阅读说明：本技术 一种光色可调的稀土发光材料的制备方法 (preparation method of rare earth luminescent material with adjustable light color ) 是由 王军 何进军 申婧 王家飞 唐佳丽 于 2019-09-18 设计创作，主要内容包括：本发明公开了一种光色可调的稀土发光材料的制备方法,设计并合成了以三联吡啶为稀土离子配位点的大π共轭配体L,配体结构通过<Sup>1</Sup>H NMR以及MS确证。利用稀土离子与三联吡啶的配位聚合,成功制备金属配位聚合物L-Ln。荧光光谱实验研究表明,L-Eu具有激发波长响应的发光行为,当激发波长为295nm时得到近白光发射材料,色坐标为(0.41,0.33)。由此调制得到一种光色可调的稀土发光材料。(The invention discloses a preparation method of a light-color-adjustable rare earth luminescent material, wherein a large pi conjugated ligand L taking terpyridine as a rare earth ion coordination site is designed and synthesized, the ligand structure is confirmed by 1 H NMR and MS, and the successful preparation of a metal coordination polymer L-Ln. fluorescence spectrum experimental study shows that L-Eu has a luminescent behavior with excitation wavelength response, when the excitation wavelength is 295nm, a near-white light emitting material is obtained, and the color coordinate is (0.41,0.33), so that the light-color-adjustable rare earth luminescent material is obtained by modulation.)

1. A preparation method of a rare earth luminescent material with adjustable light color is characterized by comprising the following steps:

Step 1, synthesis of terpyridine ligand L

Dissolving 268mg of terephthalaldehyde and 968mg of 2-acetylpyridine in 20mL of ethanol, stirring for 10min, adding 480mg of NaOH powder, stirring at room temperature for 0.5 h to completely dissolve solids, slowly adding 8mL of ammonia water solution, stirring the mixed solution at 50 ℃, reacting for 24h, cooling to room temperature, filtering a large amount of precipitated solids, drying, separating a crude product by column chromatography, eluting with CHCl ₃, CH ₃ OH (50: 1), spin-drying the solvent, and washing with a small amount of methanol to obtain a pure product 739.5mg, wherein the yield is 68.4%;

Step 2, preparation of coordination polymer L-Ln

The coordination between the ligand and rare earth ions Eu ³⁺ is examined in L2 x 10 ^-5 mol/L CHCl ₃/CH ₃ OH mixed solution through an accumulative sample injection method, the volume ratio of CHCl ₃/CH ₃ OH is 8:2, when the Eu ³⁺ concentration is gradually increased, the absorbance of the ligand at 282nm is gradually reduced, and a shoulder peak appears at 330nm, so that the coordination between the ligand molecules and the rare earth ions exists in a solution state is indicated, and a B-H curve indicates that the ligand L and the Eu ³⁺ ions are coordinated in a stoichiometric ratio of 1: 1;

200mL of CHCl ₃ dissolved with L108mg was placed in a 500mL round bottom flask, EuCl ₃.6H ₂ O73 mg was dissolved in 5mL of methanol and added dropwise to the above mixed solution under stirring at room temperature, stirred at reflux overnight during which a precipitate precipitated out, filtered and washed with CHCl ₃ to obtain a possible structural fragment of coordination polymer L-Eu..

2. The method for preparing a rare earth luminescent material with adjustable light color as claimed in claim 1, wherein L-Eu has luminescence behavior responsive to excitation wavelength, and when the excitation wavelength is 295nm, a near white light emitting material is obtained, and color coordinates are (0.41, 0.33).

3. The method for preparing a rare-earth luminescent material with adjustable light color as claimed in claim 1, wherein the color coordinate CIE is changed with the change of the excitation wavelength from 275nm to 395 nm.

Technical Field

The invention belongs to the technical field of luminescent materials, and relates to a preparation method of a rare earth luminescent material with adjustable light color.

Background

³⁺in recent years, due to the wide application in the fields of flat panel displays, light emitting diodes, lighting, communications and the like, light emitting materials with adjustable light color, especially white light materials, have attracted high attention in academia and industry (chem.rev.2018,118, 8899). white light diodes (WLEDs) are directly considered as a new solid-state light emitting source and are considered as a new innovation in the field of lighting (chem.soc.rev.201424), but traditional mercury-containing white light sources can cause a lot of environmental problems.

It is known that ideal white light with color coordinates (CIE coordinates) of (0.33 ), relative color temperature between 2500-6500K, color rendering index greater than 80(chem. rev.2012,112,1126), is generally compounded by two primary colors (blue and yellow) or three primary colors (red, green, blue) covering the entire visible region (400-700nm), which is the "light color complementation principle" of white light modulation, when modulating white light via heteronuclear/heteronuclear rare earth coordination/polymers, the most common light color composition is blue light based on the center of the ligand, red light of Eu ³⁺, and green light of Tb ³⁺, whereas in Eu ³⁺, Tb 23, int ³⁺/387gd 5 La co-doped white light materials, it is difficult to sensitize due to the higher emission level of La ³⁺/Gd 6, thus, the same trichromatic white light (incorg. chem.2018,57,8714) is also a white light co-doped with Ln ³⁺ to satisfy the complementary requirements, and thus, the same white light color ion strategy is often required to be more efficient than the use of two different rare earth phosphors for white light modulation (No. 20 ).

The rare earth white light material based on the organic ligand has unique light-emitting properties such as high color purity, light-emitting efficiency and the like, and more importantly, the discovery of the white light rare earth material directly promotes the application of the light-emitting diode in the fields of backlight sources, color screens, indoor illumination and the like. For the rare earth luminescent material, the luminescent performance can be regulated and controlled through the change of the concentration and the excitation wavelength of rare earth ions and even the polarity of a solvent. The rare earth luminescent intelligent material with adjustable luminescence is the hot research content which is highly concerned by scientific workers at present and even in a long period of time in the future.

Disclosure of Invention

The invention aims to provide a preparation method of a rare earth luminescent material with adjustable light color. Through the regulation and control of the luminescent property of the rare earth luminescent material, the more intelligent rare earth luminescent material with adjustable light color is developed.

The specific technical scheme is as follows:

A preparation method of a rare earth luminescent material with adjustable light color comprises the following steps:

step 1, synthesis of terpyridine ligand L

268mg (2mmol) of terephthalaldehyde and 968mg (8mmol) of 2-acetylpyridine are dissolved in 20mL of ethanol, 480mg (12mmol) of NaOH powder is added after stirring for 10min, the mixture is stirred at room temperature for 0.5 h to dissolve all solids, 8mL (mass concentration is 28-30%) of ammonia water solution is slowly added, the mixture is stirred at 50 ℃ for reaction for 24h and then cooled to room temperature, a large amount of precipitated solids are filtered and dried, the crude product is separated by column chromatography (an eluent is CHCl ₃: CH ₃ OH ═ 50: 1), and the solvent is dried by spinning and then washed by a small amount of methanol to obtain 739.5mg of a pure product, wherein the yield is 68.4%.

step 2, preparation of coordination polymer L-Ln

The coordination between the ligand and rare earth ions (Eu ³⁺) is examined in a mixed solution of L (2X 10 ^-5 mol/L) CHCl ₃/CH ₃ OH (v/v 8:2) by a cumulative injection method, and when the concentration of Eu ³⁺ is gradually increased, the absorbance of the ligand at 282nm is gradually reduced, and a shoulder appears at 330nm, thereby indicating that the ligand molecules and the rare earth ions have coordination in a solution state, and a B-H curve indicates that the ligand L and the Eu ³⁺ ions are coordinated in a stoichiometric ratio of 1: 1.

200mL of CHCl ₃ in which L108mg (0.2mmol) was dissolved was placed in a 500mL round-bottomed flask, EuCl ₃.6H ₂ O (73mg,0.2mmol) was dissolved in 5mL of methanol and added dropwise to the above mixed solution under stirring at room temperature, and stirred at reflux overnight during which time a precipitate precipitated out, filtered and washed with CHCl ₃ to obtain coordination polymer L-Eu.

Further, L-Eu has a luminescence behavior responsive to an excitation wavelength, and gives a near-white light emitting material having a color coordinate of (0.41,0.33) and a fluorescence lifetime of 0.25ms at an excitation wavelength of 295 nm.

Further, the color Coordinates (CIE) were changed with the change of the excitation wavelength (275nm to 395nm), and the relationship between the color coordinates and the excitation wavelength was as shown in Table 1.

Table 1: color Coordinate (CIE) as a function of excitation wavelength (Ex/nm)

Compared with the prior art, the invention has the beneficial effects that:

The invention designs and synthesizes a large pi conjugated ligand (L) taking terpyridine as a coordination point of rare earth ions, and the ligand structure is confirmed by ¹ H NMR and MS.

Drawings

FIG. 1 is a synthetic route based on a terpyridine ligand L;

FIG. 2 is an ¹ H NMR (CDCl ₃,25 ℃ C.) of ligand compound L;

FIG. 3 shows the MS (25 ℃ C.) of ligand compound L;

FIG. 4 is a UV-visible absorption titration spectrum (solvent CHCl ₃/CH ₃ OH (v/v 7:3)) of ligand L and rare earth ion (Eu ³⁺) and its corresponding B-H curve, wherein (a) is the UV-visible absorption titration spectrum, and (B) is the B-H curve;

FIG. 5 is a schematic representation of a coordination polymer structural segment;

FIG. 6 is an infrared spectrum of a ligand L and a coordination polymer L-Eu;

FIG. 7 is a scanning electron microscope for coordination polymer L-Eu;

FIG. 8 shows the UV-VIS absorption spectrum (left) and the fluorescence spectrum (right) of ligand L;

FIG. 9 is a photograph of L-Eu before (a) and after (b) irradiation with ultraviolet light (365 nm);

FIG. 10 shows the emission spectrum (a) of the coordination compound L-Eu at different excitation wavelengths and the variation of emission intensity at 616nm with excitation wavelength (b) (solid state, 25 ℃ C.);

FIG. 11 is a color coordinate diagram (solid state, 25 ℃ C.) of the coordination compound L-Eu at 295nm excitation;

FIG. 12 is a graph showing the fluorescence lifetime of coordination polymer L-Eu in the solid state;

FIG. 13 is a thermogravimetric analysis of coordination polymer L-Ln in the solid state.

Detailed Description

The technical solution of the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

The technology of the invention is a subsidized project: guizhou province education hall young science talent growth fund (NO. 2016) 141); the luminescent material with adjustable luminescence has potential application in the fields of illumination, communication, anti-counterfeiting and the like.

(1) Synthesis and structural characterization of terpyridine ligand L

The synthetic route of conjugated terpyridine ligand L (1,4-di ([2,2':6',2 '-terpyridin ] -4' -yl) benzene) is shown in figure 1. the specific synthetic process is that 268mg (2mmol) of terephthalaldehyde and 968mg (8mmol) of 2-acetylpyridine are dissolved in 20mL of ethanol, 480mg (12mmol) of NaOH powder is added after stirring for 10min, the solid is completely dissolved after stirring for 0.5 h at room temperature, 8mL (28-30%) of ammonia solution is slowly added, the mixture is stirred for reaction at 50 ℃ for 24h and then cooled to room temperature, a large amount of solid precipitated is filtered, dried, the crude product is separated by column chromatography (the eluent is CHCl ₃: CH ₃ OH ═ 50: 1), and the solvent is dried and then washed by a small amount of methanol to obtain pure product 739.5mg, the yield is 68.4%.

The structure of ligand compound L is confirmed by ¹ H NMR (CDCl ₃ is a deuterated reagent) and high resolution MS (FIG. 2) characterization results are shown in FIGS. 2-3 respectively, nuclear magnetic resonance hydrogen spectrum (FIG. 2) shows ¹ H NMR (CDCl,400MHz) delta: 8.81(s,4H), 8.77(d,4H), 8.71(d,4H), 8.07(s,4H), 7.91(t,4H), 7.38(d,4H), the chemical formula of ligand molecule L is C ₃₆ H ₂₄ N ₆, the exact mass calculation of the compound is 540.2062, the mass ratio of [ M + H ] ⁺ ([ C36H25N6] ⁺) is 541.2141, and MS (FIG. 3) shows 541.2158.

(2) Preparation and characterization of coordination polymer L-Ln

The coordination between the ligand and rare earth ions (Eu ³⁺) was examined in a mixed solution of L (2X 10 ^-5 mol/L) of CHCl ₃/CH ₃ OH (v/v 8:2) by cumulative injection, and the UV-visible titration spectrum is shown in FIG. 4 (a). The spectrum shows that, when the Eu ³⁺ concentration is gradually increased, the absorbance of the ligand at 282nm gradually decreases, and a shoulder appears at 330nm, thereby indicating that the ligand molecules and the rare earth ions are coordinated in the solution state.A B-H (corresponding curve obtained by the Benesi-Hildebrand equation) curve shows that the ligand L and the Eu ³⁺ ions are coordinated at a stoichiometric ratio of 1: 1.

200mL of CHCl ₃ dissolved with L108mg (0.2mmol) was placed in a 500mL round bottom flask, EuCl ₃.6H ₂ O (73mg,0.2mmol) was dissolved in 5mL of methanol and added dropwise to the above mixed solution with stirring at room temperature, stirred at reflux overnight during which time a precipitate precipitated out, filtered and washed with CHCl ₃ to obtain a possible structural fragment of coordination polymer L-Eu. as shown in FIG. 5.

The formation of the coordination polymer is examined by Fourier infrared spectroscopy, and as can be seen from FIG. 6, the wave number is 3059,3017cm ^-1, the C-H stretching vibration on the aromatic ring is shown, 1594 cm ^-1 and 1584cm ^-1 are respectively the skeleton vibration of the carbon-carbon double bond and the carbon-nitrogen double bond on the aromatic ring of the target product, and the absorption of the C-C bond between the aromatic rings is shown at 787cm ^-1.

When ligand L and Eu ³⁺ are assembled to form coordination polymer in coordination driving mode, the coordination polymer should have one-dimensional chain or linear shape, but three-dimensional aggregates are observed in scanning electron microscope characterization (figure 7).

(3) L-Ln optical Property test

The ligand L showed a maximum absorption wavelength at 282nm in a chloroform solution (fig. 8), and the absorption peak was generated by pi-pi transition in the compound, and with 282nm as an excitation wavelength, blue light emission was obtained (λ _max ═ 360nm), and the brown coordination polymer L-Eu did not emit light under natural light irradiation (fig. 9(a)), and red light emission was observed after irradiation with an ultraviolet lamp (365nm) (fig. 9 (b)).

The emission properties of polymer L-Eu were tested in the solid state, and the results are shown in FIG. 10. at an excitation wavelength of 275nm, characteristic emission of Eu ³⁺ in L-Eu was observed, and at ⁵ D ₀/⁷ F ₀ (579nm), ⁵ D ₀/⁷ F ₁ (592nm), ⁵ D ₀/⁷ F ₂ (616nm), ⁵ D ₀/⁷ F ₃ (650nm), and ⁵ D ₀/⁷ F ₄ (692nm), respectively.

(4) Analysis of thermal stability of coordination Polymer L-Ln

thermal stability of the coordination polymer is inspected by thermogravimetric analysis, and the experimental result shows that: the luminescent material has better thermal stability within 515 ℃, the collapse of the coordination polymer at the temperature of 517-580 ℃ causes severe quality attenuation, and finally the luminescent material is directly cracked into rare earth oxide, as shown in figure 13.

the above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, and any simple modifications or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the technical scope of the present invention are within the scope of the present invention.