Blue light excited chromium doped binary near-infrared luminescent material and preparation method thereof

Abstract

The application belongs to the technical field of luminescent materials, and provides a blue light excited chromium-doped binary near-infrared luminescent material and a preparation method thereof. 1‑ x Cr x S, wherein 0≤x≤0.15%; the preparation method comprises the following steps: according to the chemical general formula Mg 1‑x Cr x S, the raw materials are weighed according to the molar ratio of Mg:Cr in the raw materials being 1-x:x, x being 0≤x≤0.15%, wherein the raw materials are compounds containing Mg and Cr elements respectively; the weighed raw materials are added into a dispersant and sufficiently ground to obtain a uniform white powder; the ground white powder is pre-fired at 600-700 DEG C for 2-3h, then sulfurization gas is introduced, and the material is fired at 700-800 DEG C in a sulfurization environment for 2-3h, so that the blue light excited chromium-doped binary near-infrared luminescent material is obtained. The material prepared by the application has high luminescent intensity, ideal fluorescent lifetime and is green and pollution-free.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of luminescent materials, and particularly relates to a blue light excited chromium-doped binary near-infrared luminescent material and a preparation method thereof. BACKGROUND

[0002] Wideband near-infrared spectroscopy technology has been widely applied in modern food quality analysis, night vision, biological imaging, biomedical and other fields due to its advantages of rapidity, convenience, safety and non-destructiveness. Traditional near-infrared light sources such as halogen lamps and near-infrared light-emitting diodes are difficult to meet the requirements of various applications due to their low efficiency, large size, high cost and narrow emission bandwidth. In recent years, the phosphor converted light-emitting device combining commercial high-power blue LED chips with near-infrared luminescent materials has gradually become an ideal choice for a new generation of solid-state near-infrared light sources. The near-infrared fluorescent conversion light-emitting diode not only overcomes the shortcomings of traditional near-infrared light sources, but also realizes wideband tunable emission, which has attracted widespread attention and is considered to be a new generation of near-infrared light source.

[0003] However, in the prior art, the near-infrared fluorescent conversion light-emitting diode (NIR pc-LED) combining part of the near-infrared phosphor with a blue chip also has the disadvantages of low luminescent quantum efficiency and poor thermal stability, which limits its application in some fields, especially in the wavelength band greater than 850 nm, there is still a lack of high-efficiency long-wave emitting near-infrared phosphor system. At the same time, most of the existing high-efficiency near-infrared phosphor systems need to use precious elements such as gallium, scandium, indium and tantalum, which has a high synthesis cost and is not conducive to large-scale industrial synthesis and preparation, greatly affecting the promotion and application of NIR pc-LED in the field of near-infrared light sources. Therefore, it is urgent to develop a wideband near-infrared phosphor with low price, high efficiency and good stability.

[0004] Alkaline earth sulfides such as zinc sulfide (ZnS), magnesium sulfide (MgS), calcium sulfide (CaS), strontium sulfide (SrS), barium sulfide (BaS) and the like have been used as luminescent materials for a long time due to their wide optical band gap. When doped with certain activator ions, they can produce emissions from the ultraviolet to the near-infrared region, and are generally used in light emitting devices such as field emission displays (FED), wavelength converters in solid-state safety lighting light emitting diodes (LED), cathode ray tubes and thermoluminescence dosimeters. MgS is one of the alkaline earth sulfides, which has a face-centered cubic structure. In the study of Mathur et al., the phosphor activated by rare earth elements with MgS as the matrix material was used as a radiation dose measuring instrument for optically stimulated luminescence (OSL) dosimeter and as an infrared sensor for X-ray photography (Mathur V K, Gasiot J, Abbundi R J, et al. Optically Stimulated Luminescence in MgS: Ce, Sm, Radiation Protection Dosimetry, 1986, 17(1-4): 333-336). However, the magnesium sulfide phosphor disclosed in the prior art does not have long wavelength near-infrared luminescence.

[0005] Therefore, it is of great theoretical and application value to actively explore a new type of broadband near-infrared emitting phosphor which can be effectively excited by blue light, has high efficiency and excellent performance. SUMMARY

[0006] The purpose of the embodiment of the present application is to provide a blue light excited chromium doped binary near-infrared luminescent material, which aims to solve the problems existing in the background art.

[0007] The embodiment of the present application is realized in this way, a blue light excited chromium doped binary near-infrared luminescent material, the chemical formula of the luminescent material is Mg 1-x Cr x S, wherein 0≤x≤0.15%.

[0008] Another purpose of the embodiment of the present application is to provide a preparation method of a blue light excited chromium doped binary near-infrared luminescent material, comprising the following steps:

[0009] According to the chemical formula Mg 1-x Cr x S, the raw materials are weighed according to the molar ratio of Mg:Cr in the raw materials, that is, 1-x:x, and x is 0≤x≤0.15%, wherein the raw materials are compounds containing Mg and Cr elements, respectively.

[0010] The weighed raw materials are added into a dispersant and ground sufficiently to obtain a uniform white powder, the ground white powder is pre-fired at 600-700 DEG C for 2-3h, then sulfurization gas is introduced, and the material is fired at 700-800 DEG C for 2-3h in a sulfurization environment, so that the blue light excited chromium-doped binary near-infrared luminescent material is obtained.

[0011] Preferably, the Mg-containing compound is any one of MgO, MgCO3, MgCl2, MgSO4, Mg(OH)2.

[0012] Preferably, the Mg-containing compound is MgCO3.

[0013] Preferably, the Cr-containing compound is any one of Cr2O3, Cr(OH)3, Cr2(SO4)3.

[0014] Preferably, the Cr-containing compound is Cr2O3.

[0015] Preferably, the dispersant is anhydrous ethanol.

[0016] Another purpose of the embodiment of the present application is to provide an application of the above-mentioned blue light excited chromium-doped binary near-infrared luminescent material in preparing a blue light chip excited near-infrared LED device.

[0017] The blue light excited chromium-doped binary near-infrared luminescent material Mg 1-x Cr x S provided by the embodiment of the present application takes MgS as a matrix, Mg 2+ ions can be substituted by Cr 3+ ions, and a concentration quenching phenomenon occurs with the increase of the Cr 3+ ion doping concentration, the material can be effectively excited by blue light, under 450nm excitation, a wideband near-infrared emission covering 800-1400nm can be observed, the strongest emission peak is located at 995nm, which is attributed to the electronic transition of Cr 3+ . 4 T2→ 4 A2, and the maximum half-width of the emission spectrum can reach 160nm, the luminescent material can be used for preparing a near-infrared LED device, and can be widely applied in the fields of biological identification, non-invasive monitoring, food analysis and environmental detection.

[0018] The preparation method provided by the embodiment of the present application is a gas-solid reaction method, the raw material resource reserves are abundant, the preparation method is simple and easy to implement, the synthesis temperature is relatively low, the production process is simple, the scale production is facilitated, the material powder prepared has excellent grain growth quality, has few surface defects, the product is loose and easy to crush, the scale production is easy to expand and large in quantity and will not affect the luminescence performance, the material has good physical and chemical stability, has high luminescence intensity and quantum efficiency, has ideal fluorescence lifetime, and is green and pollution-free. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 XRD patterns of samples prepared by the embodiment 1-6 and the comparative example 1 of the present application;

[0020] Figure 2 Excitation spectrum diagrams of samples prepared by the embodiment 1-6 of the present application;

[0021] Figure 3 Emission spectrum diagrams of samples prepared by the embodiment 1-6 of the present application;

[0022] Figure 4 Emission spectrum diagram of a sample prepared by the embodiment 3 of the present application under 450 nm excitation;

[0023] Figure 5 Thermal quenching curve diagram of a sample prepared by the embodiment 3 of the present application;

[0024] Figure 6 Emission intensity normalization comparison diagram of a sample prepared by the embodiment 3 of the present application at different temperatures;

[0025] Figure 7 Application comparison results of an LED device prepared by the sample of the embodiment 3 of the present application and an LED device prepared by a commercial blue light chip. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0027] A blue light excited chromium-doped binary near-infrared luminescent material, and a preparation method thereof, the preparation method comprising the following steps:

[0028] (1) according to the chemical formula Mg 1-x Cr x S, the corresponding raw materials are accurately weighed by an electronic balance according to the molar ratio of each element in the raw materials, that is, Mg:Cr=1-x:x, x is 0≤x≤0.15%, wherein the raw materials are Mg source and Cr source;

[0029] The Mg source is an oxide, chloride, hydroxide, carbonate or sulfate containing Mg;

[0030] The Cr source is an oxide, hydroxide or sulfate containing Cr;

[0031] (2) Put the weighed raw materials into a marver mortar, add anhydrous ethanol as a dispersant to grind thoroughly, grind until the alcohol volatilizes to obtain a uniform white powder, put the ground white powder into an alumina crucible, place the crucible in a tube furnace at 700 ℃ for pre-sintering for 2 h, then pass in sulfurizing gas, move the crucible to a tube furnace at 800 ℃ for sintering for 3 h in a sulfurizing environment, then slowly reduce to room temperature until cooling, and the chromium-doped near-infrared sulfide luminescent material is obtained.

[0032] The specific implementation of the present application is described in detail below in combination with specific examples.

[0033] Example 1, a blue light excited chromium-doped binary near-infrared luminescent material, the preparation method comprising the following steps:

[0034] (1) according to the chemical formula Mg 1-x Cr x S (x = 0.025%), the initial raw material is MgCO3, Cr2O3 is accurately weighed according to the stoichiometric ratio, an appropriate amount of anhydrous ethanol is added as a dispersant to grind thoroughly for 30 min, and the raw materials are mixed uniformly to obtain a mixed powder;

[0035] (2) Put the mixed powder into an alumina crucible, place the crucible in a tube furnace at 700 ℃ for pre-sintering for 2 h, then pass in sulfurizing gas, move the crucible to a tube furnace at 800 ℃ for sintering for 3 h in a sulfurizing environment, then slowly reduce to room temperature until cooling, and the chromium-doped near-infrared sulfide luminescent material is obtained.

[0036] Example 2, a blue light excited chromium-doped binary near-infrared luminescent material, the preparation method comprising the following steps:

[0037] (1) according to the chemical formula Mg 1-x Cr x S (x = 0.05%), the initial raw material is MgCO3, Cr2O3 is accurately weighed according to the stoichiometric ratio, an appropriate amount of anhydrous ethanol is added as a dispersant to grind thoroughly for 30 min, and the raw materials are mixed uniformly to obtain a mixed powder;

[0038] (2) Put the mixed powder into an alumina crucible, place the crucible in a tube furnace at 700 ℃ for pre-sintering for 2 h, then pass in sulfurizing gas, move the crucible to a tube furnace at 800 ℃ for sintering for 3 h in a sulfurizing environment, then slowly reduce to room temperature until cooling, and the chromium-doped near-infrared sulfide luminescent material is obtained.

[0039] Example 3, a blue light excited chromium doped binary near infrared luminescent material, a preparation method thereof comprising the following steps:

[0040] (1) according to the chemical formula Mg 1-x Cr x S (x = 0.075%), the initial raw material is selected from MgCO3, Cr2O3 is accurately weighed according to the stoichiometric ratio, and a proper amount of anhydrous ethanol is added as a dispersant to fully grind for 30 min, so that the raw materials are uniformly mixed to obtain a mixed powder;

[0041] (2) the mixed powder is put into an alumina crucible, the crucible is placed in a tube furnace at 700 DEG C, and pre-sintering is carried out for 2h, then sulfurization gas is introduced, the crucible is moved to an 800 DEG C tube furnace, and sintering is carried out in a sulfurization environment for 3h, then it is slowly cooled to room temperature until it is cooled.

[0042] Example 4, a blue light excited chromium doped binary near infrared luminescent material, a preparation method thereof comprising the following steps:

[0043] (1) according to the chemical formula Mg 1-x Cr x S (x = 0.1%), the initial raw material is selected from MgCO3, Cr2O3 is accurately weighed according to the stoichiometric ratio, and a proper amount of anhydrous ethanol is added as a dispersant to fully grind for 30 min, so that the raw materials are uniformly mixed to obtain a mixed powder;

[0044] (2) the mixed powder is put into an alumina crucible, the crucible is placed in a tube furnace at 700 DEG C, and pre-sintering is carried out for 2h, then sulfurization gas is introduced, the crucible is moved to an 800 DEG C tube furnace, and sintering is carried out in a sulfurization environment for 3h, then it is slowly cooled to room temperature until it is cooled.

[0045] Example 5, a blue light excited chromium doped binary near infrared luminescent material, a preparation method thereof comprising the following steps:

[0046] (1) according to the chemical formula Mg 1-x Cr x S (x = 0.125%), the initial raw material is selected from MgCO3, Cr2O3 is accurately weighed according to the stoichiometric ratio, and a proper amount of anhydrous ethanol is added as a dispersant to fully grind for 30 min, so that the raw materials are uniformly mixed to obtain a mixed powder;

[0047] (2) the mixed powder is put into an alumina crucible, the crucible is placed in a tube furnace at 700 DEG C, and pre-sintering is carried out for 2h, then sulfurization gas is introduced, the crucible is moved to an 800 DEG C tube furnace, and sintering is carried out in a sulfurization environment for 3h, then it is slowly cooled to room temperature until it is cooled.

[0048] Example 6, a blue light excited chromium doped binary near infrared luminescent material, a preparation method thereof comprising the following steps:

[0049] (1) Mg 1-x Cr x S (x = 0.15%), the initial raw material is selected as MgCO3, Cr2O3 is accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind for 30 min, so that the raw materials are uniformly mixed to obtain a mixed powder;

[0050] (2) The mixed powder is placed in an alumina crucible, the crucible is placed in a tube furnace at 700°C, and pre-sintering is performed for 2 h, then sulfurization gas is introduced, the crucible is moved to an 800°C tube furnace for sintering in a sulfurization environment for 3 h, and then slowly cooled to room temperature until cooling.

[0051] Comparative Example 1, a MgS, a preparation method comprising the following steps:

[0052] (1) Mg 1-x Cr x S (x = 0), i.e. MgS, MgCO3 is weighed, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind for 30 min, so that the raw materials are uniformly mixed to obtain a powder;

[0053] (2) The powder is placed in an alumina crucible, the crucible is placed in a tube furnace at 700°C, and pre-sintering is performed for 2 h, then sulfurization gas is introduced, the crucible is moved to an 800°C tube furnace for sintering in a sulfurization environment for 3 h, and then slowly cooled to room temperature until cooling.

[0054] Performance test:

[0055] The samples prepared in Examples 1-6 and Comparative Example 1 are analyzed by powder X-ray diffraction (XRD) technology, and the XRD patterns are as shown in Figure 1 Comparing the XRD data of all the synthesized samples with the MgS standard card (PDF # 35-0730), it can be seen that all the prepared samples are free of impurity phases;

[0056] Figure 2 and Figure 3 The excitation and emission spectra of the samples prepared in Examples 1-6 are given, it can be seen that the excitation spectrum is composed of two wide peaks, located near 310 and 450 nm, the absorption bands corresponding to the positions of the two excitation peaks are attributed to the Cr 3+ ions 4 A2( 4 F)→ 4 T1( 4 F) transition, under 450 nm excitation, a broadband near-infrared emission covering 800-1400 nm can be observed, the strongest emission peak is located at 995 nm, and the maximum half-peak width can reach 160 nm; and through spectral testing, the Mg 1-xCr x S(x=0), i.e. MgS, has no emission signal response under 468 nm excitation, indicating that the sample has no near-infrared luminescence;

[0057] Figure 4 The optimal emission wavelength and half-peak width in the emission spectrum of the sample prepared in Example 3 are given, and it can be seen that the sample exhibits near-infrared broadband emission with an optimal emission wavelength of 995 nm under 450 nm excitation, and the half-peak width is 160 nm. The results show that the material prepared in the embodiment of the application can be widely used in the field of near-infrared spectroscopy.

[0058] Figure 5 The thermal quenching spectrum of the sample prepared in Example 3 is given, and the results show that the emission intensity gradually decreases with increasing temperature, and the sample exhibits good thermal stability.

[0059] Figure 6 The normalized comparison diagram of the emission intensity of the sample prepared in Example 3 at different temperatures is given, and it can be seen that when the temperature is increased to 413 K (150℃), the emission intensity still maintains 56.7% of the initial intensity.

[0060] The sample prepared in Example 3 is used to prepare an LED device, and the LED device is compared with an LED device prepared by a commercial blue light chip, and the results are shown in Figure 7 Figure 7 a and Figure 7 b are schematic diagrams of ordinary cameras in a natural indoor light environment without power, Figure 7 c and ​ d are observation diagrams of night vision cameras in a dark environment with power. Under the irradiation of the powered NIR pc-LED device, the night vision camera can clearly observe the schematic diagram of the object and the human hand after the filter, and it can be seen that the NIR pc-LED prepared by the material of the embodiment of the application can pass through human tissues, indicating that the material has great application potential in the fields of biological recognition, non-invasive monitoring, etc.

[0061] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement and improvement made within the spirit and principle of the application shall be included in the protection scope of the application.​

Claims

1. A blue light excited chromium doped binary near infrared luminescent material, characterized in that, The chemical formula of the luminescent material is Mg 1-x Cr x S, wherein 0.025%≤x≤0.15%. The preparation method of the blue light excited chromium doped binary near-infrared luminescent material comprises the following steps: According to the chemical formula Mg 1-x Cr x S, the raw materials are taken according to the molar ratio of each element in the raw materials Mg:Cr = 1-x:x, x is 0.025%≤x≤0.15%, wherein the raw materials are compounds containing Mg and Cr elements respectively; The weighed raw materials are added into a dispersant and ground sufficiently to obtain a uniform white powder, the ground white powder is pre-fired at 600-700 DEG C for 2-3h, then sulfurizing gas is introduced, and the material is fired at 700-800 DEG C for 2-3h in a sulfurizing environment, thereby obtaining the blue light excited chromium doped binary near-infrared luminescent material.

2. The blue light excited Cr-doped binary near-infrared luminescent material according to claim 1, characterized in that, The compound containing Mg elements is any one of MgO, MgCO3, MgCl2, MgSO4 and Mg(OH)2.

3. The blue light excited Cr-doped binary near-infrared luminescent material according to claim 2, characterized in that, The compound containing Mg elements is MgCO3.

4. The blue excitation Cr-doped binary near-infrared luminescent material of claim 1, wherein, The compound containing Cr elements is any one of Cr2O3, Cr(OH)3 and Cr2(SO4)3.

5. The blue light excited Cr-doped binary near-infrared luminescent material according to claim 4, characterized in that, The compound containing Cr elements is Cr2O3.

6. The blue excitation Cr-doped binary near-infrared luminescent material of claim 1, wherein, The dispersant is anhydrous ethanol.

7. Use of the blue light excited chromium doped binary near-infrared luminescent material according to claim 1 in the preparation of a blue chip excited near-infrared LED device.

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