A Class of All-Spectrum Multicolor Long Afterglow Fluorescent Materials at 77K and Their Preparation Methods

Abstract

The present invention discloses a class of full-spectrum multicolor long afterglow fluorescent materials at 77K and a preparation method thereof, belonging to the technical field of rare earth luminescent materials. The multicolor low-temperature long afterglow material of the present invention uses a double perovskite material doped with rare earth ions as a fluorescence emitter, and its chemical formula is Cs2NaLuCl6:5%Ln 3+ , where Ln is one or a combination of more of Er, Tm, Tb, Dy, Sm, Pr, Nd. The phosphor of the present invention has good chemical stability and excellent luminescence performance, and has a persistent luminescence lasting up to 2 hours at the liquid nitrogen temperature of 77 K. By simply changing the luminescence center, long afterglow luminescence of various colors such as red, green, and blue can be achieved at 77 K.

Description

Technical Field

[0001] The present invention belongs to the technical field of rare earth luminescent materials, and particularly relates to a class of full-spectrum multicolor long afterglow fluorescent materials at 77 K low temperature and a preparation method thereof. Background Art

[0002] Persistent luminescence, also known as long afterglow, is a fascinating optical phenomenon in which materials continue to emit light for seconds to hours after the excitation source is turned off. Phosphors showing persistent luminescence have received great attention and are widely used in safety displays, decoration, and emergency lighting. So far, the commercialized long afterglow luminescent materials include blue long afterglow luminescent material CaAl2O4:Eu 2+ , Nd 3+ , green long afterglow luminescent material SrAl2O4:Eu 2+ , Dy 3+ , red long afterglow luminescent material Y2O2S:Eu 3+ , Mg 2+ , Ti 4+ etc. These long afterglow materials will lose their long afterglow luminescence characteristics at extremely low temperatures of 77 K because the trap depth of these materials is relatively large, and the energy in the traps cannot be transferred to the luminescence centers through the thermal detrapping process, thus losing the long afterglow performance. Therefore, a shallow trap depth is a prerequisite for achieving low-temperature long afterglow. Currently, only a few examples of luminescent materials with low-temperature long afterglow material characteristics have been reported. For example, Dirk Poelman et al. found that Mg 1+x Ga 2−2x Ge x O4:Cr 3+ has near-infrared long afterglow luminescence characteristics near 709 nm at -77 °C. Zhang Yuhai et al. found that Cs2AgInCl6:Mn 2+ has red long afterglow luminescence characteristics at low temperatures. Zhang Jiahua et al. recently reported a green oxynitride phosphor BaSi2O2N2:Eu 2+ with long afterglow characteristics at liquid nitrogen temperature. Yu Xue et al. found that NaNbO3:Pr 3+ has very long red long afterglow luminescence characteristics at low temperatures. However, the currently reported low-temperature long afterglow materials have a single luminescence color. Therefore, it is crucial to explore a class of multicolor low-temperature full-spectrum long afterglow fluorescent materials. Summary of the Invention

[0003] In order to improve the current situation of the single afterglow luminescence color of existing materials at low temperatures, the present invention provides a class of multicolor low-temperature full-spectrum long afterglow fluorescent materials, which use rare-earth double perovskite materials as the matrix and realize multicolor phosphors by doping different rare-earth ions. Its synthesis method is simple and has high chemical stability. It not only has long afterglow at room temperature, but also has long afterglow luminescence performance at 77 K, and the continuous luminescence time is as long as 2 hours.

[0004] Based on the above purposes, the present invention adopts the following technical solutions:

[0005] A class of full-spectrum multicolor long afterglow fluorescent materials at 77 K low temperature, with double perovskite materials doped with rare-earth ions as the fluorescence emitters, and its chemical formula is Cs2NaLuCl6:5%Ln 3+ , where Ln is one or a combination of more of Er, Tm, Tb, Dy, Sm, Pr, Nd. By simply changing the luminescence center, long afterglow luminescence of various colors such as red, green, and blue can be achieved at 77 K.

[0006] The thermoluminescence curve of this material ranges from 77 K to 300 K after the sample is excited by X-ray at a temperature of 77 K, and it has low-temperature traps.

[0007] After the excitation light source is removed at 77 K, this material has the characteristic of long afterglow luminescence, and the continuous luminescence time is as long as 2 hours.

[0008] The preparation method of the above-mentioned full-spectrum multicolor long afterglow fluorescent materials at 77 K low temperature is as follows: Using NaCl, CsCl, LuCl3·6H2O, and LnCl3 as raw materials, weigh the raw materials according to the stoichiometric molar ratio in the target product, transfer each raw material to the inner lining of the reaction kettle and mix evenly, add concentrated hydrochloric acid to the inner lining of the reaction kettle, and stir magnetically for 0.5 - 2 hours; then, heat the autoclave to 180 - 200 °C, keep it for 10 - 15 hours, cool it naturally to room temperature, wash it with isopropyl alcohol, and dry it to obtain the product.

[0009] Furthermore, the molar ratio of NaCl, CsCl, LuCl3, and LnCl3 is 1:2:0.95:0.05, and 4 - 6 mL of concentrated hydrochloric acid needs to be added for every 1 mol of Cs2NaLuCl6:5%Ln 3+ needs to be added.

[0010] Furthermore, the LnCl3 is specifically one or a combination of more of ErCl3·6H2O, TmCl3·6H2O, TbCl3·6H2O, DyCl3·6H2O, SmCl3·6H2O, PrCl3, and NdCl3·6H2O.

[0011] The beneficial effects of the present invention:

[0012] For general long - persistent materials, their long - persistent properties will be lost at low temperatures and the luminescent color is single. The present invention provides a class of multicolor low - temperature full - spectrum long - persistent fluorescent materials with the chemical formula Cs2NaLuCl6:5%Ln 3+ , where Ln is one of Er, Tm, Tb, Dy, Sm, Pr, Nd. Multicolor luminescence is achieved by doping different rare - earth ions into the double - perovskite matrix material. Moreover, for this class of long - persistent materials obtained by doping, the thermoluminescence peaks measured after X - ray excitation at a temperature of 77 K are concentrated in the 77 - 300 K region, with a relatively shallow trap depth, which provides an explanation for the persistent luminescence characteristics of this class of long - persistent materials at low temperatures. This class of multicolor low - temperature full - spectrum long - persistent fluorescent materials has broad application prospects in many fields such as biomedical preservation and vaccine freezing. Description of the Drawings

[0013] Figure 1 XRD pattern of the long - persistent fluorescent material Cs2NaLuCl6:5%Ln 3+ , (Ln = Er, Tm, Tb, Dy, Sm, Pr, Nd) in Example 1;

[0014] Figure 2 Emission spectra of the long - persistent fluorescent material Cs2NaLuCl6:5%Ln 3+ , (Ln = Er, Tm, Tb, Dy, Sm, Pr, Nd) in Example 1 under X - ray excitation at temperatures of 77 K and 300 K;

[0015] Figure 3 Thermoluminescence curve of the long - persistent fluorescent material Cs2NaLuCl6:5%Ln 3+ , (Ln = Er, Tm, Tb, Dy, Sm, Pr, Nd) in Example 1 written at a temperature of 77 K;

[0016] Figure 4 Display diagram of the photoluminescence colors of the long - persistent fluorescent material Cs2NaLuCl6:5%Ln 3+ , (Ln = Er, Tm, Tb, Dy, Sm, Pr, Nd) in Example 1 at temperatures of 77 K and 300 K on the CIE coordinate diagram;

[0017] Figure 5 For the long - persistent fluorescent material Cs2NaLuCl6:5%Ln 3+, Afterglow luminescence photographs and afterglow decay curves of (Ln=Er,Tm, Tb, Dy, Sm, Pr, Nd) long afterglow phosphor at 77 K and 300 K temperatures;

[0018] Figure 6 For Cs2NaLuCl6:5%Ln in Example 1 3+ , (Ln=Er,Tm, Tb, Dy, Sm, Pr, Nd) Afterglow spectra of long afterglow phosphors at 77 K.

[0019] Specific implementation manners

[0020] The present invention will be further described in detail below in conjunction with specific implementation manners, but the protection scope of the present invention is not limited

[0021] to the above content.

[0022] Example 1:

[0023] A class of full-spectrum multicolor long afterglow phosphors at 77 K with the chemical formula Cs2NaLuCl6:5%Ln 3+ , where Ln = Er, Tm, Tb, Dy, Sm, Pr or Nd. The specific preparation process of this phosphor is as follows: Prepare 1 mmol of Cs2NaLuCl6:5%Ln 3+ phosphor. Transfer 1 mmol of NaCl, 2 mmol of CsCl, 0.95 mmol of LuCl3·6H2O, and 0.05 mmol of LnCl3 (ErCl3·6H2O, TmCl3·6H2O, TbCl3·6H2O, DyCl3·6H2O, SmCl3·6H2O, PrCl3 or NdCl3·6H2O) into the inner lining of a 25 mL high-pressure reaction kettle and mix evenly. Add 5 mL of concentrated hydrochloric acid (37 wt%) to the inner lining of the reaction kettle, put a magnetic stirrer into it and turn on the magnetic stirrer to keep at a speed of 500 rpm for one hour. Subsequently, place the high-pressure reaction kettle in an oven and heat the high-pressure reaction kettle to 185 °C through the oven and keep it for 12 hours. After the reaction is completed, the high-pressure reaction kettle is naturally cooled to room temperature in the oven. Wash the obtained transparent pale yellow crystals with pure isopropanol 2-3 times to remove impurities, and then dry them at 100 °C for 5 h to obtain this type of phosphor.

[0024] Cs2NaLuCl6:5%Ln in this example 3+ , where the XRD of the long afterglow phosphor with Ln = Er, Tm, Tb, Dy, Sm, Pr or Nd is shown in Figure 1 , from Figure 1It can be seen that the diffraction peaks of the long-afterglow phosphor prepared by adding 5% of = Er, Tm, Tb, Dy, Sm, Pr or Nd are consistent with those of Cs2NaLuCl6, and the diffraction data are in good agreement with the PDF standard card, indicating that the introduction of the above seven rare earth ions will not change the crystal structure of the matrix material Cs2NaLuCl6.

[0025] The emission spectrum of the phosphor in this example after being irradiated by X-ray (tube voltage 60 kV, tube current 100 μA, power 6 W) at 77 K for 10 min is shown in Figure 2 . At 77 K and 300 K, Cs2NaLuCl6:5%Er 3+ , Cs2NaLuCl6:5%Tm 3+ , Cs2NaLuCl6:5%Tb 3+ , Cs2NaLuCl6:5%Dy 3+ , Cs2NaLuCl6:5%Sm 3+ , Cs2NaLuCl6:5%Pr 3+ , Cs2NaLuCl6:5%Nd 3+ , the positions of the emission peaks of the long-afterglow phosphors are 561 nm, 454 nm, 548 nm, 579 nm, 569 nm, 652 nm, 609 nm and 558 nm, 454 nm, 548 nm, 579 nm, 605 nm, 653 nm, 603 nm respectively. It can be seen from Figure 2 that this type of phosphor maintains excellent luminescence performance at 77 K and 300 K.

[0026] The thermoluminescence curve of the phosphor in this example written by X-ray at 77 K is as shown in Figure 3 . After that, the obtained thermoluminescence curve is subjected to peak fitting, and then the trap depth in the phosphor is calculated using the Urbach formula E = T m / 500 (E is the trap depth, T m is the temperature corresponding to the thermoluminescence peak). The trap depths of the corresponding traps in the phosphors Cs2NaLuCl6:5%Er 3+ , Cs2NaLuCl6:5%Tm 3+ , Cs2NaLuCl6:5%Tb 3+ , Cs2NaLuCl6:5%Dy 3+ , Cs2NaLuCl6:5%Sm 3+ , Cs2NaLuCl6:5%Pr 3+ , Cs2NaLuCl6:5%Nd 3+After being irradiated with X-ray (tube voltage: 60 kV, tube current: 100 μA, power: 6 W) for 10 min, the trap depth ranges are 0.23 - 0.56 eV, 0.23 - 0.57 eV, 0.23 - 0.55 eV, 0.23 - 0.59 eV, 0.23 - 0.58 eV, 0.23 - 0.59 eV, and 0.23 - 0.58 eV respectively. It can be seen that the trap depths in this type of phosphor are all less than 0.6 eV, the trap depth of room-temperature long-afterglow phosphors, indicating that this type of phosphor has relatively shallow trap depths after being irradiated with X-ray (tube voltage: 60 kV, tube current: 100 μA, power: 6 W), which is conducive to achieving efficient low-temperature long afterglow.

[0027] Phosphor Cs2NaLuCl6:5%Er 3+ 、Cs2NaLuCl6:5%Tm 3+ 、Cs2NaLuCl6:5%Tb 3+ 、Cs2NaLuCl6:5%Dy 3+ 、Cs2NaLuCl6:5%Sm 3+ 、Cs2NaLuCl6:5%Pr 3+ 、Cs2NaLuCl6:5%Nd 3+ The display diagrams of the afterglow emission colors on the CIE coordinate diagram at 77 K and 300 K temperatures are as Figure 4 shown. It can be seen that at 77 K and 300 K, the phosphor Cs2NaLuCl6:5%Tm on the CIE coordinate diagram 3+ shows blue-green emission, Cs2NaLuCl6:5%Er 3+ and Cs2NaLuCl6:5%Tb 3+ show green emission, and the emission colors of Cs2NaLuCl6:5%Dy 3+ 、Cs2NaLuCl6:5%Sm 3+ 、Cs2NaLuCl6:5%Pr 3+ and Cs2NaLuCl6:5%Nd 3+ are all concentrated in the red region, and their positions in the color coordinates do not shift significantly. The above analysis shows that the afterglow emission colors of this type of phosphor remain stable at low and room temperatures.

[0028] Phosphor Cs2NaLuCl6:5%Er 3+ 、Cs2NaLuCl6:5%Tm 3+ 、Cs2NaLuCl6:5%Tb 3+ 、Cs2NaLuCl6:5%Dy 3+, Cs2NaLuCl6:5%Sm 3+ , Cs2NaLuCl6:5%Pr 3+ , Cs2NaLuCl6:5%Nd 3+ The afterglow luminescence photographs and decay curves after irradiating for 10 min with X-ray (tube voltage is 60 kV, tube current is 100 μA, power is 6 W) at 77 K and 300 K and then turning off the X-ray source are as Figure 5 shown. It can be seen from Figure 5 that the persistent luminescence time of this type of phosphor after being irradiated with X-ray at 77 K is as long as 2 h, and the initial afterglow intensities of these seven phosphors are basically the same (900000 cps) after turning off the excitation source, and their afterglow intensities can all reach above (1500 cps) after 2 h.

[0029] Fluorescent material Cs2NaLuCl6:5%Er 3+ , Cs2NaLuCl6:5%Tm 3+ , Cs2NaLuCl6:5%Tb 3+ , Cs2NaLuCl6:5%Dy 3+ , Cs2NaLuCl6:5%Sm 3+ , Cs2NaLuCl6:5%Pr 3+ , Cs2NaLuCl6:5%Nd 3+ The afterglow spectra at each time period at 77 K are as Figure 6 shown. It can be seen from Figure 6 that the afterglow spectra can still be measured for 2 h after removing the X-ray source after irradiating this type of phosphor with X-ray (tube voltage is 60 kV, tube current is 100 μA, power is 6 W) for 10 min at 77 K, which provides significant evidence of persistent luminescence time exceeding 2 h at 77 K.

[0030] The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A type of full-spectrum multi-color long-lasting fluorescent material at low temperature of 77 K, characterized in that: The chemical formula is Cs2NaLuCl6:5%Ln 3+ , where Ln = one of Tm, Tb, Sm, Pr, Nd; the thermoluminescence curve of the above sample after being excited by X-ray at a temperature of 77 K ranges from 77 K to 300 K, with an ultra-shallow low-temperature trap of 0.23 eV, the power of the X-ray is 6 W, and the excitation time is 10 min.

2. The 77 K low temperature full spectrum multi-color long afterglow fluorescent material according to claim 1, characterized in that: After the excitation light source is removed at 77 K, it has a long afterglow luminescence characteristic and can continue to luminesce for up to 2 hours.

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