A naphthaleneurea-modified magnetic nanoparticle for iron ion fluorescence detection and its preparation method

Abstract

This invention discloses a naphthalene-urea-modified magnetic nanoparticle for iron ion fluorescence detection and its preparation method. Utilizing surface ion imprinting technology, naphthalene-urea fluorescent chromophores are successfully imprinted on the surface of the magnetic nanoparticles, forming specific imprint sites that precisely match the shape and size of the template iron ions. The material preparation process is simple, and the prepared naphthalene-urea-modified magnetic nanoparticles combine the excellent nanocarrier properties of magnetic nanomaterials with the fluorescence detection advantages of naphthalene-urea fluorescent probes. The application of surface ion imprinting technology significantly enhances the selective binding ability of the naphthalene-urea chromophores to the target iron ions, enabling this probe material to exhibit good selectivity in the fluorescence detection of iron ions in water.

Description

Technical Field

[0001] This invention relates to the field of organic functionalization modification of magnetic nanoparticle surfaces, and particularly to a naphthaleneurea-modified magnetic nanoparticle ion fluorescent probe based on surface imprinting technology and its application, enabling selective fluorescence detection of iron ions in water. Background Technology

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

[0003] Currently, several promising small-molecule iron ion fluorescent probes have been developed. These probes typically exhibit high selectivity and sensitivity, performing excellently under laboratory conditions. However, they still face some challenges in practical applications. One of the most significant issues is that most reported small-molecule iron ion fluorescent probes are highly hydrophobic, often requiring organic solvents such as methanol, acetonitrile, and tetrahydrofuran for dissolution. The use of these organic solvents not only increases the complexity of the operation but also limits the direct application of the probes in pure water environments.

[0004] Therefore, to overcome this limitation, developing novel fluorescent probes for efficient and direct detection of iron ions in pure water remains a research direction worthy of in-depth exploration. In recent years, the covalent fixation of fluorescent groups onto inorganic nanomaterial supports has been introduced into the field of fluorescent probes as organic-inorganic hybrid optical probes. Magnetic nanoparticles, through adsorption stabilizers or charge modulation, can be dispersed in water for extended periods, preventing particle aggregation. Magnetic nanoparticles are easy to prepare and can be easily separated from the aqueous medium under an external magnetic field, facilitating material recovery and reuse. Meanwhile, the silica shell, rich in hydroxyl groups, can react with coupling agents to form stable covalent bonds with the fluorescent groups, effectively protecting the internal iron oxide core from corrosion by acidic environments.

[0005] Traditional ion-imprinted polymer materials are first prepared through the copolymerization reaction of functional monomers with coordinating template ions and crosslinking agents. The coordinating template ions are then removed, resulting in a specific imprinted cavity that highly matches the shape and size of the target ion. Surface imprinting technology based on sol-gel processes has also been developed, allowing the formation of a thin imprinted coating film containing imprinted cavities on the surface of inorganic materials. Most reported surface imprinting techniques typically introduce chelating groups onto inorganic supports with high specific surface areas to form specific imprinted cavities. These nanocomposites are primarily used for the selective adsorption of target metal ions. Introducing fluorescent probe molecules into the support surface using surface imprinting technology not only enables specific recognition of target ions in water but also allows for selective fluorescence detection and adsorption removal, demonstrating broad application potential in environmental protection. Based on this, this invention utilizes surface ion imprinting technology to prepare naphthaleneurea-modified magnetic nanoparticles as fluorescent probe materials for iron ions. This technology enables specific recognition and selective fluorescence detection of target iron ions in water, thereby improving the selectivity and sensitivity of the material for iron ion detection. Summary of the Invention

[0006] To address the limitations of existing small-molecule fluorescent probes in detecting target metal ions, this invention provides naphthaleneurea-modified magnetic nanoparticles for the fluorescence detection of iron ions and their preparation method. By employing surface ion imprinting, a naphthaleneurea fluorescent chromophore cavity structure with high complementarity to iron ions in shape and size is imprinted on the surface of the magnetic nanoparticles, achieving specific targeting and fluorescence detection of iron ions. The general structural formula is as follows:

[0007]

[0008] in, This refers to the partial structure of magnetic nanoparticles coated with silica, where the dark part is the magnetic magnetite core and the light gray part is the silica shell. To achieve a specific imprinted cavity structure that is highly complementary to the shape and size of iron ions, n is taken from one of the integers 1, 2 or 3, R is taken from one of the hydrogen atoms or methyl atoms, and the substitution position is one of the four substitution sites on the benzene ring.

[0009] This invention further provides a method for preparing the above-mentioned naphthaleneurea-modified magnetic nanoparticles for iron ion fluorescence detection, comprising the following steps:

[0010] Step 1: Equal amounts of isocyanate-functionalized siloxane coupling agent and naphthylamine compound are added to a round-bottom flask containing organic solvent. The temperature is controlled within the range of 30–50°C, and the mixture is mechanically stirred for 8–12 hours. The organic solvent in the reaction system is then removed by vacuum rotary evaporation to obtain a light pink oily substance, which is the naphthylurea-functionalized siloxane coupling agent. Next, this light yellow oily substance is directly dissolved in anhydrous ethanol, and a certain amount of ferric nitrate is added to the solution as a template-imprinted metal ion. The amount of ferric nitrate is half the amount of the naphthylamine compound. Under nitrogen protection, the mixture is mechanically stirred for 12–24 hours, controlling the temperature within the range of 40–50°C. Afterward, the ethanol in the reaction system is again removed by vacuum rotary evaporation, finally yielding Nap(Fe), a complex of the naphthylurea-functionalized siloxane coupling agent monomer and the iron ion template. The specific synthesis steps and reaction formulas are expressed below:

[0011]

[0012] Step 2: The Nap(Fe) from Step 1 and the silica-coated magnetic nanoparticles prepared by co-precipitation were added to an organic solvent. The mixture was then well dispersed under ultrasonication, and mechanically stirred at 70–90°C for 12–24 hours under a nitrogen atmosphere. After the reaction system cooled to room temperature, the magnetic suspended solids in the water were separated using an external magnetic field. The resulting solids were first washed twice with tetrahydrofuran, and then twice with ethanol to thoroughly remove impurities. Finally, the washed solids were vacuum dried to obtain a magnetic nanoparticle material with a surface modified with naphthalene urea chromophores and coordinated with iron ions, denoted as Fe3O4-Nap(Fe). The specific synthesis steps and reaction formulas are as follows:

[0013]

[0014] Step 3: Add ATP-Nap(Fe) from Step 2 to an inorganic acid solution, disperse by ultrasonication, and then mechanically stir at room temperature for 12–24 hours. Centrifuge the product. Wash the obtained solid repeatedly with deionized water until the aqueous solution is nearly neutral. Finally, vacuum dry to obtain naphthaleneurea-modified magnetic nanoparticles based on surface ion imprinting technology, denoted as Fe3O4-Nap-IIA. The specific synthesis steps and reaction formulas are expressed below:

[0015]

[0016] As a preferred embodiment of the present invention, the isocyanate-functionalized siloxane coupling agent in step one is selected from any one of isocyanate-propyltriethoxysilane, isocyanate-propyltrimethoxysilane, isocyanate-ethyltriethoxysilane, isocyanate-ethyltrimethoxysilane, isocyanate-methyltriethoxysilane, or isocyanate-methyltrimethoxysilane; the naphthylamine compound is selected from 1-naphthylamine, 5-methyl-1-naphthylamine, 6-methyl-1-naphthylamine, 7-methyl-1-naphthylamine, etc. The compound is selected from either 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 that dissolves the yellow oily substance is 1:100-150 g / mL.

[0017] As a preferred embodiment of the present invention, the mass ratio of Nap(Fe) to magnetic nanoparticles in step two is 1:1.0 to 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 to 180 g / mL.

[0018] As a preferred embodiment 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 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] An application of naphthalene-urea-modified magnetic nanoparticles for iron ion fluorescence detection is disclosed. The naphthalene-urea chromophores on the surface of the naphthalene-urea-modified magnetic nanoparticles exhibit fluorescence quenching after binding with iron ions in water. Therefore, these naphthalene-urea-modified magnetic nanoparticles based on surface imprinting technology can be used for selective fluorescence detection of iron ions in water.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention provides a naphthaleneurea-modified magnetic nanoparticle for the fluorescence detection of iron ions. The preparation method is simple, and the material can be easily separated from the aqueous medium under an applied magnetic field, facilitating its recovery and reuse. Furthermore, when the naphthaleneurea fluorescent chromophore forms a complex with iron ions as a surface modifier, the fluorescence intensity gradually decreases with increasing iron ion content. Therefore, the naphthaleneurea-modified magnetic nanoparticles provided by this invention are suitable for the quantitative fluorescence detection of iron ions in aqueous solutions.

[0022] This invention provides a naphthaleneurea-modified magnetic nanoparticle for the fluorescence detection of iron ions. Surface ion imprinting technology forms specific recognition sites on the material surface. These sites are highly complementary to iron ions in terms of shape and size. Under the presence of other interfering ions, the specific interaction with the target iron ion can be significantly improved, thereby enhancing the selectivity for quantitative fluorescence detection of iron ions in water. This solves the problem of limited selectivity for target ion detection in existing nanocomposite fluorescent probes. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 Transmission electron microscope image 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) of Fe3O4-Nap-IIA-1 prepared in Example 1 after the addition of iron ions in the presence of interfering ions is shown.

[0027] Figure 4 The fluorescence intensity (395 nm) of Fe3O4-Nap-IIA-1 prepared in Example 4 after the addition of iron ions in the presence of interfering ions is shown. Detailed Implementation

[0028] To further reveal the technical solutions of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0029] Example 1:

[0030] The preparation of naphthaleneurea-modified magnetic nanoparticles Fe3O4-Nap-IIA-1 for iron ion fluorescence detection is described in the following steps:

[0031] (i) 1.235 g (5.0 mmol) of isocyanate-propyltriethoxysilane and 0.715 g (5.0 mmol) of 1-naphthylamine were added to a round-bottom flask containing 100 mL of tetrahydrofuran. After stirring mechanically 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, which is the naphthylurea-functionalized siloxane coupling agent. Then, this 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. Under nitrogen protection, the mixture was stirred mechanically at 50 °C for 18 hours. Afterward, the ethanol in the reaction system was removed again by vacuum rotary evaporation to finally obtain the complex Nap(Fe)-1, which is a complex of the naphthylurea-functionalized siloxane coupling agent monomer and the iron ion template.

[0032] (II) 1.0 g of AQ(Fe)-1 and 1.0 g of silica-coated magnetic nanoparticles prepared by co-precipitation were added to 150 mL of anhydrous ethanol. The mixture was then well dispersed under ultrasonication and mechanically stirred at 75 °C for 18 hours under a nitrogen atmosphere. After the reaction system cooled to room temperature, the magnetic suspended solids in the water were separated by an external magnetic field. The resulting solids were first washed twice with tetrahydrofuran and then twice with ethanol to thoroughly remove impurities. Finally, the washed solids were vacuum dried to obtain magnetic nanoparticles with naphthalene urea chromophores and iron ions on their surface, denoted as Fe3O4-Nap(Fe)-1.

[0033] (III) 1.0 g of Fe3O4-Nap(Fe)-1 from step II was added to 180 mL of 0.8% dilute hydrochloric acid solution. After ultrasonic dispersion, the mixture was mechanically stirred at room temperature for 18 hours. The product was then centrifuged. The obtained solid was repeatedly washed with deionized water until the aqueous solution was nearly neutral. Finally, the naphthaleneurea-modified magnetic nanoparticle material based on surface ion imprinting technology was obtained by vacuum drying, denoted as Fe3O4-Nap-IIA-1. The structural diagram of the final product is shown below:

[0034]

[0035] Example 2:

[0036] The preparation of naphthaleneurea-modified magnetic nanoparticles Fe3O4-Nap-IIA-2 for iron ion fluorescence detection is described in the following steps:

[0037] (i) 1.026 g (5.0 mmol) of isocyanate-propyltrimethoxysilane 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 stirring mechanically 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, which is the naphthylurea-functionalized siloxane coupling agent. Then, this 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. Under nitrogen protection, the mixture was stirred mechanically at 40 °C for 24 hours. Afterward, the ethanol in the reaction system was removed again by vacuum rotary evaporation to finally obtain the complex Nap(Fe)-2 of the naphthylurea-functionalized siloxane coupling agent monomer and the iron ion template.

[0038] (II) 1.0 g of AQ(Fe)-2 and 1.50 g of silica-coated magnetic nanoparticles prepared by co-precipitation were added to 180 mL of acetonitrile. The mixture was then well dispersed under ultrasonication and mechanically stirred at 70 °C for 24 hours under a nitrogen atmosphere. After the reaction system cooled to room temperature, the magnetic suspended solids in the water were separated by an external magnetic field. The resulting solids were first washed twice with tetrahydrofuran and then twice with ethanol to thoroughly remove impurities. Finally, the washed solids were vacuum dried to obtain magnetic nanoparticles with naphthalene urea chromophores and iron ions on their surface, denoted as Fe3O4-Nap(Fe)-2.

[0039] (III) 1.0 g of ATP-Nap(Fe)-2 from step II was added to 150 mL of 1.0% dilute sulfuric acid solution. After ultrasonic dispersion, the mixture was mechanically stirred at room temperature for 12 hours. The product was then centrifuged. The obtained solid was repeatedly washed with deionized water until the aqueous solution was nearly neutral. Finally, the naphthaleneurea-modified magnetic nanoparticle material based on surface ion imprinting technology was obtained by vacuum drying, denoted as Fe3O4-Nap-IIA-2. The structural diagram of the final product is shown below:

[0040]

[0041] Example 3:

[0042] The preparation of naphthaleneurea-modified magnetic nanoparticles Fe3O4-Nap-IIA-3 for iron ion fluorescence detection is described in the following steps:

[0043] (i) 0.956 g (5.0 mmol) of isocyanate-based ethyltrimethoxysilane 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 stirring mechanically 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, which is the naphthurene-functionalized siloxane coupling agent. Then, this 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 mixture was stirred mechanically at 45 °C for 12 hours. Afterward, the ethanol in the reaction system was removed again by vacuum rotary evaporation to finally obtain the complex Nap(Fe)-3 of the naphthurene-functionalized siloxane coupling agent monomer and the iron ion template.

[0044] (II) 1.0 g of AQ(Fe)-3 and 1.08 g of silica-coated magnetic nanoparticles prepared by co-precipitation were added to 194 mL of toluene. The mixture was then well dispersed under ultrasonication and mechanically stirred at 90 °C for 12 hours under a nitrogen atmosphere. After the reaction system cooled to room temperature, the magnetic suspended solids in the water were separated by an external magnetic field. The resulting solids were first washed twice with tetrahydrofuran and then twice with ethanol to thoroughly remove impurities. Finally, the washed solids were vacuum dried to obtain magnetic nanoparticles with naphthalene urea chromophores and iron ions on their surface, denoted as Fe3O4-Nap(Fe)-3.

[0045] (III) 1.0 g of ATP-Nap(Fe)-3 from step II was added to 200 mL of 0.3% dilute nitric acid solution. After ultrasonic dispersion, the mixture was mechanically stirred at room temperature for 24 hours. The product was then centrifuged. The obtained solid was repeatedly washed with deionized water until the aqueous solution was nearly neutral. Finally, the naphthaleneurea-modified magnetic nanoparticle material based on surface ion imprinting technology was obtained by vacuum drying, denoted as Fe3O4-Nap-IIA-3. The structural diagram of the final product is shown below:

[0046]

[0047] Example 4:

[0048] A method for preparing naphthaleneurea-modified magnetic nanoparticles (Fe3O4-Nap-NIIA) based on non-surface imprinting technology is disclosed. The fluorescence detection performance of this probe material can be compared with that of probes prepared based on surface ion imprinting technology. This embodiment differs from Embodiments 1-3 in that the naphthaleneurea-functionalized siloxane coupling agent obtained in the reaction does not coordinate with iron ions, directly modifying the surface of silica-coated magnetic nanoparticles to obtain a naphthaleneurea-modified magnetic nanoparticle fluorescent probe material. Other conditions in this embodiment are the same as in Embodiment 1, and the specific steps are as follows:

[0049] (a) 1.235 g (5.0 mmol) of isocyanate-propyltriethoxysilane 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, namely the naphthaleneurea-functionalized siloxane coupling agent Nap-silane.

[0050] (II) 1.0 g of Nap-silane and 1.0 g of silica-coated magnetic nanoparticles prepared by co-precipitation were added to 150 mL of anhydrous ethanol. The mixture was then well dispersed under ultrasonication and mechanically stirred at 75 °C for 18 hours under a nitrogen atmosphere. After the reaction system cooled to room temperature, the magnetic suspended solids in the water were separated by an external magnetic field. The resulting solids were first washed twice with tetrahydrofuran and then twice with ethanol to thoroughly remove impurities. Finally, the washed solids were vacuum dried to obtain naphthalene-urea modified magnetic nanoparticles based on non-surface imprinting technology, denoted as Fe3O4-Nap-NIIA.

[0051] Example 5: Electron Microscopy Characterization

[0052] The naphthaleneurea-modified magnetic nanoparticles Fe3O4-Nap-IIA-1 obtained in Example 1 for iron ion fluorescence detection were characterized by transmission electron microscopy. The electron microscope images clearly showed a core-shell structure with iron(III) oxide as the core and silicon dioxide as the shell. The overall particle size was approximately 20-30 nanometers, and slight aggregation was observed in the electron microscope images. Figure 1 This characterization result shows that the naphthaleneurea-modified magnetic nanoparticles Fe3O4-Nap-IIA-1 based on surface imprinting technology exhibit excellent structural stability, and their morphology remains basically unchanged even after chemical modification and treatment with acidic solutions.

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

[0054] Example 6: Construction of Fluorescent Probes

[0055] This invention investigated the fluorescence response of Fe3O4-Nap-IIA-1 prepared in Example 1 to iron ions. Specifically, the experiment was conducted at 25°C. 2.0 mL of iron ion solutions of different concentrations were added to 2.0 mL of Fe3O4-Nap-IIA-1 stock dispersion (concentration 0.2 mg / mL). After thorough mixing, the concentration of Si-AQ-IIA-1 became 0.1 mg / mL. Subsequently, since iron ions readily hydrolyze and precipitate under neutral and alkaline conditions, the pH of the solution was adjusted to 3.0, and thorough dispersion was achieved by ultrasonic oscillation. Immediately afterwards, the dispersion was rapidly transferred to a quartz cuvette to record its fluorescence emission spectrum at an excitation wavelength of 298 nm.

[0056] like Figure 2 As shown, with the iron ion concentration gradually increasing from 0 mg / L to 2 mg / L, the fluorescence emission intensity of the Fe3O4-Nap-IIA-1 dispersion showed a continuous decreasing trend, while the shape of the emission band remained basically unchanged during this process, and the maximum emission wavelength remained around 395 nm. Ultimately, the maximum fluorescence emission intensity of the Fe3O4-Nap-IIA-1 aqueous dispersion in the presence of iron ions decreased to 1 / 6 of the initial intensity. Thereafter, even with further increases in the iron ion concentration, the decrease in fluorescence intensity was not significant. Therefore, the fluorescence intensity of the Fe3O4-Nap-IIA-1 aqueous dispersion exhibits significant quenching with increasing iron ion concentration, thus Fe3O4-Nap-IIA-1 can serve as an effective fluorescent probe for iron ion detection.

[0057] Example 7: Selectivity of Fluorescence Detection

[0058] This invention investigated the selectivity of Fe3O4-Nap-IIA-1 prepared in Example 1 for the fluorescence detection of iron ions. The experiment was conducted at 25°C. 2.0 mL of an interfering ion solution with a concentration of 4 mg / L was added to 2.0 mL of the Fe3O4-Nap-IIA-1 stock dispersion (concentration 0.2 mg / mL) prepared in Example 1. After thorough mixing, the concentration of Fe3O4-Nap-IIA-1 became 0.1 mg / mL, and the concentration of the interfering ion became 4 mg / L. The pH of the solution was then 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. Furthermore, a mixed solution containing 4 mg / L interfering ions and 4 mg / L iron ions was prepared, and the above test procedure was repeated. To evaluate the impact of surface ion imprinting on the selectivity of fluorescence detection, Fe3O4-Nap-NIIA prepared by non-ion imprinting was used as a control nanoprobe material, and the same tests were performed.

[0059] like Figure 3 As shown, the presence of other interfering metal ions did not significantly alter the fluorescence intensity of the suspension at 395 nm, indicating that Fe3O4-Nap-IIA-1 possesses excellent recognition specificity and anti-interference performance for iron ions. However, for Fe3O4-Nap-NIIA prepared by non-ion imprinting, the fluorescence intensity of Fe3O4-Nap-NIIA was slightly lower than that of Fe3O4-Nap-IIA-1 without the addition of interfering ions (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 upon the addition of iron ions in solution. Simultaneously, the fluorescence intensity of Fe3O4-Nap-IIA-1 after fluorescence quenching at 395 nm is slightly higher than that of Fe3O4-Nap-IIA-1 after the addition of iron ions. When interfering ions are added to the iron ion solution, the fluorescence intensity of Fe3O4-Nap-IIA-1 is much higher than that when iron ions are present alone. This result indicates that the same interfering ions cause greater interference to the detection results of Fe3O4-Nap-IIA-1 prepared by non-ion imprinting technology. Therefore, the application of surface ion imprinting technology significantly enhances the fluorescence detection selectivity of this nanoprobe material for iron ions in water.

[0060] This characteristic suggests that naphthalene-urea-modified magnetic nanoparticles for iron ion fluorescence detection have broad application prospects in the field of selective fluorescence detection of iron ions in water.

Claims

1. A naphthylurea modified magnetic nanoparticle for fluorescent detection of iron ions, characterized by: The naphthylurea fluorescent chromophore imprinting cavity structure with high complementarity in shape and size to iron ions is fixed on the surface of magnetic nanoparticles by surface ion imprinting method to realize specific action and fluorescence detection of target iron ions, and the structural general formula is expressed as follows: wherein, Refers to the partial structure of silica-coated magnetic nanoparticles, where the dark part is the magnetic ferroferric oxide core, and the light gray part refers to the silica shell, is a specific imprinted cavity structure with high complementarity in shape and size to iron ions, n is taken from one of the integers 1, 2 or 3, R is taken from one of 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 naphthylurea-modified magnetic nanoparticle for fluorescence detection of iron ions according to claim 1, characterized by, The preparation method comprises the following steps: Step one, equal amounts of isocyanate functionalized siloxane coupling agent and naphthylamine compound are added into a round-bottom flask containing an organic solvent, the temperature is controlled in the range of 30-50 DEG C, and mechanical stirring is carried out for 8-12 hours, then the organic solvent in the reaction system is removed by vacuum rotary evaporation to obtain a light pink oil, i.e. naphthylurea functionalized siloxane coupling agent; then, the light yellow oil is directly dissolved in anhydrous ethanol, and a certain amount of ferric nitrate is added to the solution as a template imprinting metal ion, wherein the amount of substance of ferric nitrate is half of that of the naphthylamine compound, and mechanical stirring is carried out under nitrogen protection at a temperature of 40-50 DEG C for 12-24 hours; then, the ethanol in the reaction system is removed again by vacuum rotary evaporation, and finally the complex of naphthylurea functionalized siloxane coupling agent monomer and iron ion template Nap(Fe) is obtained, and the specific synthesis steps and reaction formula are expressed as follows: Step two, Nap(Fe) in step one and magnetic nanoparticles coated with silicon dioxide prepared by the coprecipitation method are added to an organic solvent, then good dispersion is realized under ultrasonic action, and mechanical stirring is carried out under nitrogen atmosphere protection at a temperature of 70-90 DEG C for 12-24 hours; after the reaction system is cooled to room temperature, the magnetic suspension solid in water is separated under 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 magnetic nanoparticle materials modified with naphthylurea chromophore and coordinated with iron ions, denoted as Fe3O4-Nap(Fe), and the specific synthesis steps and reaction formula are expressed as follows: Step three, ATP-Nap(Fe) in step two is added to an inorganic acid solution, ultrasonic dispersion is carried out, and mechanical stirring is carried out at room temperature for 12-24 hours, and the product is centrifuged; the obtained solid is repeatedly washed with deionized water until the washed aqueous solution is close to neutral; finally, naphthylurea modified magnetic nanoparticle materials based on surface ion imprinting technology are obtained by vacuum drying, denoted as Fe3O4-Nap-IIA, and the specific synthesis steps and reaction formula are expressed as follows: Step three, ATP-Nap(Fe) in step two is added to an inorganic acid solution, ultrasonic dispersion is carried out, and mechanical stirring is carried out at room temperature for 12-24 hours, and the product is centrifuged; the obtained solid is repeatedly washed with deionized water until the washed aqueous solution is close to neutral; finally, naphthylurea modified magnetic nanoparticle materials based on surface ion imprinting technology are obtained by vacuum drying, denoted as Fe3O4-Nap-IIA, and the specific synthesis steps and reaction formula are expressed as follows:

3. The method according to claim 2, wherein the method is characterized by: The isocyanate functionalized siloxane coupling agent in step one 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 any one of 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, trichloromethane, acetone, methanol, anhydrous ethanol, isopropyl alcohol, 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 dissolving the yellow oil is 1:100-150 g / mL.

4. The method according to claim 2, wherein the method is characterized by: The mass ratio of the Nap(Fe) and the magnetic nanoparticle in step two is 1:1.0-1.5; the organic solvent is selected from any one of dichloromethane, trichloromethane, acetone, methanol, anhydrous ethanol, isopropyl alcohol, anisole, tetrahydrofuran, dioxane, acetonitrile, toluene or N,N-dimethylformamide; the solid-liquid mass volume ratio of the magnetic nanoparticle and the organic solvent is 1:120-180 g / mL.

5. The method according to claim 2, wherein the method is characterized by: 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 ATP-Nap(Fe) and the inorganic acid solution is 1:150-200 g / mL; the mass concentration of the inorganic acid is 0.3-1.0%. 6.The application of naphthylurea modified magnetic nanoparticles for fluorescent detection of iron ions according to claim 1, characterized in that: The urea group on the surface of the naphthylurea modified magnetic nanoparticle will be quenched after combining with iron ions in water, so the naphthylurea modified magnetic nanoparticle based on the surface imprinting technology can be used for selective fluorescence detection of iron ions in water.

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