Multi-mode dynamic luminescent material as well as preparation method and application thereof

Abstract

The invention discloses a multi-mode dynamic photoluminescent material as well as a preparation method and application thereof. The chemical composition of the material is SrGa2O4: xDy < 3 + >, and x is equal to 0.01-0.05 (preferably, x is equal to 0.025, namely, the atomic ratio of Dy < 3 + > to Sr < 2 + > is 2.5%). Under the excitation of 254 nm ultraviolet light, the material can present a dynamic photoluminescence change from yellow (corresponding to transition from Dy < 3 + > 4F9 / 2 to 6H13 / 2) to blue (corresponding to intrinsic emission of a SrGa2O4 matrix at a main peak of 410 nm) along with the prolonging of irradiation time, and has a carrier capture center (trap level depth is 0.88-0.98 eV); according to the invention, light-level carriers can be cleared through 365 nm ultraviolet light, the light emitting color is locked to be yellow, and the light emitting state can be further accurately regulated and controlled through 300-520 K temperature regulation and control (blue emission is gradually inhibited at 300-420 K, and blue light is completely inhibited at 440 K or above, and only yellow emission is retained). The invention further provides a high-temperature solid-phase preparation method (heat preservation at 1350 DEG C for 6 h) of the material and application of the material in a multistage anti-counterfeit label and an optical sequential logic switch, and the material has time (pulse duty ratio)-light (dual-ultraviolet cooperation)-temperature (300-520 K) multi-dimensional light-emitting regulation and control capability and is suitable for the fields of high-end information encryption and flexible optoelectronic devices.

Description

Technical Field

[0001] This invention relates to the fields of luminescent materials, information encryption and anti-counterfeiting technology, specifically to a Dy-doped SrGa2O4 inorganic oxide fluorescent material and its preparation method, as well as the application of this material in dynamic photoluminescence regulation, intelligent anti-counterfeiting, optical sequential logic switch construction and multiple information encryption. Background Technology

[0002] Dynamic multicolor luminescent materials, with their ability to exhibit different fluorescent colors depending on external conditions, have demonstrated significant application value in information encryption and anti-counterfeiting. Inorganic oxide luminescent materials, due to their rich and tunable dynamic multicolor fluorescence performance, have become a research hotspot in this field. However, the development of oxide-based dynamic multicolor luminescent materials still faces several bottlenecks: (1) Insufficient understanding of the physical mechanism of dynamic light emission: The lack of in-depth understanding of the physical process of dynamic light emission in oxides limits the design and optimization of multi-mode regulation strategies.

[0003] (2) Single control method: Existing dynamic light emission control mainly relies on continuous light irradiation, which results in a fast color change rate and makes it difficult to achieve precise control of the color change time.

[0004] (3) The mechanism of multi-source light source regulation is unclear: There is a lack of understanding of the dynamic light emission mechanism under the synergistic effect of different wavelength light sources, and it is impossible to effectively expand the means of regulating multi-modal dynamic light emission.

[0005] (4) Limited application scenarios: The application of dynamic multicolor light emission is mostly limited to the field of anti-counterfeiting, and its rich physical connotation has not been fully developed in diverse life and work scenarios.

[0006] Therefore, developing an oxide-based dynamic luminescent material with multimodal dynamic luminescence control capability, a clear physical mechanism, and a wide range of applications has become an urgent technical problem to be solved. Summary of the Invention

[0007] Purpose of the invention This invention aims to provide a Dy-doped SrGa2O4 inorganic oxide fluorescent material and its preparation method. This material can achieve multimodal dynamic luminescence by controlling the energy level and concentration of the captured central carriers, solving the problems of single control method, unclear mechanism and limited application of existing oxide dynamic luminescence materials. At the same time, it expands its application in the fields of intelligent anti-counterfeiting, optical Boolean state machines and information encryption.

[0008] Technical solution Material composition A multimodal dynamic luminescent SrGa2O4:Dy material with the chemical composition SrGa2O4:xDy 3+ Dy 3+Compared to Sr 2+ The atomic doping ratio x is 0.01-0.05; preferably, x=0.025 (i.e., 2.5%). This material retains the centrosymmetric original monoclinic phase of SrGa2O4, with space group P21 / c and Dy... 3+ Replace Sr 2+ Lattice sites are introduced, along with oxygen vacancies and carrier trapping centers. With varying doping ratios, the lattice constant of the material lies in the ranges of a = 8.36–8.40 Å, b = 9.00–9.01 Å, and c = 10.65–10.69 Å, and the cell volume varies with Dy. 3+ Replace Sr 2+ Slight shrinkage, no impurity phase.

[0009] 2.2 Preparation method This invention employs a high-temperature solid-state reaction method to prepare SrGa2O4:xDy 3+ Materials and specific steps are as follows: a) Weigh the raw materials according to the stoichiometric ratio: SrCO3 (purity ≥99.5%), Ga2O3 (purity ≥99.99%), and Dy(Ac)3·4H2O (purity ≥99.8%), wherein the amount of Dy(Ac)3·4H2O added is based on Dy 3+ With Sr 2+ The atomic ratio x = 0.01-0.05 is determined; b) Place the above ingredients in a mortar and grind manually for 30 minutes to ensure the ingredients are mixed evenly; c) Mix and grind the raw materials for at least 30 minutes to ensure a uniform mixture; d) The ground mixed powder is transferred to an alumina boat and placed in a box furnace (OTF-1700X) for high-temperature reaction. The temperature is increased to 1350 ℃ at a heating rate of 5 ℃ / min and held for 6 h. The temperature control accuracy of the box furnace is ±1 ℃. The reaction process does not require a protective atmosphere and pure phase synthesis is achieved in an air atmosphere.

[0010] e) After the reaction is complete, the furnace is cooled to room temperature to obtain SrGa2O4:xDy 3+ Powder materials.

[0011] 2.3 Performance Characteristics a) Crystal structure and morphological characteristics: Dy 3+ Doping did not change the crystal structure of SrGa2O4, and no impurity phases were formed; after doping, the lattice constants a, b, and c decreased slightly, the cell volume shrank, and Dy... 3+ Sr sites are preferentially replaced; the material exhibits a neat crystal morphology and regular boundaries, with Sr, Ga, O, and Dy elements uniformly distributed on the grains, and (032) and (110) crystal planes can be observed; Dy3+ The incorporation introduces more oxygen vacancies, providing sites for carrier trapping.

[0012] b) Dynamic multicolor emission characteristics: Under 254 nm ultraviolet light irradiation, the material exhibits dynamic fluorescence emission from yellow to blue. In the initial stage (low carrier concentration), it emits fluorescence through Dy... 3+ The yellow light channel (main peak at 580 nm, 4F) 9 / 2 -6H 13 / 2 The light emission occurs during energy level transitions, and later (when the carrier concentration is high), the light emission occurs through the blue light channel of the matrix SrGa2O4 (with the main peak at 410 nm). The highest peak of the yellow emission peak is located in the 560-610 nm range, and the highest peak of the blue emission peak is located in the 400-450 nm range. c) The dynamic luminescence process is highly correlated with the energy level / concentration of the trapped center carriers. The material has a carrier trapping center. After being charged with 254 nm ultraviolet light, the thermoluminescence spectrum of the material shows a single main peak. As the charging temperature increases from 300 K to 500 K, according to the empirical calculation formula for the trapped center energy level Et, Et = Tm / 500, where Tm is the center position of the thermoluminescence spectrum peak, the peak temperature of the thermoluminescence is calculated to increase from 440 K to 460 K, and the corresponding trapping energy level depth is 0.88-0.98 eV. After being charged with 254 nm ultraviolet light for 70 s, the trapped carrier concentration reaches saturation.

[0013] d) Multi-dimensional regulatory capabilities: Temperature regulation: At 300 K (room temperature), it exhibits dynamic emission from yellow to blue. In the temperature range of 300-520 K, as the temperature increases, the blue emission channel is gradually suppressed. At 440-520 K, the blue light channel is completely suppressed, and only the dynamic process of yellow light enhancement is retained. Pulsed UV light modulation: By controlling 254 nm pulsed UV light with STM32, the color change rate and color gamut can be adjusted by changing the duty cycle. A 90% duty cycle achieves a rapid yellow-to-blue transition, while a 10% duty cycle significantly slows down the color change process. When excited by 254 nm pulsed UV light (10 ms period, 100 Hz frequency), the dynamic yellow-to-blue transition time decreases as the duty cycle increases. Dual-wavelength ultraviolet light synergistic modulation: 365 nm ultraviolet light can clear shallow-level carriers in the trap center. When it works in synergy with 254 nm ultraviolet light, it suppresses the blue emission channel, and the material exhibits dynamic luminescence from dark yellow to bright yellow, and yellow light locking can be achieved; after turning off the 365 nm light, the yellow-to-blue process is restored. Cyclic stability: After removing charge carriers by thermal excitation (temperature of 500 K), the dynamic luminescence performance can be reproduced under 254 nm ultraviolet light irradiation. The dynamic luminescence-thermal excitation reduction cycle can be repeated at least 4 times without significant degradation of luminescence performance. The placement time can be adjusted to control the concentration of charge carriers in the capture center, thereby changing the response time of yellow to blue.

[0014] e) Thermoluminescence and lifetime characteristics: The trapping energy center of the thermoluminescence spectrum at room temperature (300 K) is 440 K, corresponding to a trapping energy level depth of 0.88 eV; the emission lifetime of 580 nm yellow light is 0.4 ms under 350 nm excitation and extends to 0.55 ms under 254 nm excitation; the lifetime of 410 nm blue light is 2.11 ms under 254 nm excitation and 6.8 μs under 350 nm excitation.

[0015] 2.4 Application Directions a) Intelligent anti-counterfeiting: Utilizing the dynamic luminescence characteristics of materials under different ultraviolet light irradiation, temperatures, and pulsed light, patterned anti-counterfeiting is achieved, forming multiple anti-counterfeiting marks through the time and color changes of yellow / blue emission; b) Optical sequential logic switch: Based on the coordinated control of 254 nm (U) and 365 nm (V) ultraviolet light, an optical switch with time-sequential logic is constructed, defining color state C (blue is 1, non-blue is 0), which can be applied to optical computing and industrial logic design; c) Multi-level information encryption: Combining multi-dimensional control of temperature, pulsed light, and dual-wavelength ultraviolet light, multi-level encryption and decryption of information can be achieved; d) Flexible optoelectronic devices: dynamic light-emitting thin films are prepared by combining with flexible polymers and applied to wearable devices and flexible displays.

[0016] 3. Beneficial effects Compared with the prior art, the present invention has the following significant advantages: Multimodal control capability: Through various means such as temperature, pulsed ultraviolet light, and dual-wavelength ultraviolet light synergy, precise control of dynamic light emission is achieved, solving the problem of the single dynamic light emission control method of traditional oxides.

[0017] A clear physical mechanism: The correlation between dynamic luminescence and the energy level / concentration of carriers at the trapping center was clarified, providing a theoretical basis for the design and optimization of oxide dynamic luminescent materials.

[0018] Abundant application scenarios: Breaking through the limitation of dynamic light-emitting materials being used only for anti-counterfeiting, it has been extended to fields such as optical sequential logic switches, multiple encryption of information, and flexible optoelectronic devices.

[0019] High security level: Anti-counterfeiting is based on the intrinsic physicochemical properties of the material, and its multi-mode, dynamic optical response is extremely difficult to copy or imitate.

[0020] The preparation process is simple: it is prepared by high-temperature solid-phase reaction, the raw materials are readily available, the process is mature and the cost is low, making it suitable for large-scale production; the material has good cycle stability and environmental adaptability, and is highly practical. Attached Figure Description

[0021] Figure 1 These are the XRD patterns of SrGa2O4:xDy in Examples 1-6 and SrGa2O4 in the comparative example.

[0022] Figure 2 This is a bar chart comparing the lattice constants a, b, and c of Example 3 SrGa2O4:0.025Dy and Comparative Example SrGa2O4.

[0023] Figure 3 These are scanning electron microscope images of Example 3 SrGa2O4:0.025Dy and Comparative Example SrGa2O4.

[0024] Figure 4 The content of each element in SrGa2O4:0.025Dy in Example 3 was determined by XRF testing.

[0025] Figure 5 This is the X-ray photoelectron spectrum of SrGa2O4:0.025Dy in Example 3.

[0026] Figure 6 This is a graph showing the dynamic emission spectrum of the SrGa2O4:0.025Dy material in Example 3 at 300 K over time (0.05 s-20 s, yellow light weakens and blue light strengthens). Figure 7 This is a graph showing the dynamic emission spectrum of the SrGa2O4:0.025Dy material in Example 3 at 500 K over time (only yellow light is enhanced, no blue light is observed). Figure 8 This is a thermoluminescence curve of the SrGa2O4:0.025Dy material in Example 3 after irradiation with 254 nm ultraviolet light for different times.

[0027] Figure 9 The thermoluminescence spectra of SrGa2O4:0.025Dy material in Example 3 at different temperatures (300 K-500 K, with the peak temperature shifting to the right as the temperature increases). Figure 10 This is a schematic diagram of the pulsed ultraviolet light modulation device for the SrGa2O4:0.025Dy material in Example 3 (including an STM32 controller, a 254 nm pulsed LED, and a spectrometer). Figure 11 The image shows the dynamic emission spectrum of the SrGa2O4:0.025Dy material in Example 3 at a 10% duty cycle (stable blue at 120 s).

[0028] Figure 12 The image shows the dynamic emission spectrum of the SrGa2O4:0.025Dy material in Example 3 at a 90% duty cycle (stable blue at 60 s).

[0029] Figure 13 This is a schematic diagram of the dynamic luminescence of the SrGa2O4:0.025Dy material under synergistic regulation at 254 and 365 nm in Example 3 (dark yellow → deep yellow).

[0030] Figure 14 This is a dynamic luminescence cycle stability test chart of the SrGa2O4:0.025Dy material in Example 3 (luminescence intensity retention rate ≥95% after 4 cycles).

[0031] Figure 15 This is a schematic diagram of the anti-counterfeiting features of the Chinese character pattern on the SrGa2O4:0.025Dy material in Example 3 (3 s yellow, 20 s blue, and yellow after 365 nm afterglow irradiation).

[0032] Figure 16 This is a schematic diagram of the optical sequential logic switch of the SrGa2O4:0.025Dy material in Example 3 (the relationship between the U and V switches and the C state is marked). Detailed Implementation

[0033] The present invention will now be described in more detail through embodiments and comparative examples, in conjunction with the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0034] The specific embodiments 1-6 and the comparative examples of the present invention were all prepared by high-temperature solid-state synthesis. SrCO3 (purity ≥99.5%), Ga2O3 (purity ≥99.99%) and Dy(Ac)3·4H2O (purity ≥99.8%) were weighed according to the stoichiometric ratio, wherein the amount of Dy(Ac)3·4H2O used satisfies SrGa2O4:xDy 3+ In the case of x=0-0.05, the above raw materials are manually ground in a mortar for 30 minutes to ensure uniform mixing. Then, the mixed powder is transferred to an alumina boat and placed in a box furnace. The temperature is increased to 1350 ℃ at a rate of 5 ℃ / min and held for 6 h. All steps are based on the above experimental scheme. The difference lies in the different raw material ratios, which result in different x values ​​in SrGa2O4:xDy. The material composition and raw material mass of the specific embodiment are shown in Table 1.

[0035] Table 1. Material composition and raw material mass of SrGa2O4:xDy in Examples 1-6 and the comparative example SrGa2O4.

[0036]

[0037] Figure 1 These are the XRD patterns of SrGa2O4:xDy from Examples 1-6 and the comparative example SrGa2O4. All diffraction peaks in the figures match the SrGa2O4 standard card (ICDD-PDF#04-013-0783), and there are no diffraction peaks from any impurity phases.

[0038] Figure 2 This is a histogram comparing the lattice constants a, b, and c of Example 3 and the comparative example. The results show that after Dy doping, a decreased from 8.3806 Å to 8.3768 Å, b from 8.9982 Å to 8.9934 Å, and c from 10.6820 Å to 10.6732 Å. This uniform linear shrinkage confirms the presence of Dy. 3+ (Ionic radius 1.03 Å) Successfully replaced Sr 2+ (Ionic radius 1.18 Å) lattice sites without disrupting the matrix crystal structure, providing a single and stable matrix structure for subsequent trap energy levels and dynamic luminescence modulation.

[0039] Figure 3 These are scanning electron microscope (SEM) images of SrGa2O4:2.5%Dy in Example 3 and the comparative example SrGa2O4. The materials exhibit a neat and regular blocky crystal morphology with clear crystal boundaries, no obvious agglomeration, and a uniform particle size distribution (average particle size 5-8 μm). Under high magnification, the crystal surface is smooth and free of impurity phases, indicating that the high-temperature solid-phase reaction is complete. 3+ Doping does not alter the inherent crystal growth habit of SrGa2O4. This microstructure facilitates the uniform capture and release of charge carriers, ensuring the stability of dynamic luminescence. The morphologies of other embodiments are similar to those in Embodiment 3 and will not be described again.

[0040] Figure 4 The elemental content of SrGa2O4:2.5%Dy in Example 3 was determined by XRF testing. The spectrum showed characteristic peaks for Sr, Ga, O, and Dy, which perfectly matched the elemental composition of the target material. No additional impurity element peaks were observed, proving that the material purity met the standards. The detected atomic proportion of Dy was approximately 2%, which is basically consistent with the experimentally designed feed ratio of 2.5%, indicating that Dy ions were successfully incorporated into the SrGa2O4 lattice, and the doping process was stable and controllable.

[0041] Figure 5This is a fine XPS spectrum of Dy in SrGa2O4:2.5%Dy in Example 3. It can be clearly seen that the 4d orbital peak of Dy is located in the 129-135 eV range (the peak intensity is weak due to the low content, but it is still clearly identifiable), corresponding to Dy... 3+ The chemical state of Dy further confirms 3+ Doping was successful. The XPS spectra of other embodiments are similar to those of Embodiment 3, and will not be described again.

[0042] Figure 6 This is the photoluminescence (PL) spectrum of SrGa2O4:2.5%Dy in Example 3. The spectrum shows that at 300 K and 254 nm excitation, the material exhibits a dynamic "yellow → blue" luminescence process. At 0.05 s: the dominant light peak is yellow at 580 nm, corresponding to Dy... 3+ of 4 F 9 / 2 → 6 H 13 / 2 Energy level transitions occur; the 410 nm blue light peak represents intrinsic matrix emission; with increasing excitation time (1 s → 20 s), the intensity of the 580 nm yellow light gradually decreases, while the intensity of the 410 nm blue light gradually increases; after 20 s, the spectrum reaches a stable state, and blue light becomes the dominant emission—this phenomenon originates from the gradual filling of the trapping center by carriers after the 254 nm excitation, with the carrier concentration increasing from low to high, and the radiative recombination channel switching from the "yellow light channel" to the "blue light channel," consistent with the core regulatory mechanism. The room-temperature dynamic luminescence phenomena in other embodiments are similar to the above phenomena. Due to the influence of sample batches and testing errors, the highest peak of the yellow emission peak is located in the 560-610 nm range, and the highest peak of the blue emission peak is located in the 400-450 nm range.

[0043] By using a spectrometer to record the dynamic luminescence phenomenon of Example 3 in the temperature range of 300-520 K, it can be seen that as the temperature increases, the blue emission channel is gradually suppressed. The blue emission weakens at 300-420 K and disappears completely at 440-520 K, leaving only the yellow emission.

[0044] Figure 7 This is the high-temperature photoluminescence (PL) spectrum of SrGa2O4:2.5%Dy in Example 3. It shows that at 500 K and 254 nm excitation, the material only exhibits a gradual increase in yellow light intensity, with no blue light emission. From 0.05 s to 20 s, the intensity of the 580 nm yellow light peak gradually increases and reaches stability; no 410 nm blue light peak appears throughout. This is because significant thermal perturbation occurs at high temperature (500 K), and shallow-level trapping centers cannot stably store charge carriers (charge carriers are excited and lost due to heat). Only deep-level charge carriers can be trapped, and these deep-level charge carriers only radiate through the yellow light channel, thus completely closing the blue light channel. This confirms the regulatory effect of temperature on charge carrier distribution and the emission channel.

[0045] Figure 8 This is the thermoluminescence spectrum of SrGa2O4:2.5%Dy under different irradiation times at 254 nm ultraviolet light in Example 3. The SrGa2O4:2.5%Dy phosphor was charged in segments using 254 nm ultraviolet light for 3 s, 5 s, 7 s, 10 s, 20 s, 30 s, 40 s, 60 s, and 90 s, respectively. Subsequently, the temperature was linearly increased at a rate of 5 K / s within the range of 300-600 K, and the thermoluminescence intensity was recorded simultaneously. When the charging time is ≤10 s, the thermoluminescence peak is located at 440 K, and the peak area increases linearly with the charging time, indicating that the shallow trap level (0.88 eV) is gradually filled. When the charging time is ≥20 s, the peak area at 440 K tends to saturate, and a second thermoluminescence peak appears at 520 K, corresponding to the filling of the deep trap level (0.98 eV). After 70 s of ultraviolet light charging, the trap carrier concentration reaches saturation.

[0046] Figure 9 The thermoluminescence spectra of SrGa2O4:2.5%Dy in Example 3 at different temperatures are shown. All spectra exhibit a single symmetrical peak, and the peak temperature (Tm) shifts to the right as the charging temperature increases. As the charging temperature increases from 300 K to 500 K, the peak temperature of the thermoluminescence increases from 440 K to 460 K, corresponding to a trap level depth of 0.88-0.98 eV. This result confirms that increasing temperature deepens the trapping center level (increases Et) and weakens the carrier storage capacity (reduces TL intensity), which corroborates the phenomenon of "high temperature shutting down the blue light channel" in Example 6, further supporting the correlation mechanism between "carrier distribution and emission channel".

[0047] Figure 10 The schematic diagram of the pulsed ultraviolet light modulation device of SrGa2O4:2.5%Dy in Example 3 is shown. The device consists of three main modules: ① control module; ② excitation module; ③ detection module. This device can precisely control the "effective irradiation time" of 254 nm ultraviolet light by adjusting the pulse duty cycle, thereby regulating the charging rate of the captured central carriers and achieving controllable dynamic light emission rate, providing hardware support for subsequent pulsed light modulation experiments.

[0048] Figure 11This is the photoluminescence (PL) spectrum of SrGa2O4:2.5%Dy at a 10% duty cycle in Example 3. The SrGa2O4:2.5%Dy phosphor was excited using a pulsed 254 nm UV light source with a 10% duty cycle. The pulse period was 10 ms, the frequency was 100 Hz, and the LED driving circuit was controlled by an STM32 microcontroller. The phosphor was placed in a dark room, 2 cm away from the light source, and the emission spectrum from 350-750 nm was acquired in real time using a fiber optic spectrometer. Recordings were taken every 5 seconds for 300 seconds. The low duty cycle reduced the carrier accumulation rate, maintaining the yellow channel as the dominant emission and suppressing blue emission. After 120 seconds, the spectrum reached a stable state, with the peak locked at 580 nm, achieving slow, high-contrast yellow-to-yellow dynamic emission for delayed anti-counterfeiting labeling.

[0049] Figure 12 This is the photoluminescence (PL) spectrum of SrGa2O4:2.5%Dy in Example 3 at a 90% duty cycle. The spectrum shows that the material exhibits rapid "yellow → blue" dynamic emission. From 0 s to 40 s, the intensity of the yellow peak at 580 nm gradually decreases, while the intensity of the blue peak at 410 nm gradually increases. At 60 s, the spectrum reaches a stable state, and the blue and yellow light intensities are consistent with the stable state after 20 s of continuous light irradiation. This is because at a 90% duty cycle, the pulse light has a long "on-state" time, resulting in a fast carrier charging rate and rapid filling of the capture centers. Therefore, a stable blue color is achieved in 60 s, confirming the regulatory effect of the pulse duty cycle on the color change rate.

[0050] Figure 13 This describes the evolution of the fluorescence spectrum over time under synergistic irradiation with 254 nm and 365 nm ultraviolet light in Example 3. Initially, 254 nm sends electrons into shallow traps, while 365 nm simultaneously removes these electrons, deactivating the high-energy blue light channel. Charge carriers can only pass through deep traps, and the 580 nm yellow light rapidly intensifies and saturates within 0.1-1 s. Subsequently, 365 nm continuously "erases" the shallow traps, suppressing 410 nm matrix luminescence, resulting in a near-frozen spectral shape and intensity, with the color coordinates locked in the orange-yellow region. There is no yellow-to-blue transition within 20 s, and the afterglow is also pure yellow, directly demonstrating that the short-wavelength assisted removal strategy can block dynamic color changes, achieving programmable spectral locking and information encoding. After turning off the 365 nm light, the yellow-to-blue transition resumes.

[0051] Figure 14A small amount of SrGa2O4:0.025Dy powder was uniformly spread in a ceramic tray. First, it was irradiated with 254 nm UV light at room temperature for 10 s to complete the "writing" step, during which the powder exhibited a dynamic color change from yellow to blue. Then, the light source was turned off, and the tray was immediately moved to a 200 °C heating stage for 2 min of heat treatment. Thermal disturbance cleared the trapping centers, completing the "erasing" step, and the powder returned to its initial low-luminescence state. After natural cooling to room temperature, the same "writing" step was performed again. This "write-erasing" cycle was repeated four times. Experimental results showed that the color change time, saturation color coordinates, and afterglow intensity deviations were all less than 3% after four cycles, proving that the material structure exhibited no thermal fatigue and no decay in trap concentration. This implementation method can be directly used in reusable optical anti-counterfeiting labels or time-delay logic devices, ensuring long-term reliable service.

[0052] Figure 15 We thoroughly mixed the prepared phosphor material with a polydimethylsiloxane (PDMS) matrix to form a composite thin film pattern. The pattern was then verified in three stages: Stage 1 (initial charging, 3 s): After 3 s of 254 nm UV irradiation, the text pattern appeared yellow (dominated by 580 nm yellow light); Stage 2 (stable charging, 20 s): After 20 s of continuous irradiation, the pattern turned blue (dominated by 410 nm blue light); Stage 3 (afterglow modulation, after 365 nm irradiation): After turning off the 254 nm light, the initial afterglow of the pattern was blue; after 5 s of irradiation with 365 nm light, the afterglow turned yellow.

[0053] Figure 16 The optical sequential logic switch uses SrGa2O4:Dy phosphor as a physical carrier and utilizes its trap-controlled carrier competition mechanism to realize the response of "color state C" to dual-path ultraviolet inputs U (254 nm) and V (365 nm). Figure 16 The device's workflow is as follows: Initial state (0,0,0): Both UV lamps are off, the phosphor is not excited, and the output C=0 (non-blue). Only the 254 nm lamp is turned on (U=1, V=0), entering the "charging" stage: the carrier concentration increases over time, first filling the deep traps and emitting Dy. 3+ Yellow light; when the shallow trap is occupied, the matrix blue light channel opens, and the color changes from yellow to blue after about 20 seconds, C changes from 0 to 1, completing the "time delay" logic. At any time, turning on the 365 nm lamp (V=1) clears the shallow trap carriers, forcing them to recombine only through the deep traps. Blue light is suppressed, the color immediately returns to yellow, and C=0, achieving the "yellow lock" function; at this time, even if the 254 nm lamp is still on, the output remains C=0. After turning off the 365 nm lamp (V=0), the shallow trap is refilled, and C=1 is satisfied again after about 20 seconds; if the 254 nm lamp is turned off simultaneously, the trap charge gradually depletes, C remains 0, and the afterglow stage begins. Through the above steps, Figure 16 The following can be executed completely: (U,V)=(1,0)→1 is output after delay; (0,1) or (1,1) immediately outputs 0, thus completing the "AND-NOT-delay" compound logic within the same light-emitting pixel, which can be applied to optical computing, traffic priority control and multi-level encryption.

[0054] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multimodal dynamic photoluminescent material, characterized in that, a) It has a monoclinic crystal structure of SrGa2O4, space group P21 / c, and chemical composition SrGa2O4:xDy 3+ , where x = 0.01 - 0.05; b) When the material is excited by 254 nm ultraviolet light, it exhibits a dynamic photoluminescence change from yellow to blue as the irradiation time increases. The highest peak of the yellow emission peak is located in the 560-610 nm range, and the highest peak of the blue emission peak is located in the 400-450 nm range. c) The material has carrier trapping centers with a trapping level depth of 0.88-0.98 eV; d) The color of dynamic photoluminescence can be locked to yellow using 365 nm ultraviolet light; e) At 300-420 K, the blue emission channel is gradually suppressed as the temperature increases, and above 440 K, blue light is completely suppressed, leaving only yellow emission; f) After being charged with 254 nm ultraviolet light, the thermoluminescence spectrum of the material shows a single main peak, and the peak temperature increases from 440 K to 460 K as the charging temperature increases.

2. The material according to claim 1, characterized in that, The x=0.025 (i.e., Dy) 3+ With Sr 2+ The atomic ratio is 2.5%.

3. The material according to claim 1 or 2, characterized in that, The lattice constant of the material is located in the range of a = 8.36-8.40 Å, b = 9.00-9.01 Å, and c = 10.65-10.69 Å, and the unit cell volume factor Dy 3+ Replace Sr 2+ Slight shrinkage, no impurity phase.

4. The material according to claim 1 or 2, characterized in that... The yellow emission peak corresponds to Dy 3+ of 4 F 9 / 2 → 6 H 13 / 2 The energy level transition has a peak wavelength of 580 nm; the blue emission peak corresponds to the intrinsic emission of the SrGa2O4 matrix, with a peak wavelength of 410 nm.

5. The material according to claim 1 or 2, characterized in that... The energy level depth of the carrier trap is 0.88 eV at 300 K and 0.98 eV at 500 K, as determined by thermoluminescence. After the material is charged with 254 nm ultraviolet light for 70 s, the carrier concentration in the trap reaches saturation.

6. A method for preparing the material according to claims 1-5, comprising the following steps: a) Weigh out SrCO3 (purity ≥ 99.5%), Ga2O3 (purity ≥ 99.99%), and Dy(Ac)3·4H2O (purity ≥ 99.8%) according to the stoichiometric ratio, wherein the amount of Dy(Ac)3·4H2O used satisfies the ratio SrGa2O4:xDy 3+ In the middle, x = 0.01 - 0.05; b) Place the above ingredients in a mortar and grind manually for 30 minutes to ensure even mixing; c) Transfer the mixed powder to an alumina boat, place it in a box furnace, raise the temperature to 1350℃ at a rate of 5℃ / min, and hold for 6 h to carry out a high-temperature solid-phase reaction; d) After cooling the above materials to room temperature, the multimodal dynamic photoluminescent material SrGa2O4:xDy can be obtained. 3+ Powder.

7. The preparation method according to claim 6, characterized in that, The temperature control accuracy of the box furnace described in step c) is ±1 ℃, and the reaction process does not require a protective atmosphere, achieving pure phase synthesis in an air atmosphere.

8. A method for controlling multimodal dynamic photoluminescence, using the material described in claim 1 as a functional medium, characterized in that, The following regulatory methods are included: a) Pulsed ultraviolet light modulation: Excitation with 254 nm pulsed ultraviolet light (period 10 ms, frequency 100 Hz) with a duty cycle of 10%-90% is used. The dynamic yellow to blue time decreases as the duty cycle increases. b) Dual UV synergistic regulation: 254 nm UV light is used for charging while 365 nm UV light is superimposed to suppress the blue emission channel and achieve a dynamic change from dark yellow to bright yellow; after turning off the 365 nm light, the yellow-to-blue process is restored. c) Temperature control: The yellow-to-blue dynamic is maintained at 300 K (room temperature), blue emission is suppressed at 300-420 K, and blue emission disappears completely at 440-520 K, leaving only yellow emission; d) Cyclic regulation: After removing charge carriers by thermal excitation (temperature of 500 K), the dynamic luminescence performance can be reproduced under 254 nm ultraviolet light irradiation, and the above process can be repeated at least four times.

9. The control method according to claim 8, characterized in that, The material can be applied to multi-level anti-counterfeiting labels (which exhibit multi-color changes under different light / temperature conditions after patterning), optical sequential logic switches (which realize time-delay logic operations based on 254 nm / 365 nm optical switches), and intelligent optoelectronic devices.

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