Au-s bond modified plasmonic enhancement of force-induced luminescence and flexible composites

Abstract

The application discloses a force-induced luminescence plasmon enhancement method based on Au-S bonding modification and a flexible composite material, and the method comprises the following steps: (1) selecting a force-induced luminescence matrix; (2) spectrum matching; (3) in-situ modification of Au-S bonding; and (4) preparation of a flexible device. The flexible composite material is a flexible force-induced luminescence composite material obtained through the above method. Through the dual synergistic effect of LSPR local electric field enhancement and interface Schottky trap regulation, the force-induced luminescence intensity is significantly improved, the luminescence intensity of a ZnS:Cu flexible film under a trace amount of loading is improved by 580%, and meanwhile, the problems of weak interface combination, easy agglomeration quenching and poor flexible cycle stability in a traditional blending method are solved. The method has simple process and low cost, and has wide application prospect in the fields of flexible stress sensing and wearable optoelectronic devices.

Description

Technical Field

[0001] This invention belongs to the field of mechanoluminescent functional materials and flexible optoelectronic devices. Specifically, it relates to a method for enhancing the mechanoluminescence performance of sulfide-based materials by modifying gold nanoparticles with Au-S covalent bonds and utilizing the localized surface plasmon resonance effect, as well as the corresponding flexible composite materials and applications. Background Technology

[0002] Mechanoluminescence (ML) is the phenomenon where materials directly convert mechanical energy into light energy under mechanical stress such as friction, impact, tension, and compression, achieving real-time stress-signal conversion without the need for an external power source. Flexible mechanoluminescence devices have significant application value in emerging fields such as wearable electronics, flexible stress sensing, human-computer interaction, and structural health monitoring.

[0003] Cu-doped zinc sulfide (ZnS:Cu) is currently the sulfide-based mechanoluminescent material with the highest industrialization potential. It has advantages such as tunable emission wavelength, good chemical stability, and repeated excitation without significant fatigue, making it the core light-emitting layer material for flexible mechanoluminescent devices. However, pure-phase ZnS:Cu exhibits low mechanoluminescence intensity and insufficient mechano-optical conversion efficiency, making it difficult to meet the practical requirements of high-sensitivity flexible sensing and high-brightness displays.

[0004] Existing enhancement strategies for ZnS:Cu mechanoluminescence mainly focus on intrinsic defect engineering and polymer matrix stress transfer optimization, but these have limited enhancement range and suffer from problems such as poor defect controllability and weak interfacial bonding. Localized surface plasmon resonance (LSPR) is a typical optical effect of noble metal nanoparticles, which can generate a strong local electric field around the particles and has been widely used for signal enhancement in photoluminescence systems.

[0005] Existing technologies have made some attempts to introduce gold nanoparticles into ZnS-based materials, but the preparation of flexible composite films generally adopts physical blending methods, which have three major drawbacks:

[0006] Weak interfacial bonding: Gold particles are only bonded to the ZnS matrix by van der Waals forces. Under dynamic stress such as repeated bending, stretching, and impact, they are prone to detachment and agglomeration, resulting in poor device cycle stability.

[0007] Uncontrollable spacing: The interface spacing between the gold particles and the luminescent center cannot be precisely controlled. If the distance is too close, it is easy to cause non-radiative energy transfer, resulting in luminescence quenching. If the distance is too far, the LSPR effect will fail, making it difficult to achieve stable enhancement.

[0008] Poor spectral matching: The size and morphology of gold particles were not systematically controlled according to the emission wavelength of ZnS:Cu, the LSPR resonance peak did not match the emission wavelength, resulting in extremely low enhancement efficiency.

[0009] Furthermore, existing technologies have not fully utilized the chemical activity of sulfur dangling bonds on the sulfide surface to construct a robust and controllable interface structure through Au-S covalent bonds; nor have they combined Au and ZnS to form a Schottky junction to achieve synergistic enhancement of optical enhancement and carrier trapping control.

[0010] Therefore, developing a flexible mechanoluminescence modification method with strong interface bonding, precise and controllable spacing, and high enhancement efficiency is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0011] To address the shortcomings of existing mechanoluminescence (MEL) technologies, this invention aims to provide a MEL plasmon enhancement method based on Au-S bonding modification, achieving robust interfacial bonding and precise subwavelength-scale spacing control to synergistically enhance MEL intensity. Simultaneously, it provides a high-performance flexible MEL composite material to solve the problems of weak interfacial bonding, easy quenching, low enhancement efficiency, and poor cycle stability in existing technologies.

[0012] The mechanoluminescence plasmon enhancement method based on Au-S bond modification of the present invention includes the following steps:

[0013] (1) Selection of mechanoluminescent matrix:

[0014] A sulfide-based mechanoluminescent matrix was selected, and the wavelength of its mechanoluminescence emission peak was measured.

[0015] The sulfide-based mechanoluminescent matrix is ​​ZnS:Cu, and its emission peak wavelength is located at 510 nm.

[0016] The sulfide-based mechanoluminescent matrix is ​​a semiconductor. Gold nanoparticles form a rectified Schottky junction in contact with the sulfide-based mechanoluminescent matrix. Under thermal equilibrium, electrons transfer from the semiconductor to the gold side, inducing the formation of abundant shallow trap states at the interface. This optimizes the capture, release, and recombination process of charge carriers under stress excitation. The surface trap energy level distribution is regulated by interfacial charge transfer, which, in conjunction with the LSPR optical effect, enhances mechanoluminescence.

[0017] (2) Spectral matching:

[0018] In a sulfide-based mechanoluminescent matrix, a gold precursor and a reducing agent are added, and gold nanoparticles are nucleated and grown on the matrix surface through an in-situ reduction reaction.

[0019] During the in-situ reduction reaction, the concentration of the gold precursor, the amount of reducing agent, and the reaction conditions are controlled. Based on the emission peak wavelength of the sulfide-based mechanoluminescent matrix, the size and surface loading density of the gold nanoparticles are controlled to match the spectrum of the local surface plasmon resonance peak of the gold nanoparticles with the mechanoluminescence emission peak, thereby controlling the effective interaction distance between the gold nanoparticles and the luminescent center of the matrix.

[0020] Furthermore:

[0021] The gold precursor is chloroauric acid or sodium chloroaurate; the reducing agent is one or more of sodium citrate, ascorbic acid, sodium borohydride, and polymer curing agent.

[0022] The reaction conditions refer to a temperature of 25~90℃ and a reaction time of 5~60min.

[0023] The gold nanoparticles have a particle size of 5-100 nm, resulting in an LSPR resonance peak of 510-530 nm.

[0024] The spectral matching refers to the fact that the center wavelength of the LSPR resonance peak of gold nanoparticles deviates from the center wavelength of the mechanoluminescence emission peak by no more than ±50 nm.

[0025] The effective interaction distance between the gold nanoparticles and the matrix luminescent center is 5~30nm.

[0026] (3) Au-S bond in-situ modification:

[0027] During the nucleation and growth process, gold atoms form Au-S covalent bonds with sulfur atoms on the matrix surface, resulting in a mechanoluminescent Au@sulfide composite particle slurry with surface-modified gold nanoparticles.

[0028] Au-S covalent bonds are formed by the bonding of gold atoms with sulfur dangling bonds on the matrix surface. The interface is firmly bonded, and the gold particles do not detach or aggregate under dynamic mechanical stress such as repeated bending, stretching, and impact.

[0029] (4) Fabrication of flexible devices:

[0030] The obtained Au@sulfide composite particle slurry was dispersed in an elastic polymer matrix, and after degassing and curing, a flexible mechanoluminescent composite material reinforced by mechanoluminescence plasmons was obtained. The resulting flexible composite material is in the form of a thin film and can withstand dynamic mechanical stresses such as bending, stretching, and repeated impacts.

[0031] The elastic polymer matrix is ​​selected from one of polydimethylsiloxane (PDMS), polyvinylidene fluoride (PVDF), and silicone rubber.

[0032] The mass fraction of the composite particles in the elastic polymer matrix is ​​5~80wt%.

[0033] This invention also protects an Au-S bonded flexible mechanoluminescent composite material prepared by the above method. It comprises an elastic polymer matrix and Au@sulfide composite particles uniformly dispersed in the elastic polymer matrix; the Au@sulfide composite particles include sulfide-based mechanoluminescent matrix particles and gold nanoparticles in situ modified on the surface of the matrix particles via Au-S covalent bonds; the localized surface plasmon resonance peak of the gold nanoparticles matches the emission spectrum of the matrix; the effective interaction distance between the gold nanoparticles and the luminescent center of the matrix is ​​on a subwavelength scale of 5~30 nm.

[0034] The above-mentioned Au-S bonded flexible mechanoluminescent composite material has applications in flexible stress sensing, wearable light-emitting devices, human-computer interaction, structural health monitoring, and anti-counterfeiting labeling.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. Strong interface bonding and excellent flexible cycle stability.

[0037] This invention utilizes the natural sulfur active sites on the surface of sulfides to form Au-S covalent bonds through in-situ reduction. The interfacial binding energy is much higher than that of van der Waals forces, making it difficult for gold particles to detach or agglomerate under dynamic stress such as repeated bending, stretching, and impact. The prepared flexible composite material retains more than 95% of its luminescence intensity after 600 cycles of impact, and its service life is significantly extended.

[0038] 2. Precise and controllable spacing prevents quenching at its source.

[0039] By adjusting the size of the gold particles, the surface density of the load, and the reaction conditions, the effective interaction distance between the gold particles and the luminescence center can be precisely controlled within an effective enhancement window of 5~30nm. This ensures that the near-field electric field of the LSPR works effectively while avoiding the quenching range of near-distance non-radiative energy transfer, achieving stable and repeatable luminescence enhancement and solving the industry's pain point of "difficulty in balancing enhancement and quenching".

[0040] 3. Dual mechanisms work together to enhance efficiency.

[0041] This invention simultaneously leverages the synergistic effect of two types of enhancement mechanisms:

[0042] LSPR optical enhancement: The matched resonance peak generates a strong local electric field, which enhances the radiative transition rate of Cu luminescent centers through the Purcell effect, suppresses nonradiative recombination, and improves luminescence quantum efficiency and photon emission efficiency.

[0043] Interfacial carrier modulation: Au and ZnS:Cu form a rectified Schottky junction, and the interfacial charge transfer induces abundant shallow trap states, optimizing the release and recombination process of stress-excited carriers, and further improving the mechanoluminescence intensity.

[0044] Under the synergistic effect of the dual mechanisms, the mechanoluminescence intensity of ZnS:Cu can be increased by more than 500% under optimal conditions.

[0045] 4. Even trace amounts of gold can enhance surface loading density, resulting in significant cost advantages.

[0046] This invention achieves efficient anchoring and utilization of gold nanoparticles through Au-S bonding. Significant luminescence enhancement can be achieved with an extremely small amount of Au on the surface, at the level of one ten-thousandth (wt%). The amount of precious metal used is far lower than that of traditional blending and doping systems, which greatly reduces the material cost of flexible devices and is suitable for large-scale promotion.

[0047] 5. The process is simple and controllable, suitable for mass production of flexible devices.

[0048] This invention employs a liquid-phase in-situ reduction combined with polymer curing process, which features mild reaction conditions, easily adjustable parameters, good batch repeatability, no need for expensive equipment, and can be directly integrated into existing flexible optoelectronic device production lines, making it highly adaptable to industrialization. Attached Figure Description

[0049] Figure 1 This is a process flow diagram of the mechanoluminescence plasmon enhancement method based on Au-S bonding modification according to the present invention.

[0050] Figure 2 This is a schematic diagram illustrating the structural formation and reinforcement mechanism of the Au-S bonded flexible mechanoluminescent composite material in this invention;

[0051] Figure 3 The image shows the SEM morphology of the Au@ZnS:Cu composite particles obtained in Example 1. The scale bar on the left is 10 μm, and the right image is a magnified view of the yellow line area in the left image (scale bar 5 μm).

[0052] Figure 4 The images show the SEM morphology and corresponding EDS gold element mapping of the Au@ZnS:Cu / PDMS composite material obtained in Example 1; where: the left image is the SEM morphology image, and the right image is the corresponding EDS gold element mapping.

[0053] Figure 5 This is a comparison of the mechanoluminescence spectra of Example 1 and Comparative Example 1;

[0054] Figure 6 This is a comparison of the mechanoluminescence spectra of Example 2 and Comparative Example 2;

[0055] Figure 7This is a comparison of the mechanoluminescence spectra of Example 3 and Comparative Example 3;

[0056] Figure 8 The image shows a comparison of the stretching curves of the flexible rectangular composite devices of ZnS:Cu / PDMS before and after Au doping obtained in Examples 1 and 3. Detailed Implementation

[0057] This invention utilizes sulfur-active sites on the surface of a sulfide matrix to form Au-S covalent bonds between gold nanoparticles and the matrix surface through an in-situ reduction method. This achieves strong interfacial bonding and precise spacing control at the subwavelength scale. Simultaneously, by controlling the size of the gold particles, the LSPR peak is matched with the emission wavelength. Combined with the carrier modulation effect of the interfacial Schottky junction, the mechanoluminescence intensity is synergistically enhanced, ultimately producing a high-performance flexible mechanoluminescent composite material. This invention solves the problems of weak interfacial bonding, easy quenching, low reinforcement efficiency, and poor cycle stability in existing technologies.

[0058] The following is combined Figure 1 and Figure 2 The specific embodiments will provide a more detailed description of the technical solution of the present invention, but the scope of protection of the present invention is not limited thereto.

[0059] Example 1: Extremely low Au surface loading density @ 20wt% ZnS:Cu / PDMS flexible composite material (best example)

[0060] (1) ZnS:Cu was selected as the mechanoluminescent matrix with an emission peak wavelength of 510 nm.

[0061] (2) Spectral matching

[0062] By selecting different concentrations of HAuCl4 precursor solutions (see step (3) for details), the size and surface loading density of the prepared Au nanoparticles were adjusted, and the Au@ZnS:Cu distance was precisely controlled within the range of 5~30nm, so that the LSPR resonance peak was located at 510~530nm, with a deviation of <10nm from the emission wavelength, thus meeting the matching requirements.

[0063] (3) Au-S bond modification

[0064] ① Weigh 0.03g of ZnS:Cu phosphor and mix it with 4.5μL of chloroauric acid (HAuCl4) ethanol solution (concentration of 7.8μmol / L, the concentration determines the size of Au nanoparticles and surface loading density). Stir and mix thoroughly to ensure that Au³⁺ is fully adsorbed onto the sulfur active sites on the ZnS surface.

[0065] ② Add 0.012g of PDMS curing agent (Sylgard 184), stir for 5 minutes at room temperature (25℃) until homogeneous. The reducing groups in the curing agent cause chloroauric acid to undergo an in-situ reduction reaction on the surface of ZnS:Cu particles. Gold atoms form Au-S covalent bonds with surface sulfur atoms, generating discretely distributed gold nanoparticles that are uniformly modified on the surface of ZnS:Cu particles.

[0066] Characterized, such as Figure 3 As shown, the Au nanoparticles have an average particle size of approximately 70 nm and are uniformly and discretely distributed on the surface of ZnS:Cu particles (the surface loading of Au nanoparticles relative to the mass fraction of ZnS:Cu is approximately 0.000023 wt%), with no obvious agglomeration; Au-S covalent bonds are formed at the interface, and the bonding is strong. Figure 4 It can be seen that Au elements are mainly concentrated near the surface of ZnS:Cu particles; the average effective interaction distance between gold particles and Cu luminescence centers in the matrix is ​​about 5~20nm, which is in the subwavelength effective enhancement range of 5~30nm; UPS test shows that the work function of the gold-doped sample is 0.07eV lower than that of the undoped pure sample, confirming that electron transfer occurs at the interface and the Schottky contact is successfully constructed.

[0067] (4) Preparation of flexible composite films:

[0068] Add 0.12g of PDMS (elastic polymer matrix to curing agent mass ratio 10:1) to the mixed slurry of Au@ZnS:Cu composite particles obtained above, so that the actual loading of ZnS:Cu is about 20wt%. After stirring evenly, degas for 10min, pour into a polytetrafluoroethylene mold, and cure at 90℃ for 30min to obtain a flexible composite film with a thickness of about 1mm.

[0069] Example 2: Micro-Au Loading @ 37wt%ZnS:Cu / PDMS Flexible Composite Material

[0070] The only difference between this embodiment and Example 1 is that: 0.059g of ZnS:Cu phosphor was weighed, the concentration of the chloroauric acid precursor remained unchanged (7.8μmol / L), the added volume was 7.7μL (the mass fraction of Au relative to ZnS:Cu remained unchanged), 0.01g of curing agent and 0.1g of PDMS prepolymer were added, and the actual ZnS:Cu loading was approximately 37wt%. The in-situ reduction reaction was carried out at 60℃ for 30min. All other preparation conditions and testing methods were the same as in Example 1.

[0071] Example 3: Micro-Au Loading @ 67wt%ZnS:Cu / PDMS Flexible Composite Material

[0072] The only difference between this embodiment and Example 1 is that: 0.12g of ZnS:Cu phosphor was weighed, the concentration of chloroauric acid solution remained unchanged (7.8μmol / L), the volume added was 15.5μL (the mass fraction of Au relative to ZnS:Cu remained unchanged), 0.006g of curing agent and 0.06g of PDMS prepolymer were added, and the actual ZnS:Cu loading was 67wt%. The in-situ reduction reaction was carried out at 90℃ for 5 min. All other preparation conditions and testing methods were the same as in Example 1.

[0073] Example 4: High Au loading @ 20wt% ZnS:Cu / PDMS flexible composite material

[0074] The only difference between this embodiment and Example 1 is that the concentration of the chloroauric acid solution added is significantly increased to 780 μmol / L, while the volume remains the same. The in-situ reduction reaction is carried out at 30°C for 50 min. All other preparation conditions and testing methods are consistent with Example 1, and the mass fraction of the composite particles in the elastic polymer matrix remains unchanged. Due to the excessively high surface loading density of the Au particles, the gold particles exhibit significant agglomeration, with the distance between the luminescent center and the gold particle in some areas being less than 5 nm.

[0075] Example 5: Sodium chloroaurate precursor (PVDF-based flexible mechanoluminescent composite film, ascorbic acid reduction)

[0076] 0.5g of ZnS:Cu phosphor was added to anhydrous ethanol and sonicated to form a uniform suspension. 75μL of sodium chloroaurate ethanol solution was slowly added dropwise under magnetic stirring. Stirring was continued for 30min in the dark to allow the extremely low concentration of AuCl4 to fully combine with the S sites and sulfur vacancies on the surface through electrostatic interaction, thereby achieving directional enrichment and adsorption.

[0077] The system was heated to 40℃, and a diluted ascorbic acid solution was added dropwise at a uniform rate. After the addition was complete, the mixture was stirred at a constant temperature for 20 min to complete the in-situ reduction. Trace amounts of Au atoms preferentially nucleated and grew at the active S sites on the surface, simultaneously forming Au–S covalent bonds for strong anchoring. No free Au particles were generated. The mixture was washed by centrifugation at 3000 rpm and vacuum dried at 50℃ for 12 h to obtain Au-modified ZnS:Cu powder.

[0078] PVDF powder was added to NMP and stirred at 60°C until completely dissolved; Au-modified ZnS:Cu powder was added and stirred for another 30 minutes to form a uniform suspension slurry, which was then degassed under vacuum to remove air bubbles.

[0079] The slurry was uniformly poured onto a glass substrate and dried at 80°C for 4 hours to remove the solvent. Then, the temperature was raised to 120°C for annealing for 2 hours to promote the crystallization of PVDF and form a piezoelectric β phase, finally obtaining a flexible PVDF-based mechanoluminescent composite film.

[0080] Example 6: Silicone rubber-based flexible mechanoluminescent composite material (reduced by sodium citrate)

[0081] 225 μL of 7.8 μmol / L sodium chloroaurate ethanol solution, 0.6 mg of sodium citrate, and 1.5 g of ZnS:Cu phosphor were mixed and stirred thoroughly to ensure that the precursor was uniformly attached to the powder surface. Excess ethanol was removed by low-temperature drying to obtain the precursor-loaded mixed powder.

[0082] Add the mixed powder to the silicone rubber base and stir at low speed for 15 minutes until it is evenly dispersed; add the curing agent and continue stirring for 5 minutes, then vacuum degas for 5 minutes to remove the air bubbles introduced by stirring.

[0083] The slurry was injected into the mold and placed in an 80℃ oven for constant temperature curing for 2 hours. During the heating process, sodium citrate gradually released its reducing power, and Au³⁺ was reduced and nucleated in situ at the S sites on the ZnS surface to form Au–S covalent bonds, while simultaneously completing the cross-linking and curing of the silicone rubber, ultimately yielding a silicone rubber-based flexible mechanoluminescent composite material.

[0084] Comparative Example 1: Pure 20wt% ZnS:Cu / PDMS flexible composite material

[0085] The only difference between this embodiment and Example 1 is that the chloroauric acid precursor solution is not added; all other preparation conditions and testing methods are the same as in Example 1.

[0086] Comparative Example 2: Pure 37wt% ZnS:Cu / PDMS Flexible Composite Material

[0087] The only difference between this embodiment and Example 2 is that the chloroauric acid precursor solution is not added; all other preparation conditions and testing methods are the same as in Example 2.

[0088] Comparative Example 3: Pure 67wt% ZnS:Cu / PDMS Flexible Composite Material

[0089] The only difference between this embodiment and Example 3 is that the chloroauric acid precursor solution is not added; all other preparation conditions and testing methods are the same as in Example 3.

[0090] The following are the results of the metronome intensity test.

[0091] The luminescence intensity of the flexible composite samples was tested by applying dynamic periodic pressure (60 MPa, 20 Hz). Each sample was tested five times, and the average value was taken. Based on the different ZnS:Cu contents, the peak intensity of Comparative Example 1 (20 wt% ZnS:Cu content) was used as the benchmark, as were the peak intensities of Comparative Example 2 (37 wt% ZnS:Cu content) and Comparative Example 3 (67 wt% ZnS:Cu content). The test results are as follows:

[0092]

[0093] Figure 5 A comparison of the mechanoluminescence spectra of Example 1 and Comparative Example 1 is provided; Figure 6 A comparison of the mechanoluminescence spectra of Example 2 and Comparative Example 2 is provided; Figure 7 A comparison of the mechanoluminescence spectra of Example 3 and Comparative Example 3 is provided.

[0094] The following provides verification of the flexibility of the composite material:

[0095] The concentration of trace Au doping is relatively low (7.8 × 10⁻⁶). −6 mol / L), at different ZnS:Cu loadings of 20 wt% and 67 wt% (see mol / L). Figure 8 Under these conditions, the stress-strain curves of the original and Au-doped samples show that this plasma modification does not reduce the softness and elastic modulus of the elastomer by much (~1.5 MPa and 3.5 MPa, respectively). Figure 8 The middle image shows a photograph of a rectangular composite thin film device (20mm×10mm×1mm) under a uniaxial tensile test.

[0096] The following is a verification of the interface electronic structure:

[0097] UPS testing showed that the work function of the sample in Example 1 was 0.07 eV lower than that in Comparative Example 1, confirming that Au and ZnS:Cu form a Schottky contact, charge transfer occurs at the interface, and the trap energy level is modulated, which is consistent with the synergistic enhancement mechanism of LSPR+ interface carrier modulation.

[0098] The results show that:

[0099] The method of this invention can achieve significant enhancement of mechanoluminescence (ML) in ZnS:Cu weight ratio systems at extremely low gold surface loading densities, verifying the feasibility and universality of the method.

[0100] High surface loading density Au nanoparticles covering the ZnS:Cu surface caused near-zero distance close contact, which in turn led to luminescence quenching. This proves that 5~30nm subwavelength control is the core necessary condition for achieving enhancement. The negative effects of nonradiative energy transfer quenching + internal filtration loss + deep trap overload quickly exceeded the enhancement contribution, which ultimately manifested as a decrease in luminescence intensity and a significant increase in absorption loss.

[0101] The ML reinforcement effect of Au-S bonded modification is far superior to that of pure ZnS:Cu flexible composite material without gold doping.

[0102] Examples 1 and 2 were subjected to 700 cycles of 60 MPa, 20 Hz shock cycling for stability testing. After cycling, the ML strength retention rate was 95%. This demonstrates that the robust interface formed by Au-S bonding can significantly improve the cycling stability of the device and avoid performance degradation caused by particle shedding and aggregation.

Claims

1. A method for enhancing mechanoluminescence plasmon resonance based on Au-S bonding modification, characterized in that, Includes the following steps: (1) Selection of mechanoluminescent matrix: A sulfide-based mechanoluminescent matrix was selected, and its mechanoluminescence emission peak wavelength was measured. (2) Spectral matching: In a sulfide-based mechanoluminescent matrix, a gold precursor and a reducing agent are added, and gold nanoparticles are nucleated and grown on the matrix surface through an in-situ reduction reaction. During the in-situ reduction reaction, the concentration of the gold precursor, the amount of reducing agent, and the reaction conditions are controlled. Based on the emission peak wavelength of the sulfide-based mechanoluminescent matrix, the size and surface loading density of the gold nanoparticles are controlled so that the local surface plasmon resonance peak of the gold nanoparticles matches the spectrum of the mechanoluminescence emission peak, thereby controlling the effective interaction distance between the gold nanoparticles and the luminescent center of the matrix. (3) Au-S bond in-situ modification: During the nucleation and growth process, gold atoms form Au-S covalent bonds with sulfur atoms on the matrix surface, resulting in a mechanoluminescent Au@sulfide composite particle slurry with surface-modified gold nanoparticles. (4) Fabrication of flexible devices: The obtained Au@sulfide composite particle slurry was dispersed in an elastic polymer matrix, and after degassing and curing, a flexible mechanoluminescent composite material with mechanoluminescent plasmon reinforcement was obtained.

2. The method for enhancing mechanoluminescence plasmon resonance based on Au-S bonding modification according to claim 1, characterized in that, The sulfide-based mechanoluminescent matrix is ​​ZnS:Cu, and its emission peak wavelength is located at 510 nm.

3. The method for enhancing mechanoluminescence plasmon resonance based on Au-S bonding modification according to claim 1, characterized in that, The gold precursor is chloroauric acid or sodium chloroaurate; the reducing agent is one or more of sodium citrate, ascorbic acid, sodium borohydride, and polymer curing agent.

4. The method for enhancing mechanoluminescence plasmon resonance based on Au-S bonding modification according to claim 1, characterized in that, The reaction conditions refer to a temperature of 25~90℃ and a reaction time of 5~60min.

5. The method for enhancing mechanoluminescence plasmon resonance based on Au-S bonding modification according to claim 1, characterized in that, The gold nanoparticles have a particle size of 5-100 nm, resulting in an LSPR resonance peak of 510-530 nm.

6. The method for enhancing mechanoluminescence plasmon resonance based on Au-S bonding modification according to claim 1, characterized in that, The spectral matching refers to the fact that the center wavelength of the LSPR resonance peak of gold nanoparticles deviates from the center wavelength of the mechanoluminescence emission peak by no more than ±50 nm.

7. The method for enhancing mechanoluminescence plasmon resonance based on Au-S bonding modification according to claim 1, characterized in that, The effective interaction distance between the gold nanoparticles and the matrix luminescent center is 5~30nm.

8. The method for enhancing mechanoluminescence plasmon resonance based on Au-S bonding modification according to claim 1, characterized in that, The elastic polymer matrix is ​​selected from one of polydimethylsiloxane, polyvinylidene fluoride, and silicone rubber.

9. The method for enhancing mechanoluminescence plasmon resonance based on Au-S bonding modification according to claim 1, characterized in that, The mass fraction of the composite particles in the elastic polymer matrix is ​​5~80wt%.

10. A flexible mechanoluminescent composite material prepared by the method according to any one of claims 1-9.

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