CN113292986A

CN113292986A - Metal organic framework composite material for detecting molybdate radical and preparation method and application thereof

Info

Publication number: CN113292986A
Application number: CN202110521451.XA
Authority: CN
Inventors: 周金风; 楚纯洁
Original assignee: Pingdingshan University
Current assignee: Pingdingshan University
Priority date: 2021-05-13
Filing date: 2021-05-13
Publication date: 2021-08-24

Abstract

The invention provides a method for MoO₄ ^2‑The composite probe material can detect MoO through the change of fluorescence intensity₄ ^2‑Concentration belongs to the technical field of environmental analysis and detection. So far, there has been little concern about MoO₄ ^2‑Literature reports of concentration detection. Thus, the present invention is in MoO₄ ^2‑The concentration detection aspect has important significance. Compared with the prior art, the invention has the following remarkable advantages: (1) the composite probe material is prepared rapidly in a water phase under room temperature stirring, so that the preparation process of the fluorescent probe is simple, environment-friendly and energy-saving; (2) the fluorescent probe material prepared by the process has high purity and strong stability; (3) the fluorescenceThe probe material belongs to a dual-wavelength proportional metering type fluorescent probe, has a self-correcting function and has higher sensitivity; (4) the probe material has magnetic separation performance, and can realize rapid separation and recovery through an external magnetic field.

Description

Metal organic framework composite material for detecting molybdate radical and preparation method and application thereof

Technical Field

The invention relates to MoO₄ ^2-A metal organic framework composite fluorescent probe material for concentration detection, in particular to a MoO with dual-wavelength self-correction and magnetic separation performance₄ ^2-Metal organic framework composite material for concentration detection and preparation method and application thereof。

Background

Molybdenum is a transition element and is an essential trace element for human bodies, animals and plants. In addition, molybdenum has a high melting point and hardness, and good thermal conductivity and corrosion resistance, so that molybdenum has wide application in the fields of machinery, electronics, medicine and the like. Molybdate anion (MoO)₄ ^2-) Is the main existing form of molybdenum in aqueous solution and is an important source for absorbing molybdenum by organic matters. However, excess Mo is a harmful or potentially harmful contaminant, creating a sensitive and rapid MoO₄ ^2-The detection method has important significance. However, so far with respect to MoO₄ ^2-Few documents are reported for ion detection, and the currently reported methods mainly include chromogenic reaction, spectrophotometry, ion chromatography and the like. However, the above method is in MoO₄ ^2-The detection has many defects, such as complicated sample pretreatment, high analysis cost, large-scale instrument and equipment, low sensitivity and the like. In contrast, fluorescence detection technology is receiving more and more attention in the monitoring field due to its advantages of fast response, signal visualization, simple operation, high sensitivity, and the like. Most of the currently reported fluorescence sensors rely on the change (such as intensity enhancement or quenching) of a single fluorescence signal, and these fluorescence probes are susceptible to the interference of external environmental factors unrelated to the concentration of the substance to be detected, such as light scattering of a sample matrix, fluctuation of an excitation source, a special microenvironment around the probes, local concentration change of the probes and the like, which all generate unavoidable interference. The dual-wavelength proportional metering type fluorescent probe material utilizes the ratio of two fluorescent bands to replace the absolute intensity of one fluorescent band for quantification, and provides the practical advantage of built-in variable correction, thereby having higher signal-to-noise ratio and sensitivity. In addition, compared with homogeneous phase fluorescent probe materials, the heterogeneous phase fluorescent sensing probe materials have the advantages of being separable and recyclable. Thus, the design and synthesis can be used for MoO₄ ^2-The detected heterogeneous phase and proportional metering type fluorescent sensing probe material has important significance.

As a novel crystalline porous material, a metal-organic framework (MOFs) has excellent properties such as high porosity, super-large specific surface area, porosity, order, adjustable pore channel structure and the like, so that the MOFs has excellent performance and application prospects in the aspects of adsorption, separation, catalysis, sensing, ion conduction and the like. At present, a great deal of literature reports that MOFs are used as a carrier to stabilize and disperse guest molecules such as photosensitizers or inorganic nanoparticles to prepare host-guest composite materials, and the MOFs are used in different fields. Up to now, MOFs are widely used as fluorescent probes for detecting metal ions, biological small molecules, organic volatile solvents, and the like. Compared with other fluorescent probe materials, the MOFs probe material also has the advantages of adsorption and enrichment, so that the MOFs probe material has higher sensitivity in the aspect of analysis and detection and has lower detection limit. Therefore, MOFs are an ideal carrier for preparing heterogeneous fluorescent probe materials.

Among the MOFs, zeolite imidazole framework MOFs (ZIFs) have important application values in many fields such as catalysis, separation, sensing and the like due to the characteristics of both MOFs and molecular sieves, such as ultra-large specific surface area, high porosity, high crystallinity, abundant functional groups and excellent stability. In ZIFs, where ZIF-8 is Zn²⁺The ZIF is a metal ion, 2-methylimidazole is a ZIF with a sodalite topological structure formed by molecular self-assembly of an organic ligand, and has the advantages of easiness in preparation, permanent porosity, high structural flexibility, strong stability and the like. Therefore, ZIF-8 is an ideal photosensitizer carrier material.

In addition, the fluorescent probe material with magnetic separation performance can be recycled through simple magnetic separation, and has practical application value. Thus, the design synthesis has dual wavelength self-correcting, magnetic separation for MoO₄ ^2-The detected heterogeneous MOFs fluorescent probe material has important significance.

So far only two have been concerned with MoO₄ ^2-Literature reports of fluorescent probes. 2012, Singh et al prepared luminescent iridium compounds, MoO₄ ^2-Chelating and coordinating with the iridium compound to cause fluorescence intensity quenching, and performing MoO (metallo-organic) reaction according to the fluorescence intensity₄ ^2-The relationship between the concentrations is thus used for MoO₄ ^2-Determination of concentration (c.e. castillo, d.l. davies, a.k.duhme Klair, k.singha and s.single. Luminescent iridium complexes for detection of molybdate. dalton trans, 2012,41, 628). However, the probe material has many defects: (1) the preparation method is complicated and can be prepared only by multi-step organic synthesis; (2) the probe material belongs to a single-wavelength quenching type, and only depends on single-wavelength fluorescence quenching to detect MoO₄ ^2-Due to the change of the concentration, the sensitivity of the probe material is low, and the probe material is easily interfered by the external environment. In 2020, Yang et al prepared layered europium hydroxide inorganic material, and utilized antenna effect between molybdate and layered europium hydroxide (LEuH), to realize detection of trace molybdate ions in aqueous solution (b.y.sho, x.b.zhang, x.y.wang, f.m.cui and x.j.yang. the Optical sensitive detection of molybdenum ions by layered europium hydroxides. Optical Materials,2020,100,109597). The probe material also has a plurality of defects: (1) to MoO₄ ^2-The response time is long, the detection can be carried out within 30min, the consumed time is long, and the practical application is not facilitated; (2) the probe material belongs to single-wavelength enhancement mode, and only depends on single-wavelength fluorescence enhancement to detect MoO₄ ^2-Due to the change of the concentration, the sensitivity of the probe material is low, and the probe material is easily interfered by the external environment.

Based on the defects of the prior art, the invention aims to provide a rapid, simple, convenient and green pollution-free MOFs probe material preparation process, and the MOFs probe material is used for MoO in water₄ ^2-And (4) detecting the concentration. The invention prepares the magnetic metal organic framework material in water under the condition of stirring at room temperature, has simple preparation process, is green and environment-friendly, and the synthesized luminescent magnetic MOFs material has high purity and high stability and is in MoO₄ ^2-The concentration detection has the advantages of rapidness, simplicity, convenience, high sensitivity and magnetic separation.

In order to achieve the experimental purpose, the technical scheme of the invention is as follows: for MoO₄ ^2-The preparation method of the metal organic framework MOFs composite material for concentration detection comprises the following steps:

(1) preparation of magnetic Fe₃O₄A nanoparticle; the magnetic Fe₃O₄The nano particles are prepared by adopting a polyvinylpyrrolidone method;

(2) weighing the product Fe obtained in the step (1)₃O₄Adding two fluorescent reagents rhodamine B (RhoB) and fluorescent Brightener BBU (BBU) with different emission wavelengths into nanoparticles, adding 2-methylimidazole solution required by synthesis of metal organic framework materials, uniformly dispersing by ultrasonic wave, and adding Zn (NO)₃)₂·6H₂O, stirring for 10-15 minutes at room temperature, then carrying out magnetic separation, washing and drying to obtain the MoO₄ ^2-Detected proportional metering type metal organic framework BBU/RhoB @ Fe₃O₄@ ZIF-8 composite material; said Fe₃O₄The addition amount of (A) is 0.2-1.0 mL; the molar ratio of the BBU to the rhodamine 6G is 1: 10-10: 1; zn (NO)₃)₂·6H₂The molar ratio of O to 2-methylimidazole is 1: 10-1: 35.

Preferably, the method comprises the following steps: zn (NO)₃)₂·6H₂The molar ratio of O to 2-methylimidazole is 1: 30.

Preferably, magnetic Fe is prepared₃O₄The nanoparticle method is as follows: 80mL of distilled water was added with FeCl₂·4H₂O (0.86g) and FeCl₃·6H₂O(2.36g)，N₂To the mixture was added dropwise 5mL of aqueous ammonia (25 wt%), heated to 80 deg.C, stirred for 1h, washed several times with water, and dispersed in 20mL of water. Then adding 1mL of polyvinylpyrrolidone aqueous solution containing 200mg, stirring at room temperature for 24h, and collecting Fe by magnetic separation after the reaction is finished₃O₄The nanoparticles were washed several times with water and then dispersed into 30mL of water for further use.

Preferably, said Fe₃O₄The addition amount of (A) is 0.5 mL; the molar ratio of BBU to RhoB is 1: 1.

In order to achieve the above experimental purpose, another technical solution of the present invention is as follows: the method is used for preparing the metal organic framework material with nitenpyram identification detection.

In order to achieve the above experimental purpose, another technical solution of the present invention is as follows: the metal organic framework material with magnetic separation and dual-wavelength proportion metering is used for selectively identifying MoO₄ ^2-Application of the aspect.

Application of magnetic MOFs (metal-organic frameworks) probe material obtained by utilizing preparation process, and MOFs fluorescent probe used for MoO (metal-organic framework) in water body₄ ^2-Selective and highly sensitive recognition, and can recover the probe material by simple separation of an applied magnetic field.

The invention has the beneficial effects that:

compared with the prior art, the invention has the following remarkable advantages:

(1) the MoO provided by the invention₄ ^2-The magnetic MOFs fluorescent probe material is rapidly synthesized in an environment-friendly solvent water phase under the condition of stirring at room temperature. The preparation process does not produce toxic and harmful byproducts, thereby being more environment-friendly. In addition, the material is prepared only by a common reaction vessel and a simple stirring device, so that the preparation process is simple and the cost is low;

(2) the fluorescent probe material prepared by the process has strong stability, and the fluorescence intensity of the fluorescent probe material is stable in water for several days and cannot be attenuated;

(3) the fluorescent probe material belongs to a dual-wavelength proportional metering type fluorescent probe material and has higher sensitivity;

detection of MoO by fluorescent probe material in the invention₄ ^2-The linear range is 0-0.020mM, the detection limit is 21nM, and the detection result shows that the probe material detects MoO₄ ^2-Has high sensitivity. At present, MoO is rarely involved₄ ^2-Report of fluorescent probe materials, in which layered europium hydroxide inorganic materials were used for detecting MoO₄ ^2-The detection limit is 100ppm and is far higher than that of the fluorescent probe material in the invention.

(4) The probe material has magnetic separation performance, and can realize quick separation and recovery through simple magnetic separation;

(5) the probe material is to MoO₄ ^2-The detection response time is fast, and moreHas practical application value;

detection of MoO by fluorescent probe material in the invention₄ ^2-The response is fast, and the reaction can be completed within 10s, so that the BBU/RhoB @ Fe₃O₄@ ZIF-8 in MoO₄ ^2-The detection aspect has higher practical application value. At present, MoO is rarely involved₄ ^2-Report of fluorescent probe materials, in which layered europium hydroxide inorganic materials were used for detecting MoO₄ ^2-The time response time is long, and the detection can be carried out within 30min, which is not beneficial to practical application.

(6) The probe material is used for MoO₄ ^2-The selectivity is good when detecting, and the method is not interfered by other common cations and anions.

(7) The BBU/RhoB @ Fe can be rapidly prepared in water₃O₄@ ZIF-8 composite material. At present, the synthesis and preparation of Fe are also reported in the literature₃O₄@ ZIF-8 composite material, which is usually prepared in methanol, cannot be prepared in methanol solvent by one-step method because BBU is insoluble in methanol solvent₃O₄@ ZIF-8 material. In addition, this application employs the preparation of BBU/RhoB @ Fe in water₃O₄@ ZIF-8 by continuously debugging Zn (NO)₃)₂·6H₂Concentration and ratio of O and 2-methylimidazole, Zn (NO)₃)₂·6H₂The molar ratio of O to 2-methylimidazole is 1:30, so that the composite material can be rapidly synthesized within 10-15 minutes, and the reaction time is greatly shortened compared with the synthesis method reported in the literature.

(8)Fe₃O₄There are many synthetic methods for preparing Fe, and this application has tried various methods to prepare Fe₃O₄The method comprises (1) adding FeCl to ethylene glycol₃Sodium citrate and sodium acetate, dissolving and mixing uniformly, transferring into a high-temperature reaction kettle, and obtaining a black product Fe through a hydrothermal reaction₃O₄Cooling to room temperature after the reaction is finished, collecting the product through magnetic separation, washing with pure water and absolute ethyl alcohol respectively, and drying to obtain magnetic Fe₃O₄(ii) a (2)2mmol of ferric triacetylacetone dissolved inReacting at 110 ℃ for 1h in a mixed solvent of 10mL of benzyl ether and 10mL of oleylamine, then heating to 300 ℃ for reacting for 2h, cooling to room temperature, then adding 50mL of ethanol solution, carrying out magnetic separation, washing with ethanol, drying, and then obtaining the magnetic Fe₃O₄The nanoparticles were re-diffused into 1.0mL of oleic acid for further use. (3) FeCl is added₃·6H₂O(75mL，134mmol L^-1) And FeCl₂·4H₂O (75mL, 67mmol L-1), then NaOH solution (2mol L) was gradually added dropwise^-130mL) is heated to 60 ℃, ultrasonic reaction is carried out for 1h, products are collected through magnetic separation after the reaction is finished, and the products are respectively washed and dried by pure water and absolute ethyl alcohol to obtain magnetic Fe₃O₄。

Fe obtained by the above preparation method₃O₄It could not be loaded into the ZIF-8 pore channels in the aqueous phase. Fe modified with polyvinylpyrrolidone of the present application₃O₄Can be quickly loaded into the ZIF-8 pore channel in the water phase.

Thus, the present invention is in MoO₄ ^2-The concentration detection aspect has important significance. Compared with the prior art, the invention has the following remarkable advantages: (1) the composite probe material is prepared rapidly in a water phase under room temperature stirring, so that the preparation process of the fluorescent probe is simple, environment-friendly and energy-saving; (2) the fluorescent probe material prepared by the process has high purity and strong stability; (3) the fluorescent probe material belongs to a dual-wavelength proportional metering type fluorescent probe, has a self-correcting function, and has higher sensitivity and high sensitivity; (4) the probe material has magnetic separation performance, and can realize rapid separation and recovery through an external magnetic field. Therefore, the fluorescent probe provided by the invention is prepared by the preparation method and is used for detecting MoO₄ ^2-Has significant advantages in terms of concentration.

The MoO provided by the invention₄ ^2-The composite fluorescent probe material can be prepared by MoO₄ ^2-The concentration detection has remarkable advantages.

Drawings

In order to facilitate further understanding of the present application, some of the illustrative drawings are provided herein and are not to be construed as unduly limiting the present application.

Detailed Description

The contents of the present invention will be further clarified by the following examples, which are not intended to limit the scope of the present invention, and various modifications that can be made by those skilled in the art without inventive efforts based on the technical solution of the present invention are still within the scope of the present invention.

FIG. 1 is a crystal structure of ZIF-8 in the present invention;

FIG. 2 shows BBU/RhoB @ Fe as fluorescent probe material of the present invention₃O₄A schematic of the preparation of @ ZIF-8;

FIG. 3 shows Fe in the present invention₃O₄Scanning electron microscope images of;

FIG. 4 is ZIF-8 and BBU/RhoB @ Fe₃O₄@ ZIF-8 pictures under visible light;

FIG. 5 shows BBU/RhoB @ Fe as fluorescent probe material of the present invention₃O₄@ZIF-8、Fe₃O₄Synthetic ZIF-8, simulated ZIF-8 powder X-ray diffraction patterns;

FIG. 6 shows BBU/RhoB @ Fe of the present invention₃O₄@ ZIF-8 scanning Electron microscopy (left panel) and Transmission Electron microscopy (right panel);

FIG. 7 shows BBU/RhoB @ Fe as fluorescent probe material of the present invention₃O₄@ ZIF-8 and Fe₃O₄Hysteresis loop curve of (1);

FIG. 8 shows BBU/RhoB @ Fe as fluorescent probe material of the present invention₃O₄@ ZIF-8 under the action of an external magnetic field;

FIG. 9 shows BBU and RhoB aqueous solutions and ZIF-8, BBU/RhoB @ Fe₃O₄@ ZIF-8 and Fe₃O₄Absorption spectrum of solid powder sample;

FIG. 10 shows BBU/RhoB @ Fe as fluorescent probe material of the present invention₃O₄The three-dimensional fluorescence spectrum of @ ZIF-8;

FIG. 11 shows BBU/RhoB @ Fe as fluorescent probe material of the present invention₃O₄The photostability map of @ ZIF-8;

FIG. 12 shows fluorescence in the present inventionOptical probe material BBU/RhoB @ Fe₃O₄@ ZIF-8 with MoO₄ ^2-Change of fluorescence spectrogram with increased concentration;

FIG. 13 shows BBU/RhoB @ Fe of the present invention₃O₄@ ZIF-8 fluorescent probe material added with MoO₄ ^2-Graph of the intensity of the post-fluorescence as a function of time;

FIG. 14 shows BBU/RhoB @ Fe of the present invention₃O₄@ ZIF-8 fluorescent probe material added with MoO₄ ^2-The rear color coordinate changes;

FIG. 15 shows BBU/RhoB @ Fe as fluorescent probe material of the present invention₃O₄@ ZIF-8 fluorescent probe material to MoO in the presence of interferent₄ ^2-In which MoO₄ ^2-The concentration is 0.01mM, and the concentration of other interfering substances is 0.1 mM;

FIG. 16 is a BBU aqueous solution with MoO₄ ^2-A graph of fluorescence spectrum change with increasing concentration;

FIG. 17 is BBU @ Fe₃O₄@ ZIF-8 addition of MoO₄ ^2-A post-fluorescence spectrum change map;

FIG. 18 is BBU @ ZIF-8 with MoO added₄ ^2-A post-fluorescence spectrum change map;

FIG. 19 shows mixed aqueous solutions of BBU + RhoB with MoO₄ ^2-A graph of fluorescence spectrum change with increasing concentration;

FIG. 20 is BBU/RhoB @ Fe₃O₄@ ZIF-8 with MoO₄ ^2-Increase in concentration changes in the fluorescence spectrum.

Example 1.Fe₃O₄Synthesis of (2)

80mL of distilled water was added with FeCl₂·4H₂O (0.86g) and FeCl₃·6H₂O(2.36g)，N₂To the mixture was added dropwise 5mL of aqueous ammonia (25 wt%), heated to 80 deg.C, stirred for 1h, washed several times with water, and dispersed in 20mL of water. Then adding 1mL of polyvinylpyrrolidone aqueous solution containing 200mg, stirring at room temperature for 24h, and collecting Fe by magnetic separation after the reaction is finished₃O₄The nanoparticles were washed several times with water and then dispersed into 30mL of water for further use.

Example 2 BBU/RhoB @ Fe₃O₄Synthesis of @ ZIF-8

First, 0.01mol/L BBU and 0.01 mol/L10 mL RhoB aqueous solution were prepared. 0.5mL of 0.01mol/L BBU, 0.5mL of 0.01mol/L RhoB and 0.5mL of Fe prepared as described above were removed₃O₄Magnetic ions are fully and uniformly mixed. Then 30mmol of 2-methylimidazole are weighed out and 3.0mL of H are added₂And (4) carrying out ultrasonic dissolution on O, adding the O into the mixed solution, and uniformly stirring. Weighing 1mmol Zn (NO)₃)₂·6H₂O dissolved in 1mL H₂O, dropwise adding it to the above solution, and adding Zn (NO)₃)₂·6H₂A large amount of precipitate is generated immediately, then the reaction is stopped after stirring for 10 minutes at room temperature, magnetic separation, water washing and ethanol washing are carried out until the supernatant is almost colorless, and the red BBU/RhoB @ Fe is obtained after drying₃O₄The @ ZIF-8 product, as shown in FIG. 4.

Study of BBU/RhoB @ Fe by powder X-ray (PXRD)₃O₄The crystal structure of @ ZIF-8, the results are shown in FIG. 5. As can be seen from FIG. 5, the ZIF-8 and BBU/RhoB @ Fe prepared according to the present invention₃O₄@ ZIF-8 is completely consistent with a PXRD spectrogram of theoretical simulation ZIF-8, which indicates that the BBU/RhoB @ Fe is successfully prepared₃O₄@ ZIF-8, and BBU, RhoB and Fe₃O₄The crystal structure integrity of ZIF-8 is not destroyed after loading. BBU/RhoB @ Fe by SEM and TEM₃O₄The @ ZIF-8 microstructure was characterized and the results are shown in FIG. 6. As can be seen from the figure, BBU/RhoB @ Fe₃O₄@ ZIF-8 has uniform particle size and good dispersibility, and MOFs can be seen to be loaded with granular substance Fe from a transmission electron microscope₃O₄. The magnetic property of the magnetic material is researched by a hysteresis loop curve, and as shown in FIG. 7, the experiment shows that the prepared BBU/RhoB @ Fe₃O₄@ ZIF-8 has excellent magnetic separation performance, and can realize rapid magnetic separation under the action of an external magnetic field for 1min (figure 8).

BBU, RhoB aqueous solution, ZIF-8, BBU/RhoB @ Fe₃O₄@ ZIF-8 and Fe₃O₄The absorption spectrum of the solid powder sample is shown in FIG. 9. As can be seen, ZIF-8 is at 3No absorption band in the range of 00-700 nm. By comparing the absorption spectra with BBU and RhoB aqueous solutions, it is obvious that BBU/RhoB @ Fe loaded with BBU and RhoB₃O₄The absorption band of @ ZIF-8 is derived from BBU and RhoB, which also indicates that BBU and RhoB were successfully loaded into the ZIF-8 channels.

BBU/RhoB@Fe₃O₄The @ ZIF-8 three-dimensional fluorescence spectrum is shown in FIG. 10, and BBU/RhoB @ Fe was studied by three-dimensional fluorescence spectrum₃O₄@ ZIF-8 excitation and emission bands. As can be seen from the figure, BBU/RhoB @ Fe₃O₄@ ZIF-8 has two emission bands, one at 433nm, which is derived from the luminescence of the fluorescent whitening agent BBU, and the other at 590nm, which is derived from the luminescence of RhoB. In addition, it is also seen from the three-dimensional fluorescence spectrum that BBU and RhoB have a common excitation band at about 365nm, and therefore the excitation wavelengths used in the present invention are all set to 365 nm.

In addition, by detecting BBU/RhoB @ Fe for 7 days₃O₄The stability of the @ ZIF-8 luminescence spectrum change research (figure 11) shows that the composite material has strong light stability, and the luminescence intensity of the composite material has no obvious quenching change after a plurality of days.

Example 3 application

The invention provides BBU/RhoB @ Fe₃O₄@ ZIF-8 magnetic nanocomposite in MoO₄ ^2-The application of the detection aspect is as follows: BBU/RhoB @ Fe₃O₄@ ZIF-8 is dispersed in ethanol, ultrasonic diffusion is uniform, and then the MoO is detected by taking 365nm as excitation wavelength through fluorescence emission spectrum change₄ ^2-The concentration of (c). The probe material can be recovered by magnetic separation after each detection.

The specific application method is as follows: weighing 6mg BBU/RhoB @ Fe₃O₄The @ ZIF-8 composite material is ultrasonically dispersed in 3mL of ethanol, and after uniform diffusion, MoO with different amounts is added in sequence₄ ^2-The change of the emission spectrum was measured with 365nm as the excitation wavelength. As shown in FIG. 12, with MoO₄ ^2-The concentration is increased, the emission band of BBU is gradually increased, the luminous intensity of RhoB is unchanged, and the ratio of BBU luminous intensity to RhoB luminous intensity isWith MoO₄ ^2-The concentration is in direct proportion, which also indicates that the probe material has a dual-wavelength self-correcting function, MoO₄ ^2-The linear range of detection is 0-0.020 mM. In addition, the MoO thereof is calculated from the linear regression equation₄ ^2-The detection limit of (A) is 21nM, which indicates that the fluorescent probe has high sensitivity.

BBU/RhoB@Fe₃O₄@ ZIF-8 detection of MoO₄ ^2-The response time of (c). The specific experimental operations were as follows: 6.0mg BBU/RhoB @ Fe was weighed₃O₄@ ZIF-8 ultrasonic diffusing into 3mL of ethanol, and adding 10uM MoO₄ ^2-Immediately testing the emission spectrum change, measuring once every 10s, and the experimental result is shown in FIG. 13, BBU/RhoB @ Fe₃O₄@ ZIF-8 detection of MoO₄ ^2-The response was very fast, 10s ready to react, which allowed BBU/RhoB @ Fe₃O₄@ ZIF-8 in MoO₄ ^2-The detection aspect has higher practical application value.

BBU/RhoB@Fe₃O₄@ ZIF-8 Selectivity test. The specific experimental operations were as follows: 6.0mg BBU/RhoB @ Fe was weighed₃O₄@ ZIF-8 ultrasonic diffusion into 3mL of ethanol, and multiple portions of BBU/RhoB @ Fe are prepared by adopting the same experimental operation₃O₄@ ZIF-8 ethanol diffusion solution, in the presence of 0.10mM interfering ions to determine MoO₄ ^2-Researching BBU/RhoB @ Fe through change conditions before and after emission spectrum₃O₄@ ZIF-8 Selectivity, results are shown in FIG. 13. Common cations and anions do not cause BBU/RhoB @ Fe₃O₄@ ZIF-8 emission spectrum was significantly changed while one-tenth amount of MoO was added₄ ^2-Can cause the emission band of BBU to be obviously enhanced, which shows that the fluorescent probe composite material prepared by the invention has strong MoO₄ ^2-Selective recognition capability.

Example 4BBU/RhoB @ Fe₃O₄@ ZIF-8-1 for detecting MoO in actual water sample₄ ^2-Concentration of

Taking a flat-topped mountain and white tortoise mountain reservoir as a sampling point, taking water from five places at random, mixing uniformly, and dividing into 3 partsNumbered 1-3. Different amounts of MoO were added to 3 water samples using standard addition methods₄ ^2-5.0. mu.M, 10.0. mu.M and 15.0. mu.M MoO were prepared, respectively₄ ^2-Solution and then measuring MoO₄ ^2-Concentrations, measured in triplicate for each sample, were averaged and the recovery and relative standard deviation calculated, with the results shown in table 1. From Table 1, it can be seen that the recovery of nitenpyram is from 99.2% to 103.7%, which indicates that BBU/RhoB @ Fe₃O₄@ ZIF-8 has good detection effect in an actual water sample.

TABLE 1 BBU/RhoB @ Fe₃O₄@ ZIF-8-1 for MoO in actual water sample₄ ^2-Concentration detection result

Comparative example 1

2012, Singh et al prepared luminescent iridium compounds, MoO₄ ^2-Chelating and coordinating with the iridium compound to cause fluorescence intensity quenching, and performing MoO (metallo-organic) reaction according to the fluorescence intensity₄ ^2-The relationship between the concentrations is thus used for MoO₄ ^2-Determination of concentration (c.e. castillo, d.l. davies, a.k.duhme Klair, k.singha and s.singh.luminescense iridium complexes for detection of molybdate. dalton trans, 2012,41, 628). However, the probe material has many defects: (1) the preparation method is complicated and can be prepared only by multi-step organic synthesis; (2) the probe material belongs to a single-wavelength quenching type, and only depends on single-wavelength fluorescence quenching to detect MoO₄ ^2-Due to the change of the concentration, the sensitivity of the probe material is low, and the probe material is easily interfered by the external environment.

Comparative example 2

In 2020, Yang et al prepared layered europium hydroxide inorganic material, and utilized antenna effect between molybdate and layered europium hydroxide (LEuH) to realize detection of trace molybdate ions in aqueous solution (b.y. Shao, x.b.zhang, x.y.wang, f.m.cui and x.j.yang. the optical sensitive detection of molybdenum ions by layered europium hydroxideoptical Materials,2020,100,109597). The probe material also has a plurality of defects: (1) to MoO₄ ^2-The response time is long, the detection can be carried out within 30min, the consumed time is long, and the practical application is not facilitated; (2) the probe material belongs to single-wavelength enhancement mode, and only depends on single-wavelength fluorescence enhancement to detect MoO₄ ^2-Due to the change of the concentration, the sensitivity of the probe material is low, and the probe material is easily interfered by the external environment.

Comparative example 3

The fluorescent probe material BBU/RhoB @ Fe in the invention₃O₄@ ZIF-8 in titrating MoO₄ ^2-When the RhoB transmitting signal is not changed, BBU (baseband unit) can follow MoO₄ ^2-The concentration is increased to be remarkably enhanced, and therefore MoO is presumed to be₄ ^2-Reacts only with BBU to cause a change in emission spectrum, so that an aqueous BBU solution (10) is used^-5mol/L) titration of MoO₄ ^2-The results of the verification are shown in fig. 16. As can be seen from the graph, the BBU luminescence spectrum did not change with increasing concentration of molybdic acid, which indicates that MoO₄ ^2-Spectral change in BBU aqueous solution cannot be caused, and the single BBU aqueous solution cannot be used for detecting MoO₄ ^2-And (4) concentration.

Comparative example 4

MoO₄ ^2-Does not cause spectral change in BBU aqueous solution, and further verifies whether the space limitation effect of MOFs is enough to lead BBU emission spectrum to follow MoO₄ ^2-The concentration increases. Therefore, BBU @ ZIF-8 is prepared in the invention, and the preparation process is as follows: transferring 0.5mL of 0.01mol/L BBU, weighing 30mmol of 2-methylimidazole, and adding 3.0mL of H₂And (4) carrying out ultrasonic dissolution on O, adding the O into the mixed solution, and uniformly stirring. Weighing 1mmol Zn (NO)₃)₂·6H₂O dissolved in 1mL H₂O, dropwise adding it to the above solution, and adding Zn (NO)₃)₂·6H₂And (3) immediately generating a large amount of precipitate, stirring at room temperature for 10 minutes to stop the reaction, performing centrifugal separation, washing with water and ethanol until the supernatant is almost colorless, and drying to obtain a white BBU @ ZIF-8 product. Weighing 6.0mg BBU @ ZIF-8 ultrasonicDiffused into 3mL of water and then different concentrations of MoO were added₄ ^2-The results are shown in FIG. 17. However, the experimental results show that MoO₄ ^2-And cannot cause the change of the BBU @ ZIF-8 luminescence signal.

Comparative example 5

To further verify Fe₃O₄Whether or not to affect MoO₄ ^2-The detection result shows that the BBU @ Fe is prepared by the invention₃O₄@ ZIF-8, which is prepared by the following steps: 0.5mL of 0.01mol/L BBU and 0.5mL of Fe prepared as described above were removed₃O₄Magnetic ions are fully and uniformly mixed. Then 30mmol of 2-methylimidazole are weighed out and 3.0mL of H are added₂And (4) carrying out ultrasonic dissolution on O, adding the O into the mixed solution, and uniformly stirring. Weighing 1mmol Zn (NO)₃)₂·6H₂O dissolved in 1mL H₂O, dropwise adding it to the above solution, and adding Zn (NO)₃)₂·6H₂A large amount of precipitate is generated immediately, then the reaction is stopped after stirring for 10 minutes at room temperature, magnetic separation, water washing and ethanol washing are carried out until the supernatant is almost colorless, and the soil gray BBU @ Fe is obtained after drying₃O₄@ ZIF-8 product. 6.0mg BBU @ ZIF-8 is weighed and ultrasonically diffused into 3mL water, and then MoO with different concentrations is added₄ ^2-The results are shown in FIG. 18. However, the experimental results show that MoO₄ ^2-Cannot cause BBU @ Fe₃O₄@ ZIF-8 luminescence signal change.

Comparative example 6

BBU@Fe₃O₄@ ZIF-8 is not useful for detecting MoO₄ ^2-Of BBU/RhoB @ Fe, thus further inferring BBU/RhoB @ Fe₃O₄@ ZIF-8 for detecting MoO₄ ^2-Is the result of the synergistic effect of BBU and RhoB, and is therefore directly configured next 10^-5A mixed aqueous solution of BBU and RhoB in mol/L is used for titrating MoO₄ ^2-The experimental results are shown in FIG. 19. However, MoO₄ ^2-Also, the fluorescence spectrum of the mixed aqueous solution of BBU and RhoB cannot be changed, which indicates that BBU/RhoB @ Fe in the present invention₃O₄Application of @ ZIF-8 probe material in detection of MoO₄ ^2-The concentration must be the result of the synergistic effect of BBU, RhoB and ZIF-8 MOFs.

Comparative example 7

BBU/RhoB @ Fe in the fluorescent probe material of the invention₃O₄@ ZIF-8 preparation of BBU/Rho6G @ Fe by replacing RhoB with rhodamine 6G₃O₄@ ZIF-8 for detecting MoO₄ ^2-And (4) concentration. BBU/Rho6G @ Fe₃O₄@ ZIF-8 is prepared as follows: 0.5mL of 0.01mol/L BBU, 0.5mL of 0.01mol/L rhodamine 6G and 0.5mL of the Fe prepared above₃O₄Magnetic ions are fully and uniformly mixed. Then 30mmol of 2-methylimidazole are weighed out and 3.0mL of H are added₂And (4) carrying out ultrasonic dissolution on O, adding the O into the mixed solution, and uniformly stirring. Weighing 1mmol Zn (NO)₃)₂·6H₂O dissolved in 1mL H₂O, dropwise adding it to the above solution, and adding Zn (NO)₃)₂·6H₂O is immediately generated with a large amount of precipitate, then the reaction is stopped after stirring for 10 minutes at room temperature, the magnetic separation, the water washing and the ethanol washing are carried out until the supernatant is almost colorless, and the pink BBU/Rho6G @ Fe is obtained after drying₃O₄@ ZIF-8 product. Taking 6.0mg BBU/Rho6G @ Fe₃O₄@ ZIF-8 ultrasonic diffusion into 3mL of water, followed by the addition of MoO at various concentrations₄ ^2-The results are shown in FIG. 20. However, the experimental results show that MoO₄ ^2-Does not cause BBU/Rho6G @ Fe₃O₄@ ZIF-8 luminescence signal change.

Comparing Rho6G with RhoB, the biggest difference between Rho6G and RhoB is that RhoB contains carboxyl functional group, and Rho6G does not contain carboxyl group. BBU contains just ortho hydroxyl, MoO₄ ^2-Coordinates with hydroxyl in BBU and carboxyl in Rho6G, and enables the rigid planar structure of BBU to be enhanced under the ZIF-8MOFs space confinement, thereby causing the luminescent signal of BBU to be enhanced. Thus, in summary, for MoO₄ ^2-When the concentration is detected, BBU, RhoB and MOFs materials need to act synergistically. BBU, RhoB, mixed water solution of BBU + RhoB, and BBU @ ZIF-8, BBU @ Fe₃O₄@ ZIF-8 and BBU @ Rho6G @ Fe₃O₄@ ZIF-8 all to MoO₄ ^2-There is no response.

Comparative example 8

The present application has tried various methods to prepare Fe₃O₄The method comprises (1) adding FeCl to ethylene glycol₃Sodium citrate and sodium acetate, dissolving and mixing uniformly, transferring into a high-temperature reaction kettle, and obtaining a black product Fe through a hydrothermal reaction₃O₄Cooling to room temperature after the reaction is finished, collecting the product through magnetic separation, washing with pure water and absolute ethyl alcohol respectively, and drying to obtain magnetic Fe₃O₄(ii) a (2) Dissolving 2mmol of ferric triacetylacetone in a mixed solvent of 10mL of benzyl ether and 10mL of oleylamine, reacting for 1h at 110 ℃, then heating to 300 ℃ for reacting for 2h, cooling to room temperature, then adding 50mL of ethanol solution, carrying out magnetic separation, washing with ethanol, drying, and then obtaining the magnetic Fe₃O₄The nanoparticles were re-diffused into 1.0mL of oleic acid for further use. (3) FeCl is added₃·6H₂O(75mL，134mmol L^-1) And FeCl₂·4H₂O(75mL，67mmol L^-1) Then, NaOH solution (2mol L) was gradually added dropwise^-130mL) is heated to 60 ℃, ultrasonic reaction is carried out for 1h, products are collected through magnetic separation after the reaction is finished, and the products are respectively washed and dried by pure water and absolute ethyl alcohol to obtain magnetic Fe₃O₄. Fe obtained by the above preparation method₃O₄It could not be loaded into the ZIF-8 pore channels in the aqueous phase.

The invention is not limited to the specific technical solutions described in the above embodiments, and all technical solutions formed by equivalent substitutions are within the scope of the claims of the invention.

Claims

1. For MoO₄ ^2-The preparation method of the metal organic framework MOFs composite material for concentration detection is characterized by comprising the following steps of: the method comprises the following steps:

(2) weighing the product obtained in the step (1)Fe₃O₄Adding two fluorescent reagents rhodamine B (RhoB) and fluorescent Brightener BBU (BBU) with different emission wavelengths into nanoparticles, adding 2-methylimidazole solution required by synthesis of metal organic framework materials, uniformly dispersing by ultrasonic wave, and adding Zn (NO)₃)₂·6H₂O, stirring for 10-15 minutes at room temperature, then carrying out magnetic separation, washing and drying to obtain the MoO₄ ^2-Detected proportional metering type metal organic framework BBU/RhoB @ Fe₃O₄@ ZIF-8 composite material; said Fe₃O₄The addition amount of (A) is 0.2-1.0 mL; the molar ratio of the BBU to the rhodamine 6G is 1: 10-10: 1; zn (NO)₃)₂·6H₂The molar ratio of O to 2-methylimidazole is 1: 10-1: 35.

2. The composition of claim 1 for MoO₄ ^2-The preparation method of the metal organic framework MOFs composite material for concentration detection is characterized by comprising the following steps of: the method comprises the following steps: zn (NO)₃)₂·6H₂The molar ratio of O to 2-methylimidazole is 1: 30.

3. The composition of claim 1 for MoO₄ ^2-The preparation method of the metal organic framework MOFs composite material for concentration detection is characterized by comprising the following steps of: preparation of magnetic Fe₃O₄The nanoparticle method is as follows: 80mL of distilled water was added with FeCl₂·4H₂O (0.86g) and FeCl₃·6H₂O(2.36g)，N₂To the mixture was added dropwise 5mL of aqueous ammonia (25 wt%), heated to 80 deg.C, stirred for 1h, washed several times with water, and dispersed in 20mL of water. Then adding 1mL of polyvinylpyrrolidone aqueous solution containing 200mg, stirring at room temperature for 24h, and collecting Fe by magnetic separation after the reaction is finished₃O₄The nanoparticles were washed several times with water and then dispersed into 30mL of water for further use.

4. The preparation method of the metal-organic framework material with nitenpyram identification and detection function according to claim 1, characterized in that: said Fe₃O₄The addition amount of (A) is 0.5 mL; the molar ratio of BBU to RhoB is 1: 1.

5. The metal-organic framework material with nitenpyram recognition detection is prepared according to the method of any one of claims 1-4.

6. The use of the metal-organic framework material with nitenpyram recognition detection according to claim 5, characterized in that: the metal organic framework material with magnetic separation and dual-wavelength proportion metering is used for selectively identifying MoO₄ ^2-Application of the aspect.

7. The use of the metal-organic framework material with nitenpyram recognition detection according to claim 6, characterized in that: the metal organic framework material with nitenpyram identification detection function is used for MoO in water₄ ^2-Selective and highly sensitive recognition, and can recover the probe material by simple separation of an applied magnetic field.