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

Abstract

The invention is applicable 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, the chemical general formula of the luminescent material is Mg1-xCrxS, and x is greater than or equal to 0 and less than or equal to 0.15%; the preparation method comprises the following steps that raw materials are weighed according to the general chemical formula Mg < 1-x > CrxS and the molar ratio of Mg to Cr in the raw materials being 1-x: x, x is larger than or equal to 0 and smaller than or equal to 0.15%, and the raw materials are compounds containing Mg and Cr elements; the preparation method comprises the following steps: weighing raw materials, adding a dispersing agent into the weighed raw materials, fully grinding to obtain uniform white powder, pre-sintering the ground white powder at 600-700 DEG C for 2-3 hours, introducing vulcanizing gas, and sintering in a vulcanizing environment at 700-800 DEG C for 2-3 hours to obtain the blue-light-excited chromium-doped binary near-infrared luminescent material. The material prepared by the invention has high luminous intensity, ideal fluorescence lifetime, and is green and pollution-free.

Description

Technical Field

[0001] The present invention belongs to the technical field of luminescent materials, and in particular relates to a blue light excited chromium doped binary near-infrared luminescent material and a preparation method thereof. Background Art

[0002] Broadband near-infrared spectroscopy technology has been widely used in modern food quality analysis, night vision, bioimaging, biomedicine and other fields due to its advantages such as 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 shortcomings such as low efficiency, large size, high cost and narrow emission bandwidth. In recent years, phosphor-converted light-emitting devices that combine commercial high-power blue LED chips with near-infrared luminescent materials are gradually becoming the ideal choice for a new generation of solid-state near-infrared light sources. Near-infrared phosphor-converted light-emitting diodes not only overcome the shortcomings of traditional near-infrared light sources, but also can achieve broadband tunable emission, which has attracted widespread attention and is considered to be a new generation of near-infrared light sources.

[0003] However, in the prior art, some near-infrared phosphors and blue light chips in the near-infrared fluorescence conversion light-emitting diode (NIR pc-LED) also have the disadvantages of low luminous quantum efficiency and poor thermal stability, which limits its application in some fields, especially in the wavelength band greater than 850nm, there is still a lack of efficient long-wave emission near-infrared phosphor system; at the same time, most of the existing high-efficiency near-infrared phosphor systems require the use of precious elements such as gallium, scandium, indium, and tantalum, and the synthesis cost is high, which 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 broadband 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), etc. usually have a wide optical band gap and have long been used as luminescent materials. When doped with certain activator ions, they can produce emissions from the ultraviolet to the near-infrared region. They are generally used in light-emitting devices such as field emission displays (FEDs), wavelength converters in light-emitting diodes (LEDs) for solid security lighting, cathode ray tubes, and thermoluminescent dosimeters. MgS is a kind of alkaline earth sulfide with a face-centered cubic structure. In the research of Mathur et al., MgS was used as the matrix material and phosphors activated by rare earth elements were used for radiation dose measurement of optically stimulated luminescence (OSL) dosimeters and as infrared sensors for X-ray photography (Mathur VK, Gasiot J, Abbundi RJ, et al. Optically Stimulated Luminescencein MgS: ​​Ce, Sm, Radiation Protection Dosimetry, 1986, 17(1-4): 333-336). However, the magnesium sulfide phosphors disclosed in the prior art do not have long-wavelength near-infrared luminescence.

[0005] Therefore, actively exploring a new type of broadband near-infrared emitting phosphor that can be effectively excited by blue light, is efficient, and has excellent performance has important theoretical and application value. Summary of the invention

[0006] The purpose of the embodiments of the present invention is to provide a blue light excited chromium doped binary near-infrared luminescent material, aiming to solve the problems existing in the above-mentioned background technology.

[0007] The embodiment of the present invention is implemented as follows: a blue light-excited chromium-doped binary near-infrared luminescent material, the chemical formula of which is Mg 1-x Cr x S, where 0≤x≤0.15%.

[0008] Another object of the embodiment of the present invention is to provide a method for preparing a blue light excited chromium doped binary near-infrared luminescent material, comprising the following steps: According to the chemical formula Mg 1-x Cr x S, weigh the raw materials according to the molar ratio of each element in the raw materials Mg:Cr=1-x:x, x is 0≤x≤0.15%, wherein the raw materials are compounds containing Mg and Cr elements respectively; The weighed raw materials are added with a dispersant and fully ground to obtain a uniform white powder. The ground white powder is pre-sintered at 600-700°C for 2-3 hours, and then a sulfiding gas is introduced and the powder is fired at 700-800°C for 2-3 hours to obtain a blue light-excited chromium-doped binary near-infrared luminescent material.

[0009] Preferably, the compound containing Mg element is MgO, MgCO 3 MgCl 2 MgSO 4 Mg(OH) 2 Any of .

[0010] Preferably, the compound containing Mg element is MgCO 3 .

[0011] Preferably, the compound containing Cr element is Cr 2 O 3 、Cr(OH) 3 Cr 2 (SO 4 ) 3 Any of .

[0012] Preferably, the compound containing Cr element is Cr 2 O 3 .

[0013] Preferably, the dispersant is anhydrous ethanol.

[0014] Another object of an embodiment of the present invention is to provide an application of the above-mentioned chromium-doped binary near-infrared luminescent material excited by blue light in the preparation of a near-infrared LED device excited by a blue light chip.

[0015] A blue light-excited chromium-doped binary near-infrared luminescent material Mg 1-x Cr x S, MgS as the matrix, Mg 2+ ions can be Cr 3+ ion replacement, and with the Cr 3+ Concentration quenching occurs during the increase of ion doping concentration. The material can be effectively excited by blue light. Under 450nm excitation, broadband near-infrared emission covering 800-1400nm can be observed, with the strongest emission peak at 995nm, which is attributed to Cr 3+ of 4 T 2 → 4 A 2The maximum half-peak width of the emission spectrum can reach 160nm. This luminescent material can be used to prepare near-infrared LED devices, which can be widely used in biometrics, non-invasive monitoring, food analysis and environmental testing. The preparation method provided by the embodiment of the present invention is a gas-solid reaction method. The raw material resources used are abundant in reserves, the preparation method is simple and easy, the synthesis temperature is relatively low, the production process is simple, and it is convenient for large-scale production. The prepared material powder has excellent grain growth quality, few surface defects, and the product is loose and easy to crush. It is easy to expand the proportion of large-scale production without affecting its luminescence performance. It has good physicochemical stability, high luminescence intensity and quantum efficiency, ideal fluorescence lifetime, and is green and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 XRD patterns of samples prepared in Examples 1-6 and Comparative Example 1 of the present invention; Figure 2 The excitation spectra of the samples prepared in Examples 1-6 of the present invention; Figure 3 The emission spectra of the samples prepared in Examples 1-6 of the present invention; Figure 4 This is the emission spectrum of the sample prepared in Example 3 of the present invention under 450nm excitation; Figure 5 This is a thermal quenching curve diagram of the sample prepared in Example 3 of the present invention; Figure 6 This is a normalized comparison diagram of emission intensities of samples prepared in Example 3 of the present invention at different temperatures; Figure 7 The results of application comparison between the LED device prepared by the sample of Example 3 of the present invention and the LED device prepared by a commercial blue light chip. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] A blue light excited chromium doped binary near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Mg 1-x Cr x S, accurately weigh the corresponding raw materials using an electronic balance according to the molar ratio of each element in the raw materials Mg:Cr=1-x:x, x is 0≤x≤0.15%, where the raw materials are Mg source and Cr source respectively; The Mg source is an oxide, chloride, hydroxide, carbonate or sulfate containing Mg; The Cr source is an oxide, hydroxide or sulfate containing Cr; (2) The weighed raw materials are placed in an agate mortar, and anhydrous ethanol is added as a dispersant to grind the raw materials thoroughly until the alcohol evaporates to obtain a uniform white powder. The ground white powder is placed in an alumina crucible, and the crucible is placed in a 700°C tubular furnace for pre-burning for 2 h. Then, a sulfiding gas is introduced, and the crucible is moved to an 800°C tubular furnace for burning for 3 h in a sulfiding environment. The temperature is then slowly cooled to room temperature until it cools down, thereby obtaining the chromium-doped near-infrared sulfide luminescent material.

[0019] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0020] Embodiment 1: A blue light excited chromium doped binary near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Mg 1-x Cr x S (x = 0.025%), the initial raw material is MgCO 3 ,Cr 2 O 3 Accurately weigh according to the stoichiometric ratio, add an appropriate amount of anhydrous ethanol as a dispersant and grind thoroughly for 30 minutes to mix the raw materials evenly to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, pre-sinter the crucible in a 700°C tubular furnace for 2 hours, then introduce sulfiding gas, move the crucible to an 800°C tubular furnace and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0021] Embodiment 2: A blue light excited chromium doped binary near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Mg 1-x Cr x S(x=0.05%), the initial raw material is MgCO 3 ,Cr 2 O 3 Accurately weigh according to the stoichiometric ratio, add an appropriate amount of anhydrous ethanol as a dispersant and grind thoroughly for 30 minutes to mix the raw materials evenly to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, pre-sinter the crucible in a 700°C tubular furnace for 2 hours, then introduce sulfiding gas, move the crucible to an 800°C tubular furnace and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0022] Embodiment 3: A blue light excited chromium doped binary near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Mg 1-x Cr x S (x = 0.075%), the initial raw material is MgCO 3 ,Cr 2 O 3 Accurately weigh according to the stoichiometric ratio, add an appropriate amount of anhydrous ethanol as a dispersant and grind thoroughly for 30 minutes to mix the raw materials evenly to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, pre-sinter the crucible in a 700°C tubular furnace for 2 hours, then introduce sulfiding gas, move the crucible to an 800°C tubular furnace and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0023] Embodiment 4: A blue light excited chromium doped binary near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Mg 1-x Cr x S(x=0.1%), the initial raw material is MgCO 3 ,Cr 2 O 3 Accurately weigh according to the stoichiometric ratio, add an appropriate amount of anhydrous ethanol as a dispersant and grind thoroughly for 30 minutes to mix the raw materials evenly to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, pre-sinter the crucible in a 700°C tubular furnace for 2 hours, then introduce sulfiding gas, move the crucible to an 800°C tubular furnace and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0024] Example 5: A blue light excited chromium doped binary near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Mg 1-x Cr x S (x = 0.125%), the initial raw material is MgCO 3 ,Cr 2 O 3 Accurately weigh according to the stoichiometric ratio, add an appropriate amount of anhydrous ethanol as a dispersant and grind thoroughly for 30 minutes to mix the raw materials evenly to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, pre-sinter the crucible in a 700°C tubular furnace for 2 hours, then introduce sulfiding gas, move the crucible to an 800°C tubular furnace and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0025] Example 6: A blue light excited chromium doped binary near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Mg1-x Cr x S (x = 0.15%), the initial raw material is MgCO 3 ,Cr 2 O 3 Accurately weigh according to the stoichiometric ratio, add an appropriate amount of anhydrous ethanol as a dispersant and grind thoroughly for 30 minutes to mix the raw materials evenly to obtain a mixed powder; (2) Place the mixed powder into an alumina crucible, pre-sinter the crucible in a 700°C tubular furnace for 2 hours, then introduce sulfiding gas, move the crucible to an 800°C tubular furnace and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0026] Comparative Example 1: A method for preparing MgS comprising the following steps: (1) According to the chemical formula Mg 1-x Cr x S(x=0), namely MgS, weigh MgCO 3 , add an appropriate amount of anhydrous ethanol as a dispersant and grind thoroughly for 30 minutes to mix the raw materials evenly to obtain powder; (2) Place the powder into an alumina crucible, pre-sinter the crucible in a 700°C tubular furnace for 2 hours, then introduce sulfiding gas, move the crucible to an 800°C tubular furnace and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0027] Performance Testing: The samples prepared in Examples 1-6 and Comparative Example 1 were analyzed using powder X-ray diffraction (XRD) technology to obtain XRD patterns as shown in Figure 1 As shown, by comparing the XRD data of all synthesized samples with the MgS standard card (PDF#35-0730), it can be seen that all prepared samples have no impurity phase; 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 consists of two broad peaks, located near 310 and 450 nm respectively. The absorption bands corresponding to the two excitation peaks are attributed to Cr 3+ Ionic 4 A 2 ( 4 F) → 4 T 1 ( 4 F) transition, under 450nm excitation, broadband near-infrared emission covering 800~1400nm can be observed, the strongest emission peak is located at 995nm, and the maximum half-peak width can reach 160nm; and through spectral testing, the Mg prepared in Comparative Example 1 1-x Crx S(x=0), i.e., MgS, has no emission signal response under 468nm excitation, indicating that the sample has no near-infrared luminescence; Figure 4 The optimal emission wavelength and half-peak width of the emission spectrum of the sample prepared in Example 3 are given. It can be seen that the sample exhibits near-infrared broadband emission with an optimal emission wavelength of 995nm under 450nm excitation, and its half-peak width is 160nm. The results show that the material prepared in the embodiment of the present invention can be widely used in the field of near-infrared spectroscopy technology; Figure 5 The thermal quenching spectrum of the sample prepared in Example 3 is given. The results show that as the temperature increases, the emission intensity gradually decreases, and the sample exhibits relatively good thermal stability; Figure 6 A normalized comparison chart of the emission intensity of the sample prepared in Example 3 at different temperatures is given. It can be seen that when the temperature rises to 413K (150°C), the emission intensity still maintains 56.7% of the initial intensity; The sample prepared in Example 3 was used to prepare an LED device, and the LED device was compared with an LED device prepared from a commercial blue light chip. The results are as follows: Figure 7 As shown, Figure 7 a and Figure 7 b is a schematic diagram of an ordinary camera in an indoor natural light environment without power supply. Figure 7 c and Figure 7 d is an observation picture of a night vision camera in a dark environment with power on. Under the illumination of the powered NIRpc-LED device, the night vision camera observes the objects behind the filter and the schematic diagram of the human hand clearly. It can be seen that the NIR pc-LED prepared using the material of the embodiment of the present invention can pass through human tissue, indicating that the material has great application potential in the fields of biometrics, non-invasive monitoring, etc.

[0028] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

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, where 0≤x≤0.15%.

2. A method for preparing the blue light excited chromium doped binary near-infrared luminescent material as claimed in claim 1, characterized in that: The following steps are involved: According to the chemical formula Mg 1-x Cr x S, weigh the raw materials according to the molar ratio of each element in the raw materials Mg:Cr=1-x:x, x is 0≤x≤0.15%, wherein the raw materials are compounds containing Mg and Cr elements respectively; The weighed raw materials are added with a dispersant and fully ground to obtain a uniform white powder. The ground white powder is pre-sintered at 600-700°C for 2-3 hours, and then a sulfiding gas is introduced and the powder is fired at 700-800°C for 2-3 hours to obtain a blue light-excited chromium-doped binary near-infrared luminescent material.

3. The method for preparing the blue light excited chromium doped binary near-infrared luminescent material according to claim 2, characterized in that: The compound containing Mg element is any one of MgO, MgCO3, MgCl2, MgSO4, and Mg(OH)2.

4. The method for preparing the blue light excited chromium doped binary near-infrared luminescent material according to claim 3, characterized in that: The compound containing Mg element is MgCO3.

5. The method for preparing the blue light excited chromium doped binary near-infrared luminescent material according to claim 2, characterized in that: The compound containing Cr element is any one of Cr2O3, Cr(OH)3, and Cr2(SO4)3.

6. The method for preparing the blue light excited chromium doped binary near-infrared luminescent material according to claim 5, characterized in that: The compound containing Cr element is Cr2O3.

7. The method for preparing the blue light excited chromium doped binary near-infrared luminescent material according to claim 2, characterized in that: The dispersant is anhydrous ethanol.

8. Use of the blue light excited chromium doped binary near-infrared luminescent material as claimed in claim 1 in preparing a near-infrared LED device excited by a blue light chip.

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