A magnetic sensitive beta-CD-OTf@Au@R-Fe3O4 nanomotor and a preparation method and application thereof

Abstract

The application discloses a kind of magnetically sensitive β-CD-OTf@Au@R-Fe3O4 Nanomotor and its preparation method and application, including the following steps: respectively preparing Zn (OTf) 2 solution and supersaturated β-CD solution, based on host-guest interaction, after mixing, β-CD-OTf is obtained;R-Fe3O4 is in situ assembled on Au NPs by electrostatic force, and R-Fe3O4@Au is obtained;Au@R-Fe3O4 is coupled to β-CD-OTf by electrostatic force, and magnetically sensitive β-CD-OTf@Au@R-Fe3O4 Nanomotor is obtained.The preparation method is simple, and the obtained nanomotor can not only significantly improve selective adsorption capacity to cationic dye, but also has high SERS activity, can realize self-cleaning after SERS detection, has excellent self-cleaning performance and recycling performance, and is suitable for being applied in cyclic selective capture and high-sensitivity SERS detection of cationic dye.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology, specifically to a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor, its preparation method, and its application. Background Technology

[0002] Uncontrolled discharge of organic pollutants into industrial wastewater leads to widespread water pollution, endangering human health. Among these, cationic dyes, due to their complex structure and high ecotoxicity, are a particularly concerning pollutant. However, the trace concentrations of cationic dyes and the complexity of detection methods pose significant challenges. Therefore, there is an urgent need to develop effective detection methods and wastewater treatment technologies. Surface-enhanced Raman scattering (SERS) can provide molecular fingerprint information unaffected by the aquatic environment and is gaining increasing attention due to its practicality, ease of operation, and cost-effectiveness. However, for effective detection, the target molecule must be close to the substrate surface. When the target molecule concentration is too low, the substrate lacks the controllability required for targeted adsorption, significantly reducing the probability of collision between the target molecule and the substrate. Therefore, developing SERS substrates with high capture rates and high selectivity is crucial for mitigating the adverse environmental and human health impacts of cationic dye residues. Micro / nanomotors can convert external energy (such as light, magnetic fields, and ultrasound) into mechanical energy, enabling rapid movement in solution. This property greatly enhances solute diffusion and transport, making it promising for applications in drug delivery and environmental remediation. Magnetic-driven micro / nanomotors, especially those utilizing magnetic Fe3O4 nanoparticles, have attracted considerable attention due to their direct driving mechanism, precise remote control, cost-effectiveness, high separability, and biocompatibility. However, while these motors can be separated from solution under the influence of an external magnetic field, they often lack self-cleaning capabilities, posing challenges to recycling and potentially causing secondary pollution. Furthermore, they typically lack active selective transport capabilities, limiting their ability to capture and transport pollutants. Moreover, the SERS activity of micro / nanomotors is often insufficient, primarily due to the lack of charge transfer effects and abundant hotspots with high electromagnetic enhancement. Therefore, there is an urgent need to develop circulating micro / nanomotors with high activity, highly selective capture capabilities, and multiple hotspot regions to improve the efficiency of water pollution treatment. Summary of the Invention

[0003] The purpose of this invention is to provide a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor, its preparation method, and its application. The preparation method is simple, and the prepared nanomotor can not only significantly improve the adsorption capacity but also has high SERS activity. It can achieve self-cleaning after SERS detection, exhibiting excellent self-cleaning and recyclability performance. It is suitable for application in the selective capture and highly sensitive SERS detection of cationic dyes.

[0004] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0005] A method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor includes the following steps:

[0006] S1. Preparation of β-CD-OTf based on the Hofmeister effect: Zn(OTf)2 solution and supersaturated β-CD solution were prepared separately. Based on the host-guest interaction, β-CD-OTf can be obtained by mixing them.

[0007] S2. R-Fe3O4 was dispersed in anhydrous ethanol, sonicated, and then APTES was added as an amino coupling agent. The reaction was carried out while sonicating and stirring. The product was then washed after magnetic separation to obtain amino-functionalized R-Fe3O4, which was then dispersed in deionized water for later use.

[0008] S3. Add gold nanoparticles Au NPs to amino-functionalized R-Fe3O4 dispersed in deionized water, stir, centrifuge and wash to obtain Au@R-Fe3O4, and disperse it in deionized water for later use.

[0009] S4. Au@R-Fe3O4 is coupled to β-CD-OTf via electrostatic interaction to obtain a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor.

[0010] Further, the specific steps of step S1 are as follows: prepare a Zn(OTf)2 solution with water as solvent and sonicate it to completely dissolve it; prepare a supersaturated β-CD solution with a white precipitate at the bottom; add the Zn(OTf)2 solution dropwise to the supersaturated β-CD solution until the white precipitate at the bottom completely disappears, thus obtaining the β-CD-OTf solution.

[0011] Preferably, the concentration of the Zn(OTf)2 solution is 2 mol / L, and the concentration of the supersaturated β-CD solution is 30 mol / mL.

[0012] Preferably, in step S2, the amount of R-Fe3O4 added is 0.1-0.6 mg / mL of anhydrous ethanol; the volume-to-mass ratio of APTES to R-Fe3O4 is (0.5-1) mL: 3 mg; the ultrasonic treatment is carried out for 25-35 min, followed by mechanical stirring at 300-400 rpm for 5-7 h.

[0013] Furthermore, in step S2, the preparation method of R-Fe3O4 is as follows:

[0014] FeCl3, NaH2PO4 and anhydrous Na2SO4 were dissolved in deionized water. The resulting mixture was transferred to a stainless steel autoclave lined with Teflon and reacted at 200-250°C for 45-50 h. After the reaction was completed, the mixture was cooled and allowed to stand overnight. The precipitate obtained after centrifugation was washed several times with distilled water and anhydrous ethanol and finally dried at 70-90°C to obtain R-Fe2O3.

[0015] Dry R-Fe2O3 powder was placed in a tube furnace with a constant gas flow rate. The gas was a mixture of hydrogen and argon with a volume ratio of 1:9. The tube furnace was evacuated and then annealed at 400-500℃ for 8-12 hours. After the tube furnace was cooled to room temperature, R-Fe3O4 was obtained.

[0016] Furthermore, in step S3, the preparation method of the gold nanoparticles Au NPs is as follows: chloroauric acid is added to a container and heated to boiling while constantly stirring; sodium citrate is then quickly added, and the color gradually changes from clear to dark; the solution is then boiled until it turns wine red; after the reaction is completed, it is naturally cooled to room temperature to obtain spherical gold nanoparticles Au NPs.

[0017] Further, in step S4, the β-CD-OTf solution prepared in step S1 is added to the Au@R-Fe3O4 dispersed in deionized water prepared in step S3, with a volume ratio of β-CD-OTf solution to Au@R-Fe3O4 of 5:1; the mixture is sonicated and stirred for 2-4 min, and then Au@R-Fe3O4 is electrostatically coupled to β-CD-OTf. The magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor is collected using an external magnet, and then washed multiple times with ultrapure water to remove unbound Au@R-Fe3O4.

[0018] The present invention also provides a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor prepared by the above preparation method.

[0019] This invention also provides the application of the magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor prepared by the above preparation method in the selective capture and highly sensitive SERS detection of cationic dyes.

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

[0021] The present invention provides a method for preparing Au@R-Fe3O4 nanomotors by electrostatic coupling to β-CD-OTf, resulting in a reusable magnetic motor for the efficient and selective capture and precise detection of cationic dyes. The preparation method of the magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor (hereinafter referred to as "βAR nanomotor") is simple. The prepared βAR nanomotor, based on the synergistic effect of electrostatic attraction and hydrogen bonding, can significantly improve adsorption capacity, enabling it to selectively remove cationic dyes. The gold nanoparticles on the βAR nanomotor are uniformly fixed to the surface of the high-specific-surface-area cyclic magnetic R-Fe3O4 particles via a coupling agent, effectively amplifying the Raman signal of the target molecule and exhibiting high detection sensitivity. Furthermore, the βAR nanomotor prepared by the present invention possesses excellent self-cleaning and recyclability properties, making it suitable for application in the recyclable selective capture and highly sensitive SERS detection of cationic dyes. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the fabrication of a magnetically sensitive βAR nanomotor according to an embodiment of the present invention;

[0023] Figure 2 SEM image (a) and TEM image (b) of the magnetically sensitive βAR nanomotor prepared in the embodiments of the present invention;

[0024] Figure 3 The image shows the UV-Vis spectra of the βAR nanomotor before and after adsorption of the MG and EY mixed solution in an embodiment of the present invention.

[0025] Figure 4 This is a schematic diagram showing the SERS performance results of the βAR nanomotor in this embodiment of the invention, wherein (a) SERS spectra of different concentrations of RhB adsorbed on the βAR nanomotor; (b) 1362 cm⁻¹ -1 A graph showing the relationship between the logarithmic SERS intensity and the logarithmic RhB concentration.

[0026] Figure 5 The self-cleaning performance diagram of the βAR nanomotor in this embodiment of the invention; after SERS detection, the adsorbed 10 nanoparticles were washed with ethanol solution. -6 SERS spectrum of M RhB-βAR nanomotor;

[0027] Figure 6 In the embodiments of the present invention, 10 βAR nanomotors adsorbed -6 The SERS spectrum of M RhB after 7 cycles of processing. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] In the following examples, unless otherwise stated, all reagents used are commercially available or obtained in accordance with known literature.

[0030] The abbreviations used in this invention represent the following substance names:

[0031] Zn(OTf)2: Zinc trifluoromethanesulfonate;

[0032] β-CD: β-cyclodextrin;

[0033] APTES: 3-Aminopropyltriethoxysilane;

[0034] RhB: Rhodamine B.

[0035] Example

[0036] like Figure 1 As shown, a method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor includes the following steps:

[0037] S1. Preparation of β-CD-OTf based on the Hofmeister effect: Prepare Zn(OTf)2 solution and supersaturated β-CD solution respectively. Based on the host-guest interaction, β-CD-OTf can be obtained by mixing them. The specific steps are as follows:

[0038] Prepare a 2 mol / L Zn(OTf)2 solution using water as the solvent and sonicate it for 5 min to dissolve it completely; prepare a 30 mol / mL supersaturated β-CD solution, at which point a white precipitate appears at the bottom of the supersaturated β-CD solution; add the prepared Zn(OTf)2 solution dropwise to the supersaturated β-CD solution until the white precipitate at the bottom completely disappears, and the β-CD-OTf solution is obtained.

[0039] S2. 6 mg of R-Fe3O4 was dispersed in 10 mL of anhydrous ethanol and sonicated for 10 min to form a uniform dispersion. Then, 2 mL of LAPTES was added as an amino coupling agent to functionalize the R-Fe3O4 with amino groups. The mixture was sonicated for another 30 min and then mechanically stirred at 350 rpm for 6 h to promote the connection of amino functional groups on the surface of R-Fe3O4. The amino-functionalized R-Fe3O4 nanoparticles were then collected using an external magnet and dispersed in 5 mL of deionized water.

[0040] The preparation method of R-Fe3O4 is as follows:

[0041] 0.8110 g of anhydrous ferric chloride (FeCl3), 0.0052 g of ammonium dihydrogen phosphate (NH4H2PO4), and 0.0195 g of anhydrous sodium sulfate (Na2SO4) were dissolved in deionized water and then transferred to a 250 mL volumetric flask for dilution to volume. The mixed solution was then dispersed and transferred to a 100 mL Teflon-lined stainless steel autoclave and reacted at 220 °C for 48 h. After the reaction was completed, the mixture was cooled and allowed to stand overnight. The precipitate obtained after centrifugation was washed twice with distilled water and anhydrous ethanol, respectively, and finally dried at 80 °C for 6 h to obtain R-Fe2O3.

[0042] Dry R-Fe2O3 powder was placed in a tube furnace with a constant hydrogen / argon flow rate (hydrogen accounted for 10% of the total volume of the mixed gas), the tube furnace was evacuated, and then annealed at 450℃ for 10h. After the tube furnace was cooled to room temperature, iron oxide nanorings (R-Fe3O4) were obtained.

[0043] S3. Add 10 mL of gold nanoparticles AuNPs (16 nm) to 1 mL of amino-functionalized R-Fe3O4 dispersed in deionized water, stir mechanically for 3 h, centrifuge and wash to obtain Au@R-Fe3O4, and disperse it in deionized water for later use.

[0044] The preparation method of the gold nanoparticles Au NPs is as follows: 200 mL of ultrapure water and 2.42 mL of 1% chloroauric acid solution are mixed and added to a 250 mL round-bottom flask, and heated to boiling using a reflux condenser. After boiling, 3 mL of 1% sodium citrate solution is added, and the color gradually changes from clear to dark. The solution is boiled for 20 min until it turns wine red. Heating is stopped, and stirring is continued until room temperature, and 16 nm spherical gold nanoparticles Au NPs are obtained.

[0045] S4. Au@R-Fe3O4 is coupled to β-CD-OTf via electrostatic interaction to obtain a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor (βAR nanomotor). The specific steps are as follows:

[0046] 5 mL of β-CD-OTf (2 mg / mL) was added to 1 mL of Au@R-Fe3O4. The mixture was sonicated for 10 min and mechanically stirred at 350 rpm for 3 min. Au@R-Fe3O4 was then electrostatically coupled to β-CD-OTf. The magnetically sensitive βAR nanomotor was collected using an external magnet, washed with ultrapure water, and dispersed in 5 mL of ultrapure water. SEM and TEM images of the prepared βAR nanomotor are shown below. Figure 2 As shown, from Figure 2 As can be seen, the cyclic structure of β-CD-OTf was not destroyed after being composited with Au@R-Fe3O4.

[0047] The βAR nanomotor prepared in this embodiment was subjected to adsorption performance, SERS performance, self-cleaning performance, and recycling performance tests. The test procedures and results are as follows:

[0048] (1) Determination of the adsorption performance of βAR nanomotors

[0049] 0.5 mL of βAR nanomotors were added to different dye solutions, and static adsorption equilibrium was reached after shaking at 350 rpm for 3 minutes. Subsequently, the βAR nanomotors dynamically captured free pollutants under the drive of an external magnetic field. The βAR nanomotors loaded with pollutants were recovered, and the maximum absorbance of various pollutants in the supernatant was measured using a UV-Vis spectrophotometer. Figure 3 The UV-Vis spectra of the βAR nanomotors before and after adsorption of a mixed solution of cationic dye MG and anionic dye EY are shown. The characteristic absorption peak of MG almost disappears, indicating that the cationic dye MG is selectively adsorbed by the βAR nanomotors. Furthermore, modification of the β-CD cavity with OTf- (trifluoromethanesulfonate anion) enables it to overcome non-selective host-guest interactions and promotes selective adsorption of cationic dyes. The surface of the βAR nanomotors is rich in highly polar and hydrophilic hydroxyl groups, and the potential hydrogen bonding interactions between these groups and the oxygen-containing functional groups in organic pollutants significantly enhance the adsorption capacity.

[0050] (2) SERS performance determination of βAR nanomotors

[0051] Following the adsorption test, SERS analysis was performed on the βAR nanomotors: 10 μL of the βAR nanomotor nanocomposite was immersed in a series of RhB solutions of different concentrations (I, 1.6 × 10⁻⁶). -4 M; II, 3.13×10 -6 M; Ⅲ, 1.25×10 -6 M; Ⅳ, 2.5×10 -7 M; V, 5×10 -8 Adsorption saturation was achieved in 10 μL (M) for 3 min. The βAR nanomotors were then driven by an external magnet to extensively contact the free RhB molecules, and the βAR nanomotors were magnetically separated for SERS detection. The SERS experiment was performed using a BWS415-785S portable Raman instrument with an excitation wavelength of 785 nm, an integration time of 20 s, and an excitation power of 30%. Results are as follows: Figure 4 As shown. From Figure 4 The results show a linear correlation between the decrease in RhB concentration and the decrease in SERS spectral intensity, spanning a concentration range of five orders of magnitude, with a detection limit (LOD) of 1.47 × 10⁻⁶. -12M indicates that the βAR nanomotor has high detection sensitivity.

[0052] (3) Determination of the self-cleaning performance of βAR nanomotors

[0053] After capturing RhB and performing SERS analysis, the βAR nanomotor was added to 10 μL of ethanol. The βAR nanomotor was then separated from the supernatant using an external magnet, and subsequently immersed in ultrapure water to remove residual ions. Finally, the βAR nanomotor was magnetically recovered and vacuum-dried at room temperature for self-cleaning. The measurement results are as follows: Figure 5 As shown, the SERS signal of RhB almost disappeared, indicating that the βAR nanomotor has good self-cleaning properties.

[0054] (4) Cyclic performance determination of βAR nanomotors

[0055] After SERS characterization, 10 μL of ethanol was added to the βAR nanomotor that captured the contaminants to extract them. SERS measurements showed that the adsorbed molecules were completely desorbed, yielding a clean βAR nanomotor. Subsequently, repeated cyclic SERS measurements were performed on the βAR nanocomposite material under the same experimental conditions as the initial test. Each measurement and self-cleaning process was repeated 7 times, and the results are as follows: Figure 6 As shown. From Figure 6 As can be seen, even after seven “capture-detection-self-cleaning” cycles, although its SERS performance slightly decreases due to the disappearance of some “hot spots”, the βAR nanomotor can still be reused, indicating that the βAR nanomotor has good recyclability.

[0056] In summary, this invention has prepared a magnetic motor capable of selectively capturing and highly sensitively detecting cationic dyes. The βAR nanomotor prepared by this invention, based on the synergistic effect of electrostatic attraction and hydrogen bonding, can significantly improve adsorption capacity, enabling it to selectively remove cationic dyes. The gold nanoparticles on this βAR nanomotor are uniformly immobilized on the surface of cyclic magnetic R-Fe3O4 particles with a high specific surface area through a coupling agent, effectively amplifying the Raman signal of the target molecule and exhibiting high detection sensitivity. Furthermore, the βAR nanomotor prepared by this invention possesses excellent self-cleaning and recyclability properties, making it suitable for application in the recyclable selective capture and highly sensitive SERS detection of cationic dyes.

[0057] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any simple changes or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor, characterized in that, Includes the following steps: S1. Preparation of β-CD-OTf based on the Hofmeister effect: Prepare zinc trifluoromethanesulfonate Zn(OTf)2 solution and supersaturated β-cyclodextrin β-CD solution respectively. Based on the host-guest interaction, β-CD-OTf can be obtained by mixing them. S2. The cyclic magnetic R-Fe3O4 was dispersed in anhydrous ethanol, and after sonication, 3-aminopropyltriethoxysilane APTES was added as an amino coupling agent. The reaction was carried out while sonicating and stirring. After the product was magnetically separated and washed, the amino-functionalized R-Fe3O4 was obtained and dispersed in deionized water for later use. S3. Add gold nanoparticles Au NPs to amino-functionalized R-Fe3O4 dispersed in deionized water, stir, centrifuge and wash to obtain Au@R-Fe3O4, and disperse it in deionized water for later use. S4. Au@R-Fe3O4 is coupled to β-CD-OTf via electrostatic interaction to obtain a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor.

2. The method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor according to claim 1, characterized in that, The specific steps of step S1 are as follows: prepare a Zn(OTf)2 solution with water as solvent and sonicate it to completely dissolve it; prepare a supersaturated β-CD solution with a white precipitate at the bottom; add the Zn(OTf)2 solution dropwise to the supersaturated β-CD solution until the white precipitate at the bottom completely disappears, and the β-CD-OTf solution is obtained.

3. The method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor according to claim 1 or 2, characterized in that, In step S2, the amount of R-Fe3O4 added is 0.1~0.6 mg / mL of anhydrous ethanol; the volume-to-mass ratio of APTES to R-Fe3O4 is (0.5~1) mL:3 mg; ultrasonic treatment is performed for 25~35 min, followed by mechanical stirring at 300~400 rpm for 5~7 h.

4. The method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor according to claim 1 or 2, characterized in that, In step S2, the preparation method of R-Fe3O4 is as follows: FeCl3, NaH2PO4 and anhydrous Na2SO4 were dissolved in deionized water. The resulting mixture was transferred to a stainless steel autoclave lined with Teflon and reacted at 200-250 °C for 45-50 h. After the reaction was completed, the mixture was cooled and allowed to stand overnight. The precipitate obtained after centrifugation was washed several times with distilled water and anhydrous ethanol and finally dried at 70-90 °C to obtain R-Fe2O3. Dry R-Fe2O3 powder was placed in a tube furnace with a constant gas flow rate. The gas was a mixture of hydrogen and argon with a volume ratio of 1:

9. The tube furnace was evacuated and then annealed at 400~500 ℃ for 8~12 h. After the tube furnace was cooled to room temperature, R-Fe3O4 was obtained.

5. The method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor according to claim 1 or 2, characterized in that, In step S3, the preparation method of the gold nanoparticles Au NPs is as follows: chloroauric acid is added to a container and heated to boiling while stirring continuously; sodium citrate is then quickly added, and the color gradually changes from clear to dark; the solution is then boiled until it turns wine red; after the reaction is completed, it is naturally cooled to room temperature to obtain spherical gold nanoparticles Au NPs.

6. The method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor according to claim 1 or 2, characterized in that, In step S4, the β-CD-OTf solution prepared in step S1 is added to the Au@R-Fe3O4 dispersed in deionized water prepared in step S3. The volume ratio between the β-CD-OTf solution and Au@R-Fe3O4 is 5:

1. The mixture is sonicated and stirred for 2-4 min. Then, Au@R-Fe3O4 is electrostatically coupled to β-CD-OTf. The magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor is collected using an external magnet and washed multiple times with ultrapure water to remove unbound Au@R-Fe3O4.

7. A magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor prepared by the preparation method of any one of claims 1 to 6.

8. The application of the magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor prepared according to claim 7 in the selective capture and highly sensitive surface-enhanced Raman scattering (SERS) detection of cationic dyes.

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