Double-response visual fluorescent probe as well as construction method and application thereof

Abstract

The invention relates to a double-response visual fluorescent probe as well as a construction method and application thereof. According to the present invention, carboxyl activation is performed on rhodamine B, Eu < 3 + > fixes the carboxyl of TAT through bridging and chelation, the Rh B can be combined with EuTAT through the amide reaction due to the steric hindrance effect of the asymmetric amino group to obtain the spirolactam ring so as to obtain the switch fluorescent probe controlled by the spirolactam ring, and the synthesized EuTAT-Rh B compound has characteristics of pH responsiveness and low fluorescence background, according to pH-dependent morphological structure conversion and fluorescence signal conversion caused by conjugate system change induced by vanadate coordination, visual vanadate solution monitoring and synchronous morphological discrimination can be realized in ultraviolet and fluorescence dual channels, and a convenient, simplified and highly sensitive visual platform is provided for visual analysis of vanadate.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of micro-polluted water detection, and particularly relates to a dual-response visual fluorescent probe and a construction method and application thereof. BACKGROUND

[0002] Although vanadium plays an irreplaceable role in human production and life, research has found that excessive intake of vanadium by humans or animals can easily cause diseases such as throat pain, pulmonary emphysema, eye conjunctivitis, kidney damage, cardiovascular lesions, etc.; excessive vanadium in plant bodies will cause wilting, limit plant growth and reduce crop yield [7] The United Nations Environment Programme (UNEP) suggests that V be listed as a priority environmental pollutant, and the limit value specified in the drinking water standard of China is 50 μg / L. In addition, according to the Vanadium Industrial Pollutant Discharge Standard (2011) of the Ministry of Ecology and Environment of the People's Republic of China, the total vanadium discharge requirement is <2.0 mg / L for existing enterprises and <1.0 mg / L for newly built enterprises, and the special discharge limit value of water pollution shall not exceed 0.3 mg / L. In an aerobic water environment, vanadium mostly exists in the form of pentavalent V (V) which is the most soluble and biologically toxic, forming a negatively charged metal oxygen-containing anion, i.e. vanadate anion [8] Unlike metal cations that can be separated by precipitation or adsorption, vanadate cannot be effectively adsorbed by rocks and minerals that are also negatively charged or electrically neutral, and has higher solubility and environmental migration rate.

[0003] Vanadate is a transition metal oxoacid salt pollutant with toxicological effects. Due to its strong migration and non-degradability, it has become an important indicator for environmental detection.

[0004] Due to the rich polymeric properties, the detection of vanadate is focused on content analysis and form identification. However, current research tends to build a single concentration or form analysis platform, which has the problems of single detection function, complex instrument equipment and high cost, and it is difficult to quickly obtain the overall situation of vanadate. Therefore, it is of great significance to develop a simple and convenient multifunctional detection probe in practical applications. SUMMARY

[0005] In view of the above technical problems to be solved, the present application develops and constructs a multifunctional fluorescent sensor with different pH responses to different forms of polyvanadate under the background of different pH values of vanadate forms and valence states.

[0006] In a first aspect of the present application, a preparation method of a dual-response visual fluorescent probe is provided, comprising the following steps:

[0007] 1) Synthesis of carboxyl-activated Rhodamine B solution 1: Rhodamine B (Rh B) solid was dissolved in ultrapure water at room temperature and in the dark, under continuous stirring, N-hydroxysuccinimide (EDC) was first added, 10 min later, carbodiimide hydrochloride (NHS) was added, and after 20 min of continuous waiting, carboxyl-activated Rhodamine B solution 1 was obtained,

[0008] 2) Synthesis of precursor EuTAT solution 2: 2-amino terephthalic acid (TAT) and sodium bicarbonate were dissolved in ultrapure water, the reaction was allowed to stand until a clear brown solution was obtained, Eu3+ solution was added, and stirring was continued for 30 min to obtain precursor EuTAT solution 2;

[0009] 3) Synthesis of EuTAT@RhB fluorescent probe

[0010] The obtained precursor EuTAT solution 2 was added dropwise to Rhodamine B solution 1, and stirring was continued for 30 min to obtain mixture 3; then mixture 3 was transferred to a hydrothermal reactor, heated at 160°C for 10 h, then cooled to room temperature, and centrifuged to obtain the precipitated product, which was washed with a mixture of water and ethanol until the supernatant did not emit fluorescence under irradiation of a 254 nm ultraviolet lamp, and vacuum dried to obtain the product EuTAT@RhB.

[0011] The preparation method first activates the carboxyl group of Rhodamine B, and then Eu 3+ The carboxyl group of TAT is fixed by bridging and chelation. Due to the steric hindrance effect of the asymmetric amino group, Rh B can be combined with EuTAT through amide reaction (emitting blue fluorescence), and a spirolactam ring is obtained (no fluorescence), thereby reducing the background fluorescence of the system, and finally obtaining a "switch" fluorescent probe controlled by a spirolactam ring. In the probe, the introduction of the Rhodamine B spirolactam ring effectively limits the basic fluorescence signal, so that the signal of vanadate is amplified, and the obtained EuTAT@Rh B complex exhibits a fluorescence enhancement related to vanadate and has a low fluorescence background in a wide pH range.

[0012] Preferably, in step 1), the mass ratio of Rhodamine B: EDC: NHS is 0.04-0.05: 0.2-0.3: 0.15-0.25.

[0013] In the construction process of the EuTAT@Rh B fluorescent probe, Eu 3+ plays a role in fixing the carboxyl group on TAT, thereby controlling the Eu 3+ The amount of Eu 3+ added is the key to improving the synthesis efficiency. Preferably, the molar ratio of Eu 3+TAT: RhB = 2:3:1.

[0014] In a second aspect of the present application, the dual-response visual fluorescent probe EuTAT@RhB prepared by the preparation method is provided.

[0015] In a third aspect of the present application, the application of the dual-response visual fluorescent probe EuTAT@RhB in vanadate detection, especially in (VO3)n n- , VO4 -3 detection is provided.

[0016] In a fourth aspect of the present application, a vanadate detection method is provided, comprising the following steps:

[0017] S1: configuring the dual-response visual fluorescent probe EuTAT@RhB into a solution, and obtaining an EuTAT@RhB dispersion liquid by ultrasonic treatment;

[0018] S2: adding the EuTAT@RhB dispersion liquid into a water sample, ultrasonic treatment, and performing fluorescence detection.

[0019] Preferably, the pH of the water sample is 1-13. Different pH has different fluorescence intensity. When the pH is less than 3, the cyan fluorescence of the EuTAT@RhB solution is enhanced, and the fluorescence emission peak is between 405 and 460 nm. When the pH is 3-5, the fluorescence of the solution is weakened with the increase of the pH value, which is due to the acid-induced proton transfer process. When the pH is greater than 5, the fluorescence remains stable, which provides a stable contact platform for detecting vanadate. Between pH 10 and 12, the fluorescence is enhanced, and the emission peak is blue-shifted. Around pH 13, the fluorescence is quenched. When the pH is less than 2, vanadium mainly exists in the form of (VO3) n n- . After the pH is greater than 10, VO4 3- begins to appear and tends to be stable under strong alkaline conditions. Preferably, the pH is between 5 and 10.

[0020] Preferably, the ultrasonic dispersion time in the step S2 is greater than or equal to 60 min, so as to form a stable combination and maintain the fluorescence stability.

[0021] Preferably, the excitation wavelength of the fluorescence detection is 240-290 nm, such as 240 nm, 250 nm, 260 nm, 270 nm, 280 nm and 290 nm, etc. Further preferably, it is 260 nm.

[0022] The present application provides a "switch" fluorescent probe controlled by a spirolactam ring. The synthesized EuTAT@RhB complex has pH responsiveness and low fluorescence background. First, Eu 3+The carboxyl group of TAT is fixed by bridging and chelation. Then, due to the steric hindrance effect of the asymmetric amino group, RhB can be combined with EuTAT through an amide reaction (emitting blue fluorescence), and a spirolactam ring (no fluorescence) is obtained, thereby reducing the background fluorescence of the system. The introduction of the rhodamine B spirolactam ring effectively limits the basic fluorescence signal, and the signal of vanadate is amplified. The complex exhibits a fluorescence enhancement associated with vanadate in a wide pH range. In addition, at pH 1-13, EuTAT@RhB exhibits a structure-dependent fluorescence change from T2→T1→EuTAT@RhB→R1→R2, which also corresponds to the morphological distribution of vanadate. The present application successfully synthesizes a simultaneous analysis of pH and vanadate, and provides a convenient, simplified process, and high-sensitivity visualization platform for the visualization analysis of vanadate. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 SEM images (a, c) and TEM images (b, d, e, f) of EuTAT and EuTAT@RhB during the synthesis process;

[0024] Figure 2 EuTAT@RhB-VO 3- Morphology and element analysis results of the conjugate;

[0025] Figure 3 UV-absorption and fluorescence emission spectra of EuTAT, EuTAT@RhB, and EuTAT@RhB-VO 3-

[0026] Figure 4 (a) Fluorescence emission spectrum of rhodamine B with an excitation wavelength of 260 nm; (b) Fluorescence emission spectrum of EuTAT and EuTAT@RhB; (c) Fluorescence response of EuTAT@RhB to NaVO3, and the inset is a local enlarged image near 590 nm;

[0027] Figure 5 Zeta potential test results of NaVO3, EuTAT@RhB, and EuTAT@RhB-VO 3-

[0028] Figure 6 Fluorescence emission spectra of different Eu:TAT:RhB raw material amounts;

[0029] Figure 7 (a) Fluorescence reaction schematic diagram of EuTAT@RhB and vanadate; (b) Fluorescence emission spectra of EuTAT@RhB and EuTAT@RhB-VO 3- ​​(a) the fluorescence intensity of EuTAT@RhB-VO3 3- (b) as a function of the ultrasonic reaction time; (c) the relative fluorescence intensity (IEuTAT@RhB-VO 3- / IEuTAT@RhB) as a function of the ultrasonic reaction time;

[0030] Figure 8 (a) the excitation spectra of EuTAT@RhB at different emission wavelengths; (b) the emission spectra of EuTAT@RhB at different excitation wavelengths;

[0031] Figure 9 (a) and Na3VO4(c) on the fluorescence response spectra of EuTAT@RhB (λex= 260 nm); the linear relationship between the fluorescence enhancement (I / I0) and the concentration (b, d);

[0032] Figure 10 (a) the fluorescence color of EuTAT@RhB after adding 0, 50, 125 μΜ NaVO3 in solutions with pH values from 1 to 13 (254 nm UV lamp, smartphone shooting); (b, c) the fluorescence emission spectra of EuTAT@RhB-VO3

[0033] Figure 11 (a) and EuTAT@RhB-VO3 - (b) after ultrasonic reaction for 60 min; (d) the fluorescence intensity data of EuTAT@RhB (a) and EuTAT@RhB-VO3 - (b) as a function of the ultrasonic reaction time;

[0034] Figure 12 (a) the response stability of EuTAT@RhB at different pH values and ultrasonic times; (b) the fluorescence emission spectra of EuTAT@RhB before and after adding 50 μΜ VO 3- (a) and EuTAT@RhB-VO 3- (b) as a function of the ultrasonic reaction time; (c) the relative fluorescence intensity (IEuTAT@RhB-VO 3- / IEuTAT@RhB) as a function of the ultrasonic reaction time;

[0035] Figure 13 (a) the repeatability experimental results of EuTAT@RhB material synthesis; (b) the fluorescence emission spectra of EuTAT@RhB before and after adding 50 μΜ NaVO3 in 10 mM Na2SO4 solution;

[0036] Figure 14 (a) the specific responses of EuTAT@RhB in different solutions were tested, including 1) single ion solution: 50 μΜ VO4 3- or VO 3- 4, 200 μΜ SO42- , MoO4 2- , WO4 2- , CrO4 2- ); 2) 50 μM VO4 3- or VO 3- and 200 μM of a mixture of similar ions; 4) a mixture of the four interferents; (b) 50 μM NaVO3or Na3VO4was added to deionized water and 200 μM solutions including CaCl2, CdCl2, Mg(NO3)2, NaCl, Zn(NO3)2, NaNO3, KNO3, Ni(NO3)2, Co(NO3)2, (counterclockwise direction);

[0037] Figure 15 The fluorescence color response of EuTAT@Rh B in real environment. DETAILED DESCRIPTION

[0038] In this study, the high coordination number of Eu 3+ , a typical benzene carboxylic acid derivative, can be used for visual sensing, but is limited by high background in actual detection. The relatively narrow pH response means that it is necessary to modify TAT. The spiro derivative of Rhodamine B has proton transfer ability and is often developed for pH sensing. In addition, the spiro lactam ring of Rhodamine B can break the π-conjugated structure of xanthene, reduce the fluorescence background signal, and restore the fluorescence background signal after ring opening. In order to achieve the two goals of amplifying the fluorescence signal and enriching the pH responsiveness, Rh B is selected as the main structure regulator in the photoluminescence process. Through performance-oriented material structure design, a multifunctional detection window with dual response to pH and vanadate is constructed.

[0039] The application will be further described below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the application, and are not used to limit the scope of the application.

[0040] The reagents and materials used in the following examples, test examples and experimental examples are shown in Table 1, and the instruments and equipment are shown in Table 2.

[0041] Table 1. Experimental reagents

[0042]

[0043]

[0044] Table 2 Instruments and equipment

[0045]

[0046] EMBODIMENT

[0047] I. Experimental Section

[0048] 1. Material synthesis

[0049] 1.1 EuTAT@Rh B fluorescent probe

[0050] 1.1.1 Synthesis of carboxyl activated Rhodamine B solution 1

[0051] Dissolve 0.0497 g of Rhodamine B solid in 10 mL of ultrapure water at room temperature and in the dark. Under continuous stirring, first add 0.2341 g of N-(3-Dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC) and after 10 min add 0.1913 g of N-Hydroxysuccinimide (NHS). After 20 min of waiting, carboxyl activated Rhodamine B solution 1 is obtained.

[0052] 1.1.2 Synthesis of precursor EuTAT solution 2

[0053] Dissolve stoichiometric amounts of 2-Aminoterephthalic acid and sodium bicarbonate in 2 mL of ultrapure water. Let the reaction stand until a clear solution of brown color is obtained. Add 8 mL of 2.5 x 10 -8 M of europium nitrate hexahydrate solution and continue stirring for 30 min to obtain precursor EuTAT solution 2.

[0054] 1.1.3 Synthesis of EuTAT@Rh B ternary composite

[0055] Add the obtained precursor EuTAT solution 2 drop by drop to Rhodamine B solution 1, make up to 35 mL with ultrapure water and continue stirring for 30 min to obtain mixture 3. Then carefully transfer the mixture to a hydrothermal reactor, heat at 160 °C for 10 h, then cool to room temperature, centrifuge at 9000 rpm and for 4 min to obtain the precipitate, wash with a mixture of water and ethanol (ethanol: water = 1:9) until the supernatant does not produce fluorescence under the irradiation of a UV lamp at 254 nm, dry at 60 °C under vacuum for 12 h to obtain the product EuTAT@Rh B.

[0056] 1.2 Synthesis of EuTAT@Rh B-VO 3-

[0057] Weigh an appropriate amount of EuTAT@Rh B dry powder synthesized in 1.1, disperse in an aqueous solution, combine with NaVO3, ultrasonic reaction, centrifugal separation, drying to obtain EuTAT@Rh B-VO 3- powder.​

[0058] 2 Material structure and characterization

[0059] 2.1 Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization

[0060] Reference to the preparation of EuTAT, the obtained precursor EuTAT solution 2 was centrifugally dried to obtain EuTAT powder. An appropriate amount of EuTAT@Rh B dry powder was weighed, and then dispersed in an aqueous solution, combined with NaVO3, ultrasonically reacted, centrifuged, dried to obtain EuTAT@Rh B-VO 3- powder. An appropriate amount of EuTAT, EuTAT@Rh B and EuTAT@Rh B-VO 3- were weighed, and then fixed on the sample stage with double-sided conductive adhesive, and then tested by scanning electron microscopy after gold spraying.

[0061] An appropriate amount of EuTAT, EuTAT@Rh B and EuTAT@Rh B-VO 3- were weighed, and then dispersed in anhydrous ethanol, carefully dropped on a copper mesh, dried with an infrared lamp, and then fixed on the sample stage for transmission electron microscopy testing.

[0062] 2.2 Ultraviolet-absorption and fluorescence emission spectrum characterization

[0063] Verification of material synthesis: a small amount of TAT, Rh B, EuTAT and EuTAT@Rh B were weighed and dispersed in deionized water, ultrasonically agitated, and then injected into a double-pass cuvette to study the changes in ultraviolet-visible absorption.

[0064] A small amount of EuTAT and EuTAT@Rh B was weighed and dispersed in deionized water, and then combined with NaVO3 to obtain EuTAT-NaVO3 and EuTAT@Rh B-NaVO3 after centrifugal drying. An appropriate amount of EuTAT, EuTAT@Rh B, EuTAT-NaVO3 and EuTAT@Rh B-NaVO3 was weighed and dispersed in deionized water, ultrasonically agitated, and then injected into a double-pass cuvette to study the changes in ultraviolet-visible absorption.

[0065] 2.3 Zeta potential test

[0066] An appropriate amount of EuTAT@Rh B, NaVO3 and EuTAT@Rh B-NaVO3 was weighed and dispersed in deionized water, ultrasonically agitated, and then injected into a potential cell to test the Zeta potential.

[0067] 3. Synthesis of EuTAT@RhB fluorescent probe and optimization of test conditions

[0068] 3.1 Raw material dosage optimization (Eu:TAT:Rh B)

[0069] Exploring the optimal dose of Eu 3+ . Synthesis of EuTAT@Rh according to 1.1 B fluorescent probe material, the difference is to change the Eu: TAT: Rh B molar ratio of raw materials is 1:3:1; 2:3:1; 3:3:1. The obtained Eu: TAT: Rh B is dispersed in deionized water, and the fluorescence emission spectrum of NaVO3 at different concentrations is tested.

[0070] 3.2 ultrasonic reaction time optimization

[0071] Synthesis of EuTAT@Rh according to 1.1 B fluorescent probe, EuTAT@Rh B is added to NaVO3 to prepare Eu: TAT: Rh B-NaVO3 solution. Eu: TAT: Rh B and Eu: TAT: Rh B-NaVO3 solution are respectively placed in the ultrasonic reactor, and the ultrasonic reaction time is changed to 0, 10, 20, 30, 60, 90, 120 min, and the fluorescence emission spectrum is tested.

[0072] 3.3 excitation wavelength optimization

[0073] Synthesis of EuTAT@Rh according to 1.1 B fluorescent probe, test the fluorescence emission spectrum under different excitation wavelengths. The excitation wavelength is set to 240, 250, 260, 270, 280, 290 nm.

[0074] 4. Performance test of EuTAT@RhB fluorescent probe

[0075] 4.1 dual-response EuTAT@Rh B fluorescence response to vanadate

[0076] This part uses F-2700 fluorescence spectrophotometer for testing, with 260nm as the excitation wavelength, the excitation light and the emission light slit width are both 5nm, and the photomultiplier tube voltage is 700V.

[0077] The EuTAT@Rh B dispersion liquid is mixed with NaVO3 solution of different concentrations to form the test solution. The final concentration of EuTAT@Rh B is 0.025mg·mL -1 , and the final concentration of NaVO3 is 0-200μmol / L. After ultrasonic oscillation, the fluorescence spectrum of the mixed solution is recorded under 260nm excitation, and the color change of the solution is recorded under 254nm ultraviolet lamp. The detection process of Na3VO4 is the same as above.

[0078] 4.2 pH-dependent fluorescence response of EuTAT@Rh B to NaVO3

[0079] The EuTAT@Rh B dispersion liquid is mixed with NaVO3 solution of different pH to form the test solution. The final concentration of EuTAT@Rh B is 0.025mg·mL -1The final concentration of NaVO3 was 50 μM, and the final pH value of the solution was 1-13. After 20 minutes of ultrasonic reaction, the fluorescence emission spectrum of the mixed solution was recorded under 245 nm excitation, and the fluorescence color change of the solution was recorded with a smartphone under 254 nm ultraviolet light.

[0080] 4.3 Fluorescence stability of EuTAT@RhB in response to NaVO3

[0081] Take an appropriate amount of EuTAT@Rh B aqueous dispersion and mix it with NaVO3 solution to form EuTAT@Rh B-VO3 - Test solution. Test EuTAT@Rh B and EuTAT@Rh B-VO3 - Fluorescence emission spectrum during 100 repetitive scans at a scan rate of 1200 nm / min and a scan interval of 30 s.

[0082] 4.4 Fluorescence stability of EuTAT@RhB in response to pH

[0083] Refer to 2.2.2 to obtain EuTAT@Rh B aqueous dispersion; take an appropriate amount of EuTAT@Rh B aqueous dispersion and mix it with NaVO3 solutions of different pH to form EuTAT@Rh B-VO3 - Test solution. Under the test pH values ​​of 4.5, 7 and 10.5, EuTAT@Rh B and EuTAT@Rh B-VO3 - Fluorescence emission spectra that vary with ultrasound time.

[0084] 4.5 Batch stability of materials

[0085] Prepare three sets of EuTAT@Rh B materials simultaneously, referring to 2.2.2. Take three aliquots from each set and label them A: 1, 2, 3; B: 4, 5, 6; and C: 7, 8, 9. Measure the fluorescence emission spectra of the samples in triplicate. 5. Practical application of EuTAT@RhB fluorescent probe III. Experimental results

[0086] 5.1 Selectivity and anti-interference ability of dual-responsive EuTAT@Rh B towards vanadate

[0087] The structural analogues of vanadate metal oxide anions Na2MoO4·2H2O, Na2WO4·2H2O, K2CrO4 were selected for selective experiments. NaVO3 (50 μM), Na3VO4 (50 μM), Na2MoO4·2H2O, Na2WO4·2H2O and K2CrO4 were prepared at 200 μM each to obtain single ion test solutions; solutions containing 200 μM analogues were mixed with NaVO3 (50 μM) or Na3VO4 (50 μM) respectively to form two kinds of mixed ion simulation solutions. Equal amounts of EuTAT@Rh B dispersion were added to the single ion and mixed ion solutions respectively, and their fluorescence emission spectra were tested.

[0088] Anti-interference experiments were conducted by selecting inorganic ions that may exist in the actual environment. 50 μM NaVO3 or Na3VO4 was added to deionized water and 200 μM of different types of interference ion solutions respectively, including CaCl2, CdCl2, Mg(NO3)2, NaCl, Zn(NO3)2, NaNO3, KNO3, Ni(NO3)2, Co(NO3)2. The fluorescence enhancement ability of EuTAT@Rh B on vanadate was tested.

[0089] 5.2 Double-response EuTAT@Rh B for the detection of vanadate in actual samples

[0090] Fish pond soil and pond water were collected as actual samples for the fluorescence detection of vanadate by EuTAT@Rh B.

[0091] After the pond water was filtered through a 0.22 μM filter membrane, the pH was adjusted to neutral with NaOH. The sample water was treated with 30% hydrogen peroxide to remove reducing impurities in the water and stabilize the possible vanadium in the highest valence state.

[0092] The soil sample was sieved, dried and ground, and a certain mass was weighed for microwave digestion. The obtained digestion solution was adjusted to neutral pH, filtered, and the supernatant was diluted to volume.

[0093] 5.3 Simulating the pH in the actual environment by double-response EuTAT@Rh B

[0094] An appropriate amount of actual fish pond water sample was taken and 50 μM NaVO3 was added to prepare actual water samples with different pH values. The pH values were 2-3, 4.5, 7, 10.5, and 13. An appropriate amount of EuTAT@Rh B dispersion was added to the actual water samples with different pH values, and the fluorescence photos were recorded at different ultrasonic times.

[0095] Figure 1

[0096] 1. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization

[0097] As Figure 1 can be seen, during the synthesis process, the material is transformed from an irregular layered stack structure (EuTAT, Fig. 1-a) to a spherical porous material (EuTAT@Rh B, Figure 1 -c), which is consistent with the TEM Figure 1 -b, d) results obtained by FEI Talos F200X electron microscope. The layer-by-layer stacking of such sheet structures increases the contact area of the material with the target, which is beneficial to improve the sensitivity of detection. At the same time, a small amount of regular strip-shaped structure is observed on the surface Figure 2 -e, f), which indicates that the material may have a certain degree of crystallinity.

[0098] EuTAT@Rh B was reacted with NaVO3 under ultrasonic conditions for 60 min, and then the precipitate was washed with deionized water for 5 times and dried to obtain EuTAT@Rh B-VO3 - powder. As shown in Figure 2 a, b, after the combination of VO3 - , the surface of EuTAT@Rh B-VO3 - is transformed from petal-shaped to spherical aggregation. In addition, combined with the Mapping diagram of the distribution of combined elements, especially the element distribution of vanadium Figure 3 c), a large amount of vanadium can still be observed on the material after multiple centrifugal washing. This shows that after 60 min of ultrasonic, EuTAT@Rh B and VO3 - form a relatively stable donor-acceptor transfer complex.

[0099] 2. Ultraviolet-absorption and fluorescence emission spectrum characterization

[0100] As Figure 3 can be seen, after adding VO 3- , the characteristic peak of EuTAT-VO 3- at 330 nm is enhanced, but the absorbance enhancement effect of EuTAT@Rh B-VO 3- is more significant. The photo corresponding to EuTAT@Rh B-VO 3- shows obvious fluorescence quenching Figure 4 b, inset), and the fluorescence recovers obviously after adding NaVO3. It can be proved that Rh B effectively changes the conjugation degree of the system, reduces the fluorescence signal of the substrate, and improves the sensitivity of vanadate. In addition, combined with the chromaticity coordinate diagram of EuTAT@Rh B-VO 3- at different pH values, it can also be seen that the response of pH has distinguishability.

[0101] The fluorescence spectrum was measured under 260 nm excitation, as shown in Figure 5 , EuTAT only shows TAT emission (3-b), and there is no Eu3+ Emission; EuTAT@Rh B shows double emission peaks at 435 nm and 590 nm from TAT and Rh B respectively. In addition, the fluorescence of TAT is enhanced with the destruction of the spirolactam ring by vanadate, which also shows the weak fluorescence recovery of Rh B at 590 nm. Finally, the typical ligand emission peak of TAT is selected as the signal response peak for subsequent testing.

[0102] 3. Zeta potential test

[0103] The electrical properties of the material surface and its dispersion ability in solution can be obtained by Zeta potential determination. The Zeta potential of the material surface is related to the surface charge and the dispersion ability in solution. Figure 6 It can be seen that the surface charge of EuTAT@Rh B changes from positive to negative after the combination of VO 3- and the EuTAT@Rh B-VO 3- shows a higher absolute potential, indicating that the donor-acceptor transfer complex formed has a higher electrostatic stability.

[0104] 4. EuTAT@Rh B fluorescence probe synthesis and test condition optimization

[0105] 4.1 Raw material dosage optimization (Eu:TAT:Rh B)

[0106] In the construction process of EuTAT@Rh B fluorescence probe, Eu 3+ plays a role in fixing the carboxyl group on TAT, so controlling the amount of Eu3+ added is the key to improving the synthesis efficiency. The fixed ratio of TAT:Rh B is 3:1, and the results are shown in Figure 7 , it is found that EuTAT@Rh B can exhibit better fluorescence response when Eu:TAT:Rh B = 2:3:1. The ratio is used in subsequent experiments.

[0107] 4.2 Ultrasonic reaction time optimization

[0108] Evaluate whether the structure can remain variable and stable within a wider pH value range, which is related to the practicality evaluation of the material and the reliability of the pH value signal detection. According to conventional reports, the spirolactam ring opening reaction is sensitive to acid and will close the fluorescence under neutral conditions. Its fluorescence intensity will also decrease with the increase of alkalinity. However, in the experiment, it is found that the EuTAT@Rh B dispersion can produce weak fluorescence enhancement in neutral environment after prolonged placement time, and the EuTAT@Rh B added with NaVO3 can also produce obvious fluorescence enhancement after overnight placement. This is because the lactam ring of EuTAT@Rh B is opened under light conditions to form a weakly fluorescent active intermediate E1( Figure 7a), this process is relatively slow. In order to accelerate the formation of E1 and the binding of vanadate, this study attempted to increase the reaction rate and enhance fluorescence by ultrasound.

[0109] The experiments have shown that it is feasible to combine EuTAT@Rh B and vanadate via ultrasonic reaction. Figure 7 As shown in b, after 60 minutes of ultrasonic reaction, the fluorescence intensity of EuTAT@Rh B reached its maximum value, and after 120 minutes, the fluorescence intensity still maintained 96%. Therefore, it is believed that the optimal time for EuTAT@Rh B to be converted into E1 is 60 minutes. In addition, according to the fluorescence enhancement detection mechanism of this method, the relative fluorescence intensity (I EuTAT@Rh B-VO3- / I EuTAT@Rh B ) is larger, the more complete the vanadate is bound. Figure 8 It can be found in c that I / I0 begins to enter a stable period at 60 minutes, which indicates that the optimal binding time of vanadate and EuTAT@RhB is also 60 minutes.

[0110] Through this experiment, it was found that under light excitation and ultrasound conditions, EuTAT@Rh B produced a weak fluorescence enhancement in a neutral environment, and the fluorescence intensity remained stable after 60 minutes of ultrasound. This is because the adjacent carboxyl group can open the ring and form intramolecular hydrogen bonds. This feature can provide active binding sites for vanadate, so EuTAT@Rh B-VO 3- Stable fluorescence can also be produced around 60 minutes.

[0111] 4.3 Excitation wavelength optimization

[0112] The optimal excitation wavelength of EuTAT@Rh B was tested, and the results are as follows: Figure 9 As shown in the figure, EuTAT@Rh B was found to have strong emission peaks at 240, 250, 260, and 270 nm. In particular, under excitation at 260 nm, a single and strong emission peak was exhibited from 350 nm to 500 nm. Therefore, 260 nm was selected as the fluorescence excitation wavelength of EuTAT@Rh B.

[0113] 5. Performance test of EuTAT@Rh B fluorescent probe

[0114] 5.1 Fluorescence response of dual-responsive EuTAT@Rh B to vanadate

[0115] To evaluate the sensitivity of EuTAT@Rh B to vanadate, tests were carried out under optimal experimental conditions.

[0116] This part was tested using an F-2700 fluorescence spectrophotometer with an excitation wavelength of 260 nm, slit widths of both the excitation and emission light of 5 nm, and a photomultiplier tube voltage of 700 V.

[0117] Different concentrations of sodium orthovanadate / sodium metavanadate solutions were added to the EuTAT@Rh B dispersion, and the fluorescence excitation and emission spectra of EuTAT@RhB were measured. Figure 9 As shown, it can be seen that at 5.0×10 -7 to 2.0×10 -4 M, NaVO3( Figure 9 a,b) and Na3VO4( Figure 7 There was a significant linear correlation between the concentration of c,d) and the relative fluorescence intensity (I / I0). Figure 10 a, b The COD values ​​of sodium orthovanadate and sodium metavanadate are R 2 =0.9968 and R 2 =0.9949. At the same time, VO 3- and VO4 3- The detection limits (3σ / slope, σ=s / I0) were 1.67×10 -8 mol·L -1 and 2.0×10 -9 mol·L -1 These spectral features indicate that the binding of vanadate to EuTAT@Rh B can trigger a regular enhancement of fluorescence.

[0118] 5.2 pH-dependent fluorescence response of EuTAT@RhB to NaVO3

[0119] During the detection of two vanadates, VO4 3- VO 3- It has stronger fluorescence response characteristics. The effect of pH on EuTAT@Rh B before and after binding with NaVO3 was further studied. Figure 10 As shown. Figure 10 It can be seen from ac that when pH < 3, the cyan fluorescence of EuTAT@Rh B solution is enhanced, and the fluorescence emission peak is between 405 and 460 nm. At pH 3 to 5, the fluorescence of the solution weakens with the increase of pH value, accompanied by the shift of the fluorescence wavelength from 435 nm to 464 nm, which is due to the acid-induced proton transfer process. When the pH value is greater than 5, the fluorescence remains stable, which provides a stable contact platform for the detection of vanadate. Between pH 10 and 12, the fluorescence is enhanced, the emission peak is blue-shifted, and the fluorescence is quenched at around pH = 13. When the pH value is less than 2, vanadium is mainly in the form of (VO3) n n-After pH>10, VO4 begins to appear. 3- , and tends to be stable under strong alkaline conditions. Figure 11 As shown in Figure d, the concentration of sodium metavanadate significantly affects the fluorescence intensity of vanadium in solution. The change in fluorescence color can be used to estimate the pH range of the solution and indirectly determine the form of the vanadate.

[0120] 5.3 Fluorescence stability of EuTAT@RhB in response to NaVO3

[0121] During the test process after the ultrasonic reaction, whether the sample can maintain a relatively stable fluorescence intensity is an issue that cannot be ignored. Under the condition of a scanning speed of 1200nm / min, the test was conducted every 30s, and 100 EuTAT@Rh B and EuTAT@Rh B-VO3 were obtained respectively. - The fluorescence intensity data ( Figure 12 ), the fluorescence intensity error was kept within ±1%, and the RSD was 0.76% (EuTAT@Rh B) and 0.49% (EuTAT@Rh B-VO3 - ), lasting approximately 75 minutes. This indicates that under the test conditions, even after 60 minutes of ultrasonic reaction, the solution can still maintain good fluorescence stability in a static state. Furthermore, because the fluorescent probe EuTAT@Rh B is easily dispersed in aqueous solution, there is no need to worry about the stability of the EuTAT@Rh B solution over an extended period of time.

[0122] 5.4 Fluorescence stability of EuTAT@RhB in response to pH

[0123] EuTAT@Rh B and EuTAT@Rh B-VO3 were investigated under different pH conditions. - (50μmol / L) under different ultrasound times. Comparison of the fluorescence response of EuTAT@Rh B and EuTAT@Rh B-VO3 at pH 4.5, 7 and 10.5 - The fluorescence emission spectrum produced by the change of ultrasound time is as follows Figure 12 .

[0124] like Figure 12 As shown in a, d, and g, EuTAT@RhB exhibited a higher and more stable fluorescence signal after 60 minutes, which was consistent with the EuTAT@Rh B-VO3 - The phenomenon is consistent with ( Figure 12 b, e, h). In addition, the relative fluorescence intensity I EuTAT@Rh B-VO3- / I EuTAT@Rh B The peak value was reached at 60 min. Figure 13 c, f, i).

[0125] 5.5 Batch stability of materials

[0126] Three groups of EuTAT@Rh B materials were prepared simultaneously: three aliquots of each material were taken and labeled A: 1, 2, 3; B: 4, 5, 6; and C: 7, 8, 9. The fluorescence emission spectra of the samples were measured in triplicate for each sample.

[0127] Depend on Figure 14 It can be seen that the relative fluorescence intensity is relatively stable, with RSD values ​​ranging from 0.48% to 3.06%, indicating that instrument errors such as autoclave and batch stability differences are within controllable range.

[0128] 6. Practical application of EuTAT@Rh B fluorescent probe

[0129] 6.1 Selectivity and anti-interference ability of dual-response EuTAT@Rh B towards vanadate

[0130] like Figure 14 As shown in a, the EuTAT@Rh B fluorescent probe is sensitive to VO4 3- or VO3 - The response of the 50μM ion was less affected by the coexisting ions (200μM). Figure 15 In b, the addition of EuTAT@Rh B to single or mixed simulated ions (200 μM) showed a significantly higher ion density than that of VO4 alone. 3- or VO 3- (50 μM) produced a lower fluorescence enhancement. When vanadate and the four ions were present simultaneously, EuTAT@Rh B maintained good selectivity.

[0131] Due to the possible conjugation between the flexible structure of EuTAT@Rh B and the high concentration of benzene ring analogs, it is impossible to perform anti-interference analysis on organic matter. In addition, the actual detection environment is mainly faced with interference from metal ions, and organic interference is not the main factor. 3+ 、Cu 2+ and Al 3+ Such easily hydrolyzed metal ions. Their smaller Ksp values ​​will lead to hydrolysis reactions, eventually producing insoluble compounds, such as Fe(OH)3, Cu(OH)2 and Al(OH)3. In the above experiment, NaVO3 and Na3VO4 can be detected in the range of pH = 4 to 9 and pH = 11 to 12. Within this range, easily hydrolyzed metal cations will begin to produce corresponding hydroxide precipitates. Even some metal ions that cannot be completely hydrolyzed under neutral conditions, such as Cu 2+ Under alkaline conditions of pH 11-12, it can also be separated from the solution in solid form without interfering with the detection of vanadate.

[0132] 6.2 Double-responsive EuTAT@Rh B for the detection of vanadate in real samples

[0133] The results of the recovery experiments of two real water samples are shown in Table 3, with the recovery range of 101.76-120% and RSD (n=6) of 0.85-10.79%. The comparison with the results of ICP-OES indicates the usability of the detection method. In ​ addition, the color of EuTAT@Rh B in real water samples changes with the pH value and the ultrasonic treatment time. In Table 4, the present work is compared with other existing studies, which indicates that the method can be used for the fluorescence detection and pH response of vanadate in a wide range of concentration.

[0134] Table 3. The results of the recovery experiments in water environment and the comparison with the results of ICP-OES

[0135]

[0136] 6.3 Comparison with other works

[0137] Comparison with other quantitative detection methods of NaVO3 / Na3VO4

[0138] Table 4 A recent comparation of quantitative detection method for NaVO3 / Na3VO4

[0139]

[0140]

[0141] 【1】Jia, Y.; Li, D.; Hu, M. A Multifunctional Probe Based on a Heterometallic-Organic Framework: Highly Selective Detection of 1,3-Dinitrobenzene, Tryptophan, and Visual Recognition of Pentavalent Vanadate Ions. Mater. Today Chem. 2023, 30, 101518.

[0142] https: / / doi.org / 10.1016 / j.mtchem.2023.101518.

[0143] 【2】Jeong,H.;Lee,B.-I.;Byeon,S.-H.Antenna Effect on the OrganicSpacer-Modified Eu-Doped Layered Gadolinium Hydroxide for the Detection ofVanadate Ions over a Wide pH Range.ACS Appl.Mater.Interfaces2016,8(17),10946–10953.

[0144] https: / / doi.org / 10.1021 / acsami.6b03703.

[0145] 【3】Sun,T.;Wang,P.;Fan,R.;Chen,W.;Hao,S.;Yang,Y.Functional MicroscaleSingle-Phase White Emission Lanthanide MOF for Tunable Fluorescent Sensingand Water Quality Monitoring.J.Mater.Chem.C2019,7(12),3598–3606.

[0146] https: / / doi.org / 10.1039 / C8TC05968C.

[0147] 【4】Batey,H.D.;Whitwood,A.C.;Duhme-Klair,A.-K.Synthesis,Characterization,Solid-State Structures,and Spectroscopic Properties of TwoCatechol-Based Luminescent Chemosensors for Biologically RelevantOxometalates.Inorg.Chem.2007,46(16),6516–6528.https: / / doi.org / 10.1021 / ic700554n.

[0148] [5] Khavasi, H. R.; Jelokhani, E. A Copper ohydrogel as a Chemosensor for Selective Detection of Oxometalate Anions in Water. J. Mater. Chem. A 2019, 7 (12), 6638-6643.

[0149] https: / / doi.org / 10.1039 / C9TA00912D.

[0150] [6] J.; Berlinger, B.; Thomassen, Y.; R. Simultaneous Speciation Analysis of Chromate, Molybdate, Tungstate and Vanadate in Welding Fume Alkaline Extracts by HPLC-ICP-MS. Talanta 2015, 142, 164-169. https: / / doi.org / 10.1016 / j.talanta.2015.04.067.

[0151] [7] Kilibarda, N.; Afton, S. E.; Harrington, J. M.; Yan, F.; Levine, K. E. Rapid Speciation and Determination of Vanadium Compounds Using Ion-Pair Reversed-Phase

[0152] Ultra-High-Performance Liquid Chromatography Inductively Coupled Plasma-Sector Field Mass Spectrometry. J. Chromatogr. A 2013, 1304, 121-126.

[0153] https: / / doi.org / 10.1016 / j.chroma.2013.06.074.

[0154] 【8】Muya, F. N.; Baker, P. G. L.; Iwuoha, E. I. Polysulfone Hydrogel Nanocomposite Alkaline Phosphatase Biosensor for the Detection of Vanadium. Electrocatalysis 2020, 11 (4), 374-382. https: / / doi.org / 10.1007 / s12678-020-00592-0.

[0155] In summary, it can be seen that the embodiment of the application designs a "switch" fluorescent probe controlled by a spiro lactam ring, the synthesized EuTAT@Rh B complex has pH responsiveness and low fluorescence background, the fluorescence signal change caused by the pH-dependent morphological structure conversion and the conjugated system change induced by vanadate coordination can be realized, the synchronous morphological discrimination of vanadate solution monitoring is realized in the ultraviolet and fluorescence dual channels, and a convenient, process simplified, high sensitivity visual platform is provided for visual analysis of vanadate.

[0156] The present application is not limited to the use of the embodiments described and illustrated in the specification, and it can be applied in any field suitable for the application, and further modifications and variations can be easily made by those skilled in the art without departing from the spirit and essence of the application, and all such modifications and variations shall fall within the scope of the application.

[0157] The above only describes some embodiments of the application, and does not limit the embodiments and protection scope of the application. Those skilled in the art should realize that any equivalent replacement and obvious change made according to the content of the specification should be included in the protection scope of the application.

Claims

1. A method for preparing a dual-response visual fluorescent probe, characterized in that: The steps include: 1) Synthesis of carboxyl-activated Rhodamine B solution 1: Rhodamine B solid was dissolved in ultrapure water at room temperature and protected from light. EDC was first added under continuous stirring, followed by NHS after 10 minutes. After 20 minutes, carboxyl-activated Rhodamine B solution 1 was obtained. 2) Synthesis of precursor EuTAT solution 2: Dissolve 2-aminoterephthalic acid TAT and sodium bicarbonate in ultrapure water, let it stand and react until it turns into a brown clear solution, add Eu 3+ The solution was stirred for 30 min to obtain the precursor EuTAT solution 2; 3) Synthesis of EuTAT@RhB fluorescent probe: The obtained precursor EuTAT solution 2 was added dropwise to the Rhodamine B solution 1, and stirring was continued for 30 minutes to obtain a mixed solution 3; the mixed solution 3 was then transferred to a hydrothermal reactor, heated at 160°C for 10 hours, and then cooled to room temperature. The precipitated product was obtained by centrifugation, and washed with a mixed solution of water and ethanol until the supernatant showed no fluorescence under 254nm ultraviolet light. The product was then vacuum dried to obtain the product EuTAT@RhB.

2. The preparation method according to claim 1, wherein: In step 1), the mass ratio is: Rhodamine B:EDC:NHS=0.04-0.05:0.2-0.3:0.15-0.

25.

3. The preparation method according to claim 1, wherein: According to the molar ratio, Eu 3+ :TAT:Rh B=1~3:3:

1.

4. The dual-response visual fluorescent probe EuTAT@RhB prepared according to the preparation method according to any one of claims 1 to 3.

5. Use of the dual-response visual fluorescent probe EuTAT@RhB as claimed in claim 4 in vanadate detection.

6. The use according to claim 5, characterized in that The vanadate is (VO3)n n- Salt and VO4 3- At least one of the salts.

7. A vanadate detection method, characterized in that: The steps include: S1: preparing the dual-response visual fluorescent probe EuTAT@RhB according to claim 4 into a solution, and ultrasonically obtaining a EuTAT@Rh B dispersion; S2: Add EuTAT@Rh B dispersion into the water sample, sonicate, and perform fluorescence detection.

8. The detection method according to claim 7, wherein: The pH of the water sample is 1-13.

9. The detection method according to claim 7, wherein: The ultrasonic dispersion time in step S2 is ≥60 min.

10. The detection method according to claim 7, wherein: The excitation wavelength of the fluorescence detection is 240-290 nm.

Images