CN102153576A - Rare earth complex coated with silicon dioxide and preparation method of rare earth complex - Google Patents

Abstract

The invention provides a rare earth complex coated with silicon dioxide and a preparation method of the rare earth complex, wherein the rare earth complex is a particle product formed by using the rare earth complex as a nuclear body and using the silicon dioxide generated after a silicon dioxide precursor is hydrolyzed as a surface coating object. A fluorescence test shows that the fluorescence intensity of the coated rare earth complex is obviously strengthened. Meanwhile, the obtained rare earth complex has the characteristic that the rare earth complex coated with the silicon dioxide is insoluble in an organic solvent. By adopting the method, the cost of rare earth can be reduced to the great extent.

Description

Silicon dioxide-coated rare earth complex and preparation method thereof

technical field

The invention provides a silicon dioxide-coated rare earth complex, which is a granular substance formed by using the rare earth complex as a nucleus, and the silicon dioxide formed after the hydrolysis of a silicon dioxide precursor as a surface coating, and its Preparation. Fluorescence test shows that the fluorescence intensity of the coated rare earth complex has been enhanced. The obtained rare earth complex has the characteristic of being insoluble in organic solvents.

Background technique

my country is rich in rare earth resources, and the deep processing of rare earth resources to produce new functional materials with high added value has important scientific value and practical significance. Rare earth complexes have unique advantages as luminescent materials, such as high internal quantum efficiency, emission peak width at half maximum of about 10nm, and high color purity. Rare earth complexes have special applications in anti-counterfeiting, fluorescent probes, and luminescent displays.

Improving the fluorescence properties of rare earth complexes, including fluorescence intensity and stability, is of great significance for their practical applications. At present, the main method is to improve the type and structure of the ligands coordinated with rare earth ions. Some rare earth researchers have studied the hybrid luminescent materials of inorganic and organic rare earth complexes. Incorporate rare earth complexes into the inorganic network structure in order to obtain luminescent materials that have both the advantages of organic and inorganic materials. For example, see Hench L L, West J K. The sol-gel process. Chem. Rev. , 1990, 90(1): 33-72; Xu Q H, Fu L S, Li L S, et al.J.Mater.Chem., 2000, 10(11), 2532-2536; Bekiari V, Lianos P .Adv.Mater., 1998, 10(17):1455-1458; Carlos L D, Sa Ferreira R A, Rainho J P, et al.Adv.Func.Mater., 2002, 12:819-823; Embert F , Mehdi A, Reye C, et al.Chem.Mater., 2001, 13:4542-4549; Dong D W, Jiang S C, Men Y F, et al.Adv.Mater., 2000, 12(9): 646-649; Henandez R, Franville A C, Minoofar P, et al.J.Am.Chem.Soc., 2001, 123:1248-1249; Minoofar P N, Hemandez R, Chia S, et al.J.Am .Chem.Soc., 2002, 124:14388-14396.

The following literature also involves many achievements in the composite materials of rare earth complexes and their electroluminescence: Zhao Ying, Yang Li-min, Zhang Li, et al. (Zhao Ying, Yang Limin, Zhang Li, etc.), Acta Polymerica Sinica (Gao Acta Molecule Sinica), 2000, 4:393-396; Guo Dong, Liang Chun-jun, Lin Peng, et al. (Guo Dong, Liang Chunjun, Lin Peng, etc.), Journal of The Chinese Rare Earth Society (Chinese Journal of Rare Earth Society), 2004, 22(6): 879-882; Zhang Li, Yang Zhan-lan, Sun Ying, et al. (Zhang Li, Yang Zhanlan, Sun Ying, etc.), Spectroscopy and Spectral Analysis (Spectroscopy and Spectral Analysis), 2000, 20(5):661-662; Tao Dong-liang, Zhang Ting, Xu Yi-zhuang, et al. (Tao Dongliang, Zhang Ting, Xu Yizhuang, etc.), Journal of The Chinese Rare Earth Society (Chinese Journal of Rare Earth), 2001 , 19(6): 543-547; Tao DL, Xu Y Z, Zhou F S, et al. Thin Solid Films, 2003, 436: 281-285; Tao DL, Xu Y Z, Feng J, et al. Journal of Materials Chemistry, 2004, 14: 1252-1256; Pan Y F, Zheng A N, Hu FZ, et al. Journal of Applied Polymer Science, 2006, 100: 1506-1510.

Although rare earth complexes have many advantages, including color purity and solubility, as hybrid materials with inorganic-organic coordination, they have always been weaker than inorganic rare earth luminescent materials in terms of fluorescence stability. In order to solve this difficult problem, Zhao Ying et al. (see Acta Polymerica Sinica (Acta Polymerica Sinica), 2000, 4: 393-396) disclose a kind of method that adopts macromolecular polymethyl methacrylate composite rare earth complex, and studied Luminescent properties of the prepared materials. This method improves the stability of rare earth complexes to a certain extent. Pan Yuanfeng et al. (Journal of Applied Polymer Science, 2006, 100: 1506-1510) used polymer monomer acrylic acid to react with rare earth ions to form a rare earth complex, and then copolymerized with styrene to prepare a new polymer rare earth complex, thereby realizing In order to introduce rare earth complexes into polymer chains. However, this method needs to choose a suitable ligand, because the acrylic acid monomer determines its spatial structure and must select an appropriate ligand to form a complex. In general, it is difficult for ligands with relatively large molecular weight to form rare earth complexes together, which affects the fluorescence properties of the final rare earth complexes to a certain extent.

Therefore, there is an urgent need to provide a rare earth complex with novel structure and excellent performance and a preparation method thereof.

Contents of the invention

Therefore, one of the objects of the present invention is to provide a rare earth complex coated with silica; another object of the present invention is to provide a method for preparing such a rare earth complex coated with silica.

The inventors of the present invention have found through diligent research that if the rare earth complex with fluorescent properties is used as the core and the silicon dioxide produced after the hydrolysis of the silicon dioxide precursor is used as the surface coating, it can self-assemble to form a silicon dioxide coating. Coated rare earth complexes. The rare earth complexes before coating are soluble in organic solvents, but the rare earth complexes prepared according to the present invention are insoluble in organic solvents, which shows that the effect of surface coating is very significant; the results of fluorescence tests show that the rare earth complexes after coating The fluorescence intensity of the object was significantly enhanced. The present invention has thus been accomplished.

The present invention is specifically described below.

In one embodiment of the present invention, a rare earth complex coated with silica is provided, which uses the rare earth complex as the core body and the silica formed after the hydrolysis of the silica precursor as the surface coating. The granular matter formed, the rare earth complex is a rare earth complex capable of emitting fluorescence, preferably a multi-component complex formed by europium, terbium, dysprosium and a small organic molecule as a ligand, and the silicon dioxide precursor is able to A silicon-based material that produces silicon dioxide.

In another embodiment, the rare earth complex is Eu(TTA) ₃ phen, Tb(aspirin) ₃ phen, Dy(TTA) ₃ phen, preferably Eu(TTA) ₃ phen, wherein phen is o-phenanthroline, TTA is 2-thiophenetrifluoromethylacetylacetonate and aspirin is acetylsalicylic acid. The silica precursor is tetraethyl orthosilicate (TEOS). These rare earth complexes are known, and their preparation methods and structural characterizations are covered in a large number of documents, such as the documents mentioned in the background art. The present invention can use these rare earth complexes directly, or firstly prepare them according to the methods described in these documents, and then coat them.

In another embodiment, the silica-coated rare earth complex is SiO ₂ /Eu(TTA) ₃ phen, which has a sharp emission peak at 617.4 nm.

The silica-coated rare earth complexes mentioned in the above embodiments were prepared by the methods described in the following preparation embodiments.

In one preparation embodiment of the present invention, there is provided a method for preparing a silica-coated rare earth complex, which uses the rare earth complex as a core material, disperses it in an organic solvent, and hydrolyzes the silica precursor The silicon dioxide formed after that forms the surface coating of the core material, thereby forming a granular silicon dioxide-coated rare earth complex. The rare earth complex used is a rare earth complex capable of emitting fluorescence, preferably europium, terbium, Dysprosium is a multi-component complex formed by a small organic molecule as a ligand, and the silicon dioxide precursor used is a silicon-based material that can generate silicon dioxide through hydrolysis.

In another preparation embodiment, the rare earth complexes used are Eu(TTA) ₃ phen, Te(aspirin) ₃ phen, Dy(TTA) ₃ phen, preferably Eu(TTA) ₃ phen. The silica precursor employed was tetraethyl orthosilicate (TEOS).

In another preparation embodiment, the organic solvent is any solvent capable of dispersing rare earth complexes, such as alcohols, ketones and halogenated alkanes, etc., preferably alcohol solvents, such as methanol, ethanol or isopropanol.

In another preparation embodiment, the formed silica-coated rare earth complex is SiO ₂ /Eu(TTA) ₃ phen, which has a sharp emission peak at 617.4 nm.

In another preparation embodiment, the rare earth complex and the silica precursor are dispersed in an organic solvent such as methanol, ethanol, or isopropanol, and the dispersion is sonicated, followed by stirring. A mixture of ammonia water, deionized water and methanol, ethanol or isopropanol is added to the dispersion, the product is separated after continuous stirring and washed with an organic solvent such as methanol, ethanol or isopropanol. The product is dried to obtain the final product.

In another preparation embodiment, Eu(TTA) _3phen and TEOS were dispersed in isopropanol. The dispersion was sonicated and then stirred. A mixture of ammonia water (28%), deionized water and isopropanol was added to the dispersion. After continuous stirring, the product was isolated and washed with isopropanol. The product is dried at a temperature of 70-100°C, preferably 80-90°C, to obtain the final product.

The research of the present invention finds that the chemical composition and structure of the rare earth complex do not change after being coated with silicon dioxide. However, its fluorescence intensity has changed greatly. For example, after Eu(TTA) ₃ phen is coated with silica, the intensity of the fluorescence emission peak is increased by more than 2 times, and a sharp emission peak appears at 617.4nm. Although not bound by any theory, these results can be interpreted as: after being coated with silica, the rare earth complex is bound to a certain extent, making its molecules more compact and rigid, and the molecular thermal vibration is weakened. The fluorescence intensity is enhanced because the energy lost by thermal vibration is reduced.

The silica-coated rare earth complex of the present invention or the coated rare earth complex prepared according to the method of the present invention is a new type of rare earth luminescent material, which shows new advantages. Compared with the uncoated existing For rare earth complexes, the solvent resistance is improved, and the cost performance is significantly improved.

As a new type of functional rare earth complex, the coated rare earth complex of the present invention has the characteristics of an inorganic-organic hybrid material, which not only saves rare earth resources, but also improves the stability of the rare earth complex. , fluorescent probes have important application value, and can also be used in electroluminescent devices. By controlling the particle size of this silica-coated rare earth complex and then serving as the light-emitting layer of an electroluminescent device, the stability of the device will be improved.

Therefore, the silicon dioxide-coated rare earth complex of the present invention not only solves the problem of the stability of the rare earth complex itself, but also prepares a new type of high value-added rare earth luminescent material with enhanced fluorescence.

Description of drawings

Figure 1 is the emission spectrum of the rare earth complex Eu(TTA) ₃ phen and the rare earth complex SiO ₂ /Eu(TTA) ₃ phen coated with silica, the excitation wavelength is 383nm; where the dotted line represents the spectrum of the rare earth complex Figure, the solid line represents the spectrogram of the rare earth complex coated with silica;

Figure 2 is the excitation spectrum of the rare earth complex Eu(TTA) ₃ phen and the rare earth complex SiO ₂ /Eu(TTA) ₃ phen coated with silica, the detection wavelength is 611nm; where the dotted line represents the spectrum of the rare earth complex Figure, the solid line represents the spectrogram of the rare earth complex coated with silica;

Figure 3 is the fluorescence decay curve of the rare earth complex Eu(TTA) ₃ phen, in which the relatively smooth curve in the upper figure is the fitted decay curve, and the other jagged curve is the actual decay curve; in the lower figure, the Curved jagged curves are residuals;

Figure 4 is the fluorescence decay curve of the rare earth complex SiO ₂ /Eu(TTA) ₃ phen coated with silica, in which the relatively smooth curve in the above figure is the fitted decay curve, and the other jagged curve is the actual Attenuation curve; in the figure below, the jagged curve is the residual;

Fig. 5 is an electron micrograph of the rare earth complex SiO ₂ /Eu(TTA) ₃ phen coated with silicon dioxide, and its appearance is granular.

Detailed ways

The present invention will be further described below with preferred specific embodiments and in conjunction with the accompanying drawings. The features and advantages of the present invention will become clearer with these descriptions. However, these embodiments are illustrative only, and do not constitute any limitation to the protection scope of the present invention. Those skilled in the art understand that, without exceeding or departing from the scope of protection of the present invention, there are various modifications, improvements or equivalents to the technical solutions and implementations of the present invention, all of which should fall within the scope of protection of the present invention.

Taking the rare earth complex Eu(TTA) ₃ phen as an example, the silicon dioxide-coated rare earth complex SiO ₂ /Eu(TTA) is prepared by hydrolyzing tetraethyl orthosilicate (TEOS) as the silica precursor. ₃ phen.

Obviously, those skilled in the art can understand that other rare earth complexes similar to the rare earth complex Eu(TTA) ₃ phen, such as Tb(aspirin) ₃ phen and Dy(TTA) ₃ phen, etc., can also be obtained by the method described in the following examples The corresponding silica-coated rare earth complexes were prepared by the same method, and their spectroscopic characteristics are similar to those of the silica-coated rare earth complexes SiO ₂ /Eu(TTA) ₃ phen, which will not be repeated here.

Example 1

Preparation of Rare Earth Complex Eu(TTA) ₃ phen

Eu ₂ O ₃ (purity 99.99%) was dissolved in dilute hydrochloric acid, evaporated slowly and then cooled to precipitate white crystal EuCl ₃ ·6H ₂ O, which was filtered and placed in a desiccator to dry for later use. 1 mmol of EuCl ₃ .6H ₂ O and 3 mmol of 2. Thiophene trifluoroacetylacetone (TTA) was dissolved in 20 mL of absolute ethanol. Then, 3 mmol of triethylamine (0.42 mL) was added. Finally, 1 mmol of phenanthroline (phen) was added, and a white precipitate was formed. After stirring for 0.5 h, the precipitate was suction-filtered, washed with absolute ethanol for several times, and then suction-filtered again, and put into a desiccator to dry for later use.

The secondary elemental analysis results of the sample are shown in Table 1, which is consistent with the theoretical value calculated by Eu(TTA) ₃ phen; its emission spectrum at an excitation wavelength of 383nm is shown in Figure 1, and its emission spectrum at a detection wavelength of 611nm The excitation spectrum is shown in Figure 2, which is consistent with the spectrum of Eu(TTA) ₃ phen reported in the literature.

Table 1: Elemental analysis results of rare earth complexes

samples C h N Eu(TTA) ₃ phen 43.58% 2.29% 3.02% Eu(TTA) ₃ phen 43.56% 2.27% 2.98%

Example 2

Preparation of Silica Coated Rare Earth Complex SiO ₂ /Eu(TTA) ₃ phen

0.2 g of Eu(TTA) ₃ phen and 2 mL of TEOS were dispersed in 20 mL of isopropanol. The solution was placed in a sonicator for ultrasonic treatment for 1 h, then the solution was transferred to a flask for electric stirring, and the stirring rate was maintained at 3000 n/min. Add 1 mL of ammonia water (28%), 1 mL of deionized water and 5 mL of isopropanol mixture into the flask at one time, continue to stir for 20 h, then centrifuge the product and wash it several times with isopropanol. The product was dried at 80°C for 12 hours to obtain the final product.

The mass of the final product was weighed to be 0.3 g. This shows that about 0.1 g is due to the silica coating on the surface of Eu(TTA) ₃ phen.

The secondary elemental analysis results of the final product are shown in Table 2, and the content of C, H, and N elements is lower than the corresponding value in Eu(TTA) ₃ phen.

The emission spectrum of the final product at an excitation wavelength of 383nm is shown in Figure 1, and SiO ₂ /Eu(TTA) ₃ phen has an obvious peak at 617.4nm. The excitation spectrum at the detection wavelength of 611 nm is shown in FIG. 2 .

Table 2: Elemental analysis results of silica-coated rare earth complexes

samples C h N SiO ₂ -Eu(TTA) ₃ phen 37.91% 2.05% 2.42% SiO ₂ -Eu(TTA) ₃ phen 37.79% 2.04% 2.39%

Test Example 3

Fluorescence Spectrum Determination of SiO ₂ /Eu(TTA) ₃ phen

Fluorescence spectra were measured on a F-4500 fluorescence spectrophotometer. Both excitation and emission slits are 1 nm. In order to compare the fluorescence intensity, the fluorescence spectra of the samples were measured at the same time period.

Fig. 1 is the emission spectrum diagram of the rare earth complex Eu(TTA) ₃ phen and the silicon dioxide-coated rare earth complex SiO ₂ /Eu(TTA) ₃ phen, the excitation wavelength is 383nm. It can be seen from the figure that the main emission peaks of the two at 611.6nm are very sharp, and there is no change in the position of the emission peak. This shows that the silica coating has no effect on the energy levels of rare earth ions. However, SiO ₂ /Eu(TTA) ₃ phen has an obvious peak at 617.4nm, while Eu(TTA) ₃ phen has no obvious peak shape at this position, and the peak can only be separated by curve fitting.

According to the energy level diagram of rare earth Eu ³⁺ , the emission peaks of the rare earth Eu complex should have seven emission peaks, all of which can be clearly seen in the emission spectrum of SiO ₂ /Eu(TTA) ₃ phen, located at 579.6nm, 590.2 nm, 596.6nm, 611.6nm, 625.2nm, 617.4nm and 652.0nm, corresponding to the energy level transition of Eu ³⁺ as ⁵ D ₀ - ⁷ F ₀ , ⁵ D ₀ - ⁷ F ₁ , ⁵ D ₀ - ⁷ F ₂ , ⁵ D ₀ - ⁷ F ₃ , ⁵ D ₀ - ⁷ F ₄ , ⁵ D ₀ - ⁷ F ₅ and ⁵ D ₀ - ⁷ F ₆ . Most notably, after silica coating, the intensity of the fluorescence emission peak has been greatly enhanced, more than 2 times higher.

Fig. 2 is the excitation spectrum diagram of Eu(TTA) ₃ phen and SiO ₂ /Eu(TTA) ₃ phen, and the detection wavelength is 611nm. It can be seen from the figure that the peak shapes of the excitation spectra of the two are similar, which indicates that the silica coating has no effect on the molecular composition of Eu(TTA) ₃ phen, because the excitation spectrum of the rare earth complex is closely related to the molecular composition. Silica is only physically coated on the surface of the rare earth complex, and has no chemical reaction with it.

It can be seen that the chemical composition and structure of the rare earth complexes have not changed after being coated with silica. However, its fluorescence intensity changed greatly, and a sharp emission peak appeared at 617.4nm. These results indicated that after silica coating, the Eu(TTA) ₃ phen molecules became more compact and rigid, the molecular thermal vibration was weakened, and the energy loss was reduced, thereby enhancing its fluorescence intensity.

Test Example 4

Measurement of Fluorescence Decay Curves of Eu(TTA) ₃ phen and SiO ₂ /Eu(TTA) ₃ phen

The time lifetime was measured using a steady-state transient time-resolved fluorescence spectrometer (Edinburgh Instruments Ltd., UK). All the drugs used are of analytical grade.

Figure 3 and Figure 4 are the fluorescence decay curves of Eu(TTA) ₃ phen and SiO ₂ /Eu(TTA) ₃ phen. It can be seen by single exponential fitting that the fluorescence lifetime of Eu(TTA) ₃ phen is 810.65 microseconds, while that of SiO ₂ /Eu(TTA) ₃ phen is 764.71 microseconds.

The results show that the fluorescence lifetime of the rare earth complex is shortened after silica coating, which also shows that the fluorescence intensity of the rare earth complex is not directly proportional to its fluorescence lifetime. The fluorescence lifetime indicates the average time that the particle exists in the excited state, and the fluorescence intensity is related to the number of photons emitted after the ligand absorbs energy and transfers it to the rare earth ion. After the rare earth complex is coated with silica, the molecular structure of Eu(TTA) ₃ phen is made more rigid. After the ligand absorbs energy, it will transfer energy to the rare earth ion at a faster rate, which then enhances the fluorescence intensity and reduces the fluorescence lifetime.

The present invention has been described above in conjunction with specific embodiments. However, these embodiments are illustrative only, and do not constitute any limitation to the protection scope of the present invention. Those skilled in the art understand that, without exceeding or departing from the scope of protection of the present invention, there are various modifications, improvements or equivalents to the technical solutions and implementations of the present invention, all of which should fall within the scope of protection of the present invention.

Claims (10)

1. A silicon dioxide-coated rare earth complex is a granular substance formed by using the rare earth complex as a nucleus and the silicon dioxide generated after the hydrolysis of a silicon dioxide precursor as a surface coating. The complex is a rare earth complex capable of emitting fluorescence, preferably a multi-element complex formed by europium, terbium, dysprosium and a small organic molecule as a ligand, and the silicon dioxide precursor is a silicon-based material that can generate silicon dioxide through hydrolysis . 2. The rare earth complex compound coated with silica according to claim 1, characterized in that, the rare earth complex compound is Eu(TTA) ₃ phen, Tb(aspirin) ₃ phen, Dy(TTA) ₃ phen, Preferably Eu(TTA) ₃ phen, phen is o-phenanthroline, TTA is 2-thiophene trifluoromethyl acetylacetonate, aspirin is acetylsalicylic acid, and the silica precursor is tetraethylorthosilicate (TEOS) . 3. The silica-coated rare earth complex according to claim 1 or 2, characterized in that, the silica-coated rare earth complex is SiO ₂ /Eu(TTA) ₃ phen, which is at 617.4 nm has a sharp emission peak. 4. A method for preparing a silicon dioxide-coated rare earth complex, which is to use the rare earth complex as a nucleus material, disperse it in an organic solvent, and form the silicon dioxide formed by the silicon dioxide precursor after hydrolysis The surface coating of bulk materials, thereby forming granular silica-coated rare earth complexes, the rare earth complexes used are rare earth complexes that can emit fluorescence, preferably europium, terbium, dysprosium and organic small as ligands A multi-component complex formed by molecules, the silica precursor used is a silicon-based material that can generate silica through hydrolysis. 5. according to the method for claim 4, it is characterized in that, the rare earth complex that adopts is Eu(TTA) ₃ phen, Te(aspirin) ₃ phen, Dy(TTA) ₃ phen, preferred Eu(TTA) ₃ phen, phen is o-phenanthroline, TTA is 2-thiophenetrifluoromethyl acetylacetonate, aspirin is acetylsalicylic acid, and the silica precursor used is tetraethyl orthosilicate (TEOS). 6. The method according to claim 4 or 5, characterized in that, the organic solvent is a solvent capable of dispersing rare earth complexes, such as alcohols, ketones and halogenated alkanes, etc., preferably alcohol solvents, such as methanol, ethanol or isopropanol. 7. The method according to one of claims 4 to 6, characterized in that the silicon dioxide-coated rare earth complex formed is _SiO2 /Eu(TTA)3phen, which has a sharp emission peak at 617.4 nm. 8. The method according to one of claims 4 to 7, characterized in that the rare earth complex and the silica precursor are dispersed in an organic solvent such as methanol, ethanol or isopropanol, the dispersion is ultrasonically treated and then stirred , the mixture of ammonia water, deionized water and methanol, ethanol or isopropanol is added to the dispersion, the product is separated after continuous stirring and washed with an organic solvent such as methanol, ethanol or isopropanol, and the product is dried to obtain the final product. 9. The method according to one of claims 4 to 8, characterized in that, Eu(TTA) ₃ phen and TEOS are dispersed in isopropanol, the dispersion is ultrasonically stirred, and ammoniacal liquor (28%) , a mixture of deionized water and isopropanol is added to the dispersion, after continuous stirring, the product is separated and washed with isopropanol, and the product is dried at 70-100°C, preferably 80°C-90°C, to obtain the final product. 10. The silica-coated rare earth complex according to any one of claims 1 to 3, characterized in that it is produced by the method according to any one of claims 4 to 9.

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