High-sensitivity visual Fe < 3 + > / Al < 3 + > fluorescent probe Rh as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of fluorescent probes, and particularly discloses a high-sensitivity visual Fe < 3 + > / Al < 3 + > fluorescent probe Rh and a preparation method and application thereof.The high-sensitivity visual Fe < 3 + > / Al < 3 + > fluorescent probe Rh is characterized in that cyanuric chloride and sulfanilic acid are used as raw materials, and an intermediate L1 is synthesized through an alkylation reaction; synthesizing an intermediate L2 by using the intermediate L1 and p-hydroxybenzaldehyde as raw materials through alkylation reaction; the intermediate L2 and rhodamine B hydrazide are subjected to a Schiff base reaction, and the triazine-rhodamine B hydrazide derivative fluorescent probe Rh is obtained. According to the fluorescent probe Rh prepared by the invention, the water solubility is increased due to the introduction of a sulfanilic acid group; the fluorescence spectrum test of the probe Rh and 17 common metal ions shows that the probe Rh has a remarkable fluorescence enhancement effect on Fe < 3 + > and Al < 3 + >; an ultraviolet-visible absorption curve test shows that a new peak appears at 560 nm, the absorbance is remarkably increased, and at 350 nm, Fe < 3 + > has an obvious absorption peak but Al < 3 + > does not exist, and Fe < 3 + > and Al < 3 + > can be distinguished.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent probes, in particular to a high-sensitivity visual Fe 3+ / Al 3+ Fluorescent probe Rh, preparation method and application thereof, and application thereof in the detection of water quality standards for drinking water, industry, agriculture, etc. Background Art

[0002] Rhodamine and its derivatives, as on / off fluorescent probes, have high fluorescence quantum yields, large molar extinction coefficients, and long emission and absorption wavelengths in the visible light region. After interacting with different metal ions, the forces formed are different, and rhodamine derivatives will emit different fluorescence and colors. Therefore, rhodamine and its derivatives have great development prospects as probes for detecting heavy metal ions. Based on this, we plan to develop one or several high-sensitivity probes based on rhodamine groups that can be identified by the naked eye, without the aid of any instruments or any professional knowledge background, and can quickly detect whether a certain metal ion in a water sample meets the requirements of drinking water and industrial and agricultural water. We will try to apply it to the prevention of poisoning by one or several metal ions in daily water for residents and industrial and agricultural water. Summary of the invention

[0003] The object of the present invention is to provide a high-sensitivity visual Fe 3+ / Al 3+ Fluorescent probe Rh and its preparation method and application.

[0004] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0005] One of the objects of the present invention is to provide a highly sensitive visual Fe 3+ / Al 3+ Fluorescent probe Rh, the fluorescent probe structure is as follows:

[0006]

[0007] Another object of the present invention is to provide a highly sensitive visual Fe 3+ / Al 3+ The preparation method of the fluorescent probe Rh comprises the following steps:

[0008] S1, using cyanuric chloride and p-aminobenzenesulfonic acid as raw materials to carry out alkylation reaction to synthesize intermediate L1;

[0009] S2, using intermediate L1 and p-hydroxybenzaldehyde as raw materials, synthesizing intermediate L2 by alkylation reaction;

[0010] S3. The intermediate L2 and rhodamine B hydrazide are subjected to a Schiff base reaction to obtain a rhodamine B hydrazide derivative fluorescent probe Rh.

[0011] Furthermore, the step S1 specifically includes:

[0012] S11, weigh 0.03 mol of p-aminobenzenesulfonic acid and put it in a beaker, add 70 mL of deionized water to dissolve it, and at the same time drop 10% anhydrous Na2CO3 solution to make the pH value of the p-aminobenzenesulfonic acid aqueous solution between 6-7 to increase the solubility of p-aminobenzenesulfonic acid in water;

[0013] S12, place the beaker in an ice bath at 0°C and stir continuously; weigh 0.03 mol of cyanuric chloride and dissolve it in 60 mL of acetone solution, place the cyanuric chloride solution in a constant pressure funnel, and drip it into the aqueous solution of p-aminobenzenesulfonic acid at a rate of 2 to 3 drops per second until the dripping is completed, and continue to stir and react for 8 hours; during the reaction, continuously drip 10% anhydrous Na2CO3 solution to adjust the pH value of the reaction so that the solution is neutral;

[0014] S13. After the reaction is completed, the beaker is left to stand for a period of time to allow the precipitate and the solution to separate, and a white solid is obtained by vacuum filtration. The unreacted cyanuric chloride is removed by washing with acetone, and then washed with a large amount of deionized water, and finally a white powder, namely the intermediate L1, is obtained by drying.

[0015] Furthermore, the step S2 specifically includes:

[0016] S21, weigh p-hydroxybenzaldehyde and dissolve it in THF solution, and add triethylamine;

[0017] S22, weigh the intermediate L1 and dissolve it in THF solution, and add it dropwise to the p-hydroxybenzaldehyde solution at a rate of 2 to 3 drops / second under a constant pressure funnel device; after the addition is completed, transfer the reaction container to an ultrasonic cleaner, adjust the temperature to 80°C, and perform ultrasonic reaction for 30 minutes, then stop for 10 minutes, and continue the interval ultrasonic reaction for a total of 120 minutes;

[0018] S23. After the reaction is completed, the reaction vessel is allowed to stand and cool to room temperature, ethanol is added, and under stirring, hydrochloric acid is added to adjust the pH to 6-7, and the mixture is filtered, washed with ethanol, and dried to finally obtain a white powder, namely, intermediate L2. Synthesis route of intermediate L2:

[0019]

[0020] Furthermore, the step S3 specifically includes:

[0021] S31, add intermediate L2, rhodamine B hydrazide and anhydrous methanol to the reaction vessel; stir and reflux, and react at 70-75°C for 12-16h until the solution changes from a suspension to a light red clear liquid;

[0022] S32. The solvent is removed by rotary evaporation to obtain a crude product, ethyl acetate is added for stirring or ultrasonic oscillation is performed to remove excess unreacted Rhodamine B hydrazide, and finally, a white solid, i.e., the fluorescent probe Rh, is obtained by filtration under reduced pressure.

[0023] Synthesis route of fluorescent probe Rh:

[0024]

[0025] Preferably, in step S2, the molar ratio of the intermediate L1, p-hydroxybenzaldehyde and triethylamine is 1:2:10.

[0026] Preferably, in step S23, after the reaction is completed, the reaction solution is concentrated into an oily substance, ethanol is added, and under stirring, hydrochloric acid is added to adjust the pH value.

[0027] Preferably, in step S3, the molar ratio of intermediate L2 to rhodamine B hydrazide is 1:2.1.

[0028] The third object of the present invention is to provide a highly sensitive visual Fe 3+ / Al 3+ The application of fluorescent probe Rh in environmental testing, biomedicine, agriculture, etc.

[0029] Compared with the prior art, the fluorescence spectrum test of the fluorescent probe Rh prepared in the present invention with 17 common metal ions shows that the fluorescence spectrum of Fe 3+ and Al 3+ There is a significant fluorescence enhancement effect; UV-visible absorption curve test shows that a new peak appears at 560nm and the absorbance increases significantly, while at 350nm, Fe 3+ There is an obvious absorption peak and Al 3+ No, Fe 3+ and Al 3+ Distinguish; color reaction test, when Fe 3+ and Al 3+ When the ion concentration reaches 0.05 mg / L, a significant color change effect occurs. Since the test is carried out in a methanol and HEPES buffer solution with a volume ratio of 1:4, which is equivalent to diluting the water sample 5 times, when the Fe 3+ When the water sample appears light pink, it indicates that the conventional iron index of groundwater meets the III requirement; when the Al 3+When the water sample appears light pink, it indicates that the conventional aluminum index of groundwater no longer meets the III requirement.

[0030] Note: "Groundwater Quality Standard (GB / T 14848-2017)" Groundwater Routine Testing Standard: Fe 3+ Class II≤0.2mg / L, Class III≤0.3mg / L; Al 3+ Class III ≤ 0.2 mg / L; Class II: The groundwater has a low content of chemical components and is suitable for various purposes; Class III: The groundwater has a medium content of chemical components, based on GB5749-2006, and is mainly suitable for centralized drinking water sources and industrial and agricultural water). BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the H NMR spectrum of intermediate L2.

[0032] Figure 2 It is a comparison chart of the nuclear magnetic resonance hydrogen spectra of intermediate L2, rhodamine B hydrazide and probe Rh.

[0033] Figure 3 This is the mass spectrometry characterization of probe Rh.

[0034] Figure 4 The fluorescence responses of probe Rh to 17 ions.

[0035] Figure 5 This is a comparison chart of the fluorescence intensity changes of probe Rh and 17 metal ions at 585nm.

[0036] Figure 6 This is the UV-visible absorption spectrum of probe Rh and 17 metal ions.

[0037] Figure 7 Comparison of the absorption intensity changes of probe Rh and 17 metal ions at 560nm.

[0038] Figure 8 This is a color comparison chart of probe Rh and 17 metal ions.

[0039] Fig. 9 As the probe Rh in different Al 3+ Color comparison chart of concentration.

[0040] Fig.10 As the probe Rh in different Fe 3+ Color comparison chart of concentration. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.

[0042] Example 1. Preparation of fluorescent probe Rh

[0043] 1) Synthesis of intermediate L1:

[0044] Weigh p-aminobenzenesulfonic acid (5.1957g, 0.03mol) and place it in a beaker. Add 70mL of deionized water to dissolve it. At the same time, add 10% anhydrous Na2CO3 solution to make the pH value of the p-aminobenzenesulfonic acid aqueous solution between 6-7 to increase the solubility of p-aminobenzenesulfonic acid in water. Place the beaker in an ice bath at 0°C and stir continuously. Weigh cyanuric chloride (5.5320g, 0.03mol) and dissolve it in 60mL of acetone solution. Place the cyanuric chloride solution in a constant pressure funnel and add it at a rate of 2 to 3 drops per second. After the addition is completed, continue to stir and react for 8 hours. During the reaction, continuously add 10% anhydrous Na2CO3 solution to adjust the pH value of the reaction so that the solution is neutral. During the stirring process, it can be clearly seen that a white precipitate slowly begins to precipitate in the clear liquid. After the reaction is completed, the beaker is left to stand for a period of time to allow the precipitate and the solution to separate. A white solid is obtained by vacuum filtration, which is washed with acetone to remove cyanuric chloride that may not have reacted completely, then washed with a large amount of deionized water, and dried to finally obtain a white powder intermediate L1 with a mass of 6.9453 g and a yield of 72.1%.

[0045] 2) Synthesis of intermediate L2:

[0046] In a 250mL round-bottom flask, add p-hydroxybenzaldehyde (2.6226g, 0.02mol), 50mL THF, and triethylamine (7mL, 0.1mol), and place in an ultrasonic cleaner to shake and dissolve; in a 100mL beaker, add intermediate L1 (3.211g, 0.01mol) and 40mL THF, after ultrasonic dissolution, transfer to a constant pressure funnel, and drip into the above p-hydroxybenzaldehyde solution at a rate of 2-3 drops / second. When the dripping is completed, adjust the reaction temperature to 80°C, ultrasonic reaction for 30min, stop for 10min, continue interval ultrasonication, and ultrasonic reaction for a total of 120min. After the reaction is completed, the reaction solution is concentrated into an oily substance, the flask is allowed to stand and cool to room temperature, ethanol 20mL is added, and hydrochloric acid is added under stirring to adjust pH=6-7, and filtered, washed with ethanol, and dried to finally obtain a white powder intermediate L2 with a mass of 3.1667g and a yield of 64.32%.

[0047] The H NMR spectrum analysis of intermediate L2 is as follows Figure 1As shown in Table 1, by analysis, there are 7 H atoms in the intermediate L2, and the displacements at 2.51 and 3.35 correspond to the deuterated DMSO peak and water peak. Since H5 and H6 have displacements at 7.37, the displacement at 7.55 is H3, the displacement at 8.05 is H2, the displacement at 10.05 is H1, and the displacement at 10.45 is H7, it is confirmed that the target product is synthesized.

[0048] Table 1

[0049]

[0050]

[0051] 3) Synthesis of fluorescent probe Rh:

[0052] Weigh rhodamine B hydrazide (1.005 g, 0.0022 mol) and intermediate L2 (0.4920 g, 0.001 mol) into a 100 mL round-bottom flask, then add 50 mL of anhydrous methanol, stir, and reflux at 70-75 ° C for 15-16 hours. The solution changes from a suspension to a light red clear liquid. The solvent is removed by rotary evaporation to obtain a crude product, and ethyl acetate is added for ultrasonic washing to remove excess unreacted rhodamine B hydrazide. Finally, the powdery white solid probe Rh is obtained by vacuum filtration with a mass of 0.7162 g and a yield of 52.3%.

[0053] By analyzing the H NMR spectra of intermediate L2, rhodamine B hydrazide and probe Rh, Figure 2 As shown, the peak of NH2 in Rhodamine B hydrazide disappears, the peak of the aldehyde group in the intermediate L2 also disappears, and the peak of the newly generated CH=N appears, indicating that the target product Rh has been synthesized.

[0054] High-resolution mass spectrometry of probe Rh Figure 3 As shown, the ion peak m / z = 1367.5 is assigned to the target product quasi-molecular ion peak [MH + ], indicating that the probe Rh has been successfully synthesized.

[0055] Example 2: Application of fluorescent probe Rh

[0056] 1. Changes in fluorescence response of Rh in the presence of 20 times the amount of metal ions

[0057] Fe 3+ 、Al 3+ , Cu 2+ , Ca 2+ , Mn 2+ Mg 2+ 、Ag + Cr 3+ 、Cd 2+ 、Ni2+ 、Zn 2+ 、Co 2+ , Pb 2+ 、Na + , K + , Ba 2+ , Hg 2+ 17 common metal ions were prepared into aqueous solutions with a concentration of 0.1 mol / L.

[0058] Probe Rh (5×10 -6 mol / L) preparation: Take 1mL 5×10 -4 mol / L probe Rh solution (DMF) was placed in a 100 mL volumetric flask, diluted with methanol and 10 mmol / L HEPES buffer solution (volume ratio 1:4), fixed to volume, shaken, and allowed to stand.

[0059] The parameters of the fluorescence spectrum test were set as follows: the scanning excitation wavelength was set to 350 nm, the scanning range was 440-680 nm, the excitation bandwidth was 10 nm, the emission bandwidth was 10 nm, and the gain was medium.

[0060] 17 common metal ion response tests: First, take 3mL Rh (5×10 -6 mol / L) solution in a 1 cm quartz cuvette with four sides transparent to light, and scan the fluorescence spectrum of the probe Rh. Take 3 mL of Rh (5×10 -6 0.1 mol / L) solution was placed in a 1 cm quartz cuvette with light-transmitting surfaces on all four sides, 3 μL of 0.1 mol / L metal ion solution (the metal ion concentration is 20 times that of Rh) was added, shaken well, placed in the sample chamber, and the fluorescence spectrum was scanned. By comparing the change in fluorescence intensity of the probe Rh at 585 nm, the response and recognition effect of Rh on metal ions was determined (this operation was repeated until 17 metal ions were tested).

[0061] The test results of the fluorescence spectrum curve are as follows: Figure 4 As shown, when there is Fe in the Rh solution 3+ and Al 3+ When the fluorescence value at 585 nm increased significantly, the probe Rh had almost no response to the other 15 metal ions. 3+ 、Al 3+ It has a good selective recognition effect.

[0062] Figure 5 The probe Rh(5×10 -6 mol / L) in the presence of 20 times the amount of 17 metal ions, a bar graph was made by comparing the fluorescence intensity change of probe Rh at 585nm before and after the addition of metal ions. It can be seen from the figure that Fe 3+ 、Al3+ The fluorescence response of Fe 3+ The fluorescence change value of Al 3+ The fluorescence change value increased by more than 8 times. When the other 15 ions were present, the probe Rh had almost no fluorescence response. By comparison, it can be seen that the probe Rh has no fluorescence response to Fe 3+ 、Al 3+ There is good recognition of both ions and the effect is significant.

[0063] 2. Changes in UV-visible absorption response of probe Rh in the presence of 20 times the amount of metal ions

[0064] 17 common metal ion response tests: Take 3mL of probe Rh (5×10 -6 mol / L) in a 1 cm quartz cuvette, scan the UV-visible absorption spectrum curve, and after the scan, use the probe Rh as a blank solution to calibrate the instrument. Take 3 mL of probe Rh (5×10 -6 mol / L) in a 1 cm quartz cuvette, add 3 μL of 0.1 mol / L solution of 17 common metal ions; shake well, scan the UV-visible absorption curve, and determine whether the probe Rh has a recognition response to the metal ions by observing whether there are new absorption peaks and changes in the absorption peak at 585 nm (repeat this operation until the 17 metal ions are tested).

[0065] Figure 6 is to add 20 times Fe to the probe Rh 3+ , 20 times Al 3+ UV-visible absorption curves of 17 metal ion solutions. Figure 6 It can be seen that in Fe 3+ 、Al 3+ When it exists, a new absorption peak appears at 560nm, and it is inferred that this new peak is the probe Rh and Fe 3+ and Al 3+ The absorption peak of the interaction occurs. Other metal ions have almost no response or very weak response. Comparison of the absorption intensity changes of probe Rh and 17 metal ions at 560nm Figure 7 As shown in the figure, it shows that the probe Rh has a strong affinity for Fe in the visible light region. 3+ 、Al 3+ The recognition response effect is remarkable. In addition, at 350nm in the ultraviolet region, Fe 3+ There is an obvious absorption peak and Al 3+ No, through this phenomenon, Fe 3+ and Al 3+ distinguish.

[0066] 3. Color changes of probe Rh and 17 common metal ions

[0067] Take 17 10mL volumetric flasks, add 10μL of 0.1mol / L metal ion solution to each flask, and then add 60μL of 5×10 -4 mol / L probe Rh solution, methanol: 10mmol / L HEPES buffer solution = 4:1 (volume ratio), shake well, transfer to a 50mL colorimetric tube, and observe its color. The color comparison chart of probe Rh and 17 metal ions is as follows Figure 8 As shown, by color contrast, Fe 3+ 、Al 3+ It is obviously pink, Cu 2+ There is a slight color change but it is not noticeable.

[0068] (1) Rh and Al 3+ Color development study

[0069] Dilute the 1g / L national standard Al solution (1mol / L HNO3) with 10mM HEPES buffer solution to 0.25mg / L, 0.5mg / L, 1.0mg / L, 1.5mg / L, 2.5mg / L, 5.0mg / L, and 10.0mg / L solutions. Take 8 10mL volumetric flasks, use one volumetric flask as a blank, and add 2mL of the above solution to the rest, and then add 60μL 5×10 -4 mol / L probe Rh solution, methanol to volume, the corresponding aluminum ion concentrations are 0mg / L, 0.05mg / L, 0.1mg / L, 0.2mg / L, 0.3mg / L, 0.5mg / L, 1.0mg / L, 2.0mg / L. The solution was transferred to a colorimetric tube, and the probe Rh was diluted to different Al 3+ The color comparison chart of concentration is as follows Fig. 9 As shown, from Fig. 9 It can be seen that at 0.05 mg / L, it turns light pink, and the color deepens as the concentration increases. By visual observation, it can be determined whether it meets the Class III detection standard for conventional aluminum indicators in groundwater (≤0.2 mg / L).

[0070] (2) Probe Rh and Fe 3+ Color development study

[0071] Dilute the 1g / L national standard Fe solution (1mol / L HNO3) with 10mM HEPES buffer solution to 0.25mg / L, 0.5mg / L, 1.0mg / L, 1.5mg / L, 2.5mg / L, 5.0mg / L, and 10.0mg / L solutions. Take 8 10mL volumetric flasks, use one volumetric flask as a blank, and add 2mL of the above solution to the rest, and then add 60μL 5×10 -4mol / L probe Rh solution was fixed to volume with methanol. The corresponding iron ion concentrations were 0mg / L, 0.05mg / L, 0.1mg / L, 0.2mg / L, 0.3mg / L, 0.5mg / L, 1.0mg / L, and 2.0mg / L. The solution was transferred to a colorimetric tube. The probe Rh was added to different Fe 3+ The color comparison chart of concentration is as follows Fig.10 As shown, from Fig.10 It can be seen that at 0.05 mg / L, it turns light pink, and the color deepens as the concentration increases. By visual observation, it can be determined whether it meets the Class III test standard for conventional iron indicators in groundwater (≤0.3 mg / L).

[0072] In summary, the probe Rh prepared in the present invention has a good 3+ , Fe 3+ The identification of Fe in groundwater is highly sensitive and can be determined by naked eye observation. 3+ 、Al 3+ Whether it meets the Class III testing standards.

[0073] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A Highly Sensitive Visualization of Fe 3+ / Al 3+ The fluorescent probe Rh is characterized by: The structural formula of the fluorescent probe Rh is as follows:

2. A highly sensitive visual Fe as claimed in claim 1 3+ / Al 3+ The method for preparing the fluorescent probe Rh is characterized in that: The following steps are involved: S1, using cyanuric chloride and p-aminobenzenesulfonic acid as raw materials to carry out alkylation reaction to synthesize intermediate L1; S2, using intermediate L1 and p-hydroxybenzaldehyde as raw materials, synthesizing intermediate L2 by alkylation reaction; S3. The intermediate L2 and rhodamine B hydrazide are subjected to a Schiff base reaction to obtain a rhodamine B hydrazide derivative fluorescent probe Rh.

3. The highly sensitive visual Fe according to claim 2 3+ / Al 3+ The method for preparing the fluorescent probe Rh is characterized in that: The step S1 specifically includes: S11, weigh 0.03 mol of p-aminobenzenesulfonic acid and put it in a beaker, add 70 mL of deionized water to dissolve it, and at the same time drop 10% anhydrous Na2CO3 solution to make the pH value of the p-aminobenzenesulfonic acid aqueous solution between 6-7 to increase the solubility of p-aminobenzenesulfonic acid in water; S12, place the beaker in an ice bath at 0°C and stir continuously; weigh 0.03 mol of cyanuric chloride and dissolve it in 60 mL of acetone solution, place the cyanuric chloride solution in a constant pressure funnel, and drip it into the aqueous solution of p-aminobenzenesulfonic acid at a rate of 2 to 3 drops per second until the dripping is completed, and continue to stir and react for 8 hours; during the reaction, continuously drip 10% anhydrous Na2CO3 solution to adjust the pH value of the reaction so that the solution is neutral; S13. After the reaction is completed, the beaker is left to stand for a period of time to allow the precipitate and the solution to separate, and a white solid is obtained by vacuum filtration. The unreacted cyanuric chloride is removed by washing with acetone, and then washed with a large amount of deionized water, and finally a white powder, namely the intermediate L1, is obtained by drying.

4. The highly sensitive visual Fe according to claim 2 3+ / Al 3+ The method for preparing the fluorescent probe Rh is characterized in that: The step S2 specifically includes: S21, weigh p-hydroxybenzaldehyde and dissolve it in THF solution, and add triethylamine; S22, weigh the intermediate L1 and dissolve it in THF solution, and add it dropwise to the p-hydroxybenzaldehyde solution at a rate of 2 to 3 drops / second under a constant pressure funnel device; after the addition is completed, transfer the reaction container to an ultrasonic cleaner, adjust the temperature to 80°C, and ultrasonically react for 30 minutes, then stop for 10 minutes, and continue the interval ultrasonication for a total of 120 minutes; S23. After the reaction is completed, the reaction container is allowed to stand and cool to room temperature, and the pH is adjusted to 6-7. The mixture is filtered, washed with ethanol, and dried to finally obtain a white powder, namely the intermediate L2.

5. The highly sensitive visual Fe according to claim 2 3+ / Al 3+ The method for preparing the fluorescent probe Rh is characterized in that: The step S3 specifically includes: S31, add rhodamine B hydrazide and intermediate L2 to the reaction container respectively, add anhydrous methanol as solvent, stir and reflux at 70-75°C for 12-16h, and the solution changes from a suspension to a light red clear liquid; S32. The solvent is removed by rotary evaporation to obtain a crude product, ethyl acetate is added for stirring or ultrasonic oscillation is used for washing to remove excess unreacted Rhodamine B hydrazide, and finally, a white solid, i.e., the fluorescent probe Rh, is obtained by filtration under reduced pressure.

6. The highly sensitive visual Fe according to claim 2 3+ / Al 3+ The method for preparing the fluorescent probe Rh is characterized in that: In the step S2, the molar ratio of the intermediate L1, p-hydroxybenzaldehyde and triethylamine is 1:2:

10.

7. The highly sensitive visual Fe according to claim 2 3+ / Al 3+ The method for preparing the fluorescent probe Rh is characterized in that: In the step S23, after the reaction is completed, the reaction solution is concentrated into an oily substance, ethanol is added, and under stirring, hydrochloric acid is added to adjust the pH value.

8. The highly sensitive visual Fe according to claim 2 3+ / Al 3+ The method for preparing the fluorescent probe Rh is characterized in that: In the step S3, the molar ratio of the intermediate L2 to the rhodamine B hydrazide is 1:2.

1.

9. The novel high-sensitivity visual Fe according to claim 1 3+ / Al 3+ The application of fluorescent probe Rh in environmental testing, biomedicine, agriculture, etc.

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