Circularly polarized light-emitting device based on plasmon chiral nanometer cavity and preparation method of circularly polarized light-emitting device

Abstract

The invention provides a circularly polarized light-emitting device based on a plasmon chiral nanometer cavity and a preparation method thereof. The preparation method comprises the following steps: synthesizing chiral nanometer particles; taking a substrate, and depositing a metal film on the substrate; and depositing a luminescent material on the surface of the substrate and assembling the chiral nano-particles on the substrate, so that the luminescent material is assembled in nano gaps between the chiral nano-particles and the metal film to obtain the circularly polarized luminescent device. The quantum efficiency and the light emitting asymmetry are greatly improved, the resolution ratio is high, the controllability is high, and the method plays a very important role in promoting integration and application of circular polarization display devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of circularly polarized luminescence devices, and particularly relates to a circularly polarized luminescence device based on a plasmonic chiral nanocavity and a preparation method thereof. Background Art

[0002] Circularly Polarized Luminescence (CPL) refers to the polarized light emitted by a luminescent material after excitation, with the electric field vector rotating along the propagation direction. Due to its unique optical properties and chiral correlation, circularly polarized luminescence devices are of great significance in the fields of display technology, optical communication, biomedicine, anti-counterfeiting, environmental monitoring, basic research, etc. Plasmonic devices have advantages such as ultra-high local enhancement, high resolution, and ultrafast response. It is expected to prepare highly efficient circularly polarized luminescence devices with high quantum yield and optimal polarization degree based on this, greatly promoting the development of chiral nanomaterials and optoelectronics, such as the electron transition process and molecular asymmetry, and exploring the basis of the origin of life.

[0003] Common materials for circularly polarized luminescence devices are chiral conjugated polymers, supramolecular self-assembly, and liquid crystal materials. The main reason is that these substances usually have relatively high quantum yields or relatively strong circular polarization asymmetry, making them one of the ideal choices for traditional display devices. However, for on-chip optical integrated devices, it is required to simultaneously consider high quantum yield and strong circular polarization asymmetry. In addition, the resolution and preparation process should be compatible with the basic conditions and requirements of chip manufacturing. Therefore, these existing luminescent materials have some inherent shortcomings in terms of performance, greatly limiting their integration and commercialization.

[0004] Traditional circularly polarized luminescence devices usually rely on the performance of the luminescent material itself. First, the luminescence efficiency is limited by the quantum yield of the material. Second, the luminescence asymmetry of fluorescent molecules is usually on the order of 10 -3 ~10 -2 order of magnitude, far lower than the theoretical limit. In addition, the emission peak of the luminescent material has poor regulation performance. Therefore, it is necessary to develop a circularly polarized luminescence device that does not solely rely on the performance of the luminescent material itself and has a relatively high circularly polarized luminescence efficiency. Summary of the Invention

[0005] An object of the present invention is to provide a preparation method of a circularly polarized luminescence device based on a plasmonic chiral nanocavity for the deficiencies of the prior art, which can solve the problems of mutual exclusion between quantum efficiency and circular polarization asymmetry, low spatial resolution, poor controllability, and low luminescence efficiency in the prior art.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] Synthesize chiral nanoparticles;

[0008] Take a substrate and deposit a metal film on the substrate;

[0009] Deposit a luminescent material on the surface of the substrate with the metal film and assemble chiral nanoparticles on the substrate, so as to assemble the luminescent material in the nanogap between the chiral nanoparticles and the metal film to obtain a circularly polarized luminescence device.

[0010] Furthermore, depositing the metal film on the substrate further includes:

[0011] Determine the pattern on the circularly polarized luminescence device, cover the pattern on the substrate, then deposit the metal film on the substrate, and remove the cover to obtain a substrate with the pattern and the metal film.

[0012] Furthermore, different chiral nanoparticles are selected according to the polarization performance of the required circularly polarized luminescence device, and the chiral nanoparticles are selected from one or more of chiral gold nanoparticles, chiral silver nanoparticles, chiral oxide nanoparticles or chiral semiconductor nanoparticles.

[0013] Furthermore, the luminescent material is selected from one or more of fluorescent dyes, phosphorescent dyes and materials with photoluminescence properties including quantum dots and rare earth complexes.

[0014] Furthermore, the luminescent material is assembled on the surface of the substrate by means of self-assembly, spin coating, dipping or evaporation.

[0015] Furthermore, circularly polarized luminescence devices with different emission wavelengths are obtained by regulating the assembly time of the luminescent material at the interface.

[0016] Another object of the present invention is to provide a circularly polarized luminescence device obtained according to the preparation method of the circularly polarized luminescence device based on plasmonic chiral nanocavities as described above.

[0017] The present invention also provides an application of a circularly polarized luminescence device based on plasmonic chiral nanocavities, and the circularly polarized luminescence device is applied in display and lighting, encryption and anti-counterfeiting.

[0018] Furthermore, blue, green and red pixel points are obtained by regulating the assembly time of the luminescent material at the interface, and the prepared pixel points are used for high-definition display.

[0019] Furthermore, by engraving different patterns on the metal film of the substrate and then assembling the luminescent material and nanoparticles with different chirality on the patterns, a luminescence device with a pattern that can only be seen under a specific circular polarizer is obtained for information encryption and anti-counterfeiting.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: By means of interface-modified self-assembly, the chemically synthesized chiral nanoparticles are assembled on the patterned substrate adsorbed with the luminescent material. Compared with the traditional superstructure circularly polarized luminescence scheme, the operation is simple, the quantum efficiency and luminescence asymmetry are greatly improved, and the resolution is high, which plays a very important role in promoting the integration and application of circularly polarized display devices.

[0021] In addition, by using different chiral nanoparticles in the present invention, components with different chiral luminescence polarization properties can be obtained. Moreover, by regulating the assembly time of the luminescent material at the interface, components with different emission wavelengths can be obtained. It has strong controllability, expands the application of components, and is simple to prepare. In addition, the present invention can be completed in an air environment, which greatly simplifies the preparation conditions and reduces the cost.

[0022] The structure provided by the present invention can not only achieve relatively high circularly polarized asymmetric luminescence, with the asymmetry factor being greater than 1.0, but also achieve relatively high circularly polarized luminescence efficiency, with the quantum efficiency reaching 45%. It provides new possibilities for circularly polarized light sources and their integrated applications, such as ultra-high-definition circularly polarized displays, on-chip integrated circularly polarized light sources, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flowchart for the preparation of the circularly polarized luminescence device provided in Embodiment 1 of the present invention;

[0024] Figure 2 It is the circularly polarized luminescence imaging of the blue pixel points prepared in Embodiment 1 of the present invention;

[0025] Figure 3 It is the circularly polarized luminescence imaging of the green pixel points prepared in Embodiment 1 of the present invention;

[0026] Figure 4 It is the circularly polarized luminescence imaging of the red pixel points prepared in Embodiment 1 of the present invention;

[0027] Figure 5 It is the chiral photoluminescence test result diagram provided in Embodiment 1 of the present invention. Among them, (a) is the fluorescence spectrum of the photoluminescence of excimer 1 assembled in the left-handed chiral nanocavity, (b) is the fluorescence spectrum of the photoluminescence of excimer 1 assembled in the right-handed chiral nanocavity, and (c) is the asymmetry factor of the circularly polarized luminescence of excimer 1 in the chiral nanocavity;

[0028] Figure 6Photoluminescence test result diagram provided by Embodiment 1 of the present invention. Among them, (a) fluorescence spectrum of excimer 2 assembled in the left-handed nanocavity for photoluminescence, (b) fluorescence spectrum of excimer 2 assembled in the right-handed nanocavity for photoluminescence, and (c) asymmetry factor of circularly polarized luminescence of excimer 2 in the chiral nanocavity;

[0029] Figure 7 Dark-field microscopy image of the photoluminescence of the luminescent material assembled in the chiral nanocavity provided by Embodiment 1 of the present invention. Among them, (a) perylene monolayer (475 nm emission peak), (b) excimer 1 (550 nm emission peak), (c) excimer 2 (640 nm emission peak);

[0030] Figure 8 Flow chart for the preparation of circularly polarized luminescence components in the shapes of letters "C", "P", and "L" based on racemic, left-handed, and right-handed nanoparticles respectively provided by Embodiment 2 of the present invention. Among them, 1. Gold target; 2. Silicon substrate; 3. Gold film; 4. Nanoparticles;

[0031] Figure 9 Scanning electron microscope images of the chiral gold nanoparticle enantiomers provided by Embodiment 2 of the present invention. Among them, (a) is the left-handed particle, and (b) is the right-handed particle;

[0032] Figure 10 Circular dichroism scattering spectrum of the chiral gold nanoparticles on the gold substrate provided by Embodiment 2 of the present invention;

[0033] Figure 11 Transmission electron microscope pictures and high-resolution images of the chiral nanoparticles provided by Embodiment 2 of the present invention. (a) and (b) are left-handed particles, and (c) and (d) are right-handed particles;

[0034] Figure 12 Statistical distribution diagram of the scattering asymmetry factor of the chiral gold nanoparticles provided by Embodiment 2 of the present invention;

[0035] Figure 13 Dark-field microscope image of the patterned "C, P, L" type gold substrate provided by Embodiment 2 of the present invention;

[0036] Figure 14 Fluorescence image of the circularly polarized luminescence device under the excitation of linearly polarized light with a wavelength of 446 nm provided by Embodiment 2 of the present invention. Among them, (a) without a circular polarizer (natural light), (b) left-handed circular polarizer (left-handed light), (c) right-handed circular polarizer (right-handed light). Detailed implementation manners

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with 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. 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.

[0038] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0039] The present invention will be further described below in conjunction with specific embodiments, but it is not limited to the present invention.

[0040] The embodiment of the present invention provides a preparation method for a circularly polarized luminescence device based on a plasmonic chiral nanocavity, including the following steps:

[0041] 101: Chiral nanoparticles synthesized by a wet chemical method.

[0042] Among them, the synthesis conditions in step 101 include: mixing 4.25 mL of water, 100 μL of 8 mM - 12 mM chloroauric acid, and 120 μL of 0.10 M ascorbic acid AA evenly, then adding 10 μL of 0.1 mM L- / D-cysteine solution, and standing in a water bath at 30 °C for 1 h - 3 h. Centrifuge all the synthesized chiral nanoparticles with sharp-corner features at a rotation speed of 3000 rpm - 4000 rpm for 5 minutes to separate the unreacted reagents, and obtain the required chiral nanoparticles. In addition to the L- / D-cysteine solution, other chiral compounds can also be selected as the chiral compound.

[0043] 102: Prepare a patterned gold film on a substrate by masking.

[0044] Among them, the preparation of the patterned gold substrate in step 102 includes the following steps: First, mask a clean substrate silicon wafer with tape, and the tape is engraved with a designed pattern. Then deposit a metal film with a thickness of 50 nm - 200 nm on the substrate by thermal evaporation or other methods, and then peel off the tape to expose the pattern on the substrate.

[0045] Of course, a metal film can also be directly deposited on the substrate without designing a pattern.

[0046] 103: Assemble the luminescent material in the nano-gap between the chiral nanoparticles and the metal substrate to prepare a circularly polarized luminescence device.

[0047] In this step, the luminescent material can be one or more of fluorescent dyes, phosphorescent dyes, quantum dots, rare earth complexes and other materials with photoluminescence properties. Then, the luminescent material is assembled on the surface of the substrate by means of self-assembly, spin coating, dipping or evaporation. If the dipping method is adopted, the substrate is immersed in a toluene solution containing 0.1 mM to 0.3 mM perylene molecules for 0.08 h to 14 h, and then dried with an air gun. Then, the colloidal solution containing chiral nanoparticles is dropped on the substrate and left for 6 min to 10 min, and the particles are uniformly assembled on the surface of the substrate.

[0048] For perylene molecules, they can randomly diffuse in the solution through Brownian motion. The ground-state molecules and the excited-state molecules generate π-π interactions and approach in a parallel or partially overlapping configuration to form an excimer. Therefore, different phases of excimers can be generated by adjusting the assembly time. Not only can an excimer with an emission wavelength of 550 nm (excimer 1) be obtained, but also an excimer with an emission wavelength of 640 nm (excimer 2) can be obtained.

[0049] For example, as an illustration, when the concentration of perylene molecules in toluene is low, the self-assembled excimer has an emission peak at 550 nm (see Example 1).

[0050] For another example, as an illustration, when the concentration of perylene molecules in toluene is high, the self-assembled excimer has an emission peak at 640 nm (see Example 1).

[0051] Example 1

[0052] See Figure 1 As shown, this example provides a preparation method of a circularly polarized luminescence device based on a plasmonic left-handed chiral nanocavity, which can be used as red, green, and blue sub-pixel dots. The specific steps are as follows:

[0053] 1) Chemical preparation of chiral nanoparticles

[0054] First, 4.25 mL of water, 100 μL of 10 mM chloroauric acid, and 120 μL of 0.10 M AA are mixed evenly, and then 10 μL of 0.1 mM L- / D-cysteine solution is added. The mixture is left standing in a water bath at 30 °C for 2 h. All the synthesized chiral nanoparticles with sharp-corner features are centrifuged at 3500 rpm for 5 minutes to separate the unreacted reagents.

[0055] 2) Deposit a 100-nm-thick metal film on the substrate by means of thermal evaporation or the like to obtain the required substrate for standby;

[0056] 3) Assemble the luminescent material in the nano-gap between the chiral nanoparticles and the metal substrate, and obtain circularly polarized luminescence devices with different emission wavelengths by regulating the assembly time of the luminescent material at the interface. The specific regulation methods include:

[0057] a) Assemble a monolayer of perylene with an emission wavelength of 475 nm in the nanogap between left-handed nanoparticles and a metal substrate to prepare blue sub-pixel dots.

[0058] First, immerse the substrate prepared in step 2) above in a toluene solution containing 0.2 mM perylene molecules for 5 minutes, then blow dry with an air gun, deposit left-handed nanoparticles on the substrate by drop casting, and finally perform circularly polarized luminescence testing. The test results are as Figure 2 shown. According to Figure 2 it can be seen that the blue pixel dots have high brightness and good clarity.

[0059] b) Assemble excimer 1 with an emission wavelength of 550 nm in the nanogap between left-handed nanoparticles and a metal substrate to prepare green sub-pixel dots.

[0060] Immerse another substrate prepared in step 2) above in a toluene solution containing 0.2 mM perylene molecules for 5 hours, then blow dry with an air gun, deposit left-handed nanoparticles on the substrate by drop casting, and finally perform circularly polarized luminescence testing. The test results are as Figure 3 shown. From Figure 3 it can be known that the green sub-pixel dots based on left-handed particles are more sensitive to the response of the left-handed circular polarizer.

[0061] c) Assemble excimer 2 with an emission wavelength of 640 nm in the nanogap between left-handed nanoparticles and a metal substrate to prepare red sub-pixel dots.

[0062] Take another substrate prepared in step 2) above and immerse it in a toluene solution containing 0.2 mM perylene molecules for 14 hours, then blow dry with an air gun, deposit left-handed nanoparticles on the substrate by drop casting, and finally perform circularly polarized luminescence testing. The test results are as Figure 4 shown. From Figure 4 it can be known that the emission of the red sub-pixel dots has a strong chiral response and can be used for circular polarization display.

[0063] Finally, perform chiral photoluminescence testing on the above excimers respectively. The test results are shown in Figure 5 and 6 . Focus a linearly polarized laser beam of 457 nm on the structure of chiral nanoparticles. As Figure 5 shown, the fluorescence spectrum shows that excimer 1 has strong fluorescence intensity and a stable and controllable chiral response. See Figure 6 shown. The fluorescence spectrum shows that the emission peak of excimer 2 is at 640 nm, and compared with excimer 1 with an emission peak of 550 nm, it has stronger circular polarization characteristics.

[0064] In summary, it can be seen that excimers with more diverse wavelength distributions can be obtained by the assembly time of the luminescent material at the interface, enabling further applications in the directions of dynamic regulation of circularly polarized luminescence, molecular sensing, ultra-high-definition full-color display, etc. The above method can be used to prepare the required blue, green, and red pixel dots. As Figure 7 shown, the marked "1", "2", and "3" represent "blue", "green", and "red" pixel dots respectively. The pixel dots have high brightness and good clarity. The pixel dots prepared by the above method are suitable for high-definition display. At the same time, the circularly polarized luminescence device prepared above indicates that this structure has taken an important step towards an integrated display device.

[0065] Example 2

[0066] See Figure 8 shown. This example provides a preparation method for a circularly polarized emission device based on a plasmonic chiral nanocavity, which can be applied to encryption and anti-counterfeiting. The specific steps are as follows:

[0067] 1) Chemical preparation of chiral nanoparticles

[0068] First, mix 4.25 mL of water, 100 μL of 10 mM chloroauric acid, and 120 μL of 0.10 M AA evenly, and then add 10 μL of 0.1 mM L- / D-cysteine solution. Let it stand in a water bath at 30 °C for 2 h. Centrifuge all the synthesized chiral nanoparticles with sharp-corner features at 3500 rpm for 5 minutes to separate the unreacted reagents.

[0069] Then see Figure 9 shown. Drop the prepared chiral nanoparticles on the Au substrate. The scanning electron microscope pictures show that the synthesized chiral nanoparticles have obvious chiral features. See Figure 10 shown. The circular dichroism scattering spectrum shows that the far-field scattering of the chiral nanoparticles has a circular polarization response. Then see Figure 11 shown. The synthesized chiral nanoparticles have the characteristics of good single crystals. From the statistical results, Figure 12 in, the circular polarization scattering characteristics of the chiral nanoparticles are relatively stable and suitable for application in luminescent devices.

[0070] 2) Preparation of a patterned gold film with a mask on the substrate

[0071] See Figure 8 , first, take three clean silicon wafers, and mask the clean silicon wafers with tape respectively. Three capital letters "C", "P", and "L" are engraved on the three tapes respectively. Then deposit a 100-nm-thick gold film on the substrate by thermal evaporation, and then peel off the tape to expose the golden letters on the substrate. Among them, the substrates with the "C", "P", and "L" patterns prepared are shown in Figure 13 shown.

[0072] 3) Assemble the excimer of perylene molecules in the nanogap between chiral nanoparticles and a metal substrate to fabricate a circularly polarized luminescence device:

[0073] First, immerse the three patterned substrates (“C”, “P”, and “L”) in a toluene solution of perylene molecules with a concentration of 0.2 mM for 5 minutes, 5 hours, and 14 hours respectively, then dry them with an air gun, and place them in a vacuum temperature control box. At 90 °C and a vacuum of 10 -7 bar, hydrophobize the silicon substrate with siloxane for 1.5 h. Finally, deposit racemic, left-handed, and right-handed nanoparticles on the patterns “C”, “P”, and “L” of the substrate by drop casting method.

[0074] Finally, perform patterning tests on the three fabricated luminescence devices under the excitation of linearly polarized light with a wavelength of 446 nm, and obtain the results as Figure 14 shown. It can be seen from Figure 14 that the fluorescence emission of circularly polarized luminescence devices with different chiral structures has obvious left- and right-handed asymmetry. Combine these three luminescence devices together, and the information of “CPL” can be obtained when observed under natural light, the information of “CP” can be obtained when observed under a left-handed circular polarizer, and the information of “CL” can be obtained when observed under a right-handed circular polarizer under the same conditions. Such patterns or texts that can only be seen when observed under a specific circular polarizer can be used for information encryption and anti-counterfeiting.

[0075] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all equivalent replacements and obvious changes made by using the content of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a circularly polarized luminescence device based on a plasmonic chiral nanocavity, characterized in that, Comprising the following steps: Synthesizing chiral nanoparticles; Taking a substrate and depositing a metal film on the substrate; Depositing a luminescent material on the surface of the substrate with the metal film and assembling the chiral nanoparticles on the substrate, so as to assemble the luminescent material in the nano-gap between the chiral nanoparticles and the metal film to obtain a circularly polarized luminescence device.

2. The preparation method of the circularly polarized luminescence device based on the plasmonic chiral nanocavity according to claim 1, wherein, Depositing the metal film on the substrate further includes: Determining the pattern on the circularly polarized luminescence device, covering the pattern on the substrate, then depositing the metal film on the substrate, and removing the covering to obtain a substrate with the pattern and the metal film.

3. The preparation method of the circularly polarized luminescence device based on the plasmonic chiral nanocavity according to claim 1, wherein, Selecting different chiral nanoparticles according to the polarization performance of the required circularly polarized luminescence device, and the chiral nanoparticles are selected from one or more of chiral gold nanoparticles, chiral silver nanoparticles, chiral oxide nanoparticles or chiral semiconductor nanoparticles.

4. The preparation method of the circularly polarized luminescence device based on the plasmonic chiral nanocavity according to claim 1, wherein, The luminescent material is selected from one or more of fluorescent dyes, phosphorescent dyes and materials with photoluminescence properties including quantum dots and rare earth complexes.

5. The preparation method of the circularly polarized luminescence device based on the plasmonic chiral nanocavity according to claim 1, wherein, The luminescent material is assembled on the surface of the substrate by means of self-assembly, spin coating, dipping or evaporation.

6. The preparation method of the circularly polarized luminescence device based on the plasmonic chiral nanocavity according to claim 1, wherein, Circularly polarized luminescence devices with different emission wavelengths are obtained by regulating the assembly time of the luminescent material at the interface.

7. A circularly polarized luminescence device obtained by the preparation method of the circularly polarized luminescence device based on a plasmonic chiral nano-cavity according to any one of claims 1-6.

8. An application of the circularly polarized luminescence device based on the plasmonic chiral nanocavity according to claim 7, characterized in that, Applying the circularly polarized luminescence device in display and lighting, encryption and anti-counterfeiting.

9. The application of the circularly polarized luminescence device based on the plasmonic chiral nanocavity according to claim 8, characterized in that, Blue, green and red pixel points are obtained by regulating the assembly time of the luminescent material at the interface, and the prepared pixel points are used for high-definition display.

10. The application of the circularly polarized luminescence device based on the plasmonic chiral nanocavity according to claim 8, wherein By engraving different patterns on the metal film of the substrate and then assembling the luminescent material and nanoparticles with different chirality on the patterns, a luminescence device with a pattern that can only be seen under a specific circular polarizer is obtained for information encryption and anti-counterfeiting.

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