A MoS2 / Europium Composite Fluorescent Probe and Its Preparation Method and Application

Abstract

A molybdenum disulfide / europium composite fluorescent probe and its preparation method and application belong to the field of rare earth fluorescent materials and the field of analytical detection of oxytetracycline. The specific scheme is as follows: The molybdenum disulfide / europium composite fluorescent probe is a composite of molybdenum disulfide nanosheets doped with europium. The composite shows, in terms of microstructure, that Eu2O3 is uniformly coated on flaky MoS2 nanosheets. The preparation method includes the following steps: Step 1, adding an aqueous L-cysteine solution to a Na2MoO4 solution and ultrasonically dispersing it uniformly to obtain liquid A; Step 2, dispersing Eu2O3 in water to obtain liquid B; Step 3, mixing liquids A and B, performing a hydrothermal reaction, cooling, and centrifuging to obtain the supernatant, which is the molybdenum disulfide / europium composite fluorescent probe. The probe has the advantages of simple preparation, good selectivity, low detection limit, and wide linear range, and can effectively overcome the interference of external environmental factors on the detection results.

Description

Technical Field

[0001] The present invention belongs to the field of rare earth fluorescent materials and the field of analysis and detection of oxytetracycline, and relates to a molybdenum disulfide / europium composite fluorescent probe and its preparation method and application, and specifically relates to a rare earth europium doped molybdenum disulfide composite fluorescent probe and its preparation method and a method for quantitatively detecting oxytetracycline in water using the probe. Background Art

[0002] Oxytetracycline is a broad-spectrum antibiotic widely used in the treatment and prevention of infectious diseases in animals. However, its long-term, excessive, and irrational use has led to its accumulation in food, posing a serious threat to human health. Because it is not fully absorbed by the human body, it seeps into water and soil in various forms and pathways, posing a threat to the ecological environment. Commonly used methods for oxytetracycline analysis include high-performance liquid chromatography, high-performance liquid chromatography-tandem mass spectrometry, and capillary electrophoresis. However, these techniques suffer from drawbacks such as cumbersome operation, high cost, and time consumption. Therefore, the search for simple and rapid detection methods is crucial. Fluorescence technology, with its high sensitivity, high specificity, and low cost, holds broad application prospects in pharmaceutical and clinical testing, environmental testing, and food testing. Currently, nanomaterials used as fluorescent probes for oxytetracycline detection include carbon quantum dots, functionalized metal-organic frameworks, semiconductor quantum dots, silver nanoclusters, and lanthanide-based rare earth materials.

[0003] Polymers containing Sm, Eu, Tb, and Dy are promising luminescent materials, especially those with red, green, and blue colors, which have attracted widespread attention. Oxytetracycline is a tetracycline drug with a β-diketone structure. Some studies have shown that the β-diketone structure can become Eu 3+ The ideal ligand of Eu 3+ The luminescence ability of the complex is weak and may be interfered by other ligands in the environment. Other nanomaterials need to be introduced to enhance its luminescence ability. Summary of the Invention

[0004] In order to solve the shortcomings of conventional detection technology such as high cost, complicated operation and expensive equipment, the present invention provides a molybdenum disulfide / europium composite fluorescent probe and its preparation method and application, which is specifically used for the efficient quantitative detection of oxytetracycline.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A molybdenum disulfide / europium composite fluorescent probe is a composite of molybdenum disulfide nanosheets doped with europium. The microstructure of the composite shows that Eu2O3 is uniformly coated on flaky MoS2 nanosheets.

[0007] A method for preparing the molybdenum disulfide / europium composite fluorescent probe comprises the following steps:

[0008] Step 1: Add the L-cysteine aqueous solution to the Na2MoO4 solution and disperse it evenly with ultrasonic waves to obtain solution A;

[0009] Step 2: Disperse Eu2O3 in water to obtain solution B;

[0010] Step 3: Mix liquid A and liquid B, and conduct a hydrothermal reaction. After cooling, centrifuge and obtain the supernatant, which is the molybdenum disulfide / europium composite fluorescent probe.

[0011] Furthermore, the concentration of the Na2MoO4 solution is 0.035-0.045 mol / L; the concentration of the L-cysteine aqueous solution is 0.075-0.085 mol / L; and the concentration of the Eu2O3 solution is 0.13-0.15 mol / L.

[0012] Furthermore, the volume ratio of the mixture of liquid A and liquid B is 90:1 to 75:1.

[0013] Furthermore, the temperature of the hydrothermal reaction is 180-220° C., and the duration is 33-39 hours.

[0014] An application of a molybdenum disulfide / europium composite fluorescent probe prepared by the preparation method, wherein the molybdenum disulfide / europium composite fluorescent probe is used for quantitative determination of oxytetracycline.

[0015] Furthermore, the sample to be tested was mixed with the diluted composite fluorescent probe solution, phosphate buffer was added, and the mixture was incubated at room temperature. The fluorescence intensity at 437 nm was measured at an excitation wavelength of 365 nm.

[0016] Furthermore, the dilution ratio of the composite fluorescent probe solution is 18 to 22 times; the volume of the phosphate buffer is 970 to 1030 μL; the pH of the phosphate buffer is 6.8 to 7.2; and the incubation time is 570 to 630 s.

[0017] Furthermore, the phosphate buffer solution is prepared by taking 0.675-0.685 g of potassium dihydrogen phosphate, adding 29.0-29.2 mL of 0.095-0.105 mol / L sodium hydroxide solution, and diluting the mixture with water to 99-101 mL.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] Lanthanide fluorescent probes have a unique outer electron layer structure of lanthanide ions, with advantages such as large Stokes shift, sharp emission spectrum, long fluorescence lifetime, and high chemical stability. They can effectively eliminate background fluorescence and light scattering of samples in harsh environments. Therefore, they have received widespread attention and application in the field of analysis. The principle of tunable luminescence design of lanthanide fluorescent probes is to rely on the chelation of lanthanide ions and ligands to form an "antenna effect" to emit fluorescence. Oxytetracycline is a polycyclic compound containing a β-diketone structure. The β-diketone structure can be used as a sensitizer and reacts with Eu 3+ Cooperate to form an "antenna effect". 3+ The luminescence ability of the coordination compound is weak, so Eu 3+ It is unsaturated and easily interfered by other ligands in the environment, resulting in poor detection accuracy. Therefore, other nanomaterials are needed to assist Eu 3+ Coordination compounds achieve enhanced luminescence. Molybdenum disulfide and Eu 3+ Fluorescence resonance energy transfer occurs between the two molecules, with the Eu-oxytetracycline coordination compound receiving energy from molybdenum disulfide via the transmission channel constructed by the oxytetracycline molecule, thereby enhancing the characteristic emission peak. Molybdenum disulfide acts as both an indicator and an enhancer. The molybdenum disulfide / europium composite fluorescent probe prepared by the present invention has high sensitivity and selectivity for the detection of oxytetracycline. The probe exhibits good linearity within the linear range of 0 to 50 μM oxytetracycline, with a minimum detection limit of 20 nM. The present invention has also successfully applied the probe to the detection of oxytetracycline in water bodies and actual samples. The probe has the advantages of simple preparation, good selectivity, low detection limit, and a wide linear range, and can effectively overcome the interference of external environmental factors on the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the infrared spectrum of the composite fluorescent probe prepared in Example 1 of the present invention;

[0021] Figure 2 The excitation and emission spectra of the composite fluorescent probe prepared in Example 1 of the present invention;

[0022] Figure 3 This is the X-ray photoelectron spectrum of the composite fluorescent probe prepared in Example 1 of the present invention;

[0023] Figure 4 (a) is a scanning electron microscope image of MoS2 prepared in Example 1 of the present invention; (b) is a scanning electron microscope image of the composite fluorescent probe prepared in Example 1 of the present invention; (c) is an EDS spectrum of the composite fluorescent probe prepared in Example 1 of the present invention;

[0024] Figure 5(a) is a transmission electron micrograph of MoS2 prepared in Example 1 of the present invention; (b) is a high-resolution transmission electron micrograph of the composite fluorescent probe prepared in Example 1;

[0025] Figure 6 (a) is the fluorescence spectrum of oxytetracycline at different concentrations added to the composite fluorescent probe solution prepared in Example 2 of the present invention; (b) is the linear relationship diagram between the (I0-I) / I0 value and the oxytetracycline concentration; (c) is the fluorescence response of the (I0-I) / I0 value to different ions; (d) is the fluorescence response of the (I0-I) / I0 value to different analogues; wherein OTC, CIP, CAP, IBU, DPA, and LPA represent oxytetracycline, ciprofloxacin, chloramphenicol, ibuprofen, D-penicillamine, and L-penicillamine, respectively. DETAILED DESCRIPTION

[0026] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Sodium molybdate and L-cysteine were purchased from MacLean Biotech. Europium oxide, oxytetracycline, ciprofloxacin, and other reagents were purchased from Aladdin Chemical Reagents. All chemicals and reagents were used directly without further purification. Ultrapurified water was used throughout this work and treated in the laboratory using water treatment equipment.

[0028] Example 1

[0029] A method for preparing a molybdenum disulfide / europium composite fluorescent probe comprises the following steps:

[0030] Step 1: Using Na2MoO4 as a molybdenum source, ultrasonically disperse it in water to obtain a Na2MoO4 solution; using an aqueous solution of L-cysteine as a sulfur source, add it to the Na2MoO4 solution and continue ultrasonicating to obtain Solution A;

[0031] Step 2: Disperse Eu2O3 in water as liquid B;

[0032] Step 3: Take appropriate amounts of solution A and solution B, mix them, hydrothermally react at 200° C., and then cool and centrifuge to obtain the supernatant, which is the molybdenum disulfide / europium composite fluorescent probe.

[0033] In step 1, 0.25 g of Na2MoO4·2H2O was dissolved in 25 mL of water and ultrasonically vibrated for 5 minutes to obtain a Na2MoO4 solution; 0.5 g of L-cysteine was dispersed in 50 mL of water and then added to the Na2MoO4 solution. After mixing, the mixture was ultrasonically vibrated for 10 minutes to obtain solution A.

[0034] In step 2, 0.5 g of Eu2O3 was slowly added to 10 mL of water and stirred continuously for 30 min to fully disperse it. The solution was stirred for 30 min to uniformly dissolve it to obtain solution B.

[0035] In step 3, accurately pipette 900 μL of the B solution into solution A, mix well, transfer to a 100 mL reactor, incubate at 200°C for 36 hours, cool naturally, and centrifuge at 12,000 rpm for 10 minutes. The supernatant obtained is the molybdenum disulfide / europium composite fluorescent probe and is stored at 4°C.

[0036] Figure 1 is an infrared spectrum of the composite fluorescent probe prepared in Example 1 of the present invention; Figure 2 : is the excitation and emission spectrum of the composite fluorescent probe prepared in Example 1 of the present invention. Figure 1 It can be seen that the OH vibration and NH stretching vibration peaks are at 3420 cm -1 The CH vibration peak is at 2959cm -1 , SH symmetric stretching peak at 2108 cm -1 The stretching vibration peak of NH is at 1637 cm -1 The asymmetric stretching vibrations of C-NH are at 1350 and 1140 cm -1 , at 619cm -1 The vibration peak at is the characteristic absorption peak of Mo-S. These results indicate that the hydroxyl and amino groups are most likely located on the surface of the composite. Figure 2 As can be seen from the figure, as a new type of fluorescent sensing material, its most important feature is its good optical properties. Under ultraviolet (5W) and 365nm light, the synthesized composite fluorescent probe shows blue light and reddish brown in visible light. Figure 2 As shown, the fluorescence spectrum of the composite fluorescent probe has a maximum emission wavelength at 437 nm under an excitation wavelength of 365 nm.

[0037] like Figure 3 As shown, Figure 3 This is the X-ray photoelectron spectrum of the composite fluorescent probe prepared in Example 1 of the present invention. Figure 3 As can be seen in (a), the composite fluorescent probe is mainly composed of Eu, O, S, Mo and other elements. Figure 3 As shown in (b), 3d in Mo3d5 / 2 The corresponding binding energy is 227.68 eV, 3d 3 / 2 The corresponding binding energies are 231.88 and 235.03 eV, respectively, indicating that Mo is Mo 4+ The form exists in the composite fluorescent probe. Figure 3 As shown in (c), 2p in S2p 3 / 2 and 2p 1 / 2 The binding energies of the two molecules are 162.43 and 168.57 eV, respectively, indicating that the S element in L-cysteine is introduced into the complex. The resolved spectra of Mo 3d and S2p confirm the presence of molybdenum disulfide in the composite fluorescent probe. Figure 3 (d) In the high-resolution spectrum of Eu 3d, 3d 3 / 2 and 3D 5 / 2 The corresponding binding energies are 1163.72 and 1134.16 eV, respectively, indicating that Eu is 3+ The presence of in Eu2O3 further proves the existence of Eu2O3.

[0038] like Figure 4 As shown, Figure 4 (a) is a scanning electron microscopy image of MoS2 prepared in Example 1 of the present invention; Figure 4 (b) is a scanning electron microscopy image of the composite fluorescent probe prepared in Example 1 of the present invention; Figure 4 (c) is the EDS spectrum of the composite fluorescent probe prepared in Example 1 of the present invention. Figure 4 As can be seen in (a), MoS2 is in uniform flake form and aggregates together. Figure 4 As can be seen in (b), Eu2O3 is evenly coated on the MoS2 nanosheets. Figure 4 It can be seen from (c) that Mo, S, O, and Eu elements exist in the composite fluorescent probe, which is consistent with the XPS analysis results. The above results further prove the successful synthesis of the composite fluorescent probe.

[0039] like Figure 5 As shown, Figure 5 (a) is a transmission electron micrograph of MoS2 prepared in Example 1 of the present invention; Figure 5 (b) is a high-resolution transmission electron microscopy image of the composite fluorescent probe prepared in Example 1 of the present invention. Figure 5 As shown in (a), there is a large amount of solid solution on the surface of MoS2 nanosheets, which is consistent with the analysis results of scanning electron microscopy. Figure 5 (b) shows the presence of Eu2O3, where the lattice fringes of Eu2O3 can be clearly observed. The above results prove that the MoS2 / Eu2O3 nanocomposite fluorescent probe was successfully synthesized.

[0040] Example 2

[0041] An application of the molybdenum disulfide / europium composite fluorescent probe prepared by the preparation method described in an embodiment comprises the following steps:

[0042] Step 1: Add 0-50 μM oxytetracycline to the 20-fold diluted composite fluorescent probe solution prepared in Example 1, and add 1 mL of phosphate buffer (pH 7.0). Add ultrapure water to a final volume of 5 mL and incubate at room temperature for 10 minutes.

[0043] Step 2: Measure the fluorescence intensity at 437 nm at an excitation wavelength of 365 nm.

[0044] like Figure 6 As shown, Figure 6 (a) is the fluorescence spectrum of the composite fluorescent probe solution prepared in Example 2 of the present invention with different concentrations of oxytetracycline added; Figure 6 (b) is a linear relationship diagram of the (I0-I) / I0 value and the oxytetracycline concentration, where I0 and I represent the fluorescence intensity of the probe solution without and with oxytetracycline, respectively; Figure 6 (c) is the fluorescence response of (I0-I) / I0 value to different ions; Figure 6 (d) is the fluorescence response of (I0-I) / I0 to different analogs. Figure 6 As shown in (a), within the range of 0 to 50 μM, as the concentration gradually increases, the fluorescence intensity of the composite fluorescent probe decreases. Figure 6 As shown in (b), under the optimal experimental conditions, the relative fluorescence intensity [(I0-I) / I0] showed a good linear relationship with the oxytetracycline concentration in the range of 0 to 50 μM, and the linear equation was [(I0-I) / I0] = 0.0149[x]-0.0006(r 2 =0.9974, n=10, n means 10 data were tested). The fluorescence intensity of 1 μM probe solution was tested, and the standard deviation (SD) was calculated based on the test results. According to the standard deviation formula, SD=0.01%, and the detection limit formula can be used to calculate that the detection limit of the probe is 20 nM. Figure 6 As shown in (c) and (d), 1 mM of some common ions and their analogs (Na + , K + , Ca 2+ Mg 2+ 、Zn 2+ 、Co 2+ 、Cd 2+ , Pb 2+ NH4 + 、F - Br - 、Cl - 、CO3 2- 、SO3 2-、SO4 2- 、NO3 - PO4 3- , CIP, CAP, IBU, DPA and LPA) responded weakly to the probe, but had almost no effect on the value of [(I0-I) / I0], while oxytetracycline responded significantly to the probe solution. The results showed that the probe can selectively detect oxytetracycline.

[0045] Example 3

[0046] In this example, the content of oxytetracycline in local tap water and Songhua River water was determined. The water sample was centrifuged at 12000rpm for 10 minutes to remove suspended particles. Then 0.1mL of river water diluted 30 times was added to the composite fluorescent probe solution prepared in Example 1 diluted 20 times, and 1.0mL of phosphate buffer (pH 7.0) was added. After incubation at room temperature for 10 minutes, the fluorescence intensity at 437nm was measured at an excitation wavelength of 365nm. Table 1 shows the results of the determination of oxytetracycline content in local tap water and Songhua River water in this example. As shown in Table 1, the recovery rates in tap water and Songhua River water were 92.1% to 98.9% and 97.2% to 98.5% respectively, with relative standard deviations of 1.05% to 1.26% and 1.09% to 1.31%, respectively. The recovery rate effect was ideal.

[0047] Example 4

[0048] This embodiment measures the content of oxytetracycline in three oxytetracycline preparations (injection, powder and veterinary medicine). A certain amount of preparation is appropriately diluted or dissolved to obtain an oxytetracycline solution to be tested of a suitable concentration. Then an appropriate amount of the solution to be tested is added to the composite fluorescent probe solution prepared in Example 1 diluted 20 times, and 1.0 mL of phosphate buffer (pH 7.0) is added. After incubation at room temperature for 10 minutes, the fluorescence intensity at 437 nm is measured at an excitation wavelength of 365 nm. Table 2 is the detection of oxytetracycline concentration in oxytetracycline injection, powder and veterinary medicine by the composite fluorescent probe. As shown in Table 2, the measured values are consistent with the true values of the three reference values, with a relative standard deviation of 98.7% to 99.7%, which is ideal, proving that this method can be used for estimating the concentration of oxytetracycline in actual samples. These results fully demonstrate the feasibility and reliability of this method in actual detection.

[0049] Table 1

[0050]

[0051] Table 2

[0052]

[0053] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a molybdenum disulfide / europium composite fluorescent probe, characterized in that: The molybdenum disulfide / europium composite fluorescent probe is a composite of molybdenum disulfide nanosheets doped with europium, and the microstructure of the composite shows that Eu2O3 is uniformly coated on the flaky MoS2 nanosheets; The preparation method comprises the following steps: Step 1: Add the L-cysteine aqueous solution to the Na2MoO4 solution and disperse it evenly with ultrasonic waves to obtain solution A; Step 2: Disperse Eu2O3 in water to obtain solution B; Step three: mixing solution A and solution B, and performing a hydrothermal reaction. After cooling and centrifugation, the supernatant obtained is the molybdenum disulfide / europium composite fluorescent probe; The concentration of the Na2MoO4 solution is 0.035-0.045 mol / L; the concentration of the L-cysteine aqueous solution is 0.075-0.085 mol / L; and the concentration of the Eu2O3 solution is 0.13-0.15 mol / L.

2. The method for preparing a molybdenum disulfide / europium composite fluorescent probe according to claim 1, wherein: The volume ratio of the mixture of liquid A and liquid B is 90:1 to 75:

1.

3. The method for preparing a molybdenum disulfide / europium composite fluorescent probe according to claim 1, wherein: The temperature of the hydrothermal reaction is 180-220° C., and the duration is 33-39 hours.

4. An application of a molybdenum disulfide / europium composite fluorescent probe prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The molybdenum disulfide / europium composite fluorescent probe is used for quantitative determination of oxytetracycline.

5. The use according to claim 4, characterized in that: The sample to be tested was mixed with the diluted composite fluorescent probe solution, phosphate buffer was added, and the mixture was incubated at room temperature. The fluorescence intensity at 437 nm was measured at an excitation wavelength of 365 nm.

6. The use according to claim 5, characterized in that: The dilution ratio of the composite fluorescent probe solution is 18 to 22 times; the volume of the phosphate buffer is 970 to 1030 μL; the pH of the phosphate buffer is 6.8 to 7.2; and the incubation time is 570 to 630 seconds.

7. The use according to claim 5 or 6, characterized in that: The preparation method of the phosphate buffer solution is as follows: 0.675-0.685 g of potassium dihydrogen phosphate is added to 29.0-29.2 mL of 0.095-0.105 mol / L sodium hydroxide solution, and the mixture is diluted with water to 99-101 mL.

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