Cr < 3 + >-doped A2M3O12 type near-infrared first-region luminescent material and preparation method thereof

Abstract

The invention discloses a Cr < 3 + >-doped A2M3O12 type near-infrared first-region luminescent material and a preparation method thereof, and relates to the technical field of luminescent materials. According to the technical scheme, the structural formula is A1 (1-x) A2 (1-x) Cr2xM3O12, x is larger than or equal to 0.005 and smaller than or equal to 0.05, and A1 or A2 is one or more of Hf, Mg, Zr, Y and Sc; m is W or Mo. The preparation method comprises the following steps: S1, weighing corresponding raw materials according to the dosage ratio; s2, calcining the raw material powder prepared in the step S1; s3, cooling the calcined raw material powder to room temperature to obtain a calcined product; and S4, grinding the calcined product to prepare the Cr < 3 + > doped A2M3O12 type near-infrared luminescent material. The preparation method is simple, pollution-free and low in cost; the luminous intensity is high and the spectrum coverage range is large.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, specifically to a Cr... 3+ Doped A2M3O 12 Near-infrared luminescent materials in the first region and their preparation methods. Background Technology

[0002] In recent years, energy and environmental issues have become major topics affecting the sustainable development of human society. Light sources account for a large proportion of total energy consumption. LEDs (light emitting diodes) are a new generation of solid-state light sources. Compared with traditional incandescent lamps, fluorescent lamps, and gas discharge lamps, they have rapidly captured the market due to their advantages such as low energy consumption, long lifespan, and small size, showing great application prospects in lighting, display, sensing, and medical fields. In particular, with the introduction and development of mini-LED and micro-LED concepts and technologies, portable and miniaturized solid-state light sources will bring a new revolution to human life. As a result, some functional LEDs have gradually become research hotspots, with near-infrared LEDs being one such category.

[0003] Near-infrared light (700-1700nm) possesses advantages such as excellent penetration, tissue responsiveness, and strong anti-interference capabilities, and has gradually attracted widespread attention in fields such as bioimaging, biosensing, night vision monitoring, remote sensing, and spectroscopy. In particular, in recent years, non-destructive in vitro imaging and wearable biological sensors have shown broad application prospects in miniaturized, intelligent, and portable human-computer interaction experiences.

[0004] As research progressed, scientists discovered that Cr 3+ With its unique energy level structure, it can generate near-infrared broadband emission in a suitable crystal field. Its emission wavelength matches the bio-optical window, resulting in low tissue scattering and autofluorescence interference, and a high signal-to-noise ratio. It also boasts a broad excitation spectrum, making it easy to match with commercial chips. Furthermore, its excellent chemical and photothermal stability, low raw material cost, and good biocompatibility give it significant application potential in fields such as bioimaging, fluorescence sensing, in vivo diagnosis and treatment, near-infrared illumination, and security monitoring. It represents an important development direction for high-performance, low-cost near-infrared luminescent materials. In addition, in recent years, tungsten-molybdate luminescent materials based on negative thermal expansion properties have gradually come into the researchers' view. These materials overcome the thermal quenching phenomenon of traditional inorganic luminescent materials; as the temperature increases, the luminescence not only does not quench but also shows abnormal enhancement, demonstrating great application potential in temperature sensing and security anti-counterfeiting. In 2023, D. Stefa'nska et al. reported on Cr in the SAA journal. 3+ The structure and spectroscopic properties of the doped Sc2(MoO4)3 molybdate. This material emits at a wavelength of 880 nm and has a full width at half maximum (FWHM) of 176 nm (2179 cm⁻¹).-1 This technology achieves broadband near-infrared emission and, thanks to its rigid structure, exhibits excellent thermal stability, showing no significant luminescence quenching in the 80-300K temperature range. In 2024, Hongpeng You et al. reported on Cr in the journal *Advanced Optical Materials*. 3+ The structure and spectroscopic properties of doped LiScGaW2O8 tungstate. This material emits at a wavelength of 1069 nm and has a full width at half maximum (FWHM) of 225 nm. This is due to the presence of Cr... 3+ The crystal field strength around the luminescent center is very weak. 4 The energy of the T2 level is lower than 2 The E energy level makes Cr 3+ Its luminescence extends beyond the near-infrared I region into the near-infrared II region.

[0005] Therefore, based on the traditional advantages of LED light sources, high-efficiency Cr... 3+ Doped A2M3O 12 The development of tungsten-molybdate near-infrared LEDs is of great significance for promoting LED near-infrared light-emitting devices, expanding their emission spectrum, and broadening their application range. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a Cr 3+ Doped A2M3O 12 The near-infrared luminescent material and its preparation method are disclosed. The method involves one-step high-temperature calcination and emits bright near-infrared light after excitation with light of wavelengths of 250-750nm. The preparation method is simple, pollution-free, and low-cost. It also features high luminescence intensity and a wide spectral coverage. Light-emitting devices containing this phosphor can be applied in fields such as micro-spectral technology and biomedicine.

[0007] The technical solution of this invention is as follows:

[0008] On the one hand, the present invention provides a Cr 3+ Doped A2M3O 12 Type I near-infrared luminescent material, its structural formula is as follows A 1(1-x) A 2(1-x) Cr 2x M3O 12 Where 0.005≤x≤0.05, A1 or A2 is one or more of Hf, Mg, Zr, Y and Sc; M is W or Mo.

[0009] Preferably, the raw material for A1 or A2 is selected from one or more of hafnium oxide, magnesium oxide, zirconium oxide, yttrium oxide and scandium oxide.

[0010] Preferably, the raw material for M is selected from tungsten oxide or molybdenum oxide.

[0011] Preferably, Cr 3+ The raw material is selected from chromium oxide.

[0012] On the other hand, the present invention provides the above-mentioned Cr 3+ Doped A2M3O 12 A method for preparing near-infrared luminescent materials in the first region includes the following steps:

[0013] S1: According to A 1(1-x) A 2(1-x) Cr 2x M3O 12 Weigh the corresponding raw materials according to the stoichiometric ratio, grind each raw material to the micron level, and obtain powdered raw materials;

[0014] S2: Calcining the powdered raw material at 850-1100℃ for 6-10 hours in air or nitrogen atmosphere;

[0015] S3: Cool the calcined raw material powder to room temperature to obtain the calcined product;

[0016] S4: Grind the calcined material to obtain Cr. 3+ Doped A2M3O 12 Near-infrared luminescent material in the first region.

[0017] Preferably, in step S2, the air atmosphere is the atmospheric environment at room temperature of 25°C; the nitrogen atmosphere is a pure nitrogen environment in a closed environment with a nitrogen purity of 99.8%.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The near-infrared luminescent material synthesized by the method of the present invention is composed of (Hf, Mg, Zr, Y, Sc)(W, Mo)3O 12 Based on the structure, doped with Cr 3+ As the central ion, it is calcined at low temperature and, under light excitation at wavelengths of 250-750 nm, emits near-infrared light with wavelengths of 700-1400 nm. The peak value of this broadband near-infrared emission is located at 970 nm, in the near-infrared I region, and the full width at half maximum (FWHM) of the emission peak is 256 nm. A2M3O 12 The negative thermal expansion material has a rigid open framework formed by the co-oxygen connection of MO4 tetrahedra and AO6 octahedra, which is Cr 3+ Provides a stable lattice environment. Cr 3+ When doped, Cr 3+ Preferentially replacing high-coordination-number cations in the crystal lattice, Cr enters the distorted octahedral coordination field. At low doping concentrations, Cr... 3+ It exists in the form of a single ion, and its 3d3 Under the influence of a moderately strong crystal field, the ground state of an electron is 4 A2, the excited state is 4 T1, 4 T2. Under ultraviolet or blue light excitation, electrons transition from the ground state... 4 A2 transitions to the excited state. 4 T1 or 4 T2, after rapid non-radiative relaxation, with spin-allowed... 4 T2→ 4 The A2 transition returns to the ground state, generating broadband emission in the near-infrared region I. This is the Cr... 3+ Doped A2M3O 12 The intrinsic mechanism of luminescence in near-infrared luminescent materials.

[0020] 2. The preparation method of this invention adopts one-step high-temperature calcination, and after excitation with light of wavelength 250-750 nm, it can emit bright near-infrared light-emitting material. It has the advantages of simple preparation method, no pollution, low cost, high luminous intensity, and wide spectral coverage. The light-emitting device containing this phosphor can be applied to micro-spectral technology, biomedicine and other fields. Attached Figure Description

[0021] Figure 1 This is a comparison of the XRD pattern of the near-infrared luminescent material prepared in Example 1 with the standard XRD pattern of the target product.

[0022] Figure 2 This is the excitation and emission spectrum of the near-infrared luminescent material prepared in Example 1.

[0023] Figure 3 This is a comparison of the XRD pattern of the near-infrared luminescent material prepared in Comparative Example 1 with the standard XRD pattern of the target product.

[0024] Figure 4 This is the excitation and emission spectrum of the near-infrared luminescent material prepared in Comparative Example 1.

[0025] Figure 5 This is a comparison between the XRD pattern of the near-infrared luminescent material prepared in Example 2 and the standard XRD pattern of the target product.

[0026] Figure 6 This is the excitation and emission spectrum of the near-infrared luminescent material prepared in Example 2.

[0027] Figure 7 This is a comparison of the XRD pattern of the near-infrared luminescent material prepared in Comparative Example 2 with the standard XRD pattern of the target product.

[0028] Figure 8 This is the excitation and emission spectrum of the near-infrared luminescent material prepared in Comparative Example 2.

[0029] Figure 9 This is a comparison of the XRD pattern of the near-infrared luminescent material prepared in Comparative Example 3 with the standard XRD pattern of the target product.

[0030] Figure 10 This is the excitation and emission spectrum of the near-infrared luminescent material prepared in Comparative Example 3. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention.

[0032] Example 1 Hf 0.97 Mg 0.97 Cr 0.06 W3O 12 Preparation and performance characterization

[0033] 0.2042g HfO2, 0.0391g MgO, 0.6955g WO3, and 0.0046g Cr2O3 were weighed as raw materials. The raw materials were ground and mixed evenly, then placed in an alumina crucible and calcined at 1100℃ in air for 6 hours. The calcined powder was then cooled to room temperature with the furnace to obtain the calcined product. The calcined product was then ground to obtain the near-infrared luminescent material Hf. 0.97 Mg 0.97 Cr 0.06 W3O 12 .

[0034] Figure 1 The XRD pattern of this near-infrared luminescent material indicates that its phase is HfMgW3O. 12 No other impurity phases were generated. This near-infrared luminescent material Hf 0.97 Mg 0.97 Cr 0.06 W3O 12 The excitation and emission spectra are as follows Figure 2 As shown in the figure, the near-infrared luminescent material HfMgW3O is displayed. 12 The emission spectrum is broadband, with a peak value around 886 nm and a full width at half maximum (FWHM) of 253 nm. Its excitation spectrum is also broadband, with the optimal excitation wavelength around 480 nm. This near-infrared luminescent material Hf... 0.97 Mg 0.97 Cr 0.06 W3O 12 Exhibiting a Stokes shift of 406 nm, and effectively suppressing self-absorption while ensuring efficient blue light excitation, it can be concluded that the prepared luminescent material is a blue light-excited near-infrared luminescent material.

[0035] Comparative Example 1 Hf 0.99 Mg 0.99 Cr 0.02 Mo3O 12 Preparation and luminescence characterization

[0036] Unlike Example 1, Comparative Example 1 used 0.2084g HfO2, 0.0399g MgO, 0.4318g MoO3, and 0.0015g Cr2O3 as raw materials, and the calcination temperature was 850℃. All other synthesis conditions were the same as in Example 1.

[0037] according to Figure 3 It can be seen that the phase of this near-infrared luminescent material is HfMgMo3O 12 No other impurity phases were generated. And according to... Figure 4 As shown in the emission spectrum, Comparative Example 1 (Hf) 0.99 Mg 0.99 Cr 0.02 Mo3O 12 The luminescence intensity of ) is compared to that of Example 1 (Hf) 0.97 Mg 0.97 Cr 0.06 W3O 12 ) is very weak, mainly due to W 6+ and Mo 6+ Differences between the two ions in electronic structure, chemical bond properties, and lattice environment: W 6+ Higher electronegativity and polarizability allow CrO6 octahedrons to possess a more suitable crystal field strength, which is beneficial to Cr 3+ of 4 T2→ 4 A2 transition emits light; while Mo... 6+ The introduction of Mo alters the crystal field environment, shifting the excited-state energy level distribution and significantly enhancing non-radiative relaxation channels. Simultaneously, the higher phonon energy of the Mo-O bond exacerbates the multiphonon relaxation process, causing more excited-state energy to dissipate as heat. Furthermore, the charge transfer band of the Mo-based matrix becomes less matched to the excitation wavelength, leading to matrix-Cr... 3+ The decreased energy transfer efficiency, coupled with the increase in lattice stress and defects, leads to a reduction in fluorescence quantum yield, ultimately resulting in a significant weakening of luminescence performance.

[0038] Example 2 Zr 0.99 Mg 0.99 Cr 0.02 W3O 12 Preparation and performance characterization

[0039] 0.122g ZrO2, 0.0399g MgO, 0.6955g WO3, and 0.0015g Cr2O3 were weighed as raw materials. The raw materials were ground and mixed evenly, then placed in an alumina crucible and calcined in air at 1050℃ for 6 hours. The calcined powder was cooled to room temperature with the furnace to obtain the calcined product. The calcined product was then ground to obtain the near-infrared luminescent material ZrO2. 0.99 Mg 0.99 Cr 0.02 W3O 12 .

[0040] like Figure 5 As shown, in Zr 4+ and Mg 2+ Each lattice site is doped with 1% Cr 3+ The positions of all strong peaks in the XRD of the subsequent sample were consistent with those of the standard XRD data. This indicates that Cr 3+ Successfully entered Zr 4+ and Mg 2+ No impurity phase was generated at the lattice sites. Its excitation and emission spectra are as follows: Figure 6 As shown, compared to Hf in Example 1 0.97 Mg 0.97 Cr 0.06 W3O 12 Excitation and emission spectra of Zr 0.99 Mg 0.99 Cr 0.02 W3O 12 The sample exhibits an increased Stokes shift (~450 nm), indicating a weaker matrix crystal field. 4 The decrease in the T2 energy level reduces the transition energy difference, resulting in a significant redshift in both the excitation and emission spectra. The main excitation peak shifts to around 520 nm, reflecting... 4 A2→ 4 The T1 transition absorption band shifts to a longer wavelength; the emission peak position redshifts to 970 nm, while still maintaining broadband emission characteristics, further extending to the long wavelength end of the near-infrared I region and extending to the near-infrared II region, indicating that the prepared material is a near-infrared luminescent material.

[0041] Comparative Example 2 Zr 0.99 Mg 0.99 Cr 0.02 Mo3O 12 Preparation and performance characterization

[0042] Unlike Example 2, Comparative Example 2 used 0.122g ZrO2, 0.0399g MgO, 0.4318g MoO3, and 0.0015g Cr2O3 as raw materials. These raw materials were ground and mixed evenly, then placed in an alumina crucible and calcined in air at 850°C for 6 hours. The calcined powder was then cooled to room temperature with the furnace to obtain the calcined product. The calcined product was then ground to obtain the near-infrared luminescent material ZrO2. 0.99 Mg 0.99 Cr 0.02 Mo3O 12 .

[0043] from Figure 7 From this, we can see that W 6+ Replace with Mo 6+ Subsequently, the XRD diffraction peaks of the sample were basically consistent with the standard XRD data, indicating that no impurity phase was generated, and the crystal structure remained intact and pure. Its excitation and emission spectra are as follows: Figure 8 As shown, Zr 0.99 Mg 0.99 Cr 0.02 Mo3O 12 The sample had an emission peak at 920 nm and a Stokes shift of 408 nm, but its luminescence intensity was significantly lower than that of Zr in Example 2. 0.99 Mg 0.99 Cr 0.02 W3O 12 Furthermore, the emission peak shape exhibits significant fluctuations. The reason for this is similar to that of the reduced luminescence intensity in Comparative Example 1. Meanwhile, Mo... 6+ The ionic radius is slightly larger than W. 6+ Doping introduces more lattice stress and defects, forming non-radiative recombination centers, which further weakens the luminescence intensity and causes peak perturbation.

[0044] Comparative Example 3 Y 1.98 Cr 0.02 W3O 12 Preparation and performance characterization

[0045] 0.2236g Y₂O₃, 0.6955g WO₃, and 0.0015g Cr₂O₃ were weighed as raw materials. The raw materials were ground and mixed evenly, then placed in an alumina crucible and calcined at 1100℃ in air for 6 hours. The calcined powder was cooled to room temperature with the furnace to obtain the calcined product. The calcined product was then ground to obtain the near-infrared luminescent material Y₂O₃. 1.98 Cr 0.02 W3O 12 .

[0046] from Figure 9 From this, we can see that in Y3+ 1% Cr doped at lattice sites 3+ Subsequently, the XRD diffraction peaks of the sample were consistent with the standard XRD data, indicating that Cr 3+ Successfully entered Y 3+ The lattice positions did not induce the formation of impurity phases, and the crystal structure remained intact and pure. From Figure 10 From the spectral characteristics, it can be seen that Y 1.98 Cr 0.02 W3O 12 It exhibits broadband near-infrared emission of 890 nm under 480 nm excitation, with a Stokes shift of approximately 410 nm, similar to Hf in Example 1. 0.97 Mg 0.97 Cr 0.06 W3O 12 The emission peak positions are basically the same, indicating that both have Cr. 3+ The transition energy differences are similar. However, its excitation spectrum shows a sharp and strong peak at ~650 nm, originating from the Y at the A site. 3+ This leads to increased octahedral distortion in CrO6. 4 A2→ 4 The T2(G) transition absorption is significantly enhanced, broadening the excitation window. However, lattice defects introduced by isovalent substitution cause peak fluctuations, leading to a decrease in luminescence efficiency.

[0047] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. Cr 3+ Doped A2M3O 12 Type I near-infrared luminescent material, characterized in that, Its structural formula is A 1(1-x) A 2(1-x) Cr 2x M3O 12 Where 0.005≤x≤0.05, A1 or A2 is one or more of Hf, Mg, Zr, Y and Sc; M is W or Mo.

2. The Cr as described in claim 1 3+ Doped A2M3O 12 Type I near-infrared luminescent material, characterized in that, The raw materials for A1 or A2 are selected from one or more of hafnium oxide, magnesium oxide, zirconium oxide, yttrium oxide, and scandium oxide.

3. The Cr as described in claim 1 3+ Doped A2M3O 12 Type I near-infrared luminescent material, characterized in that, The raw material for M is selected from tungsten oxide or molybdenum oxide.

4. The Cr as described in claim 1 3+ Doped A2M3O 12 Type I near-infrared luminescent material, characterized in that, Cr 3+ The raw material is selected from chromium oxide.

5. The Cr as described in any one of claims 1-4 3+ Doped A2M3O 12 The method for preparing near-infrared luminescent materials in the first region is characterized by, Includes the following steps: S1: According to A 1(1-x) A 2(1-x) Cr 2x M3O 12 Weigh the corresponding raw materials according to the stoichiometric ratio, grind each raw material to the micron level, and obtain powdered raw materials; S2: Calcining the powdered raw material at 850-1100℃ for 6-10 hours in air or nitrogen atmosphere; S3: Cool the calcined raw material powder to room temperature to obtain the calcined product; S4: Grind the calcined material to obtain Cr. 3+ Doped A2M3O 12 Near-infrared luminescent material in the first region.

6. The Cr as described in claim 5 3+ Doped A2M3O 12 The method for preparing near-infrared luminescent materials in the first region is characterized by, In step S2, the air atmosphere is the atmospheric environment at room temperature of 25°C; the nitrogen atmosphere is a pure nitrogen environment in a closed environment with a nitrogen purity of 99.8%.

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