Rare earth organic-inorganic hybrid luminescent material and preparation method thereof

Abstract

The application discloses a rare earth organic-inorganic hybrid luminescent material, which has a chemical formula of [(CH3CH2)4N]Eu[CH2(SO3)2]2, wherein Eu 3+ is a metal site, [CH2(SO3)2] 2‑ and Eu 3+ are chelated and coordinated to form a one-dimensional anion framework, and guest cation CH3CH2)4 + is distributed in a crystal lattice to form a host-guest compound. The preparation method comprises the following steps: (1) mixing an organic amine source (CH3CH2)4N + , an europium source and a methyldisulfonic acid source, and dissolving the mixture in water to obtain a mixed solution; (2) adjusting the pH of the mixed solution prepared in the step (1) to be acidic, and then performing constant-temperature heating and volatilization, so that colorless transparent crystals are precipitated, and the colorless transparent crystals are the final product. The rare earth organic-inorganic hybrid luminescent material has high-efficiency blue light excitation and super-high thermal stability, and has good fluorescence performance.

Description

Technical Field

[0001] This invention relates to a luminescent material and its preparation method, and particularly to a rare earth organic-inorganic hybrid luminescent material and its preparation method. Background Technology

[0002] Light-emitting diodes (LEDs) are gradually replacing traditional incandescent and fluorescent lamps due to their advantages such as low energy consumption, environmental friendliness, and long lifespan. Currently, commercially available white LEDs mainly use a combination of yellow phosphors and blue LED chips in their packaging. However, this combination lacks red light, resulting in a low color rendering index and a high correlated color temperature, giving it a cool visual tone, which is not conducive to healthy lighting. Therefore, developing red phosphors that can be excited by blue light, are low-cost, environmentally friendly, and have high luminous efficiency is of great practical significance for achieving green and healthy lighting.

[0003] Currently, the red phosphors used in the market are mainly inorganic Y2O3:Eu 3+ and Y2O2S:Eu 3+ However, their poor chemical stability, low absorption efficiency, and excitation in the deep ultraviolet region limit their suitability for blue LED chips. Furthermore, the production of pure inorganic phosphors requires high-temperature synthesis, resulting in high energy consumption and high costs, which is detrimental to green and healthy development. Over the past decade, organic-inorganic hybrid materials have made significant progress in photovoltaic applications as an emerging semiconductor material, thanks to their advantages such as light weight, simple synthesis, environmental friendliness, and strong structural manipulation. Meanwhile, the high carrier mobility and abundant quantum wells of organic-inorganic hybrid structures have also attracted considerable attention in the design of novel luminescent materials. Rare earth metals possess rich energy level structures and transition types, producing a wide range of fluorescence spectra from ultraviolet to near-infrared wavelengths. Using them as organic-inorganic hybrid metal sites can endow compounds with excellent optical properties. However, current research on rare earth metal-based organic-inorganic hybrid luminescent materials is limited, and the presence of organic components generally results in poor optical and thermal stability of rare earth hybrid compounds. Furthermore, most hybrid compounds exhibit low quantum yields and cannot be effectively excited by near-ultraviolet or blue light. These characteristics significantly limit the further development of rare-earth hybrid luminescent materials. Therefore, developing novel rare-earth organic-inorganic hybrid fluorescent materials with excellent thermal stability, high quantum efficiency, and good spectral quality that can be excited by blue or near-ultraviolet light holds significant application potential. Summary of the Invention

[0004] Purpose of the invention: The first purpose of this invention is to provide a rare earth organic-inorganic hybrid luminescent material with high efficiency of blue light excitation and ultra-high thermal stability; the second purpose of this invention is to provide a method for preparing the rare earth organic-inorganic hybrid luminescent material.

[0005] Technical solution: The rare-earth organic-inorganic hybrid luminescent material of the present invention has the chemical formula [(CH3CH2)4N]Eu[CH2(SO3)2]2, wherein Eu 3+ For metal sites, [CH2(SO3)2] 2- and Eu 3+ Chelating coordination forms a one-dimensional anionic framework, with the guest cation being CH3CH2)4. + They are distributed in the crystal lattice to form host-guest compounds.

[0006] Preferably, the luminescent material is a colorless and transparent crystal.

[0007] Preferably, the crystal belongs to the monoclinic crystal system, space group I2 / a, and its unit cell parameters are: α=90°, β=102.448(6)°, γ=90°, Z=9,

[0008] Preferably, the luminescent material has emission peaks of 593nm, 613nm and 700nm when excited by 394nm ultraviolet light and 464nm blue light, and the emitted visible light is red light.

[0009] The preparation method of the rare earth organic-inorganic hybrid luminescent material of the present invention includes the following steps:

[0010] (1) The organic amine source (CH3CH2)4N + A mixture of europium source and methanedisulfonic acid source is dissolved in water to obtain a mixed solution;

[0011] (2) Adjust the pH of the mixed solution prepared in step (1) to acidic, and then heat it at a constant temperature to volatilize it. The colorless and transparent crystals that precipitate out are the final product.

[0012] Under acidic conditions, the organic amine (tetraethylamine) is completely protonated to form the guest cation (CH3CH2)4N. + rare earth ions Eu 3+ With [CH2(SO3)2] 2- Chelation forms a special one-dimensional chain anionic skeleton, which attracts the guest cation (CH3CH2)4N through electrostatic attraction. + Interspersed within a one-dimensional chain lattice, thus constructing Eu 3+ crystalline one-dimensional chain coordination polymers.

[0013] Preferably, in step (2), the constant temperature heating temperature is 35-45℃.

[0014] Preferably, in step (2), the pH of the mixed solution is 4 to 7.

[0015] In step (2), the organic amine source is one or more of tetraethylammonium chloride, tetraethylammonium bromide, and tetraethylammonium hydroxide; the methyl disulfonic acid source is derived from one or more of methyl disulfonic acid, potassium methyl disulfonate, and sodium methyl disulfonate; and the europium source is one or more of europium chloride or europium oxide. More preferably, the organic amine source is tetraethylammonium chloride [(CH3CH2)4NCl]; the europium source is europium chloride (EuCl3·6H2O) containing water of crystallization; and the methyl disulfonic acid source is methyl disulfonic acid [CH2(SO3H)2].

[0016] Invention Mechanism: Rare earth metals possess abundant energy level structures and transition types, generating rich fluorescence spectra in the ultraviolet to near-infrared bands, and are therefore often used as luminescent centers in optical materials. Eu 3+ It is one of the most important optically active luminescent ions, which can be derived from... 5 D0 excited state to 7 F J (J = 0-6) The ground state produces pure red fluorescence. Therefore, Eu is used. 3+ Using ions as metal sites to self-assemble organic-inorganic hybrid compounds is a strategy for synthesizing novel red luminescent materials. In fact, Eu... 3+ As a metal site in an organic-inorganic hybrid compound, its narrow red band emission is caused by transitions between electric and magnetic dipoles.

[0017] This invention utilizes an organic cationic tetraethylammonium chloride and a bridging ligand, methanedisulfonic acid, to achieve a one-step self-assembly of a crystalline compound of a one-dimensional chain-like coordination polymer. Under ultraviolet light excitation, this compound exhibits a high quantum yield of 73.4%. More importantly, under blue light excitation at 464 nm, this crystalline compound achieves a high quantum yield of 48.2%, which is significant in the Euler-Hydrogen-Alder (EuHydrogen-Alder) range. 3+ There have been no reports on coordination aggregation.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The rare earth organic-inorganic hybrid luminescent material has efficient blue light excitation and ultra-high thermal stability, and has good fluorescence performance; (2) Under the excitation of 394nm ultraviolet light and 464nm blue light, its solid quantum yield is 73.38% and 48.2% respectively, and the fluorescence lifetime is 3.066ms; (3) The rare earth organic-inorganic hybrid luminescent material is a solid crystal with ultra-high stability, and its thermogravimetric results remain stable before 727K; (4) The preparation method of the rare earth organic-inorganic hybrid luminescent material is simple, the raw material utilization rate is high, the yield is high and the sample purity is high. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the crystal structure of sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 in Example 1 of the present invention;

[0020] Figure 2 The X-ray powder diffraction pattern of sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 in Example 1 of this invention;

[0021] Figure 3 The thermogravimetric analysis curve of sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 in Example 1 of this invention;

[0022] Figure 4 The excitation and emission spectra of sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 in Example 1 of this invention;

[0023] Figure 5 The photoluminescence quantum yield spectrum of sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 excited at 394 nm UV in Example 1 of this invention;

[0024] Figure 6 The photoluminescence quantum yield spectrum of sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 excited by 464nm blue light in Example 1 of this invention;

[0025] Figure 7 The photoluminescence fluorescence lifetime spectrum of sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 in Example 1 of this invention;

[0026] Figure 8 The sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 powder in Example 1 of this invention and commercial green powder (Ba,Sr)2SiO4:Eu 2+ Photoemission spectrum of the mixed LED using a 465nm chip and CIE coordinate diagram of the fabricated white LED;

[0027] Figure 9 The temperature-dependent emission spectrum of sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 in Example 1 of this invention is shown. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the embodiments.

[0029] Example 1

[0030] The rare-earth organic-inorganic hybrid luminescent material of the present invention has the chemical formula [(CH3CH2)4N]Eu[CH2(SO3)2]2, and its preparation method includes the following steps:

[0031] Add 0.9g of tetraethylammonium chloride and 1.92g of methanedisulfonic acid to a beaker containing 15.0g of deionized water, and stir slowly until homogeneous. Separately, weigh 2g of europium chloride hexahydrate into a 50ml empty beaker, add 10g of distilled water, and stir slowly until completely dissolved to obtain a colorless, transparent solution. Slowly add the solution containing tetraethylammonium chloride and methanedisulfonic acid to the beaker containing europium chloride hexahydrate, stirring constantly until homogeneous. Adjust the pH of the system to 4–7 using HCl, then place the mixture on a 35°C hot plate for evaporation. After 15 days, colorless, transparent, small, ribbon-like crystals precipitate, which is europium. This is the rare-earth organic-inorganic hybrid luminescent material, with a yield of approximately 70% based on tetraethylammonium chloride.

[0032] Raw materials: EuCl3·6H2O (≥99.999%, Shanghai Dibai Biotechnology Co., Ltd.), (CH3CH2)4NCl (≥97%, Pijiasole), and CH2(SO3H)2 (≥97%, Maclean's). All chemicals were used as is without further special treatment.

[0033] Example 2

[0034] The rare-earth organic-inorganic hybrid luminescent material of the present invention has the chemical formula [(CH3CH2)4N]Eu[CH2(SO3)2]2, and its preparation method includes the following steps:

[0035] 2.31 g of tetraethylammonium iodide and 2.12 g of sodium methanedisulfonate were added to a beaker containing 15.0 g of deionized water and stirred slowly until homogeneous. Separately, 2 g of europium chloride was weighed into a 50 ml empty beaker, and 10 g of distilled water was added. The mixture was stirred slowly until completely dissolved, yielding a colorless and transparent solution. The solution containing tetraethylammonium iodide and sodium methanedisulfonate was slowly added to the beaker containing europium chloride, and the mixture was stirred continuously until homogeneous. The pH of the system was adjusted to 4–7 using HCl. The mixture was then placed on a 35°C hot plate for evaporation. After 15 days, colorless and transparent small strip-shaped crystals precipitated, which were europium crystals. This was the rare-earth organic-inorganic hybrid luminescent material, with a yield of approximately 70% based on tetraethylammonium chloride.

[0036] Raw materials: EuCl3 (≥99.999%, Bisoxane), (CH3CH2)4NI (≥98%, Bisoxane), and CH3NaO3S (≥99%, Maclean's). All chemicals were used as is without further special treatment.

[0037] Product characterization

[0038] The test conditions for the samples are as follows:

[0039] (1) X-ray powder diffraction phase analysis (XRD) was performed on a Rigaku DMax X-ray diffractometer.

[0040] (2) Excitation spectrum, emission spectrum, fluorescence lifetime and quantum yield were obtained on an FLS980 spectrometer (Edinburgh) equipped with a continuous xenon lamp (450W), a pulsed flash lamp and a 345nm picosecond pulsed laser.

[0041] (3) X-ray single crystal diffraction experiments were conducted on a Rigaku Oxford Diffraction, 2019 diffractometer with a Mo target and a Kα radiation source (λ = 0.071073 nm). The test temperature was room temperature (~302 K), and the structure was analyzed by Olex2.

[0042] (4) Thermogravimetric (TG) test was performed on a NETZSCH STA 449F3 instrument in a dry N2 atmosphere. 2 At 15K·min -1 The heating rate is determined.

[0043] (1) Single crystal analysis of the sample

[0044] The product prepared in Example 1 was selected with dimensions of 0.10 × 0.20 × 0.25 mm. 3 The crystals were used for single-crystal structure analysis. Single-crystal diffraction data were collected on a Rigaku Oxford Diffraction 2019 diffractometer using the XtaLABSynergy R, DW system, HyPix method. X-rays were taken from a Rigaku (Mo) X-ray source, and the sample structure was resolved using Olex2. The obtained compound [(CH3CH2)4N]Eu[CH2(SO3)2]2 is an ABX2 type rare-earth organic-inorganic hybrid compound. Specific data on the crystal structure of this compound are shown in Table 1.

[0045] Table 1. Crystallographic data of [(CH3CH2)4N]Eu[CH2(SO3)2]2

[0046]

[0047]

[0048] The sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 crystal belongs to space group I2 / a. Figure 1 Thus, one trivalent Eu ion and four [CH2(SO3)2] ions are obtained. 2-Anions form 8-coordinates, and guest cations are distributed in the crystal lattice through intermolecular interactions.

[0049] (2) Powder X-ray diffraction characterization of the sample

[0050] The XRD pattern of the powder [(CH3CH2)4N]Eu[CH2(SO3)2]2 prepared in Example 1 is shown below. Figure 2 As shown.

[0051] like Figure 2 The following is the theoretical XRD diffraction pattern obtained from the simulation of its crystal structure. The experimental diffraction peaks of sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 are in the same position as the simulated peaks, indicating that the obtained samples are all pure phases.

[0052] (3) Thermogravimetric analysis characterization of the samples

[0053] The thermogravimetric analysis (TGA) spectrum of the sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 prepared in Example 1 is shown below. Figure 3 As shown.

[0054] Depend on Figure 3 It can be seen that the sample has good thermal stability before 727K, after which it begins to thermally decompose.

[0055] Performance Characterization

[0056] (1) Excitation-emission spectrum and fluorescence lifetime of the sample

[0057] The excitation and emission spectra of the sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 prepared in Example 1 are as follows: Figure 4 As shown.

[0058] Depend on Figure 4 It was found that the sample exhibited the same emission peaks under ultraviolet light excitation at 394 nm and 464 nm, respectively, at 593 nm, 613 nm, and 700 nm, and the intensity of the emission peaks changed with the excitation wavelength. The fluorescence lifetime was 3.066 ms.

[0059] (2) Quantum yield test of the sample

[0060] Depend on Figure 5 and 6 It was found that the quantum yields of the sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 prepared in Example 1, under UV excitation at 394 nm and photoluminescence at 464 nm, were 73.38% and 73.38%, respectively. Figure 5 ), 48.2% Figure 6 ).

[0061] (3) Photoluminescence lifetime test of the sample

[0062] Depend on Figure 7 The fluorescence decay curves of the sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 prepared in Example 1, measured at the peak wavelengths of the emission and excitation spectra, showed an average lifetime of 3.066 ms based on the double exponential function fitting.

[0063] (4) Application of the sample in white LEDs

[0064] Example 1: The prepared sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 single crystal material and the commercial green phosphor (Ba,Sr)2SiO4:Eu 2+ The photoluminescence spectrum of white LEDs fabricated using 460–465 nm chips is shown below. Figure 8 As shown.

[0065] Depend on Figure 8 It can be seen that the white LED prepared from the sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 prepared in Example 1 has CIE coordinates (0.33, 0.33), a correlated color temperature (CCT) of 8877K, and a color rendering index (CRI) of 93.1.

[0066] (5) Temperature-dependent photoluminescence of the sample

[0067] Depend on Figure 9 It can be seen that the sample [(CH3CH2)4N]Eu[CH2(SO3)2]2 prepared in Example 1 exhibits a temperature-dependent emission spectrum in the range of 303 to 533 K. The intensity decreases with increasing temperature. At 423 K, the luminescence intensity is 54.5% of that at room temperature, and it still exhibits red fluorescence emission at 533 K.

Claims

1. A rare-earth organic-inorganic hybrid luminescent material, characterized in that, Its chemical formula is [(CH3CH2)4N]Eu[CH2(SO3)2]2, where Eu 3+ For metal sites, [CH2(SO3)2] 2- and Eu 3+ Chelating coordination forms a one-dimensional anionic framework, with the guest cation [(CH3CH2)4N]. + A host-guest compound is formed distributed within the crystal lattice; the luminescent material is a crystal, and the crystal belongs to the monoclinic crystal system. I 2 / a The space group has the following cell parameters: a = 9.7059(6) Å, b = 9.6380(5) Å, c =22.2940(14) Å, α = 90°, β = 102.448(6)°, γ = 90°, Z = 9, V = 2036.5(2) Å 3 .

2. The rare-earth organic-inorganic hybrid luminescent material according to claim 1, characterized in that, The luminescent material is a colorless and transparent crystal.

3. The rare-earth organic-inorganic hybrid luminescent material according to claim 1, characterized in that, The luminescent material exhibits emission peaks of 593 nm, 613 nm, and 700 nm when excited by 394 nm ultraviolet light and 464 nm blue light, and emits red visible light.

4. A method for preparing the rare-earth organic-inorganic hybrid luminescent material according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) The organic ammonium source (CH3CH2)4N + A mixture of europium source and methanedisulfonic acid source is dissolved in water to obtain a mixed solution; (2) Adjust the pH of the mixed solution prepared in step (1) to acidic, and then heat it at a constant temperature to volatilize it. The colorless and transparent crystals that precipitate out are the final product.

5. The method for preparing the rare-earth organic-inorganic hybrid luminescent material according to claim 4, characterized in that, In step (2), the constant temperature heating temperature is 35~45℃.

6. The method for preparing the rare-earth organic-inorganic hybrid luminescent material according to claim 4, characterized in that, In step (2), the pH of the mixed solution is 4 to 7.

7. The method for preparing the rare-earth organic-inorganic hybrid luminescent material according to claim 4, characterized in that, The organic ammonium source is one or more of tetraethylammonium chloride, tetraethylammonium bromide, and tetraethylammonium hydroxide.

8. The method for preparing the rare-earth organic-inorganic hybrid luminescent material according to claim 4, characterized in that, The methyl disulfonic acid source is one or more of methyl disulfonic acid, potassium methyl disulfonic acid, and sodium methyl disulfonic acid.

9. The method for preparing the rare-earth organic-inorganic hybrid luminescent material according to claim 4, characterized in that, The europium source is europium chloride or europium oxide.

Images