Naphthylurea modified magnetic nanoparticle for iron ion fluorescence detection and preparation method thereof

Abstract

The invention discloses a naphthylurea-modified magnetic nanoparticle for iron ion fluorescence detection and a preparation method thereof, a surface ion imprinting technology is utilized to successfully fix a naphthylurea fluorescent chromophore on the surface of the magnetic nanoparticle to form a specific imprinting site accurately matched with the shape and the size of a template iron ion; the preparation process of the material is simple, the prepared naphthylurea modified magnetic nanoparticles have the excellent nano-carrier characteristic of a magnetic nano-material and the fluorescence detection advantage of a naphthylurea fluorescent probe, and the selective binding capacity of a naphthylurea chromophore and target iron ions is remarkably improved by applying a surface ion imprinting technology; therefore, the probe material shows good selectivity in the aspect of fluorescence detection of iron ions in a water body.

Description

Technical Field

[0001] The invention relates to the field of organic functional modification of magnetic nanoparticle surfaces, and in particular to a naphthaleneurea-modified magnetic nanoparticle ion fluorescent probe based on surface imprinting technology and an application thereof, for realizing selective fluorescent detection of iron ions in water. Background Art

[0002] In recent years, fluorescent probe technology has shown great potential in the monitoring of specific analytes in environmental and biological systems due to its simplicity, portability, economy and excellent selectivity. Among many ions, iron ions have become one of the hot spots in fluorescent probe research because they are an indispensable element in biological systems and play a key role in the storage and transportation of oxygen to tissues. The balance of iron ions in organisms is crucial to maintaining normal physiological functions. However, the imbalance of iron ion levels, whether it is deficiency or excessive accumulation, is closely related to a series of diseases, such as anemia, liver and kidney dysfunction, Alzheimer's disease and Parkinson's disease.

[0003] At present, there are many promising small molecule iron ion fluorescent probes. These probes are usually highly selective and sensitive and perform well under laboratory conditions, but they still face some challenges in practical applications. Among them, one of the main problems is that most of the reported small molecule iron ion fluorescent probes are highly hydrophobic and often need to rely on organic solvents such as methanol, acetonitrile and tetrahydrofuran for solubilization. The use of these organic solvents not only increases the complexity of the operation, but also limits the direct application of the probe in a pure water environment.

[0004] Therefore, in order to overcome this limitation, the development of new fluorescent probes for iron ions and the realization of efficient and direct detection in pure water is still a research direction worthy of in-depth exploration. In recent years, the covalent fixation of fluorescent groups on inorganic nanomaterial carriers has been introduced into the field of fluorescent probes as organic-inorganic hybrid optical probes. The surface of magnetic nanoparticles can be dispersed in water for a long time by adsorbing stabilizers or charge regulation to prevent particle aggregation. Magnetic nanoparticles are easy to prepare and can be easily separated from aqueous media under the action of an external magnetic field, thereby facilitating the recycling and reuse of materials. The silica shell, because of its rich surface hydroxyl groups, can react with coupling agents and further form a stable covalent connection with the fluorescent group, effectively protecting the internal ferroferric oxide core from erosion by the acidic environment.

[0005] Traditional ion-imprinted polymer materials are first prepared by copolymerization of functional monomers and crosslinking agents that coordinate template ions, and then the coordinated template ions are removed to form specific imprinted cavities that are highly matched to the shape and size of the target ions. Surface imprinting technology based on sol-gel process has also been developed, which can form a thin layer of imprinted coating film containing imprinted cavities on the surface of inorganic materials. Most reported surface imprinting technologies usually introduce chelating groups on inorganic carriers with high specific surface areas to form specific imprinted cavities. This nanocomposite material is mainly used for selective adsorption of target metal ions. If fluorescent probe molecules are introduced on the carrier surface in combination with surface imprinting technology, not only can specific recognition of target ions in water be achieved, but also selective fluorescence detection and adsorption removal can be performed, showing a wide range of application potential in the field of environmental protection. Based on this, the present invention uses surface ion imprinting technology to prepare naphthalene urea-modified magnetic nanoparticles as fluorescent probe materials for iron ions. Through this technology, specific recognition and selective fluorescence detection of target iron ions in water can be achieved, thereby improving the selectivity and sensitivity of the material to iron ion detection. Summary of the invention

[0006] In view of the limited applicability of small molecule fluorescent probes for detecting target metal ions in the prior art, the present invention provides a naphthalene urea modified magnetic nanoparticle for fluorescent detection of iron ions and a preparation method thereof. A naphthalene urea fluorescent chromophore imprinted cavity structure having high complementarity with the iron ions in shape and size is fixed on the surface of the magnetic nanoparticle by a surface ion imprinting method, so as to achieve specific action and fluorescent detection of the target iron ions. The general structural formula is as follows:

[0007]

[0008] in, Refers to the partial structure of the silica magnetic nanoparticles, where the dark part is the magnetic ferroferric oxide core and the light gray part is the silica shell. It is a specific imprinted cavity structure with high complementarity with the iron ion in shape and size, n is selected from one of the integers 1, 2 or 3, R is selected from one of the hydrogen atom or methyl group, and the substitution position is one of the four substitution sites on the benzene ring.

[0009] The present invention further provides a method for preparing the above-mentioned naphthaleneurea modified magnetic nanoparticles for fluorescent detection of iron ions, comprising the following steps:

[0010] Step 1: add equal amounts of isocyanate functionalized siloxane coupling agent and naphthylamine compound to a round-bottom flask filled with an organic solvent, control the temperature within the range of 30 to 50° C., mechanically stir the reaction for 8 to 12 hours, and remove the organic solvent in the reaction system by vacuum rotary evaporation to obtain a light pink oily substance, i.e., a naphthurea functionalized siloxane coupling agent; then, directly dissolve the light yellow oily substance in anhydrous ethanol, and add a certain amount of ferric nitrate to the solution as a template imprinted metal ion, wherein the amount of ferric nitrate is half the amount of the naphthylamine compound, and control the temperature within the range of 40 to 50° C. and mechanically stir for 12 to 24 hours under nitrogen protection; then, remove the ethanol in the reaction system by vacuum rotary evaporation again, and finally obtain a complex of a naphthurea functionalized siloxane coupling agent monomer and an iron ion template, Nap(Fe), and the specific synthesis steps and reaction formulas are expressed as follows:

[0011]

[0012] Step 2: Add the Nap(Fe) in step 1 and the magnetic nanoparticles coated with silica prepared by the coprecipitation method into an organic solvent, and then achieve good dispersion under the action of ultrasound, and control the system temperature in the range of 70 to 90°C for mechanical stirring under the protection of a nitrogen atmosphere for 12 to 24 hours; after the reaction system is cooled to room temperature, the magnetic suspended solids in the water are separated by the action of an external magnetic field, and the obtained solid is first washed twice with tetrahydrofuran and then washed twice with ethanol to completely remove impurities; finally, the washed solid is vacuum dried to obtain a magnetic nanoparticle material with a surface modified with a naphthyurea chromophore and coordinated with iron ions, which is recorded as Fe3O4-Nap(Fe). The specific synthesis steps and reaction formulas are expressed as follows:

[0013]

[0014] Step 3: Add ATP-Nap(Fe) in step 2 to an inorganic acid solution, and then mechanically stir at room temperature for 12 to 24 hours after ultrasonic dispersion, and separate the product by centrifugation; the obtained solid is repeatedly washed with deionized water for several times until the aqueous solution after washing is close to neutral; finally, the naphthalene urea modified magnetic nanoparticle material based on surface ion imprinting technology is obtained by vacuum drying, which is recorded as Fe3O4-Nap-IIA. The specific synthesis steps and reaction formula are expressed as follows:

[0015]

[0016] As a preferred technical solution of the present invention, in step 1, the isocyanate functionalized siloxane coupling agent is selected from any one of isocyanate propyl triethoxysilane, isocyanate propyl trimethoxysilane, isocyanate ethyl triethoxysilane, isocyanate ethyl trimethoxysilane, isocyanate methyl triethoxysilane or isocyanate methyl trimethoxysilane; the naphthylamine compound is selected from 1-naphthylamine, 5-methyl-1-naphthylamine, 6-methyl-1-naphthylamine, 7-methyl-1- The invention relates to a method for preparing a naphthylamine compound, wherein the naphthylamine compound is selected from one of naphthylamine and 8-methyl-1-naphthylamine; the organic solvent is selected from any one of dichloromethane, chloroform, acetone, methanol, anhydrous ethanol, isopropanol, anisole, tetrahydrofuran, dioxane, acetonitrile, toluene or N,N-dimethylformamide; the solid-liquid mass volume ratio of the naphthylamine compound and the organic solvent is 1:100-150 g / mL; the solid-liquid mass volume ratio of the naphthylamine compound and anhydrous ethanol for dissolving the yellow oil is 1:100-150 g / mL.

[0017] As a preferred technical solution of the present invention, in step 2, the mass ratio of Nap(Fe) to the magnetic nanoparticles is 1:1.0-1.5; the organic solvent is selected from any one of dichloromethane, chloroform, acetone, methanol, anhydrous ethanol, isopropanol, anisole, tetrahydrofuran, dioxane, acetonitrile, toluene or N,N-dimethylformamide; the solid-liquid mass volume ratio of the magnetic nanoparticles to the organic solvent is 1:120-180 g / mL.

[0018] As a preferred technical solution of the present invention, the inorganic acid solution in step three is selected from any one of sulfuric acid, hydrochloric acid or nitric acid solution; the solid-liquid mass volume ratio of the Fe3O4-Nap(Fe) to the inorganic acid solution is 1:150-200 g / mL; and the mass concentration of the inorganic acid is 0.3-1.0%.

[0019] The invention discloses an application of naphthylurea modified magnetic nanoparticles for fluorescent detection of iron ions. The naphthylurea chromophore on the surface of the naphthylurea modified magnetic nanoparticles will undergo fluorescence quenching after binding with iron ions in water. Therefore, the naphthylurea modified magnetic nanoparticles based on surface imprinting technology can be used for selective fluorescent detection of iron ions in water.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a naphthalene urea modified magnetic nanoparticle for fluorescent detection of iron ions. The preparation method is simple, and the material can be easily separated from the aqueous medium under the action of an external magnetic field, which is convenient for the recovery and reuse of the material. On this basis, when the naphthalene urea fluorescent chromophore forms a complex with the iron ion as a surface modifier, the fluorescence intensity gradually decreases with the increase of the iron ion content. Therefore, the naphthalene urea modified magnetic nanoparticle provided by the present invention is suitable for the fluorescent quantitative detection of iron ions in aqueous solution.

[0022] The present invention provides a naphthaleneurea modified magnetic nanoparticle for fluorescent detection of iron ions. The surface ion imprinting technology forms a specific recognition site on the surface of the material. The site has a high complementarity with the iron ion in shape and size. Under the condition of the presence of other interfering ions, the specific effect with the target iron ion can be significantly improved, and the selectivity of fluorescent quantitative detection of iron ions in water bodies can be improved, which solves the problem of limited selectivity of nano-composite fluorescent probes for target ion detection in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0024] Figure 1 This is a transmission electron microscope photo of Fe3O4-Nap-IIA-1 prepared in Example 1;

[0025] Figure 2 The fluorescence emission spectra of Fe3O4-Nap-IIA-1 prepared in Example 1 at an excitation wavelength of 298 nm in the presence of different concentrations of iron ions;

[0026] Figure 3 The fluorescence intensity (395 nm) change of Fe3O4-Nap-IIA-1 prepared in Example 1 after adding iron ions in the presence of interfering ions;

[0027] Figure 4 The fluorescence intensity (395 nm) change of Fe3O4-Nap-IIA-1 prepared in Example 4 after adding iron ions in the presence of interfering ions; DETAILED DESCRIPTION

[0028] To further disclose the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0029] Embodiment 1:

[0030] A preparation method of naphthaleneurea modified magnetic nanoparticles Fe3O4-Nap-IIA-1 for fluorescent detection of iron ions, the specific steps are as follows:

[0031] (i) 1.235 g (5.0 mmol) of isocyanate propyl triethoxysilane and 0.715 g (5.0 mmol) of 1-naphthylamine were added to a round-bottom flask containing 100 mL of tetrahydrofuran, and the temperature was controlled at 40°C and mechanically stirred for 10 hours. The tetrahydrofuran organic solvent in the reaction system was removed by vacuum rotary evaporation to obtain a light pink oily substance, i.e., a naphthyurea functionalized siloxane coupling agent; then, the light yellow oily substance was directly dissolved in 100 mL of anhydrous ethanol, and 0.605 g (2.5 mmol) of ferric nitrate was added to the solution as a template imprinted metal ion, and the temperature was controlled at 50°C and mechanically stirred for 18 hours under nitrogen protection; thereafter, the ethanol in the reaction system was removed by vacuum rotary evaporation again, and finally, a complex of a naphthyurea functionalized siloxane coupling agent monomer and an iron ion template, Nap(Fe)-1, was obtained.

[0032] (ii) 1.0 g of AQ(Fe)-1 in step 1 and 1.0 g of magnetic nanoparticles coated with silica prepared by coprecipitation were added to 150 mL of anhydrous ethanol, and then well dispersed under ultrasonic action. Under the protection of nitrogen atmosphere, the system temperature was controlled at 75°C for mechanical stirring for 18 hours. After the reaction system was cooled to room temperature, the magnetic suspended solids in the water were separated by the action of an external magnetic field. The obtained solid was first washed twice with tetrahydrofuran and then washed twice with ethanol to completely remove impurities. Finally, the washed solid was vacuum dried to obtain a magnetic nanoparticle material with a surface modified with a naphthyurea chromophore and coordinated with iron ions, which was recorded as Fe3O4-Nap(Fe)-1.

[0033] (III) adding 1.0 g of Fe3O4-Nap(Fe)-1 in step 2 to 180 mL of 0.8% dilute hydrochloric acid solution, and mechanically stirring at room temperature for 18 hours after ultrasonic dispersion, and centrifuging the product; washing the obtained solid with deionized water repeatedly for several times until the washed aqueous solution is close to neutral; and finally vacuum drying to obtain a naphthalene urea modified magnetic nanoparticle material based on surface ion imprinting technology, which is recorded as Fe3O4-Nap-IIA-1. The structural schematic diagram of the final product is as follows:

[0034]

[0035] Embodiment 2:

[0036] Preparation of naphthaleneurea modified magnetic nanoparticles Fe3O4-Nap-IIA-2 for fluorescent detection of iron ions, the specific steps are as follows:

[0037] (i) 1.026 g (5.0 mmol) of isocyanate propyl trimethoxysilane and 0.785 g (5.0 mmol) of 8-methyl-1-naphthylamine were added to a round-bottom flask containing 78.5 mL of dioxane. After mechanical stirring at 30°C for 12 hours, the dioxane organic solvent in the reaction system was removed by vacuum rotary evaporation to obtain a light pink oily substance, i.e., a naphthurea functionalized siloxane coupling agent; then, the light yellow oily substance was directly dissolved in 118 mL of anhydrous ethanol, and 0.605 g (2.5 mmol) of ferric nitrate was added to the solution as a template imprinted metal ion, and the temperature was controlled at 40°C under nitrogen protection and mechanical stirring was performed for 24 hours; thereafter, the ethanol in the reaction system was removed by vacuum rotary evaporation again, and finally, a complex of a naphthurea functionalized siloxane coupling agent monomer and an iron ion template, Nap(Fe)-2, was obtained.

[0038] (ii) 1.0 g of AQ(Fe)-2 in step 1 and 1.50 g of magnetic nanoparticles coated with silica prepared by coprecipitation were added to 180 mL of acetonitrile, and then well dispersed under ultrasonic action. Under the protection of nitrogen atmosphere, the system temperature was controlled at 70°C for mechanical stirring for 24 hours. After the reaction system was cooled to room temperature, the magnetic suspended solids in the water were separated by the action of an external magnetic field. The obtained solid was first washed twice with tetrahydrofuran and then washed twice with ethanol to completely remove impurities. Finally, the washed solid was vacuum dried to obtain a magnetic nanoparticle material with a surface modified with a naphthyurea chromophore and coordinated with iron ions, which was recorded as Fe3O4-Nap(Fe)-2.

[0039] (III) adding 1.0 g of ATP-Nap(Fe)-2 in step 2 to 150 mL of 1.0% dilute sulfuric acid solution, ultrasonically dispersing, mechanically stirring at room temperature for 12 hours, and centrifuging the product; washing the obtained solid with deionized water repeatedly for several times until the washed aqueous solution is close to neutral; finally, vacuum drying is performed to obtain a naphthalene urea modified magnetic nanoparticle material based on surface ion imprinting technology, which is recorded as Fe3O4-Nap-IIA-2. The structural schematic diagram of the final product is as follows:

[0040]

[0041] Embodiment 3:

[0042] A preparation method of naphthaleneurea modified magnetic nanoparticles Fe3O4-Nap-IIA-3 for fluorescent detection of iron ions, the specific steps are as follows:

[0043] (i) 0.956 g (5.0 mmol) of isocyanate ethyl trimethoxysilane and 0.785 g (5.0 mmol) of 5-methyl-1-naphthylamine were added to a round-bottom flask containing 118 mL of N,N-dimethylformamide. After mechanical stirring at 50°C for 8 hours, the N,N-dimethylformamide organic solvent in the reaction system was removed by vacuum rotary evaporation to obtain a light pink oily substance, i.e., a naphthyurea functionalized siloxane coupling agent. Then, the light yellow oily substance was directly dissolved in 78.5 mL of anhydrous ethanol, and 0.605 g (2.5 mmol) of ferric nitrate was added to the solution as a template imprinted metal ion. Under nitrogen protection, the temperature was controlled at 45°C and mechanical stirring was performed for 12 hours. Afterwards, the ethanol in the reaction system was removed by vacuum rotary evaporation again to finally obtain a complex of naphthyurea functionalized siloxane coupling agent monomer and iron ion template Nap(Fe)-3.

[0044] (ii) 1.0 g of AQ(Fe)-3 in step 1 and 1.08 g of magnetic nanoparticles coated with silica prepared by coprecipitation were added to 194 mL of toluene, and then well dispersed under ultrasonic action. Under the protection of nitrogen atmosphere, the system temperature was controlled at 90°C for mechanical stirring for 12 hours. After the reaction system was cooled to room temperature, the magnetic suspended solids in the water were separated by the action of an external magnetic field. The obtained solid was first washed twice with tetrahydrofuran and then washed twice with ethanol to completely remove impurities. Finally, the washed solid was vacuum dried to obtain a magnetic nanoparticle material with a surface modified with a naphthyurea chromophore and coordinated with iron ions, which was recorded as Fe3O4-Nap(Fe)-3.

[0045] (III) adding 1.0 g of ATP-Nap(Fe)-3 in step 2 to 200 mL of 0.3% dilute nitric acid solution, ultrasonically dispersing, mechanically stirring at room temperature for 24 hours, and centrifuging the product; washing the obtained solid with deionized water repeatedly for several times until the washed aqueous solution is close to neutral; finally, vacuum drying is performed to obtain a naphthalene urea modified magnetic nanoparticle material based on surface ion imprinting technology, which is recorded as Fe3O4-Nap-IIA-3. The structural schematic diagram of the final product is as follows:

[0046]

[0047] Embodiment 4:

[0048] A preparation of naphthalurea-modified magnetic nanoparticles Fe3O4-Nap-NIIA based on non-surface imprinting technology. The fluorescence detection performance of the probe material can be compared with that of the probe prepared based on surface ion imprinting technology. The difference between this embodiment and the above-mentioned embodiments 1 to 3 is that the naphthalurea-functionalized siloxane coupling agent obtained by the reaction does not coordinate with iron ions, and directly modifies the surface of the coated silica magnetic nanoparticles to obtain a naphthalurea-modified magnetic nanoparticle fluorescent probe material. The other conditions of this embodiment refer to Example 1, and the specific steps are as follows:

[0049] (i) 1.235 g (5.0 mmol) of isocyanate propyl triethoxysilane and 0.715 g (5.0 mmol) of 1-naphthylamine were added to a round-bottom flask containing 100 mL of tetrahydrofuran. After mechanical stirring at 40°C for 10 hours, the tetrahydrofuran organic solvent in the reaction system was removed by vacuum rotary evaporation to obtain a light pink oily substance, i.e., naphthurea functionalized siloxane coupling agent Nap-silane.

[0050] (ii) 1.0 g of Nap-silane in step 1 and 1.0 g of magnetic nanoparticles coated with silica prepared by co-precipitation method are added to 150 mL of anhydrous ethanol, and then well dispersed under the action of ultrasound. Under the protection of nitrogen atmosphere, the system temperature is controlled at 75°C and mechanically stirred for 18 hours. After the reaction system is cooled to room temperature, the magnetic suspended solids in the water are separated by the action of an external magnetic field. The obtained solid is first washed twice with tetrahydrofuran and then washed twice with ethanol to completely remove impurities. Finally, the washed solid is vacuum dried to obtain naphthalene urea modified magnetic nanoparticles based on non-surface imprinting technology, which are recorded as Fe3O4-Nap-NIIA.

[0051] Example 5: Electron Microscope Characterization

[0052] The naphthaleneurea modified magnetic nanoparticles Fe3O4-Nap-IIA-1 obtained in Example 1 for fluorescent detection of iron ions were characterized by transmission electron microscopy. The electron microscope photo clearly showed a core-shell structure with ferroferric oxide as the core and silicon dioxide as the shell. The particle size was about 20 to 30 nanometers, and there was a slight agglomeration phenomenon in the sample in the electron microscope photo ( Figure 1 ). This characterization result shows that the naphthalene urea modified magnetic nanoparticles Fe3O4-Nap-IIA-1 based on surface imprinting technology exhibits excellent structural stability, and its morphology remains basically unchanged even after chemical modification and acidic solution treatment.

[0053] When Fe3O4-Nap-IIA-1 was added to an aqueous solution and subjected to 0.5 minutes of ultrasonic treatment, it was effectively dispersed in water, and no significant precipitation was observed in the next half hour. This experimental result strongly verified that Fe3O4-Nap-IIA-1 exhibited excellent water dispersibility in water.

[0054] Example 6: Construction of fluorescent probe

[0055] The present invention studies the fluorescence response performance of Fe3O4-Nap-IIA-1 prepared in Example 1 to iron ions. Specifically, the experiment was carried out at 25°C, and 2.0 mL of iron ion solutions of different concentrations were added to 2.0 mL of Fe3O4-Nap-IIA-1 reserve dispersion (concentration of 0.2 mg / mL), and after uniform mixing, the concentration of Si-AQ-IIA-1 became 0.1 mg / mL. Subsequently, since iron ions are easily hydrolyzed and precipitated under neutral and alkaline conditions, the pH value of the solution was adjusted to 3.0, and fully dispersed by ultrasonic oscillation. Then, the dispersion was quickly transferred to a quartz cuvette to record its fluorescence emission spectrum at an excitation wavelength of 298 nm.

[0056] like Figure 2 As shown in the figure, as the iron ion concentration gradually increases from 0 mg / L to 2 mg / L, the fluorescence emission intensity of the Fe3O4-Nap-IIA-1 dispersion shows a continuous downward trend. During this process, the shape of the emission band remains basically unchanged, and the maximum emission wavelength is maintained at about 395 nm. Finally, the maximum fluorescence emission intensity of the aqueous dispersion of Fe3O4-Nap-IIA-1 in the presence of iron ions drops to 1 / 6 of the initial intensity. Thereafter, even if the concentration of iron ions continues to increase, the decrease in fluorescence intensity is not significant. Therefore, the fluorescence intensity of the aqueous dispersion of Fe3O4-Nap-IIA-1 is significantly quenched with the increase of iron ion concentration, so Fe3O4-Nap-IIA-1 can be used as an effective fluorescent probe for iron ion detection.

[0057] Example 7: Selectivity of fluorescence detection

[0058] The present invention studies the selectivity of Fe3O4-Nap-IIA-1 prepared in Example 1 for fluorescence detection of iron ions. The experiment was set at 25°C, and 2.0 mL of an interfering ion solution with a concentration of 4 mg / L was added to 2.0 mL of a Fe3O4-Nap-IIA-1 reserve dispersion (concentration of 0.2 mg / mL) prepared in Example 1. After uniform mixing, the concentration of Fe3O4-Nap-IIA-1 became 0.1 mg / mL, and the interfering ion concentration became 4 mg / L. Then, the pH value of the solution was adjusted to 3.0, and Fe3O4-Nap-IIA-1 was uniformly dispersed in water by ultrasonic oscillation. The resulting suspension was then transferred to a quartz cuvette, and the fluorescence emission intensity at 395 nm was recorded under 298 nm excitation light. In addition, a mixed solution containing 4 mg / L interfering ions and 4 mg / L iron ions was prepared, and the above test process was repeated. In order to evaluate the effect of surface ion imprinting technology on the selectivity of fluorescence detection, Fe3O4-Nap-NIIA prepared by non-ionic imprinting technology was used as a comparison nanoprobe material and the above test was also carried out.

[0059] like Figure 3 As shown in the figure, the presence of other interfering metal ions did not significantly change the fluorescence intensity of the suspension at 395 nm, indicating that Fe3O4-Nap-IIA-1 has excellent recognition specificity and anti-interference performance for iron ions. However, for Fe3O4-Nap-NIIA prepared by non-ionic imprinting technology, when no interfering ions were added, the fluorescence intensity of Fe3O4-Nap-NIIA was slightly lower than that of Fe3O4-Nap-IIA-1 (see Figure 4 ). The results show that Fe3O4-Nap-IIA-1 prepared based on ion imprinting exhibits a more significant and sensitive fluorescence quenching effect on the addition of iron ions in the solution. At the same time, the intensity of Fe3O4-Nap-NIIA after fluorescence quenching at 395nm after the addition of iron ions is slightly higher than that of Fe3O4-Nap-IIA-1. When interfering ions are added to the iron ion solution, the fluorescence intensity of Fe3O4-Nap-NIIA is much higher than when iron ions are present alone. The results show that the same interfering ions have a greater interference with the detection results of Fe3O4-Nap-NIIA prepared by non-ionic imprinting technology. Therefore, the use of surface ion imprinting technology significantly enhances the fluorescence detection selectivity of the nanoprobe material for iron ions in water.

[0060] This characteristic indicates that naphthaleneurea-modified magnetic nanoparticles for fluorescent detection of iron ions have broad application prospects in the field of selective fluorescent detection of iron ions in water.

Claims

1. A naphthaleneurea modified magnetic nanoparticle for fluorescent detection of iron ions, characterized in that: By using the surface ion imprinting method, a naphthalene urea fluorescent chromophore-imprinted cavity structure with high complementarity with the iron ions in shape and size is fixed on the surface of the magnetic nanoparticles to achieve specific action and fluorescence detection of the target iron ions. The general structural formula is as follows: in, Refers to the partial structure of the silica magnetic nanoparticles, where the dark part is the magnetic ferroferric oxide core and the light gray part is the silica shell. It is a specific imprinted cavity structure with high complementarity with the iron ion in shape and size, n is selected from one of the integers 1, 2 or 3, R is selected from one of the hydrogen atom or methyl group, and the substitution position is one of the four substitution sites on the benzene ring.

2. A method for preparing the naphthyurea modified magnetic nanoparticles for fluorescent detection of iron ions according to claim 1, characterized in that: The preparation method comprises the following steps: Step 1: add equal amounts of isocyanate functionalized siloxane coupling agent and naphthylamine compound to a round-bottom flask filled with an organic solvent, control the temperature within the range of 30 to 50° C., mechanically stir the reaction for 8 to 12 hours, and remove the organic solvent in the reaction system by vacuum rotary evaporation to obtain a light pink oily substance, i.e., a naphthurea functionalized siloxane coupling agent; then, directly dissolve the light yellow oily substance in anhydrous ethanol, and add a certain amount of ferric nitrate to the solution as a template imprinted metal ion, wherein the amount of ferric nitrate is half the amount of the naphthylamine compound, and control the temperature within the range of 40 to 50° C. and mechanically stir for 12 to 24 hours under nitrogen protection; then, remove the ethanol in the reaction system by vacuum rotary evaporation again, and finally obtain a complex of a naphthurea functionalized siloxane coupling agent monomer and an iron ion template, Nap(Fe), and the specific synthesis steps and reaction formulas are expressed as follows: Step 2: Add the Nap(Fe) in step 1 and the magnetic nanoparticles coated with silica prepared by the coprecipitation method into an organic solvent, and then achieve good dispersion under the action of ultrasound, and control the system temperature in the range of 70 to 90°C for mechanical stirring under the protection of a nitrogen atmosphere for 12 to 24 hours; after the reaction system is cooled to room temperature, the magnetic suspended solids in the water are separated by the action of an external magnetic field, and the obtained solid is first washed twice with tetrahydrofuran and then washed twice with ethanol to completely remove impurities; finally, the washed solid is vacuum dried to obtain a magnetic nanoparticle material with a surface modified with a naphthyurea chromophore and coordinated with iron ions, which is recorded as Fe3O4-Nap(Fe). The specific synthesis steps and reaction formulas are expressed as follows: Step 3: Add ATP-Nap(Fe) in step 2 to an inorganic acid solution, and then mechanically stir at room temperature for 12 to 24 hours after ultrasonic dispersion, and separate the product by centrifugation; the obtained solid is repeatedly washed with deionized water for several times until the aqueous solution after washing is close to neutral; finally, the naphthalene urea modified magnetic nanoparticle material based on surface ion imprinting technology is obtained by vacuum drying, which is recorded as Fe3O4-Nap-IIA. The specific synthesis steps and reaction formula are expressed as follows:

3. The method for preparing naphthaleneurea modified magnetic nanoparticles for fluorescent detection of iron ions according to claim 2, characterized in that: Step 1: the isocyanate functionalized siloxane coupling agent is selected from any one of isocyanate propyl triethoxysilane, isocyanate propyl trimethoxysilane, isocyanate ethyl triethoxysilane, isocyanate ethyl trimethoxysilane, isocyanate methyl triethoxysilane or isocyanate methyl trimethoxysilane; the naphthylamine compound is selected from 1-naphthylamine, 5-methyl-1-naphthylamine, 6-methyl-1-naphthylamine, 7-methyl-1-naphthylamine or 8-methyl -1-naphthylamine; the organic solvent is selected from any one of dichloromethane, chloroform, acetone, methanol, anhydrous ethanol, isopropanol, anisole, tetrahydrofuran, dioxane, acetonitrile, toluene or N,N-dimethylformamide; the solid-liquid mass volume ratio of the naphthylamine compound and the organic solvent is 1:100-150 g / mL; the solid-liquid mass volume ratio of the naphthylamine compound and the anhydrous ethanol for dissolving the yellow oil is 1:100-150 g / mL.

4. The method for preparing naphthaleneurea modified magnetic nanoparticles for fluorescent detection of iron ions according to claim 2, characterized in that: Step 2: The mass ratio of Nap(Fe) to magnetic nanoparticles is 1:1.0-1.5; the organic solvent is selected from any one of dichloromethane, chloroform, acetone, methanol, anhydrous ethanol, isopropanol, anisole, tetrahydrofuran, dioxane, acetonitrile, toluene or N,N-dimethylformamide; the solid-liquid mass volume ratio of the magnetic nanoparticles to the organic solvent is 1:120-180 g / mL.

5. The method for preparing naphthaleneurea modified magnetic nanoparticles for fluorescent detection of iron ions according to claim 2, characterized in that: Step 3: The inorganic acid solution is selected from any one of sulfuric acid, hydrochloric acid or nitric acid solution; the solid-liquid mass volume ratio of the ATP-Nap (Fe) to the inorganic acid solution is 1:150-200 g / mL; and the mass concentration of the inorganic acid is 0.3-1.0%.

6. The use of naphthyurea modified magnetic nanoparticles for fluorescent detection of iron ions according to claim 1, characterized in that: The urea groups on the surface of the naphthurea-modified magnetic nanoparticles will cause fluorescence quenching after combining with iron ions in water. Therefore, the naphthurea-modified magnetic nanoparticles based on surface imprinting technology can be used for selective fluorescence detection of iron ions in water.

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