Preparation method and application of a cyclodextrin-histidine / lanthanum-based complex

Abstract

The present invention relates to a preparation method and application of a cyclodextrin - histidine / lanthanum complex, belonging to the technical field of fluorescence sensors. The preparation method includes: mixing a cyclodextrin - histidine fluorescent molecule with a lanthanum source in a solution and heating for reaction to obtain a cyclodextrin - histidine / lanthanum fluorescent complex; wherein, the preparation method of the cyclodextrin - histidine fluorescent molecule includes: mixing an aldehyde - group cyclodextrin and histidine in an aqueous solution for reaction to obtain; the aldehyde - group cyclodextrin is an aldehyde - group cyclodextrin obtained by pre - oxidizing β - cyclodextrin with sodium periodate. Compared with the prior art, the cyclodextrin - histidine / lanthanum complex prepared by the present invention can directly and highly specifically recognize phosphate ions, realizing highly sensitive detection of phosphate ions, being more suitable for accurate detection of trace pollutants at low concentrations and highly selective detection. In addition, portable detection of phosphate ions can be realized through a visualization technique based on fluorescence images.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent sensors, and relates to a preparation method and application of a complex based on cyclodextrin-histidine / lanthanum, in particular to a preparation method of a complex based on cyclodextrin-histidine / lanthanum and its application in the fluorescence detection of phosphate ions. Background Art

[0002] The content of dissolved reactive phosphorus is an important indicator in water quality monitoring. Phosphorus is a major nutrient required for plant growth and animal production. This inorganic nutrient mainly exists in the form of orthophosphate in water bodies. An appropriate concentration of phosphorus-containing nutrients in water bodies is of great significance for maintaining the balance of aquatic ecosystems. However, when human activities such as agricultural and industrial emissions discharge excessive amounts of phosphorus-containing substances into water bodies, other plankton such as algae will reproduce rapidly, the dissolved oxygen content in the water will decrease, resulting in the massive death of other aquatic organisms such as fish, causing eutrophication of the aquatic ecosystem. Currently, most of the monitoring methods for the content of dissolved reactive phosphorus in water bodies still use traditional laboratory chemical analysis methods. Traditional laboratory monitoring methods rely on large-scale instruments, are limited in sampling frequency, and cannot analyze the pollutant content in real time; the accuracy of monitoring results requires a high level of proficiency of operators, and there are large human errors in the detection process; sample contamination or analyte degradation that may occur during the transportation and storage of samples to be detected will cause inaccurate detection results. Therefore, there is a need to propose a portable on-site monitoring method with high spatio-temporal resolution to achieve in-situ analysis of the content of dissolved reactive phosphorus in water bodies.

[0003] As one of the most promising optical analysis methods, fluorescence analysis has the advantages of rapidity, sensitivity, and low cost. These advantages are conducive to combining it with portable detection equipment. Selecting a suitable fluorescent sensor can achieve rapid, in-situ, and highly sensitive analysis of the target analyte. In the existing literature, the phosphate fluorescence detection method mainly constructs fluorescent sensors based on metal-organic frameworks and coordination polymers. Traditional fluorescent molecules are based on the chemical bond conjugation structure of π-conjugated aromatic structures, with adjustable emission colors and high fluorescence efficiency. However, the poor solubility, high biological toxicity, high cost, and complex synthesis process of these materials limit their practical applications. In addition, most of the reported fluorescent detection probes for phosphate ions rely on fluorescence spectrometers to analyze fluorescence signals, which are limited in in-situ on-site monitoring. In contrast, unconventional luminophores without significant conjugated structures have unique advantages such as high biocompatibility, low toxicity, good processability, and easy synthesis. However, currently reported fluorescent probes based on unconventional luminophore materials have limited applications and poor sensing performance. Therefore, designing a highly sensitive and selective fluorescent probe for phosphate ions based on unconventional luminophore materials is of great significance for the on-site detection of phosphate ions.

[0004] Chinese Patent CN202211187054.4 discloses a preparation method of a fluorescent sensor for detecting phosphate. In this method, 7-(diethylamino)coumarin-3-carbaldehyde carbohydrazide methyl ester Schiff base is first dissolved in a methanol solution. After adding a copper ion solution, it is left standing for a period of time so that 7-(diethylamino)coumarin-3-carbaldehyde carbohydrazide methyl ester Schiff base and Cu 2+ are completely complexed to prepare a fluorescent sensor solution. Although this patent also uses the fluorescence recovery signal for the detection of phosphate, it still needs to use a fluorescence spectrophotometer to analyze the fluorescence response signal. Therefore, it also has the problem of being limited in in-situ on-site monitoring.

[0005] Chinese Patent CN202110853706.2 discloses a cyclodextrin-europium molybdate / lanthanum hybrid microsphere, its preparation method and application in the fluorescence detection of phosphorus-containing compounds. The preparation method includes first preparing a mixed solution containing a molybdenum source and aldehyde group cyclodextrin; then adding a crosslinking agent and a co-solvent to the mixed solution and stirring and reacting to obtain a molybdenum-modified aldehyde group cyclodextrin suspension; then adding a lanthanum source and an europium source to the molybdenum-modified aldehyde group cyclodextrin suspension and continuing to stir and react. After purification treatment, a cyclodextrin-europium molybdate / lanthanum hybrid microsphere is obtained; the prepared hybrid microsphere can be used as a fluorescent detector for the qualitative or quantitative detection of phosphate ions, nitrophenyl phosphate or bis-nitrophenyl phosphate. This patent has problems such as more synthesis steps, the need to use detection equipment such as a fluorescence spectrometer in the detection process, and the inability to be combined with a portable visualization device supported by a mobile phone. In contrast, the synthesis process of the present invention is simple, large-scale material synthesis can be achieved, and it can be combined with a portable visualization device supported by a mobile phone to realize rapid and effective visual detection of phosphate in water by using the change of the image signal of the fluorescence color. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of a complex based on cyclodextrin-histidine / lanthanum and its application in the fluorescence detection of phosphate ions.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A preparation method of a fluorescent complex based on cyclodextrin-histidine / lanthanum, including: mixing a cyclodextrin-histidine fluorescent molecule and a lanthanum source in a solution and heating and reacting to obtain a fluorescent complex based on cyclodextrin-histidine / lanthanum;

[0009] Among them, the preparation method of the cyclodextrin-histidine fluorescent molecule includes: mixing aldehyde group cyclodextrin and histidine in an aqueous solution and reacting to obtain;

[0010] The aldehyde group cyclodextrin is the aldehyde group cyclodextrin obtained by pre-oxidizing β-cyclodextrin with sodium periodate.

[0011] Furthermore, the molar ratio of the aldehyde group cyclodextrin to histidine is 1:(6-9).

[0012] Furthermore, in the mixed reaction, the reaction temperature is 60-80 °C, and the reaction time is 0.5-1 h.

[0013] Furthermore, the molar ratio of the cyclodextrin-histidine fluorescent molecule to lanthanum element is 1:(1-4).

[0014] Furthermore, the lanthanum source includes lanthanum nitrate.

[0015] Furthermore, in the heating reaction, the reaction temperature is 60-80 °C, and the reaction time is 0.5-1 h.

[0016] Furthermore, the preparation method of the aldehyde group cyclodextrin includes: stirring and reacting β-cyclodextrin with sodium periodate in an aqueous solution in the dark, after nanofiltration, stirring and mixing with ethanol until precipitation occurs, and then successively filtering, washing, and freeze-drying to obtain the aldehyde group cyclodextrin;

[0017] The molar ratio of the β-cyclodextrin to sodium periodate is 1:(2-7); in the dark stirring reaction, the reaction temperature is 30-50 °C, and the reaction time is 3-5 h; during the purification process, a water / ethanol mixed solution with a volume ratio of 1 / 4 is used for washing.

[0018] A cyclodextrin-histidine / lanthanum complex is synthesized by the method described above.

[0019] An application of the cyclodextrin-histidine / lanthanum complex includes using the complex as a fluorescent probe for qualitative and / or quantitative detection of phosphate ions in water.

[0020] Furthermore, the quantitative detection method includes the following steps:

[0021] 1) Plot a standard curve: Mix the fluorescent probe with solutions containing different concentrations of phosphate ions respectively to obtain standard solutions with a phosphate ion concentration range of 0-10 ppm. Use a 365 nm ultraviolet lamp as the excitation light source, take the fluorescent images of the standard solutions in a dark environment, and analyze the YUV-U value of the images. Plot a standard curve with the U value as the ordinate and the phosphate ion concentration as the abscissa to obtain the phosphate detection fitting equation;

[0022] 2) Detection of phosphate ions in the water sample: Adopt the method in step 1), mix the fluorescent probe with the water sample to be tested at the same mixing ratio as that for preparing the standard solution to obtain a mixed sample, then use a 365 nm ultraviolet lamp as the excitation light source to obtain the fluorescent image of the mixed sample, and analyze the YUV-U value of the image. Then, according to the standard curve or the fitting equation, obtain the corresponding phosphate ion concentration.

[0023] First, the present invention oxidatively modifies β-cyclodextrin with low solubility and low reactivity using sodium periodate to obtain aldehyde group cyclodextrin with good water solubility, high reactivity, and containing a dialdehyde structure. Then, through the Schiff base reaction between the aldehyde group of aldehyde group cyclodextrin and the amino group in the histidine molecule, a fluorescent molecule based on histidine-grafted cyclodextrin is obtained. Subsequently, a novel fluorescent probe based on cyclodextrin-histidine / lanthanum complex is obtained through the coordination between histidine and lanthanum ions. The synthesized fluorescent probe has excellent fluorescence properties in solution, good water solubility, and environmental compatibility. The synthesized cyclodextrin-histidine / lanthanum complex as a fluorescent probe for phosphate ions can achieve highly selective and sensitive portable detection of phosphate based on visualization technology.

[0024] Compared with the prior art, the present invention has the following characteristics:

[0025] 1) Compared with Chinese Patent CN202110853706.2, the complex based on histidine-grafted cyclodextrin coordinated with lanthanum in the present invention has a clear molecular composition and spatial structure, and the probe has high biocompatibility and low toxicity. In addition, the complex based on histidine-grafted cyclodextrin coordinated with lanthanum as a specific recognition probe for phosphate ions can achieve highly sensitive and selective detection of phosphate ions in a portable detection device, showing good application prospects;

[0026] 2) The synthesis method of the present invention is simple, obtained by simply modifying cyclodextrin, and the synthesis conditions are relatively mild. The reaction temperature can be controlled at 80 °C, and a conventional water bath condition can provide the required preparation environment;

[0027] 3) Compared with traditional fluorescent molecules with conjugated structures, the cyclodextrin-histidine / lanthanum complex prepared in the present invention has the advantages of simple structure, low cost, good water solubility, and good environmental compatibility.

[0028] 4) The cyclodextrin-histidine / lanthanum complex prepared in the present invention can directly and highly specifically recognize phosphate ions, achieving highly sensitive detection of phosphate ions (the detection range is 0 - 10 ppm, and the detection limit is 0.06 ppm). It is more suitable for the accurate detection of trace pollutants at low concentrations and highly selective detection. In addition, portable detection of phosphate ions can be achieved through the visualization technology based on fluorescence images. Description of the Drawings

[0029] Figure 1 It is the fluorescence emission spectrum and optical diagram of the cyclodextrin-histidine / lanthanum complex synthesized in Example 1;

[0030] Figure 2Emission spectra of the fluorescence response of cyclodextrin-histidine / lanthanum complexes to phosphate ions under the conditions of different sodium periodate addition ratios in Example 2;

[0031] Figure 3 Emission spectra of the fluorescence response of cyclodextrin-histidine / lanthanum complexes to phosphate ions under the conditions of different histidine addition ratios in Example 3;

[0032] Figure 4 Emission spectra of the fluorescence response of cyclodextrin-histidine / lanthanum complexes to phosphate ions under the conditions of different lanthanum element addition ratios in Example 4;

[0033] Figure 5 Emission spectra of the fluorescence response of cyclodextrin-histidine / lanthanum complexes to phosphate ions under the conditions of different probe concentrations in Example 5;

[0034] Figure 6 Fluorescence emission spectra after adding different concentrations of phosphate ions in Example 6;

[0035] Figure 7 Detection standard curve of phosphate ions drawn in Example 6;

[0036] Figure 8 Effect of different interfering ions on the fluorescence emission spectra of the synthesized cyclodextrin-histidine / lanthanum complexes in Example 7. Detailed implementation mode

[0037] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] A fluorescence complex based on cyclodextrin-histidine / lanthanum, and its preparation method includes the following steps:

[0039] S1: Preparation of aldehyde group cyclodextrin:

[0040] Mix β-cyclodextrin and sodium periodate in water at a molar ratio of 1:(2 - 7) (preferably 1:6), and stir and react in the dark at 30 - 50 °C (preferably 40 °C) for 3 - 5 h. After nanofiltration, stir and mix with ethanol until precipitation occurs, and then filter, purify, and lyophilize in sequence to obtain aldehyde group cyclodextrin;

[0041] Among them, during the purification process, a water / ethanol mixed solution with a volume ratio of 1 / 4 is used for washing;

[0042] S2: Preparation of cyclodextrin-histidine fluorescent molecule:

[0043] Mix aldehyde group cyclodextrin and histidine in an aqueous solution at a molar ratio of 1:(6 - 9) (preferably 1:8) and react at 60 - 80 °C for 0.5 - 1 h to obtain a cyclodextrin-histidine fluorescent molecule;

[0044] S3: Preparation of cyclodextrin-histidine / lanthanum-based fluorescent complex:

[0045] Mix the cyclodextrin-histidine fluorescent molecule with a lanthanum source in solution and heat the reaction mixture at 60 - 80 °C for 0.5 - 1 h to obtain the cyclodextrin-histidine / lanthanum-based fluorescent complex;

[0046] Among them, the molar ratio of the cyclodextrin-histidine fluorescent molecule to the lanthanum element is 1:(1 - 4) (preferably 1:2); the lanthanum source is a water-soluble lanthanum salt, preferably lanthanum nitrate.

[0047] An application of a cyclodextrin-histidine / lanthanum complex, including using the complex as a fluorescent probe for qualitative and / or quantitative detection of phosphate ions in water.

[0048] Furthermore, the quantitative detection method includes the following steps:

[0049] 1) Plot a standard curve: Mix the fluorescent probe with solutions containing different concentrations of phosphate ions respectively to obtain standard solutions with a phosphate ion concentration range of 0 - 10 ppm. Use a 365 nm ultraviolet lamp as the excitation light source, take the fluorescent images of the standard solutions in a dark environment, and analyze the YUV-U value of the images (for example: use the "Picture Color Picker" function in the mobile phone APP "Color Picker"). Plot a standard curve with the U value as the ordinate and the phosphate ion concentration as the abscissa to obtain the phosphate detection fitting equation;

[0050] 2) Detection of phosphate ions in the water sample: Adopt the method in step 1), mix the fluorescent probe with the water sample to be tested at the same mixing ratio as that for preparing the standard solution to obtain a mixed sample. Then use a 365 nm ultraviolet lamp as the excitation light source to obtain the fluorescent image of the mixed sample, analyze the YUV-U value of the image, and then obtain the corresponding phosphate ion concentration according to the standard curve or the fitting equation.

[0051] In some specific embodiments, pretreatment of the water sample to be tested is also included before detection: Filter the water sample to be tested and adjust the pH to neutral 7. Take 25 mL of the water sample and mix it thoroughly with 5 mL of H2O2 (30 wt%) solution, and then treat it in a high-temperature reaction kettle under high temperature and high pressure conditions of 150 °C for 1 h to obtain a pretreated water sample; then detect the phosphate ion concentration in the pretreated water sample.

[0052] The following examples are implemented on the premise of the above technical solutions of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0053] Example 1:

[0054] A cyclodextrin - histidine / lanthanum - based complex, and its synthesis method comprises the following steps:

[0055] S1: Add 15 g of β - cyclodextrin to 100 mL of deionized water, stir evenly, then add 18 g of sodium periodate, and stir and react under dark conditions at 40 °C for 4 h. After filtering through a 220 nm filter membrane, take the filtrate and mix it with an excessive amount of absolute ethanol (800 mL) until precipitation occurs. Then, filter, wash multiple times with ethanol / water (V / V = 80 / 20), and freeze - dry to obtain aldehyde - cyclodextrin with good water solubility, high reaction activity, and containing a dialdehyde structure;

[0056] S2: Dissolve 2 mmol (2.268 g) of aldehyde - cyclodextrin and 16 mmol (2.48 g) of histidine in 400 mL of water;

[0057] S3: Stir and react the above - mentioned solution at 80 °C for 1 h;

[0058] S4: Dissolve 4 mmol (1.732 g) of lanthanum nitrate in 4 mL of water, drop - add it into the above - mentioned solution, and continue to stir and react at 80 °C for 1 h;

[0059] S5: Centrifuge and freeze - dry the above - mentioned solution to obtain the cyclodextrin - histidine / lanthanum - based fluorescent material powder.

[0060] Example 2: Influence of different addition ratios of sodium periodate

[0061] A cyclodextrin - histidine / lanthanum - based complex, the difference in its synthesis method compared with Example 1 is that:

[0062] In step S1, the dosages of sodium periodate used are 6 g, 12 g, and 18 g respectively (the molar ratios of β - cyclodextrin to sodium periodate are 1:2, 1:4, and 1:6); the rest is the same as in Example 1.

[0063] Using a 365 nm ultraviolet lamp as the excitation light source, measure the fluorescence emission curves before and after mixing the fluorescent probe with an equal - volume 2 ppm sodium dihydrogen phosphate solution. The results are as Figure 2 shown. As the addition ratio of sodium periodate increases, the fluorescence - enhanced response signal gradually becomes significant. When the addition molar ratio is 1:6, the fluorescence response is the largest.

[0064] Example 3: Influence of different addition ratios of histidine

[0065] A cyclodextrin - histidine / lanthanum - based complex, the difference in its synthesis method compared with Example 1 is that:

[0066] In step S2, the amounts of histidine used were 1.86 g and 2.48 g respectively (the molar ratios of aldehyde group cyclodextrin to histidine were 1:6 and 1:8 respectively); the rest was the same as in Example 1.

[0067] Using a 365 nm ultraviolet lamp as the excitation light source, the fluorescence emission curves before and after mixing the fluorescent probe with a 12 ppm sodium dihydrogen phosphate solution in equal volume were measured. The results are as Figure 3 shown. With the increase of the histidine addition ratio, the fluorescence response signal increased to a certain extent. When the added molar ratio was 1:8, the fluorescence response was the largest.

[0068] Example 4: Influence of different lanthanum element addition ratios

[0069] A cyclodextrin-histidine / lanthanum-based complex, the difference in its synthesis method compared with Example 1 lies in:

[0070] In step S3, the amounts of lanthanum nitrate used were 0.866 g and 1.732 g respectively (the molar ratios of aldehyde group cyclodextrin to lanthanum nitrate were 1:2 and 1:4 respectively); the rest was the same as in Example 1.

[0071] Using a 365 nm ultraviolet lamp as the excitation light source, the fluorescence emission curves before and after mixing the fluorescent probe with a 2 ppm sodium dihydrogen phosphate solution in equal volume were measured. The results are as Figure 4 shown. With the increase of the lanthanum nitrate addition ratio, the fluorescence response signal decreased significantly. When the added molar ratio was 1:2, the fluorescence response was the largest.

[0072] Example 5: Influence of different probe concentrations

[0073] In this example, the cyclodextrin-histidine / lanthanum-based complex prepared in Example 1 was used as the fluorescent probe and dispersed in deionized water with concentrations of 0.2, 0.4, 1.0, and 1.6 g / L respectively.

[0074] Using a 365 nm ultraviolet lamp as the excitation light source, the fluorescence emission curves before and after mixing the fluorescent probe with a 2 ppm sodium dihydrogen phosphate solution in equal volume were measured. The results are as Figure 5 shown. With the increase of the probe concentration, the fluorescence enhancement response signal decreased significantly. When the probe concentration in the mixed solution was 0.5 g / L, the fluorescence response was the largest.

[0075] Example 6:

[0076] In this example, the cyclodextrin-histidine / lanthanum-based complex prepared in Example 1 was used as the fluorescent probe to detect phosphate ions in water samples. The specific detection process is as follows:

[0077] 1) Preparation of the standard curve: The cyclodextrin - histidine / lanthanum complex was dispersed in deionized water at a concentration of 1 g / L and used as a fluorescent probe.

[0078] Standard sodium dihydrogen phosphate solutions with concentrations of 0, 0.05, 0.1, 0.3, 0.5, 0.8, 1.0, 3.0, 5.0, 8.0, and 10.0 ppm were prepared respectively. Then, 1 mL of each solution was taken and mixed with an equal volume of the fluorescent probe to obtain a mixed solution. Using a fluorescence spectrometer with a 365 nm ultraviolet lamp as the excitation light source in a dark environment, the fluorescence emission curve of the mixed solution was measured. The results are as Figure 6 shown. It can be seen from the figure that as the concentration of phosphate ions added increases, the fluorescence intensity of the system gradually increases.

[0079] Fluorescence images of the above - mentioned mixed solutions were taken. As the phosphate concentration increased, the image brightness gradually increased. Using the "Picture Color Picker" function in the mobile phone APP "Color Picker" to analyze the captured images, the YUV - U value of the image was directly obtained. With the U value as the ordinate and the phosphate concentration (ppm) as the abscissa, a standard curve was plotted (as Figure 7 shown). Detection fitting equations for phosphate were obtained in two concentration ranges: in the range of 0 - 1 ppm, y = 7.3797x + 1.2316, (R 2 = 0.95); in the range of 1 - 10 ppm, y = 1.8972x + 7.7544, (R 2 = 0.99). According to the detection limit LOD = 3σ / N (where σ is the standard deviation of the blank sample and N is the slope of the linear equation), the detection limit of the cyclodextrin - histidine / lanthanum complex as a probe was calculated to be 0.06 ppm.

[0080] 2) Pretreatment of the water sample to be measured: The water sample to be measured was filtered and the pH was adjusted to 7. Then, 25 mL was taken and mixed thoroughly with 5 mL of H2O2 (30 wt%) solution. The mixture was treated in a high - temperature reaction kettle under high - temperature and high - pressure conditions of 150 °C for 1 h to obtain a pretreated water sample.

[0081] 3) Detection of phosphate in the water sample: 0.5 mL of the pretreated water sample was taken and mixed with 0.5 mL of the fluorescent probe to obtain a mixed sample. After obtaining a fluorescence image with a 365 nm ultraviolet lamp as the excitation light source, the U value of the image was obtained through image - analysis software using the same method as in step 2). Then, according to the fitted equation, the corresponding phosphate concentration was obtained. Specifically, the standard addition recovery experiments were carried out on the lake water and tap water collected from Jiangpu Park in Shanghai using the above - mentioned method. Phosphate with concentrations of 0.5 ppm and 10 ppm were added respectively, and the above - mentioned method was used for testing. The phosphate recovery rates obtained were 99.14% - 109.40%, and the relative standard deviations were 7.18 - 11.84%. The specific results are shown in Table 1 in the appendix.

[0082] Table 1 Results of the spike recovery experiment

[0083]

[0084] Example 7:

[0085] Using the cyclodextrin - histidine / lanthanum synthesized in Example 1 as a fluorescent probe, the anti - interference detection of different co - existing anions, cations and other interfering substances was carried out. The specific method is as follows:

[0086] Disperse the cyclodextrin - histidine / lanthanum complex in deionized water with a concentration of 1 g / L as a fluorescent probe; at the same time, prepare multiple 20 ppm solutions of different ionic salts K + , Na + , Ca 2+ , Mg 2+ , NH4 + and Cl - , NO3 - , HCO3 - , SO4 2- . Take 1 mL of each and mix it with an equal volume of the fluorescent probe. After standing until the reaction system is stable, use the method in step 3) of Example 3 to take its fluorescence image with a 365 nm ultraviolet lamp as the excitation light source and analyze its U value to investigate its selective recognition ability. As Figure 8 shown, after adding phosphate ions, the fluorescence signal of the system is significantly enhanced, while the addition of other interfering substances has no obvious effect on the fluorescence response of the system, indicating that this method has good selectivity, and the cyclodextrin - histidine / lanthanum complex fluorescent probe realizes the specific recognition of phosphate ions.

[0087] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. Those skilled in the art can obviously make various modifications to these embodiments easily and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of a fluorescence complex based on cyclodextrin-histidine / lanthanum, characterized in that, The method includes: mixing a cyclodextrin-histidine fluorescent molecule with a lanthanum source in a solution and heating for reaction to obtain a cyclodextrin-histidine / lanthanum-based fluorescent complex; Among them, the preparation method of the cyclodextrin-histidine fluorescent molecule includes: mixing and reacting aldehyde group cyclodextrin and histidine in an aqueous solution to obtain; The aldehyde group cyclodextrin is the aldehyde group cyclodextrin obtained by pre-oxidizing β-cyclodextrin with sodium periodate.

2. The preparation method of the fluorescent complex based on cyclodextrin-histidine / lanthanum according to claim 1, characterized in that, The molar ratio of the aldehyde group cyclodextrin to histidine is 1:(6-9).

3. The preparation method of the cyclodextrin-histidine / lanthanum-based fluorescent complex according to claim 1, characterized in that In the mixing reaction, the reaction temperature is 60-80 °C and the reaction time is 0.5-1 h.

4. The preparation method of the cyclodextrin-histidine / lanthanum-based fluorescent complex according to claim 1, wherein The molar ratio of the cyclodextrin-histidine fluorescent molecule to the lanthanum element is 1:(1-4).

5. The preparation method of the cyclodextrin-histidine / lanthanum-based fluorescent complex according to claim 1, characterized in that, The lanthanum source includes lanthanum nitrate.

6. The preparation method of the cyclodextrin-histidine / lanthanum-based fluorescent complex according to claim 1, wherein, In the heating reaction, the reaction temperature is 60-80 °C and the reaction time is 0.5-1 h.

7. The preparation method of the cyclodextrin-histidine / lanthanum-based fluorescent complex according to claim 1, characterized in that, The preparation method of the aldehyde group cyclodextrin includes: stirring and reacting β-cyclodextrin with sodium periodate in an aqueous solution in the dark to obtain aldehyde group cyclodextrin; The molar ratio of β-cyclodextrin to sodium periodate is 1:(2-7); in the dark stirring reaction, the reaction temperature is 30-50 °C and the reaction time is 3-5 h.

8. A cyclodextrin-histidine / lanthanum complex, characterized in that, Synthesized by the method according to any one of claims 1 to 7.

9. An application of the cyclodextrin-histidine / lanthanum complex as described in claim 8, characterized in that, The said complex is used as a fluorescent probe for qualitative and / or quantitative detection of phosphate ions in water.

10. Use of the cyclodextrin-histidine / lanthanum-based fluorescent complex according to claim 9, characterized in that, The quantitative detection method includes the following steps: 1) Plotting a standard curve: Mixing the fluorescent probe with solutions containing different concentrations of phosphate ions respectively and uniformly to obtain standard solutions with a phosphate ion concentration range of 0-10 ppm. Using a 365 nm ultraviolet lamp as the excitation light source, taking the fluorescent images of the standard solutions in a dark environment, and analyzing the YUV-U value of the images. Plotting a standard curve with the U value as the ordinate and the phosphate ion concentration as the abscissa to obtain a phosphate detection fitting equation; 2) Detection of phosphate ions in the water sample: Using the same method as in step 1), mixing the fluorescent probe with the water sample to be tested at the same mixing ratio as that for preparing the standard solution to obtain a mixed sample. Then, using a 365 nm ultraviolet lamp as the excitation light source to obtain the fluorescent image of the mixed sample, and analyzing the YUV-U value of the image. Then, according to the standard curve or the fitting equation, obtaining the corresponding phosphate ion concentration.

Images