Photosensitive Au (at) TiO2-Au NPs (at) R-Fe3O4 micron robot, preparation method thereof and application of micron robot in nano plastic detection
By preparing the photosensitive Au@TiO2-Au NPs@R-Fe3O4 microrobot, the sensitivity problems of nanoplastic capture and SERS detection are solved by using electrostatic coupling and visible light drive, and efficient capture and high sensitivity detection are achieved.
Patent Information
- Application Number
- CN202411005706.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-25
- Publication Date
- 2024-12-20
AI Technical Summary
The prior art cannot effectively capture and identify nanoplastics, and SERS detection methods are difficult to achieve high sensitivity analysis in water environments, due to problems such as insufficient adsorption sites, static adsorption and hydrophobic properties.
Prepare photosensitive Au@TiO2-Au NPs@R-Fe3O4 microrobot, couple Au NPs@R-Fe3O4 to Au@TiO2 microrobot through electrostatic action, and use visible light and water as fuel to achieve efficient capture of nanoplastics and enhance SERS Signal.
It realizes rapid capture of nanoplastics under visible light, significantly enhances SERS signals, achieves high sensitivity detection effect, and simplifies the detection process of nanoplastics.
Smart Images
Figure CN119158557A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of nanomaterials, and in particular to a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micron robot and a preparation method thereof, and application of the robot in high-sensitivity SERS detection of nanoplastics. Background Art
[0002] Plastics are ubiquitous in daily life due to their low cost and durability. Microplastics (<5mm) can be gradually decomposed into smaller nanoplastics (<1μm) through physical or chemical processes. Nanoplastics with larger surface areas are more likely to adsorb various toxic chemicals and trace metals to form "plastic balls", which can also serve as carriers for the spread of pathogens, increasing the risk of pollution to the aquatic environment and ecosystems. Trace nanoplastics are widely distributed in water, and low-content nanoplastics cannot be analyzed with high sensitivity. Adsorption has become one of the most widely used sewage treatment methods due to its low cost, simple use and strong practicality. However, the adsorption of commonly used adsorbents generally has insufficient adsorption sites, and is limited to short-range static adsorption, which cannot expand the capture range. Micro / nano robots can convert chemical or other forms of energy into driving forces and are widely used in the environmental field, but the robots do not have enough capture sites to accommodate more target nanoplastics, and cannot identify nanoplastics and cannot be recovered from aquatic environments, which limits their application and causes secondary pollution.
[0003] Surface-enhanced Raman spectroscopy (SERS) is used to detect environmental pollutants because of its ability to provide specific molecular vibration fingerprints without interference from water. However, the SERS method has not been widely used for the detection of nanoplastics. First, SERS detection is based on static adsorption between the substrate and the analyte, while nanoplastics are suspended in water due to their light weight and passive diffusion according to Lebron motion, which makes it impossible to perform accurate SERS detection in a controllable manner. Second, nanoplastics (<1μm) are much larger than hot spots (<10nm), and their hydrophobic properties prevent them from directly contacting the hot spots, making it impossible to obtain high-quality SERS signals. Third, nanoplastics have a weak affinity for metal surfaces and are also easily interfered by complex environmental components. Since trace nanoplastics are widely distributed in water, high-sensitivity analysis of low-content nanoplastics requires not only a strong driving force to expand the capture range of the static adsorption force, but also more adsorption sites to accommodate more target nanoplastics, and more hot spot areas to achieve stronger SERS sensing capabilities. Therefore, it is necessary to develop efficient, fast, and recyclable micro / nanorobotes to achieve real-time capture and high SERS recognition of nanoplastics. Summary of the invention
[0004] The purpose of the present invention is to provide a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot and its preparation method and application in high-sensitivity SERS detection of nanoplastics. The preparation method is simple, and the prepared photosensitive ATAR micro-robot can efficiently capture and accurately detect nanoplastics using water as fuel under visible light.
[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is:
[0006] A method for preparing a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot comprises the following steps:
[0007] S1. Preparation of Au@TiO2 microrobots
[0008] S1-1, the dried MXenes-Ti3C2T x Transformed into accordion-shaped TiO2;
[0009] S1-2, using MSP-2S magnetron target ion sputtering coating machine to sputter gold onto TiO2 to generate Au@TiO2 micro-robots;
[0010] S2. Preparation of Au NPs@R-Fe3O4
[0011] S2-1, preparing Fe2O3 powder by hydrothermal method with FeCl3 and additives;
[0012] S2-2, generating R-Fe3O4 by thermal annealing the dried Fe2O3 powder;
[0013] S2-3, using sodium citrate as a reducing agent to reduce chloroauric acid to prepare gold nanoparticles Au NPs;
[0014] S2-4, in situ assembling the positively charged R-Fe3O4 prepared in step S2-2 onto the negatively charged Au NPs prepared in step S2-3 to synthesize Au NPs@R-Fe3O4;
[0015] S3. The R-Fe3O4@Au NPs prepared in step S2 are coupled to the Au@TiO2 micro-robot prepared in step S1 through electrostatic action to obtain a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot.
[0016] Furthermore, the specific steps of step S1-1 are: drying the MXenes-Ti3C2T x The powder was heated to 550 °C in a muffle furnace at a heating rate of 10 °C / min and converted into accordion-shaped TiO2.
[0017] Furthermore, the specific steps of step S1-2 are: preparing the accordion-shaped TiO2 prepared in step S1-1 into a solution, placing the solution on a silicon wafer to dry so that the TiO2 is evenly spread on the silicon wafer, and the silicon wafer is placed on a sample table; then using an MSP-2S magnetron target ion sputtering coating machine to sputter gold onto the TiO2, after sputtering, the silicon wafer is dispersed in deionized water, and Au@TiO2 is ultrasonically separated from the silicon wafer, and finally Au@TiO2 is dried to obtain an Mxene-derived Au@TiO2 micron robot; the distance between the metal target on the coating machine and the sample table is 3-5 cm, the sputtering time is 30 s, and the sputtering process is repeated three times.
[0018] Furthermore, the specific steps of step S2-1 are: completely dissolving FeCl3, NaH2PO4 and Na2SO4 in ultrapure water, transferring the resulting mixture to a Teflon-lined stainless steel autoclave, reacting at 210-230°C for 45-50h, washing the red precipitate after centrifugation with ultrapure water and anhydrous ethanol for multiple times, and obtaining powdered Fe2O3 after vacuum drying at 70-90°C.
[0019] Furthermore, the specific steps of step S2-2 are: placing the dried Fe2O3 powder in a constant flow gas tube furnace, the gas is a mixture of hydrogen and argon in a volume ratio of 8:92; annealing at 400-500°C for 8-12h, after the tube furnace is cooled to room temperature, exposing the black powder to air at 250-260°C for 2-4h for oxidation to obtain R-Fe3O4.
[0020] Furthermore, the specific steps of step S2-3 are: adding chloroauric acid into a container and heating to boiling under constant 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.
[0021] Furthermore, the specific steps of step S2-4 are:
[0022] a. Disperse R-Fe3O4 in anhydrous ethanol, wherein the amount of R-Fe3O4 added is 0.5-0.7 mg / mL anhydrous ethanol, and add APTES, wherein the volume mass ratio of APTES to R-Fe3O4 is (0.5-1.5) mL:3 mg; subject the mixed solution to ultrasonic treatment for 4-6 min to uniformly disperse the mixed solution, and then mechanically stir the mixed solution at a speed of 300-400 rpm for 5-7 h, bridge the surface of R-Fe3O4 with -NH2 to make the surface positively charged, and recover the amino-functionalized R-Fe3O4 nanoparticles with a permanent magnet, and then disperse the obtained nanoparticles in deionized water for later use;
[0023] b. Add the amino-functionalized R-Fe3O4 nanoparticles dispersed in ultrapure water to the gold nanoparticle Au NPs solution, stir mechanically at a speed of 300-400 rpm for 2-4 h, perform magnetic separation on the prepared solution with an external magnet, wash the obtained product in deionized water several times to obtain Au NPs@R-Fe3O4, and disperse it in deionized water for later use.
[0024] Furthermore, the specific steps of step S3 are: uniformly dispersing the Au@TiO2 microrobot prepared in step S1 in deionized water, adding the Au NPs@R-Fe3O4 prepared in step S2 after ultrasound, coupling the Au NPs@R-Fe3O4 to the Au@TiO2 microrobot by electrostatic action after mechanical stirring, collecting with an external magnet and washing multiple times to remove unbound Au NPs@R-Fe3O4, thereby obtaining a photosensitive Au@TiO2-Au NPs@R-Fe3O4 microrobot.
[0025] The present invention also provides a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot prepared by the above preparation method.
[0026] The present invention also provides the use of the photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot prepared by the above preparation method as a substrate in high-sensitivity SERS detection of nano-plastics.
[0027] Compared with the prior art, the present invention has the following beneficial effects:
[0028] The preparation method of the present invention is to couple Au NPs@R-Fe3O4 to Au@TiO2 micro-robots through electrostatic action, and prepare visible light-sensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robots (hereinafter referred to as "photosensitive ATAR micro-robots") using water as fuel, which are used to efficiently capture and accurately detect nano-plastics. The preparation method of the present invention is simple, and the prepared photosensitive ATAR micro-robots can achieve efficient capture of nano-plastics within 2 minutes under visible light using water as fuel based on the stacking structure and electrostatic action between MXene-derivatized TiO2 layers; the electromagnetic field enhancement area provided by the Au NPs inside and outside the Fe3O4 ring of the photosensitive ATAR micro-robot of the present invention enhances the SERS signal of the captured nano-plastics by several times. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 A flow chart for preparing a photosensitive ATAR micro robot according to an embodiment of the present invention;
[0030] Figure 2The SEM image (a) and TEM image (b) of the photosensitive ATAR microrobot prepared in the embodiment of the present invention;
[0031] Figure 3 A schematic diagram of the motion performance results of the photosensitive ATAR micro robot prepared according to an embodiment of the present invention;
[0032] Figure 4 Schematic diagram of the SERS performance results of the photosensitive ATAR micro-robot prepared in the embodiment of the present invention, wherein (a) SERS spectra of different concentrations of PS nanoplastics adsorbed on the ATAR micro-robot: I represents 320μg / mL, II represents 160μg / mL, III represents 80μg / mL, IV represents 40μg / mL, V represents 20μg / mL, VI represents 10μg / mL, and VIII represents 5μg / mL, (b) 1000cm -1 The relationship between the logarithmic SERS intensity and the logarithmic PS concentration. DETAILED DESCRIPTION
[0033] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0034] The substance names represented by the English abbreviations used in the present invention are as follows:
[0035] Example
[0036] like Figure 1 As shown, a method for preparing a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot comprises the following steps:
[0037] S1. Preparation of Au@TiO2 microrobots
[0038] S1-1, the dried MXenes-Ti3C2T x The powder was heated to 550 °C in a muffle furnace at a heating rate of 10 °C / min and converted into accordion-shaped TiO2;
[0039] S1-2, the accordion-shaped TiO2 prepared in step S1-1 is prepared into a solution with a concentration range of 10 mg / mL, the solution is placed on a silicon wafer to dry so that the TiO2 is evenly spread on the silicon wafer, and the silicon wafer is placed on a sample stage; then, gold is sputtered onto the TiO2 using an MSP-2S magnetron target ion sputtering coating machine, after the sputtering is completed, the silicon wafer is dispersed in deionized water, and Au@TiO2 is separated from the silicon wafer by ultrasonication for 3 minutes, and finally, the Au@TiO2 is dried to obtain an Mxene-derived Au@TiO2 micron robot; the distance between the metal target on the coating machine and the sample stage is 4 cm, the sputtering time is 30 seconds, and the sputtering process is repeated three times;
[0040] S2. Preparation of Au NPs@R-Fe3O4
[0041] S2-1, 0.0624M FeCl3, 5.6×10 -4 0.0017 M NaH2PO4 and 0.0017 M Na2SO4 were completely dissolved in 80 mL ultrapure water, and the resulting mixture was transferred to a 100 mL Teflon-lined stainless steel autoclave and reacted at 220 °C for 48 h. The red precipitate after centrifugation was washed with ultrapure water and anhydrous ethanol for several times, and then dried in vacuo at 80 °C to obtain powdered Fe2O3;
[0042] S2-2, the dried Fe2O3 powder was placed in a constant flow gas tube furnace, the gas was a mixture of hydrogen and argon with a volume ratio of 8:92; annealed at 450°C for 10 hours, after the tube furnace was cooled to room temperature, the black powder was exposed to air at 240°C for 2 hours for oxidation to obtain R-Fe3O4;
[0043] S2-3, add 100mL, 0.01%wt chloroauric acid into a 250mL round-bottom flask, heat to boiling under constant stirring, then quickly add 3mL 1%wt sodium citrate to the boiling solution, the color of which gradually changes from clear to dark; boil the solution for 30 minutes until it turns wine red; after the reaction is completed, cool naturally to room temperature to obtain spherical gold nanoparticles with a particle size of 16nm;
[0044] S2-4, in situ assembling the positively charged R-Fe3O4 prepared in step S2-2 onto the negatively charged Au NPs prepared in step S2-3 to synthesize Au NPs@R-Fe3O4, the specific steps are:
[0045] a. Disperse 6 mg of dried R-Fe3O4 in 10 mL of anhydrous ethanol, add 2 mL of APTES, and ultrasonicate for 5 min to make it evenly dispersed. After mechanical stirring for 6 h (350 rpm), bridge the surface of R-Fe3O4 with -NH2 to make the surface positively charged. The amino-functionalized R-Fe3O4 nanoparticles are recovered and washed with a permanent magnet, and then dispersed in 5 mL of superdeionized water.
[0046] b. Add 1 mL of functionalized R-Fe3O4 to 10 mL of a gold nanoparticle Au NPs solution with a particle size of 16 nm, and stir mechanically at 350 rpm for 3 h. The prepared solution is magnetically separated using an external magnet. The obtained product is washed several times in deionized water to obtain Au NPs@R-Fe3O4, which is dispersed in 5 mL of deionized water for later use.
[0047] S3, coupling the R-Fe3O4@Au NPs prepared in step S2 to the Au@TiO2 micro-robot prepared in step S1 through electrostatic action to obtain a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot, the specific steps are:
[0048] 10 mg of Au@TiO2 microrobot was evenly dispersed in 5 mL of deionized water. After ultrasonic treatment for 10 min, 2 mg of Au NPs@R-Fe3O4 was added and mechanically stirred for 3 h. Then, Au@TiO2 was coupled to the Au NPs@R-Fe3O4 nanoring by electrostatic action. Unbound Au NPs@R-Fe3O4 was removed by collecting with an external magnet and washed several times to obtain the photosensitive ATAR microrobot. The SEM and TEM images of the prepared photosensitive ATAR microrobot are shown in Figure 2. Figure 2 As shown, the SEM image clearly shows the uniform distribution of AuNPs@R-Fe3O4 nanorings on the ATAR microrobot, and TEM further shows that the magnetic nanoparticles are uniformly adhered to the ATAR microrobot.
[0049] The photosensitive ATAR micro robot prepared in this embodiment was subjected to motion performance measurement and SERS performance measurement, and the test process and results are as follows:
[0050] (1) Measurement of the motion performance of the photosensitive ATAR microrobot
[0051] The cyclic motion of the ATAR microrobot in the on / off mode of a xenon lamp in water was observed and recorded using a confocal Raman imaging spectrometer on an inverted microscope. Figure 3 The final speed of the ATAR micro robot at 5-second intervals under the control of the on-off light. The ATAR micro robot will not actively move forward in the dark, but will only show random Brownian motion. When the xenon lamp is turned on, it will start to move immediately. Under the action of the xenon lamp, the average movement speed of the ATAR micro robot dynamically switches between 25.83182μm / s and 16.67μm / s, and the response is fast. When the xenon lamp is turned off, the speed of the ATAR micro robot first drops significantly, and then stabilizes.
[0052] (2) SERS performance measurement of the photosensitive ATAR microrobot
[0053] The ATRA microrobot (1 mg) was immersed in a series of glass bottles (5 ml) containing different concentrations of PS dispersion (1 ml, 500 nm). After irradiation with a xenon lamp (300 w) at a wavelength of 400 nm for 5 min, the microrobot was separated from the solution by a permanent magnet and then SERS detection was performed with an integration time of 20 s and a laser power of 50%. In the range of 5 to 320 μg / mL, the peak intensity of PS nanoplastics decreased with decreasing concentration ( Figure 4 a). At 1000cm -1 The characteristic peak intensity at is linearly correlated with the concentration of PS nanoplastics ( Figure 4 b), the calculated limit of detection (LOD) was 1.27 μg / mL, indicating that the ATRA microrobot has a high detection sensitivity.
[0054] In summary, the preparation method of the present invention is to couple Au NPs@R-Fe3O4 to Au@TiO2 micro-robots through electrostatic action, and prepare visible light-sensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robots (hereinafter referred to as "photosensitive ATAR micro-robots") using water as fuel, which are used to efficiently capture and accurately detect nano-plastics. The preparation method of the present invention is simple, and the prepared photosensitive ATAR micro-robot is based on the stacking structure and electrostatic action between MXene-derivatized TiO2 layers, and achieves efficient capture of nano-plastics within 2 minutes using water as fuel under visible light; the electromagnetic field enhancement area provided by the Au NPs inside and outside the Fe3O4 ring of the photosensitive ATAR micro-robot of the present invention enhances the SERS signal of the captured nano-plastics by several times.
[0055] The above is only a preferred specific implementation manner of the present invention, and the protection scope of the present invention is not limited thereto. Any simple change or equivalent replacement of the technical solution that can be obviously obtained by any technician familiar with the technical field within the technical scope disclosed in the present invention falls within the protection scope of the present invention.
Claims
1. A method for preparing a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot, characterized in that: The following steps are involved: S1. Preparation of Au@TiO2 microrobots S1-1, the dried MXenes-Ti3C2T x Transformed into accordion-shaped TiO2; S1-2, using MSP-2S magnetron target ion sputtering coating machine to sputter gold onto TiO2 to generate Au@TiO2 micron robot; S2. Preparation of AuNPs@R-Fe3O4 S2-1, preparing Fe2O3 powder by hydrothermal method with FeCl3 and additives; S2-2, generating R-Fe3O4 by thermal annealing the dried Fe2O3 powder; S2-3, using sodium citrate as a reducing agent to reduce chloroauric acid to prepare gold nanoparticles AuNPs; S2-4, in situ assembling the positively charged R-Fe3O4 prepared in step S2-2 onto the negatively charged Au NPs prepared in step S2-3 to synthesize Au NPs@R-Fe3O4; S3. The R-Fe3O4@Au NPs prepared in step S2 are coupled to the Au@TiO2 micro-robot prepared in step S1 through electrostatic action to obtain a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot.
2. The method for preparing a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot according to claim 1, characterized in that: The specific steps of step S1-1 are: drying the MXenes-Ti3C2T x The powder was heated to 550 °C in a muffle furnace at a heating rate of 10 °C / min and converted into accordion-shaped TiO2.
3. The method for preparing a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot according to claim 1, characterized in that: The specific steps of step S1-2 are: prepare the accordion-shaped TiO2 prepared in step S1-1 into a solution, place the solution on a silicon wafer and dry it so that the TiO2 is evenly spread on the silicon wafer, and the silicon wafer is placed on a sample table; then use an MSP-2S magnetron target ion sputtering coating machine to sputter gold onto the TiO2, after sputtering, disperse the silicon wafer in deionized water, and ultrasonically separate Au@TiO2 from the silicon wafer, and finally dry the Au@TiO2 to obtain an Mxene-derived Au@TiO2 micron robot; the distance between the metal target on the coating machine and the sample table is 3-5 cm, the sputtering time is 30 s, and the sputtering process is repeated three times.
4. The method for preparing a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot according to claim 1, characterized in that: The specific steps of step S2-1 are: completely dissolving FeCl3, NaH2PO4 and Na2SO4 in ultrapure water, transferring the resulting mixture to a Teflon-lined stainless steel autoclave, reacting at 210-230°C for 45-50h, washing the red precipitate after centrifugation with ultrapure water and anhydrous ethanol for multiple times, and vacuum drying at 70-90°C to obtain powdered Fe2O3.
5. The method for preparing a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot according to claim 1, characterized in that: The specific steps of step S2-2 are: placing the dried Fe2O3 powder in a constant flow gas tube furnace, the gas is a mixture of hydrogen and argon with a volume ratio of 8:92; annealing at 400-500°C for 8-12 hours, after the tube furnace is cooled to room temperature, exposing the black powder to air at 250-260°C for 2-4 hours to oxidize to obtain R-Fe3O4.
6. The method for preparing a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot according to claim 1, characterized in that: The specific steps of step S2-3 are: adding chloroauric acid into a container and heating to boiling under constant 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 photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot according to claim 1, characterized in that: The specific steps of step S2-4 are: a. Disperse R-Fe3O4 in anhydrous ethanol, wherein the amount of R-Fe3O4 added is 0.5-0.7 mg / mL anhydrous ethanol, and add APTES, wherein the volume mass ratio of APTES to R-Fe3O4 is (0.5-1.5) mL:3 mg; subject the mixed solution to ultrasonic treatment for 4-6 min to uniformly disperse the mixed solution, and then mechanically stir the mixed solution at a speed of 300-400 rpm for 5-7 h, bridge the surface of R-Fe3O4 with -NH2 to make the surface positively charged, and recover the amino-functionalized R-Fe3O4 nanoparticles with a permanent magnet, and then disperse the obtained nanoparticles in deionized water for later use; b. Add the amino-functionalized R-Fe3O4 nanoparticles dispersed in ultrapure water to the gold nanoparticle Au NPs solution, stir mechanically at a speed of 300-400 rpm for 2-4 h, perform magnetic separation on the prepared solution with an external magnet, wash the obtained product in deionized water several times to obtain Au NPs@R-Fe3O4, and disperse it in deionized water for later use.
8. The method for preparing a photosensitive Au@TiO2-Au NPs@R-Fe3O4 micro-robot according to claim 1, characterized in that: The specific steps of step S3 are: uniformly dispersing the Au@TiO2 microrobot prepared in step S1 in deionized water, adding the Au NPs@R-Fe3O4 prepared in step S2 after ultrasound, coupling the AuNPs@R-Fe3O4 to the Au@TiO2 microrobot through electrostatic action after mechanical stirring, collecting with an external magnet and washing multiple times to remove unbound Au NPs@R-Fe3O4, thereby obtaining a photosensitive Au@TiO2-Au NPs@R-Fe3O4 microrobot.
9. A photosensitive Au@TiO2-AuNPs@R-Fe3O4 microrobot prepared by the preparation method of the photosensitive Au@TiO2-Au NPs@R-Fe3O4 microrobot according to any one of claims 1 to 8.
10. Use of the photosensitive Au@TiO2-Au NPs@R-Fe3O4 microrobot prepared according to claim 9 as a substrate in highly sensitive SERS detection of nanoplastics.