Long-wavelength ultra-wideband sulfide near-infrared luminescent material as well as preparation method and application thereof

Abstract

The invention is applicable to the technical field of luminescent materials, and provides a long-wavelength ultra-wideband sulfide near-infrared luminescent material and a preparation method and application thereof, the general chemical formula of the luminescent material is Ca < 1-x > CrxS, and x is more than or equal to 0 and less than or equal to 0.125%; the preparation method comprises the following steps that raw materials are weighed according to the chemical general formula Ca < 1-x > CrxS and the molar ratio of Ca to Cr in the raw materials being 1-x: x, x is larger than or equal to 0 and smaller than or equal to 0.125%, and the raw materials are compounds containing Ca 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 700-800 DEG C for 2-3 hours, introducing vulcanizing gas, and sintering in a vulcanizing environment at 800-900 DEG C for 2-3 hours to obtain the long-wavelength ultra-wideband sulfide near-infrared luminescent material. The luminescent material provided by the invention is excellent in performance, can effectively meet the requirements of near-infrared LED devices, and is widely applied to the fields of modern food quality analysis, biological imaging, biomedicine and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of luminescent materials, and in particular relates to a long-wavelength ultra-wideband sulfide near-infrared luminescent material and a preparation method and application thereof. Background Art

[0002] Near infrared region II (NIR-II) is located between 1000 and 1700 nm, and has the advantages of low scattering, deep penetration, and high signal-to-background ratio, which can realize sensitive chemical bond detection and is highly favored in sensing applications. Since NIR-II light scatters and absorbs less than NIR-I light, and can cover the vibration absorption of many functional groups, it has good application prospects in many fields such as information storage, optical imaging, bioimaging, optical switching, and non-destructive analysis. At the same time, its wide application has led to an increasing demand for phosphor-converted light-emitting diodes (pc-LEDs) with NIR-II emission.

[0003] Transition metal ion Cr 3+ It is the most ideal near-infrared activator reported so far, and when it is located in a weak octahedral coordinated crystal field, it usually produces broadband emission in the range of 650-1200nm; in addition, due to its 4 A 2g → 4 T 1g Spin-allowed transitions, Cr 3+ Ions usually have strong broadband absorption at around 460nm, which is compatible with commercial blue LED chips. However, the prior art with publication number CN117070215A discloses a phosphate near-infrared luminescent material and its preparation method and application, which discloses Cr 3+ The emission peak wavelength of ion-activated near-infrared phosphors is shorter than 1000 nm, and the full width at half maximum (FWHM) is below 200 nm, which will limit the detection range and accuracy of spectral applications. Therefore, it is urgent to develop an ultra-broadband near-infrared second-zone emitting phosphor with excellent luminescence performance.

[0004] Alkaline earth sulfides such as zinc sulfide (ZnS), magnesium sulfide (MgS), calcium sulfide (CaS), strontium sulfide (SrS), and barium sulfide (BaS) usually have wide optical band gaps and have long been used as luminescent materials. When doped with certain activator ions, they can be effectively excited by ultraviolet or visible light to produce emission peaks with wide half-widths in the ultraviolet to near-infrared region. The lower phonon energy in alkaline earth sulfides reduces the probability of non-radiative relaxation, and their strong covalency is expected to reduce the center of gravity of the d orbital energy level of the luminescence center, thereby achieving long-wavelength near-infrared emission that is difficult to achieve in oxide materials. Therefore, alkaline earth sulfide luminescent materials have been widely used in the fields of photoluminescence, electroluminescence, and cathodoluminescence. Lehmann first reported the results of a detailed and systematic study of CaS doped with a large amount of activators and co-doped (Lehmann W. Activators and co-activators in calcium sulfide phosphors [J]. Journal of Luminescence, 1972, 5 (2): 87-107.). However, the calcium sulfide phosphor disclosed in the above prior art does not emit near-infrared light.

[0005] Therefore, actively exploring a new type of ultra-wideband near-infrared second-zone emitting phosphor that can be effectively excited by blue light 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 long-wavelength ultra-wideband sulfide near-infrared luminescent material, aiming to solve the problems raised in the above background technology.

[0007] The embodiment of the present invention is implemented as follows: a long-wavelength ultra-wideband sulfide near-infrared luminescent material, the chemical formula of which is Ca 1-x Cr x S, where 0≤x≤0.125%.

[0008] Another object of the embodiment of the present invention is to provide a method for preparing a long-wavelength ultra-wideband sulfide near-infrared luminescent material, comprising the following steps: According to the chemical formula Ca 1-x Cr x S, weigh the raw materials according to the molar ratio of each element in the raw materials Ca:Cr=1-x:x, x is 0≤x≤0.125%, wherein the raw materials are compounds containing Ca 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-calcined at 700-800°C for 2-3 hours, and then a sulfiding gas is introduced and the powder is calcined at 800-900°C for 2-3 hours to obtain the long-wavelength ultra-wideband sulfide near-infrared luminescent material.

[0009] Preferably, the compound containing the Ca element is any one of CaO, CaCO3, CaCl2, CaSO4, and Ca(OH)2.

[0010] Preferably, the compound containing the Ca element is CaCO3.

[0011] Preferably, the compound containing Cr element is any one of Cr2O3, Cr(OH)3, and Cr2(SO4)3.

[0012] Preferably, the compound containing Cr element is Cr2O3.

[0013] Preferably, the dispersant is anhydrous ethanol.

[0014] Another object of an embodiment of the present invention is to provide an application of a long-wavelength ultra-wideband sulfide near-infrared luminescent material in preparing a near-infrared LED device excited by a blue light chip.

[0015] A long-wavelength ultra-wideband sulfide near-infrared luminescent material Ca 1-x Cr x S, Ca in the chemical formula 2+ ions can be Cr 3+ ion replacement, and with the Cr 3+ Concentration quenching occurs during the increase of ion doping concentration. The luminescent material can be effectively excited by blue light. Under 468nm excitation, broadband near-infrared emission covering 900~1650nm can be observed, with the strongest emission peak at 1170nm, which is attributed to Cr 3+ of 4 T2→ 4 A2's electronic transition, the maximum half-peak width of the emission spectrum can reach 310nm, with good physical and chemical stability, ideal fluorescence lifetime, green and pollution-free. It can be used as a broadband near-infrared sulfide luminescent material excited by a blue light chip to prepare near-infrared LED devices, which can be widely used in plant lighting and night vision imaging. The preparation method provided in the embodiment of the present invention uses a gas-solid reaction method, the raw material resources used are abundant, the synthesis temperature is relatively low, the method is simple and easy to implement, the production process is simple, and it is convenient for large-scale production. The prepared product powder has excellent grain growth quality and few surface defects. The product is loose and easy to crush, easy to expand the scale for large-scale production, and will not affect its luminescence performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 XRD patterns of samples prepared in Examples 1-5 and Comparative Example 1 of the present invention; Figure 2 The excitation spectra of the samples prepared in Examples 1-5 of the present invention; Figure 3 The emission spectra of the samples prepared in Examples 1-5 of the present invention; Figure 4 This is the emission spectrum of the sample prepared in Example 2 of the present invention under 468nm excitation; Figure 5 This is a thermal quenching curve diagram of the sample prepared in Example 2 of the present invention; Figure 6 This is a normalized comparison diagram of emission intensities of samples prepared in Example 2 of the present invention at different temperatures; Figure 7 The results of application comparison between the LED device prepared by the sample of Example 2 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 long-wavelength ultra-wideband sulfide near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Ca 1-x Cr x S, according to the molar ratio of each element in the raw material Ca:Cr=1-x:x, the corresponding raw materials are accurately weighed with an electronic balance, x is 0≤x≤0.125%, where the raw materials are Ca source and Cr source respectively; The Ca source is an oxide, chloride, hydroxide, carbonate or sulfate containing Na; 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 tube furnace at 800°C for pre-burning for 2 hours. Then, a sulfiding gas is introduced, and the crucible is moved to a tube furnace at 900°C for burning for 3 hours in a sulfiding environment. The temperature is then slowly cooled to room temperature until it cools down, thereby obtaining the long-wavelength ultra-wideband sulfide near-infrared luminescent material.

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

[0020] Embodiment 1: A long-wavelength ultra-wideband sulfide near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Ca 1-x Cr x S (x = 0.025%), the initial raw materials are CaCO3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind 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 tube furnace at 800°C for 2 hours, then introduce sulfiding gas, move the crucible to a tube furnace at 900°C and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0021] Embodiment 2: A long-wavelength ultra-wideband sulfide near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Ca 1-x Cr x S (x = 0.05%), the initial raw materials are CaCO3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind 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 tube furnace at 800°C for 2 hours, then introduce sulfiding gas, move the crucible to a tube furnace at 900°C and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0022] Embodiment 3: A long-wavelength ultra-wideband sulfide near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Ca 1-x Cr x S (x = 0.075%), the initial raw materials are CaCO3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind 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 tube furnace at 800°C for 2 hours, then introduce sulfiding gas, move the crucible to a tube furnace at 900°C and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0023] Embodiment 4: A long-wavelength ultra-wideband sulfide near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Ca 1-x Cr xS (x = 0.1%), the initial raw materials are CaCO3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind 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 tube furnace at 800°C for 2 hours, then introduce sulfiding gas, move the crucible to a tube furnace at 900°C and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0024] Embodiment 5: A long-wavelength ultra-wideband sulfide near-infrared luminescent material, the preparation method of which comprises the following steps: (1) According to the chemical formula Ca 1-x Cr x S (x = 0.125%), the initial raw materials are CaCO3 and Cr2O3, which are accurately weighed according to the stoichiometric ratio, and an appropriate amount of anhydrous ethanol is added as a dispersant to fully grind 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 tube furnace at 800°C for 2 hours, then introduce sulfiding gas, move the crucible to a tube furnace at 900°C and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0025] Comparative Example 1: A method for preparing CaS comprising the following steps: (1) According to the chemical formula Ca 1-x Cr x S (x = 0), i.e., CaS composition, weigh CaCO3, 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 tube furnace at 800°C for 2 hours, then introduce sulfiding gas, move the crucible to a tube furnace at 900°C and sinter for 3 hours in a sulfiding environment, then slowly cool to room temperature until cooled.

[0026] Performance Testing: The samples prepared in Examples 1-5 and Comparative Example 1 were analyzed using powder X-ray diffraction (XRD) technology to obtain XRD patterns as shown in Figure 1 As shown, all synthesized sample XRD data were compared with CaS standard cards (PDF#08-0464), and all prepared samples had no impurity phase; Figure 2 and Figure 3 The excitation and emission spectra of the samples prepared in Examples 1-5 are given, and it can be seen that The excitation spectrum consists of three broad peaks located near 260, 360 and 468 nm. The absorption bands corresponding to the three excitation peaks are attributed to Cr 3+ Ionic 4 A2( 4 F) → 4 T1( 4 F)、T1 ( 4 F) and 4 T2 ( 4 F) transition, under 450nm excitation, broadband near-infrared emission covering 900~1650nm can be observed, and the strongest emission peak is located at 1170nm; and through spectral testing, the Ca prepared in Comparative Example 1 1-x Cr x S (x = 0), i.e., CaS, has no emission signal response under 468 nm excitation, indicating that the sample has no near-infrared luminescence; Figure 4 The optimal emission wavelength and half-peak width in the emission spectrum of the sample prepared in Example 2 are given. It can be seen that the sample exhibits broadband emission in the near-infrared second region under 468nm excitation, with a half-peak width of 310nm and an optimal emission wavelength of 1170nm. 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.

[0027] Figure 5 The thermal quenching spectrum of the sample prepared in Example 2 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 2 at different temperatures is given. It can be seen that when the temperature rises to 150°C, its emission intensity still maintains 52.8% of the initial intensity; The sample prepared in Example 2 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 visible. It is obvious 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 long-wavelength ultra-wideband sulfide near-infrared luminescent material, characterized in that: The chemical formula of the luminescent material is Ca 1-x Cr x S, where 0≤x≤0.125%.

2. A method for preparing the long-wavelength ultra-wideband sulfide near-infrared luminescent material according to claim 1, characterized in that: The following steps are involved: According to the chemical formula Ca 1-x Cr x S, weigh the raw materials according to the molar ratio of each element in the raw materials Ca:Cr=1-x:x, x is 0≤x≤0.125%, wherein the raw materials are compounds containing Ca 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-calcined at 700-800°C for 2-3 hours, and then a sulfiding gas is introduced and the powder is calcined at 800-900°C for 2-3 hours to obtain the long-wavelength ultra-wideband sulfide near-infrared luminescent material.

3. The method for preparing the long-wavelength ultra-wideband sulfide near-infrared luminescent material according to claim 2, characterized in that: The compound containing Ca element is any one of CaO, CaCO3, CaCl2, CaSO4, and Ca(OH)2.

4. The method for preparing the long-wavelength ultra-wideband sulfide near-infrared luminescent material according to claim 3, characterized in that: The compound containing Ca element is CaCO3.

5. The method for preparing the long-wavelength ultra-wideband sulfide 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 long-wavelength ultra-wideband sulfide near-infrared luminescent material according to claim 5, characterized in that: The compound containing Cr element is Cr2O3.

7. The long-wavelength ultra-wideband sulfide near-infrared luminescent material according to claim 2, characterized in that: The dispersant is anhydrous ethanol.

8. Use of the long-wavelength ultra-wideband sulfide 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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