CN111484628B - MOFs-zinc material and preparation method and application thereof - Google Patents

Abstract

The invention provides a MOFs-zinc material, the molecular formula of which is Zn (CDC) (BPY)]·DMF·2H₂O, wherein CDC is a 3, 6-carbazole dicarboxylic acid ligand, BPY is a 4,4' -bipyridine ligand, the crystal belongs to I4/mcm space group of tetragonal system, and the crystal is independent Zn²⁺Uses four-coordinate coordination mode to coordinate with two oxygen atoms from two 3, 6-carbazole dicarboxylic acid ligands and two nitrogen atoms from two 4,4' -bipyridyl ligands to form two 3, 6-carbazole dicarboxylic acid ligands and two Zn²⁺A small ring is formed, and then two small rings, four 4,4' -bipyridyl ligands and two Zn are connected²⁺Six vertexes are Zn²⁺The unit cell parameter is alpha-beta-gamma-90 deg. to obtain a cyclic structure,

unit cell volume of

And Z is 32. The invention has the following beneficial effects: use of MOFs-Zn materials for the construction of identifiable Cr₂O₇ ^2‑The fluorescent sensor realizes rapid detection.

Description

MOFs-zinc material and preparation method and application thereof

Technical Field

The invention relates to a zinc MOFs-zinc material, a preparation method and application thereof, belonging to the technical field of sensor preparation.

Background

Chromium is a toxic chemical element and has been widely used in various industrial productions such as printing, electroplating, leather tanning, metal polishing and the like. A large amount of chromium waste has been produced all over the world, seriously raising environmental problems. Chromium is in the form of a highly soluble hexavalent chromate anion (Cr) under many environmental conditions₂O₇ ^2-) There is an excessive intake of these anions with obvious carcinogenesisSex and mutagenicity, resulting in DNA damage and destruction of the human protein and enzyme systems. In addition, chromate anions are a problem in the vitrification of nuclear waste, since they crystallize internally to form spinels. Therefore, monitoring the concentration of chromate anion is of paramount importance in many environmental and industrial applications.

The use of fiber optic wave sensors, and high performance liquid chromatography and atomic absorption spectroscopy are suitable for both qualitative and quantitative analysis in a number of analytical detection methods such as ion chromatography, inductively coupled plasma mass spectrometry (ICP-MS), and high performance liquid chromatography. Among these, fluorescence methods generally require shorter processing times and involve less sample pretreatment, and are therefore of great interest. In the last decade, Metal Organic Frameworks (MOFs) have attracted great interest, and more designable structures have accumulated broad performance application prospects and are often used in the fields of gas adsorption and separation, catalysis, electrochemistry, and the like. Among them, it is not uncommon to construct fluorescence sensors from MOFs.

The MOFs structure is regulated and controlled by replacing a metal center and a ligand in a common mode, and the structure is regulated and controlled by simply changing the acid-base property of a solution under the condition that the proportion of the metal to the ligand is the same, so that the same 'fen' isomer FJU-826 of FJU-82-Zn is prepared. The fluorescence intensity of the MOF is improved, and meanwhile, the construction of the chromium (VI) oxyanion fluorescence sensor of the non-lanthanide MOF is realized.

Disclosure of Invention

The invention aims to solve the problems of the prior art and provides a preparation method for regulating and controlling MOFs structure by simply changing the pH value of a solution and identifiable Cr₂O₇ ^2-The fluorescence sensor of (1).

The invention is realized by the following technical scheme:

the invention provides a MOFs-zinc material, the molecular formula of which is Zn (CDC) (BPY)]·DMF·2H₂O, wherein CDC is a 3, 6-carbazole dicarboxylic acid ligand, BPY is a 4,4' -bipyridine ligand, the crystal belongs to I4/mcm space group of tetragonal system, and the crystal is independent Zn²⁺Is coordinated with two 3, 6-carbazole dicarboxylic acids by four-coordinate coordinationTwo oxygen atoms of the body coordinate with two nitrogen atoms from two 4,4' -bipyridine ligands, with two 3, 6-carbazole dicarboxylic acid ligands and two Zn²⁺A small ring is formed, and then two small rings, four 4,4' -bipyridyl ligands and two Zn are connected²⁺Six vertexes are Zn²⁺α ═ β ═ γ ═ 90 °,

has a volume of

Z＝32。

A preparation method of the MOFs-zinc material comprises the following steps:

dissolving water-soluble zinc salt, 4' -bipyridine and 3, 6-carbazole dicarboxylic acid in dimethylformamide and distilled water, adding a potassium hydroxide aqueous solution, uniformly mixing, and carrying out hydrothermal reaction at 85 ℃ to obtain the zinc-MOFs material.

Preferably, the water-soluble zinc salt is zinc nitrate.

Preferably, the molar ratio of the zinc nitrate to the 4,4' -bipyridine to the 3, 6-carbazole dicarboxylic acid is 1: 1: 1.

preferably, the hydrothermal reaction time is 24 h.

The MOFs-zinc material is used for identifying Cr₂O₇ ^2-The use in a fluorescence sensor.

A method for constructing the fluorescence sensor comprises the following steps:

dissolving MOFs-zinc material in distilled water, and fixing the volume to 0.5mg/mL of mixed solution;

taking a plurality of 1mL of mixed solution, and respectively adding Cr with different known concentrations₂O₇ ^2-After the solution is dissolved, the volume is uniformly determined to be 10mL, and a plurality of standard samples are obtained;

performing fluorescence luminosity detection on each standard sample, setting the excitation wavelength of fluorescence to be 295nm and the response time to be 0.1s, and obtaining the fluorescence absorption intensity and Cr₂O₇ ^2-Concentration relationship, and fluorescence absorption intensity and Cr₂O₇ ^2-Concentrations were plotted as standard curves.

Compared with the prior art, the invention has the following beneficial effects:

the invention utilizes a method for simply changing the pH value of the solution to realize the rapid regulation and control of the fluorescence property of the MOFs structure lifting material, and prepares the same 'molecule' isomer FJU-826 of FJU-82-Zn.

FJU-826 was used next to construct identifiable Cr₂O₇ ^2-The fluorescent sensor realizes rapid detection. The linear range of the sensor is 0.5-0.9 mmol/L and 5-90 mu mol/L, and the detection limit is 1.2 mu M. The sensor also has good stability, reproducibility and anti-interference performance, and a standard recovery rate experiment is carried out on an actual water sample, so that the recovery rate is 96.0-98.7%, and relatively ideal performance is obtained.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a coordination environment, a construction mode and a three-dimensional structure analysis of FJU-826 crystal structures of example 1 of the present invention;

FIG. 2 is a coordination environment, a construction manner and a three-dimensional structure analysis of FJU-82-Zn crystal structure of comparative example 1 of the present invention;

FIG. 3 is an infrared spectroscopic analysis of FJU-82-Zn and FJU-826 of comparative example 1 of the present invention;

FIG. 4 is an optical microscope image of FJU-82-Zn and FJU-826 of comparative example 1 of the present invention under UV irradiation;

FIG. 5 is the solid fluorescence test results of FJU-82-Zn and FJU-826 of comparative example 1 of the present invention;

FIG. 6 shows the fluorescence spectra of FJU-826 in different solvents according to example 2 of the present invention;

FIG. 7 is an XRD spectrum of FJU-826 soaked in different solvents according to example 2 of the present invention;

FIG. 8 is a fluorescence spectrum of FJU-826 in different anionic aqueous solutions according to example 3 of the present invention;

FIG. 9 shows FJU-826 of example 4 of the present invention with Cr concentrations varied₂O₇ ^2-Fluorescence response spectra in aqueous solution;

FIG. 10 is a linear fit curve of example 4 of the present invention;

FIG. 11 is an anti-interference experiment of FJU-826 fluorescent sensor against anions and amino acids according to example 5 of the present invention;

FIG. 12 is an anti-interference experiment of FJU-826 fluorescent sensor of example 5 of the present invention with positive ions;

FIG. 13 shows Cr-impregnated steel sheets in example 6 of the present invention₂O₇ ^2-Fluorescence microscopy images of FJU-826 of aqueous solution;

FIG. 14 shows Cr immersion method in example 6 of the present invention₂O₇ ^2-XRD spectrograms of FJU-826 before and after the aqueous solution;

FIG. 15 is a graph of the UV-VIS absorption spectra of various aqueous anionic solutions of example 6 of the present invention;

FIG. 16 shows Cr in example 6 of the present invention₂O₇ ^2-Ultraviolet-visible absorption spectrum of the aqueous solution and fluorescence spectrum of FJU-826 in the aqueous solution.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

Example 1

The embodiment provides a preparation method of MOFs-zinc material, which specifically comprises the following steps:

zinc nitrate hexahydrate (Zn (NO)₃)₂·6H₂O,0.1mmol,29.8mg), 4,4' -bipyridine (BPY,0.1mmol,15.6mg),3, 6-carbazole dicarboxylic acid (CDC,0.1mmol,25.5mg) were dissolved in dimethylformamide (DMF,4mL) and distilled water (2mL), and 1mL of 1.0M KOH aqueous solution was added to obtainThe mixture was clear. Then, the transparent mixture is sealed in a transparent glass bottle and reacted for 24h at 85 ℃ to obtain a light yellow blocky crystal MOFs-zinc material, which is recorded as FJU-826 and has a molecular formula of [ Zn (CDC) (BPY)]·DMF·2H₂O, yield 60%. The elemental analysis result shows that the experimental value is C, 55.80; h, 4.53; n,10.03, theoretical value C, 55.40; h, 4.27; n, 10.05.

Diffraction intensity data for MOFs-zinc materials was collected by an Agilent Technologies Super Nova single crystal diffractometer. The MOFs-zinc material correlation crystal data and structure refinement parameters are listed in Table 1. The single crystal X-ray diffraction analysis result shows that the MOFs-zinc material belongs to I4/mcm space group of tetragonal system.

TABLE 1 relevant Crystal data for MOFs-Zinc materials (FJU-826)

The crystal structure of MOFs-zinc material is analyzed in detail, as shown in FIG. 1a, the crystallographically independent Zn²⁺Four coordinate coordination is used to coordinate two oxygen atoms (from two CDCs) and two nitrogen atoms (from two BPY). FJU-826 in the framework, two CDC ligands and two Zn²⁺Form a small ring, and then two small rings and four BPY ligands are connected with two metal Zn²⁺Six vertexes are Zn²⁺Like the six-membered ring structure shown in fig. 1 b. Each six-membered ring structure forms a single layer structure of a honeycomb two-dimensional grid by sharing metal vertices, each of which is shared by three six-membered rings, as shown in fig. 1 c. When the stacked pattern of parallel grids is viewed from the c-axis direction, a slip phenomenon is observed between adjacent parallel grids, as shown in fig. 1 d. Referring to FIG. 1e, the single-layer structure of the two-dimensional grid is topologically extracted, and the MOFs-zinc material is analyzed by Topos 4.0 software to be hcb type topology, wherein the nodes correspond to metal Zn²⁺. Parallel grids which are also slipped and piled up in the same interlayer are inserted and piled up in the vertical direction of the piled-up parallel grid structure, so that a three-dimensional frame structure of the MOFs-zinc material is formed, and the three-dimensional frame structure is shown in figure 1 f.

Comparative example 1

This comparative example differs from the examples only in that no aqueous KOH solution was added to the hydrothermal reaction and the resulting product was designated as the MOFs-zinc material isomer, noted FJU-82-Zn. Diffraction intensity data for isomers of MOFs-zinc materials was collected by an Agilent Technologies SuperNova single crystal diffractometer. The MOFs-zinc material isomer related crystal data and structure refinement parameters are listed in Table 2.

TABLE 2 relevant Crystal data for MOFs-Zinc Material isomers (FJU-82-Zn)

3, 6-carbazole dicarboxylic acid (CDC) and 4,4' -Bipyridine (BPY) in a mixed solvent of DMF and water with Zn (NO)₃)₂Reaction synthesis FJU-82-Zn with the chemical formula [ Zn (CDC) (BPY)]·DMF·3H₂And O. After KOH solution is added into the mixed solvent, FJU-826 which has the chemical formula of [ Zn (CDC) (BPY) are synthesized]·DMF·2H₂And O. FJU-82-Zn and FJU-826 were found to be isomers except for the solvent molecule. The single crystal X-ray diffraction analysis result shows that FJU-82-Zn belongs to the P-1 space group of the triclinic system. A detailed analysis FJU-82-Zn crystal structure, shown in FIG. 2a, of crystallographically independent Zn²⁺With four oxygen atoms (from two CDCs) and two nitrogen atoms (from two BPY) coordinated in a hexacoordinated coordination. FJU-82-Zn framework, firstly consisting of CDC and Zn ligands²⁺One-dimensional binuclear metal chains are formed as shown in fig. 2b, and bridged by ligand BPY to form a single-layer structure of a two-dimensional rhomboid lattice as shown in fig. 2 c. The two-dimensional rhombic lattice forms a three-dimensional supramolecular configuration by pi … pi stacking effect between adjacent ligands (CDC) in different two-dimensional layers as shown in FIG. 2d, and the distance between the centers of gravity of two CDC molecules is

As shown in fig. 2 e.

The infrared spectra of FJU-82-Zn and FJU-826 were measured by Fourier transform Infrared Spectroscopy (FTIR), and it can be seen from FIG. 3 that the infrared spectra are very similar. This is mainly thatSince FJU-82-Zn and FJU-826 both use CDC and BPY as organic linkers, Zn²⁺Two examples of MOFs synthesized as metal centers have the same composition but different structures. According to the results obtained, 3500cm^-1The nearby peak corresponds to N-H stretching vibration, 3300cm^-1The left and right peaks correspond to O-H stretching vibration. About 1650cm^-1And 1370cm^-1The peaks at (a) correspond to C ═ O asymmetric stretching vibration and C — O symmetric stretching vibration on the carboxyl group, respectively. 3050cm^-1Nearby peaks and 1490cm^-1The adjacent peaks respectively belong to a C-H characteristic peak and a C ═ C stretching vibration on the benzene ring. Based on the above infrared analysis results, it was shown that FJU-82-Zn and FJU-826 both contain CDC and BPY related functional groups.

The prepared FJU-82-Zn and FJU-826 were placed on clean glass slides, respectively, irradiated with UV light, and observed under an optical microscope. The rod-shaped yellowish crystals in FIG. 4a are FJU-82-Zn, and the block-shaped crystals emitting bluish light in FIG. 4b are FJU-826. Moreover, the strongest emission peak of FJU-826 was found by solid fluorescence test to be around 520nm with intensity much greater than FJU-82-Zn (FIG. 5) at an excitation wavelength of 295 nm. Because the CDCs of adjacent ligands in the FJU-82-Zn crystal structure are stacked mutually, and two CDC ligands and metal ions in FJU-826 are connected to form a small ring to form a coplanar surface, the planes of two small rings which are nearest to each other are perpendicular to each other, and no stack exists, so that the fluorescence properties of the two small rings are greatly different.

Therefore, by comparing example 1 with comparative example 1, FJU-826 upgraded the crystal system compared with FJU-82-Zn.

Example 2

The embodiment relates to a selection method of FJU-826 fluorescence sensor solvent system, which comprises the following steps:

grinding prepared FJU-826 into superfine powder with agate mortar, respectively weighing 4mg of powder and 6mL of different solvents, and mixing, and performing ultrasonic treatment for 30min to ensure that FJU-826 are uniformly dispersed in each solvent. Setting test parameters: the excitation wavelength was 295nm, the response time was 0.1s, and the results are shown in FIG. 6. FJU-826 also differ in their fluorescent properties in different solvents. Among them, the fluorescence of water is best among six solvents, methanol, ethanol, tetrahydrofuran, ethyl acetate and DMF, in the vicinity of 380 nm. In addition, FJU-826 were soaked in different solvents and the samples recovered after one day were filtered and dried for powder diffraction testing, as shown in FIG. 7, and FJU-826 were found to be stable in these six solvents when compared to the simulated powder pattern. Based on FJU-826, the fluorescence response signal in water is strongest, and the water environment of the practical application system is more, so the water environment is selected as the detection system for constructing the fluorescence sensor.

Example 3

The embodiment relates to determination of FJU-826 fluorescence sensor detection object, which specifically comprises the following steps:

placing 25mg of FJU-826 into a 50.00mL volumetric flask, adding distilled water to constant volume, and ultrasonically treating in a cold water bath for 30min to uniformly disperse. Then 1.00mL of the dispersion liquid is put into different 10mL volumetric flasks, 1.00mL (0.1mol/L) of different anion aqueous solutions are transferred, finally, the volume is determined by distilled water, and the solution is ultrasonically treated by a cold water bath for 30min to ensure that FJU-826 is uniformly dispersed in the solution. Setting test parameters: the excitation wavelength was 295nm and the response time was 0.1 s. As a result, as shown in FIG. 8, the fluorescence intensity was significantly different under the condition that the same concentration of different anions was 0.01mol/L, wherein Cr is present₂O₇ ^2-The influence of ions is large, and the quenching rate is far higher than that of other anions. Thus selecting Cr₂O₇ ^2-The ions are the object of detection.

Example 4

The embodiment relates to determination of detection linear range and detection limit of FJU-826 fluorescence sensor system, which comprises the following steps:

FJU-826 was weighed into a volumetric flask and made up to 0.5mg/mL with distilled water. After the mixed solution is subjected to ultrasonic dispersion, respectively taking 1.00mL of the mixed solution into 10mL volumetric flasks, and preparing the mixed solution into the volumetric flasks containing Cr with different concentrations₂O₇ ^2-The mixed solution of (1) is treated by cold water bath and ultrasonic treatment for 30 min. Setting test parameters: the excitation wavelength was 295nm, the response time was 0.1s, and the test results are shown in FIG. 9. The results of the linear fitting are shown in FIG. 10, Cr₂O₇ ^2-Fluorescence of the mixture of ion concentration and FJU-826The light intensity was linearly related over two ranges, I-1308.65 c (mmol/L) +1366.78, R, between 0.5mmol/L and 0.9mmol/L²0.986, with a minimum detection limit of 0.10 mmol/L; the linear relationship between 5 to 90 μmol/L is-18.57 c (μmol/L) +3140.99, R²The lowest detection limit was 1.20. mu. mol/L, which was 0.999. Compared with other similar Materials (MOFs), the results are shown in the following Table 3, and the detection limit of FJU-826 is relatively excellent in zinc-based MOFs, but has a difference with lanthanide MOFs.

TABLE 3 various luminescent MOFs sensors for Cr in aqueous phase₂O₇ ^2-Comparison of detected Performance

Example 5

This example relates to the evaluation of the detection immunity of the FJU-826 fluorescence sensor system, and the experiment is carried out on a sample containing interferents and 50. mu. mol/LCr₂O₇ ^2-The samples were similarly incorporated with quantitative amounts FJU-826 for fluorescence detection, and the results showed that 100 times as much valine (Val), glycine (Gly), alanine (Ala), and F were present^-、Cl^-、Br^-、SO₃ ^2-、SO₄ ^2-、NO₃ ^-、Li⁺、Mg²⁺、K⁺、Cd ²⁺10 times of I^-、NO₂ ^-Histidine (His), Urea (UA), Homopoly PO₄ ^3-、Na⁺、Ca²⁺、Mn²⁺、Ni²⁺When to Cr₂O₇ ^2-The determination of (2) has no influence (as shown in fig. 11 and fig. 12), and the FJU-826 fluorescence sensor has good anti-interference performance and applicability.

And (3) determination of an actual water sample: similarly, the fluorescent sensing system is constructed by adding quantitative FJU-826, and the standard-adding recovery method is adopted to treat Cr in the actual water sample₂O₇ ^2-And (4) carrying out fluorescence detection on the content. The results are shown in Table 4, Cr₂O₇ ^2-The recovery rate range is 96.0-98.7%, which shows thatFJU-826 construction of fluorescence sensor pair Cr₂O₇ ^2-The detection has practical applicability.

TABLE 4 Cr in actual water sample₂O₇ ^2-Measurement of (average. + -. SD, n is 3)

SD：standarddeviation；ND：notdetected；RSD：relative standarddeviation；

Example 6

FJU-826 Cr 0.01M₂O₇ ^2-After soaking in the aqueous solution for 15 days, filtration, rinsing with distilled water, and observation under a fluorescent microscope. FJU-826 was still a square block of pale yellow crystals as shown in FIG. 13 a. When excitation light is applied, FJU-826 remain as bulk crystals that emit cyan light, as shown in FIG. 13 b. FJU-826 was found to retain its structural stability before and after immersion as shown in FIG. 14 by X-ray powder diffraction testing. Indicates that Cr is present₂O₇ ^2-The aqueous solution did not destroy the FJU-826 structure, and the reason for fluorescence quenching was not due to the structural change of FJU-826.

Soaking Cr₂O₇ ^2-FJU-826 before and after the water solution are subjected to energy dispersive X-ray spectroscopy (EDS) surface scan analysis, and the results are shown in the following table 5, wherein the Cr element content before and after soaking is basically consistent, and the Cr element content belongs to the background interference category. The FJU-826 sample surface after soaking is not adsorbed with Cr₂O₇ ^2-Ions, excluding surface adsorption of Cr₂O₇ ^2-The ion leads to the possibility of fluorescence quenching.

TABLE 5 relevant EDS surface Scan elemental analysis results

Performing ultraviolet absorption spectrum analysis on 0.01M aqueous solution of various anions, and obtaining test results shown in figure 15 and FIG. 16, it was found that Cr was excluded₂O₇ ^2-In addition, the ultraviolet absorption peak range of the tested anion water solution is less than 260 nm. Cr (chromium) component₂O₇ ^2-The UV absorption spectrum of the aqueous solution shows two broad bands (lambda appears at 260, 370 nm)_max). Wherein there is spectral overlap between the absorption peak near 370nm and the fluorescence emission peak of FJU-826, indicating that due to weak interaction between the two, electron energy may be transferred from FJU-826 to the analyte Cr₂O₇ ^2-Thereby inducing a selective quenching phenomenon. No overlap was observed between the spectra of the other anions and the emission peaks from FJU-826, indicating that FJU-826 was associated with Cr₂O₇ ^2-The reason for ion selective quenching. Thus, a static quenching process that causes electron energy transfer due to spectral overlap with the analyte can be considered a viable quenching mechanism in the present case.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

Claims (7)

1. A MOFs-zinc material characterized by the molecular formula Zn (CDC) (BPY)]·DMF·2H₂O, wherein CDC is a 3, 6-carbazole dicarboxylic acid ligand, BPY is a 4,4' -bipyridine ligand, the crystal belongs to I4/mcm space group of tetragonal system, and the crystal is independent Zn²⁺Uses four-coordinate coordination mode to coordinate with two oxygen atoms from two 3, 6-carbazole dicarboxylic acid ligands and two nitrogen atoms from two 4,4' -bipyridyl ligands to form two 3, 6-carbazole dicarboxylic acid ligands and two Zn²⁺A small ring is formed, and then two small rings, four 4,4' -bipyridyl ligands and two Zn are connected²⁺Six vertexes are Zn^{2 +}The unit cell parameter is alpha-beta-gamma-90 deg. to obtain a cyclic structure,

unit cell volume of

Z＝32。

2. A process for the preparation of MOFs-zinc materials as claimed in claim 1, characterized by the following steps:

dissolving water-soluble zinc salt, 4' -bipyridine and 3, 6-carbazole dicarboxylic acid in dimethylformamide and distilled water, adding a potassium hydroxide aqueous solution, uniformly mixing, and carrying out hydrothermal reaction at 85 ℃ to obtain the zinc-MOFs material.

3. The method of claim 2, wherein said water-soluble zinc salt is zinc nitrate.

4. The method of preparing MOFs-zinc materials of claim 3, wherein the molar ratio of zinc nitrate, 4' -bipyridine and 3, 6-carbazole dicarboxylic acid is 1: 1: 1.

5. the method for preparing MOFs-zinc materials according to claim 2, wherein the hydrothermal reaction time is 24 h.

6. A MOFs-zinc material as claimed in claim 1 for identifying Cr₂O₇ ^2-The use in a fluorescence sensor.

7. A method of constructing a fluorescence sensor according to claim 6, comprising the steps of:

dissolving MOFs-zinc material in distilled water, and fixing the volume to 0.5mg/mL of mixed solution;

taking a plurality of 1mL of mixed solution, and respectively adding Cr with different known concentrations₂O₇ ^2-After the solution is dissolved, the volume is uniformly determined to be 10mL, and a plurality of standard samples are obtained;

performing a fluorescence photometry of each of the standardsMeasuring, setting the excitation wavelength of fluorescence at 295nm and the response time at 0.1s to obtain the fluorescence absorption intensity and Cr₂O₇ ^2-Concentration relationship, and fluorescence absorption intensity and Cr₂O₇ ^2-Concentrations were plotted as standard curves.

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