Rare-earth doped Y 2 O 3 -Au composite nanomaterials for use as non-volatile self-encrypting all-optical memories

Abstract

The present invention discloses the use of a rare-earth doped Y2O3-Au composite nanomaterial as a non-volatile self-encrypting all-optical memory. By utilizing the strong light confinement and ultrafast thermal response characteristics of the localized surface plasmon resonance effect, non-volatile self-encrypting all-optical storage based on the rare-earth doped Y2O3-Au composite nanomaterial is achieved. When changing the excitation light power, the crystal can quickly switch between two stable luminescent states, and there is an ultra-high luminescence switching contrast (10 4 ) between the two states. By simply changing the intensity of the irradiation light, all processes of writing, reading, erasing, and encrypting optical information can be achieved. Not only does it not require the switching of light sources with multiple frequencies and the erasing process of electric heating, but the encryption of information can be completed simultaneously when the information is written, thus avoiding additional encryption steps. And only when the frequency and power density of the light strictly meet the predetermined conditions can the stored information be effectively read out, which can improve the security of data encryption and anti-counterfeiting.

Description

Technical Field

[0001] The present invention belongs to the technical field of rare earth ion-doped inorganic luminescent materials, and particularly relates to the use of a composite material composed of plasmonic gold nanoparticles and rare earth-doped oxide single crystals in self-encrypted optical information storage. Background Art

[0002] With the rapid development of information science, the unstructured data connected to the Internet has shown exponential growth. In response to the challenges of data security and the speed mismatch between memory units and processors, there is an urgent need for secure, reliable, and fast memory devices. Inspired by the characteristics of human memory, materials that respond to multiple stimuli (such as electric fields, magnetic fields, and mechanical fields) and can quickly switch between two stable states (providing "0" and "1") have attracted great interest from researchers because they can be used to achieve binary information storage. Compared with various electronic and magnetic response materials, photo-stimulated response devices have an ultra-fast operating speed and low power consumption, and are considered to be the most promising next-generation memory, with the potential to realize on-chip neuromorphic devices.

[0003] Rare earth ion-doped inorganic luminescent materials have excellent characteristics such as a rich linear energy level structure, full-spectrum coverage fluorescence emission in the ultraviolet-visible-infrared region, and stable physical and chemical properties. Different from the broadband fluorescence radiation caused by interband transitions in semiconductor quantum dots, the luminescence of trivalent rare earth ions is based on the transition of 4f electrons within the f-f configuration. In 5 S 2 、 5 P 6 Under the shielding effect of the electron shell, the energy level position of the 4f shell electrons is insensitive to the external environment, and stable linear emission spectra can be generated by electron transitions. In addition, the energy level structure of rare earth ions is extremely rich, and tunable emission from ultraviolet light to near-infrared can be achieved by selecting appropriate doping ions and regulating the luminescence process. Rare earth ion-doped inorganic luminescent materials are widely used in many fields such as light-emitting diodes, biomedicine, solar cells, sensors, and displays. In particular, yttrium oxide crystals doped with rare earth ions have extremely narrow emission peaks and ultra-high physical and chemical stability, and are a very practical luminescent material, and their application ranges include photonics, quantum information processing, laser media, protective coatings, scintillators, and phosphors, etc.

[0004] If yttrium oxide crystals doped with rare earth ions can be used for optical information storage, it will contribute to the development of a new generation of all-optical memories and optical anti-counterfeiting technologies. However, this application still faces a series of challenges. The primary problem is the effective combination of the stimulus-responsive function and the luminescence of rare earth ions. Some researchers have attempted to achieve the photochromic properties of rare earth-doped luminescent materials by means of energy exchange or electron transfer between the matrix material and the luminescent ions. However, existing photochromic materials doped with rare earth ions have problems such as poor crystallinity or lattice mismatch between the rare earth ions and the matrix material, which prevent the superior luminescence properties of rare earth ions, such as narrow linewidth and high intensity, from being manifested, resulting in a low luminescence switching contrast and limiting the resolution and signal-to-noise ratio of information reading. This has become a major problem restricting the use of rare earth ion-doped luminescent materials for information storage. Secondly, when existing rare earth-doped photochromic materials are used for information storage, the information reading is achieved based on the difference in luminescence color, which not only involves the counting of emitted photons but also the conversion calculation of photon energy, complicating the information reading. Thirdly, in existing methods, in order to achieve reversible writing and reading of photochromic material information, irradiation with light of different frequencies is required and information erasure is carried out using electrical heating, and a truly single-frequency all-optical memory cannot be achieved. Therefore, a new, convenient and efficient all-optical strategy is needed to combine the stimulus-responsive function with rare earth luminescence.

[0005] CN 108866625 A discloses a method for in-situ rapid synthesis of rare earth-doped oxide single crystals. This method utilizes the thermal effect of Au nanostructure plasmons, uses small-sized Au nanoparticles with a large absorption cross-section as a heat source, and through the action of an external optical field with a resonant wavelength, causes the Au nanoparticles to generate extremely high heat in an extremely short time and conduct it to NaYF 4 :Eu 3+ sub-micron crystals, causing their local temperature to rise instantaneously; at the same time, the hot electrons generated by the relaxation of surface plasmons catalyze the oxygen molecules adsorbed on their surface, activating the oxygen molecules, thereby promoting the oxidation reaction of the luminescent material. Under the dual action of the instantaneous high temperature and the activated oxygen, the luminescent material instantaneously transforms into Y 2 O 3 :RE 3+ single crystals (RE 3+ represents Eu 3+ or Yb 3+ / Er 3+ ), and a Y 2 O 3 :RE 3+ -Au composite nanomaterial is obtained. Summary of the Invention

[0006] The object of the present invention is for the above Y 2 O 3 :RE 3+The Y:RE-Au composite nanomaterial provides a new application.

[0007] Actually, the present invention relates to the 2 Y 3 O 3+ :RE-Au composite nanomaterial for use as a non-volatile self-encrypting all-optical memory.

[0008] The above-mentioned rare-earth-doped Y 2 O 3 -Au composite nanomaterial is prepared by the following steps:

[0009] (1) Coating rare-earth-doped luminescent materials with Au nanoparticles

[0010] Add the rare-earth-doped luminescent materials to deionized water, add a reducing agent, ultrasonically stir at room temperature for 5 - 20 minutes, heat to 60 - 90 °C, then add a silane coupling agent, continue to heat to 90 - 100 °C, and then add an aqueous solution of chloroauric acid with a concentration of 0.01 - 0.1 mol / L, react at a constant temperature for 10 - 30 minutes, naturally cool, centrifuge, wash, and dry to obtain rare-earth-doped luminescent materials coated with Au nanoparticles; wherein, the rare-earth-doped luminescent materials are YF 3 :RE 3+ submicron crystals or NaYF 4 :RE 3+ submicron crystals, and RE 3+ represents Eu 3+ or Yb 3+ / Er 3+ , the reducing agent is any one of sodium citrate, citric acid, ascorbic acid, oxalic acid, sodium borohydride, and ethylene glycol; the silane coupling agent is any one of 3-aminopropyltrimethoxysiloxane, (methacryloyloxy)propyltrimethoxysilane, and vinyltriethoxysilane;

[0011] (2) Phase transformation of rare-earth-doped luminescent materials into rare-earth-doped oxide single-crystal nanoparticles

[0012] Irradiate the rare-earth-doped luminescent materials coated with Au nanoparticles with a laser for 0.5 milliseconds to 3 seconds, the laser wavelength is coupled with the wavelength of the surface plasmon resonance peak of the Au nanoparticles, and the laser power density is 5.0×10 3 to 1.0×10 6 W / cm 2 , to obtain the rare-earth-doped Y 2 O 3 -Au composite nanomaterial.

[0013] The rare-earth-doped Y 2 O 3In the -Au composite nanomaterial, the ionic transition energy levels of the doped rare earth luminescent ions and the surface plasmon resonance of the Au nanoparticles need to be coupled with the frequency of the excitation light simultaneously. The frequency and power density of the information reading light should be the same as those of the laser used to induce the transformation of the rare earth doped luminescent material into rare earth doped oxide.

[0014] Under the irradiation of 532 nm continuous light, the present invention realizes the catalytic oxidation and structural transformation of NaYF 4 :Eu 3+ and YF 3 :Yb 3+ / Er 3+ submicron crystals by means of the surface plasmon thermal effect of small-sized Au nanoparticles, and obtains Y 2 O 3 :Eu 3+ -Au or Y 2 O 3 :Yb 3+ / Er 3+ -Au composite nanomaterials, and simultaneously writes the frequency and power information of the irradiation light into the composite nanomaterials. The Y 2 O 3 :RE 3+ -Au composite nanomaterials exhibit excellent luminescence modulation and high sensitivity response to frequency and light intensity, and this property can be used for dual encryption of optical information. When the frequency and power of the reading light are the same as those of the writing light, due to the highly efficient local thermal effect of surface plasmons, the luminescence of the Y 2 O 3 :RE 3+ -Au composite nanomaterials is almost completely quenched. When the power of the reading light is less than that of the writing light, due to the enhancement effect of the surface plasmon electromagnetic field on the light emission of rare earth ions, the composite nanomaterials exhibit high-intensity red light emission. Therefore, during the information reading process, by controlling the intensity of the excitation light, the reversible switching of the composite nanomaterials between the luminescence enhancement state ("1") and the luminescence quenching state ("0") can be realized, and the contrast ratio is as high as 10 4 . Secondly, through the irradiation of higher power light, the optical information written in the composite nanomaterials can be erased and rewritten. During the rewriting process, the composite nanomaterials will undergo self-adaptive adjustment of the structure, resulting in changes in its photothermal conversion efficiency, so that the material can only respond to the new power intensity and reach the luminescence quenching state, while the original optical power information is erased.

[0015] From the above results, the advantages of the present invention can be obtained as follows:

[0016] When the present invention changes the power of the excitation light, it can realize the rapid switching between two stable luminescence states, and there is an ultra-high luminescence switching contrast ratio (104 ) By changing the intensity of the irradiation light, the entire process of writing, reading, erasing, and encrypting optical information can be achieved. Not only is it unnecessary to switch light sources of multiple frequencies and perform the erasing process by electric heating, but also the encryption of information can be completed simultaneously during information writing, thus avoiding additional encryption steps. And only when the frequency and power density of the light strictly meet the predetermined conditions can the stored information be effectively read out, realizing dual-encrypted binary optical information storage, which can improve the security of data encryption and anti-counterfeiting. The present invention solves the main problems hindering the application of rare-earth doped materials in optical information storage and provides a brand-new solution for the development of self-encrypting all-optical memories. Description of the Drawings

[0017] Figure 1 is the TEM image and element distribution map of the NaYF 4 :Eu 3+ @Au submicron crystals in Example 1.

[0018] Figure 2 is the TEM image and element distribution map of the Y 2 O 3 :Eu 3+ -Au submicron crystals in Example 1.

[0019] Figure 3 is the fluorescence spectrum of the Y 2 O 3 :Eu 3+ -Au submicron crystals excited by a 532 nm laser in Example 1.

[0020] Figure 4 is the fluorescence spectrum of the Y 2 O 3 :Eu 3+ -Au submicron crystals excited by a 633 nm laser in Example 1.

[0021] Figure 5 is the dependence of the fluorescence radiation intensity on the excitation light power of the Y 2 O 3 :Eu 3+ -Au submicron crystals with written optical information (532 nm, 24.5 mW) excited by a 532 nm laser in Example 1.

[0022] Figure 6 is the dependence of the fluorescence radiation intensity on the excitation light power of the Y 2 O 3 :Eu 3+ -Au submicron crystals with written optical information (532 nm, 12 mW) excited by a 532 nm laser in Example 1.

[0023] Figure 7 is the dependence of the fluorescence radiation intensity of Y 2 O 3 :Eu 3+ -Au submicron crystals on the excitation light power under 532nm laser excitation.

[0024] Figure 8 is the resolution of the luminescence switching behavior of Y 2 O 3 :Eu 3+ particles when the reading light approaches the writing light power. In the information writing step, the laser power of 532nm is fixed at 1mW, 12mW and 24.5mW, while in the information reading step, the power gradually increases from 0.01 to 24.5mW.

[0025] Figure 9 is the dependence of the fluorescence radiation intensity of Y 2 O 3 :Eu 3+ submicron crystals on the excitation light power under 532nm laser excitation.

[0026] Figure 10 is the SEM image and the corresponding luminescence image of Y W1 and P W2 Y 2 O 3 :Eu 3+ -Au submicron crystals when the writing power is P W1 .

[0027] Figure 11 is the information reading result under different reading power conditions; P 1 and P 2 are the irradiation light powers (P 1 <P 2 ) when binary information is written, and P is the excitation light power when information is read.

[0028] Figure 12 is to achieve reproducible luminescence switching between the enhanced state and the quenched state of Y 2 O 3 :Eu 3+ -Au by adjusting the power of the reading light.

[0029] Figure 13 is the TEM image and the elemental distribution map of YF 3 :Yb 3+ / Er 3+ -Au submicron crystals in Example 2.

[0030] Figure 14is Y in Example 2 2 O 3 :Yb 3+ / Er 3+ -Au submicron crystal TEM images and elemental distribution maps.

[0031] Figure 15 is Y in Example 2 2 O 3 :Yb 3+ / Er 3+ -Au submicron crystal fluorescence spectra under 980 nm laser excitation.

[0032] Figure 16 is Y in Example 2 2 O 3 :Yb 3+ / Er 3+ -Au submicron crystal schematic diagram of the Er 3+ transition and absorption spectra of Au nanoparticles under 532 nm laser excitation.

[0033] Figure 17 is Y in Example 2 2 O 3 :Yb 3+ / Er 3+ -Au submicron crystal fluorescence spectra under 532 nm laser excitation. Specific implementation manners

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0035] Example 1

[0036] Y 2 O 3 :Eu 3+ -Au composite nanomaterial as an application for a non-volatile self-encrypting all-optical memory

[0037] 1. Coating of NaYF 4 :Eu 3+ submicron crystals with Au nanoparticles

[0038] Add 0.95 mL of 0.5 mmol / L Y(NO 3 ) 3 aqueous solution and 0.05 mL of 0.5 mmol / L Eu(NO 3 ) 3An aqueous solution, 7 mL of 0.5 mmol / L NaF aqueous solution, was stirred at room temperature for 60 minutes, then heated to 75 °C and reacted at a constant temperature for 2 hours. After natural cooling, it was centrifugally washed with deionized water and anhydrous ethanol in sequence, and dried at 60 °C for 10 hours to obtain flower-shaped NaYF with a particle size distribution of about 500 nm and good monodispersity. 4 :Eu 3+ Sub-micron crystals. 0.03 g (0.16 mmol) of NaYF 4 :Eu 3+ Sub-micron crystals were added to 40 mL of deionized water, and 1.4 g (7.28 mmol) of trisodium citrate was added. After ultrasonic treatment at room temperature for 10 minutes, the temperature was raised to 70 °C, 30 μL (0.167 mmol) of 3-aminopropyltrimethoxysilane was added, and the temperature was further raised to 90 °C. Then 3 mL of 0.01 mol / L chloroauric acid aqueous solution was added, and the reaction was carried out at a constant temperature for 15 minutes. After natural cooling, it was centrifugally washed with deionized water and anhydrous ethanol in sequence, and dried at 60 °C for 10 hours to obtain NaYF 4 :Eu 3+ Sub-micron crystals coated with Au nanoparticles, namely NaYF 4 :Eu 3+ @Au sub-micron crystals. As can be seen from Figure 1 Figure 1, the particle size of the Au nanoparticles is about 8 - 10 nm, and they are uniformly and densely adhered to the surface of the NaYF 4 :Eu 3+ Sub-micron particles. Before and after coating with Au nanoparticles, NaYF 4 Both show a cubic phase.

[0039] 2. Transformation of NaYF 4 :Eu 3+ to Y 2 O 3 :Eu 3+

[0040] Using continuous light at 532 nm (coupled with the wavelength of the plasmon resonance peak of Au nanoparticles) as the irradiation light source, a single NaYF 4 :Eu 3+ @Au sub-micron crystal was irradiated for 0.5 s to obtain a Y 2 O 3 :Eu 3+ -Au composite nanomaterial with light-stimulus response function, and at the same time, the triggering conditions of the light switch were written into it. In the obtained Y 2 O 3 :Eu 3+ -Au composite nanomaterial, Y 2 O 3 :Eu 3+are spherical cubic single-crystal nanoparticles with a particle size of about 300 nm, and the Au nanoparticles embedded on their surface have a particle size between 25 and 80 nm( Figure 2 ). While the particles are transformed, the information of the irradiated light (λw = 532 nm and power Pw) is written into the composite structure and serves as the trigger condition for luminescence conversion when information is read.

[0041] 3. Y 2 O 3 :Eu 3+ -Au Composite Nanomaterials' Frequency Encryption Characteristics of Luminescence Switching Behavior

[0042] To verify the frequency encryption characteristics of the luminescence switching behavior, Y 2 O 3 :Eu 3+ -Au composite nanomaterials were selected as the luminescent crystal, and the particles were written with the same light (λw = 532 nm, Pw = 20 mW). Lights of 532 nm and 633 nm were selected as the excitation lights for information reading to study the down-conversion luminescence of Y 2 O 3 :Eu 3+ -Au composite nanomaterials. Y 2 O 3 :Eu 3+ -Au composite nanomaterials show high-efficiency red luminescence under the excitation of low-power (2 mW) light at 532 nm( Figure 3 ). Especially at the electric dipole( 7 F 0 → 5 D 2 ) transition at 611 nm, it not only significantly enhances but also shows an emission with a narrow line width (FWHM = 1.1 nm) and high color purity. In contrast, when the reading light is strictly close to the writing light power of 20 mW, the luminescence of the particles is almost completely quenched. The light intensities read at the two powers show an extremely high luminescence contrast, with a ΔR value of 99.9% (ΔR = (R 0 -R t ) / R 0 , where R 0 and R t are the luminescence intensities in the luminescence enhancement and quenching states, respectively). The luminescence switching contrast is an important parameter for evaluating information reading, and a high contrast can ensure the accuracy of data reading. When using the light of 633 nm to excite the particles to read information, due to the mismatch between the laser energy and the energy difference between the ground state and the excited state of the luminescence center, the transition of rare-earth ions cannot be effectively excited, so the particles do not emit fluorescence, and no switching of luminescence enhancement and quenching is observed when the light power is changed( Figure 4)。Only when the frequency of the excitation light is coupled with both the plasmon resonance and the transition energy levels of the luminescent ions can the efficient switching between the luminescence enhancement and quenching states be achieved under excitation lights of different powers, and the stored information can be successfully read out.

[0043] 4. Y 2 O 3 :Eu 3+ Power Encryption Characteristics of the Luminescence Switching Behavior of Y

[0044] By tracking the evolution of the luminescence intensity of the particles after photoexcitation with different powers, the power encryption characteristics of the luminescence switching behavior of Y 2 O 3 :Eu 3+ -Au composite nanomaterials were studied. Using light with a wavelength of 532 nm and powers of 24.5 mW, 12 mW, and 1 mW as the writing light, three types of Y 2 O 3 :Eu 3+ -Au nanoparticles were obtained, and the variation of their luminescence intensity with the reading light power is as Figures 5 - 7 shown. As the reading light power increases, the luminescence of each particle shows a similar variation trend, that is, it first becomes stronger and then weaker. When the reading light reaches a specific intensity, the particle hardly luminesces, that is, it switches to the luminescence quenching state. It can be seen that the triggering powers of the quenching state and the enhancement state of these particles are different, and the triggering power of the quenching state is exactly equal to the power of the writing light. That is to say, the switching power is determined during the information writing process. At the same time, when the power of the reading light approaches the switching power, the luminescence state is super-sensitive to the power of the reading light. From Figure 8 we can see that for the particles written with 24.5 mW, when the reading power changes from 24 mW to 24.5 mW, a luminescence switching contrast of 94.5% can be obtained. That is to say, the luminescence efficiency of Y 2 O 3 :Eu 3+ -Au composite nanomaterials does not depend on the absolute intensity of the excitation light, but on its intensity relative to the writing light. This unique property is not possessed by Y 2 O 3 :Eu 3+ -Au composite nanomaterials prepared by conventional methods ( Figure 9 ).

[0045] 5. Y 2 O 3 :Eu 3+ Self-Encrypted Binary Information Storage of Y

[0046] Y 2 O 3:Eu 3+ The characteristic of the Eu-Au composite nanomaterial that can rapidly switch between the enhanced state and the quenched state (providing "1" and "0") can be used to achieve self-encrypted binary information storage. In the information writing step, lights with powers of P w1 and P w2 (P w1 <P w2 ) are used to obtain two Y 2 O 3 :Eu 3+ -Au composite nanoparticles, and the information of P w1 and P w2 are written into them respectively. When reading the information, the light with power of P w1 is selected as the excitation light to excite the luminescence of Eu 3+ and the surface plasmon resonance of Au nanoparticles. As can be seen from Figure 10 , using lights with powers of P w1 and P w2 as the writing lights, uniform spherical Y 2 O 3 :Eu 3+ -Au composite nanoparticles are obtained. Under the excitation of the reading light with power of P w1 , the two composite nanoparticles respectively exhibit obvious luminescence enhancement ("1") and quenching ("0") states. It should be noted that only at a specific reading light power (equal to the lower one of the two writing light powers, P r = P W1 ), can the written information be successfully read. When the reading light power (P r ) is less than the lower one of the two writing light powers (P r <P W1 ), both particles show the luminescence enhancement state, and the read information is (1,1), rather than the written information (1,0) ( Figure 11 ). When the reading light power is greater than P W1 and less than P W2 (P W1 <P r <P W2 ), the read information is also (1,0), but the light intensity information written in the particles will be rewritten. If the light with power of P W1 is used in subsequent readings, it will present (1,1). When reading with light with power greater than P W2 , both particles will present the quenched state (0,0), and the two data points will be damaged. In subsequent reading steps, when the reading light power is not less than P W2 , the information will be read as (0,0), and when the reading light power is less than P W2When the information will be read as (1, 1). Therefore, for information reading, there are strict requirements not only for the frequency of the excitation light but also for its intensity, which means that the information is successfully encrypted during data writing. By controlling the intensity of the excitation light, a periodic and stable luminescence switch with high contrast (10 4 ) can be achieved. Figure 12 ) This strategy not only does not require additional steps for information encryption but also enables double encryption of data.

[0047] Example 2

[0048] YF 3 :Yb 3+ / Er 3+ -Au composite nanomaterials for use as non-volatile self-encrypting all-optical memories

[0049] 1. Au nanoparticles coated on YF 3 :Yb 3+ ,Er 3+ submicron crystals

[0050] Add 0.95 mL of 0.5 mmol / L Y(NO 3 ) 3 aqueous solution and 0.04 mL of 0.5 mmol / L Yb(NO 3 ) 3 and 0.01 mL of 0.5 mmol / L Er(NO 3 ) 3 aqueous solution, 3 mL of 0.5 mmol / L NaF aqueous solution. In a 75 °C environment, react at a constant temperature for 2 hours, cool naturally, and wash by centrifugation with deionized water and absolute ethanol in turn, and dry at 60 °C for 10 hours to obtain YF 3 :Eu 3+ submicron crystals. Add 0.03 g (0.2 mmol) of YF 3 :Yb 3+ ,Er 3+ submicron crystals to 40 mL of deionized water, add 1.4 g (7.2 mmol) of trisodium citrate, sonicate at room temperature for 10 minutes, then raise the temperature to 70 °C, add 30 μL (0.167 mmol) of 3-aminopropyltrimethoxysilane, continue to raise the temperature to 90 °C, then add 3 mL of 0.01 mol / L chloroauric acid aqueous solution, react at a constant temperature for 15 minutes, cool naturally, and wash by centrifugation with deionized water and absolute ethanol in turn, and dry at 60 °C for 10 hours to obtain Au nanoparticles coated on YF 3 :Yb 3+ / Er 3+ submicron crystals, namely YF 3 :Yb3+ / Er 3+ @Au submicron crystals.

[0051] 2. YF 3 :Yb 3+ / Er 3+ @Au is transformed into Y 2 O 3 :Yb 3+ / Er 3+ -Au

[0052] This step is the same as the operation of NaYF 4 :Eu 3+ transformed into Y 2 O 3 :Eu 3+ in Example 1, and YF 3 :Yb 3+ / Er 3+ -Au composite nanomaterials are obtained.

[0053] 3. Frequency encryption characteristics of the luminescence switching behavior of Y 2 O 3 :Yb 3+ / Er 3+ -Au composite nanomaterials

[0054] To verify the frequency encryption characteristics of the luminescence switching behavior, YF 3 :Yb 3+ / Er 3+ -Au composite nanomaterials are selected as luminescent crystals, and the particles are written with the same light (λw = 532 nm, Pw = 20 mW). Lights of 532 nm and 980 nm are selected as the excitation lights for information reading, and the down-conversion and up-conversion luminescence of Y 2 O 3 :Yb 3+ / Er 3+ -Au composite nanomaterials are studied. When the excitation light is tuned to 532 nm, regardless of whether the power of the excitation light is close to the power of the writing light, the particles always show efficient up-conversion luminescence, and power-dependent luminescence switching cannot be obtained ( Figure 15 ). When the excitation light is tuned to 980 nm, its energy matches the energy gap of Er 3+ ( 4 I 15 / 2 → 4 H 11 / 2 ) and simultaneously matches the surface plasmon resonance of Au nanoparticles ( Figure 16 ), Y 2 O 3 :Yb 3+ / Er 3+-Au nanoparticles show high-efficiency down-conversion emission ([ Figure 17 ]) under low-power (2 mW, P r <P W ) optical excitation at 532 nm. In contrast, when the reading light is strictly close to the power of the writing light, 20 mW (P Figure 17 )), the luminescence of the particles is almost completely quenched. That is to say, when the reading light is 532 nm, Y r =P W ), the Y 2 O 3 :Yb 3+ / Er 3+ -Au composite nanomaterials exhibit obvious power-dependent luminescence switching behavior.

[0055] Y 2 O 3 :Yb 3+ / Er 3+ -Au composite nanomaterials: Verification and implementation examples of the power encryption characteristics of the luminescence switching behavior and self-encrypted binary information storage.

Claims

1. Use of rare earth-doped Y 2 O 3 -Au composite nanomaterials as non-volatile self-encrypting all-optical memories, wherein the rare earth-doped Y 2 O 3 -Au composite nanomaterials are prepared by the following steps: (1) Rare earth-doped luminescent materials coated with Au nanoparticles Add the rare earth-doped luminescent materials into deionized water, and add a reducing agent. After ultrasonic treatment at room temperature for 5 - 20 minutes, heat it to 60 - 90 °C, then add a silane coupling agent, continue to heat up to 90 - 100 °C, and then add an aqueous solution of chloroauric acid with a concentration of 0.01 - 0.1 mol / L. React at a constant temperature for 10 - 30 minutes, cool naturally, centrifuge, wash, and dry to obtain the rare earth-doped luminescent materials coated with Au nanoparticles; Among them, The rare earth-doped luminescent material is YF 3 :RE 3+ submicron crystals or NaYF 4 :RE 3+ submicron crystals, where RE 3+ represents Eu 3+ or Yb 3+ / Er 3+ , and the reducing agent is any one of sodium citrate, citric acid, ascorbic acid, oxalic acid, sodium borohydride, and ethylene glycol; the silane coupling agent is any one of 3-aminopropyltrimethoxysiloxane, (methacryloyloxy)propyltrimethoxysilane, and vinyltriethoxysilane; (2) Rare earth-doped luminescent materials are transformed into rare earth-doped oxide single crystal nanoparticles Irradiate the rare earth-doped luminescent material coated with Au nanoparticles with a laser for 0.5 milliseconds to 3 seconds. The laser wavelength is coupled with the wavelength of the surface plasmon resonance peak of the Au nanoparticles, and the laser power density is 5.0×10 3 ~1.0×10 6 W / cm 2 to obtain a rare earth-doped Y 2 O 3 -Au composite nanomaterial; When the frequency and power of the read light are the same as those of the write light, due to the highly efficient local thermal effect of the plasmon, the luminescence of the rare-earth-doped Y 2 O 3 -Au composite nanomaterial is almost completely quenched; while when the power of the read light is less than that of the write light, due to the enhancement effect of the plasmon electromagnetic field on the light emission of rare-earth ions, the composite nanomaterial exhibits high-intensity red light emission; during the information reading process, by controlling the intensity of the excitation light, the reversible switching of the composite nanomaterial between the luminescence enhancement state "1" and the luminescence quenching "0" state can be achieved; through the irradiation of higher-power light, the written optical information in the composite nanomaterial can be erased and rewritten again; and only when the frequency and power density of the light strictly meet the predetermined conditions can the stored information be effectively read out.

2. Use of the rare earth-doped Y 2 O 3 -Au composite nanomaterial as a non-volatile self-encrypting all-optical memory It is characterized in that The ion transition energy levels of the rare earth luminescent ions doped in the composite nanomaterials and the surface plasmon resonance of the Au nanoparticles need to be coupled with the frequency of the excitation light at the same time. The frequency and power density of the information reading light should be the same as the laser used to induce the transformation of the rare earth-doped luminescent materials into rare earth-doped oxides in step (2) of claim 1.

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