Deep anti-counterfeiting materials induced by upconversion luminescence temperature and their applications

Abstract

The deep anti-counterfeiting material based on upconversion luminescence temperature induction provided by the present invention and its application include two kinds of core-shell structure nanoparticles with high doping of lanthanide rare earth ions having different temperature dependences on upconversion luminescence. One is a temperature-sensitive nanoparticle with a structure of a luminescent center core - an active sensitizing shell - an inert protective shell, and the other is a temperature-insensitive nanoparticle with a structure of a luminescent center core - an inert protective shell. The temperature-sensitive nanoparticles are coated to form a hidden information layer, and the temperature-insensitive nanoparticles are coated to form a covering protective layer. The pattern made of this anti-counterfeiting material is completely invisible under natural light. At room temperature, it presents a completely blurred glare under near-infrared laser irradiation. Under near-infrared laser irradiation in a low-temperature environment, the true information is decoded and presented. When the temperature returns to room temperature, the true information is hidden again. The present invention has a repeatable and reversible hiding and decoding process, realizing deep anti-counterfeiting protection for important information.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoluminescence anti-counterfeiting, and particularly relates to the application of lanthanide ion highly doped upconversion luminescent nanomaterials in deep optical anti-counterfeiting related to temperature. Background Art

[0002] With the development of social economy and technology, the phenomenon of counterfeiting and shoddy products has become increasingly serious in many fields, such as food, art, medicine, and currency. The existence of counterfeit products not only damages the interests of consumers but also causes huge economic losses to society. Therefore, in order to effectively block the spread of counterfeit products, it is urgent to develop more advanced anti-counterfeiting materials and improve the anti-counterfeiting technology level. Traditional anti-counterfeiting technologies have been applied on a large scale in the market, but their anti-counterfeiting modes are single and easy to be counterfeited, making it difficult to achieve good anti-counterfeiting effects in practical applications. Based on this background, fluorescence anti-counterfeiting technology has attracted wide attention due to its excellent fluorescence intensity, extremely high concealment and confidentiality, complex coding patterns, etc., and has gradually become one of the commonly used anti-counterfeiting technologies.

[0003] Optical materials such as organic dyes, semiconductor quantum dots, and lanthanide upconversion luminescent nanoparticles have been confirmed by researchers to be applicable to the development of fluorescence anti-counterfeiting technology. Compared with organic dye and semiconductor quantum dot materials, lanthanide element-doped upconversion nanoparticles can convert near-infrared excitation into ultraviolet or visible light emission, and have advantages such as long fluorescence lifetime, narrow emission band, adjustable spectrum, good photochemical stability, no photo-bleaching, high processability, and convenient surface functionalization, and have a more extensive application prospect in the field of fluorescence anti-counterfeiting.

[0004] At present, certain achievements have been made in fluorescence anti-counterfeiting technology based on rare earth element-doped upconversion luminescent materials. Existing upconversion fluorescence anti-counterfeiting methods include: regulating the wavelength and power density of near-infrared excitation light, regulating fluorescence emission color, irradiation time, pH stimulus response, etc. However, these anti-counterfeiting schemes of rare earth-doped upconversion fluorescence materials are all carried out at room temperature, and the anti-counterfeiting mode is relatively single. With the continuous iteration and update of forgery technologies, in order to meet higher anti-counterfeiting requirements in different scenarios, people still need to continuously develop more advanced and deeper multi-dimensional optical anti-counterfeiting materials in this field.

[0005] In order to solve the above technical problems, the present invention introduces the dimension of temperature into the anti-counterfeiting technical solution, increases the anti-counterfeiting level, and develops a deep anti-counterfeiting technology based on rare earth element-doped upconversion luminescent materials under low-temperature regulation, realizing a higher degree of protection for hidden information, which is of great significance for multi-dimensionally improving the anti-counterfeiting level. Summary of the Invention

[0006] The deep anti-counterfeiting material based on upconversion luminescence temperature induction provided by the present invention comprises two kinds of core-shell structure nanoparticles with high doping of lanthanide rare earth ions having different temperature dependences on upconversion luminescence. One is a temperature-sensitive nanoparticle with a structure of a luminescence center core - an active sensitization shell - an inert protection shell, and the other is a temperature-insensitive nanoparticle with a structure of a luminescence center core - an inert protection shell;

[0007] The luminescence center core is a host matrix doped with an activator, and the activator includes Ho 3+ or Er 3+ , and the doping concentration is 20% - 100% in mole percentage;

[0008] The active sensitization shell is a host matrix doped with a sensitizer, and the sensitizer includes Yb 3+ , and the doping concentration is 0 - 100% in mole percentage;

[0009] The host matrix is NaYF4, NaLuF4 or NaGdF4;

[0010] The inert protection shell is NaYF4, NaLuF4 or NaGdF4;

[0011] In the temperature-insensitive nanoparticle, an energy trapping center ion is further doped in the luminescence center core, and the energy trapping center ion includes Tm 3+ .

[0012] Preferably, in the temperature-insensitive nanoparticle, the doping concentration of Tm 3+ is 0.5% in mole percentage.

[0013] Preferably, the preparation of the temperature-sensitive nanoparticle with a structure of a luminescence center core - an active sensitization shell - an inert protection shell according to the present invention comprises the following steps:

[0014] (1) Preparation of the luminescence center core

[0015] Dissolve the activator hydrated chloride in oleic acid and 1-octadecene in a three-necked flask; deoxygenate under continuous protection of argon, and heat to 150 °C and maintain for at least 30 minutes to obtain a precursor solution;

[0016] When the above solution is cooled to room temperature, add a methanol solution containing NaOH and NH4F, then heat to 80 °C to remove the methanol in the system; then gradually raise the temperature to 300 - 320 °C, stir and maintain for at least 90 minutes to form a luminescence core; the doping concentration of the activator is 100% in mole percentage;

[0017] When the above solution is cooled to room temperature, centrifuge and wash ultrasonically with ethanol and cyclohexane, and finally disperse the centrifuged nanoparticles in cyclohexane to form a luminescence core solution.

[0018] (2) Preparation of luminescent center core - active sensitizing shell

[0019] Add CF3COONa and (CF3COO)3Yb with a molar ratio of 1:1 into a three - necked flask; add OA and ODE, heat the mixture to 120 °C under an argon atmosphere and stir to dissolve the solid and remove residual water, then cool to room temperature and collect as the NaYbF4 active shell precursor;

[0020] Take the core solution obtained in the above step (1) and add it to a three - necked flask containing OA and ODE, remove cyclohexane in the system at 80 °C; under argon protection, heat the solution to 300 °C, then inject the NaYbF4 precursor in portions, with a molar ratio of core to precursor of 1:3.6, and react to form the corresponding epitaxial shell; the doping concentration of the sensitizer is 100 mol%;

[0021] Cool the mixture to room temperature, centrifuge to collect the luminescent center core - active sensitizing shell product, wash it with ethanol and cyclohexane, and disperse it in cyclohexane to form a core - shell solution.

[0022] (3) Preparation of luminescent center core - active sensitizing shell - inert protective shell

[0023] Add CF3COONa and (CF3COO)3Y with a molar ratio of 1:1 into a three - necked flask, add OA and ODE, heat the mixture to 120 °C under an argon atmosphere and stir to completely dissolve the solid and remove residual water, then cool to room temperature and collect as the NaYF4 inert shell precursor;

[0024] Take the core - shell solution obtained in the above step (2) and add it to a three - necked flask containing OA and ODE, remove cyclohexane in the system at 80 °C; under argon protection, heat the solution to 300 °C, then inject the NaYF4 precursor in portions, with a molar ratio of luminescent center core - active sensitizing shell to precursor of 1:1.4, and react to form the corresponding epitaxial shell;

[0025] Cool the mixture to room temperature, centrifuge to collect the luminescent center core - active sensitizing shell - inert protective shell product, wash it with ethanol and cyclohexane, and disperse it in cyclohexane to form a luminescent center core - active sensitizing shell - inert protective shell up - conversion nanoparticle solution.

[0026] Preferably, the preparation of the temperature - insensitive nanoparticles with a luminescent center core - inert protective shell structure of the present invention includes the following steps:

[0027] (1) Preparation of luminescent center core

[0028] In a three-necked flask, the activator hydrated chloride and hydrated thulium chloride with a molar ratio of 0.995:0.005 are dissolved in oleic acid and 1-octadecene. Under continuous argon protection, oxygen is removed, and the mixture is heated to 150 °C and maintained for at least 30 minutes to obtain a precursor solution.

[0029] After the above solution is cooled to room temperature, a methanol solution containing NaOH and NH4F is added, and then heated to 80 °C to remove methanol in the system; then the temperature is gradually raised to 300 - 320 °C, stirred and maintained for at least 90 minutes to form a NaErF4:Tm luminescent core; the doping concentration of the activator is 99.5 mol%; Tm 3+ The doping concentration is 0.5 mol%.

[0030] After the above solution is cooled to room temperature, it is centrifuged, and ultrasonically washed with ethanol and cyclohexane. Finally, the centrifuged nanoparticles are dispersed in cyclohexane to form a luminescent core solution.

[0031] (2) Preparation of luminescent center core - inert protective shell

[0032] CF3COONa and (CF3COO)3Y with a molar ratio of 1:1 are added to a three-necked flask, and OA and ODE are added. Under an argon atmosphere, the mixture is heated to 120 °C and stirred until all solids are dissolved and residual water is removed. Then it is cooled to room temperature and collected as a NaYF4 inert shell precursor.

[0033] Take the core NaErF4:Tm nanocrystal solution obtained in the above step (1) and add it to a three-necked flask containing OA and ODE. Remove cyclohexane in the system at 80 °C; under argon protection, heat the solution to 300 °C, and then inject the NaYF4 precursor in portions. The molar ratio of the core to the precursor is 1:4, and the reaction forms a corresponding epitaxial shell.

[0034] Cool the mixture to room temperature, centrifuge to collect the luminescent center core - inert protective shell product, wash it with ethanol and cyclohexane, and disperse it in cyclohexane to form a luminescent center core - inert protective shell upconversion nanoparticle solution.

[0035] The depth anti-counterfeiting material based on upconversion luminescence temperature induction described in the present invention is applied to fluorescence anti-counterfeiting, especially for making anti-counterfeiting patterns.

[0036] The temperature-sensitive nanoparticles described in the present invention are coated as a hidden information layer to record hidden information; the temperature-insensitive nanoparticles are used as a protective layer and coated on the upper part of the temperature-sensitive nanoparticle coating; it is completely invisible under natural light, and under near-infrared excitation light, it shows a blurred glare in the temperature range of 100 - 310 K and shows hidden information in the temperature range of 5 - 100 K; when the temperature returns to 100 - 310 K, the hidden information is hidden again.

[0037] The hidden information described above includes digital coding, pattern information, text information or two-dimensional codes.

[0038] The working principle of the present invention:

[0039] Combined Figure 1 as shown;

[0040] The sensitizer Yb of the temperature-sensitive nanoparticles described above 3+ ions have a relatively large absorption cross-section in the infrared region, which can effectively increase the absorption of the doped ions to the excitation light, and then transfer the energy of the external excitation light source to the activator, enhancing the upconversion luminescence efficiency. Yb 3+ absorbs 980 nm near-infrared light ( 2 F 7 / 2 → 2 F 5 / 2 ), and then transfers the obtained energy to Er 3+ ions' 4 I 11 / 2 and 4 F 7 / 2 excited state energy levels, and then through the radiation relaxation process, green upconversion fluorescence (525 nm, 2 H 11 / 2 → 4 I 15 / 2 ; 545 nm, 4 S 3 / 2 → 4 I 15 / 2 ) can be radiated, as well as red upconversion fluorescence (655 nm, 4 F 9 / 2 → 4 I 15 / 2 ). At room temperature, for highly doped nanoparticles, there is cross-relaxation between Er 3+ -Er 3+ ( 4 S 3 / 2 + 4 I 11 / 2 → 4 F 9 / 2 + 4 I 9 / 2 ; 4 S 3 / 2 + 4 I 9 / 2 →2 4 F 9 / 2 ; 4 S 3 / 2 + 4 I 13 / 2 → 4 F 9 / 2 + 4 I 11 / 2The energy quenching caused thereby results in a relatively high red / green (R / G) emission ratio. At low temperatures, lattice vibrations are restricted, cross-relaxation is suppressed, and the green upconversion fluorescence is greatly enhanced compared to red light, causing the red / green emission ratio to decrease and the upconversion luminescence to exhibit a relatively high temperature dependence.

[0041] In addition to a high concentration of activator ions in the luminescence center core of the temperature-insensitive nanoparticles, 0.5% Tm is doped. 3+ ; Due to Er 3+ -Tm 3+ interactions to reconstruct the excited state depopulation process of Er 3+ which is effective at both room temperature and low temperatures. Therefore, the upconversion fluorescence triggered by a low-temperature field is weakened, maintaining a relatively high red / green light emission ratio and a relatively low temperature dependence.

[0042] Both of the above-mentioned nanoparticles are soluble in volatile solvents.

[0043] Advantages of the present invention:

[0044] The deep anti-counterfeiting material based on temperature-induced upconversion luminescence provided by the present invention uses the above-mentioned temperature-sensitive nanoparticles to coat a hidden information layer and temperature-insensitive nanoparticles to coat a covering and protecting layer, and the information pattern is drawn by superimposing the two layers. The pattern made of this anti-counterfeiting material is completely invisible under natural light; at room temperature, it presents a completely blurred glare under near-infrared laser irradiation, and the true information is difficult to distinguish; while under near-infrared laser irradiation in a low-temperature environment, the true information is decoded and presented with relatively high resolution; when the temperature returns to room temperature, the true information is hidden again. The anti-counterfeiting material and method of the present invention have a repeatable and reversible process of "hide - protect - decode - protect - hide", realizing deep anti-counterfeiting protection of important information. Description of the Drawings

[0045] Figure 1 is a diagram of rare earth ion energy levels and their interactions related to the present invention;

[0046] Figure 2 is a TEM diagram of the upconversion nanoparticles obtained in Examples 1 and 2 of the present invention;

[0047] Figure 3 is an X-ray diffraction pattern of the upconversion nanoparticles obtained in Examples 1 and 2 of the present invention;

[0048] Figure 4 is a temperature-related upconversion emission spectrum diagram of the upconversion nanoparticles obtained in Examples 1 and 2 of the present invention under 980 nm excitation;

[0049] Figure 5This is the temperature-dependent red / green emission ratio diagram of the upconversion nanoparticles obtained in Examples 1 and 2 of the present invention under 980 nm excitation;

[0050] Figure 6 This is the application of the double-layer superposition of the upconversion nanoparticles prepared in the present invention in the deep anti-counterfeiting of temperature-induced hiding-protection-decoding-protection-hiding. Detailed implementation manners

[0051] Example 1

[0052] Preparation of temperature-sensitive nanoparticles with a luminescent center core-active sensitizing shell-inert protective shell structure, including the following steps:

[0053] (1) Preparation of the luminescent center core

[0054] Dissolve 1 mmol erbium chloride hexahydrate in 6 ml oleic acid and 15 ml 1-octadecene in a three-necked flask. Under continuous argon protection, deoxygenate for 30 minutes and heat to 150 °C for 30 minutes to obtain a precursor solution;

[0055] After the above solution is cooled to room temperature, add 8 ml of methanol solution containing 0.1 g of NaOH and 0.148 g of NH4F, then heat to 80 °C for 30 minutes to remove methanol in the system; then gradually raise the temperature to 300 - 320 °C, stir and continue for 90 minutes to form a luminescent core;

[0056] After the above solution is cooled to room temperature, centrifuge and wash ultrasonically with ethanol and cyclohexane. Finally, disperse the centrifuged nanoparticles in 8 ml of cyclohexane to form a luminescent core solution.

[0057] (2) Preparation of the luminescent center core-active sensitizing shell

[0058] Add 1 mmol of CF3COONa and 1 mmol of (CF3COO)3Yb to a three-necked flask, and add 5 ml of OA and 5 ml of ODE. Under an argon atmosphere, heat the mixture to 120 °C and stir for 30 min to dissolve the solids and remove the residual water. Then cool to room temperature and collect as the NaYbF4 active shell precursor;

[0059] Take 1 ml of the core solution obtained in the above step (1) and add it to a three-necked flask containing 5 ml of OA and 5 ml of ODE. Maintain at 80 °C for 30 minutes to remove cyclohexane in the system; under argon protection, heat the solution to 300 °C, and then inject 0.9 mmol of the NaYbF4 precursor in portions, with each reaction time being 15 min, to form the corresponding epitaxial shell;

[0060] Cool the mixture to room temperature, centrifuge to collect the luminescent center core - active sensitizing shell product, wash it with ethanol and cyclohexane, and disperse it in 4 ml of cyclohexane to form a core - shell solution.

[0061] (3) Preparation of luminescent center core - active sensitizing shell - inert protective shell

[0062] Add 1 mmol of CF3COONa and 1 mmol of (CF3COO)3Y to a three - necked flask, add 5 ml of OA and 5 ml of ODE, heat the mixture to 120 °C under an argon atmosphere and stir for 30 min to dissolve the solid and remove the residual water, then cool to room temperature and collect it as the NaYF4 inert shell precursor;

[0063] Take 4 ml of the core - shell solution obtained in the above step (2) and add it to a three - necked flask containing 5 ml of OA and 5 ml of ODE, maintain at 80 °C for 30 minutes to remove cyclohexane from the system; under argon protection, heat the solution to 300 °C, then inject 0.8 mmol of NaYF4 precursor in portions, with each reaction time being 15 min, to form the corresponding epitaxial shell;

[0064] Cool the mixture to room temperature, centrifuge to collect the luminescent center core - active sensitizing shell - inert protective shell product, wash it with ethanol and cyclohexane, and disperse it in 8 ml of cyclohexane to form a luminescent center core - active sensitizing shell - inert protective shell solution.

[0065] Figure 2 (a) Transmission electron micrograph of the core - shell - shell up - conversion nanoparticles prepared in Example 1 of the present invention, with an average particle size of 42.56 nm.

[0066] Figure 3 (a) X - ray diffraction pattern of the core - shell - shell up - conversion nanoparticles prepared in Example 1 of the present invention, and the corresponding crystal phase is a pure hexagonal phase.

[0067] Figure 4 (a) Temperature - dependent up - conversion emission spectrum of the core - shell - shell up - conversion nanoparticles prepared in Example 1 of the present invention under 980 nm laser irradiation. When the temperature gradually decreases from 300 K to 40 K, the total emission intensity gradually increases, and it is enhanced by about 10 times at 40 K compared with room temperature.

[0068] Figure 5 (a) Temperature - dependent red / green emission intensity ratio of the core - shell - shell up - conversion nanoparticles prepared in Example 1 of the present invention under 980 nm laser irradiation. As the temperature gradually decreases, its red / green light ratio decreases from 10 to 1.3.

[0069] Example 2

[0070] Preparation of temperature-insensitive nanoparticles with a luminescent core-inert protective shell structure, comprising the following steps:

[0071] (1) Preparation of the luminescent core

[0072] Dissolve 0.995 mmol of erbium chloride hydrate and 0.005 mmol of thulium chloride hydrate in 6 ml of oleic acid and 15 ml of 1-octadecene in a three-necked flask. Under continuous argon protection, deoxygenate for 30 minutes and heat to 150 °C for 30 minutes to obtain a precursor solution;

[0073] After the above solution is cooled to room temperature, add 8 ml of a methanol solution containing 0.1 g of NaOH and 0.148 g of NH4F. Then heat to 80 °C for 30 minutes to remove methanol from the system; gradually raise the temperature to 300 - 320 °C, stir and continue for 90 minutes to form a NaErF4:Tm luminescent core;

[0074] After the above solution is cooled to room temperature, centrifuge and wash ultrasonically with ethanol and cyclohexane. Finally, disperse the centrifuged nanoparticles in 8 ml of cyclohexane to form a luminescent core solution.

[0075] (2) Preparation of the luminescent core-inert protective shell

[0076] Add 1 mmol of CF3COONa and 1 mmol of (CF3COO)3Y to a three-necked flask, add 5 ml of OA and 5 ml of ODE, heat the mixture to 120 °C under an argon atmosphere and stir for 30 min to dissolve the solid and remove residual water. Then cool to room temperature and collect as a NaYF4 inert shell precursor;

[0077] Take 2 ml of the core NaErF4:Tm nanocrystal solution obtained in the above step (1) and add it to a three-necked flask containing 5 ml of OA and 5 ml of ODE. Maintain at 80 °C for 30 minutes to remove cyclohexane from the system; under argon protection, heat the solution to 300 °C, then inject 0.8 mmol of the NaYF4 precursor in portions, with each reaction time being 15 min, to form the corresponding epitaxial shell;

[0078] Cool the mixture to room temperature, centrifuge to collect the luminescent core-inert protective shell product, wash with ethanol and cyclohexane, and disperse in 8 ml of cyclohexane to form a luminescent core-inert protective shell solution.

[0079] Figure 2 (b) is the transmission electron microscope image of the core-shell upconversion nanoparticles prepared in Example 2 of the present invention, with an average particle size of 31.60 nanometers.

[0080] Figure 3(b) is the X-ray diffraction pattern of the core-shell upconversion nanoparticles prepared in Example 2 of the present invention, and the corresponding crystal phase is a pure hexagonal phase.

[0081] Figure 4 (b) is the temperature-dependent upconversion emission spectrum of the core-shell upconversion nanoparticles prepared in Example 2 of the present invention under 980 nm laser irradiation. When the temperature gradually decreases, the total emission intensity slightly increases, and the maximum enhancement is about 3 times.

[0082] Figure 5 (b) is the ratio of the red / green emission intensities of the core-shell upconversion nanoparticles prepared in Example 2 of the present invention under 980 nm laser irradiation as a function of temperature. In the range of 40 - 300 K, the red / green ratio always remains large (12 - 23).

[0083] Example 3

[0084] Application of a depth anti-counterfeiting material based on upconversion luminescence temperature induction:

[0085] As Figure 6 shown, the present invention provides an application method of a depth anti-counterfeiting material based on upconversion luminescence temperature induction, and the information to be encrypted and protected is a two-dimensional code; the temperature-sensitive nanoparticles prepared in Example 1 are coated as the bottom hidden information layer, and a volatile solution containing upconversion luminescent nanoparticles is coated on the surface of the three-dimensional model of the two-dimensional code and printed on the paper surface; the temperature-insensitive nanoparticles prepared in Example 2 are coated as the upper covering protection layer, and the two layers are stacked to form an anti-counterfeiting information pattern.

[0086] This pattern is invisible under natural light and completely invisible;

[0087] At room temperature, under near-infrared laser irradiation, a completely blurred red glare is presented, and the real information is difficult to distinguish, forming a protection layer;

[0088] Under near-infrared laser irradiation in a low-temperature environment of 5 - 100 K, the bottom upconversion nanoparticles exhibit strong green luminescence, the bottom pattern appears, and the real information is decoded with high resolution;

[0089] When restored to room temperature, the luminescence intensity of the bottom layer particles decreases, is covered by the red luminescence, and the real information is re-protected.

[0090] Invisible under natural light and re-invisible.

[0091] The anti-counterfeiting method of the present invention has a repeatable and reversible hiding - protection - decoding - protection - hiding process, realizing deep anti-counterfeiting encryption of important information. This anti-counterfeiting technology can be applied to the anti-counterfeiting protection of digital codes, pattern information, and two-dimensional codes.

Claims

1. A depth anti-counterfeiting material based on upconversion luminescence temperature induction, characterized in that: It includes two kinds of core-shell structured nano-ions with highly doped upconversion luminescence of lanthanide rare-earth ions with different temperature dependences. One is a temperature-sensitive nanoparticle with a structure of a luminescent center core - an active sensitizing shell - an inert protective shell, and the other is a temperature-insensitive nanoparticle with a structure of a luminescent center core - an inert protective shell; The luminescent center core is a host matrix doped with an activator, and the activator is Ho 3+ or Er 3+ ; The active sensitizing shell is a host matrix doped with a sensitizer, and the sensitizer is Yb 3+ ; The host matrix is NaYF4, NaLuF4 or NaGdF4; The inert protective shell is NaYF4, NaLuF4 or NaGdF4; In the temperature-insensitive nanoparticles, the luminescent center core is further doped with energy trapping center ions, and the energy trapping center ions are Tm 3+ .

2. The depth anti-counterfeiting material based on upconversion luminescence temperature induction according to claim 1, wherein: The doping concentration of the activator is 20% - 100% in mole percentage; the doping concentration of the sensitizer is 0% - 100% in mole percentage.

3. The depth anti-counterfeiting material based on upconversion luminescence temperature induction according to claim 1, characterized in that: In the temperature-insensitive nanoparticles described above, the molar percentage of Tm 3+ doping concentration is 0.5%.

4. The depth anti-counterfeiting material based on upconversion luminescence temperature induction according to claim 1, wherein: The preparation of the temperature-sensitive nanoparticle with a structure of a luminescent center core - an active sensitizing shell - an inert protective shell includes the following steps: (1)Preparation of the luminescent center core Dissolve the activator hydrated chloride in oleic acid and 1-octadecene in a three-necked flask; deoxygenate under continuous argon protection and heat to 150 °C for at least 30 minutes to obtain a precursor solution; Wait for the above solution to cool to room temperature, add a methanol solution containing NaOH and NH4F, then heat to 80 °C to remove methanol in the system; then gradually raise the temperature to 300 - 320 °C, stir and continue for at least 90 minutes to form a luminescent core; the doping concentration of the activator is 100% in mole percentage; Wait for the above solution to cool to room temperature, centrifuge and wash ultrasonically with ethanol and cyclohexane, and finally disperse the centrifuged nanoparticles in cyclohexane to form a luminescent core solution; (2)Preparation of the luminescent center core - active sensitizing shell Add CF3COONa and (CF3COO)3Yb with a molar ratio of 1:1 to a three-necked flask; add OA and ODE, heat the mixture to 120 °C and stir under an argon atmosphere to dissolve the solid and remove the residual water, then cool to room temperature and collect as a NaYbF4 active shell precursor; Take the core solution obtained in the above step (1) and add it to a three-necked flask containing OA and ODE, remove cyclohexane in the system at 80 °C; under argon protection, heat the solution to 300 °C, then inject the NaYbF4 precursor in portions, with a molar ratio of core to precursor of 1:3.6, and react to form the corresponding epitaxial shell; the doping concentration of the sensitizer is 100% in mole percentage; Cool the mixture to room temperature, centrifuge to collect the luminescent center core - active sensitizing shell product, wash with ethanol and cyclohexane, and disperse in cyclohexane to form a core - shell solution; (3)Preparation of the luminescent center core - active sensitizing shell - inert protective shell Add CF3COONa and (CF3COO)3Y with a molar ratio of 1:1 to a three-necked flask, and add OA and ODE. Heat the mixture to 120 °C and stir under an argon atmosphere to dissolve all the solids and remove the residual water, then cool to room temperature and collect as a NaYF4 inert shell precursor; Add the core-shell solution obtained in the above step (2) into a three-necked flask containing OA and ODE, and remove cyclohexane in the system at 80 °C; under argon protection, heat the solution to 300 °C, and then inject the NaYF4 precursor in portions. The molar ratio of the luminescent center core-active sensitizing shell to the precursor is 1:1.4, and the corresponding epitaxial shell is formed by reaction. Cool the mixture to room temperature, centrifuge to collect the luminescent center core-active sensitizing shell-inert protective shell product, wash it with ethanol and cyclohexane, and disperse it in cyclohexane to form a luminescent center core-active sensitizing shell-inert protective shell upconversion nanoparticle solution.

5. The depth anti-counterfeiting material based on upconversion luminescence temperature induction according to claim 1, characterized in that: The preparation of the temperature-insensitive nanoparticles with a luminescent center core-inert protective shell structure includes the following steps: (1) Preparation of the luminescent center core Dissolve the activator hydrated chloride and hydrated thulium chloride with a molar ratio of 0.995:0.005 in oleic acid and 1-octadecene in a three-necked flask, remove oxygen under continuous argon protection, and heat to 150 °C for at least 30 minutes to obtain a precursor solution. After the above solution is cooled to room temperature, a methanol solution containing NaOH and NH4F is added, and then heated to 80 °C to remove methanol in the system; then gradually heated to 300 - 320 °C, stirred and continued for at least 90 minutes to form a NaErF4:Tm luminescent core; the doping concentration of the activator is 99.5 mmol% in molar percentage; Tm 3+ The doping concentration is 0.5% in molar percentage; Wait for the above solution to cool to room temperature, centrifuge and separate, wash it ultrasonically with ethanol and cyclohexane, and finally disperse the centrifuged nanoparticles in cyclohexane to form a luminescent core solution. (2) Preparation of the luminescent center core-inert protective shell Add CF3COONa and (CF3COO)3Y with a molar ratio of 1:1 to a three-necked flask, add OA and ODE, heat the mixture to 120 °C and stir under an argon atmosphere to dissolve all the solids and remove the residual water, then cool to room temperature and collect it as the NaYF4 inert shell precursor. Take the core NaErF4:Tm nanocrystal solution obtained in the above step (1) and add it to a three-necked flask containing OA and ODE, remove cyclohexane in the system at 80 °C; under argon protection, heat the solution to 300 °C, and then inject the NaYF4 precursor in portions. The molar ratio of the core to the precursor is 1:4, and the corresponding epitaxial shell is formed by reaction. Cool the mixture to room temperature, centrifuge to collect the luminescent center core-inert protective shell product, wash it with ethanol and cyclohexane, and disperse it in cyclohexane to form a luminescent center core-inert protective shell upconversion nanoparticle solution.

6. The application of the depth anti-counterfeiting material based on upconversion luminescence temperature induction according to claim 1, characterized in that: The temperature-sensitive nanoparticles are coated as a hidden information layer to record the hidden information; the temperature-insensitive nanoparticles are used as a protective layer and coated on the upper part of the temperature-sensitive nanoparticle coating.

7. The application of the depth anti-counterfeiting material based on upconversion luminescence temperature induction according to claim 6, characterized in that: It is completely invisible under natural light, shows a blurred glare in the temperature range of 100 - 310 K under near-infrared excitation light, and shows the hidden information in the temperature range of 5 - 100 K; when the temperature returns to 100 - 310 K, the hidden information is re-hidden.

8. The application of the depth anti-counterfeiting material based on upconversion luminescence temperature induction according to claim 6, characterized in that: The hidden information includes digital coding, pattern information, text information or two-dimensional codes.

9. Use of the depth anti-counterfeiting material based on upconversion luminescence temperature induction according to any one of claims 6-8, characterized in that: The depth anti-counterfeiting material based on upconversion luminescence temperature induction is applied to fluorescence anti-counterfeiting, including making anti-counterfeiting patterns.

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