Preparation method and application of Fe < 3 + >-activated broadband sulfide near-infrared fluorescent powder for optical imaging

Abstract

The invention aims to provide Fe < 3 + > activated sulfide near-infrared fluorescent powder for optical imaging as well as a preparation method and application thereof, and belongs to the technical field of inorganic luminescent materials. The chemical composition formula of the near-infrared fluorescent powder is LiGa < 0.99 > S < 2 >: 0.01 Fe < 3 + >. A vulcanization strategy is adopted, synthesis is performed through a high-temperature solid-phase method, and calcination is performed in an inert atmosphere to obtain a target product. The fluorescent powder has broadband near-infrared emission (the peak wavelength is 1400nm, and the full width at half maximum reaches 285 nm), can be effectively excited by a commercial 450nm blue light LED chip, and has excellent luminescence performance, water stability and acid resistance. And the emission spectrum covers the NIR-II region, and is suitable for night vision, non-destructive biological detection and liquid component analysis. The preparation method has the advantages of simple process, low cost and batch synthesis, and provides a new way for the design and application of high-performance near-infrared luminescent materials.

Description

Technical Field

[0001] This invention belongs to the field of inorganic luminescent materials technology, specifically relating to a Fe for optical imaging. 3+ Preparation method and application of activated broadband sulfide near-infrared phosphor. Background Technology

[0002] Near-infrared light has important applications in optical communication, non-invasive biomedical imaging, and targeted therapy. Traditional high-energy-consuming halogen tungsten lamps and narrow-spectrum near-infrared LEDs are gradually being replaced by high-efficiency, environmentally friendly near-infrared phosphor-converted LEDs (pc-LEDs). These devices offer advantages such as compact structure, fast response, and tunable emission spectra. However, because the dd transition of transition metal ions is a forbidden transition, its charge transfer band is typically located in the high-energy ultraviolet region, thus near-infrared phosphors have long been limited to ultraviolet or near-ultraviolet excitation. In recent years, Cr... 3+ Activated near-infrared phosphors have been extensively studied, and they can be used in weak crystal fields through spin-allowed... 4 A 2g → 4 T 1g The transition produces a broadband emission of 650-1200 nm. However, most Cr 3+ Cr present in the doped system 6+ The severe suppression of luminescence efficiency limits its long-term application in living organisms. Ni 2+ Although doped materials can emit in the NIR-II region, their efficiency is low and their absorption is weak. Other examples include Eu... 2+ Bi 3+ Mn 2+ Plasma emission is mainly concentrated in the far-infrared to NIR-I region, where tissue scattering is severe, limiting its penetration depth in biological systems.

[0003] Because biological tissues exhibit varying absorption and reflection rates of near-infrared light across different wavelengths (NIR-I: 700-1000 nm; NIR-II: 1000-1700 nm), the development of customizable, broadband-tunable near-infrared phosphors has become a research hotspot. (The last sentence appears to be incomplete and unrelated to the preceding text. It likely refers to Ce.) 3+ / Eu 2+ The fd transitions are different, Fe 3+ The luminescence of ions originates from dd transitions and is less affected by electron cloud expansion. To achieve a spectral redshift, researchers have developed strategies such as energy transfer engineering, coordination engineering, and lattice site engineering. For example, co-doping can achieve emission from visible light to NIR-I, but the energy transfer process involves significant energy loss. Typically, tetrahedral coordinated Fe... 3+ Emission occurs in the 650-780 nm range, while octahedral coordination enables near-infrared emission at even longer wavelengths; the difference stems from variations in crystal field strength. However, in some spinel systems, Fe...3+ Even when occupying octahedral sites, emission remains below 780 nm. Recent studies have shown that co-substitution can achieve a redshift from 885 nm to 1005 nm, but significant redshifts and band broadening in the NIR-II region remain difficult to achieve. Current research largely relies on Tanabe-Sugano level diagrams to analyze crystal field intensity, but limitations include the lack of a unified calculation formula, unclear definitions of excited-state energy levels, complex energy level structures, diverse coordination environments, and numerous ion species, making it impossible to fully predict emission spectrum positions from excitation spectra. Therefore, developing novel near-infrared phosphors compatible with blue LEDs is a crucial issue for phosphor-converting LED luminescent materials, and the development of related luminescent materials and devices is of great significance to the advancement of optical imaging. Summary of the Invention

[0004] The purpose of this invention is to provide a Fe for optical imaging. 3+ A method for preparing and applying activated broadband sulfide near-infrared phosphors is disclosed. The preparation method is simple, convenient, and environmentally friendly. The phosphors are characterized by being excited by blue light, emitting in the broadband near-infrared II region, and exhibiting excellent chemical stability.

[0005] The present invention adopts the following technical solution: Fe for optical imaging 3+ Activated broadband sulfide near-infrared phosphor, its chemical composition is LiGa 0.99 S2:0.01Fe 3+ The near-infrared phosphor has an emission peak of 1400 nm and a full width at half maximum (FWHM) of 285 nm.

[0006] Fe for optical imaging 3+ A method for preparing activated broadband sulfide near-infrared phosphors includes the following steps: S1. Weigh the raw materials according to the stoichiometric ratio under an inert atmosphere, and introduce CS2 to grind them thoroughly to obtain a mixture of raw materials. S2. Place the raw material mixture obtained in S1 in a corrosion-resistant container and calcine it at 780-820℃ for 3-5 hours under a flowing N2 atmosphere carrying CS2 vapor to obtain a sintered body. S3. The sintered body obtained in S2 is naturally cooled to room temperature, and then ground to obtain the near-infrared phosphor.

[0007] Furthermore, the raw materials mentioned in S1 include Li2S, Ga2S3, FeS2 or Li2SO4, Ga2O3, Fe2O3.

[0008] Furthermore, the inert atmosphere described in S1 is an argon atmosphere.

[0009] Furthermore, the anti-corrosion treatment method described in S2 involves wrapping the container with carbon paper and performing carbonization treatment.

[0010] Furthermore, the calcination temperature in S2 is 800℃, and the calcination time is 4h.

[0011] Fe for optical imaging 3+ Application of activated broadband sulfide near-infrared phosphors in the fabrication of fluorescence-converting LED devices.

[0012] Furthermore, the fluorescent conversion LED device includes a packaging substrate, a blue LED chip, and a near-infrared phosphor layer; the near-infrared phosphor can absorb the light emitted by the blue LED chip and generate near-infrared light emission.

[0013] Furthermore, the blue LED chip is a GaN-based blue LED chip with an emission wavelength range of 440-450nm.

[0014] Fe for optical imaging 3+ Applications of activated sulfide near-infrared phosphors in non-destructive testing, bioimaging, or liquid composition analysis.

[0015] The principle of this invention is as follows: This invention utilizes an anion substitution engineering strategy to achieve the desired effect in LiGa. 0.99 S2:0.01Fe 3+ Highly efficient broadband near-infrared II (NIR-II) emission for optical imaging was achieved in near-infrared phosphors, suitable for non-destructive testing and liquid composition analysis. The enhanced covalent interaction between the luminescent center and the coordinating anion after anion substitution was elucidated using ligand field theory. Through enhanced Fe-S covalent bonding, this material achieved an unprecedented 1400 nm emission under 470 nm excitation. 3+ The ions simultaneously occupy both LiS4 and GaS4 tetrahedra. The near-perfect energy between the S-3p and Fe-3d orbitals significantly enhances the Fe-S covalent interaction, effectively reducing electron repulsion within the 3d orbitals and lowering the antibonding state energy, thereby inducing an overall downward shift in the excited state energy level. This material also exhibits excellent water stability and acid resistance, and its phosphor-converted LEDs integrated with commercial blue GaN chips show broad application prospects in night vision, biomedicine, and liquid composition detection.

[0016] The beneficial effects of this invention are as follows: 1. The near-infrared phosphor of the present invention has an unprecedented emission peak of 1400nm and a full width at half maximum (FWHM) of 285nm, achieving a breakthrough redshift from the NIR-I to NIR-II region, and can be effectively excited by commercial 450nm blue LED chips.

[0017] 2. The preparation method of the present invention adopts a high-temperature solid-state method, which is simple, low-cost, environmentally friendly, and suitable for large-scale production.

[0018] By enhancing the Fe-S covalent interaction, the repulsion between electrons in the 3d orbital was effectively reduced, and the overall energy level of the excited state was shifted downward, providing new theoretical guidance for solving broadband near-infrared emission.

[0019] 3. The phosphor of the present invention exhibits excellent chemical stability, and can still maintain 95% of its initial luminescence intensity after being soaked in water and acidic environments for 30 days, meeting the needs of practical applications.

[0020] PC-LED devices based on this phosphor show broad application prospects in fields such as night vision, non-destructive biological detection, and liquid composition analysis. Attached Figure Description

[0021] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the fluorescent material powder prepared in Example 1.

[0022] Figure 2 The fluorescent material LiGa prepared in Example 1 0.99 S2:0.01Fe 3+ The excitation and emission spectra.

[0023] Figure 3 This is a schematic diagram and spectrum of the near-infrared LED light-emitting device fabricated in Example 4.

[0024] Figure 4 The conversion efficiency and output power of the near-infrared LED light-emitting device fabricated in Example 4 are shown.

[0025] Figure 5 The spectrum of Example 1 is the specific spectrum required for liquid absorption.

[0026] Figure 6 The images show photographs taken with a near-infrared camera and photographs taken with a visible camera under sunlight of the near-infrared LED fabricated in Example 4. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, specific embodiments of the invention are described in detail, but are not limited thereto. Unless otherwise specified, the raw materials used in the embodiments are all commercially available products; and unless otherwise specified, the methods used are methods commonly used in the art.

[0028] Fe for optical imaging 3+ The preparation method of activated sulfide near-infrared phosphor includes the following steps: S1, according to the chemical formula LiGa0.99 S2:0.01Fe 3+ The raw materials were accurately weighed under an inert atmosphere and mixed thoroughly with CS2 to obtain a raw material mixture. S2. Place the raw material mixture obtained in S1 in a corrosion-resistant container and calcine it at 780-820℃ for 3-5 hours under a flowing N2 atmosphere carrying CS2 vapor to obtain a sintered body. S3. The sintered body obtained in S2 is naturally cooled to room temperature, and then ground to obtain the near-infrared phosphor.

[0029] Example 1 Fe in this embodiment 3+ The chemical formula of the activated sulfide near-infrared phosphor is LiGa 0.99 S2:0.01Fe 3+ According to the stoichiometric ratio of Li:Ga:Fe = 1:0.99:0.01, 0.09189 g of Li₂S (Maclean, 99.9%), 0.46656 g of Ga₂S₃ (Maclean, 99.99%), and 0.00395 g of FeS₂ (Maclean, 99.99%) were accurately weighed in an argon-atmosphere glove box, and CS₂ (Aladdin, 99.9%) was introduced. The raw material mixture was ground in an agate mortar for 20 minutes to ensure thorough mixing, and then transferred to a crucible wrapped with carbon paper. It was sintered at 800°C for 4 hours under a nitrogen flow (carrying CS₂ vapor). After naturally cooling to room temperature, it was ground again to obtain LiGaS₂:Fe. 3+ Near-infrared phosphor.

[0030] Example 2 Fe in this embodiment 3+ The chemical formula of the activated sulfide near-infrared phosphor is LiGa 0.99 S2:0.01Fe 3+ The preparation method is the same as in Example 1, except that the sintering temperature is 780℃ and the sintering time is 5 hours. Other raw material ratios and processing conditions are consistent with those in Example 1.

[0031] Example 3 Fe in this embodiment 3+ The chemical formula of the activated sulfide near-infrared phosphor is LiGa 0.99 S2:0.01Fe 3+The preparation method is the same as in Example 1, except that the raw materials are Li2SO4 = 0.21989g (Maclean, 99.9%), Ga2O3 = 0.37513g (Maclean, 99.99%), and Fe2O3 = 0.00319g (Maclean, 99.99%). Other proportions and processing conditions are the same as in Example 1.

[0032] Example 4 A method for fabricating a near-infrared PC-LED device includes the following steps: preparing LiGa42O4 as described in Example 1... 0.99 S2:0.01Fe 3+ Near-infrared phosphor and epoxy resin are uniformly mixed and stirred to obtain a phosphor-resin mixture; the mixture is uniformly coated on the surface of a commercial GaN blue light chip (emission wavelength 450 nm); the chip is cured in an 80°C oven for 20 minutes to complete the device encapsulation; after connecting the circuit, a pc-LED device emitting 1400nm near-infrared light is obtained.

[0033] Example 5 Chemical stability test experiment: LiGa prepared in Example 1 was used. 0.99 S2:0.01Fe 3+ 0.5 g of each phosphor sample was dispensed into three PVC sample vials; the initial luminescence intensity (I0) was measured for each vial; equal volumes of deionized water, H2SO4 solution, and NaOH solution were added to each of the three vials; the samples were removed after 1, 3, 7, 14, 21, and 30 days, dried, and the luminescence intensity (I0) was measured. t ); calculate relative luminous intensity (I) t ( / I0×100%), the results showed that after 30 days, the sample still maintained more than 95% of the initial luminescence intensity in water and acid.

[0034] Figure 1 This is the X-ray diffraction (XRD) pattern of the fluorescent material powder prepared in Example 1. Figure 1 It can be seen that the sample corresponds to the diffraction peaks as shown by comparison with the standard card, and the target product was successfully synthesized.

[0035] Figure 2 The fluorescent material LiGa prepared in Example 1 0.99 S2:0.01Fe 3+ The excitation and emission spectra are derived from Figure 2 It can be seen that a broadband near-infrared phosphor with a full width at half maximum (FWHM) of 285 nm and a peak value of 1400 nm was obtained under 470 nm excitation.

[0036] Figure 3 The spectrum of the near-infrared LED light-emitting device produced in Example 4 is shown below. Figure 3It can be seen that there is no obvious attenuation phenomenon as the driving current increases, indicating that the device has good stability.

[0037] Figure 4 The conversion efficiency and output power of the near-infrared LED light-emitting device fabricated in Example 4 are given. Figure 4 It can be seen that as the driving current increases, the conversion efficiency remains stable, while the output power shows an increasing trend, indicating that the device can still maintain a high output as the driving current increases.

[0038] Figure 5 The absorption spectra of Example 1 and the standard liquid are obtained from... Figure 5 It can be seen that the spectrum highly overlaps with the absorption spectrum of the standard liquid, indicating that the material can effectively detect liquid components.

[0039] Figure 6 The images show photographs taken with a near-infrared camera and a visible camera under daylight of the near-infrared LED fabricated in Example 4. The results demonstrate significant application potential in night vision and penetration.

[0040] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be defined by the appended claims.

Claims

1. A Fe for optical imaging 3+ Activated broadband sulfide near-infrared phosphor, characterized in that: The near-infrared phosphor has the chemical composition of LiGa. 0.99 S2:0.01Fe 3+ The near-infrared phosphor has an emission peak of 1400 nm and a full width at half maximum (FWHM) of 285 nm.

2. A Fe for optical imaging as described in claim 1 3+ A method for preparing activated broadband sulfide near-infrared phosphors, characterized in that: Includes the following steps: S1. Weigh the raw materials according to the stoichiometric ratio under an inert atmosphere, and introduce CS2 to grind them thoroughly to obtain a mixture of raw materials. S2. Place the raw material mixture obtained in S1 in a corrosion-resistant container and calcine it at 780-820℃ for 3-5 hours under a flowing N2 atmosphere carrying CS2 vapor to obtain a sintered body. S3. The sintered body obtained in S2 is naturally cooled to room temperature, and then ground to obtain the near-infrared phosphor.

3. The Fe for optical imaging according to claim 2 3+ A method for preparing activated broadband sulfide near-infrared phosphors, characterized in that: The raw materials mentioned in S1 include Li2S, Ga2S3, FeS2 or Li2SO4, Ga2O3, Fe2O3.

4. The Fe for optical imaging according to claim 2 3+ A method for preparing activated broadband sulfide near-infrared phosphors, characterized in that: The inert atmosphere mentioned in S1 is an argon atmosphere.

5. The Fe for optical imaging according to claim 2 3+ A method for preparing activated broadband sulfide near-infrared phosphors, characterized in that: The anti-corrosion treatment method described in S2 is to wrap the container with carbon paper and perform carbonization treatment.

6. The Fe for optical imaging according to claim 2 3+ A method for preparing activated broadband sulfide near-infrared phosphors, characterized in that: The calcination temperature described in S2 is 800℃, and the calcination time is 4h.

7. A Fe for optical imaging as described in claim 1 3+ Application of activated broadband sulfide near-infrared phosphors in the fabrication of fluorescence-converting LED devices.

8. The Fe for optical imaging according to claim 7 3+ The application of activated broadband sulfide near-infrared phosphors is characterized by: The fluorescent conversion LED device includes a packaging substrate, a blue LED chip, and a near-infrared phosphor layer; the near-infrared phosphor can absorb the light emitted by the blue LED chip and generate near-infrared light emission.

9. The Fe for optical imaging according to claim 8 3+ The application of activated broadband sulfide near-infrared phosphors is characterized by: The blue LED chip is a GaN-based blue LED chip with an emission wavelength range of 440-450nm.

10. A Fe for optical imaging as described in claim 1 3+ Applications of activated sulfide near-infrared phosphors in non-destructive testing, bioimaging, or liquid composition analysis.

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