CN113045591A

CN113045591A - Double-molecular rhodamine fluorescent probe R6G-PA and preparation method and application thereof

Info

Publication number: CN113045591A
Application number: CN202110388748.3A
Authority: CN
Inventors: 韩波; 张苗苗; 王望; 张玉琦
Original assignee: Yanan University
Current assignee: Yanan University
Priority date: 2021-04-12
Filing date: 2021-04-12
Publication date: 2021-06-29

Abstract

The invention provides a bimolecular rhodamine fluorescent probe R6G-PA and a preparation method and application thereof, relating to the technical field of organic synthesis and comprising the following steps: slowly adding the rhodamine 6G ethanol solution into ethylenediamine, heating and refluxing until all fluorescence disappears, performing suction filtration, washing, and recrystallizing with ethanol to obtain a white solid, namely rhodamine 6G ethylenediamine; and (3) dissolving the rhodamine 6G ethylenediamine obtained in the step S3 in absolute ethyl alcohol, adding terephthalaldehyde, performing reflux reaction until the raw materials disappear, stopping the reaction, cooling to room temperature, performing suction filtration, washing with absolute ethyl alcohol and water for three times respectively, and drying to obtain a white solid, namely the fluorescent probe R6G-PA. The fluorescent probe prepared by the invention has high selectivity and good anti-interference capability, and can be used for resisting Fe in solution³⁺Is not influenced by Al in solution during detection³⁺、Cu²⁺、Ag⁺、Ca²⁺、Cd²⁺、K⁺、Na⁺、Mg²⁺、Ni²⁺、Zn²⁺、Co²⁺Etc.

Description

Double-molecular rhodamine fluorescent probe R6G-PA and preparation method and application thereof

Technical Field

The invention relates to the technical field of organic synthesis, and particularly relates to a bimolecular rhodamine fluorescent probe R6G-PA, and a preparation method and application thereof.

Background

Iron is the second highest element of the earth's crust, Fe³⁺It is one of the trace elements essential for human body, and it is widely available in nature and plays an important role in human metabolism. However, excessive intake of Fe³⁺Can cause damage to liver, kidney and DNA, and if the intake is insufficient, the diseases such as dyspnea and anemia can also be caused. Therefore, the development of a high-sensitivity and high-selectivity iron ion detection system is of great significance.

Detection of Fe at present³⁺The probe materials used include organic dyes, carbon quantum dots, gold nanoparticles, and the like. The organic micromolecule colorimetric/fluorescent probe draws wide attention of scholars at home and abroad due to the advantages of simple design, rapid detection, high sensitivity, low detection limit and the like. In organic small-molecule colorimetric/fluorescent probes represented by coumarins, naphthalimides, cyanines, rhodamines and the like, rhodamine B and rhodamine 6G have excellent optical and chemical characteristics. Such as long absorption and emission wavelengths, high molar absorption coefficient, and high quantum yield, in addition to the closed cyclic amide structure, mostly without color, the fluorescence intensity is very low, and in the presence of strong acid or specific metal ions, the lactam ring is opened, accompanied by macroscopic color change, so as to realize rapid detection, and at the same time, the fluorescence intensity is increased, so that the 'off-on' type fluorescence sensor makes the ion detection simpler. Rhodamine-based probes enable dual channel detection of one or more analytes by providing two different spectral responses through colorimetry/fluorescence. In addition, the paramagnetic property of iron ions makes most of Fe³⁺The fluorescent probe is quenched. Therefore, the development of an OFF-ON colorimetric/fluorescent response type iron ion probe based ON rhodamine B and rhodamine 6G with excellent spectral performance has important significance for the detection of iron ions.

Disclosure of Invention

In order to solve the problems, the invention provides a bimolecular rhodamine fluorescent probe R6G-PA, a preparation method and application thereof.The invention utilizes the nucleophilic addition reaction of rhodamine 6G ethylenediamine and terephthalaldehyde to synthesize Fe which takes aromatic hydrocarbon as an axis and contains two symmetrical rhodamine 6G frameworks³⁺Fluorescent probe R6G-PA. The probe can react with Fe in solution³⁺And (3) carrying out coordination according to the stoichiometric ratio of 1:2, inducing the ring opening of the lactam ring in the probe, so that the skeleton of the probe molecule is changed, the color of the solution is changed into orange red, and strong green fluorescence is emitted at 560 nm. Even under the interference of other ions, the Fe-Fe complex still shows³⁺High selectivity and sensitivity, and can be used as a naked eye probe and a fluorescence turn-on probe to specifically detect Fe³ ⁺Convenient, quick and high accuracy.

In order to achieve the above object, the first technical solution adopted by the present invention is: a bimolecular rhodamine fluorescent probe R6G-PA, wherein the structural formula of the bimolecular rhodamine fluorescent probe R6G-PA is shown as follows:

。

the second technical scheme adopted by the invention is as follows: the invention discloses a preparation method of a bimolecular rhodamine fluorescent probe R6G-PA, which comprises the following steps:

s1 reacting rhodamine 6G with ethylenediamine in an ethanol solution to generate rhodamine 6G ethylenediamine;

s2: in ethanol solution, rhodamine 6G ethylenediamine and terephthalaldehyde react to generate a fluorescent probe R6G-PA.

Further, the method comprises the following steps:

s3: slowly adding the rhodamine 6G ethanol solution into ethylenediamine, heating and refluxing until all fluorescence disappears, performing suction filtration, washing, and recrystallizing with ethanol to obtain a white solid, namely rhodamine 6G ethylenediamine;

specifically, rhodamine 6G ethanol solution is slowly added into ethylenediamine, reflux reaction is carried out for 12 hours at 85 ℃, TLC is adopted to track the reaction progress until all fluorescence disappears, the reaction is finished, suction filtration is carried out, the obtained solid is washed with water, and the crude product obtained by washing with water is recrystallized with ethanol to obtain rhodamine 6G ethylenediamine.

S4: and (3) dissolving the rhodamine 6G ethylenediamine obtained in the step S3 in absolute ethyl alcohol, adding terephthalaldehyde, performing reflux reaction until the raw materials disappear, stopping the reaction, cooling to room temperature, performing suction filtration, washing with absolute ethyl alcohol and water for three times respectively, and drying to obtain a white solid, namely the fluorescent probe R6G-PA.

Dissolving rhodamine 6G ethylenediamine in absolute ethyl alcohol until the rhodamine 6G ethylenediamine is completely dissolved, adding terephthalaldehyde, performing reflux reaction for 24 hours, tracking the reaction process by adopting TLC (thin layer chromatography) until the reaction is completely reacted, cooling to room temperature, performing suction filtration, washing with absolute ethyl alcohol and water for three times respectively, and drying to obtain the fluorescent probe R6G-PA.

Further, in step S1, the mass ratio of rhodamine 6G to ethylenediamine added is 2: 1.

Furthermore, in the step S2, the mass ratio of the rhodamine 6G ethylenediamine to the terephthalaldehyde is 6.8: 1.

the third technical scheme adopted by the invention is as follows: the invention discloses a bimolecular rhodamine fluorescent probe R6G-PA for detecting Fe³⁺The use of (1).

The fourth technical scheme adopted by the invention is as follows: the invention relates to a bimolecular rhodamine fluorescent probe R6G-PA for preparing and detecting Fe in liquid³⁺The use of the reagent of (1).

Further, the liquid contains Fe³⁺Or blood.

The invention has the beneficial effects that:

compared with the prior art, the bimolecular rhodamine fluorescent probe R6G-PA prepared by the invention has the following advantages:

one, high selectivity and good anti-interference ability, and Fe in solution³⁺Is not influenced by Al in solution during detection³ ⁺、 Cu²⁺、Ag⁺、 Ca²⁺、 Cd²⁺、 K⁺、 Na⁺、 Mg²⁺、Ni²⁺、 Zn²⁺、 Co²⁺Etc.

Secondly, the detection limit is low: detection by over ultraviolet absorption and fluorescence spectrophotometryMeasuring Fe³⁺The lowest detection limits of (D) were 0.1. mu.M and 0.027. mu.M, respectively.

Thirdly, detecting effect visible to naked eyes: in the case of using the probe pair of the present invention for Fe³⁺During detection, Fe can be observed without other tools³⁺R6G-PA is added to turn pink.

Fourthly, the response speed is high: R6G-PA and Fe³⁺Obvious reaction easily occurs within 2 min.

In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention.

FIG. 1 is a synthetic scheme of a fluorescent probe R6G-PA according to an embodiment of the present invention;

FIG. 2 shows the NMR spectrum of a fluorescent probe R6G-PA according to an embodiment of the present invention;

FIG. 3 is a nuclear magnetic resonance carbon spectrum of fluorescent probe R6G-PA according to an embodiment of the present invention;

FIG. 4 is an infrared spectrum of fluorescent probe R6G-PA according to an embodiment of the present invention;

FIG. 5 is a high resolution mass spectrum of fluorescent probe R6G-PA of the present invention;

FIG. 6 shows the fluorescent probe R6G-PA of the present invention with Al added³⁺/Fe³⁺The absorbance and the fluorescence intensity of the solution with different pH values are obtained before and after, wherein a is the absorbance, and b is the fluorescence intensity;

FIG. 7 is the variation of absorbance and fluorescence intensity of R6G-PA with different metal ions added in the example of the present invention, where a is the absorbance, b is the fluorescence intensity, c is the color variation of the probe solution after different ions are added, and d is the optical photograph of the probe solution after different ions are added under a 365nm ultraviolet lamp;

FIG. 8 shows the fluorescent probe R6G-PA of this embodiment with Fe added³⁺Fluorescence intensity at 560nm of front and rear metal ions, wherein 1 is Al ³⁺2 is Cu²⁺And 3 is Ag⁺And 4 is Ca²⁺And 5 is Cd ²⁺6 is K⁺7 is Na ⁺8 is Mg²⁺9 is Ni ²⁺10 is Zn²⁺11 is Co ²⁺12 is Hg²⁺13 is Ba ²⁺14 is a metal ion mixed solution listed as 1 to 13;

FIG. 9 shows the addition of 50 μ M Fe in the examples of the present invention³⁺The absorption spectrum and the fluorescence spectrum of the post-R6G-PA are shown along with the time, wherein a is the absorption spectrum, and b is the fluorescence spectrum;

FIG. 10 shows the concentration of Fe in 20 μ M R6G-PA solution of the present invention³⁺Wherein a is a light absorption spectrum and c is a fluorescence spectrum; b is different Fe³⁺Absorbance at 530nm at concentration, d is different Fe³⁺Fluorescence intensity at 560nm at concentration;

FIG. 11 shows the reaction of R6G-PA with Fe in Tris-HCl buffer solution according to an embodiment of the present invention³⁺Job curve of the ion;

FIG. 12 shows the alternative addition of Fe to a solution of R6G-PA in accordance with an embodiment of the present invention³⁺And the fluorescence intensity and fluorescence spectrum at 560nm after EDTA, a is the fluorescence intensity, b is the fluorescence spectrum;

FIG. 13 is Fe according to an embodiment of the present invention³⁺And a binding mechanism diagram of R6G-PA.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The reagent solutions used in the following examples of the present application were prepared as follows:

preparing an acetonitrile solution of the R6G-PA probe: weighing a certain amount of R6G-PA prepared in example 1, dissolving in anhydrous acetonitrile, performing ultrasonic dissolution for 30s, and preparing a solution with the concentration of 100 mu M.

Preparing a metal ion stock solution: weighing a certain amount of Pb (NO)₃)₂、AgNO₃、Ba(NO₃)₂、Ca(NO₃)₂、Cu(NO₃)₂、 Cd(NO₃)₂、Fe(NO₃)₃、Hg(NO₃)₂、KNO₃、Mg(NO₃)₂、NaNO₃、Ni(NO₃)₂、Co(NO₃)₂、Zn(NO₃)₂All dissolved by three times of water to prepare 5mM metal ion stock solution for later use.

Preparing a Tris solution: a certain amount of Tris was taken, and a small amount of deionized water was added to completely dissolve the Tris, and the volume was 50mL with acetonitrile/water (V/V =1:3), thereby obtaining a 10mM Tris solution.

0.1mM HCl formulation: a volume of 12M concentrated HCl was measured and diluted to 0.1mM with deionized water.

Preparation of 10mM Tris-HCl buffer solution: and (3) taking a certain amount of Tris with constant volume, slowly dropwise adding 0.1mM HCl into the Tris to prepare solutions with different pH values, and sealing and storing the solutions in a dark place.

Preparation of 10mM EDTA solution: 0.1821g of EDTA were weighed out and dissolved in deionized water to a volume of 50 mL.

Example 1

Synthesizing rhodamine 6G ethylenediamine: dissolving 1.6G of rhodamine 6G in 50mL of ethanol, then dropwise and slowly adding 0.8G of ethylenediamine, refluxing for 12h at 85 ℃, tracking the reaction progress by TLC until all fluorescence disappears, performing suction filtration, washing with water to obtain a crude product, and recrystallizing with ethanol to obtain a white solid.

Synthesis of R6G-PA: 0.228G of rhodamine 6G ethylenediamine and 20mL of absolute ethanol are added into a 50mL round-bottom flask, 0.0335G of terephthalaldehyde is added after the rhodamine 6G ethylenediamine is completely dissolved, and the mixture is refluxed for 24 hours. And detecting the reaction progress by TLC, stopping the reaction when the raw materials disappear, cooling to room temperature, performing suction filtration, washing with absolute ethyl alcohol and water for three times respectively, and drying to obtain a white solid with the yield of 75%, wherein the reaction formula is shown in figure 1.

Dissolving the obtained probe molecule in CDCl₃The nuclear magnetic test was performed, and the obtained nuclear magnetic resonance hydrogen spectrum is shown in fig. 2:¹H NMR (400 MHz, CHCl₃)δ:ppm7.93(dd,J=10.6,8.3 Hz, 4H), 7.52(s, 4H),7.46–7.39(m,4H),7.02(dd,J= 5.5, 2.3Hz,2H),6.33(s,4H), 6.21(s, 4H),3.45–3.38(m,8H),3.21–3.15(m,8H),1.82(s,12H),1.31(t,J=7.1Hz, 12H)。

the resulting nmr spectrum is shown in fig. 3:¹³C NMR(100 MHz, CHCl₃)δ:ppm 168.4, 161.7,153.8,151.7,147.3,137.8,132.4,131.0,128.5, 127.9, 123.8, 122.7, 117.8, 106.0, 96.6, 65.0, 59.1, 41.2, 38.3, 16.6, 14.7.

the infrared spectrum of the probe molecule of the invention measured by potassium bromide tabletting method is shown in figure 4: IR (KBr), v/cm-1: 3420, 2972, 2369, 1688 (spirolactam ring C = O), 1518, 1376, 1212, 1006, 737. Wherein, 3420cm^-12972cm for the stretching vibration of hydroxyl O-H^-1Is represented by-CH₃and-CH₂Characteristic absorption peak of (a); 1688cm^-1Characterizing a vibration absorption peak for carbonyl; 1518cm^-1Is the characteristic vibration peak of the benzene ring.

The probe R6G-PA was subjected to high resolution mass spectrometry, as shown in FIG. 5, HRMS (ESI) M/z [ M + H ] + calcd. for C64H67N8O4: 1011.5285, found: 1011.5299.

Example 2

Synthesizing rhodamine 6G ethylenediamine: dissolving 16G of rhodamine 6G in 500mL of ethanol, then dropwise and slowly adding 8G of ethylenediamine, refluxing for 12h at 85 ℃, tracking the reaction process by TLC until all fluorescence disappears, performing suction filtration, washing with water to obtain a crude product, and recrystallizing with ethanol to obtain a white solid.

Synthesis of R6G-PA: adding 2.28G of rhodamine 6G ethylenediamine into a 50mL round-bottom flask, adding 200mL of absolute ethanol, adding 0.335G of terephthalaldehyde after the rhodamine 6G ethylenediamine is completely dissolved, and carrying out reflux reaction for 24 hours. And detecting the reaction progress by TLC, stopping the reaction when the raw materials disappear, cooling to room temperature, performing suction filtration, washing with absolute ethyl alcohol and water for three times respectively, and drying to obtain a white solid.

Example 3

To study the pH of the solution, R6G-PA probe molecules prepared herein and Fe were tested³⁺And selecting the optimal pH buffer solution:

adding 200 mu L of probe stock solution into a centrifuge tube, then adding the prepared Tris-HCl buffer solution (pH =2-9) into the centrifuge tube respectively, and then adding 20 mu L of Fe (Fe) (according to the concentration of each pH value) into the solution of each pH value respectivelyNO₃)₃And Al (NO)₃)₃After the solution is fully reacted, the ultraviolet-visible absorption spectrum and the fluorescence spectrum of the solution are measured, and as can be seen from figure 6a, the absorbance of the free probe at 530nm is greatly increased when the pH is 2-3, and the intensity is gradually reduced when the pH is more than 3; at pH > 6, there was little absorption. Adding Fe³⁺After, absorption increased at pH = 6; adding Al³⁺After that, there was a weak absorption enhancement at pH = 6. As can be seen from FIG. 6b, the fluorescence intensity of the free probe at 560nm increased greatly at 2-3, decreased gradually at pH > 3, and quenched at pH > 6. Adding Fe³⁺After, Fe at pH =6³⁺The fluorescence enhancement is obvious; adding Al³⁺After that, very weak fluorescence was shown at pH = 6. Therefore, the fluorescent probe of the present invention requires the targeting of Fe in Tris-HCl solution at pH =6³⁺And (6) detecting.

Example 4

In order to investigate the selectivity of the probe R6G-PA of the invention for metal ion recognition. As shown in FIG. 7a, only Fe was added³⁺And Al³⁺When the metal ion is used, an absorption peak appears at 530nm, and other metal ions cannot cause the change of the absorption spectrum of the R6G-PA. Free R6G-PA has no fluorescence signal in the range of 540-650nm, Fe is added³⁺Then emits strong fluorescence at 560nm, and Al is added³⁺The emission peak at 560nm is very weak and can be ignored, and no interference is caused. It can also be seen from FIG. 7b that other metal ions have a very weak effect on the fluorescence spectrum of R6G-PA. Adding Al³⁺Although the post-absorption and the fluorescence are changed, the change is very weak and can be ignored, so that the R6G-PA can not effectively identify Al³⁺Therefore to Fe³⁺Without significant interference. As shown in FIG. 7c, the photograph under a fluorescent lamp was observed to find that Fe was added³⁺And Al³⁺The solution all turned pink (pink was not visible because the color pattern could not be used in the patent, but was visible to the naked eye during the actual experiment), but Fe³⁺The solution color is obviously better than that of Al³⁺The solution was much darker indicating Fe³⁺Is more strongly absorbed than Al³⁺. As shown in FIG. 7d, only Fe was added under 365nm UV lamp³⁺The solution of (a) emits intense green fluorescence, which may be due to Fe³⁺Ions have high charge number and proper ionic radius, and are more suitable for being coordinated with R6G-PA, so that the fluorescent R6G-PA can be used as a colorimetric/fluorescent probe for specifically recognizing Fe³⁺。

Example 5

To investigate the presence of other metal ions, the fluorescent probes R6G-PA of the present invention were used for Fe³⁺The identification performance of (1). Respectively adding the prepared different metal ion solutions with the particle size of 50 mu M into a 20 mu M R6G-PA probe solution, testing a fluorescence spectrum, and recording the fluorescence intensity at 560 nm; then 10 μ M Fe was added³⁺The fluorescence property test was performed, and the results are shown in fig. 8. Adding Fe³⁺Previously, the fluorescence intensity of the R6G-PA probe solution and the other metal ion solutions was weak, but Fe was added³⁺Fluorescence intensity of the post solution and Fe³⁺The intensities of the single ions are very close to each other, which proves that the existence of other metal ions is opposite to Fe³⁺The detection has no obvious influence, which indicates that the R6G-PA fluorescent probe prepared by the invention detects Fe³⁺The anti-interference capability is stronger.

Example 6

Adding 200 mu L of probe solution into a 2mL centrifuge tube, diluting to 2mL with Tris-HCl buffer solution with pH =6, and adding 20 mu L of Fe³⁺And (4) stock solution. Every 2min, the absorption spectrum and the fluorescence spectrum were measured, as shown in FIG. 9, which is a graph of absorbance at 530nm and fluorescence intensity at 560nm, respectively, as a function of time (the direction of the arrows is the direction of the absorption spectrum and the fluorescence spectrum for time from 0 to 20 min). The solution absorbance and fluorescence intensity increase with time. Finding Fe by spectrogram³⁺After the addition, the absorption intensity and the fluorescence intensity of the R6G-PA are changed rapidly, the change speed is reduced after 14min, the reaction gradually tends to be stable, and the reaction reaches the equilibrium after 20 min. Description of R6G-PA and Fe³⁺Obvious reaction is easy to occur within 2min, which indicates that the probe is easy to react with Fe³⁺The response can be fast.

Example 7

Detection of Fe for exploring R6G-PA³⁺To a 2mL centrifuge tube, 200. mu.L of probe solution was added and buffered with Tris-HCl pH =6The solution is diluted to 2mL, and a series of Fe with different concentrations are added³⁺(0-60 mu M), and after reacting for 20min, measuring absorption and fluorescence spectra. Without addition of Fe³⁺First, R6G-PA was colorless and non-fluorescent, with the addition of Fe³⁺The solution color gradually becomes red with increasing concentration, and the corresponding absorption and fluorescence intensity of R6G-PA also increases, as shown in FIGS. 10a and 10 c. When Fe³⁺When the concentration is increased to 60 mu M, the absorption intensity and the fluorescence intensity of R6G-PA are not changed any more. In the absorption spectrum, Fe³⁺The concentration is in a range of 10-50M and shows a good linear relation with the absorption intensity of R6G-PA, and R²= 0.9859 colorimetric titration for detection of Fe³⁺The lowest detection limit of (d) is 0.1 [ mu ] M, as shown in FIG. 10 b. In the fluorescence spectrum, Fe³⁺The concentration is in the range of 8-45 mu M and has good linear relation with the fluorescence intensity of R6G-PA, and R²= 0.9855, fluorescence detection of Fe³⁺The minimum detection limit of (d) is 0.027 μ M, as shown in FIG. 10 d.

Example 8

To further explore the present invention R6G-PA fluorescent probe for Fe³⁺The detection mechanism of (2) is that a probe and Fe are separately provided³⁺In each concentration ratio of the mixed solution, the molar ratio of the probes R6G-PA to Fe is changed from 1:9 to 9:1³⁺The total concentration of (A) was kept constant at 100. mu.M, and the fluorescence intensities at different stoichiometric ratios were measured. With [ Fe ]³⁺]/([R6G-PA]+[Fe³⁺]) Plotted on the abscissa, corresponding to the fluorescence intensity on the ordinate, as shown in FIG. 11. Fe³⁺From 0.1 to 0.6, the fluorescence intensity gradually increases, and from 0.6 to 0.9, the fluorescence intensity gradually decreases. Therefore, when Fe³⁺The molar fraction of (a) is 0.6, the fluorescence intensity is maximal. Shows that R6G-PA and Fe³⁺The coordination ratio of (A) to (B) is 1: 2.

Ethylenediaminetetraacetic Acid (EDTA) coordinates to many metal ions to form complexes and is therefore commonly used to detect probe reversibility. Adding 200 mu L of probe solution into a 2mL centrifuge tube, diluting to 2mL with Tris-HCl buffer solution with pH =6, and adding 20 mu L of Fe³⁺. After sufficient reaction, the fluorescence intensity was recorded. Adding EDTA solution with the same volume of 10mM to the solution, and fixing Fe in the mixed solution³⁺At a concentration ofAnd (5) testing a fluorescence spectrum, wherein the concentration of EDTA is 100 mu M. Sequentially and alternately adding 20 mu L of Fe into the mixed solution³⁺And 20 muL of 10mM EDTA solution, testing the fluorescence spectrum, and performing cycle test for 5 times. The change in fluorescence intensity is shown in FIG. 12. After EDTA is added for the first time, the fluorescence intensity of the solution is greatly reduced to be nearly no fluorescence, and Fe is added again³⁺The fluorescence is recovered after the reaction, the intensity is close to that of the solution with only Fe³⁺The fluorescence intensity of (2). Indicating that EDTA can convert Fe from R6G-PA-Fe3+ complex³⁺Released and quenched by fluorescence. After the above 5 cycles, the fluorescence intensity is not obviously attenuated, and it can be seen that the R6G-PA fluorescent probe can release the Fe complexed by R6G-PA through the coordination competition of EDTA³⁺And reversible detection is realized.

The lactam ring of the rhodamine class substance is generally colorless and non-fluorescent before being opened, and the lactam ring is opened after being combined with the specific substance. In Fe³⁺In the presence of the probe R6G-PA, the spirolactam is opened, and the color of the solution is changed and the fluorescence is greatly enhanced. The proposed mechanism may be that the spirolactam ring of probe R6G-PA is in Fe³⁺Is induced to open the ring, then is reacted with two equivalents of Fe³⁺In combination, the carbonyl O and imino N in R6G-PA are Fe³⁺The most probable binding site, the specific process is shown in FIG. 13, in which the ring of the spirolactam ring of R6G-PA is opened and then reacted with Fe³⁺The coordination forms a complex, which is an internal cause of the change in the ultraviolet-visible absorption spectrum and the fluorescence.

Example 9

Verifying that probe R6G-PA is used for detecting Fe in water body by taking Yanghe water as real water sample through adopting standard-adding recovery method³⁺And (4) detecting ions. At this time, the concentration of other ions in water is low and is ignored, and EDTA does not affect the determination of the result. mu.L and 200. mu.L of each real water sample and R6G-PA stock solution were mixed and diluted to 2mL by Tris-HCl buffer solution (10mM, pH 6.0) with a concentration of R6G-PA of 20. mu.M. Adding a known concentration of Fe³⁺Ions were added to the solution containing R6G-PA and the real water sample prepared above, respectively. After full reaction, the fluorescence spectrum change is measured, and the measurement is repeated three times. The results are shown in Table 1 with recoveries from 96.47% to 102.04%.

Table 1 shows Fe in water sample³⁺Measurement of (2)

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A bimolecular rhodamine fluorescent probe R6G-PA is characterized in that the structural formula of the bimolecular rhodamine fluorescent probe R6G-PA is as follows:

。

2. the preparation method of the bimolecular rhodamine fluorescent probe R6G-PA as claimed in claim 1, which is characterized by comprising the following steps:

s1: reacting rhodamine 6G and ethylenediamine in an ethanol solution to generate rhodamine 6G ethylenediamine;

3. The preparation method of the bimolecular rhodamine fluorescent probe R6G-PA according to claim 2, which is characterized by comprising the following steps:

4. The method for preparing the bimolecular rhodamine fluorescent probe R6G-PA according to claim 2, wherein the mass ratio of the rhodamine 6G and the ethylenediamine added in the step S1 is 2: 1.

5. The method for preparing the bimolecular rhodamine fluorescent probe R6G-PA according to claim 2, wherein the mass ratio of rhodamine 6G ethylenediamine to terephthalaldehyde added in the step S2 is 6.8: 1.

6. the bimolecular rhodamine fluorescent probe R6G-PA as claimed in claim 1 for detecting Fe³⁺The use of (1).

7. The bimolecular rhodamine fluorescent probe R6G-PA as claimed in claim 1 for preparing Fe in detection liquid³⁺The use of the reagent of (1).

8. Use according to claim 7, wherein the liquid is Fe-containing³⁺Or blood.