Rh800 dye molecule multi-angle photoluminescence enhancement method based on plasmon metal grating resonance

Abstract

The invention discloses an Rh800 dye molecule multi-angle photoluminescence enhancement method based on plasmon metal grating resonance, and relates to the technical field of plasmon optics, and the method comprises the following steps: S1, obtaining a metal grating structure capable of coupling surface plasmon; s2, preparing an Rh800-polymer PMMA (polymethyl methacrylate) solution, spin-coating the solution on the surface of the metal grating structure, and drying; s3, adjusting the incident angle and the incident polarization of the exciting light and selecting the excitation wavelength for enhancing the excitation process of the dye; s4, obtaining a multi-angle luminescence response curve; s5, optimizing and obtaining stable enhanced photoluminescence output under a plurality of incidence and collection angles; by accurately controlling sample preparation parameters and test conditions, efficient enhancement of Rh800 dye molecule photoluminescence is achieved, the enhancement multiple reaches 22-22.6 times during resonance matching and still reaches 14 times in a non-resonance state, the sample has the narrow-angle emission characteristic, and reproducible experimental basis is provided for large-scale preparation and application of related optical devices.

Description

Technical Field

[0001] This invention relates to the field of plasmonic optics technology, specifically to a method for enhancing the multi-angle photoluminescence of Rh800 dye molecules based on plasmonic metal grating resonance. Background Technology

[0002] In recent years, enhancing the photoluminescence (PL) effect of organic dye molecules has attracted widespread attention in optoelectronic devices, sensing, and imaging. Specifically, Rh800 dye molecules have garnered significant interest due to their unique optical properties and high luminescence efficiency. Enhancing photoluminescence not only has the potential to improve the performance of these materials in practical applications but also provides insights into the fundamental mechanisms of light-matter interactions. Recent studies have shown that various methods and structures can significantly enhance the photoluminescence effect of Rh800 dye molecules. Enhanced photoluminescence has been extensively researched, with numerous methods proposed and investigated. For example, structures such as nanoparticles, microcavities, and photonic crystals have been used to improve the luminescence efficiency of dye molecules. While these methods can indeed amplify the photoluminescence effect to some extent, they also suffer from drawbacks such as complex fabrication processes, high costs, and limited enhancement effects. Therefore, finding a simple, efficient, and controllable method to enhance the photoluminescence of Rh800 dye molecules has become an increasingly important issue.

[0003] Metal gratings are considered an ideal structure for enhancing photoluminescence due to their unique surface plasmon resonance effect. Metal gratings can generate a strong local electric field on their surface, significantly enhancing the photoluminescence efficiency of dye molecules. Furthermore, the design and parameters of the metal grating can be precisely controlled to match the excitation wavelength of the dye molecules with the surface plasmon resonance mode, thereby achieving optimal enhancement. Compared with other complex enhancement structures, metal gratings have advantages such as simple fabrication, low cost, and ease of large-scale production. High-quality metal gratings can be easily fabricated using holographic grating technology, offering potential for large-scale applications. Currently, research on enhancing the photoluminescence effect of Rh800 dye molecules using metal gratings at different angles is limited. However, studying from different angles is crucial for fully understanding the enhancement mechanism and practical applications of metal gratings. By adjusting the grating angle, the photoluminescence enhancement effect can be further optimized to meet the requirements of different application scenarios.

[0004] To address this issue, this application proposes a multi-angle photoluminescence enhancement method for Rh800 dye molecules based on plasmon resonance, in order to solve the aforementioned problems. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-angle photoluminescence enhancement method for Rh800 dye molecules based on plasmonic metal grating resonance, in order to solve the problems of complex preparation, high cost and limited enhancement effect of existing technologies for enhancing the photoluminescence of Rh800 dyes with nanoparticles, microcavities and other structures, and insufficient research on enhancing the photoluminescence of the dye with metal gratings at different angles, which makes it difficult to meet the needs of diverse application scenarios.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for enhancing the photoluminescence of Rh800 dye molecules from multiple angles based on plasmon resonance includes the following steps:

[0008] S1. A periodic photoresist grating is formed on a substrate and a silver film is thermally deposited on the surface of the grating to obtain a metal grating structure that can couple surface plasmons.

[0009] S2. Prepare a Rh800-polymer PMMA solution and spin-coat the solution onto the surface of the metal grating structure and dry it to form a uniform dye organic film;

[0010] S3. Adjust the incident angle and incident polarization of the excitation light and select the excitation wavelength so that the plasmon resonance mode of the metal grating partially overlaps with the excitation / emission spectrum of the dye organic film to obtain a resonance-matched excitation system, which is used to enhance the excitation process of the dye.

[0011] S4. Perform angle-resolved excitation-collection photoluminescence measurement on the resonant matched excitation system and record the distribution of luminescence intensity with incident angle, collection angle and polarization to obtain multi-angle luminescence response curves;

[0012] S5. Based on the multi-angle emission response curve, adjust the grating period, grating depth, metal film thickness or coating thickness, and repeat steps S3 to S4 to optimize and obtain photoluminescence output that exhibits stable enhancement under multiple incident and collection angles.

[0013] Furthermore, the grating period is 500–580 nm and the depth is 8–25 nm.

[0014] Furthermore, the thickness of the silver film is 100–200 nm.

[0015] Furthermore, the concentration of Rh800 is 1–3 mg·mL. -1 The PMMA mass fraction is 1-5 wt%, and the spin coating speed is 2000-5000 rpm.

[0016] Furthermore, the excitation wavelength is selected from 600 to 640 nm, and the dye emission peak is located in the range of 710 to 730 nm; the measurement scanning incident angle range is -12° to +12°, the angular resolution is 0.1° to 1°, and the mode adopts TM polarization.

[0017] Furthermore, the photoluminescence enhancement factor is obtained by comparing the peak luminescence intensity of the metal grating / dye sample with the peak luminescence intensity of the corresponding dye film on the planar silver film under the same excitation conditions.

[0018] Furthermore, steps S3 to S5 can be repeated at least twice to verify the enhanced stability and repeatability, and in each cycle, the grating period, metal film thickness, or coating thickness can be finely adjusted within a range of ±15% to obtain the optimal multi-angle enhancement effect.

[0019] Compared with existing technologies, the multi-angle photoluminescence enhancement method for Rh800 dye molecules based on plasmon resonance provided by this invention achieves highly efficient enhancement of Rh800 dye molecule photoluminescence by precisely controlling sample preparation parameters and testing conditions: the enhancement factor reaches 22-22.6 times under resonance matching and still reaches 14 times under non-resonance conditions, and the sample exhibits narrow-angle emission characteristics and good reproducibility. This embodiment verifies the photoluminescence modulation capability of plasmon resonance grating structures under multiple angles and polarization states, providing reproducible experimental evidence for the large-scale fabrication and application of related optical devices. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0021] Figure 1 A 3D structural schematic diagram and a 2D cross-sectional schematic diagram of the silver grating combined with Rh800 dye molecules provided for embodiments of the present invention: (a) 3D structural schematic diagram of the silver grating combined with Rh800 dye molecules; (b) 2D cross-sectional schematic diagram of the composite structure (from top to bottom: PMMA (Rh800) layer, Ag grating layer, photoresist layer (PR), silicon substrate (Substrate (Si))).

[0022] Figure 2The simulated and experimental reflectance spectra (including the electric field distribution at the 714 nm resonant wavelength) of the 540 nm periodic grating structure under normal incidence of TM polarized light provided for embodiments of the present invention, as well as the top view and cross-sectional view of the prepared structure by atomic force microscopy (AFM), (a) simulated and experimental reflectance spectra of the 540 nm periodic grating structure under normal incidence of TM polarized light (distribution of the transverse electric field |E| at the resonant wavelength of 714 nm); (b)-(c) AFM images of the prepared sample;

[0023] Figure 3 The following diagrams are provided for embodiments of the present invention: a schematic diagram of the test geometry for plasmonic metal grating emission collection, a diagram of the luminescence measurement experimental setup, a vertical photoluminescence (PL) spectrum at a 40° incident angle (including insets of resonant / non-resonant reflection spectra), and an angle-resolved PL intensity distribution under resonant conditions. (a) Test geometry for oblique incidence-vertical collection mode (IL: incident light; CL: collected light; RL: reflected light; DL: diffracted light); (b) Schematic diagram of the angle-resolved spectral testing experimental setup; (c) Vertical PL spectrum at a 40° incident angle (insets show reflection spectra in resonant / non-resonant states); (d) Angle-resolved PL intensity distribution under resonant conditions (incident angle 40°, collection angle -12° to 12°).

[0024] Figure 4 A schematic diagram of the test geometry for collecting photoluminescence at -40° normal incidence provided in an embodiment of the present invention, and a comparison diagram of the PL spectra of different polarization states of this test mode under resonance conditions. (a) Schematic diagram of photoluminescence collected at 40° under normal incidence conditions. (b) Photoluminescence spectrum collected at 40° normal incidence under resonance conditions. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0026] As attached Figure 1 To be continued Figure 4 As shown:

[0027] Example 1:

[0028] A multi-angle photoluminescence enhancement method for Rh800 dye molecules based on plasmonic metal grating resonance includes:

[0029] I. Materials and Equipment

[0030] Monocrystalline silicon wafers (silicon substrate), acetone, ethanol, deionized water;

[0031] Photoresist (for interference / holographic lithography); helium-cadmium laser (λ = 325 nm) exposure equipment; developing solution;

[0032] Thermal evaporation coating machine (silver target); electronic balance, ultrasonic cleaner; spin coater; constant temperature drying oven; AFM (atomic force microscope); scanning electron microscope (SEM); spectral measurement system (He–Ne laser IL, λ = 632.8 nm; half-wave plate and polarizer; angular resolution rotating stage, angular resolution 0.5°; fiber-coupled spectrometer). (See experimental platform and measurement configuration description).

[0033] II. Preparation Steps

[0034] S1 Cleaning the substrate: The silicon wafer is ultrasonically cleaned in acetone, ethanol and deionized water for 15 min each, and then dried with nitrogen gas for later use.

[0035] S2 Photolithography Grating Fabrication: Photoresist is spin-coated on a silicon wafer (4000 rpm, film thickness approximately 120 nm), and interference holographic exposure is performed (HeCd laser, λ = 325 nm, exposure approximately 30 s). Development is performed for 4–10 s to obtain a periodic photoresist grating (period is taken as the design value of 540 nm, ridge width approximately 270 nm).

[0036] S3 Metal Grating Formation: Silver is deposited on the photoresist grating by thermal evaporation, with a silver film thickness of approximately 150 nm. Figure 1 As shown, an Ag metal grating structure was obtained (shallow grating depth d ≈ 10–20 nm, sidewall tilt angle approximately 25°, surface roughness < 0.5 nm). AFM / SEM characterization confirmed the grating period and morphology.

[0037] S4 Dye Organic Film Preparation and Coating: Preparation of PMMA (Rh800) Solution: Weigh 6 mg of Rh800, add 3 mL of PMMA solvent system, sonicate for 1 h, to obtain Rh800 concentration ≈ 2 mg·mL -1 (PMMA mass fraction 1–5 wt% optional). Spin-coat the solution onto the Ag grating surface (3500 rpm), allow to air dry at room temperature to form a uniform organic film (thickness controlled by spin-coating speed and solvent concentration). S5 Excitation-Angle-Resolved PL Measurement: Mount the sample on an angle-resolved stage, using a He–Ne laser (λ = 632.8 nm) as the excitation source; two experimental modes are available:

[0038] Mode A (Oblique Incidence - Vertical Collection): Fixed incident angle of 40° (for exciting plasmon resonance), collection and emission along the normal (collection angle of 0°); scan incident polarization (TM / TE) and record PL spectrum.

[0039] Mode B (Angle-Resolved Collection): With fixed or oblique incident excitation (e.g., 40°), the collection angle is varied from −12° to +12° (angular resolution 0.5°) to record the PL intensity distribution, obtaining multi-angle emission response curves. The two modes complement each other, revealing the effects of angle and polarization on PL enhancement. S6 Parameter Optimization and Repeatability Validation: Based on the angle-resolved PL response, fine-tune the grating period (±15%), grating depth (10–25 nm), silver film thickness (100–200 nm), or coating thickness as needed, and repeat cycles S4–S5 at least twice to confirm enhancement stability and repeatability.

[0040] III. Test Platform Setup

[0041] An angle-resolved spectroscopy testing platform was constructed, and interference from reflection and diffraction signals was avoided by spatially separating the excitation and collection optical paths. The specific configuration is as follows:

[0042] The excitation source uses a helium-neon laser (λ=632.8nm), which can achieve two incident angles of 0° (vertical) or 40° (oblique incidence);

[0043] A half-wave plate is configured to adjust the polarization state of the incident light (TM polarization / TE polarization).

[0044] The collection system uses a fiber-coupled spectrometer, paired with a control rotary stage, which can achieve precise angular resolution scanning (0.5° angular resolution) in the range of -12° to +12°.

[0045] Two test geometries were constructed: ① oblique incidence - perpendicular collection (incident angle 40°, collection angle 0°); ② perpendicular incidence - oblique collection (incident angle 0°, collection angle 40°), as follows. Figure 3 (a) As shown in Figure 4(a).

[0046] IV. Experimental Testing and Result Analysis

[0047] (I) Sample structure characterization

[0048] like Figure 2 As shown, the composite sample was characterized by AFM. Figure 2(b) is a top AFM image of the sample, showing a grating period of p=540nm, a ridge width of about w=270nm, and a surface roughness of less than 0.5nm, confirming that the fabrication process has good uniformity. Figure 2(c) is a cross-sectional AFM image of the sample, showing a grating depth of d≈10nm and a sidewall tilt angle of about 25°, indicating slight etching anisotropy.

[0049] (II) Simulation and Verification of Resonance Characteristics

[0050] The resonance characteristics of the metal grating were simulated using the FDTD method, and the results were compared with the experimentally measured reflection spectra. Figure 2(a) shows that the experimental reflection spectrum resonance position of the pure metal grating (Ag Gra.) and the silver grating-PMMA (Rh800) composite structure (Ag Gra-PMMA) is highly consistent with the theoretical simulation results, with a resonance wavelength of 714 nm. At this wavelength, the electric field maxima are concentrated on the upper surface of the PMMA layer at the air interface and the top region of the silver grating ridge, forming a weakly coupled hybrid state of the PMMA-air interface waveguide mode and the surface plasmon (SP) mode.

[0051] (III) Oblique Incidence - Vertical Collection Mode Test

[0052] like Figure 3 As shown in Figure 3(c), with the incident angle set to 40° and the collection angle to 0°, the vertical PL spectra of different structures (Si / PMMA substrate, Si / Ag thin film / PMMA, Si / Ag grating / PMMA) were tested, and the results are shown in Figure 3(c).

[0053] The Si / PMMA substrate has the lowest PL strength (≈1814 au).

[0054] The PL strength of the Si / Ag thin film / PMMA structure is increased to approximately 9241 au (a 5-fold increase).

[0055] The Si / Ag grating / PMMA structure achieves a peak PL of approximately 40,000 au (22 times stronger than the Si / PMMA substrate) during resonant matching, and still reaches approximately 25,444 au (14 times stronger) in the non-resonant state.

[0056] Angle-resolved PL intensity tests were performed under resonance conditions (collection angle -12° to +12°), and the results are shown in Figure 3(d). The sample exhibits narrow-angle emission characteristics (FWHM≈8°), with the emission center located in the normal direction (0°). The intensity on the negative angle side (incident light direction) is slightly higher than that on the positive angle side, and a weak diffraction tail peak appears only at +10°, confirming the precise control capability of the grating structure on the emission directionality.

[0057] (iv) Vertical incidence - oblique collection mode test

[0058] like Figure 4 As shown in Figure 4(b), with the incident angle set to 0° and the collection angle to 40°, the polarization state of the incident light was adjusted, and the PL spectra of different structures were tested.

[0059] The PL emission peaks of all structures are concentrated in the 710-730nm band, which coincides with the characteristic emission peaks of the Rh800 dye;

[0060] When TM polarized light is incident, the peak PL of the Si / Ag grating / PMMA structure reaches approximately 43,000 au (22.6 times stronger than the Si / PMMA substrate and 4.5 times stronger than the Ag thin film structure).

[0061] When TE polarized light is incident, the PL intensity of this structure is only ≈7800 au (4.1 times stronger than that of the Si / PMMA substrate), which is lower than the enhancement effect of the Ag thin film structure. This confirms that TM polarized light can form an effective oscillatory coupling with the free electrons on the silver grating surface, which is the dominant factor in PL enhancement.

[0062] As shown above, this application achieves highly efficient enhancement of photoluminescence in Rh800 dye molecules by precisely controlling sample preparation parameters and testing conditions: the enhancement factor reaches 22-22.6 times under resonance matching and still reaches 14 times under non-resonance conditions, and the sample exhibits narrow-angle emission characteristics and good reproducibility. This embodiment verifies the photoluminescence modulation capability of plasmon grating structures under multiple angles and polarization states, providing reproducible experimental evidence for the large-scale fabrication and application of related optical devices.

[0063] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for enhancing the photoluminescence of Rh800 dye molecules from multiple angles based on plasmon resonance, characterized in that, Includes the following steps: S1. A periodic photoresist grating is formed on a substrate and a silver film is thermally deposited on the surface of the grating to obtain a metal grating structure that can couple surface plasmons. S2. Prepare a Rh800-polymer PMMA solution and spin-coat the solution onto the surface of the metal grating structure and dry it to form a uniform dye organic film; S3. Adjust the incident angle and incident polarization of the excitation light and select the excitation wavelength so that the plasmon resonance mode of the metal grating partially overlaps with the excitation / emission spectrum of the dye organic film to obtain a resonance-matched excitation system, which is used to enhance the excitation process of the dye. S4. Perform angle-resolved excitation-collection photoluminescence measurement on the resonant matched excitation system and record the distribution of luminescence intensity with incident angle, collection angle and polarization to obtain multi-angle luminescence response curves; S5. Based on the multi-angle emission response curve, adjust the grating period, grating depth, metal film thickness or coating thickness, and repeat steps S3 to S4 to optimize and obtain photoluminescence output that exhibits stable enhancement under multiple incident and collection angles.

2. The method for enhancing the multi-angle photoluminescence of Rh800 dye molecules based on plasmon resonance according to claim 1, characterized in that, The grating has a period of 500–580 nm and a depth of 8–25 nm.

3. The method for enhancing the multi-angle photoluminescence of Rh800 dye molecules based on plasmon resonance according to claim 1, characterized in that, The thickness of the silver film is 100–200 nm.

4. The method for enhancing the multi-angle photoluminescence of Rh800 dye molecules based on plasmon resonance according to claim 1, characterized in that, The concentration of Rh800 is 1–3 mg·mL. -1 The PMMA mass fraction is 1-5 wt%, and the spin coating speed is 2000-5000 rpm.

5. The method for enhancing the multi-angle photoluminescence of Rh800 dye molecules based on plasmon resonance according to claim 1, characterized in that, The excitation wavelength is selected from 600 to 640 nm, and the emission peak of the dye is located in the range of 710 to 730 nm; the measurement scanning incident angle range is -12° to +12°, the angular resolution is 0.1° to 1°, and the mode adopts TM polarization.

6. The method for enhancing the multi-angle photoluminescence of Rh800 dye molecules based on plasmon resonance according to claim 1, characterized in that, The photoluminescence enhancement factor is obtained by comparing the peak luminescence intensity of the metal grating / dye sample with the peak luminescence intensity of the corresponding dye film on a planar silver film under the same excitation conditions.

7. The method for enhancing the multi-angle photoluminescence of Rh800 dye molecules based on plasmon resonance according to claim 1, characterized in that, Steps S3 to S5 can be repeated at least twice to verify the enhanced stability and repeatability, and in each cycle, the grating period, metal film thickness or coating thickness can be finely adjusted within ±15% to obtain the optimal multi-angle enhancement effect.

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