Single-mode excitation color-tunable luminescent upconversion material, and preparation method therefor and use thereof in security Anti-counterfeiting

Abstract

The present invention relates to the technical field of optical anti-counterfeiting. Disclosed are a single-mode excitation color-tunable luminescent upconversion material, and a preparation method therefor and a use thereof in security anti-counterfeiting. The single-mode excitation color-tunable luminescent upconversion material has a molecular formula of AxMOCly-1:Yb / Ln, wherein A is at least one of Li+, Na+, K+, and Cs+, M is at least one of La3+, Y3+, Gd3+, and Lu3+, and Ln is at least one of Er3+, Ho3+, and Tm3+, with 1≤x≤4 and 4≤y≤7. The single-mode excitation color-tunable luminescent upconversion material has an excitation wavelength range of 950 nm to 11000 nm and an emission wavelength range of 400 nm to 800 nm. Under excitation by single-mode near-infrared light, the material exhibits color-tunable upconversion luminescence. The upconversion material has a fast-responsive color-tunable luminescence function, can be used as a high-level security anti-counterfeiting strategy, and is easy and convenient to identify.

Description

Single-mode excitation color-changing luminescence upconversion material, preparation method thereof and application thereof in security anti-counterfeiting TECHNICAL FIELD

[0001] The present application relates to the field of optical anti-counterfeiting technology, in particular to a single-mode excitation color-changing luminescence upconversion material, a preparation method thereof and an application thereof in security anti-counterfeiting. BACKGROUND

[0002] Globally, the counterfeit and substandard goods business causes more than 1.7 trillion US dollars in economic losses each year. Counterfeiting in the fields of pharmaceuticals, high-value goods and currency seriously threatens the health of consumers, the interests of enterprises and the security of the social economy. Anti-counterfeiting strategies can make it difficult for genuine goods to be replicated and effectively prevent counterfeit goods from circulating in the market. Rare earth-doped upconversion crystal materials, as one of the anti-counterfeiting strategies, have the advantages of low background fluorescence and strong anti-photobleaching ability. At present, upconversion materials applied to currency and high-value goods have single green light emission. The color of the emitted light of these anti-counterfeiting materials is almost unchanged under near-infrared light excitation. The anti-counterfeiting patterns constructed with such materials can still be imitated by counterfeiters using other materials with similar luminescence.

[0003] The security level of upconversion anti-counterfeiting materials can be improved by regulating the luminescence color. In recent years, a large number of studies have been conducted on multicolor fluorescent materials. For example, multicolor fluorescence is generated by multimode fluorescence, adjusting laser power or using pulsed laser. These strategies greatly improve the security level of anti-counterfeiting technology, but relatively complex identification equipment is required to trigger the multicolor luminescence of these new upconversion materials. First, upconversion and downconversion cooperative luminescence requires multiple excitation sources; second, power-dependent multicolor luminescence requires adjustable ultrahigh power laser; and finally, time-gated multiplexing requires a time-gated decoding device. The complexity of the material structure and the special identification method limit the commercial application of these anti-counterfeiting materials. Therefore, it is necessary to develop an anti-counterfeiting material with a convenient identification method and a high security level.

[0004] Therefore, based on the above technical problems, it is necessary to provide an anti-counterfeiting material with a convenient identification method and a high security level. SUMMARY

[0005] To solve the above technical problems, the present application provides a single-mode excitation color-changing luminescence upconversion material, a preparation method thereof and an application thereof in security anti-counterfeiting. The present application uses an anion doping strategy to prepare A x MOCl y-1 :Yb / Ln upconversion material by a solid-phase reaction method. Under the excitation of a single near-infrared light, various different paths of color-changing upconversion luminescence are realized. This color-changing luminescence upconversion material not only has a simple and convenient identification method, but also has a high security anti-counterfeiting level, and has potential applications in the field of anti-counterfeiting.

[0006] A first object of the present application is to provide a single-mode excitation color-changing luminescent upconversion material, the molecular formula of the single-mode excitation color-changing luminescent upconversion material being A x MOCl y-1 :Yb / Ln,

[0007] wherein A is at least one of Li + , Na + , K + , Cs + ;

[0008] M is at least one of La 3+ , Y 3+ , Gd 3+ , Lu 3+ ;

[0009] Ln is at least one of Er 3+ , Ho 3+ , Tm 3+ ;

[0010] 1≤x≤4, 4≤y≤7.

[0011] In some embodiments of the present application, the A x MOCl y-1 :Yb / Ln Yb 3+ is a sensitizing agent, occupying the M site, and the doping amount of Yb 3+ is 1%-30%.

[0012] In some embodiments of the present application, the A x MOCl y-1 :Yb / Ln Ln 3+ is an activating agent, occupying the M site, and the doping amount of Ln 3+ is 0.1%-5%.

[0013] In some embodiments of the present application, the A x MOCl y-1 :Yb / Ln O 2- is a doped anion, occupying the Cl site.

[0014] In some embodiments of the present application, the excitation wavelength of the single-mode excitation color-changing luminescent upconversion material is 950nm-1100nm.

[0015] In some embodiments of the present application, the emission wavelength of the single-mode excitation color-changing luminescent upconversion material is 400nm-800nm.

[0016] The color change of the single-mode excitation color-changing luminescent upconversion material includes, but is not limited to, red to green, green to cyan, and green to blue.

[0017] A second object of the present application is to provide a preparation method of the single-mode excitation color-changing luminescent upconversion material, comprising the following steps: using a solid phase reaction method to prepare the single-mode excitation color-changing luminescent upconversion material from a chloride of A, a chloride of M, a sensitizer, and an activator.

[0018] In some embodiments of the present application, the chloride of A is selected from one or more of LiCl, NaCl, KCl, and CsCl;

[0019] The chloride of M is selected from one or more of LaCl3, YCl3, GdCl3, and LuCl3;

[0020] The sensitizer is selected from YbCl3;

[0021] The activator is selected from one or more of ErCl3, HoCl3, and TmCl3.

[0022] In some embodiments of the present application, the heat treatment temperature in the solid phase reaction method is 100-500°C, and the heat treatment time is 2-48h.

[0023] In some embodiments of the present application, the specific preparation method is as follows:

[0024] The chloride of A, the chloride of M, the sensitizer, and the activator are mixed according to the formula A x MOCl y-1 :Yb / Ln ratio, then ground uniformly, and then heated using a muffle furnace, a tube furnace, or an oven for solid phase reaction to obtain the single-mode excitation color-changing luminescent upconversion material.

[0025] A third object of the present application is to provide an application of the single-mode excitation color-changing luminescent upconversion material in security and anti-counterfeiting.

[0026] The above technical solution of the present application has the following advantages compared with the prior art:

[0027] (1) Anion O 2- Doping, O occupies the Cl site, and the symmetry of the crystal field is reduced; the low-symmetry crystal field is conducive to the Stark splitting of the 4f energy level of the small-radius rare earth ion under the action of laser heat effect, changes the upconversion luminescence dynamics, and changes the upconversion luminescence mechanism from energy transfer upconversion to excited state absorption, thereby realizing the thermally responsive color-changing upconversion luminescence.

[0028] (2) The solid phase reaction method is used in the preparation process, and the optical performance is stable;

[0029] (3) Single-mode excitation triggers color change luminescence, and the identification method is simple and convenient;

[0030] (4) The color change luminescence path is diversified, and the anti-counterfeiting technology level is high. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to make the content of the application more easily and clearly understood, the application will be further described in detail below according to specific embodiments of the application and in conjunction with the drawings, in which,

[0032] Fig. 1 is an XRD pattern of Cs2GdOCl4:Yb / Er of embodiment 1 of the application;

[0033] Fig. 2 is an upconversion emission spectrum of the color change luminescence upconversion material Cs2GdOCl4:Yb / Er of embodiment 1 of the application under excitation at 975 nm at different times;

[0034] Fig. 3 is an emission spectrum of the color change luminescence upconversion material Cs2GdOCl4:Yb / Er of embodiment 1 of the application, in which the integral intensity of the emission bands at 525 nm (Green) and 660 nm (Red) is shown;

[0035] Fig. 4 is a photo of the color change of the luminescence of the color change luminescence upconversion material Cs2GdOCl4:Yb / Er solid powder of embodiment 1 of the application within 4 s;

[0036] Fig. 5 is an XRD pattern of CsGdOCl3:Yb / Ho of embodiment 2 of the application;

[0037] Fig. 6 is an upconversion emission spectrum of the color change luminescence upconversion material CsGdOCl3:Yb / Ho of embodiment 2 of the application under excitation at 975 nm at different times;

[0038] Fig. 7 is an emission spectrum of the color change luminescence upconversion material CsGdOCl3:Yb / Ho of embodiment 2 of the application, in which the integral intensity of the emission bands at 475 nm (Blue), 530 nm (Green), 590 nm (Orange) and 650 nm (Red) is shown;

[0039] Fig. 8 is a photo of the color change of the luminescence of the color change luminescence upconversion material CsGdOCl3:Yb / Ho solid powder of embodiment 2 of the application within 4 s;

[0040] Fig. 9 is an XRD pattern of K3YOCl5:Yb / Tm of embodiment 3 of the application;

[0041] Fig. 10 is an upconversion emission spectrum of the color change luminescence upconversion material K3YOCl5:Yb / Tm of embodiment 3 of the application under excitation at 975 nm at different times;

[0042] Figure 11 is a photo of the color change of the color-change luminescent up-conversion material K3YOC15:Yb / Tm solid powder under excitation at 6s. DETAILED DESCRIPTION

[0043] The application will be further described below in conjunction with the drawings and specific examples so that those skilled in the art can better understand the application and implement it.

[0044] Example 1 (Cs2GdOCl4:Yb / Er)

[0045] This example provides a method for preparing a single-mode excitation color-change luminescent up-conversion material (Cs2GdOCl4:Yb / Er), which is as follows:

[0046] 2mmol of CsCl, 0.78mmol of GdCl3, 0.2mmol of YbCl3, and 0.02mmol of ErCl3 were weighed and mixed uniformly in a mortar. The mixture was placed in a tube furnace for calcination. The calcination temperature was 450°C, and the time was 24 hours. The obtained Cs2GdOCl4:Yb / Er had an XRD pattern as shown in Figure 1.

[0047] The obtained Cs2GdOCl4:Yb / Er was continuously captured under excitation at 975nm. The emission spectra at different times and the integrated intensities of the emission bands showed that the initial red emission band (~660nm) was stronger than the green emission band (~525nm), and the sample emitted red light. With the extension of the excitation time, the red emission band gradually weakened, while the green emission gradually strengthened, and the sample emitted green light in the later stage. As shown in Figure 4, the Cs2GdOCl4:Yb / Er under excitation at 975nm changed from red to green in a short time (4s).

[0048] Example 2 (CsGdOCl3:Yb / Ho)

[0049] This example provides a method for preparing a single-mode excitation color-change luminescent up-conversion material (CsGdOCl3:Yb / Ho), which is as follows:

[0050] 1mmol of CsCl, 0.78mmol of GdCl3, 0.2mmol of YbCl3, and 0.02mmol of HoCl3 were weighed and mixed uniformly in a mortar. The mixture was placed in a muffle furnace for calcination. The calcination temperature was 300°C, and the time was 2 hours. The obtained CsGdOCl3:Yb / Ho had an XRD pattern as shown in Figure 5.

[0051] The obtained CsGdOCl3:Yb / Ho was excited at 975 nm, and the emission spectra at different excitation times were measured, and the emission bands of the emission spectra were integrated, and the results are shown in Figures 6 and 7. As shown in Figure 6, at the initial stage of 975 nm excitation, the green emission intensity (~540 nm) of the sample is dominant, and the red emission intensity (~660 nm) is relatively weak, so the sample initially emits green light; with the extension of the excitation time, the blue emission intensity (~475 nm) of the sample gradually increases, and its intensity exceeds the green and red emission intensities in the later stage (Figure 7). As shown in Figure 8, the CsGdOCl3:Yb / Ho emits green-to-cyan color-changing light within 4 s under 975 nm excitation.

[0052] Example 3 (K3YOCl5:Yb / Tm)

[0053] The present example provides a preparation method of a single-mode excitation color-changing upconversion luminescent material (K3YOCl5:Yb / Tm), which is specifically as follows:

[0054] 3 mmol of KCl, 0.79 mmol of YCl3, 0.2 mmol of YbCl3, and 0.01 mmol of TmCl3 were weighed and uniformly mixed in a mortar, and the mixture was placed in an oven for heat treatment, with a treatment temperature of 120°C and a treatment time of 48 hours, to obtain K3YOCl5:Yb / Tm, and the XRD pattern thereof is shown in Figure 9.

[0055] The obtained K3YOCl5:Yb / Tm sample was continuously excited at 975 nm, and the emission spectra at different times were obtained (Figure 10). At the initial stage of the emission spectra, there is a relatively strong green emission peak at ~525 nm, and the blue emission peak at ~475 nm is weak, so the sample emits green light at the initial stage of excitation; with the extension of the excitation time, although the green emission band is enhanced, the blue emission band is enhanced more significantly, so the sample emits blue light in the later stage of excitation. The color-changing luminescence photograph of the solid powder within a short time confirms this single-mode excitation color-changing (green-to-blue) upconversion luminescence phenomenon (Figure 11).

[0056] Obviously, the above examples are merely examples for clarity, and are not limiting to the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A single mode excitation color changing luminescent upconversion material, characterized in that, The molecular formula A of the single-mode excitation color-changing luminescence up-conversion material x M0CI y-1 :Yb / Ln; wherein A is at least one of Li + , Na + , K + , Cs + . M is at least one of Y 3+ , Gd 3+ , Lu 3+ , and 3+ ​ Ln is at least one of Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu 3+ 3+ 3+ at least one of Y, Gd, Tb, Dy, Ho, Er, Tm​​ 1≤x≤4, 4≤y≤7.

2. The single-mode excitation color-changing luminescence upconversion material of claim 1, wherein, The A x MOC1 y-1 Yb in Yb / Ln 3+ is a sensitizer, occupies M site, Yb 3+ Doping amount of Yb is 1%-30%.

3. The single-mode excitation color-changing luminescence upconversion material of claim 1, wherein, The A x MOC1 y-1 : Yb / Ln 3+ is an activator, occupies M sites, Ln 3+ is doped in an amount of 0.1% - 5%.

4. The single-mode excitation metameric luminescent upconversion material of claim 1, wherein, The A x MOC1 y-1 O in :Yb / Ln 2- is a doped anion occupying the Cl site.

5. The single-mode excitation metameric luminescent upconversion material of claim 1, wherein, The excitation wavelength of the single-mode excitation color-changing luminescent upconversion material is 950 nm-1100 nm; The emission wavelength of the single-mode excitation color-changing luminescent upconversion material is 400 nm-800 nm.

6. The single-mode excitation metameric luminescent upconversion material of claim 1, wherein, The color change of the single-mode excitation color-changing luminescent upconversion material includes but is not limited to red to green, green to cyan, and green to blue.

7. A method of producing a single-mode excitation color-changing luminescent upconversion material according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: The chloride of A, the chloride of M, the sensitizer, and the activator are used to prepare the single-mode excitation color-changing luminescent upconversion material by a solid phase reaction method.

8. The preparation method according to claim 7, characterized in that, The chloride of A is selected from one or more of LiCl, NaCl, KCl, and CsCl; The chloride of M is selected from one or more of LaCl3, YCl3, GdCl3, and LuCl3; The sensitizer is selected from YbCl3; The activator is selected from one or more of ErCl3, HoCl3, and TmCl3.

9. The preparation method according to claim 7, characterized in that, The heat treatment temperature in the solid phase reaction method is 100°C-500°C, and the heat treatment time is 2-48 h.

10. Application of the single-mode excitation color-changing luminescent upconversion material in security and anti-counterfeiting according to any one of claims 1-6.

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