CN113004475B

CN113004475B - Organic fluorescent material, synthetic method and application thereof

Info

Publication number: CN113004475B
Application number: CN202110128972.9A
Authority: CN
Inventors: 唐安娜; 孔德明; 陈燕; 李薇; 王晓涵; 王汭
Original assignee: Nankai University
Current assignee: Nankai University
Priority date: 2021-01-29
Filing date: 2021-01-29
Publication date: 2022-04-19
Anticipated expiration: 2041-01-29
Also published as: CN113004475A

Abstract

The invention provides an organic fluorescent material, a synthetic method and application thereof, wherein a ketone compound and an aldehyde compound form a covalent organic polymer with a conjugated system through an aldol condensation reaction under an alkaline condition, the fluorescence emission range of the organic fluorescent material is 410-750nm, and the organic fluorescent material shows a double fluorescence phenomenon at 475nm and 610nm, and can be applied to the fields of WLED and information encryption.

Description

Organic fluorescent material, synthetic method and application thereof

Technical Field

The invention belongs to the field of synthesis of organic fluorescent materials, and particularly relates to an organic fluorescent material, a synthesis method and application thereof.

Background

Fluorescent materials are chemical materials which absorb purple light under the irradiation of ultraviolet light (200nm-400nm) and emit certain visible light (400nm-800 nm). Nowadays, fluorescent materials have attracted much attention in the fields of chemistry, biology, medicine, etc., and fluorescent technologies such as sensing detection, biological imaging, drug tracing, photoelectric devices, anti-counterfeiting encryption, etc. are widely used. The development of the fluorescent technology is not independent of fluorescent materials, and most of the existing mature fluorescent materials are metal sulfides, oxides doped with rare earth elements or organic polymers, such as metal-organic frameworks (MOFs), which exhibit excellent fluorescent properties. However, compared with a pure organic fluorescent material without metal, the doping of metal elements causes the defects of environmental pollution, biological toxicity, high cost of rare earth elements, difficulty in flexible design and the like. In pure organic fluorescent materials, small organic molecules are easy to generate fluorescence quenching phenomena in a solid state, and researches show that the existence of internal gaps of high molecular polymers can influence the luminous performance of a luminous substance, promote luminous intensity and luminous efficiency and inhibit the fluorescence quenching phenomena, so that the development of the organic high molecular luminous polymers has important significance for obtaining fluorescent materials with good performance and environmental friendliness.

Most organic polymer fluorescent materials are conjugated polymers, have rigid planar structures and large pi-bond conjugated systems, can reduce energy dissipation caused by vibration and rotation in molecules, and meanwhile, strong pi-conjugated systems can easily cause pi-pi action between rigid planes to cause fluorescence quenching. Therefore, it is still a great challenge to construct organic polymers with good fluorescence properties, and organic polymer light-emitting polymers with dual fluorescence emission and high fluorescence properties are more scarce.

Disclosure of Invention

In order to achieve the above object, an object of the present invention is to provide an organic fluorescent material, wherein a ketone compound and an aldehyde compound form a covalent organic polymer having a conjugated system through an aldol condensation reaction under an alkaline condition.

Preferably, the ketone compound is one of C2 symmetric acetyl or C3 symmetric acetyl aromatic ketone, the aldehyde compound is one of C2 symmetric formyl or C3 symmetric formyl aromatic aldehyde, and the aromatic ketone monomer and the aromatic aldehyde monomer have the following structures:

wherein the content of the first and second substances,

is one of benzene, biphenyl and 1,3, 5-triphenyl benzene.

The method comprises the following specific steps:

c2 is benzene, biphenyl, 1,3, 5-triphenyl benzene symmetrically connected with two formyl or acetyl;

c3 is benzene, biphenyl, 1,3, 5-triphenyl benzene with three formyl or acetyl groups symmetrically connected.

Preferably, the fluorescence emission range of the organic fluorescent material is 410-750nm, and the dual fluorescence phenomenon is shown at 475nm and 610 nm.

The invention also aims to provide a synthetic method of the organic fluorescent material, which comprises the following steps: s1, dissolving the aromatic ketone and the aromatic aldehyde in the organic solvent to be uniformly dispersed to form a mixture a;

s2, adding a catalyst into the mixture a in the step S1, uniformly dispersing, and reacting at 110-120 ℃ for 11-13 hours to form a mixture b;

s3, washing the mixture b in the step S2 by water, DMF, 1, 4-dioxane and ethanol alternately under reflux until the supernatant is colorless;

s4, drying the product washed in the step S3 at 55-65 ℃ for 4-6 hours to obtain the COPs material with double fluorescence emission.

Preferably, in step S1, the aromatic ketone is one of 1,3,5 triacetylbenzene, p-diacetylbenzene, 4' -diacetylbiphenyl, 1,3, 5-tris (4-acetylphenyl) benzene (English name: 1,1' - (5' - (4-acetylphenyl) - [1,1':3', 1' -terphenyl ] -4, 4' -diyl) dione);

the aromatic aldehyde is one of terephthalaldehyde, biphenyldicarboxaldehyde, trimesic aldehyde and 1,3, 5-tri (p-formylphenyl) benzene.

Preferably, in step S1, the organic solvent is one or more of absolute ethyl alcohol, 1, 4-dioxane, n-butanol, dichloromethane, toluene, o-dichlorobenzene or dimethyl sulfoxide.

Preferably, in step S1, the organic solvent is a mixed solvent of ethanol and 1, 4-dioxane, and the volume ratio of ethanol to 1, 4-dioxane is 1: 1.

Preferably, in step S2, the catalyst is one of aqueous solutions of sodium hydroxide, potassium hydroxide, cesium carbonate and potassium tert-butoxide or one of alcoholic solutions of sodium hydroxide, potassium hydroxide, cesium carbonate and potassium tert-butoxide, and preferably, the concentration of the aqueous catalyst solution is 1 to 6mol/L and the concentration of the alcoholic catalyst solution is 0.5 to 1.5 mol/L.

The invention also aims to provide application of the prepared organic fluorescent material in WLED.

Dispersing the prepared organic fluorescent material in an organic solvent DMF, irradiating for 5-8 days under an ultraviolet lamp to obtain white light emission visible to naked eyes, detecting by a solid fluorescence spectrophotometer, coating the COPs material of the obtained white light emission on a purple light LED after the test result corresponds to the white light emission exactly, and realizing the preparation of WLED.

The fourth purpose of the invention is to provide the application of the prepared organic fluorescent material in information encryption.

The prepared organic fluorescent material powder is dispersed in an organic solvent to be used as fluorescent ink, and is coated and written on notepaper with similar color or darker color, so that the notepaper can be difficult to identify under natural light and can be displayed under ultraviolet irradiation, and the application in information encryption is realized.

Compared with the prior art, the organic fluorescent material, the synthetic method and the application thereof in WLED and information encryption have the beneficial effects that:

(1) according to the organic fluorescent material, the synthesis method and the application thereof in WLED and information encryption, the novel COPs material is a pure covalent organic polymer, does not contain metal elements, and has the advantages of small toxicity, environmental friendliness, low cost and the like;

(2) according to the organic fluorescent material, the synthetic method and the application thereof in WLED and information encryption, the novel COPs material has the performance of double fluorescence emission under single-wavelength excitation, and has excellent fluorescence performance in solid and liquid states, wherein the solid fluorescence quantum yield is 9.84%, and the liquid fluorescence quantum yield is 21.2%;

(3) the novel COPs material can obtain various colors by adjusting the intensity ratio of double wavelengths through ultraviolet irradiation;

(4) according to the organic fluorescent material, the synthesis method and the application thereof in WLED and information encryption, the WLED is obtained by combining white light fluorescent powder converted by illumination of the novel COPs material and a purple light LED lamp, so that the organic fluorescent material has important significance for future solid illumination and can also be applied to the information encryption process.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a diagram illustrating the mechanism of the synthesis of organic fluorescent materials (aldol condensation reaction under base catalysis) according to the present invention;

FIG. 2 is a schematic structural diagram of a process for synthesizing a double fluorescence emission COPTAB-TPA-OH of the organic fluorescent material according to the present invention;

FIG. 3 is a schematic diagram of the reaction of C ═ C opening addition polymerization to cyclobutane in the organic fluorescent material COPs (illustrated by COPTAB-TPA-0);

FIG. 4 is a schematic infrared spectrum of the monomers (1,3,5 triacetylbenzene, terephthalaldehyde), the dual fluorescent emission materials COPTAB-TPA-OH and COPTAB-TPA-0 (comparative);

FIG. 5 is a schematic nuclear magnetic representation of the COPTAB-TPA-OH, COPTAB-TPA-0 (control) solids of the present invention;

FIG. 6 is a schematic scanning electron microscope of COPTAB-TPA-OH at different synthesis times according to the present invention;

FIG. 7 is a graph showing the fluorescence spectra (385nm excitation) of the monomers (1,3,5 triacetylbenzene, terephthalaldehyde), COPTAB-TPA-OH, COPTAB-TPA-0 (control) dispersed in DMF, and the solid fluorescence spectra (390nm excitation) of COPTAB-TPA-OH according to the present invention;

FIG. 8 is a schematic representation of the color change of COPTAB-TPA-OH of the present invention when dispersed in DMF following UV irradiation;

FIG. 9 is a schematic representation of the fluorescence spectrum of a COPTAB-TPA-OH solid according to the present invention (390nm excitation) with color transition and its corresponding graph;

FIG. 10 is a schematic view of a white phosphor powder of FIG. 7 coated on a purple LED lamp to prepare a WLED according to the present invention;

FIG. 11 is a schematic diagram of the present invention in which COPTAB-TPA-OH is made into fluorescent ink and characters are written on yellow and off-white notepaper, respectively;

FIG. 12 is a schematic structural diagram of a synthesis process of a novel double fluorescence emission COPTAB-BPDA-OH material according to example 2 of the present invention;

FIG. 13 is a schematic representation of the IR spectrum of COPTAB-BPDA-OH, COPTAB-BPDA-0 (control) according to example 2 of the present invention;

FIG. 14 is a schematic scanning electron microscope of COPTAB-BPDA-OH according to example 2 of the present invention;

FIG. 15 shows fluorescence spectra (385nm excitation) of 1,3,5 triacetylbenzene, biphenyldicarboxaldehyde, COPTAB-BPDA-OH, COPTAB-BPDA-0 (control) dispersed in DMF, an organic solvent, according to example 2 of the present invention;

FIG. 16 is a solid state fluorescence spectrum (390nm excitation) of COPTAB-BPDA-OH according to example 2 of the present invention, with excitation spectrum in black and emission spectrum in red;

FIG. 17 is a solid state fluorescence spectrum (390nm excitation) of COPTAB-BPDA-0 according to example 2 of the present invention;

FIG. 18 is a schematic diagram of the writing of characters on an off-white notepaper with the fluorescent ink of COPTAB-BPDA-OH drawn into a pen according to example 2 of the present invention.

Detailed Description

It is to be noted that, unless otherwise defined, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

Example 1:

the method comprises the following specific steps of synthesizing a novel double-fluorescence-emission COPTAB-TPA-OH material by a solvothermal method:

(1) dissolving 123.9mg of monomer 1,3,5 triacetyl benzene and 121.5mg of monomer terephthalaldehyde in 12ml of mixed solvent of ethanol and 1, 4-dioxane at a volume ratio of 1:1, performing ultrasonic treatment for 10 minutes, and uniformly dispersing to a colorless or light yellow transparent mixture;

(2) adding 0.3mL of 6mol/L sodium hydroxide aqueous solution into the mixture, carrying out ultrasonic treatment for 10min, and transferring the mixture into a reaction kettle after uniform dispersion;

(3) transferring the reaction kettle to a forced air drying oven at 120 ℃ for reaction for 12 hours;

(4) stopping heating, after the reaction kettle is cooled to room temperature, pouring out the reaction product, transferring the reaction product into a Soxhlet extractor, alternately refluxing and washing with water, DMF, 1, 4-dioxane and ethanol for about 4h, and refluxing each solvent until the supernatant is colorless;

(5) finally, taking out the product, and drying the product in a vacuum drying oven at 60 ℃ for 5 hours to obtain a novel COPs material with double fluorescence emission;

(6) a comparative COPTAB-TPA-0 was synthesized by the same procedure as above with 0.1mL of a 6mol/L aqueous solution of sodium hydroxide as a catalyst.

Secondly, applying the novel double-fluorescence-emission COPTAB-TPA-OH material to the WLED preparation:

taking 21mg of COPs from a 10ml centrifugal tube, dispersing in 7ml of DMF solvent, irradiating in an ultraviolet lamp box, arranging an ultraviolet lamp tube with the length of 30cm and the power of 8W in the lamp box, horizontally placing the sample and the lamp light, irradiating for about 8 days after the sample is 2cm away from the lamp light, observing that the sample is changed from orange to near white, centrifugally separating, testing the spectral curve of the sample, and calculating whether the color coordinate accords with the white light coordinate range. Finally, a sample with a proper color is prepared into about 20mg/ml dispersion liquid, the dispersion liquid is lightly coated on commercial ultraviolet lamp beads, the emission wavelength of the ultraviolet lamp beads is about 390nm, and the power is 0.3W.

Thirdly, the novel double-fluorescence emission COPTAB-TPA-OH material is applied to information encryption:

the COPTAB-TPA-OH material with double fluorescence emission is dispersed in organic solvent isopropanol, the concentration of dispersion liquid is 5mg/ml, (DMF is corrosive and corrodes appliances, and non-corrosive organic solvent isopropanol is selected), the dispersion liquid is used as fluorescent ink, a liquid-transferring gun or a pen is used for sucking the ink, characters are lightly coated on yellow or grey-white notepaper, after the isopropanol volatilizes, the characters cannot be distinguished under natural light, and the characters are shown under ultraviolet irradiation, so that information encryption is realized.

Fourthly, the structure and the performance of the novel dual fluorescence emission COPs material prepared by the invention are explained in detail by combining the attached drawings

Experimental example 1: infrared spectroscopic analysis

The novel dual fluorescence emission COPTAB-TPA-OH material prepared in example 1 of the present invention was analyzed by fourier infrared spectroscopy of type TENSOR II, and as a result, as shown in fig. 4, it was confirmed from fig. 4 that the target COPTAB-TPA-OH material and the fully dehydrated control under dilute alkali conditions both retained the characteristic peak of C ═ O from the monomer 1,3,5 triacetylbenzene, 1661nm and 1668nm, respectively, and new characteristic peaks ascribed to C ═ C appeared at 1592nm and 1602nm, respectively, and that the fully dehydrated product COPTAB-TPA-0 observed more distinct trans C peak than the COPTAB-TPA-OH material, located at 980nm, indicating successful progress of aldol condensation, and further, that broad peak of association type hydroxyl group at 3351nm, methylene (-CH2-) peak at 2927nm and its synergic vibration peak appeared at 1436nm, indicating the presence of partially non-dehydrated hydroxylation products in COPTAB-TPA-OH.

Experimental example 2: solid 13C NMR spectrum analysis

The superconducting NMR spectrometer model Infinityllus-400 was used to analyze the novel dual fluorescence emission COPTAB-TPA-OH material prepared in example 1 of the present invention, and the results are shown in FIG. 5, from the 13C NMR spectrum of COPTAB-TPA-OH, the peak corresponding to C ═ O is 185ppm of 170-. In the 13C nuclear magnetic spectrum of the product COPTAB-TPA-0 of full dehydration, no characteristic peak of hydroxyl group is obvious, and 30-50ppm corresponds to C-H vibration of part C ═ C opening addition polymerization of the product COPTAB-TPA-0 of full dehydration in synthesis.

Experimental example 3: analysis by scanning Electron microscope

The scanning electron microscope with the model number of SU3500 is used for analyzing the novel dual fluorescence emission COPTAB-TPA-OH material prepared in the embodiment 1 of the invention, and the result is shown in figure 6, and it can be seen from the figure that the morphology of COPTAB-TPA-OH is gradually changed into a sphere from the initial fiber shape to about 500nm almost completely after 18h along with the increase of the reaction time, and the morphology is not changed any more after continuous heating.

Experimental example 4: liquid fluorescence spectroscopy

The novel dual fluorescent emission COPTAB-TPA-OH material prepared in example 1 of the present invention was analyzed using a liquid fluorescence spectrometer of model RF-5301pc, and the results are shown in fig. 7A, and as can be seen from fig. 7, comparative COPTAB-TPA-0 showed only a single fluorescent emission corresponding to monomeric terephthalaldehyde, whereas COPTAB-TPA-OH material had dual fluorescent emissions of 475nm and 610nm due to the presence of two structures (fully dehydrated double bond structure and dehydrated hydroxylated structure).

Experimental example 5: solid state fluorescence spectroscopy

The results of the novel dual fluorescence emission COPTAB-TPA-OH material prepared in example 1 of the present invention, analyzed by a solid fluorescence spectrophotometer model QM/TM/NIR are shown in fig. 7B, from which it can be seen that COPTAB-TPA-OH also exhibits dual fluorescence emission, which has a certain red shift relative to the liquid spectrum, wavelengths of 520nm and 630nm, wherein the emission at 520nm has aggregation-induced quenching due to the higher conjugation degree of the fully dehydrated structure, and the fluorescence intensity is low. FIG. 8 is a schematic diagram showing that COPTAB-TPA-OH is dispersed in DMF and the color is changed with the irradiation of ultraviolet light, and FIG. 9A is a solid fluorescence spectrum corresponding to the color in FIG. 8, wherein the emission at 630nm undergoes photobleaching under the irradiation of ultraviolet light, the fluorescence intensity is gradually reduced, and the fluorescence at 520nm shows fluorescence enhancement due to the addition polymerization reaction caused by the opening of carbon-carbon double bonds in a fully dehydrated structure, and the pi effect between rigid planes is weakened. Fig. 9B is a schematic diagram of coordinates of corresponding colors.

Experimental example 6: analysis of COPTAB-TPA-OH potential in conjunction with preparation of WLED lamps

Referring to fig. 10, the results of the description of the novel dual fluorescent emission COPTAB-TPA-OH material prepared in example 1 of the present invention are shown in fig. 10, fig. 10A is a schematic view of a commercial violet bead after application of the COPTAB-TPA-OH material and before application, and fig. 10B is a schematic view of the bead corresponding to fig. 10A after connection of a power supply.

Experimental example 7: analysis of COPTAB-TPA-OH application potential in combination with information encryption

Referring to fig. 11, taking the novel dual fluorescence emission COP material prepared in example 1 of the present invention as an example, fig. 11A is a yellow and gray colored notepaper after characters are written on, and fig. 11B is a schematic view under ultraviolet light corresponding to fig. 11A.

Example 2:

the synthesis method and the steps of the novel double-fluorescence emission COPTAB-BPDA-OH material are the same as the embodiment. The difference lies in that: 123.9mg of monomeric 1,3,5 triacetylbenzene and 189.1mg of monomeric biphenyldicarboxaldehyde were dissolved in 12ml of a mixed solvent of ethanol and 1, 4-dioxane.

The novel double-fluorescence emission COPTAB-BPDA-OH material is applied to information encryption:

the COPTAB-BPDA-OH material with double fluorescence emission is dispersed in organic solvent isopropanol (wherein DMF is corrosive and can corrode instruments), the concentration of the dispersion liquid is about 5mg/ml, the dispersion liquid is used as fluorescent ink, ink is sucked into a pen bag by a pen, characters are lightly written on grey-white notepaper, the characters cannot be distinguished under natural light after the organic solvent is volatilized, and the characters are displayed under ultraviolet light irradiation, so that information encryption is realized.

Secondly, the structure and performance of the novel dual fluorescence emission COPTAB-BPDA-OH material prepared by the invention are explained in detail in the following with the attached drawings

Experimental example 1: infrared spectroscopic analysis

The novel dual fluorescence emission COPTAB-BPDA-OH material prepared in example 2 of the present invention was analyzed by fourier infrared spectroscopy of type tencor II, and as a result, as shown in fig. 13, it can be seen from fig. 13 that the target product COPTAB-BPDA-OH material and the control COPTAB-BPDA-0 fully dehydrated under dilute alkali conditions both retained the characteristic peaks of C ═ O from the monomer 1,3,5 triacetylbenzene, appeared at 1663nm and 1682nm, respectively, new characteristic peaks ascribed to C ═ C at 1571nm and 1599nm, respectively, and the control fully dehydrated COPTAB-BPDA-0 observed more distinct trans C ═ C peak than COPTAB-BPDA-OH material, was located at 982nm, indicating successful progress of aldol condensation, and in addition, the broad peak of associated hydroxyl group at 3368nm, the methylene group at 2926nm (-CH2-) and the synergic peak thereof appeared at 1436nm, indicating the presence of partially non-dehydrated hydroxylation products in the COP.

Experimental example 2: analysis by scanning Electron microscope

The novel dual fluorescence emission COPTAB-BPDA-OH material prepared in example 2 of the present invention was analyzed by scanning electron microscopy with the model number SU3500, and the results are shown in fig. 14, where the COPTAB-BPDA-OH material is in the form of a block of about 800 nm.

Experimental example 3: liquid fluorescence spectroscopy

The novel dual fluorescence emission COPTAB-BPDA-OH material prepared in example 2 of the present invention was analyzed by a liquid fluorescence spectrometer of type RF-5301pc, and the results are shown in fig. 15, from which it can be seen that COPTAB-BPDA-0, a fully dehydrated product, showed only a single fluorescence emission, whereas COPTAB-BPDA-OH material, due to the presence of two structures (fully dehydrated double bond structure and dehydrated hydroxylated structure), had dual fluorescence emission at 480nm and 595 nm.

Experimental example 4: solid state fluorescence spectroscopy

The results of analyzing the novel dual fluorescence emission COPTAB-BPDA-OH material prepared in example 2 of the present invention by using a solid fluorescence spectrophotometer with model number QM/TM/NIR are shown in FIGS. 16 and 17, and it can be seen from the figure that COPTAB-BPDA-OH also shows dual fluorescence emission, has a certain red shift relative to the liquid spectrum, and has wavelengths of 530nm and 615nm, wherein the emission at 530nm has aggregation induced quenching due to the higher conjugation degree of the fully dehydrated structure, and the fluorescence intensity is low. FIG. 17 is a solid state fluorescence spectrum of COPTAB-BPDA-0 with only a single fluorescence emission.

Experimental example 5: analyzing the application potential of COPTAB-BPDA-OH by combining information encryption

Referring to fig. 18, a description is given by taking the novel dual fluorescence emission COPTAB-BPDA-OH material prepared in example 2 of the present invention as an example, fig. 18A and 18B are schematic diagrams of a pen nib with COP-isopropyl alcohol as fluorescent ink drawn into the pen nib under ultraviolet light and natural light, respectively, fig. 18C is a gray white note paper after writing, and fig. 18D is a corresponding schematic diagram of fig. 18C under ultraviolet light.

In the experiment, organic solvents such as absolute ethyl alcohol, 1, 4-dioxane, DMF, isopropanol and the like are purchased from Tianjin Corncoded reagent company, 1,3, 5-triacetylbenzene is purchased from Shanghai Bigdi medicine science and technology company, terephthalaldehyde is purchased from Tianjin Shanghai sub-technology development company, sodium hydroxide is purchased from Beijing YinuoKai science and technology company, and commercial violet LED lamps are purchased from Quanzhou Miao trade company.

Example 3:

the synthesis method and the steps of the novel double-fluorescence-emission COPDAB-TFB-OH material are the same as those of the example 1, and the difference is that: 97.2mg of monomer p-diacetylbenzene and 97.2mg of monomer mesitylene are dissolved in 12ml of a mixed solvent of ethanol and 1, 4-dioxane.

Comparative example:

compared with the invention, the invention has double fluorescence emission, the highest point of emission intensity is 475nm and 610nm, the wavelength range almost covers the whole visible light region, which is beneficial to preparing WLED lamp with high quality, the synthesis time of the invention is shorter, the solid fluorescence quantum yield can reach 9.84%, and the liquid quantum yield can reach 21.2%.

Table 1 comparison of the effects of example 1 and comparative example

The preparation principle of the COPs material with double fluorescence emission provided by the invention is as follows:

most of organic polymer fluorescent materials are conjugated polymers, have rigid plane structures and large pi-bond conjugated systems, wherein diphenyl alkene compounds, diphenyl alkyne compounds, azo compounds, schiff base compounds and diphenyl ketene compounds are taken as representatives, and unsaturated bonds C ═ C, C ≡ C, N ≡ N, C ≡ N and C ═ O are conjugated with aromatic rings to construct the diphenyl ketene fluorescent materials. The dual fluorescence emission can be achieved by two methods (1) compounding two substances with different fluorescence emission, (2) a certain unit in the polymer has tautomerism, so that the polymer has two configurations to achieve dual fluorescence emission, and the dual fluorescence emission is achieved by adjusting the concentration of the catalyst and controlling the type of the reaction product.

The method takes sodium hydroxide as a catalyst, and 1,3,5 triacetylbenzene and terephthalaldehyde or biphenyldicarboxaldehyde are subjected to aldol condensation reaction under an alkaline condition to form a network polymer with a conjugated system, wherein when the concentration of the catalyst in the reaction system is 0.05mol/L, a reaction product is a fully dehydrated polymer with carbon-carbon double bonds connected, and the reaction product mainly shows 495nm single fluorescence emission corresponding to the fluorescence property of a monomer in DMF and is used as a reference substance of double fluorescence emission COP (coefficient of performance), namely COP-0; when the concentration of a catalyst in a reaction system is 0.15mol/L, the aldol condensation reaction cannot be completely carried out under a concentrated alkali environment, part of a reaction product is an undehydrated hydroxylated polymer, and the product shows about 475nm (475 nm in DMF and 520nm in solid state) of fluorescence emission, and in addition, another two fluorescence emissions appear at about 610nm (610 nm in DMF and 630nm in solid state) due to the existence of a new structure, namely a hydroxylated structure, so that the COPs material with double fluorescence emission is obtained.

The application principle of the double fluorescence emission COPs material in White Light Emitting Diode (WLED) and information encryption:

(1) the LED has the advantages of energy saving, environmental protection, long life, fast response, etc., wherein the white light LED is regarded as the most promising new light source in the 21 st century after fluorescent lamp as the second generation solid-state lighting source, and there are three main principles for designing the WLED based on "LED + phosphor powder": (1) according to the principle of complementary color mixing, the method is mature at present, but the quality of the obtained LED is poor and the color temperature is high due to the fact that monochromatic yellow fluorescence lacks a red light wave band; (2) compounding green and red fluorescent powder by adopting a blue light LED (450nm-470nm) chip; (3) the red, green and blue fluorescent powder is directly mixed and adjusted to be white fluorescent powder, the white fluorescent powder is combined with a purple light LED (370nm-410nm), white light emission of the fluorescent powder is directly obtained under the excitation of purple light, and the purple light does not participate in the composition of the white light. The dual fluorescence emission wavelengths 475nm and 610nm obtained in the solution respectively correspond to blue light and yellow light of a visible light region, the dual fluorescence emission wavelengths belong to complementary colors, and the solid emission wavelengths are 520nm and 630 nm. And the emission spectrum bandwidth covers almost the whole visible light region (410nm-760nm), so that white light emission can be obtained if the intensity ratio of the two emission wavelengths can be properly adjusted. According to the experiment, the COPs material with double fluorescence emission is dispersed in an organic solvent DMF, and is irradiated under an ultraviolet lamp for a period of time, during which the fluorescence emitted by the solid at 630nm shows photobleaching, the fluorescence intensity is reduced, and the fluorescence at 520nm shows fluorescence enhancement by weakening the pi-pi action between rigid planes because of the addition polymerization reaction caused by opening of carbon-carbon double bonds in a fully dehydrated structure, so that the solid fluorescence intensity ratio of 520nm to 630nm can be adjusted by controlling the ultraviolet irradiation time, white light emission is obtained after about 5-8 days, a solid fluorescence spectrophotometer is used for detection, and after white light is detected, the obtained COPs material with white light emission is coated and covered on a purple light LED, and the preparation of WLED is realized.

(2) Application principle of information encryption potential: the principle of utilizing fluorescent powder to encrypt information is that the fluorescent powder is light yellow in color under natural light and emits strong orange fluorescent light under the irradiation of ultraviolet light, so that the fluorescent powder can be dispersed in organic solvent isopropanol as fluorescent ink, the concentration is 5mg/ml, and the fluorescent ink is coated on notepaper with similar color or darker color, and the application of information encryption which is difficult to identify under natural light and appears under the irradiation of ultraviolet light can be realized.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. An organic fluorescent material, characterized in that: forming a covalent organic polymer with a conjugated system by an aldol condensation reaction of a ketone compound and an aldehyde compound under an alkaline condition;

the ketone compound is one of C2 symmetrical acetyl or C3 symmetrical acetyl aromatic ketone, the aldehyde compound is one of C2 symmetrical formyl or C3 symmetrical formyl aromatic aldehyde, and the structures of the aromatic ketone monomer and the aromatic aldehyde monomer are as follows:

ketone monomers

Aldehyde monomer

Wherein the content of the first and second substances,

is one of benzene, biphenyl and 1,3, 5-triphenylbenzene;

the synthesis method of the organic fluorescent material comprises the following steps:

s1, dissolving the aromatic ketone and the aromatic aldehyde in the organic solvent to be uniformly dispersed to form a mixture a;

s4, drying the product washed in the step S3 at 55-65 ℃ for 4-6 hours to obtain the organic fluorescent material with double fluorescence emission;

in step S2, the catalyst is one of aqueous solutions of sodium hydroxide, potassium hydroxide, cesium carbonate, and potassium tert-butoxide, or one of alcoholic solutions of sodium hydroxide, potassium hydroxide, cesium carbonate, and potassium tert-butoxide, the concentration of the aqueous solution of the catalyst is 1 to 6mol/L, and the concentration of the alcoholic solution of the catalyst is 0.5 to 1.5 mol/L.

2. An organic fluorescent material according to claim 1, wherein: the fluorescence emission range of the organic fluorescent material is 410-750nm, and double fluorescence phenomena are shown at 475nm and 610 nm.

3. The organic fluorescent material of claim 1, wherein: in step S1, the aromatic ketone is one of 1,3,5 triacetylbenzene, p-diacetylbenzene, 4' -diacetylbiphenyl, and 1,3, 5-tris (4-acetylphenyl) benzene;

4. The organic fluorescent material of claim 1, wherein: in step S1, the organic solvent is one or more of absolute ethyl alcohol, 1, 4-dioxane, n-butanol, dichloromethane, toluene, o-dichlorobenzene, or dimethyl sulfoxide.

5. The organic fluorescent material of claim 1, wherein: in step S1, the organic solvent is a mixed solvent of ethanol and 1, 4-dioxane, and the volume ratio of ethanol to 1, 4-dioxane is 1: 1.

6. Use of the organic fluorescent material prepared according to any one of claims 1 to 5 in WLED.

7. Use of the organic fluorescent material prepared according to any one of claims 1 to 5 for information encryption.