Asymmetric self-assembly structure and method of Fe3O4 (at) Au nanoparticles and photoresponse composite tuning structure

Abstract

The invention discloses a Fe3O4 (at) Au nanoparticle asymmetric self-assembly structure and method and a photoresponse composite tuning structure, Fe3O4 (at) Au nanoparticles are used as basic construction units to form a swastika shape, and the self-assembly structure cannot coincide with a mirror image of the self-assembly structure; the self-assembly structure is composed of two parts which are orthogonal to each other, the two parts share one Fe3O4 (at) Au nanoparticle, each part comprises two structural arms and a structural main shaft, each structural arm and the structural main shaft are composed of a plurality of Fe3O4 (at) Au nanoparticles, the two structural arms are perpendicular to the structural main shaft to form a right-angle Z shape, and the Fe3O4 (at) Au nanoparticles are arranged in the right-angle Z shape. And the two structural arms respectively share one Fe3O4 (at) Au nanoparticle with the structural main shaft.

Description

Technical Field

[0001] This invention relates to the field of functional nanomaterials technology, and in particular to an asymmetric self-assembly structure and method of Fe3O4@Au nanoparticles and a photoresponsive composite tuning structure. Background Technology

[0002] Magnetoplatinic nanoparticles, such as the Fe3O4@Au core-shell structure, are highly favored in the field of nanomaterials due to their unique dual-functional integrated properties. The Fe3O4 core endows them with excellent magnetic response properties, allowing them to be precisely manipulated by external magnetic fields, while the Au shell provides superior localized surface plasmon resonance (LSPR) properties, good biocompatibility, and easy surface functionalization. Compared to single-component nanoparticles, such as pure magnetic nanoparticles or pure gold nanoparticles, the gold magnetic core-shell structure has higher stability, tunability, and multifunctionality, making it a promising candidate for applications in targeted drug delivery, enhanced magnetic resonance imaging (MRI), tumor hyperthermia, catalysis, and surface-enhanced Raman scattering (SERS) detection.

[0003] By orderly assembling and precisely controlling Fe3O4@Au nanoparticles, their self-assembled structures can acquire superior properties beyond those of the nanoparticles themselves, exhibiting characteristics not found in conventional materials in the fields of magnetism, electricity, and optics. Furthermore, under external incident light irradiation, the asymmetric self-assembled structure, by breaking the geometric constraints of traditional symmetrical structures, can confine light energy within an extremely small space, generating a very strong local electromagnetic field between the nanoparticles. Based on the strong electromagnetic coupling between the nanoparticles and between them and the incident light, the asymmetric self-assembled structure can exhibit unique and flexibly tunable photoresponses and magnetic responses, showing considerable application potential in the development of novel optical devices and functional metamaterials.

[0004] Existing research shows that although symmetrical assembly structures can also produce unique optical spectral lines, they still have significant limitations: First, their optical response modes are usually relatively simple, mainly due to electric dipole resonance hybridization, making it difficult to excite higher-order quadrupole or magnetic dipole resonances; second, their resonance bands are relatively concentrated, making it difficult to respond to more complex requirements, which greatly limits their application in cutting-edge fields such as high-precision biosensing. Summary of the Invention

[0005] The purpose of this invention is to provide an asymmetric self-assembly structure and method for Fe3O4@Au nanoparticles and a photoresponsive composite tuning structure, so as to solve the problems of high symmetry, single photoresponse mode and insufficient tuning capability of existing assembly structures.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: Asymmetric self-assembled structure of Fe3O4@Au nanoparticles. The self-assembled structure uses Fe3O4@Au nanoparticles as basic building units to form a "卍" shape, and the self-assembled structure is non-superimposable with its mirror image; The self-assembled structure consists of two mutually orthogonal parts, and the two parts share a Fe3O4@Au nanoparticle. Each part includes two structural arms and a structural main axis. The structural arms and the structural main axis are both composed of several Fe3O4@Au nanoparticles. The two structural arms are perpendicular to the structural main axis, forming a "right-angled Z" shape, and the two structural arms share a Fe3O4@Au nanoparticle with the structural main axis respectively.

[0007] Furthermore, the Fe3O4@Au nanoparticles have a Fe3O4 core and a Au shell, and the diameter of the Fe3O4@Au nanoparticles is less than the wavelength of the incident light, where the incident light is the incident light during the light response test.

[0008] Furthermore, in the self-assembled structure, the distance between adjacent Fe3O4@Au nanoparticles is ≥ 2 nm.

[0009] Self-assembly method of the asymmetric self-assembled structure of Fe3O4@Au nanoparticles, including the following steps: The first step is to use a silicon wafer as the bottom substrate, fabricate a "卍" - shaped soft magnetic body array on the silicon wafer, and then deposit a Au thin film with a preset thickness around the "卍" - shaped soft magnetic body array to form a soft magnetic body mold. The material of the soft magnetic body array is permalloy, and the thickness of the Au thin film is higher than that of the "卍" - shaped soft magnetic body array. A groove with the same shape as the "卍" - shaped soft magnetic body and a depth equivalent to the diameter of the Fe3O4@Au nanoparticles is formed above the "卍" - shaped soft magnetic body array; The second step is to load a microfluidic channel on the soft magnetic body mold. The microfluidic channel is a suspension of Fe3O4@Au nanoparticles. At the same time, a permanent magnet is used to provide an external bias magnetic field to guide the Fe3O4@Au nanoparticles to complete the assembly of the "卍" - shaped structure.

[0010] Furthermore, in the second step, the velocity of the Fe3O4@Au nanoparticle suspension at the inlet of the microfluidic channel is set v in = 1 mm / s.

[0011] Furthermore, in the second step, the magnetic induction intensity of the external bias magnetic field B bias = 500 mT.

[0012] Furthermore, it further includes a third step. After the assembly is completed, the velocity of the Fe3O4@Au nanoparticle suspension is increased to v in= 0.3 m / s to remove stray particles deposited near the grooves.

[0013] The light-responsive composite tuning structure, based on the above Fe3O4@Au nanoparticle asymmetric self-assembly structure, includes a target substrate and the Fe3O4@Au nanoparticle asymmetric self-assembly structure disposed on the target substrate.

[0014] Furthermore, the target substrate is glass, a metal backplane or a flexible film.

[0015] Furthermore, by controlling the type of the target substrate, the core or shell size of the Fe3O4@Au nanoparticles, the compactness of the Fe3O4@Au nanoparticles, the polarization direction of the external incident photoelectric field, and the surrounding medium environment, flexible regulation of the light response of the "卍"-shaped Fe3O4@Au nanoparticle asymmetric self-assembly structure is achieved.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: In the present invention, by assembling Fe3O4@Au nanoparticles into a "卍"-shaped asymmetric structure, close arrangement of the particles is achieved. Under the excitation of incident light, based on the electromagnetic near-field coupling effect between the particles, the asymmetric self-assembly structure can produce a significant local electromagnetic field enhancement effect at the gaps between adjacent particles. In particular, the "卍"-shaped asymmetric structure can form four "U"-shaped regions with different opening directions but uniform distribution, which have the structural characteristics of a kind of open resonant ring. Under the excitation of a specific wavelength, a circular current can be induced, equivalently realizing magnetic dipole resonance, making the structure have the cooperative regulation ability of both light response and magnetic response.

[0017] Based on the excellent magnetic response ability of Fe3O4@Au nanoparticles, under the drive of an external gradient magnetic field, with the geometric constraint of the "卍"-shaped groove and the high local strong magnetic dipole attraction of the "卍"-shaped soft magnet, Fe3O4@Au nanoparticles are guided to self-assemble into a stable asymmetric structure. This scheme effectively improves the consistency of the assembled structure, and the reusability of the soft magnet mold also makes the entire assembly process highly controllable.

[0018] In the present invention, by transferring the "卍"-shaped asymmetric self-assembly structure to different target substrates to form a light-responsive composite tuning structure, and at the same time by controlling factors such as the size of Fe3O4@Au nanoparticles and the surrounding medium environment, a series of specific tunable light responses with high quality factors ( Q ≥31) and high sensitivities (≥1777.8 nm / RIU) are obtained. This advantage also makes the present invention have the potential to be used as the core unit of a high-precision optical sensor to achieve ultrasensitive detection of analytes such as biomolecules, with prominent application value. Brief Description of the Drawings

[0019] The accompanying drawings of the specification are used to provide a further understanding of the present invention and form a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0020] Figure 1 are the plan top view and three-dimensional perspective view of the “卍”-shaped Fe3O4@Au nanoparticle asymmetric self-assembly structure, where: (a) is the plan top view and (b) is the three-dimensional perspective view; Figure 2 is the process schematic diagram of the self-assembly of the “卍”-shaped asymmetric structure completed by using the microfluidics-assisted magnetic field-driven nanoparticle self-assembly technology, where: (a) the stacked structure of the Si substrate, the “卍”-shaped soft magnet array and the Au thin film, (b) the schematic diagram of the microfluidics-assisted magnetic field-driven Fe3O4@Au nanoparticle self-assembly system; Figure 3 are the three-dimensional full-wave calculation model for analyzing the optical response of the “卍”-shaped self-assembly structure and its transmission spectrum diagram, where: (a) is the three-dimensional full-wave calculation model and (b) is the transmission spectrum; Figure 4 is in Figure 3 the model scenario, the local electric field enhancement and magnetic response of the self-assembly structure, where: (a) surface charge and current, (b) central plane electric field distribution, (c) magnetic field distribution of the Y1 and Y2 sections; Figure 5 is the regulation of the optical response of the structure by controlling the polarization direction of the incident optical electric field (glass substrate, the polarization direction of the incident optical electric field is y axis), where: (a) surface charge and current, (b) central plane electric field distribution, (c) magnetic field distribution of the X1 and X2 sections; Figure 6 is the regulation of the optical response by controlling the self-assembly structure parameters (glass substrate), where: (a) particle core radius R core , (b) Au shell thickness​​​​​​​​​​​​​​​Under the model scenario, the local electric field enhancement and magnetic response of the self-assembled structure, where: (a) Schematic diagram of the positions of Z1 on the upper surface of the Al2O3 dielectric layer, the upper horizontal arm (rose gold), the central horizontal axis (purple), and the lower horizontal arm (yellow) of the assembled structure, (b) Electric field distribution in the central plane, (c) Positive projection of the current density in the XZ direction: The red arrows represent the current flowing through the particle surface, and the currents flowing through the upper horizontal arm, the central horizontal axis, and the lower horizontal arm of the structure are denoted as I 1, I 2, and I 3, and the white arrows represent the current flowing through the Au backplane. (d) Magnetic field distribution in the Z1 plane. Specific implementation manners

[0021] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily need to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0023] Embodiment 1 The present invention proposes a "卍"-shaped Fe3O4@Au nanoparticle asymmetric self-assembled structure with specific optical response, and intuitively demonstrates its optical spectrum and the regulation of its optical response characteristics by factors such as particle size and surrounding medium environment with the help of a three-dimensional full-wave calculation model.

[0024] The self-assembled structure uses Fe3O4@Au nanoparticles as the basic building units, and the overall self-assembled structure cannot coincide with its mirror image.

[0025] See Figure 1The self-assembled structure consists of two orthogonal parts that share a single Fe3O4@Au nanoparticle. Each part includes two structural arms and a structural main axis. Both structural arms and the structural main axis are composed of several Fe3O4@Au nanoparticles. The two structural arms are perpendicular to the structural main axis, forming a "right-angled Z" shape. Each of the two structural arms shares a single Fe3O4@Au nanoparticle with the structural main axis.

[0026] The radius of the Fe3O4@Au nanoparticle core (Fe3O4) is [missing information]. R core The shell (Au) thickness is t s The radius of Fe3O4@Au nanoparticles R = R core + t s The structural arm length is L a The overall length is L x Width is L y Its length and width are equal, both equal to the dimensions of the main axis of the structure.

[0027] Fe3O4@Au nanoparticles, as a type of nanoparticle with a double core-shell structure, possess many unique properties, including those of metal nanoparticles, organic nanoparticles, and inorganic nanoparticles, providing favorable conditions for generating a specific photoresponse.

[0028] Under external incident light, free electrons on the gold shell surface undergo collective oscillation, generating localized surface plasmons (LSPs). When the incident light frequency matches the oscillation frequency of the free electrons, localized surface plasmon resonance (LSPR) occurs on the metal surface, resulting in a strong enhancement of the surrounding local electric field. Furthermore, the magnetic core endows Fe3O4@Au nanoparticles with excellent magnetic response characteristics, enabling them to efficiently and stably self-assemble this swastika-shaped asymmetric structure under the control of an external gradient magnetic field.

[0029] Example 2 See Figure 2 The specific assembly process of the Fe3O4@Au nanoparticle asymmetric self-assembly structure of the present invention is as follows: The first step involves using a silicon wafer as the substrate to fabricate a swastika-shaped soft magnetic array. Then, a pre-determined thickness Au film is deposited around the swastika-shaped soft magnetic array to form the soft magnetic mold shown in Figure (a). The material of the soft magnetic array is permalloy (78% Fe, 22% Ni by mass fraction). The geometric dimensions of a single swastika-shaped soft magnetic element are as follows: L 1 = 600 nmL 2 = 400 nm, L 3 = L 4 = 200 nm, h = 200 nm. It should be noted that the thickness of the Au film is higher than that of the soft magnetic array, forming a groove with a depth equivalent to the diameter of the Fe3O4@Au nanoparticles, as shown by the yellow part in Figure (a); In the second step, particle assembly is carried out. A microfluidic channel is loaded onto the soft magnetic mold, and the velocity of the Fe3O4@Au nanoparticle suspension at the inlet of the microfluidic channel shown in Figure (b) is set v in = 1 mm / s. At the same time, a permanent magnet is used to provide an external bias magnetic field (magnetic induction intensity B bias = 500 mT) for the self-assembly system to guide the Fe3O4@Au nanoparticles to complete the assembly of the "卍" - shaped structure; In the third step, after the particle assembly is completed, the velocity of the Fe3O4@Au nanoparticle suspension is increased to v in = 0.3 m / s to remove the stray particles deposited near the groove, and thus the assembly process is completed.

[0030] Example Three The present invention realizes flexible regulation of the light response of the "卍" - shaped Fe3O4@Au nanoparticle asymmetric self - assembly structure by controlling the type of the target substrate, the core or shell size of the Fe3O4@Au nanoparticles, the compactness of the Fe3O4@Au nanoparticles, the polarization direction of the external incident photoelectric field, and the surrounding medium environment.

[0031] In addition, the present invention proposes to obtain parameters such as its absorption power through three - dimensional full - wave computational analysis of the light response of the "卍" - shaped Fe3O4@Au nanoparticle asymmetric self - assembly structure, which lays a foundation for further research on the photothermal conversion characteristics of the "卍" - shaped Fe3O4@Au nanoparticle asymmetric self - assembly structure, and provides a basis for the selection of laser wavelength, light power, and laser duration.

[0032] The "卍" - shaped asymmetric self - assembly structure is respectively transferred onto a glass substrate and an Al2O3 dielectric layer with an Au backplane. A three - dimensional full - wave computational model of its optical response is established using COMSOL Multiphysics 6.2. The Helmholtz wave equation is used to describe the time - harmonic electric field in the computational domain, and it is set that the external incident light propagates along the - z axis. In addition, perfect matched layers (PML) are respectively set at the top and bottom of the three - dimensional full - wave computational model to reduce the backscattering at the boundaries, and at the same time, periodic boundary conditions are applied to simulate the two - dimensional array of the infinitely arranged "卍" - shaped self - assembly structures.

[0033] Figure 3 To analyze the three-dimensional full-wave computational model and transmission spectrum of the optical response of the swastika-shaped self-assembled structure, the following figures are provided: (a) three-dimensional full-wave computational model, (b) transmission spectrum; in figure (a), the light blue substrate is glass, and the particle size is... R core = 80 nm t s = 20 nm, the polarization direction of the incident photoelectric field is along x The axis is surrounded by water; two distinct resonance valleys T1 can be observed in Figure (b). λ =2.1 μm), T2 ( λ =2.74 μm), at the resonant wavelength of 2.74 μm, due to the coupling effect between the bright mode and the dark mode, T2 exhibits a narrow and deep valley with extremely low radiation loss.

[0034] Figure 4 In order to be in Figure 3 Under the model scenario, the local electric field enhancement and magnetic response of the self-assembled structure are shown in Figure (a): surface charge and current, (b) electric field distribution in the central plane, and (c) magnetic field distribution in the Y1 and Y2 cross-sections. Figure (a) shows that incident light at T2 can induce clockwise and counterclockwise circular currents in the "U"-shaped regions at the upper right and lower left corners of the assembled structure, respectively, forming magnetic dipole moments. Figure (b) shows that the strong electromagnetic near-field coupling between nanoparticles leads to a significant enhancement of the local electric field between particles, especially at the central horizontal axis particle gap, where the "hot spot" field strength reaches as high as 8 × 10⁻⁶. 9 V m -1 In Figure (c), the Y1 and Y2 cross-sections pass through the middle of the "U"-shaped regions in the upper right and lower left corners, respectively. Observing the magnetic field distribution of the two cross-sections, it is found that the magnetic field at the center of the "U"-shaped region is relatively weak, while the magnetic field near the particle is stronger, which is consistent with the magnetic field distribution law of a single-turn ring current.

[0035] Figure 5 To control the effect of the incident photoelectric field polarization direction on the structured light response (glass substrate, incident photoelectric field polarization direction is...) y (Axis), where: (a) surface charge and current, (b) electric field distribution in the central plane, and (c) magnetic field distribution in the X1 and X2 cross-sections; it can be observed from Figure (a) that the incident light at T2 can be different from the X1 and X2 cross-sections. Figure 4 (a) The region shown in the figure is induced with a ring current, forming a magnetic dipole moment; as can be observed in Figure (b), the local electric field between particles on the central vertical axis is significantly enhanced at this time; in Figure (c), the cross-sections X1 and X2 pass through the middle positions of the "U"-shaped regions in the upper left and lower right corners, respectively, and their magnetic field distribution pattern is consistent with the electric field polarization direction along the middle position of the "U"-shaped region in the upper left and lower right corners, respectively. x The axis is consistent.

[0036] Figure 6 To control the modulation of the optical response by self-assembled structural parameters (glass substrate), where: (a) particle nucleus radius R core (b) Gold casing thickness t s (c) Refractive index of the surrounding medium n s (d) Spacing between the centers of the particle surfaces S It can be observed that, with R core As the wavelength increases, the resonant wavelength of the structure exhibits a significant redshift at T1, while only a slight redshift occurs at T2; with... t s As the wavelength increases, the resonant wavelength of the structure exhibits a slight redshift at both T1 and T2, and the transmittance decreases significantly; when the assembled structure is placed in different media environments, with... n s With the increase of the particle spacing, the resonance wavelength exhibits a significant redshift at both T1 and T2, with sensitivities reaching 1444.4 nm / RIU and 1777.8 nm / RIU, respectively, fully demonstrating the flexible tunability of the structure's optical response. Furthermore, the resonance wavelength of the assembled structure at both T1 and T2 varies with the inter-particle spacing. S A slight redshift occurs due to the decrease in [something].

[0037] Figure 7 To analyze the three-dimensional full-wave computational model and absorption spectrum of the photoresponse of the swastika-shaped self-assembled structure, where: (a) three-dimensional full-wave computational model, (b) absorption spectrum; in Figure (a), the substrate is an Al2O3 dielectric layer with an Au backplate, and the particle size is... R core = 80 nm t s = 20 nm, the polarization direction of the incident photoelectric field is along x The shaft is surrounded by water; four distinct resonance absorption peaks A1 ( ) can be observed in Figure (b). λ =1.03 μm), A2 ( λ =1.48 μm), A3 ( λ =2 μm), A4 ( λ =2.34 μm), the absorption rate at A3 reaches 0.97, which is almost perfect absorption; Figure 8 In order to be in Figure 7Under the model scenario, the local electric field enhancement and magnetic response of the self-assembled structure are shown, including: (a) a schematic diagram of the positions of the upper horizontal arm (rose gold), central horizontal axis (purple), and lower horizontal arm (yellow) of the Al2O3 dielectric layer surface Z1 and the assembled structure; (b) the electric field distribution in the central plane; and (c) the orthographic projection of the current density in the XZ direction: the red arrows represent the current flowing through the particle surface, and the currents flowing through the upper horizontal arm, central horizontal axis, and lower horizontal arm of the structure are denoted as follows. I 1. I 2 and I 3. The white arrows indicate the current flowing through the Au backplate. (d) Magnetic field distribution in plane Z1. It can be observed that at the resonant wavelength of 2 μm, three pairs of antiparallel currents are formed between the upper horizontal arm, the central horizontal axis, and the lower horizontal arm and the Au backplate. These three pairs of antiparallel currents form counterclockwise closed loops with the displacement current in the Al2O3 dielectric layer, which are equivalent to three magnetic dipoles. Observing the magnetic field distribution in plane Z1, it can be seen that the magnetic field at the corresponding position is significantly enhanced. At the resonant wavelength of 2.34 μm, only the central horizontal axis forms a closed loop with the Au backplate, and the magnetic field at the corresponding position in plane Z1 is also significantly enhanced.

[0038] In summary, after the asymmetric self-assembled structure is transferred to the target substrate, the structure can generate a specific photoresponse with high sensitivity and quality factor based on the strong electromagnetic coupling between nanoparticles and between the particles and incident light. Furthermore, by flexibly adjusting the geometric parameters of the swastika-shaped asymmetric structure, it can be effectively adapted to the application needs of various scenarios such as biomedical imaging, high-sensitivity molecular detection, and even wearable sensing.

[0039] The above description only illustrates embodiments of the present invention, but should not be construed as covering the entire scope of protection of the present invention. Equivalent changes or modifications, or proportional enlargements or reductions made by the paradigm based on the design spirit of the present invention should all be considered to fall within the protection scope of the present invention.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. An asymmetric self-assembled structure of Fe3O4@Au nanoparticles, characterized in that, The self-assembled structure uses Fe3O4@Au nanoparticles as the basic building units to form a "卍" shape, and the self-assembled structure and its mirror image cannot coincide. The self-assembled structure is composed of two mutually orthogonal parts, and the two parts share a Fe3O4@Au nanoparticle. Each part includes two structural arms and a structural main axis. Both the structural arms and the structural main axis are composed of a number of Fe3O4@Au nanoparticles. The two structural arms are perpendicular to the structural main axis, forming a "right-angled Z" shape, and the two structural arms respectively share a Fe3O4@Au nanoparticle with the structural main axis.

2. The Fe3O4@Au nanoparticle asymmetric self-assembly structure according to claim 1, characterized in that, The Fe3O4@Au nanoparticles have a Fe3O4 core and a Au shell, and the diameter of the Fe3O4@Au nanoparticles is smaller than the wavelength of the incident light, where the incident light is the incident light during the light response test.

3. The asymmetric self-assembly structure of Fe3O4@Au nanoparticles according to claim 1, characterized in that, In the self-assembled structure, the distance between adjacent Fe3O4@Au nanoparticles is ≥ 2 nm.

4. The self-assembly method of the Fe3O4@Au nanoparticle asymmetric self-assembly structure according to any one of claims 1-3, characterized in that, It includes the following steps: In the first step, a silicon wafer is used as the bottom substrate. A "卍" - shaped soft magnetic body array is processed on the silicon wafer, and then a Au thin film with a preset thickness is plated around the "卍" - shaped soft magnetic body array to form a soft magnetic body mold. The material of the soft magnetic body array is permalloy. The thickness of the Au thin film is higher than the thickness of the "卍" - shaped soft magnetic body array. A groove with the same shape as the "卍" - shaped soft magnetic body and a depth equivalent to the diameter of the Fe3O4@Au nanoparticles is formed above the "卍" - shaped soft magnetic body array. In the second step, a microfluidic channel is loaded on the soft magnetic body mold. The microfluidic channel is a suspension of Fe3O4@Au nanoparticles. At the same time, a permanent magnet is used to provide an external bias magnetic field to guide the Fe3O4@Au nanoparticles to complete the assembly of the "卍" - shaped structure.

5. The self-assembly method for the Fe3O4@Au nanoparticle asymmetric self-assembly structure according to claim 4, characterized in that, In the second step, the velocity of the Fe3O4@Au nanoparticle suspension at the inlet of the microfluidic channel is set. v in = 1 mm / s.

6. The self-assembly method for the Fe3O4@Au nanoparticle asymmetric self-assembly structure according to claim 4, characterized in that, In the second step, the magnetic induction intensity of the external bias magnetic field... B bias =500 mT.

7. The self-assembly method for the Fe3O4@Au nanoparticle asymmetric self-assembly structure according to claim 4, characterized in that, The third step also includes increasing the speed of the Fe3O4@Au nanoparticle suspension after assembly. v in = 0.3 m / s, to remove stray particles deposited near the groove.

8. A photoresponsive composite tuning structure, based on the asymmetric self-assembly structure of Fe3O4@Au nanoparticles according to any one of claims 1-3, characterized in that, It includes a target substrate and a Fe3O4@Au nanoparticle asymmetric self-assembled structure provided on the target substrate.

9. The photoresponse composite tuning structure according to claim 8, characterized in that, The target substrate is glass, a metal backplane or a flexible film.

10. The photoresponse composite tuning structure according to claim 8, characterized in that, By controlling the type of the target substrate, the core or shell layer size of the Fe3O4@Au nanoparticles, the compactness of the Fe3O4@Au nanoparticles, the polarization direction of the external incident photoelectric field, and the surrounding medium environment, flexible regulation of the light response of the "卍" - shaped Fe3O4@Au nanoparticle asymmetric self-assembled structure is achieved.

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