Ceo 2-based enhanced fluorescent probe and use thereof in detection of sulfur ions or sulfate-reducing bacteria

Abstract

The present invention belongs to the technical field of fluorescent sensing, and relates to a CeO2-based enhanced fluorescent probe and the use thereof in the detection of sulfur ions or sulfate-reducing bacteria. The enhanced fluorescent probe of the present invention is obtained by means of loading cerium dioxide (CeO2) on a metal organic framework material (MOF) and then adsorbing fluorescent dye, i.e. riboflavin sodium monophosphate (FMN-Na). The fluorescent probe of the present invention can achieve fluorescence enhancement, thereby improving detection sensitivity; and the synthesis mode thereof is simple, the cost is low, and the fluorescent response to sulfur ions (S2-) and a sulfate-reducing bacteria (SRB) liquid is very significant. The fluorescence enhancement probe can also be designed as a double-quenching fluorescence probe, achieves high-sensitivity and wide-linear-range detection of sulfur ions by means of correction, has the advantages of high selectivity, rapid detection, strong practicability, etc., and provides potential application prospects for rapid detection of harmful microorganisms in a water environment.

Description

CeO2-enhanced fluorescent probe and application thereof in detection of sulfur ions or sulfate-reducing bacteria TECHNICAL FIELD

[0001] The application belongs to the technical field of fluorescent sensing, and particularly relates to a CeO2-enhanced fluorescent probe and application thereof in detection of sulfur ions or sulfate-reducing bacteria. BACKGROUND

[0002] Protecting the Yangtze River Basin is a major requirement for maintaining national ecological security. In order to better protect the Yangtze River Basin, online monitoring of water quality is very important. However, due to technical constraints, only a few pollutants can be monitored online. The sensitivity and specificity of harmful microorganism monitoring have not yet met the requirements, and there are still gaps in water pollution risk prevention. The research on water quality change mechanism and carbon emission has encountered technical bottlenecks. Therefore, it is an urgent need for the Yangtze River protection in the new era to develop online automatic monitoring technology and equipment suitable for the Yangtze River water environment, and to improve the monitoring capability of harmful microorganisms in the water environment and the research level of water quality change mechanism.

[0003] At present, the total wastewater discharge in the Yangtze River Economic Belt accounts for more than 40% of the total in China, and nearly 50% of the water source risk prevention and control capability is insufficient. Some rivers and lakes have changed from carbon sinks to carbon sources, and there are a large number of black and odorous water bodies. At the same time, research shows that the methane emission of lakes accounts for about 25% of the global emission. The "culprit" of these phenomena is mostly derived from sulfate-reducing bacteria (SRB). A small amount of SRB metabolism produces sulfide, which can greatly promote the production of methane by methanogens, leading to the transformation of water bodies to carbon sources, while a large amount of SRB produces a large amount of hydrogen sulfide, inducing black and odorous water bodies. These serious environmental problems will aggravate the greenhouse effect, and the hydrogen sulfide in black and odorous water bodies will lead to biological diseases and serious corrosion of industrial environment, resulting in economic losses and even life safety. Therefore, it is urgent to develop a high-sensitivity and convenient SRB sensor. Therefore, based on the characteristic metabolic product of SRB, i.e., sulfur ions, a sulfur ion and SRB probe is designed with enhanced fluorescence as the core technology, which has the advantages of high sensitivity, good visualization effect, strong specificity, and convenience for on-site monitoring, so as to more accurately, comprehensively and intuitively judge the water quality change, and provide an important basis for carbon emission, formation of black and odorous water bodies, and water pollution in the water environment, so as to protect the beautiful water environment.

[0004] Traditional microorganism detection methods such as SRB mainly adopt dilution culture technology, PCR technology, ELISA, etc., which have low sensitivity, long time, large error, and are difficult to realize on-site detection. Therefore, in recent years, electrochemical sensors have been greatly developed for detecting sulfur ions and sulfate-reducing bacteria. However, there are still great technical bottlenecks in realizing online monitoring of sulfate-reducing bacteria.

[0005] Fluorescence detection is a multi-functional spectral detection method with the characteristics of short response period, high sensitivity, simple technology and wide applicability, which can be widely applied to real-time and on-site detection. However, at present, fluorescence sensing is mostly used for foodborne microbial detection, and there are few reports on environmental microorganisms, especially SRB. Therefore, it is urgent to establish a rapid and efficient SRB detection method based on fluorescence analysis. 2- The fluorescence analysis method is used to detect sulfate-reducing bacteria, so as to monitor and protect the water environment in an urgent manner. However, the fluorescence probes for detecting sulfide ions still have the defects of insufficient intensity and narrow linear range, and cannot accurately quantify the content of bacteria in the water environment. Therefore, it is of great significance to realize fluorescence enhancement to expand the linear range and sensitivity.

SUMMARY

[0006] In order to overcome the above defects or improvement needs of the prior art, the present application provides an enhanced fluorescence probe capable of detecting sulfide ions and sulfate-reducing bacteria SRB. CeO2 particles are loaded on metal organic framework materials MOFs with cobalt or copper as metal sites, and then the fluorescence dye riboflavin monophosphate sodium FMN-Na is modified through electrostatic adsorption and precipitation reaction to obtain the enhanced fluorescence probe (MOFs@CeO2@FMN-Na). The enhanced fluorescence probe prepared by the present application realizes high sensitivity and wide linear range detection of sulfide ions or sulfate-reducing bacteria through enhanced fluorescence signal, thereby solving the technical problems of insufficient intensity and narrow linear range of the fluorescence probe for detecting sulfide ions or sulfate-reducing bacteria in the prior art.

[0007] According to a first aspect of the present application, a preparation method of a CeO2-based enhanced fluorescence probe is provided, comprising the following steps:

[0008] (1) Injecting a dispersion liquid of organic framework material into a cerium source solution, then adding a complexing precipitant, and then heating, separating the generated precipitate to obtain a metal organic framework loaded with CeO2 particles; wherein the organic framework material is an organic framework material containing metal cobalt elements or an organic framework material containing metal copper elements;

[0009] (2) Adding riboflavin monophosphate sodium solution to the metal organic framework loaded with CeO2 particles obtained in step (1), and connecting the riboflavin monophosphate sodium to the CeO2 particles, to obtain a CeO2-based enhanced fluorescence probe.

[0010] Preferably, the ligand of the organic framework material is at least one of dimethyl imidazole, bipyridine, terephthalic acid, trimesic acid, and naphthalene acid.

[0011] Preferably, the ligand of the organic framework material MOFs includes at least one of amino terephthalic acid, hydroxy terephthalic acid, and 2,6-bis(2-pyrazinyl)-4,4'-bipyridine.

[0012] According to another aspect of the present application, there is provided a CeO2-based enhanced fluorescent probe prepared by any one of the methods.

[0013] According to another aspect of the present application, there is provided a use of the CeO2-based enhanced fluorescent probe for detecting sulfate ions.

[0014] Preferably, the use specifically comprises the following steps:

[0015] (1) adding the CeO2-based enhanced fluorescent probe to a salt solution containing sulfate ions with gradient concentrations, then performing fluorescence detection, and establishing a relationship curve between the fluorescence intensity at the peak value and the concentration of sulfate ions;

[0016] (2) adding the CeO2-based enhanced fluorescent probe to a solution to be detected, and performing fluorescence detection under the same excitation wavelength as that in step (1), then obtaining the concentration of sulfate ions in the solution to be detected according to the relationship curve in step (1).

[0017] Preferably, the use specifically comprises the following steps:

[0018] (1) adding the CeO2-based enhanced fluorescent probe to a salt solution containing sulfate ions with gradient concentrations, then performing fluorescence detection, and establishing a relationship curve between the ratio of the fluorescence intensity at the two peak values and the concentration of sulfate ions;

[0019] (2) adding the CeO2-based enhanced fluorescent probe to a solution to be detected, and performing fluorescence detection under the same excitation wavelength as that in step (1), then obtaining the concentration of sulfate ions in the solution to be detected according to the relationship curve in step (1).

[0020] According to another aspect of the present application, there is provided a use of the CeO2-based enhanced fluorescent probe for detecting the concentration of sulfate-reducing bacteria.

[0021] Preferably, the use specifically comprises the following steps:

[0022] (1) adding the CeO2-based enhanced fluorescent probe to a bacterial solution of sulfate-reducing bacteria with gradient concentrations, then performing fluorescence detection, and establishing a relationship curve between the fluorescence intensity at the peak value and the concentration of sulfate-reducing bacteria;

[0023] (2) adding the CeO2-based enhanced fluorescent probe to a bacterial solution to be detected, and performing fluorescence detection under the same excitation wavelength as that in step (1), then obtaining the concentration of sulfate-reducing bacteria in the bacterial solution to be detected according to the relationship curve in step (1).

[0024] Preferably, the use specifically comprises the following steps:

[0025] (1) the CeO2-based enhanced fluorescence probe is added to the bacterial solution of sulfate-reducing bacteria with gradient concentration, and then fluorescence detection is performed, and a relationship curve of the fluorescence intensity ratio at two peak values to the concentration of sulfate-reducing bacteria is established;

[0026] (2) the CeO2-based enhanced fluorescence probe is added to the bacterial solution to be detected, and fluorescence detection is performed under the same excitation wavelength as that in step (1), and then the concentration of sulfate-reducing bacteria in the bacterial solution to be detected is obtained according to the relationship curve in step (1).

[0027] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages:

[0028] (1) The preparation method of the MOFs loaded CeO2 connecting fluorescent dye composite material of the present application connects the fluorescent dye riboflavin monophosphate sodium FMN-Na through the strong action of CeO2 on phosphate, solves the problems that FMN-Na is easily quenched by solvent molecules and easily photo-degraded and oxidized, and is difficult to utilize, realizes nearly 30-fold fluorescence enhancement of FMN-Na in aqueous solution, improves the highest detection concentration (from 10-50 μM to 270 μM), ensures that the detection limit is sufficient for practical detection, and overall expands the linear range, which is more suitable for the detection of sulfate-reducing bacteria in water quality environment.

[0029] (2) For a long time, research has been focused on the effect of noble metal materials on fluorescence enhancement, while research on semiconductors is relatively less. Semiconductors (especially metal oxides) have high abundance in the earth's crust, low cost, and more advantages and potential in industrial applications. The strong interaction between CeO2 and fluorescent groups with phosphate enables the fluorescent dye FMN-Na to emit bright fluorescence due to the restriction of intramolecular group movement in the aggregated state. In addition, recent research shows that some degenerate doped semiconductors have significant surface plasmon effects. CeO2 is a semiconductor material containing abundant oxygen vacancies, and by adjusting the synthesis of CeO2, CeO2 can have a plasmonic-like effect on fluorescence enhancement of fluorescent dyes. The construction of a semiconductor-enhanced fluorescence model can provide a theoretical value reference for the design of biosensors.

[0030] (3) The fluorescent probe of the present application can realize fluorescence enhancement, improve the detection sensitivity, and has a very significant fluorescent response to sulfur ions and sulfate-reducing bacteria (SRB) metabolic bacteria solution. Preferably, the enhanced fluorescent probe can also be designed into a double-quenching fluorescent probe, which refers to measuring the intensity of the emission spectrum at two wavelengths, correcting the error caused by the change of the local environment by making the fluorescence ratio at two wavelengths and the working curve of the measured object, so as to realize the high sensitivity and wide linear range detection of sulfur ions, and has the advantages of high selectivity, rapid detection, strong practicability and the like, and provides potential application prospects for rapid detection of harmful microorganisms in water environment.

[0031] (4) The present application is based on the reaction that cobalt or copper ions can specifically bind with sulfur ions to generate precipitates, and a fluorescent probe is designed based on the energy competition absorption of sulfide precipitates and fluorescent dyes as the quenching mechanism. Only when S 2- exists, the fluorescence emission peak changes significantly. Other common anions in water have a lower binding ability with cobalt or copper ions than sulfur ions, and in addition, the precipitates formed by a small number of interfering ions do not have strong energy competition absorption with fluorescent dyes, so the fluorescent probe has good anti-interference effect, good specificity, and good application prospect in water quality detection. BRIEF DESCRIPTION OF DRAWINGS

[0032] Fig. 1 is the fluorescence spectrum of MOFs@CeO2@FMN-Na under different S 2- concentrations (0-300 μM).

[0033] Fig. 2 is the correlation curve of fluorescence intensity F533 and S 2- concentration.

[0034] Fig. 3 is the corresponding fluorescence spectrum of S 2- probe selectivity experiment and anti-interference experiment.

[0035] Fig. 4 is the corresponding relative fluorescence intensity of S 2- probe selectivity experiment and anti-interference experiment.

[0036] Fig. 5 is the fluorescence spectrum of MOFs@CeO2@FMN-Na under different SRB bacteria solution concentrations (0-5.9*10 4 cells / mL).

[0037] Fig. 6 is the correlation curve of fluorescence intensity F533 and SRB bacteria solution concentration.

[0038] Fig. 7 is the fluorescence spectrum of MOFs@CeO2@FMN-Na under different S 2- concentrations (0-2.6 mM).

[0039] Figure 8 is a correlation curve of fluorescence intensity ratio F531 / F431 and S 2- concentration.

[0040] Figure 9 is a fluorescence spectrum of probes prepared from different materials.

DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0042] The present application provides a fluorescence-enhanced probe capable of detecting sulfur ions and sulfate-reducing bacteria (SRB), which comprises loading CeO2 particles on metal organic framework material (MOFs) with cobalt or copper as metal sites, and then modifying the fluorescence dye FMN-Na through electrostatic adsorption and precipitation reaction to obtain the enhanced fluorescence probe (MOFs@CeO2@FMN-Na). The degree of fluorescence enhancement can be changed by adjusting the loading of MOFs and cerium dioxide, so as to realize the enhanced fluorescence probe for monitoring sulfur ions and SRB. The method can include the following steps:

[0043] (1) Injecting the dispersion liquid of metal organic framework material (MOFs) with cobalt or copper as metal sites into a cerium source solution, adding a complexing precipitant, and then reacting at a certain temperature. Then, the product is separated and washed to obtain the metal organic framework (MOFs) loaded with cerium dioxide particles (MOFs@CeO2).

[0044] (2) Adding the MOFs@CeO2 obtained in step (1) to riboflavin monophosphate sodium (FMN-Na), and stirring at room temperature overnight to obtain the enhanced fluorescence probe (MOFs@CeO2@FMN-Na).

[0045] In some embodiments, the preparation of the metal organic framework material (MOFs) is as follows: rapidly mixing a metal salt (cobalt salt or copper salt) solution and a ligand solution at a certain temperature (preferably 50-80°C), stirring for a certain time, and then separating and washing the product to obtain the corresponding metal organic framework material (MOFs).

[0046] As a further preferred embodiment of the present application, the metal salt is one of cobalt nitrate, copper nitrate, cobalt chloride, copper sulfate, and cobalt sulfate, and the molar ratio of the metal salt to the ligand is 5:1-1:5.

[0047] As a further preferred embodiment of the present application, the ligand is at least one of 2-methylimidazole, bipyridine, terephthalic acid, trimesic acid, and naphthalene acid.

[0048] Preferably, the ligand comprises at least one of amino terephthalic acid, hydroxy terephthalic acid, 2,6-bis(2-pyrazinyl)-4,4'-bipyridine.

[0049] As a further preferred embodiment of the present application, the solvent used for the ligand is ethanol, water, DMF, triethylamine or a mixed solution in any proportion.

[0050] As a further preferred embodiment of the present application, in step (1), the solvent of the MOFs dispersion liquid is one of water, ethanol, DMF or a mixed solution in any proportion; the volume of the dispersion liquid is 0.5-3.5 mL.

[0051] As a further preferred embodiment of the present application, in step (1), the cerium source is one of cerium nitrate and cerium sulfate, and the concentration of the cerium nitrate is 1-8 g / L.

[0052] As a further preferred embodiment of the present application, in step (1), the complexing precipitant is one of arginine, citric acid, sodium hydroxide and ammonia water.

[0053] As a further preferred embodiment of the present application, in step (1), the molar ratio of cerium nitrate to the complexing precipitant is 2.5:1-1:2.5.

[0054] As a further preferred embodiment of the present application, in step (1), the temperature of the reaction is 75-90℃, and the reaction time is 2.5-4 h.

[0055] As a further preferred embodiment of the present application, in step (2), the concentration of the sodium riboflavin monophosphate is 1-3 mM.

[0056] According to another aspect of the present application, the present application provides the use of the fluorescence-enhanced probe prepared by the above preparation method for detecting sulfur ions or in detecting sulfate-reducing bacteria (SRB).

[0057] In some embodiments, the use is specifically:

[0058] (1) Prepare a 100 mM Na2S solution, dilute the fluorescence-enhanced probe by 10000 times, then add different volumes of the Na2S solution, shake well, and perform fluorescence detection after 2-4 min, with an excitation wavelength of 350 nm, a scanning speed of 600-2000 nm / min, and a slit width of 5 nm, and record the emission spectrum of 370-800 nm;

[0059] (2) Establish a relationship curve between the fluorescence emission intensity F533 and S 2- (the relationship curve between the fluorescence intensity at the peak and S 2- );

[0060] (3) Take 30 μL of the test solution to perform the operation process described in step (1);

[0061] (4) Obtain the S of the test solution according to the S 2- concentration relationship curve of the F533 obtained in step (2). 2-

[0062] In some embodiments, the application is specifically:

[0063] (1) Prepare a 100 mM Na2S solution, dilute the prepared double-quenching fluorescent probe by 10000 times (the ligand in the metal-organic framework material is a luminescent ligand, such as at least one of amino terephthalic acid, hydroxy terephthalic acid, and 2,6-bis(2-pyrazinyl)-4,4'-bipyridine), then add different volumes of the Na2S solution, shake well, and perform fluorescence detection after 2-4 min, the excitation wavelength is 350 nm, the sweep speed is 600-2000 nm / min, the slit width is 5 nm, and the emission spectrum of 370-800 nm is recorded;

[0064] (2) Establish the relationship curve between the fluorescence emission intensity ratio F531 / F413 (the fluorescence intensity ratio at two peak values and S 2- ) and S 2- ;

[0065] (3) Take 30 μL of the test solution to perform the operation process described in step (1);

[0066] (4) Obtain the S of the test solution according to the S 2- relationship curve of the fluorescence emission intensity ratio F531 / F413 obtained in step (2). 2-

[0067] In some embodiments, the application is specifically:

[0068] (1) Filter the SRB bacterial solution cultured for one week with a filter membrane, dilute the prepared enhanced fluorescent probe by 10000 times, then add different volumes of the treated SRB bacterial solution, shake well, and perform fluorescence detection after 2-4 min, the excitation wavelength is 350 nm, the sweep speed is 600-2000 nm / min, the slit width is 5 nm, and the emission spectrum of 370-800 nm is recorded;

[0069] (2) Establish the relationship curve between the fluorescence emission intensity F533 and the concentration of the SRB bacterial solution;

[0070] (3) Take 30 μL of the test bacterial solution to perform the operation process described in step (1);

[0071] ​​(4) According to the concentration relationship curve of the SRB bacteria liquid obtained from the fluorescence emission intensity F533 of step (2), the SRB bacteria liquid concentration value of the solution to be measured is obtained.

[0072] In some embodiments, the application is specifically:

[0073] (1) The SRB bacteria liquid cultured for one week is filtered with a filter membrane, and the prepared enhanced fluorescence probe is diluted by 10000 times, then different volumes of treated SRB bacteria liquid are added, shaken, and fluorescence detection is performed after 2-4 min, the excitation wavelength is 350 nm, the scanning speed is 600-2000 nm / min, the slit width is 5 nm, and the emission spectrum of 370-800 nm is recorded;

[0074] (2) The relationship curve between the fluorescence emission intensity ratio F531 / F413 (the fluorescence intensity ratio at two peak values and S 2- ) and the concentration of the SRB bacteria liquid is established;

[0075] (3) 30 μL of the bacteria liquid to be measured is taken to perform the operation process described in step (1);

[0076] (4) According to the relationship curve between the fluorescence emission intensity ratio F531 / F413 (the fluorescence intensity ratio at two peak values and S 2- ) and the concentration of the SRB bacteria liquid, the concentration of the bacteria liquid to be measured is obtained. The following is a specific embodiment:

[0077] Example 1

[0078] Synthesis of fluorescence probe MOFs@CeO2@FMN-Na:

[0079] The cobalt nitrate solution and the dimethyl imidazole solution (1:1) are rapidly mixed at 50°C, the product is separated and washed after stirring for 10 min to obtain the corresponding metal organic framework Co-MOFs; 1 mL of Co-MOFs dispersion is injected into the cerium nitrate solution, and after adding sodium hydroxide, it is reacted at 85°C, then the product is separated and washed to obtain the corresponding metal organic framework Co-MOFs@CeO2 loaded with cerium dioxide particles. After dispersing with water, riboflavin monophosphate sodium FMN-Na is added, and the enhanced fluorescence probe MOFs@CeO2@FMN-Na is obtained after stirring at room temperature overnight.

[0080] Fluorescence response of fluorescence probe MOFs@CeO2@FMN-Na to different concentrations of S 2-

[0081] ​A 100 mM Na2S solution was prepared, the enhanced fluorescent probe was diluted 10000 times, then different volumes of Na2S solution were added, shaken, and fluorescence detection was performed after 2-4 min. The excitation wavelength was 350 nm, the scanning speed was 2000 nm / min, the slit width was 5 nm, and the emission spectrum of 370-800 nm was recorded. As shown in FIG. 1, the arrow direction in the figure is S 2- The concentration increased in the direction. It was further found that F533 had a good linear relationship with S 2- in the concentration range of 0-150 μM and 150-270 μM, respectively: F533 = -4356.14 *[S 2- ]+5.6E 6 (R 2 =0.95) and F533 = -16542.80 *[S 2- ]+7.39E 6 (R 2 =0.99), as shown in FIG. 2. Finally, the S 2- detection limit was 18.42 μM, and the highest detection range was 270 μM. Therefore, the probe can be used for quantitative detection of S 2- in a wide linear range.

[0082] Example 2

[0083] The selectivity and interference of the fluorescent probe MOFs@CeO2@FMN-Na prepared in Example 1 to different anions were tested:

[0084] In order to exclude the influence of other anions that may exist in the aqueous phase on the detection of S 2- , common anions (H2PO4 - , SCN - , Cl - , C2O4 2- , SO3 2- , S2O3 2- , S2O8 2- , S 2- ) with a concentration of 100 mM were prepared for use. The enhanced fluorescent probe was diluted 10000 times, 4.5 μL of 10 mM of other seven kinds of anions except S 2- was added, shaken, and fluorescence detection was performed after 2-4 min. The excitation wavelength was 350 nm, the scanning speed was 2000 nm / min, the slit width was 5 nm, and the emission spectrum of 370-800 nm was recorded. Then, 4.5 μL of 100 mM S 2- was added to the above solution, shaken, and fluorescence detection was performed after 5 min.

[0085] As shown in FIG. 3, only when S 2-The fluorescence emission peak at 533 nm changed significantly. As shown in Figure 4, when these interfering substances coexist with S 2- 2- The relative fluorescence intensity change of the enhanced fluorescence probe is the largest. These results show that the MOFs@CeO2@FMN-Na has good specificity for S 2-

[0086] Example 3

[0087] The fluorescence response of the fluorescence probe MOFs@CeO2@FMN-Na prepared in Example 1 to different concentrations of SRB bacterial solution was studied:

[0088] After culturing SRB for one week, the bacterial solution was filtered to obtain the SRB metabolic bacterial solution; the enhanced fluorescence probe was diluted 10,000 times, then the SRB metabolic bacterial solution was added, shaken, and after 2-4 min, fluorescence detection was performed with an excitation wavelength of 350 nm, a scanning speed of 2000 nm / min, and a slit width of 5 nm. The recorded emission spectrum of 370-800 nm is shown in Figure 5, and the arrow direction in the figure is the direction of increasing concentration of the SRB metabolic bacterial solution. It was further found that F533 had a good linear relationship when the concentration of the SRB metabolic bacterial solution was 0-5.9*10 4 cells / mL: F533=-11.69*[C SRB ]+1.18E 6 (R 2 =0.99), as shown in Figure 6. Finally, the detection limit of the SRB metabolic bacterial solution was calculated to be 840 cells / mL by 3N / S. Therefore, the probe can be used for quantitative detection of the concentration of SRB.

[0089] Example 4

[0090] In order to realize signal correction, a dual-quenching fluorescence probe MOFs@CeO2@FMN-Na was also prepared, and the synthesis process was as follows:

[0091] The cobalt nitrate solution, dimethyl imidazole, and amino terephthalic acid solution (1:1:1) were mixed at 65°C and stirred for 12 h. The product was separated and washed to obtain the corresponding metal organic framework Co-MOFs. The Co-MOFs dispersion solution 1 mL was injected into the cerium nitrate solution, and after adding sodium hydroxide, it was reacted at 80°C. Then the product was separated and washed to obtain the corresponding metal organic framework Co-MOFs loaded with cerium dioxide particles. After dispersing with water, riboflavin monophosphate sodium FMN-Na was added, and after stirring at room temperature overnight, the enhanced fluorescence probe MOFs@CeO2@FMN-Na was obtained.

[0092] The fluorescence response of the dual-quenching fluorescence probe MOFs@CeO2@FMN-Na to different concentrations of S 2- ​​fluorescence response of the material Co-MOFs:

[0093] A 100 mM Na2S solution was prepared, and the enhanced fluorescence probe was diluted 10000 times, then the Na2S solution was added, shaken, and fluorescence detection was performed after 2-4 min. The excitation wavelength was 350 nm, the scanning speed was 2000 nm / min, the slit width was 5 nm, and the emission spectrum of 370-800 nm was recorded as shown in Figure 9. There was almost no fluorescence emission. 2- As the concentration of S 2- increased, the fluorescence intensity of MOFs@CeO2@FMN-Na in the system gradually weakened at the emission wavelengths of 413 nm and 531 nm. When the concentration of S 2- reached 12.17 mM, the fluorescence quenching rate exceeded 90%. Further found that F531 / F413 had a good linear relationship when the concentration of S 2- was 150-720 μM and 720-1230 μM, respectively: F531 / F413=-0.011*[S 2- ]+18.65 (R 2 =0.99), F531 / F413=-0.014*[S 2- ]+20.67 (R 2 =0.99), as shown in Figure 8. Therefore, the probe can be used for quantitative detection of S 2- concentration.

[0094] Comparative Example 1

[0095] The cobalt nitrate solution and the dimethyl imidazole solution (1:1) were rapidly mixed at 50°C, the product was separated and washed after stirring for 10 min to obtain the corresponding metal organic framework material Co-MOFs.

[0096] Test the fluorescence response of the material Co-MOFs:

[0097] The obtained Co-MOFs were diluted 10000 times for fluorescence detection. The excitation wavelength was 350 nm, the scanning speed was 2000 nm / min, the slit width was 5 nm, and the emission spectrum of 370-800 nm was recorded as shown in Figure 9. There was almost no fluorescence emission.

[0098] Comparative Example 2

[0099] The cobalt nitrate solution and the dimethyl imidazole solution (1:1) were rapidly mixed at 50°C, the product was separated and washed after stirring for 10 min to obtain the corresponding metal organic framework material Co-MOFs. 1 mL of Co-MOFs dispersion was injected into a cerium nitrate solution, and after adding sodium hydroxide, it was reacted at 85°C. Then the product was separated and washed to obtain the corresponding metal organic framework Co-MOFs@CeO2 loaded with cerium dioxide particles.

[0100] The fluorescence response of the test material Co-MOFs@CeO2 was tested.

[0101] The obtained Co-MOFs@CeO2 was diluted 10,000 times for fluorescence detection, the excitation wavelength was 350 nm, the scanning speed was 2,000 nm / min, the slit width was 5 nm, and the emission spectrum of 370-800 nm was recorded as shown in FIG. 9, and almost no fluorescence emission was observed.

[0102] Comparative Example 3

[0103] After adding sodium hydroxide to the cerium nitrate solution and reacting at 85°C, the product was separated and washed to obtain the corresponding cerium dioxide particles CeO2; after dispersing in water and adding riboflavin monophosphate sodium FMN-Na, the material CeO2@FMN-Na was obtained after stirring overnight at room temperature.

[0104] The fluorescence response of the test material CeO2@FMN-Na was tested.

[0105] The obtained CeO2@FMN-Na was diluted 10,000 times for fluorescence detection, the excitation wavelength was 350 nm, the scanning speed was 2,000 nm / min, the slit width was 5 nm, and the emission spectrum of 370-800 nm was recorded as shown in FIG. 9.

[0106] Comparative Example 4

[0107] Riboflavin monophosphate sodium FMN-Na was added to water, and the material FMN-Na was obtained after stirring overnight at room temperature.

[0108] The fluorescence response of the test material FMN-Na was tested.

[0109] The obtained FMN-Na was diluted 10,000 times for fluorescence detection, the excitation wavelength was 350 nm, the scanning speed was 2,000 nm / min, the slit width was 5 nm, and the emission spectrum of 370-800 nm was recorded as shown in FIG. 9, and the fluorescence emission was weak.

[0110] The fluorescence probes prepared in Comparative Examples 1, 2 and 4 were all lower than the fluorescence intensity of the fluorescence probe prepared in Example 1. Although Comparative Example 3 was higher than Example 1, since there was no substance (metallic cobalt or copper) capable of recognizing S in the material, it could not be used as a fluorescence material for detecting S. 2- 2- The fluorescence probes prepared in Comparative Examples 1, 2 and 4 were all lower than the fluorescence intensity of the fluorescence probe prepared in Example 1. Although Comparative Example 3 was higher than Example 1, since there was no substance (metallic cobalt or copper) capable of recognizing S in the material, it could not be used as a fluorescence material for detecting S.

[0111] It is easily understood by those skilled in the art that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for preparing a CeO2-based enhanced fluorescent probe, characterized in that, The method comprises the following steps: (1) injecting a dispersion liquid of an organic framework material into a cerium source solution, then adding a complexing precipitant, and then heating to separate the generated precipitate to obtain a metal organic framework loaded with cerium dioxide particles; wherein the organic framework material is an organic framework material containing metal cobalt elements or an organic framework material containing metal copper elements; (2) adding a sodium riboflavin monophosphate solution to the metal organic framework loaded with cerium dioxide particles obtained in step (1), and connecting the sodium riboflavin monophosphate to the cerium dioxide particles to obtain a CeO2-based enhanced fluorescence probe.

2. The method for preparing Ce02-based enhanced fluorescent probe according to claim 1, characterized in that, The ligand of the organic framework material is at least one of dimethyl imidazole, bipyridine, terephthalic acid, trimesic acid, and naphthalene acid.

3. The method for preparing a Ce02-based enhanced fluorescent probe according to claim 1 or 2, characterized in that, The ligand of the organic framework material includes at least one of amino terephthalic acid, hydroxy terephthalic acid, and 2,6-bis(2-pyrazinyl)-4,4'-bipyridine.

4. The CeO2-based enhanced fluorescence probe prepared by the method of any one of claims 1-3.

5. The use of the CeO2-based enhanced fluorescence probe of claim 4 for detecting sulfur ions.

6. The use according to claim 5, wherein the compound is ###0002### The use specifically comprises the following steps: (1) adding the CeO2-based enhanced fluorescence probe to a salt solution containing sulfur ions with gradient concentrations, then performing fluorescence detection, and establishing a relationship curve of the fluorescence intensity at the peak value and the sulfur ion concentration; (2) adding the CeO2-based enhanced fluorescence probe to a to-be-detected solution, and performing fluorescence detection under the same excitation wavelength as the fluorescence detection in step (1), and then obtaining the concentration of sulfur ions in the to-be-detected solution according to the relationship curve in step (1).

7. The use according to claim 5, wherein the compound is ###0002### The use specifically comprises the following steps: (1) adding the CeO2-based enhanced fluorescence probe to a salt solution containing sulfur ions with gradient concentrations, then performing fluorescence detection, and establishing a relationship curve of the ratio of the fluorescence intensity at the two peak values and the sulfur ion concentration; (2) adding the CeO2-based enhanced fluorescence probe to a to-be-detected solution, and performing fluorescence detection under the same excitation wavelength as the fluorescence detection in step (1), and then obtaining the concentration of sulfur ions in the to-be-detected solution according to the relationship curve in step (1).

8. The use of the CeO2-based enhanced fluorescence probe of claim 4 for detecting the concentration of sulfate-reducing bacteria.

9. Use according to claim 8, wherein the compound is ###0002### The use specifically comprises the following steps: (1) adding the CeO2-based enhanced fluorescence probe to a bacteria solution of sulfate-reducing bacteria with gradient concentrations, then performing fluorescence detection, and establishing a relationship curve of the fluorescence intensity at the peak value and the concentration of sulfate-reducing bacteria; (2) adding the CeO2-based enhanced fluorescence probe to a to-be-detected bacteria solution, and performing fluorescence detection under the same excitation wavelength as the fluorescence detection in step (1), and then obtaining the concentration of sulfate-reducing bacteria in the to-be-detected bacteria solution according to the relationship curve in step (1).

10. The use according to claim 8, wherein the compound is ###0002### The use specifically comprises the following steps: (1) adding the CeO2-based enhanced fluorescent probe into the bacterial solution of sulfate-reducing bacteria with gradient concentration, and then performing fluorescence detection to establish a relationship curve between the ratio of fluorescence intensity at two peak values and the concentration of sulfate-reducing bacteria; (2) adding the CeO2-based enhanced fluorescent probe into the bacterial solution to be detected, and performing fluorescence detection under the same excitation wavelength as that in step (1), and then obtaining the concentration of sulfate-reducing bacteria in the bacterial solution to be detected according to the relationship curve in step (1).

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