A magnetic-chiral nanoparticle with locally modulated optical activity, its preparation method and application

Abstract

This invention discloses a method for preparing and applying magnetic-chiral nanoparticles with locally modulated optical activity using a magnetic field, belonging to the field of chiral optical materials technology. The method involves mixing an organic solution containing non-chiral magnetic Fe3O4 nanoparticles and an aqueous solution containing superparamagnetic-chiral Co3O4 nanoparticles, adjusting the pH of the mixed solution, initiating a vortex reaction, followed by sedimentation, centrifugation, and washing to obtain the magnetic-chiral nanoparticles. This invention allows for the control of the optical signal intensity of the superparamagnetic-chiral Co3O4 nanoparticles in their shell by altering the particle size or concentration of the non-chiral Fe3O4 nanoparticles, and also allows for simple control of the optical activity of the nanomaterials by changing the applied magnetic field.

Description

Technical Field

[0001] This invention belongs to the field of chiral optical materials technology, and in particular relates to a magnetic-chiral nanoparticle with local magnetic field-controlled optical activity, its preparation method and application. Background Technology

[0002] Chiral materials have made significant contributions to human technological progress in fields such as medicine, asymmetric synthesis, and security and anti-counterfeiting. The precise construction of intelligent responsive chiral nanomaterials (such as magnetically responsive chiral nanomaterials) is of great importance for fields such as electron spin devices, chiral resolution, asymmetric catalysis, magnetochemistry, and biomedicine. However, currently, the dynamic control of chiral materials mainly relies on irreversible changes in their chemical structure. Synthesizing nanomaterials that combine magnetism and chirality, and using magnetic fields or circularly polarized light to modulate the magnetic transition dipole moment of the material's polarization state, allows for real-time control of its catalytic activity, magnetic properties, biological activity, and chiral properties.

[0003] In recent years, the main synthetic strategies for magnetic-chiral nanomaterials have included: 1) surface functionalization of magnetic nanoparticles and chiral ligand exchange; 2) bottom-up synthesis of magnetic-chiral nanoparticles induced by chiral molecules; 3) self-assembly of assemblies with chiral helical structures induced by chiral templates; and 4) asymmetric arrangement of magnetic nanoparticles on the material surface. As a result, a series of superparamagnetic-chiral nanoparticles with good dispersibility, recyclability, and biocompatibility have been successfully prepared and widely applied in magnetic resonance imaging (MRI), nanomedicine delivery, and catalysis. However, the synthesis of iron / ferrimagnetic-chiral nanoparticles (such as chiral Fe3O4 nanoparticles) that exhibit rapid and reversible magnetic responses to external stimuli still faces significant challenges.

[0004] Currently, the synthesis processes for achiral Fe3O4 nanoparticles (ferromagnetic / ferrimagnetic) with different morphologies and sizes are quite mature. For magnetic-chiral Fe3O4 nanoparticles, the main synthesis methods are: 1) chiral ligand-driven synthesis of nanoparticles; 2) chiral ligand exchange on the surface of magnetic nanoparticles—often using chiral molecules containing thiol groups (such as cysteine ​​(Cys), penicillamine (Pen), and glutathione (GSH); 3) grafting chiral ligands via chemical coupling reactions (such as EDC-NHS). As mentioned above, surface chiral ligand exchange is the most classic method, but effectively preventing the spontaneous aggregation of magnetic nanoparticles during ligand exchange is key to successful surface functionalization. Furthermore, preventing the Fe on the particle surface during ligand exchange is crucial. 2+Oxidation is key to preserving the magnetism of chiral Fe3O4 nanoparticles. Currently, most literature reports that chiral Fe3O4 nanoparticles exhibit weak optical activity, with surface ligand signals detected only in the ultraviolet region. Therefore, effectively endowing ferromagnetic or ferrimagnetic nanoparticles with chirality is crucial for their successful synthesis. The paper "Magnetic Field Tuning Ionic Current Generated by Chiromagnetic Nanofilms" (J.Cai, J.Zhao, X.Gao, W.Ma, D.Meng, H.Zhang, C.Hao, M.Sun, L.Xu, L.Xu..ACS Nano 2022, 16, 7, 11066-11075.) describes a ligand exchange method to modify the surface of paramagnetic Fe3O4 nanoparticles with chiral acid (D / L-tartaric acid). The resulting nanoparticles exhibit weak optical activity, with surface ligand signals detected only in the ultraviolet region.

[0005] Therefore, there is an urgent need in this field for a method to prepare magnetic-chiral nanoparticles that combine strong magnetic properties with strong optical activity. Summary of the Invention

[0006] The purpose of this invention is to provide a magnetic-chiral nanoparticle with locally modulated optical activity, its preparation method, and its application, thereby solving the problems existing in the prior art. This invention uses achiral magnetic Fe3O4 nanoparticles as the magnetic core and superparamagnetic-chiral Co3O4 nanoparticles as chiral ligands. Surface adsorption with strong optical activity is achieved through ligand exchange (the surface ligand of the achiral magnetic Fe3O4 nanoparticles is oleic acid), i.e., magnetic interaction. The preparation method provided by this invention is simple to operate and low in cost. The magnetic-chiral nanoparticles obtained in this way have strong optical activity. After magnetization with an external parallel magnetic field, a local magnetic field can be obtained, which can be used to modulate the optical activity of the magnetic-chiral nanoparticles.

[0007] One of the technical solutions provided by this invention:

[0008] A type of magnetic-chiral nanoparticle with locally modulated optical activity, using non-chiral magnetic Fe3O4 nanoparticles as the magnetic core and superparamagnetic-chiral Co3O4 nanoparticles as the chiral ligand layer.

[0009] Since the synthesis of superparamagnetic-chiral Co3O4 nanoparticles is simple and technically mature, and can be obtained by one-pot method with stirring for 2 hours at room temperature, superparamagnetic-chiral Co3O4 nanoparticles with strong chiral optical activity can be obtained. Therefore, this invention selects superparamagnetic-chiral Co3O4 nanoparticles as the chiral ligand layer.

[0010] The second technical solution provided by this invention:

[0011] A method for preparing magnetic-chiral nanoparticles with locally modulated optical activity involves mixing an organic solution containing non-chiral magnetic Fe3O4 nanoparticles and an aqueous solution containing superparamagnetic-chiral Co3O4 nanoparticles, adjusting the pH of the mixed solution to alkaline, performing a vortex reaction, sedimentation, centrifugation, and washing to obtain the magnetic-chiral nanoparticles.

[0012] Preferably, the non-chiral magnetic Fe3O4 nanoparticles have a particle size of 70-140 nm.

[0013] When the particle size of non-chiral magnetic Fe3O4 nanoparticles is too large, the magnetic nanoparticles tend to spontaneously aggregate and are difficult to disperse, making it impossible to carry out effective ligand exchange. Magnetic nanoparticles are paramagnetic, and if the particle size is too small, they cannot retain their magnetism after magnetization and cannot use their own local magnetic field to regulate the optical activity of the outer ligands.

[0014] Preferably, the superparamagnetic-chiral Co3O4 nanoparticles have a particle size of 3-5 nm.

[0015] When the particle size of superparamagnetic-chiral Co3O4 nanoparticles is too large, they will aggregate; when the particle size is too small, they will have no magnetic responsiveness.

[0016] Preferably, the concentration ratio of non-chiral magnetic Fe3O4 nanoparticles to superparamagnetic-chiral Co3O4 nanoparticles in the mixed solution is (1-10):(4-20).

[0017] Adding too many non-chiral magnetic Fe3O4 nanoparticles will result in incomplete ligand exchange, while adding too few will result in insufficient magnetic responsiveness.

[0018] Preferably, the pH is 8-12.

[0019] Preferably, the preparation method of the non-chiral magnetic Fe3O4 nanoparticles is as follows: an iron oleate complex is prepared using FeCl3·6H2O and sodium oleate as raw materials, the iron oleate complex is added to octadecene, and the mixture is heated and stirred to obtain non-chiral magnetic Fe3O4 nanoparticles.

[0020] Preferably, the preparation method of the superparamagnetic-chiral Co3O4 nanoparticles is as follows: using CoCl2, sodium citrate and NaBH4 (sodium borohydride) as raw materials, adding chiral ligands, stirring at room temperature, and synthesizing superparamagnetic-chiral Co3O4 nanoparticles.

[0021] Preferably, the chiral ligand includes one or more of Cys (cystine), Pen (penicillamine), and GSH (glutathione).

[0022] There are many types of chiral amino acids. The reason why the above three amino acids were selected in this invention is that they contain thiol groups, have high reactivity, and can endow Co3O4 nanoparticles with strong optical activity.

[0023] The third technical solution provided by this invention:

[0024] Application of the above-mentioned magnetic-chiral nanoparticles with local magnetic field-modulated optical activity in the preparation of hydrogels.

[0025] This invention disperses and solidifies the prepared magnetic-chiral nanoparticles in a hydrogel, then places them in a parallel external magnetic field for directional magnetization, thereby controlling the magnetic dipole moment of the magnetic-chiral nanoparticles. When the external magnetic field is removed, due to the inherent properties of ferromagnetic materials, the magnetic dipole moment remains unchanged and parallel to the external magnetic field. Thus, the magnetic nucleus of the nanoparticles can generate a local magnetic field. This local magnetic field can be used to control the optical activity of the superparamagnetic-chiral Co3O4 nanoparticles surrounding the magnetic nucleus. The magnetized gel can be used as a local magnetic field. Adding other functional nanomaterials to this hydrogel can form other functionalized optical materials.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] The preparation method provided by this invention, by using paramagnetic-chiral Co3O4 nanoparticles as chiral ligands, can prevent Fe from forming on the particle surface. 2+ The oxidation process preserves the magnetism of the non-chiral magnetic Fe3O4 nanoparticles.

[0028] This invention uses non-chiral magnetic Fe3O4 nanoparticles as the magnetic core and superparamagnetic-chiral Co3O4 nanoparticles as the chiral ligand layer. The process of this invention is simple, the required reagents are readily available, and it can achieve efficient, rapid and large-scale preparation.

[0029] This invention can regulate the optical signal intensity of superparamagnetic-chiral Co3O4 nanoparticles in their shells by changing the size or concentration of non-chiral magnetic Fe3O4 nanoparticles, and can also easily regulate the optical activity of nanomaterials by changing the applied magnetic field.

[0030] The nanoparticles are dispersed in a hydrogel and magnetized by an external magnetic field to generate a local magnetic field. The optical activity of the magnetic chiral nanoparticles can be tuned by changing the morphology and size of the Fe3O4 nanoparticles, the concentration of the magnetic chiral nanoparticles, and the strength of the external magnetic field. The present invention disperses the prepared magnetic chiral nanoparticles in a hydrogel and magnetizes them by an external magnetic field to generate a local magnetic field. The magnetized gel can be used as a local magnetic field. Other functional nanomaterials can be added to the hydrogel to form other functionalized optical materials. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in 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.

[0032] Figure 1 The CD spectra of the magnetic-chiral nanoparticle solutions prepared in Examples 1-4 are shown.

[0033] Figure 2 The CD spectra of the magnetic-chiral nanoparticle gels prepared in Examples 1-4 after magnetization;

[0034] Figure 3 CD spectra of magnetic-chiral nanoparticle solutions prepared in Comparative Examples 1-4 and Example 1;

[0035] Figure 4 The CD spectra of the magnetic-chiral nanoparticle gels prepared in Comparative Examples 1-4 and Example 1 after magnetization are shown. Detailed Implementation

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0038] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0040] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0041] The room temperature in this invention refers to 25±2℃.

[0042] This invention utilizes CoCl2, sodium citrate, and NaBH4 as raw materials, adding different chiral ligands (including one or more of Cys, Pen, and GSH) to synthesize superparamagnetic-chiral Co3O4 nanoparticles with stable chiral optical properties and magnetic responsiveness. Using FeCl3·6H2O and sodium oleate as raw materials, an iron oleate complex is synthesized. Based on the iron oleate complex, by controlling the reaction conditions, non-chiral magnetic Fe3O4 nanoparticles with different morphologies and sizes are synthesized. Using non-chiral Fe3O4 nanoparticles as the magnetic core to provide a local magnetic field, a ligand exchange strategy is employed, with superparamagnetic-chiral Co3O4 nanoparticles acting as the extranuclear ligands. By optimizing the ligand exchange conditions, magnetic-chiral nanoparticles with locally regulated optical activity are prepared.

[0043] This invention involves dispersing and solidifying magnetic-chiral nanoparticles in a hydrogel, then subjecting them to directional magnetization in a parallel external magnetic field to modulate the magnetic dipole moment of the material. When the external magnetic field disappears, due to the inherent properties of ferromagnetic materials, the magnetic dipole moment remains unchanged and parallel to the applied magnetic field. This allows the magnetic nucleus of the nanoparticles to generate a local magnetic field. This local magnetic field can then be used to modulate the optical activity of the superparamagnetic-chiral Co3O4 nanoparticles surrounding the magnetic nucleus. The magnetized gel can be used as a local magnetic field. Adding other functional nanomaterials to this hydrogel can create other functionalized optical materials.

[0044] Example 1

[0045] 1) Preparation of superparamagnetic-chiral Co3O4 nanoparticles:

[0046] Add 60 mL of ultrapure water, 8 mL of L-Cys (100 mM / L) aqueous solution, 8 mL of sodium citrate (100 mM / L) aqueous solution, and 4 mL of CoCl2 (200 mM / L) aqueous solution to a 250 mL three-necked flask. After mixing, add 10 mL of NaBH4 (100 mM / L) aqueous solution dropwise. After the NaBH4 aqueous solution is added, the mixed solution changes from an orange transparent solution to a brown solution. The reaction system is stirred at room temperature for 2 h. After the reaction is completed, a brown solution is obtained. Add 7 times the volume of isopropanol solution to the reaction solution to precipitate the synthesized superparamagnetic-chiral Co3O4 nanoparticles. Centrifuge at 10000 rpm for 20 min, collect the solid, wash the sample twice with a water / isopropanol (v / v, 1 / 7) mixed solution, disperse the obtained solid sample in 10 mL of ultrapure water, and store it in a refrigerator at 4 °C for later use.

[0047] 2) Preparation of non-chiral magnetic Fe3O4 nanoparticles:

[0048] FeCl3·6H2O (10.8 g, 40 mmol) and sodium oleate (36.5 g, 120 mmol) were dissolved in a mixed solvent consisting of 80 mL ethanol, 60 mL distilled water, and 140 mL n-hexane. The mixture was heated to 70 °C and maintained for 4 h. After the heating was complete, the reaction was stopped, and the layers were separated. The organic layer was washed three times with 30 mL distilled water, and the solvent was evaporated to obtain a waxy solid ferric oleate complex. The ferric oleate complex (36 g, 40 mmol) and oleic acid (5.7 g, 20 mmol) were dissolved in 200 g of 1-octadecene. The reaction system was heated to 290°C at a rate of 20°C / min (when the reaction temperature reaches 290°C, the reaction intensifies, and the initially transparent solution becomes a turbid brownish-black solution), and kept at 290°C for 1 hour. The reaction solution was then cooled to room temperature, and 500 mL of ethanol was added to the reaction solution to precipitate the nanoparticles. The non-chiral magnetic Fe3O4 nanoparticles were obtained by centrifugation (nanoparticles of different sizes were obtained by controlling the temperature and reaction time: particle size 70-140 nm, including 70 nm, 110 nm, and 140 nm, for use in this example, examples 2-4, and comparative examples 1-4). The obtained nanoparticles were dispersed in 10 mL of n-hexane solution and stored in a -20°C refrigerator for later use.

[0049] 3) Preparation of magnetic-chiral nanoparticles:

[0050] Two mL of hexane solution containing 70 nm non-chiral Fe3O4 nanoparticles (prepared via step 2) dispersed in n-hexane, 10 mL of aqueous solution containing 3-5 nm superparamagnetic chiral Co3O4 nanoparticles dispersed in ethanol, and 2 mL of ethanol were added to a 50 mL centrifuge tube. The concentration ratio of non-chiral Fe3O4 nanoparticles to superparamagnetic chiral Co3O4 nanoparticles was 1 mg / mL:4 mg / mL. Tetramethylammonium hydroxide was added to adjust the pH of the solution to 12. The mixture was then vortexed for 0.5 h. Five volumes of isopropanol solution were added to the reaction solution to precipitate the nanoparticles. The mixture was centrifuged at 8000 rpm for 10 min, and the solid was collected. The sample was washed twice with a water / isopropanol (v / v, 1 / 5) mixture. The resulting solid was labeled Fe3O4@Co3O4-L-Cys. The sample was dispersed in 10 mL of ultrapure water and stored at 4 °C for later use.

[0051] Example 2

[0052] 1) Preparation of superparamagnetic-chiral Co3O4 nanoparticles:

[0053] Add 60 mL of ultrapure water, 8 mL of D-Cys (100 mM / L) aqueous solution, 8 mL of sodium citrate (100 mM / L) aqueous solution, and 4 mL of CoCl2 (200 mM / L) aqueous solution to a 250 mL three-necked flask. After mixing, add 10 mL of NaBH4 (100 mM / L) aqueous solution dropwise. After the NaBH4 aqueous solution is added, the mixed solution changes from an orange transparent solution to a brown solution. The reaction system is stirred at room temperature for 2 h. After the reaction is completed, a brown solution is obtained. Add 7 times the volume of isopropanol solution to the reaction solution to precipitate the synthesized superparamagnetic-chiral Co3O4 nanoparticles. Centrifuge at 10000 rpm for 20 min, collect the solid, wash the sample twice with a water / isopropanol (v / v, 1 / 7) mixed solution, disperse the obtained solid sample in 10 mL of ultrapure water, and store it in a refrigerator at 4 °C for later use.

[0054] 2) Preparation of magnetic-chiral nanoparticles:

[0055] Two mL of hexane solution containing achiral magnetic Fe3O4 nanoparticles (using achiral magnetic Fe3O4 nanoparticles with a particle size of 110 nm prepared in Example 1), 10 mL of aqueous solution containing superparamagnetic-chiral Co3O4 nanoparticles (particle size of 3-5 nm), and 2 mL of ethanol were added to a 50 mL centrifuge tube. The concentration ratio of achiral magnetic Fe3O4 nanoparticles to superparamagnetic-chiral Co3O4 nanoparticles was 3 mg / mL: 15 mg / mL. Tetramethylammonium hydroxide was added to adjust the pH of the solution to 12. The reaction was then vortexed for 0.5 h. Five volumes of isopropanol solution were added to the reaction solution to precipitate the nanoparticles, and the mixture was centrifuged at 8000 rpm for 10 min. The solid was collected, washed twice with a water / isopropanol (v / v, 1 / 5) mixture, and the resulting solid was labeled Fe3O4@Co3O4-D-Cys. The sample was dispersed in 10 mL of ultrapure water and stored at 4 °C for later use.

[0056] Example 3

[0057] 1) Preparation of superparamagnetic-chiral Co3O4 nanoparticles:

[0058] Add 60 mL of ultrapure water, 8 mL of Pen (100 mM / L) aqueous solution, 8 mL of sodium citrate (100 mM / L) aqueous solution, and 4 mL of CoCl2 (200 mM / L) aqueous solution to a 250 mL three-necked flask. After mixing, add 10 mL of NaBH4 (100 mM / L) aqueous solution dropwise. After the NaBH4 aqueous solution is added, the mixed solution changes from an orange transparent solution to a brown solution. The reaction system is stirred at room temperature for 2 h. After the reaction is completed, a brown solution is obtained. Add 7 times the volume of isopropanol solution to the reaction solution to precipitate the synthesized superparamagnetic-chiral Co3O4 nanoparticles. Centrifuge at 10000 rpm for 20 min, collect the solid, wash the sample twice with a water / isopropanol (v / v, 1 / 7) mixed solution, disperse the obtained solid sample in 10 mL of ultrapure water, and store it in a refrigerator at 4 °C for later use.

[0059] 2) Preparation of magnetic-chiral nanoparticles:

[0060] Two mL of hexane solution containing achiral magnetic Fe3O4 nanoparticles (using achiral magnetic Fe3O4 nanoparticles with a particle size of 140 nm prepared in Example 1), 10 mL of aqueous solution containing superparamagnetic-chiral Co3O4 nanoparticles (particle size of 3-5 nm), and 2 mL of ethanol were added to a 50 mL centrifuge tube. The concentration ratio of achiral magnetic Fe3O4 nanoparticles to superparamagnetic-chiral Co3O4 nanoparticles was 10 mg / mL: 20 mg / mL. Tetramethylammonium hydroxide was added to adjust the pH of the solution to 12. The mixture was then vortexed for 0.5 h. Five volumes of isopropanol solution were added to the reaction solution to precipitate the nanoparticles. The mixture was centrifuged at 8000 rpm for 10 min, and the solid was collected. The sample was washed twice with a water / isopropanol (v / v, 1 / 5) mixture. The obtained solid was labeled Fe3O4@Co3O4-Pen. The sample was dispersed in 10 mL of ultrapure water and stored at 4 °C for later use.

[0061] Example 4

[0062] 1) Preparation of superparamagnetic-chiral Co3O4 nanoparticles:

[0063] Add 60 mL of ultrapure water, 8 mL of GSH (100 mM / L) aqueous solution, 8 mL of sodium citrate (100 mM / L) aqueous solution, and 4 mL of CoCl2 (200 mM / L) aqueous solution to a 250 mL three-necked flask. After mixing, add 10 mL of NaBH4 (100 mM / L) aqueous solution dropwise. After the NaBH4 aqueous solution is added, the mixed solution changes from an orange transparent solution to a brown solution. The reaction system is stirred at room temperature for 2 h. After the reaction is completed, a brown solution is obtained. Add 7 times the volume of isopropanol solution to the reaction solution to precipitate the synthesized superparamagnetic-chiral Co3O4 nanoparticles. Centrifuge at 10000 rpm for 20 min, collect the solid, wash the sample twice with a water / isopropanol (v / v, 1 / 7) mixed solution, disperse the obtained solid sample in 10 mL of ultrapure water, and store it in a refrigerator at 4 °C for later use.

[0064] 2) Preparation of magnetic-chiral nanoparticles:

[0065] Two mL of hexane solution containing achiral magnetic Fe3O4 nanoparticles (using achiral magnetic Fe3O4 nanoparticles with a particle size of 110 nm prepared in Example 1), 10 mL of aqueous solution containing superparamagnetic-chiral Co3O4 nanoparticles (particle size of 3-5 nm), and 2 mL of ethanol were added to a 50 mL centrifuge tube. The concentration ratio of achiral magnetic Fe3O4 nanoparticles to superparamagnetic-chiral Co3O4 nanoparticles was 5 mg / mL: 20 mg / mL. Tetramethylammonium hydroxide was added to adjust the pH of the solution to 12. The mixture was then vortexed for 0.5 h. Five volumes of isopropanol solution were added to the reaction solution to precipitate the nanoparticles. The mixture was centrifuged at 8000 rpm for 10 min, and the solid was collected. The sample was washed twice with a water / isopropanol (v / v, 1 / 5) mixture. The obtained solid was labeled Fe3O4@Co3O4-GSH. The sample was dispersed in 10 mL of ultrapure water and stored at 4 °C for later use.

[0066] Figure 1 The CD spectra of the magnetic-chiral nanoparticle solutions prepared in Examples 1-4 are shown below. Figure 1 As can be seen, after ligand exchange, chiral Co3O4 nanoparticles can effectively attach to the surface of magnetic nanoparticles and endow them with optical activity.

[0067] Figure 2 The images show the CD spectra of the magnetic-chiral nanoparticle solution gels prepared in Examples 1-4 after magnetization. Figure 2 As can be seen, after ligand exchange, chiral Co3O4 nanoparticles can effectively attach to the surface of magnetic nanoparticles; after being magnetized by an external magnetic field, the core of the magnetic nanoparticles can obtain a local magnetic field and can effectively regulate the optical activity of the Co3O4 nanoparticles wrapped around the core.

[0068] Comparative Example 1

[0069] Same as Example 1, except that in step 3), the concentration ratio of non-chiral magnetic Fe3O4 nanoparticles to superparamagnetic-chiral Co3O4 nanoparticles is 15 mg / mL: 4 mg / mL.

[0070] Comparative Example 2

[0071] Same as Example 1, except that in step 3), the concentration ratio of non-chiral magnetic Fe3O4 nanoparticles to superparamagnetic-chiral Co3O4 nanoparticles is 1 mg / mL: 30 mg / mL.

[0072] Comparative Example 3

[0073] Same as Example 1, except that in step 1), L-Cys is replaced with histidine.

[0074] Comparative Example 4

[0075] Preparation of magnetic-chiral nanoparticles: 2 mL of a hexane solution containing achiral magnetic Fe3O4 nanoparticles (using achiral magnetic Fe3O4 nanoparticles with a particle size of 110 nm prepared in Example 1), 10 mL of an aqueous solution containing superparamagnetic-chiral CoFe2O4 nanoparticles (particle size of 3-5 nm), and 2 mL of ethanol were added to a 50 mL centrifuge tube. The concentration ratio of achiral magnetic Fe3O4 nanoparticles to superparamagnetic-chiral Co3O4 nanoparticles was 5 mg / mL: 20 mg / mL. Tetramethylammonium hydroxide was added to adjust the pH of the solution to 12. The mixture was then vortexed for 1 h. Add 5 times the volume of isopropanol solution to the reaction solution to precipitate the nanoparticles, centrifuge at 8000 rpm for 10 min, collect the solid, wash the sample twice with a water / isopropanol (v / v, 1 / 5) mixed solution, and label the obtained solid as Fe3O4@CoFe2O4-Cys. Disperse the sample in 10 mL of ultrapure water and store it in a refrigerator at 4 °C for later use.

[0076] Figure 3 To obtain the CD spectra of the magnetic-chiral nanoparticle solutions prepared in Comparative Examples 1-4 and Example 1, from... Figure 3 As can be seen from the results, compared with Example 1, Comparative Example 1 had weaker optical activity due to the addition of too many Fe3O4 nanoparticles, and Comparative Example 2 had weaker optical activity due to the addition of too many Co3O4 nanoparticles. In Comparative Example 3, the optical activity of the nanoparticles was weakened because the ligands on the surface of the Co3O4 nanoparticles were changed to histidine. In Comparative Example 4, the optical activity of CoFe2O4-Cys was weakened compared to Co3O4-Cys because the nanoparticles that served as the chiral ligand layer were changed to CoFe2O4-Cys. This resulted in a weakening of the optical activity of the magnetic-chiral nanoparticles.

[0077] Figure 4 The CD spectra of the magnetic-chiral nanoparticle gels prepared in Comparative Examples 1-4 and Example 1 after magnetization were obtained from... Figure 4 As can be seen from the results, compared with Example 1, Comparative Example 1 had weaker optical activity due to the excessive amount of Co3O4 nanoparticles added. Comparative Example 2 also had excessive Co3O4 nanoparticles added, and the nanoparticles failed to retain a local magnetic field after magnetization, thus failing to regulate the optical activity of the chiral ligand layer. Comparative Example 3 had its optical activity weakened because the ligands on the surface of the Co3O4 nanoparticles were replaced with histidine. However, the nanoparticles could retain a local magnetic field after magnetization and regulate the optical activity of the chiral ligand layer. In Comparative Example 4, the nanoparticles were replaced with CoFe2O4-Cys. After ligand exchange, the nanoparticles could effectively attach to the surface of the magnetic nanoparticles. After magnetization with an external magnetic field, the core of the magnetic nanoparticles could obtain a local magnetic field and effectively regulate the optical activity of the CoFe2O4-Cys nanoparticles wrapped around its core.

[0078] Application examples

[0079] The magnetic-chiral nanoparticles prepared in Examples 1-4 and Comparative Examples 1-4 were used to prepare hydrogels incorporating the magnetic-chiral nanoparticles:

[0080] A prepared acrylamide solution (20 w%), tetramethylethylenediamine solution (1 w%), methylenebisacrylamide solution (1 w%), potassium persulfate solution (5 w%), and the magnetic-chiral nanoparticles (concentration of approximately 10 mg / mL) prepared in Examples 1-4 and Comparative Examples 1-4 were mixed in a volume ratio of (10:3:3:4:1). The mixed solution was poured into a cuvette and allowed to stand to form a gel. The cuvette was then placed in a uniform parallel external magnetic field. The external magnetic field caused the permanent magnetic moments of the magnetic cores of the magnetic-chiral nanoparticles prepared in Examples 1-4 to align. By adjusting the strength of the external magnetic field, the strength of the local magnetic field of the magnetic nanocores (non-chiral Fe3O4 nanoparticles) could be controlled, thereby regulating the optical activity of the outer superparamagnetic-chiral Co3O4 nanoparticles. In Comparative Example 1, the addition of too many achiral magnetic Fe3O4 nanoparticles resulted in insufficient ligand exchange. In Comparative Example 2, the addition of insufficient achiral magnetic Fe3O4 nanoparticles resulted in weaker magnetic properties of the nanoparticles. In Comparative Example 3, the use of histidine acid reduced its binding ability with the magnetic nanoparticles, leading to a decrease in the optical activity of the obtained nanoparticles. In Comparative Example 4, the use of superparamagnetic-chiral CoFe2O4-Cys nanoparticles resulted in magnetically responsive magnetic-chiral nanoparticles after ligand exchange, although their optical activity was weaker compared to Co3O4-Cys. The optical activity of the magnetic-chiral nanoparticles using this as a ligand was weakened.

[0081] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. The application of magnetic-chiral nanoparticles with locally modulated optical activity in the preparation of hydrogels, characterized in that, The magnetic-chiral nanoparticles with locally modulated optical activity use non-chiral Fe3O4 nanoparticles as the magnetic core and superparamagnetic-chiral Co3O4 nanoparticles as the chiral ligand layer. The preparation method of the magnetic-chiral nanoparticles with locally modulated optical activity includes the following steps: mixing an organic solution containing non-chiral Fe3O4 nanoparticles and an aqueous solution containing superparamagnetic-chiral Co3O4 nanoparticles, adjusting the pH of the mixed solution to alkaline, vortexing, settling, centrifuging, and washing to obtain the magnetic-chiral nanoparticles. The concentration ratio of non-chiral magnetic Fe3O4 nanoparticles to superparamagnetic-chiral Co3O4 nanoparticles in the mixed solution is (1-10):(4-20). The non-chiral magnetic Fe3O4 nanoparticles have a particle size of 70-140 nm. The superparamagnetic-chiral Co3O4 nanoparticles have a particle size of 3-5 nm; The preparation method of the superparamagnetic-chiral Co3O4 nanoparticles is as follows: using CoCl2, sodium citrate and sodium borohydride as raw materials, adding chiral ligands, stirring the reaction at room temperature, and synthesizing superparamagnetic-chiral Co3O4 nanoparticles. The chiral ligands include one or more of cystine, penicillamine, and glutathione.

2. The application according to claim 1, characterized in that, The pH is 8-12.

3. The application according to claim 1, characterized in that, The preparation method of the non-chiral magnetic Fe3O4 nanoparticles is as follows: FeCl3·6H2O and sodium oleate are used as raw materials to prepare an iron oleate complex, the iron oleate complex is added to octadecene, and the mixture is heated and stirred to obtain non-chiral magnetic Fe3O4 nanoparticles.

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