Magnetic-sensitive beta-CD-OTf (at) Au (at) R-Fe3O4 nano motor and preparation method and application thereof

Abstract

The invention discloses a magnetic-sensitive beta-CD-OTf (at) Au (at) R-Fe3O4 nano motor and a preparation method and application thereof, and the preparation method comprises the following steps: respectively preparing a Zn (OTf) 2 solution and a supersaturated beta-CD solution, and based on the host-guest interaction, mixing to obtain beta-CD-OTf; the method comprises the following steps: assembling R-Fe3O4 on Au NPs in situ through static electricity to obtain R-Fe3O4 (at) Au; and the Au (at) R-Fe3O4 is coupled to the beta-CD-OTf through the electrostatic interaction, so that the magnetic sensitive beta-CD-OTf (at) Au (at) R-Fe3O4 nano motor is obtained. The preparation method is simple, and the obtained nano motor not only can significantly improve the selective adsorption capacity of cationic dyes, 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 to cyclic selective capture and high-sensitivity SERS detection of cationic dyes.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and particularly relates to a magnetic β-CD-OTf@Au@R-Fe3O4 nanomotor and a preparation method and application thereof. Background Art

[0002] The uncontrolled discharge of organic pollutants in industrial wastewater can lead to large-scale water pollution, which in turn endangers human health. Among them, cationic dyes have become one of the worrying pollutants due to their complex structure and high ecological toxicity. However, the trace concentration of cationic dyes and the complexity of detection methods pose great challenges to detection. 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 that is not interfered by the water environment, and has attracted increasing attention due to its strong practicability, simple operation, economic feasibility and other advantages. However, for effective detection, the target molecules must be close to the substrate surface. When the concentration of the target molecules is too low, the substrate lacks the controllability required for targeted adsorption, greatly reducing the collision probability between the target molecules and the substrate. Therefore, developing SERS substrates with high capture rates and high selectivity is crucial for reducing the adverse effects of cationic dye residues on the environment and human health. Micro / nanomotors can convert external energy (such as light, magnetic field, ultrasonic wave, etc.) into mechanical energy and move rapidly in solution. This property greatly enhances the diffusion and transport of solutes, making it have broad application prospects in fields such as drug delivery and environmental remediation. Magnetically driven micro / nanomotors, especially those using magnetic Fe3O4 nanoparticles, have attracted much attention due to their direct driving mechanism, precise remote control, cost-effectiveness, high-efficiency separability and biocompatibility. However, although these motors can be separated from the solution under the action of an external magnetic field, they often lack self-cleaning ability, posing challenges for recycling and possibly causing secondary pollution. In addition, they usually do not have an active selective transport function, limiting their ability to capture and transport pollutants. Moreover, the SERS activity of micro / nanomotors is often insufficient, mainly due to the lack of charge transfer effects and the lack of abundant hot spots with high electromagnetic enhancement. Therefore, there is an urgent need to develop recyclable micro / nanomotors with activity, high selective capture ability and multiple hot spot regions to improve the efficacy of water pollution treatment. Summary of the Invention

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

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

[0005] A preparation method of a magnetic-sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor, comprising the following steps:

[0006] S1. Prepare 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 after mixing.

[0007] S2. Disperse R-Fe3O4 in absolute ethanol, add APTES as an amino coupling agent after ultrasonic treatment, stir the reaction while ultrasonicating, and after magnetic separation and washing of the product, amino-functionalized R-Fe3O4 is obtained and dispersed in deionized water for standby.

[0008] S3. Add gold nanoparticles Au NPs to the amino-functionalized R-Fe3O4 dispersed in deionized water, stir and then centrifuge and wash to obtain Au@R-Fe3O4, which is dispersed in deionized water for standby.

[0009] S4. Couple Au@R-Fe3O4 to β-CD-OTf through electrostatic interaction to obtain a magnetic-sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor.

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

[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 addition amount of R-Fe3O4 is 0.1 - 0.6 mg / mL of absolute ethanol; the volume-mass ratio of APTES to R-Fe3O4 is (0.5 - 1) mL: 3 mg; ultrasonically treat for 25 - 35 min, and then mechanically stir at a rotation speed of 300 - 400 rpm for 5 - 7 h.

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

[0014] Dissolve FeCl3, NaH2PO4 and anhydrous Na2SO4 in deionized water. Transfer the resulting mixture to a stainless-steel autoclave lined with Teflon and react at 200 - 250 °C for 45 - 50 h. After the reaction is completed, cool and let stand overnight. The precipitate obtained after centrifugation is washed repeatedly with distilled water and anhydrous ethanol, and finally dried at 70 - 90 °C to obtain R-Fe2O3;

[0015] Place the dried R-Fe2O3 powder in a tubular furnace with a constant gas flow rate. The gas is a mixture of hydrogen and argon with a volume ratio of 1:9. Evacuate the tubular furnace, and then anneal at 400 - 500 °C for 8 - 12 h. After the tubular furnace cools to room temperature, R-Fe3O4 is obtained.

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

[0017] Furthermore, in step S4, add the β-CD-OTf solution prepared in step S1 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; Ultrasonic the mixture and then stir for 2 - 4 min, and then couple Au@R-Fe3O4 to β-CD-OTf by electrostatic interaction. Use an external magnet to collect the magnetosensitive β-CD-OTf@Au@R-Fe3O4 nanomotor, and wash it repeatedly with ultrapure water to remove the unbound Au@R-Fe3O4.

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

[0019] The present invention also provides the application of the magnetosensitive β-CD-OTf@Au@R-Fe3O4 nanomotor prepared by the above preparation method in selectively capturing 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 preparation method of the present invention is that Au@R-Fe3O4 is coupled to β-CD-OTf through electrostatic interaction to prepare a reusable magnetic motor for efficient selective capture and precise detection of cationic dyes. The preparation method of the magnetic-sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor (hereinafter referred to as "βAR nanomotor") of the present invention is simple. The prepared βAR nanomotor can significantly improve the adsorption capacity based on the synergistic effect of electrostatic attraction and hydrogen bonds, enabling the βAR nanomotor to highly selectively remove cationic dyes. The gold nanoparticles on the βAR nanomotor of the present invention are uniformly fixed on the surface of the 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 having high detection sensitivity. In addition, the prepared βAR nanomotor of the present invention has excellent self-cleaning performance and recyclability, and is suitable for application in the recyclable selective capture and highly sensitive SERS detection of cationic dyes. Brief Description of the Drawings

[0022] Figure 1 It is a flowchart for preparing the magnetic-sensitive βAR nanomotor in the embodiment of the present invention;

[0023] Figure 2 It is the SEM image (a) and TEM image (b) of the magnetic-sensitive βAR nanomotor prepared in the embodiment of the present invention;

[0024] Figure 3 It is the ultraviolet-visible spectrogram of the βAR nanomotor before and after adsorbing the mixed solution of MG and EY in the embodiment of the present invention;

[0025] Figure 4 It is a schematic diagram related to the SERS performance results of the βAR nanomotor in the embodiment of the present invention. Among them, (a) SERS spectra of different concentrations of RhB adsorbed on the βAR nanomotor; (b) Relationship diagram of the logarithm of SERS intensity at 1362 cm -1 and the logarithm of RhB concentration;

[0026] Figure 5 Self-cleaning performance diagram of the βAR nanomotor in the embodiment of the present invention; After SERS detection, the SERS spectrogram of the 10 -6 M RhB-βAR nanomotor adsorbed was washed with an ethanol solution;

[0027] Figure 6 It is for the 10 -6 M RhB adsorbed by the βAR nanomotor in the embodiment of the present invention after 7 cycles of treatment. Detailed Embodiments

[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 specified, the reagents used can be purchased commercially or obtained in the manner reported in known literature.

[0030] The names of the substances represented by the English abbreviations used in the present invention are as follows:

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

[0032] β-CD: β-cyclodextrin;

[0033] APTES: 3-aminopropyltriethoxysilane;

[0034] RhB: Rhodamine B.

[0035] Example

[0036] As Figure 1 shown, a preparation method of a magnetic-sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor includes the following steps:

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

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

[0039] S2. Disperse 6 mg of R-Fe3O4 in 10 mL of absolute ethanol, and ultrasonicate it for 10 min to form a homogeneous dispersion; then, add 2 mL of APTES as an amino coupling agent to functionalize the amino group of R-Fe3O4; ultrasonicate the mixed dispersion for another 30 min, and then mechanically stir it at a speed of 350 rpm for 6 h to promote the connection of the amino functional groups on the surface of R-Fe3O4; then collect the amino-functionalized R-Fe3O4 nanoparticles with an external magnet and disperse them in 5 mL of deionized water.

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

[0041] Dissolve 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) in deionized water, and then transfer it to a 250 mL volumetric flask for volume fixation; Disperse and transfer the mixed solution to a 100 mL stainless steel autoclave lined with Teflon, react at 220 °C for 48 h, cool and let it stand overnight after the reaction, wash the obtained precipitate with distilled water and anhydrous ethanol twice respectively, and finally dry it at 80 °C for 6 h to obtain R-Fe2O3;

[0042] Place the dried R-Fe2O3 powder in a tubular furnace with a constant hydrogen / argon flow rate (hydrogen accounts for 10% of the total volume of the mixed gas), evacuate the tubular furnace, and then anneal it at 450 °C for 10 h. After the tubular furnace cools to room temperature, obtain iron oxide nanorings (R-Fe3O4);

[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, then centrifuge and wash to obtain Au@R-Fe3O4, and disperse it in deionized water for standby;

[0044] The preparation method of the gold nanoparticles Au NPs is as follows: Mix 200 mL of ultrapure water and 2.42 mL of 1% chloroauric acid solution and add them to a 250 mL round-bottom flask, and at the same time use a condensing reflux device to heat to boiling: After boiling, add 3 mL of 1% sodium citrate solution, and its color gradually changes from clear to dark; Boil the solution for 20 min until it turns wine red; Stop heating and continue to stir until room temperature, then 16 nm spherical gold nanoparticles Au NPs can be obtained.

[0045] S4. Couple Au@R-Fe3O4 to β-CD-OTf through electrostatic interaction to obtain a magnetic β-CD-OTf@Au@R-Fe3O4 nanomotor (βAR nanomotor). The specific steps are as follows:

[0046] Add 5 mL of β-CD-OTf with a concentration of 2 mg / mL to 1 mL of Au@R-Fe3O4, ultrasonicate the mixture for 10 min, and stir mechanically at a speed of 350 rpm for 3 min, then couple Au@R-Fe3O4 to β-CD-OTf through electrostatic interaction, collect the magnetic βAR nanomotor with an external magnet, wash it with ultrapure water, and disperse it in 5 mL of ultrapure water. The SEM and TEM of the prepared βAR nanomotor are as Figure 2 shown. It can be seen from Figure 2 that the cyclic structure of Au@R-Fe3O4 is not damaged after the combination of β-CD-OTf.

[0047] The adsorption performance, SERS performance, self-cleaning performance, and recycling performance of the βAR nanomotors prepared in this example were measured respectively, and the test processes and results are as follows:

[0048] (1) Adsorption performance measurement of βAR nanomotors

[0049] Add βAR nanomotors (0.5 mL) to different dye solutions and oscillate for 3 minutes at a rotation speed of 350 rpm to reach static adsorption equilibrium. Subsequently, under the drive of an external magnetic field, the βAR nanomotors dynamically capture free pollutants. The βAR nanomotors loaded with pollutants are recovered, and the maximum absorbance of various pollutants in the supernatant is measured using a UV-visible spectrophotometer. Figure 3 Figure 10 shows the UV-visible spectra of the βAR nanomotors before and after adsorbing the mixed solution of cationic dye MG and anionic dye EY. The characteristic absorption peak of MG almost disappears, indicating that the cationic dye MG is selectively adsorbed by the βAR nanomotors. In addition, after modifying the β-CD cavity with OTf- (trifluoromethanesulfonate anion), it can overcome the non-selective host-guest interaction adsorption and promote the selective adsorption of cationic dyes. The surface of the βAR nanomotors is rich in highly polar and hydrophilic hydroxyl groups, and the potential hydrogen bond interaction between these groups and the oxygen-containing functional groups in organic pollutants significantly improves the adsorption capacity.

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

[0051] After the adsorption test, SERS detection was carried out on the βAR nanomotors: Immerse the βAR nanomotor (10 μL) nanocomposite in a series of RhB solutions with different concentrations (Ⅰ, 1.6×10 -4 M; Ⅱ, 3.13×10 -6 M; Ⅲ, 1.25×10 -6 M; Ⅳ, 2.5×10 -7 M; Ⅴ, 5×10 -8 M) (10 μL) for 3 min to reach adsorption saturation; Use an external magnet to drive the βAR nanomotors to widely contact free RhB molecules, and magnetically separate the βAR nanomotors for SERS detection. The SERS experiment used 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%. The results are as Figure 4 shown. It can be seen from Figure 4 that the decrease in RhB concentration shows a linear correspondence with the decrease in SERS spectral intensity. This linear relationship spans a concentration range of five orders of magnitude, and the limit of detection (LOD) is 1.47×10 -12M, indicating that the βAR nanomotor has high detection sensitivity.

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

[0053] After the βAR nanomotor captured RhB and was tested by SERS, the βAR nanomotor was added to 10 μL of ethanol. After separating the βAR nanomotor from the supernatant by an external magnet, it was immersed in ultrapure water to remove the remaining ions. Finally, the βAR nanomotor was magnetically recovered and vacuum dried at room temperature to achieve self-cleaning. The measurement results are as Figure 5 shown. It was observed that the SERS signal of RhB almost disappeared, indicating that the βAR nanomotor has good self-cleaning performance.

[0054] (4) Determination of the recyclability performance of the βAR nanomotor

[0055] After SERS characterization, 10 μL of ethanol was added to the βAR nanomotor that had captured pollutants to extract the pollutants. By SERS measurement, the adsorbed molecules were completely desorbed, and a clean βAR nanomotor was obtained. Subsequently, under the same experimental conditions as the initial test, the βAR nanocomposite was subjected to repeated cyclic SERS detection. Each detection and self-cleaning process was repeated 7 times, and the results are as Figure 6 shown. As can be seen from Figure 6 , even after seven "capture-detection-self-cleaning" cycles, although the SERS performance of the βAR nanomotor decreased slightly due to the disappearance of some "hot spots", the βAR nanomotor could still be reused, indicating that the βAR nanomotor has good recyclability performance.

[0056] In summary, the present invention prepared a magnetic motor capable of selectively capturing and highly sensitively detecting cationic dyes. The βAR nanomotor prepared by the present invention, based on the synergistic effect of electrostatic attraction and hydrogen bonds, can significantly improve the adsorption capacity, enabling the βAR nanomotor to highly selectively remove cationic dyes; the gold nanoparticles on the βAR nanomotor are uniformly fixed on the surface of the 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 having high detection sensitivity; in addition, the βAR nanomotor prepared by the present invention has excellent self-cleaning performance and recyclability performance, and is suitable for application in recyclable selective capture and highly sensitive SERS detection of cationic dyes.

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

Claims

1. A method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor, characterized in that: The following steps are involved: S1. Preparation of β-CD-OTf based on Hofmeister effect: Zn(OTf)2 solution and supersaturated β-CD solution were prepared separately, and β-CD-OTf was obtained after mixing based on host-guest interaction; S2, dispersing R-Fe3O4 in anhydrous ethanol, adding APTES as an amino coupling agent after ultrasonic treatment, reacting with ultrasonication and stirring, and washing the product after magnetic separation to obtain amino-functionalized R-Fe3O4, which was dispersed in deionized water for later use; S3, adding gold nanoparticles Au NPs to the amino-functionalized R-Fe3O4 dispersed in deionized water, stirring and centrifuging to obtain Au@R-Fe3O4, which is dispersed in deionized water for later use; S4. Au@R-Fe3O4 is coupled to β-CD-OTf through 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: prepare a Zn(OTf)2 solution with water as solvent, and completely dissolve it by ultrasound; prepare a supersaturated β-CD solution, and there is a white precipitate at the bottom of the supersaturated β-CD solution; add the Zn(OTf)2 solution dropwise to the supersaturated β-CD solution until the white precipitate at the bottom completely disappears, thereby obtaining a β-CD-OTf solution.

3. The method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor according to claim 2, characterized in that: 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.

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 amount of R-Fe3O4 added is 0.1-0.6 mg / mL anhydrous ethanol; the volume mass ratio of APTES to R-Fe3O4 is (0.5-1) mL:3 mg; ultrasonic treatment is performed for 25-35 min, and then mechanical stirring is performed at a rotation speed of 300-400 rpm for 5-7 h.

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 S2, the preparation method of R-Fe3O4 is: FeCl3, NaH2PO4 and anhydrous Na2SO4 were dissolved in deionized water, and the obtained mixture was transferred to a Teflon-lined stainless steel autoclave, and reacted at 200-250°C for 45-50 hours. After the reaction was completed, the mixture was cooled and allowed to stand overnight. After centrifugation, the obtained precipitate was washed with distilled water and anhydrous ethanol for multiple times, and finally dried at 70-90°C to obtain R-Fe2O3; The dried R-Fe2O3 powder is placed in a tubular furnace with a constant gas flow rate. The gas is a mixture of hydrogen and argon in a volume ratio of 1:

9. The tubular furnace is evacuated and then annealed at 400-500°C for 8-12 hours. After the tubular furnace is cooled to room temperature, R-Fe3O4 is obtained.

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 S3, the preparation method of the gold nanoparticles Au NPs is: adding chloroauric acid into a container and heating to boiling under continuous stirring; then quickly adding sodium citrate, and the color gradually changes from clear to dark; then boiling the solution until it turns wine red; after the reaction is completed, naturally cooling to room temperature to obtain spherical gold nanoparticles Au NPs.

7. 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, and the volume ratio between the β-CD-OTf solution and Au@R-Fe3O4 is 5:1; the mixture is ultrasonically stirred for 2-4 minutes, and then Au@R-Fe3O4 is coupled to β-CD-OTf by electrostatic action, and the magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotors are collected by an external magnet, and washed with ultrapure water multiple times to remove unbound Au@R-Fe3O4.

8. A magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor prepared by the method for preparing a magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor according to any one of claims 1 to 7.

9. Application of the magnetically sensitive β-CD-OTf@Au@R-Fe3O4 nanomotor prepared according to claim 8 in selective capture and highly sensitive SERS detection of cationic dyes.

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