A NIR-II~III phosphor, its preparation method and application

Abstract

This invention discloses a NIR-II~III phosphor, its preparation method, and its applications. The phosphor has the chemical formula Ba2La2Zn. 1‑x W2O 12 :xNi 2+ Where x = 0.3~3.0 mol; this phosphor is based on a hexagonal close-packed structure, Ni 2+ Ions occupy octahedral sites in [ZnO6], and through crystal field modulation and impurity energy level design, ultra-wideband emission covering 1200–2000 nm (NIR-II~III) is achieved. During preparation, BaCO3, La2O3, ZnO, WO3, and NiO are weighed according to stoichiometric ratios, and 5 mol% H3BO3 is added as a sintering aid. After grinding and mixing with alcohol and drying, the mixture is sintered at 1623 K for 4 hours in air and then naturally cooled to obtain the target phosphor. This phosphor can be mixed with PDMS at a weight ratio of 3:1 and cured at 353 K for 2 hours to form a flexible transparent film. This film is then coupled with a 330 nm ultraviolet continuous laser for excitation to produce NIR-III emission. The phosphor of this invention can be applied to night vision imaging, long-distance parking lot security monitoring, and anti-counterfeiting information encryption identification based on the absorption differences of different inks, possessing advantages such as wide emission spectrum, simple preparation process, and flexible application.

Description

Technical Field

[0001] This invention relates to the field of broadband near-infrared phosphor preparation and flexible light-emitting device technology, specifically to a NIR-II~III phosphor, its preparation method and application. Background Technology

[0002] NIR-III photons exhibit extremely low tissue absorption and scattering, and virtually no autofluorescence background in biological tissues, making them promising candidates for deep optical imaging. Currently, most near-infrared phosphors fail to cover the NIR-III region in terms of emission bandwidth, and their narrow half-width at half-maximum (HWHM) severely limits their application as broadband NIR-III light sources. 2+ While activated phosphors exhibit broadband emission characteristics, most emission only covers the NIR-II region, and very few materials can achieve NIR-III emission. Furthermore, existing Ni... 2+ Doped phosphors generally exhibit low internal quantum efficiency and poor thermal stability, making them unsuitable for practical applications such as high energy density, long-distance illumination, and bioimaging. Therefore, developing novel phosphors with broadband NIR-III emission, high quantum efficiency, and good thermal stability, and realizing their application in flexible, laser-driven light sources, is of significant scientific and practical value. This paper proposes a NIR-II~III phosphor, its preparation method, and its applications. Summary of the Invention

[0003] The present invention relates to the design of an NIR-II~III phosphor, its preparation method, and its application; the preparation method uses a high-temperature solid-state method to prepare Ni 2+ Doped Ba2La2ZnW2O 12 (BLZWO) broadband near-infrared phosphor; this phosphor is based on a hexagonal close-packed structure, Ni 2+ Occupying [ZnO6] octahedral sites, ultra-wideband emission covering NIR-II~III (1200–2000 nm) was achieved through crystal field modulation and impurity energy level design. In application, this phosphor was further embedded in a flexible PDMS film and coupled with a 330 nm ultraviolet laser to construct a laser-activated high-energy-density NIR-III light source; at this point, Ni… 2+ With O 2- The orbital hybridization in the octahedron generates impurity energy levels that participate in the radiative transition path, which is the main mechanism for ultra-wideband NIR-III emission; thus, this material shows application potential in night vision imaging, long-distance security monitoring, and anti-counterfeiting information encryption.

[0004] To achieve the above-mentioned technical effects, the present invention is implemented through the following technical solution: an NIR-II~III phosphor, characterized in that its chemical formula is: Ba2La2Zn1-x W2O 12 :xNi 2+ , where x = 0.3~3.0 mol.

[0005] Furthermore, x = 1.5 mol.

[0006] Furthermore, the NIR-II~III phosphors are based on a hexagonal close-packed structure, Ni 2+ Occupying [ZnO6] octahedral sites; through crystal field modulation and impurity level design, ultra-wideband emission covering NIR-II~III (1200–2000 nm) is achieved.

[0007] Another object of the present invention is to provide a method for preparing NIR-II~III phosphors, characterized by comprising the following steps:

[0008] S1. Raw material preparation: Weigh out BaCO3, La2O3, ZnO, WO3 and NiO in the ratio of BaCO3:La2O3:ZnO:WO3:NiO=2:1:1-x:2:x using a molar ratio meter, where x=0.3,0.5,0.7,1.0,1.5,2.0,3.0mol, and add 5mol H3BO3 as a sintering aid;

[0009] S2. Weigh the raw materials precisely according to the proportions and place them in an agate mortar. Add 10ml of alcohol and grind and mix.

[0010] S3. After the alcohol has completely evaporated and the powder is dry, transfer the powder to a covered corundum crucible and sinter it in air at 1600-1650K for 3-5 hours. After naturally cooling to room temperature, remove and grind to obtain Ba2La2Zn. 1-x W2O 12 :xNi 2+ Fluorescent powder.

[0011] Furthermore, in S3, the sintering temperature is 1623K and the holding time is 4 hours.

[0012] Furthermore, the purity of BaCO3, La2O3, ZnO, WO3, NiO, and H3BO3 is 99.99%.

[0013] Another objective of this invention is to provide an application of NIR-II~III phosphors in night vision imaging, long-distance (e.g., 10-meter-high) parking lot security monitoring, and anti-counterfeiting information encryption and identification based on the differences in NIR absorption of different inks.

[0014] Furthermore, the application specifically involves preparing Ba2La2Zn... 1-x W2O12 :xNi 2+ Phosphor and PDMS were uniformly mixed at a weight ratio and cured at 353K for 2 hours to prepare a flexible transparent NIR luminescent film. The film was then coupled with a 330nm ultraviolet continuous laser to excite the film to produce NIR-III emission.

[0015] Furthermore, the weight ratio of the phosphor to PDMS includes 0:1, 3:1, 2:1, 1:1, 1:2, 1:3, and 1:4.

[0016] Furthermore, the weight ratio of the phosphor to PDMS is 3:1.

[0017] The beneficial effects of this invention are:

[0018] Ba2La2Zn prepared by this invention 1-x W2O 12 :xNi 2+ The phosphor, when excited at 330 nm, exhibits an emission peak at 1530 nm, a full width at half maximum (FWHM) of approximately 300 nm, and covers the 1200–2000 nm range (NIR-II~III). Its internal quantum efficiency reaches 41.22%, outperforming most reported Ni... 2+ Activate NIR-II / III phosphors; wherein, Ni 2+ After occupying the [ZnO6] octahedron, lattice distortion occurs, and it interacts with O. 2- Orbital hybridization occurs, introducing an impurity level of approximately 1.31 eV into the band gap. This level participates in radiative transitions and is a key mechanism for ultra-wideband NIR-III emission. The phosphor has a thermal activation energy of 0.21 eV and maintains good emission at 453 K. The flexible film prepared by combining the phosphor with PDMS exhibits hydrophobicity (contact angle 106.42°), excellent tensile strength (elastic modulus 16.82 MPa), and outstanding stability.

[0019] The laser-activated NIR-III light source constructed in this invention demonstrates clear and distinguishable imaging effects in long-distance night vision imaging, large-area security monitoring, and anti-counterfeiting information encryption; through Ni 2+ Impurity level engineering and flexible laser device design in octahedrons provide new strategies for realizing efficient, high-energy-density, and long-life broadband NIR-III light sources. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 Ba2La2Zn prepared according to the present invention 1-x W2O 12 XRD patterns of -xNi (x=0,0.3,0.5,0.7,1.0,1.5,2.0,3.0) phosphors, and magnified views of local areas in the 29.0-29.5° range;

[0022] Figure 2 The present invention is Ba2La2Zn 1-x W2O 12 ESR spectrum of -1.5Ni phosphor at 100K;

[0023] Figure 3 The present invention is Ba2La2Zn 1-x W2O 12 PL and PLE spectra of BLZWO-1.5Ni phosphor;

[0024] Figure 4 The present invention is Ba2La2Zn 1-x W2O 12 Quantum efficiency curve (PLQY) of 1.5Ni phosphor;

[0025] Figure 5 Photographs of films prepared by different ratios of phosphor and PDMS according to the present invention under natural light;

[0026] Figure 6 The present invention is Ba2La2ZnW2O 12 :Ni 2+ SEM images and EDS elemental distribution maps of phosphor embedded in PDMS films;

[0027] Figure 7 Photographs showing the contact angles of the PDMS and phosphor / PDMS (3:1) film surfaces of this invention;

[0028] Figure 8 The stress-strain curves of blank PDMS and phosphor / PDMS (3:1) films of this invention are shown.

[0029] Figure 9 This invention demonstrates its potential applications in night vision imaging, far-field imaging, and information anti-counterfeiting under visible and NIR light. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] A NIR-II~III phosphor, its preparation method, and its application, specifically including the following steps:

[0033] Step 1: Preparation of Phosphor

[0034] (1) Raw material preparation: Weigh 2 mmol BaCO3 (purity 99.99%), 1 mmol La2O3 (purity 99.99%), 1-x mmol ZnO (purity 99.99%), 2 mmol WO3 (purity 99.99%), and x mmol NiO (purity 99.99%) in the molar ratio of BaCO3:La2O3:ZnO:WO3:NiO=2:1:1-x:2:x, where x=0.3,0.5,0.7,1.0,1.5,2.0,3.0 mol, and add 5 mol H3BO3 (purity 99.9%) as sintering aid;

[0035] (2) After accurately weighing the raw materials according to the proportion, place them in an agate mortar and add 10ml of alcohol to grind and mix thoroughly;

[0036] (3) After the alcohol has completely evaporated and the powder is dry, transfer the powder to a covered corundum crucible and sinter it in air at 1623 K for 4 hours. Then, allow it to cool naturally to room temperature, remove it, and grind it to obtain Ba2La2Zn. 1-x W2O 12 :xNi 2 + (x=0.3,0.5,0.7,1.0,1.5,2.0,3.0mol; preferably 1.5mol) NIR emitting fluorescent materials (denoted as NIR-II~III phosphors);

[0037] (4) Undoped Ni 2+ Ba2La2Zn 1-x W2O 12 (Refered as BLZWO) The host was prepared using the same steps as a control.

[0038] Step 2: Preparation of Flexible NIR Light-Emitting Thin Films

[0039] (1) The Ba2La2Zn obtained in step one is optimized 1-x W2O 12 -1.5Ni phosphor and PDMS organic polymer are uniformly mixed at a certain weight ratio, wherein the weight ratio includes 0:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4 (phosphor:PDMS), preferably 3:1;

[0040] (2) Place the mixture in a petri dish and cure it at 353K for 2 hours to obtain a flexible transparent NIR luminescent film.

[0041] Step 3: Construction of a laser-activated NIR-III light source

[0042] The flexible thin film prepared in step two is coupled with a 330nm ultraviolet continuous laser to excite the thin film to generate NIR-III emission.

[0043] In the phosphor material obtained through the above steps, Ni 2+ Ions replace Zn in the [ZnO6] octahedral sites of BLZW. 2+ ESR testing confirmed that Ni exists in the +2 valence state and is in an octahedral coordination environment; this material is obtained through Ni... 2+ With surrounding O 2- The orbital hybridization introduces an impurity level (approximately 1.31 eV) into the host bandgap. This impurity level participates in the radiative transition path and is a key mechanism for realizing ultra-wideband NIR-II to NIR-III emission.

[0044] Through systematic optimization, BLZWO-1.5Ni (i.e., Ni) 2+ The phosphor with a doping concentration of 1.5 mol exhibited the best performance: under 330 nm UV excitation, the emission peak was located at 1530 nm, the full width at half maximum (FWHM) was approximately 300 nm, and the emission range covered 1200–2000 nm (spanning the NIR-II and NIR-III regions), with an internal quantum efficiency of 41.22%. Thermal stability tests showed that the phosphor's thermal activation energy was 0.21 eV. In the prepared flexible film, the phosphor particles were uniformly distributed in the PDMS matrix (confirmed by SEM-EDS). The film exhibited hydrophobicity (contact angle 106.42°) and excellent tensile strength (elastic modulus 16.82 MPa), while the elastic modulus of the blank PDMS film was 1.13 MPa. The laser-activated NIR-III light source constructed by coupling the prepared optimized phosphor flexible film with a 330 nm UV continuous laser demonstrated clear application effects in night vision imaging, 10-meter high-altitude long-distance parking lot monitoring, and anti-counterfeiting information encryption identification.

[0045] Example 2

[0046] Figure 1XRD patterns of the prepared BLZWO-xNi (x=0, 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 3.0 mol%) phosphors, and magnified views within the 29.0–29.5° range; the diffraction peaks of all samples are basically consistent with the standard card (PDF#35-0128), indicating that pure-phase phosphors were successfully synthesized. 2+ Doping did not induce the formation of impurity phases; as can be seen from the magnified local image, with the increase of Ni... 2+ As the doping concentration increases, the diffraction peaks gradually shift slightly to higher angles; according to Bragg's law, this is due to the smaller radius of Ni. 2+ (0.69Å) replaced the larger-radius Zn 2+ (0.74Å), resulting in lattice contraction.

[0047] Figure 2 The image shows the ESR spectrum of BLZWO-1.5Ni phosphor at 100K; a characteristic signal appears at g=2.001, which is attributed to Ni in an octahedral coordination environment. 2+ Ions. The results show that Ni 2+ It successfully occupied an octahedral lattice site in the crystal lattice.

[0048] Figure 3 The PL and PLE spectra of BLZWO-1.5Ni phosphor are shown. When monitoring the emission peak at 1530 nm, the excitation spectrum exhibits a strong excitation band in the 300–350 nm range, which is attributed to Ni. 2+ of 3 A2(F)→ 3 T1(P) spin-allowed transitions; under 330 nm ultraviolet light excitation, the emission spectrum exhibits a broadband NIR emission covering 1200–2000 nm, with an emission peak at 1530 nm and a full width at half maximum (FWHM) of approximately 300 nm. This emission range spans from NIR-II to NIR-III regions.

[0049] Figure 4 The figure shows the quantum efficiency curve; under 330 nm excitation, the internal quantum efficiency (IQE) of the BLZWO-1.5Ni phosphor was measured to be 41.22%.

[0050] Figure 5 Photographs of films prepared with different phosphor-PDMS ratios under natural light; from left to right, the weight ratios of phosphor to PDMS are 0:1, 3:1, 2:1, 1:1, 1:2, 1:3, and 1:4; the blank PDMS film without added phosphor exhibits extremely high visible light transparency; as the phosphor content increases, the transparency of the film gradually decreases and eventually becomes opaque.

[0051] Figure 6SEM images and EDS elemental distribution maps of BLZWO-Ni phosphor embedded in PDMS films are shown. The SEM images show that the phosphor particles are uniformly distributed inside the PDMS film. The EDS elemental distribution maps show that Ba, La, Zn, W, and Ni elements are uniformly distributed in the film, ensuring the uniform luminescence performance of the flexible NIR luminescent film.

[0052] Figure 7 The images show the contact angles of the blank PDMS film and the phosphor / PDMS (3:1) film. The contact angle of the blank PDMS film is 115.26°, and the contact angle of the phosphor / PDMS (3:1) film is 106.42°. Both are greater than 90°, indicating that the film is hydrophobic and can be used underwater, in high humidity and smog environments.

[0053] Figure 8 The stress-strain curves are for blank PDMS and phosphor / PDMS (3:1) films. The tensile elastic modulus of the phosphor / PDMS (3:1) film is 16.82 MPa, which is much higher than that of the blank PDMS film (1.13 MPa), indicating that the addition of phosphor significantly enhances the film's resistance to deformation.

[0054] Figure 9 This demonstrates potential applications under visible and NIR light. (a) Night vision imaging: Kiwifruit, butterfly specimens, and knitted fabrics are photographed under visible light. When NIR light (700–1600 nm) is used as the sole light source, the NIR camera clearly displays the outlines and details of the objects, especially clearly distinguishing patterns in knitted fabrics with similar colors. (b) Far-field imaging: In a parking lot at night at a height of 10 meters, visible light images struggle to distinguish vehicles, while NIR images clearly differentiate vehicles within the parking lot, enabling large-scale, long-distance NIR security monitoring. (c) Information anti-counterfeiting: Utilizing the difference in absorption rates of different black inks in the NIR region, binary information is printed as black and white squares (white squares represent 0, black squares represent 1). Encrypted information is hidden under visible light, but can be successfully read under NIR light.

Claims

1. A NIR-II~III phosphor, characterized in that, Its chemical formula is: Ba2La2Zn 1-x W2O 12 :xNi 2+ , where x = 0.3~3.0 mol.

2. The NIR-II~III phosphor according to claim 1, characterized in that, The value of x is 1.5 mol.

3. The NIR-II~III phosphor according to claim 1, characterized in that, The NIR-II~III phosphors are based on a hexagonal close-packed structure, Ni 2+ Occupying [ZnO6] octahedral sites; through crystal field modulation and impurity level design, ultra-wideband emission covering NIR-II~III (1200–2000 nm) is achieved.

4. A method for preparing NIR-II~III phosphors according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Raw material preparation: Weigh out BaCO3, La2O3, ZnO, WO3 and NiO in the ratio of BaCO3:La2O3:ZnO:WO3:NiO=2:1:1-x:2:x using a molar ratio meter, where x=0.3,0.5,0.7,1.0,1.5,2.0,3.0mol, and add 5mol H3BO3 as a sintering aid; S2. Weigh the raw materials precisely according to the proportions and place them in an agate mortar. Add 10ml of alcohol and grind and mix. S3. After the alcohol has completely evaporated and the powder is dry, transfer the powder to a covered corundum crucible and sinter it in air at 1600-1650K for 3-5 hours. After naturally cooling to room temperature, remove and grind to obtain Ba2La2Zn. 1-x W2O 12 :xNi 2 + Fluorescent powder.

5. The method for preparing NIR-II~III phosphor according to claim 4, characterized in that, In S3, the sintering temperature is 1623K and the holding time is 4 hours.

6. The method for preparing NIR-II~III phosphor according to claim 4, characterized in that, The purity of BaCO3, La2O3, ZnO, WO3, NiO, and H3BO3 is 99.99%.

7. The application of the NIR-II~III phosphor according to claim 1 in night vision imaging, long-distance parking lot security monitoring, and anti-counterfeiting information encryption and identification based on the difference in NIR absorption of different inks.

8. The application according to claim 7, characterized in that, The application specifically involves preparing Ba2La2Zn. 1- x W2O 12 :xNi 2+ Phosphor and PDMS were uniformly mixed at a weight ratio and cured at 353K for 2 hours to prepare a flexible transparent NIR luminescent film. The film was then coupled with a 330nm ultraviolet continuous laser to excite the film to produce NIR-III emission.

9. The application according to claim 8, characterized in that, The weight ratio of the phosphor to PDMS includes 0:1, 3:1, 2:1, 1:1, 1:2, 1:3, and 1:

4.

10. The application according to claim 9, characterized in that, The weight ratio of the phosphor to PDMS is 3:1.

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