Metal double-helix nanowire, preparation method thereof and circular polarization modulator

Abstract

The invention discloses a metal double-helix nanowire, a preparation method thereof and a circular polarization modulator, the preparation method comprises the following steps: stacking metal sheets on a template, and ballasting to obtain a complex, the template having double-helix nanopores; and the template in the complex is removed, and the metal double-helix nanowire is obtained on the metal sheet. According to the method, a metal confinement superplastic deformation means is adopted, the metal sheet is ballasted on the double-spiral-hole template, the single-crystal metal nanostructure is formed in the holes of the double-spiral-hole template, and compared with a traditional micro-nano machining technical scheme, operation is easy, the manufacturing cost is reduced, uniformity is good, functionality is high, and the method is suitable for large-scale production. And the method plays a very important role in improving the emission and transmission efficiency of the circular polarization signal. The metal double-helix nanowire prepared by the invention can realize circular polarization luminescence with an asymmetry factor greater than 0.5, and the circular polarization waveguide distance is 2 microns.

Description

Technical Field

[0001] The present invention relates to the technical field of circular polarization modulation devices, and particularly to a metal double-helical nanowire, a preparation method thereof, and a circular polarization modulation device. Background Art

[0002] A circular polarization modulator is a polarization optical device, and its core function is to precisely control the circular polarization state of an optical signal. It has broad application prospects in the fields of optical communication, polarization imaging, biomedical detection, quantum information processing, astronomy, and national defense security. However, traditional circular polarization modulators (such as those based on liquid crystals, electro-optic crystals, magneto-optic materials, or mechanical modulators) have significant limitations in terms of miniaturization, broadband performance, modulation rate, polarization purity, and multifunctional integration, and it is difficult to meet the requirements of emerging applications for high-performance optical devices.

[0003] In recent years, circular polarization modulators based on metamaterials have received extensive attention due to their miniaturization, broadband performance, and high flexibility. Metamaterials are artificially designed sub-wavelength structured materials that can achieve extraordinary optical properties, such as negative refractive index, superchiral field, and plasmon tuning, by regulating their geometric parameters and material compositions. Among them, plasmonic chiral metamaterials utilize the strong interaction between metal nanostructures and chiral light to generate chiral surface plasmon resonance, significantly enhancing the interaction between the local optical field and chiral substances, and thus showing unique advantages in circularly polarized luminescence, chiral molecule sensing, etc.

[0004] However, the commonly used preparation techniques for plasmonic chiral metamaterials at present (such as electron beam lithography, focused ion beam etching, 3D printing) have high costs, great preparation difficulties, low purity of the generated circularly polarized light, and cannot have the conduction performance of circularly polarized light, which greatly limits their integrated applications in optical systems. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention prepares metal double-helical nanowires by a supermolding deformation processing method with a double-helical nanopore template, in one step, on a large scale, and with high efficiency, and constructs them into circularly polarized luminescence and optical waveguide devices. It avoids the problems of high cost, complex operation, and poor design flexibility existing in conventional micro-nano processing methods such as electron beam and ion beam etching.

[0006] To achieve the above object, the present invention provides a preparation method of a metal double-helical nanowire, including: Stacking a metal sheet on a template and applying pressure to obtain a composite body, wherein the template has double-helical nanopores; Removing the template in the composite body to obtain metal double-helical nanowires on the metal sheet.

[0007] Further, the preparation method of the template includes dropping the gold particle dispersion liquid on the surface of the silicon substrate to form a gold dimer structure; immersing the silicon substrate with the gold dimer structure into an etching solution to etch and obtain the template.

[0008] Further, the concentration of the gold particle dispersion liquid is 0.02 - 0.1 mg / mL, and it is prepared from gold particles with a particle size of 60 - 100 nm, a chelating agent, and a solvent; The time for forming the gold dimer is 0.5 - 1.5 h.

[0009] The etching solution is formed by mixing hydrofluoric acid and hydrogen peroxide.

[0010] It should be noted that the types of the dispersion aid and the solvent in the gold particle dispersion liquid do not need to be strictly limited, nor does the concentration of the dispersion aid need to be strictly limited, as long as the gold particles can be evenly dispersed and grow to form a dimer structure on the surface of the silicon substrate. Exemplarily, the chelating agent can be at least one of sodium citrate, cetyltrimethylammonium bromide, polyvinylpyrrolidone, etc.; the solvent can be at least one of water, ethanol, N,N - dimethylformamide, etc.

[0011] Without special instructions, the concentrations of hydrofluoric acid and hydrogen peroxide in the etching solution are commercially available concentrations. Preferably, the concentration of hydrofluoric acid ≥ 40%, and the concentration of hydrogen peroxide ≥ 30%. The volume ratio does not need to be strictly limited. Preferably, the volume ratio of hydrofluoric acid to hydrogen peroxide in the etching solution is 6:4. The etching time in the etching solution is preferably 5 - 7 h.

[0012] Further, the ballasting lasts for 8 - 12 min at a temperature of 400 - 600 °C and a pressure of 260 - 340 MPa. The ballasting can be achieved by applying mechanical pressure, hot pressing, or vacuum - assisted ballasting.

[0013] The present invention has no limitation on the type of the metal sheet, which can be a single - element metal or an alloy, as long as the material of the metal sheet can meet the processing method of super - molding deformation. Exemplarily, it can be at least one of gold, silver, copper, aluminum, titanium, etc.

[0014] Further, the metal sheet is also polished before stacking.

[0015] Further, after obtaining the metal double - helix nanowires on the metal sheet, the metal double - helix nanowires are also peeled off from the metal sheet.

[0016] In the present invention, the template in the removal complex can be removed by methods such as chemical dissolution, mechanical peeling, or thermal decomposition.

[0017] Preferably, a chemical dissolution method is adopted to remove the silicon template in the composite. Specifically, the composite is immersed in an alkaline solution with a concentration of 2-4 mol / L at a temperature of 50-70 °C for 3-4 h.

[0018] The present invention also provides a metal double-helical nanowire obtained by the above preparation method.

[0019] Furthermore, the helical diameter of the metal double-helical nanowire is 10-500 nm, and the pitch is 50-1000 nm.

[0020] The present invention also provides a circular polarization modulation device, which includes the above metal double-helical nanowire and also includes a luminescent material.

[0021] The present invention does not strictly limit the type of the luminescent material. Exemplarily, the luminescent material can be selected from at least one of quantum dots, organic luminescent materials, rare earth luminescent materials, or fluorescent dyes. The preparation method of the circular polarization modulation device is not strictly limited either and is a conventional method in the art. Exemplarily, the metal double-helical nanowire and the luminescent material can be combined together by physical deposition, chemical bonding, coating, self-assembly, etc. to construct the device.

[0022] The present invention also provides the application of the above circular polarization modulation device in optical communication, polarization imaging, optical sensing, and optical encryption.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts the means of metal-confined superplastic deformation to press-load a metal sheet on a double-helical hole template, forming a single-crystalline metal nanostructure in the holes of the double-helical hole template. Compared with the traditional micro-nano processing technology solutions, the operation is simple, the manufacturing cost is reduced, the uniformity is good, the functionality is strong, and it plays a very important role in improving the emission and transmission efficiency of circular polarization signals.

[0024] The metal double-helical nanowire prepared by the present invention can achieve circularly polarized luminescence with an asymmetry factor greater than 0.5, and the circularly polarized optical waveguide distance is 2 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1The flowchart of the preparation method of the metal double - helix nanowire is shown, where the markings in the figure are: 1. silicon substrate; 2. gold nanoparticles; 3. silver sheet; 4. silver double - helix nanowire; Figure 2 The scanning electron microscope image of the double - helix nanopore template is shown; Figure 3 The low - magnification scanning electron microscope image of the silver double - helix nanowire is shown; Figure 4 The high - magnification scanning electron microscope image of the silver double - helix nanowire is shown; Figure 5 The scanning electron microscope images of the left - handed silver double - helix nanowire and the right - handed silver double - helix nanowire are shown; Figure 6a and Figure 6b respectively show the transmission electron microscope image and the electron diffraction pattern of the single - crystal characteristics of the silver double - helix nanowire; Figure 7a 、 Figure 7b and Figure 7c respectively show the circularly polarized fluorescence emission spectra of the right - handed and left - handed double - helix nanowires and the fluorescence luminescence asymmetry factor diagrams of the left - handed and right - handed double - helix nanowires; Figure 8a 、 Figure 8b and Figure 8c respectively show the right - hand circularly polarized scattering intensity, the left - hand circularly polarized scattering intensity and the scattering asymmetry factor diagram of the circular polarization modulation device; Figure 9 The scanning electron micrographs of the left - handed and right - handed double - helix structure optical waveguides are shown; Figure 10 The dark - field optical imaging diagrams of the left - handed and right - handed double - helix structure nanowires for left - hand circularly polarized and right - hand circularly polarized optical waveguides are shown; Figure 11 The test result diagram of the optical waveguide circular polarization response of the circular polarization modulation device is shown; Figure 12 The schematic diagram of the action of the circular polarization modulation device is shown. Detailed implementation mode

[0027] In the ranges disclosed in the present invention, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the accompanying drawings of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Embodiment 1 As Figure 1 shown, a preparation method of a metal double-helical nanowire includes the following steps: S101. Preparation of a double-helical nanopore template Using sodium citrate as a chelating agent, gold particles with a diameter of 80 nm are dispersed in water to prepare a gold particle dispersion with a concentration of 0.05 mg / mL; the gold particle dispersion is dropped on a silicon substrate and left for 1 h to form a gold dimer structure on the surface of the silicon substrate; Mix hydrofluoric acid with a concentration ≥ 40% and hydrogen peroxide with a concentration ≥ 30% in a volume ratio of 6:4 to obtain an etching solution; Immerse the silicon substrate with the gold dimer structure in the etching solution, take it out after 6 h, wash and dry to obtain a double-helical nanopore template.

[0030] S102. Preparation of silver double-helical nanowires Stack the polished silver sheet on the double-helical nanopore template, apply a pressure of 300 MPa at 500 °C, and hold for 10 min to obtain a composite; Immerse the composite in a potassium hydroxide solution with a concentration of 3 mol / L at 60 °C for 3 h to completely remove the silicon-based double-helical nanopore template, and obtain silver double-helical nanowires on the silver sheet.

[0031] S103. Preparation of a silver double-helical nanowire dispersion Place the silver sheet obtained in step S102 in absolute ethanol and ultrasonicate for 2 min to obtain a silver double-helical nanowire dispersion.

[0032] Embodiment 2 A preparation method of a circular polarization modulation device includes the following steps: T1. Drop and coat the silver double-helical nanowire dispersion prepared in Embodiment 1 on the surface of a silicon-based composite substrate. The bottom layer of the silicon-based composite substrate is silicon and the upper layer is SiO2 with a thickness of 400 nm. After waiting for 3 min, wash the surface with ultrapure water and blow dry with clean nitrogen.

[0033] T2. Immerse the product obtained in step T1 in a toluene solution of perylene with a concentration of 2 mmol / L and wait for 10 min, then take it out and dry to obtain a circular polarization modulation device.

[0034] Test Example The microscopic morphologies of the double-helical nanopore template and the silver double-helical nanowire prepared in Example 1 were observed by a scanning electron microscope. It can be seen from Figure 2 that with the assistance of gold particle etching, a double-helical pore structure was successfully obtained on the silicon substrate. It can be seen from Figure 3 and Figure 4 that the prepared silver double-helical nanowires have good morphologies, uniform sizes, and a large number of finished products. Figure 5 It shows that the prepared silver double-helical nanowires can be distinguished as belonging to the left-handed structure or the right-handed structure through scanning electron microscope characterization.

[0035] The morphology of the prepared silver double-helical nanowires was also observed by a transmission electron microscope. Figure 6a It further verifies that the silver double-helical nanowires have good morphologies and uniform sizes; Figure 6b The electron diffraction pattern of

[0036] shows that the silver double-helical nanowires have the characteristics of single crystals. Figure 7a - Figure 7c In the in-situ circularly polarized light emission performance test of the circular polarization modulation device prepared in Example 2, a linearly polarized laser beam with a wavelength of 457 nm was focused on the double-helical nanostructure, and the photoluminescence signal of perylene molecules was collected at the same position as the excitation light. It was found from Figure 7a - Figure 7c that the in-situ emission intensity of left-handed circularly polarized light is significantly stronger than that of right-handed circularly polarized light; when a linearly polarized laser beam with a wavelength of 457 nm was focused on the right-handed double-helical structure, and the photoluminescence signal of perylene molecules was collected at the same position as the excitation light, it was found that the in-situ emission intensity of right-handed circularly polarized light is significantly stronger than that of left-handed circularly polarized light. The luminescence asymmetry factors of the above two circularly polarized lights are ±0.5.

[0037] The chiral scattering performance of the circular polarization modulation device prepared in Example 2 was also tested. It can be seen from Figure 8a - 8c that the far-field radiation of the constructed circular polarization modulation device has excellent circular polarization responsiveness.

[0038] The optical circularly polarized light waveguide performance of the circular polarization modulation device prepared in Example 2 was also tested. It can be seen from Figure 9 and Figure 10 that the right-handed double-helical nanowires have an obvious selective enhancement for the conduction and radiation of right-handed circularly polarized light; the left-handed double-helical nanowires have an obvious selective enhancement for the conduction and radiation of left-handed circularly polarized light. It can be seen from Figure 11 the optical waveguide circular polarization response diagram of

[0039] These results demonstrate that the circular polarization modulation device constructed with silver double-helical nanowires according to the present invention can be used as a circularly polarized luminescence, circularly polarized optical waveguide, or optical antenna for the reception and transmission of circularly polarized light. Figure 12 The schematic diagram showing the function of the circular polarization modulation device according to the present invention is presented.

[0040] In summary, the present invention uses the method of metal-confined superplastic deformation to press-load a metal sheet on a double-helical pore template, forming a single-crystalline metal nanostructure within the pores of the double-helical pore template. Compared with traditional micro-nano processing technology solutions, it is simple to operate, reduces manufacturing costs, has good uniformity, and strong functionality. The metal double-helical nanowires prepared by the present invention can achieve circularly polarized luminescence with an asymmetry factor greater than 0.5, and the circularly polarized optical waveguide distance is 2 μm. The present invention provides a new idea for the functional integration of circularly polarized luminescence and circularly polarized waveguide devices.

[0041] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a metal double-helix nanowire, characterized in that: include, The metal sheets are stacked on the template and pressed to obtain a composite, wherein the template has a double-helical nanopore; The template in the complex is removed to obtain metal double-helix nanowires on the metal sheet.

2. The method for preparing a metal double-helix nanowire according to claim 1, characterized in that: The method for preparing the template comprises: Dropping dispersed gold particles onto the surface of a silicon substrate to form a gold dimer structure; The silicon substrate with the gold dimer structure is immersed in an etching solution and etched to obtain a template.

3. The method for preparing a metal double-helix nanowire according to claim 2, characterized in that: The gold particle dispersion has a concentration of 0.02-0.1 mg / mL and is prepared from gold particles with a particle size of 60-100 nm, a dispersing aid and a solvent; The time for forming the gold dimer is 0.5-1.5h; The etching solution is formed by mixing hydrofluoric acid and hydrogen peroxide.

4. The method for preparing a metal double-helix nanowire according to claim 1, characterized in that: The ballasting lasts for 8-12 minutes at a temperature of 400-600° C. and a pressure of 260-340 MPa.

5. The method for preparing a metal double-helix nanowire according to claim 1, characterized in that: The metal sheets are also polished before being stacked.

6. The method for preparing a metal double-helix nanowire according to claim 1, characterized in that: After obtaining the metal double helix nanowires on the metal sheet, the metal double helix nanowires are peeled off from the metal sheet.

7. A metal double helix nanowire, characterized in that: The preparation method is obtained by any one of claims 1 to 6.

8. The metal double helix nanowire according to claim 7, characterized in that: The spiral diameter is 10-500nm and the pitch is 50-1000nm.

9. A circular polarization modulation device, characterized in that: The metal double-helix nanowire according to claim 7 or 8 also includes a light-emitting material.

10. Application of the circular polarization modulation device according to claim 9 in optical communication, polarization imaging, optical sensing, and optical encryption.

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