrically identified, and there is an inner filter effect and static quenching between nitrophenol and Rho-6G-SQDs. Therefore, rhodamine 6G sulfur quantum dots can be directly used to realize dual-mode identification of nitrophenol isomer molecules. The method has high sensitivity, good linear relationship, simple and easy operation, good selectivity, and strong anti-interference ability.
[0021] The present invention also provides the use of sulfur quantum dots prepared according to the preparation method in the ratio fluorescence sensing of β-galactosidase (β-Gal) activity, wherein β-Gal catalyzes the hydrolysis of the substrate p-nitrophenyl-β- d -galactoside (PNPG) to generate p-nitrophenol (p-NP). At a single excitation wavelength of 310 nm, the product p-NP can quench the fluorescence of Rho-6G-SQDs at 414 nm, but has little effect on the fluorescence of SQDs-Rho6G at 516 nm. By measuring the fluorescence intensity at 414 nm and 516 nm, the ratio fluorescence determination of β-Gal activity is achieved. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is a transmission electron microscope image of the sulfur quantum dots in Example 1.
[0023] Figure 2 The fluorescence emission spectrum and UV-visible absorption spectrum of the sulfur quantum dots in Example 1 under different excitation wavelengths.
[0024] Figure 3 For different concentrations o -、 p -Linear relationship diagram of the fluorescence spectrum of sulfur quantum dot solution and the change of target concentration and fluorescence intensity of the system in the presence of nitrophenol.
[0025] Figure 4 For different concentrations m -Linear relationship diagram of the fluorescence spectrum of sulfur quantum dot solution and the change of target concentration and fluorescence intensity of the system in the presence of nitrophenol.
[0026] Figure 5 for o -、 m -、 p -Linear relationship between the concentration ratio of nitrophenol and the color change of the system.
[0027] Figure 6 The figure is a linear relationship diagram of the fluorescence spectrum of the sulfur quantum dot solution, the target concentration and the change of the fluorescence intensity of the system when different concentrations of β-Gal exist.
[0028] Figure 7 is the recovery rate of the actual sample spike.
[0029] Figure 8 This is a schematic diagram of the optimization results of the detection condition data in Example 2.
[0030] Fig. 9 This is a schematic diagram of the optimization results of the detection condition data of Example 6. DETAILED DESCRIPTION
[0031] In order to gain a deeper understanding of the present invention, we will provide a comprehensive and detailed description of the present invention. However, the present invention has multiple implementations and is not limited to the specific examples listed herein. The presentation of these examples is intended to deepen the comprehensive understanding of the disclosure of the present invention.
[0032] Example 1
[0033] A method for preparing a sulfur quantum dot fluorescent probe for detecting nitrophenol isomers comprises the following steps: First, 0.80 g NaOH was added to 25 mL deionized water to dissolve, and then 0.30 g sublimated sulfur powder and 50 mL Rho-6G (1 mM) were added to the NaOH solution. After the mixture was stirred evenly and fully dissolved in a magnetic heating stirrer, it was transferred to a reactor and reacted at 180 ° C in an electric heating blast drying oven for 6 h. After cooling to room temperature, the dialysis membrane with a cutoff of 3500 Da was used for 24 h, and the dialysis water was replaced at intervals of 4, 4, 6, and 10 h, respectively. The dialyzed sample was freeze-dried for 24 h to obtain a white flocculent solid, namely rhodamine 6G-sulfur quantum dots (Rho-6G-SQDs). A water-soluble Rho-6G-SQDs solution of the desired concentration can be prepared.
[0034] The morphology of sulfur quantum dots was analyzed using transmission electron microscopy. Figure 1 As shown, it can be seen that the prepared sulfur quantum dots exhibit a spherical structure with good dispersion and an average particle size of 7.65±0.5 nm. HR-TEM shows that the lattice spacing of Rho-6G-SQDs is 0.3127 nm.
[0035] The fluorescence spectrum of Rho-6G-SQDs prepared in the present invention under 310-340 nm excitation is as follows: Figure 2 As shown in the figure, as the excitation wavelength gradually shifts from 310 nm to 340 nm, the fluorescence intensity of Rho-6G-SQDs gradually weakens, and the fluorescence spectrum does not shift significantly. Figure 2As shown, the prepared sulfur quantum dots have an absorption peak at 220 nm. Using quinine sulfate (0.10 mol / L H2SO4) as a reference, the fluorescence quantum yield of Rho-6G-SQDs prepared by this method was determined to be 0.04 under excitation at 310 nm. When the excitation wavelength is 310 nm, the fluorescence spectrum of sulfur quantum dots has relatively stable fluorescence emission peaks at wavelengths of 414 nm and 516 nm, and the peak shape is good.
[0036] Example 2
[0037] Selection of Rho-6G-SQDs concentration in the Rho-6G-SQDs and nitrophenol reaction system: In order to obtain the best sensing effect, the sulfur quantum dot concentration, pH, reaction time and other conditions were optimized, and it was found that the optimal detection conditions of the fluorescence sensing system were: Rho-6G-SQDs concentration was 35 mg / mL, pH = 8.0 (PBS buffer system), and the reaction time was 2 min. Figure 8 The schematic diagram of the detection condition data optimization results is shown.
[0038] Example 3
[0039] Application of the sulfur quantum dots (Rho-6G-SQDs) obtained in Example 1 in dual-mode recognition in o-nitrophenol and p-nitrophenol systems.
[0040] The isomer dual-mode recognition method is as follows: the fluorescence intensity of the Rho-6G-SQDs-nitrophenol system is studied as o- Nitrophenol and p - Changes in nitrophenol concentration, and according to o -Nitrophenol and p -Nitrophenol concentration and the corresponding fluorescence change of the system (F 414 / F 516 ) to establish a standard curve for nitrophenol analysis. Figure 3 With o-nitrophenol ( o With the increase of the concentration of Rho-6G-SQDs, the fluorescence of Rho-6G-SQDs was gradually quenched, and at the same time, the fluorescence at 414 nm was red-shifted. The fluorescence ratio (F 414 / F 516 ) showed a rapid downward trend in the range of 0-2500 mM o-nitrophenol, and then gradually stabilized in the range of 2500-4000 mM; with the increase of p-nitrophenol ( p With the increase of the concentration of Rho-6G-SQDs, the fluorescence of Rho-6G-SQDs was gradually quenched, and at the same time, the fluorescence at 414 nm was red-shifted. The fluorescence ratio (F 414 / F 516) shows a rapid downward trend in the range of 0~100 mM p-nitrophenol, and then gradually stabilizes at 100~200 mM. The experiment shows that Rho-6G-SQDs can realize the ratio fluorescence sensing system of o- and p-nitrophenol.
[0041] Example 4
[0042] Application of the sulfur quantum dot solution obtained in Example 1 in dual-mode recognition in the m-nitrophenol system.
[0043] The isomer dual-mode recognition method is as follows: the fluorescence intensity of the Rho-6G-SQDs-nitrophenol system is studied as m- The changes of nitrophenol and m The relationship between the concentration of -nitrophenol and the corresponding fluorescence change (F / F0) of the system was used to establish the standard curve for nitrophenol analysis and detection. Figure 4 As the concentration of m-nitrophenol (m-NP) increases, the fluorescence of Rho-6G-SQDs is gradually quenched, and the fluorescence (F0 / F) of Rho-6G-SQDs decreases rapidly in the range of 0-1000 mM m-nitrophenol, and then gradually stabilizes in the range of 1000-2000 mM. The ratio of the ratio fluorescence in this system is not linear, but the fluorescence at 414 nm and 516 nm is linearly related to the concentration of m-nitrophenol. The experiment shows that Rho-6G-SQDs can realize the fluorescence sensing system of m-nitrophenol.
[0044] Example 5
[0045] Application of the sulfur quantum dot solution obtained in Example 1 in the nitrophenol isomer colorimetric system.
[0046] The method of isomer dual-mode identification is as follows: a portable smartphone sensing system is made, that is, the analyte is added to a cuvette containing the Rho-6G-SQDs sensing solution, and a mobile phone software is used to take photos and obtain colors in a dark room under ultraviolet light to obtain the RGB values of Rho-6G-SQDs at different nitrophenol concentrations. Three photos are taken at each concentration for analysis. The RGB ratio of the image is obtained using the color analysis software (Android-Xiaolu Color Picker). Figure 5 As shown, with different concentrations of the test substance ( o -NP, m -NP, p -NP) was added, the color of the solution gradually changed from yellow to green and then darkened under ultraviolet light.
[0047] Compared with these single-emission fluorescence sensing systems, the ratiometric fluorescence probe realizes fluorescence sensing through the linear relationship between the concentration of nitrophenol and the intensity ratio of the fluorescence double peak emission. By recording two independent emissions of the same excitation wavelength, it can achieve self-correction of environmental interference, making the fluorescence detection results more accurate. And the construction of a dual-mode recognition and detection system for nitrophenol combined with colorimetric sensing is more conducive to improving the accuracy and convenience of detection.
[0048] Example 6
[0049] The optimal detection conditions of Rho-6G-SQDs in the β-galactosidase ratio fluorescence sensing system are: the concentration of sulfur quantum dots is 10 mg / mL, the optimal concentration of substrate PNPG is 20 mM, the optimal pH of the system is 7.5, the incubation temperature is 37°C, the action time of PNPG and enzyme is 6 min, and the binding time of the product and sulfur quantum dots is 4 min. Fig. 9 The results of the detection condition data optimization are shown.
[0050] Example 7
[0051] Application of the sulfur quantum dot solution obtained in Example 1 in a β-galactosidase ratio fluorescence sensing system.
[0052] The ratio fluorescence sensing method is based on the hydrolysis of the substrate p-nitrophenyl-β-d-galactoside (PNPG) catalyzed by β-galactosidase to generate p-nitrophenol (p-NP), and the ratio fluorescence change (F 414 / F 516 ) to establish a standard curve for β-galactosidase activity analysis. Figure 6 As the activity of β-galactosidase increases, the fluorescence of Rho-6G-SQDs at 414 nm gradually quenches, and the fluorescence intensity at 516 nm remains basically unchanged. 414 / F 516 ) in the range of 0-40 U·L −1 The concentration range showed a downward trend, and the experiment showed that Rho-6G-SQDs could be used as a ratiometric fluorescence sensing system for detecting β-galactosidase activity.
[0053] Example 8
[0054] Application of the sulfur quantum dot solution obtained in Example 1 in an α-glucosidase (α-Glu) ratio fluorescence sensing system.
[0055] The ratio fluorescence sensing method is based on the fact that α-Glu can specifically hydrolyze its substrate p-nitrophenyl-α-D-pyranoglucoside into p-NP, and the ratio fluorescence change (F 414 / F 516 ) to establish a standard curve for α-Glu activity analysis. Figure 7 As the activity of α-Glu increases, the fluorescence of Rho-6G-SQDs at 414 nm gradually quenches, and the fluorescence intensity at 516 nm remains basically unchanged. 414 / F 516 ) in the range of 0~50 U·L −1 The concentration range showed a downward trend, and the experiment showed that Rho-6G-SQDs could be used as a ratiometric fluorescence sensing system for detecting α-Glu activity.
[0056] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. Although the illustrative specific embodiments of the present invention are described above to facilitate the understanding of the present invention by the technical personnel in the field, it should be clear that the present invention is not limited to the scope of the specific embodiments. For the ordinary technical personnel in the field, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.
Claims
1. A method for preparing a sulfur quantum dot fluorescent probe for detecting nitrophenol isomers, characterized in that: The assembly-fission method was adopted, with rhodamine 6G as a passivating agent and fluorescent reference substance. Sublimated sulfur powder and rhodamine 6G were added to the solution under alkaline conditions, mixed under magnetic stirring conditions, heated to react after full dissolution, and the filtrate was dialyzed and freeze-dried to obtain a white flocculent solid, namely rhodamine 6G-sulfur quantum dots Rho-6G-SQDs.
2. The method for preparing a sulfur quantum dot fluorescent probe for detecting nitrophenol isomers according to claim 1, characterized in that: The mass ratio of the sublimated sulfur powder to rhodamine 6G is (4-5):(0.1-0.3); the solution is a NaOH solution with a concentration of 32 g / L.
3. The method for preparing a sulfur quantum dot fluorescent probe for detecting nitrophenol isomers according to claim 1, characterized in that: The temperature of the heating reaction is 180°C, and the reaction time is 6 hours; the freeze-drying time is 12 to 24 hours; the dialysis purification refers to dialysis in a dialysis bag with a molecular weight cutoff of 3500Da for 12 to 24 hours, and the water is changed twice every 6 hours.
4. The sulfur quantum dot fluorescent probe for detecting nitrophenol isomers prepared by the preparation method according to claim 1, characterized in that: The sulfur quantum dot fluorescent probe has a spherical structure and an average particle size of 7.65±0.5 nm. When the sulfur quantum dot fluorescent probe is excited at a wavelength of 310 nm, the fluorescence spectrum of the sulfur quantum dot fluorescent probe has relatively stable fluorescence emission peaks at wavelengths of 414 nm and 516 nm.
5. The use of the sulfur quantum dot fluorescent probe for detecting nitrophenol isomers prepared by the preparation method according to claim 1 in a nitrophenol isomer dual-mode fluorescent sensing system, characterized in that: Based on the inner filter effect and static quenching between nitrophenol and Rho-6G-SQDs, the ratio fluorescence quenching of Rho-6G-SQDs is accompanied by a change in the color of the solution. Under ultraviolet light, the sensing system solution changes color from yellow to green, thus realizing dual-mode ratio fluorescence and smartphone colorimetric detection capabilities.
6. The use of the sulfur quantum dot fluorescent probe for detecting nitrophenol isomers according to claim 5 in a nitrophenol isomer dual-mode fluorescent sensing system, characterized in that: The optimal detection conditions of the fluorescence sensing system are: the concentration of Rho-6G-SQDs is 35 mg / mL, the pH of the PBS buffer system is 8.0, and the reaction time is 2 min.
7. The use of the sulfur quantum dot fluorescent probe for detecting nitrophenol isomers according to claim 6 in a nitrophenol isomer dual-mode fluorescent sensing system, characterized in that: The three isomers of p-nitrophenol all have dual-channel responses of fluorescence and colorimetry. o- Nitrophenol, m- Nitrophenol and p The three isomers of -nitrophenol have different responses, and the specific fluorescence quenching amplitudes are: o- Nitrophenol< m -Nitrophenol< p- Nitrophenol, and p- The fluorescence quenching of nitrophenol is accompanied by a red shift in the fluorescence wavelength at 414 nm.
8. The use of the sulfur quantum dot fluorescent probe for detecting nitrophenol isomers prepared by the preparation method according to claim 1 in a ratiometric fluorescent sensing system for β-galactosidase activity, characterized in that: In the presence of β-galactosidase, p-nitrophenyl-β-d-galactoside was hydrolyzed to generate p-nitrophenol. Based on the static quenching between p-nitrophenol and Rho-6G-SQDs, the ratiometric fluorescence determination of β-Gal activity was achieved by measuring the fluorescence intensity of Rho-6G-SQDs.
9. The use of the sulfur quantum dot fluorescent probe for detecting nitrophenol isomers prepared by the preparation method according to claim 8 in a ratiometric fluorescent sensing system for β-galactosidase activity, characterized in that: The optimal detection conditions of the ratio fluorescence sensing system are as follows: the concentration of Rho-6G-SQDs is 10 mg / mL, the optimal concentration of the substrate p-nitrophenyl-β-d-galactoside is 20 mM, the optimal pH for sensing of the system is 7.5, the incubation temperature is 37°C, the action time of p-nitrophenyl-β-d-galactoside and the enzyme is 6 min, and the binding time of p-nitrophenol and Rho-6G-SQDs is 4 min.
10. Application of the sulfur quantum dot fluorescent probe for detecting nitrophenol isomers prepared by the preparation method according to claim 1 in an α-glucosidase ratio fluorescence sensing system, characterized in that: In the presence of α-glucosidase, it can specifically hydrolyze its substrate p-nitrophenyl-α-D-pyranoglucoside into p-nitrophenol. Based on the static quenching between p-nitrophenol and Rho-6G-SQDs, the ratiometric fluorescence determination of α-glucosidase activity was achieved by measuring the fluorescence intensity of Rho-6G-SQDs.