Stimuli-responsive fluorescent film and preparation method thereof

Abstract

This invention discloses a stimulus-responsive fluorescent thin film and its preparation method, belonging to the field of fluorescent materials. The fluorescent thin film includes components capable of emitting red, green, and blue primary colors of fluorescence. The red and green fluorescent components contain rare earth ion complexes, and the blue fluorescent component contains tetraphenylethylene (TPE) complexes. The preparation method involves uniformly mixing the rare earth ion complexes and TPE complexes in an aqueous solution, adding a cationic surfactant to fully precipitate the mixture, centrifuging the precipitate particles, and compacting them at room temperature to spontaneously form a self-supporting fluorescent thin film. Adjusting the proportions of each component yields fluorescent thin films with different emission colors. The preparation method is green, environmentally friendly, and simple, which is conducive to industrial production. The fluorescent thin film has good mechanical properties and stimulus responsiveness, and can be used for acid gas detection, showing promise for playing an important role in environmental monitoring and chemical sensing.

Description

Technical Field

[0001] This invention relates to a stimulus-responsive fluorescent thin film and its preparation method, belonging to the field of fluorescent materials. Background Technology

[0002] In recent years, stimulus-responsive fluorescent materials, especially highly sensitive white fluorescent materials, have attracted widespread attention. Through ingenious molecular design, stimulus-responsive fluorescent materials can exhibit significant changes in fluorescence color or intensity under specific conditions such as different temperatures, humidity levels, acids and alkalis, metal ions, and chemical gases. Among them, thin-film-based stimulus-responsive fluorescent materials, due to their advantages such as light weight and ease of device fabrication, have significant application prospects in fields such as chemical sensing and intelligent detection.

[0003] White fluorescent films are typically composed of a homogeneous mixture of red, green, and blue fluorescent components in a specific ratio. A change in the fluorescence of any one component will cause a significant change in the film's fluorescence color, thus exhibiting extremely high sensitivity. Currently, reported white fluorescent films are often produced through layer-by-layer self-assembly or solution casting. Layer-by-layer self-assembly utilizes weak intermolecular interactions (such as electrostatic interactions, hydrogen bonding, coordination interactions, etc.) to spontaneously adsorb fluorescent components onto a solid substrate layer by layer through alternating deposition. This process is cumbersome, inefficient, and unsuitable for large-scale industrial production. Furthermore, the resulting films lack self-support, and their mechanical properties depend on the substrate used. Solution casting is a common film-forming method with a relatively simple process. Due to the thorough mixing of raw materials in the solution, highly uniform film materials can be prepared through casting. However, solution casting usually requires the evaporation of large amounts of organic solvents, resulting in significant pollution and high energy consumption, failing to meet the requirements of green chemistry and sustainable development.

[0004] Therefore, there is an urgent need to develop a green, environmentally friendly, and simple method for preparing thin film materials that is conducive to industrial production, so as to achieve the large-scale preparation of highly uniform and self-supporting fluorescent thin films under mild conditions. Summary of the Invention

[0005] In view of the above-mentioned shortcomings in the existing technology, the purpose of this invention is to provide a green, environmentally friendly, simple process that is conducive to industrial production of fluorescent thin films, which can prepare highly uniform and self-supporting fluorescent thin films under mild conditions; and to achieve the detection of acidic gases by designing a stimulus-responsive white fluorescent thin film.

[0006] To achieve the above objectives, the present invention provides the following technical solution: the coordination center ions of the red and green fluorescent rare earth ion complexes of the present invention are Eu and... 3+ and Tb 3+Its ligands have the structural formula shown in L1; the coordination center ion of the blue fluorescent TPE complex is a multivalent metal ion, preferably a divalent metal ion, and more preferably Mg. 2+ Ca 2+ Ni 2+ Cu 2+ Zn 2+ Its ligands have the structure shown in L2.

[0007] ;

[0008] Where n = 1 - 10, m = 1 - 10.

[0009] A method for preparing a stimulus-responsive fluorescent thin film includes the following steps: Step 1: Prepare complex solutions of red, green, and blue primary color fluorescence respectively; Step 2: Uniformly mix the red, green, and blue primary color fluorescent complexes from Step 1; Step 3: Add cationic surfactant solution, mix thoroughly, and then separate the precipitate; Step 4: Compact the precipitate to obtain a uniform, continuous, self-supporting transparent film.

[0010] The preferred technical solution is as follows: In step 1, the complex solution is preferably an aqueous solution, the molar ratio of metal ions to ligands in red and green fluorescent complexes is preferably 2:3, the molar ratio of divalent metal ions to ligands in blue fluorescent complexes is preferably 1:1, and the metal ion concentration is preferably 0.1-10 mM.

[0011] The preferred technical solution is as follows: In step 2, the proportions of the red, green and blue primary color fluorescent complexes are adjusted to obtain fluorescent films with different emission colors. The preferred molar ratio of the three is 3:1:0.06-3:1:0.18, and the more preferred ratio is 3:1:0.12, which can yield a film that emits white fluorescence under 254 nm ultraviolet light excitation.

[0012] The preferred technical solution is as follows: In step 3, the cationic surfactant solution is preferably an aqueous solution, and the type is preferably an amine salt type, quaternary ammonium salt type, or heterocyclic surfactant containing an alkyl chain. The preferred ratio is that the net charge of the coordination center of the complex is equal to the positive charge of the cation.

[0013] The preferred technical solution is as follows: In step 4, the film pressing process of precipitation compaction is carried out at room temperature, and the required pressure is mild, preferably by finger pressure and roller pressure; that is, the film pressing process is preferably carried out at room temperature, small area films are preferably pressed by finger pressure, and large area films are preferably pressed by automated roller pressure.

[0014] The preparation method described in this invention is mild, environmentally friendly, and simple, which is conducive to industrial production.

[0015] The present invention has the following beneficial effects: (1) The fluorescent thin film preparation method of the present invention is green and environmentally friendly, and the process is simple. It is conducive to industrial production and can prepare highly uniform and self-supporting fluorescent thin films under mild conditions.

[0016] (2) The composite film preparation method described in this invention can be used to obtain fluorescent films with tunable full-spectrum colors, including white fluorescent films with high sensitivity.

[0017] (3) The fluorescent thin film prepared by the method described in this invention has good mechanical properties, is easy to device, and can undergo observable and significant fluorescence changes under acidic gas stimulation, and has good application prospects in environmental monitoring and chemical sensing. Attached Figure Description

[0018] Figure 1 The fluorescence spectrum of the red fluorescent film described in Example 1 under 254 nm ultraviolet light excitation is shown. Figure 2 The fluorescence spectrum of the orange fluorescent film described in Example 2 under 254 nm ultraviolet light excitation; Figure 3 The fluorescence spectrum of the white fluorescent film described in Example 3 under 254 nm ultraviolet light excitation; Figure 4 The tensile stress-strain curve of the white fluorescent film described in Example 3; Figure 5 The fluorescence spectrum of the white fluorescent film described in Example 3 after being placed in an HCl atmosphere for 3 min and then in an NH3 atmosphere for 1 min is obtained under 254 nm ultraviolet light excitation. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments and accompanying drawings, so that the purpose, technical solution and effects of the present invention will be clearer.

[0020] The specific embodiments of the present invention are as follows: A stimulus-responsive fluorescent thin film and its preparation method Example 1: Red fluorescent film This embodiment provides a method for preparing a red fluorescent thin film, the specific steps of which are as follows: Take 0.3380 g of chebulic acid bis-headed ligand L1 (n=4) potassium salt (abbreviated as L1 potassium salt) (see literature: Angew. Chem. Int. Ed. 2008, 1200.1487 g Eu(NO3)3·6H2O and 0.3645 g hexadecyltrimethylammonium bromide (CTAB) were dissolved in 50 mL of ultrapure water. The resulting L1 potassium salt solution and europium nitrate solution were uniformly mixed to obtain a red fluorescent complex solution. Then, CTAB solution was added, mixed thoroughly, and allowed to stand for 5-10 min. The mixture was then centrifuged. The resulting precipitate was transferred to a clean glass plate, covered with a clean polytetrafluoroethylene (PTFE) plate, and the PTFE plate was pressed firmly with a finger to squeeze out excess water. The PTFE plate was removed, and the precipitate was allowed to stand naturally for 5-15 min, gradually transforming into a uniform and continuous film. The film was then peeled off from the glass plate to obtain a self-supporting transparent film, which exhibited red fluorescence under a 254 nm UV lamp. The film pressing process was carried out at room temperature with a gentle pressure, preferably applied by finger pressure.

[0021] The emission spectrum of the red fluorescent film described in this embodiment under 254 nm ultraviolet light excitation is as follows: Figure 1 As shown, the emission spectrum exhibits Eu 3+ Characteristic emission wavelength (Eu) 3+ 595nm 5 D0→ 7 F1; 616nm, 5 D0→ 7 F2; 694nm 5 D0→ 7 F4), CIE coordinates are (0.5093, 0.2987).

[0022] Example 2 Orange fluorescent film The preparation method of the fluorescent thin film in this embodiment is the same as that in Example 1, except that Tb(NO3)3 is used to partially replace Eu(NO3)3, with a molar ratio of Eu... 3+ :Tb 3+ =3:1, the specific steps are as follows: Take 0.3380 g of chebulic acid bis-headed ligand L1 (n=4) potassium salt (abbreviated as L1 potassium salt) (see literature: Angew. Chem. Int. Ed. 2008, 1200.1115 g Eu(NO3)3·6H2O, 0.0378 g Tb(NO3)3·6H2O, and 0.3645 g cetyltrimethylammonium bromide (CTAB) were dissolved in 50 mL of ultrapure water. The resulting L1 potassium salt solution and europium nitrate-terbium nitrate solution were uniformly mixed to obtain an orange fluorescent complex solution. Then, CTAB solution was added, mixed thoroughly, and allowed to stand for 5-10 min, followed by centrifugation. The resulting precipitate was transferred to a clean glass plate, covered with a clean polytetrafluoroethylene (PTFE) plate, and the PTFE plate was pressed firmly to squeeze out excess water. The PTFE plate was removed, and the precipitate was allowed to stand naturally for 5-15 min, gradually transforming into a uniform and continuous film. The film was then peeled off from the glass plate to obtain a self-supporting transparent film, which exhibited orange fluorescence under a 254 nm UV lamp. The film pressing process was carried out at room temperature with gentle pressure, preferably applied by finger pressure.

[0023] The emission spectrum of the orange fluorescent film described in this embodiment under 254 nm ultraviolet light excitation is as follows: Figure 2 As shown, the emission spectrum exhibits Eu 3+ and Tb 3+ Characteristic emission wavelength (Eu) 3+ 595nm 5 D0→ 7 F1; 616nm, 5 D0→ 7 F2; 694nm 5 D0→ 7 F4; Tb 3+ 495nm 5 D4→ 7 F6; 544nm 5 D4→ 7 F5), CIE coordinates are (0.4112, 0.3903).

[0024] Example 3 White fluorescent film The preparation method of the fluorescent thin film in this embodiment is the same as that in Example 2, except that a certain amount of TPE complex L2-Ni is added. 2+ The molar ratio is Eu 3+ :Tb 3+： TPE=3:1:0.12, the specific steps are as follows: Take 0.3380 g of chebulic acid bis-headed ligand L1 (n=4) potassium salt (abbreviated as L1 potassium salt) (see literature: Angew. Chem. Int. Ed. 2008, 120, 4260 - 4263), 0.1115 g Eu(NO3)3·6H2O-0.0378 g Tb(NO3)3·6H2O, 0.0120 g tetraphenylethylene chebulic acid bis-headed ligand L2 (m=4) potassium salt (abbreviated as L2 potassium salt) (see literature: J. Am. Chem. Soc. 2014, 136 0.0029 g Ni(NO3)2·6H2O and 0.3718 g hexadecyltrimethylammonium bromide (CTAB) were dissolved in 50 mL of ultrapure water, respectively. The resulting L1 potassium salt solution and europium nitrate-terbium nitrate solution, and L2 potassium salt solution and nickel nitrate solution were mixed uniformly to obtain orange and blue fluorescent complex solutions, respectively. The two complex solutions were then mixed, and CTAB solution was added. The mixture was thoroughly mixed, allowed to stand for 5-10 min, and centrifuged. The resulting precipitate was transferred to a clean glass plate, covered with a clean polytetrafluoroethylene (PTFE) plate, and the PTFE plate was pressed firmly to squeeze out excess water. The PTFE plate was removed, and the precipitate was allowed to stand naturally for 5-15 min, gradually transforming into a uniform and continuous film. The film was then peeled off from the glass plate to obtain a self-supporting transparent film, which exhibited white fluorescence under a 254 nm UV lamp. The film pressing process was carried out at room temperature with gentle pressure, preferably applied by finger pressure.

[0025] The emission spectrum of the white fluorescent film described in this embodiment under 254 nm ultraviolet light excitation is as follows: Figure 3 As shown, the emission spectrum exhibits Eu 3+ and Tb 3+ Characteristic emission wavelength (Eu) 3+ 595nm 5 D0→ 7 F1; 616nm, 5 D0→ 7 F2; 694nm 5 D0→ 7 F4; Tb 3+ 495nm 5 D4→ 7 F6; 544nm 5 D4→ 7 F5), and the characteristic bands of TPE (420 nm-550 nm), with CIE coordinates of (0.3332, 0.3342).

[0026] The stress-strain curve of the white fluorescent film described in this embodiment is as follows: Figure 4 As shown, the tensile breaking strength is 1.73 MPa, the tensile breaking strain is 16.7%, and the Young's modulus is 22.8 MPa.

[0027] The white fluorescent film described in this embodiment exhibits a stimulating response to acidic gases. The fluorescence spectra of the film under 254 nm ultraviolet light excitation in different atmospheres are as follows: Figure 5 As shown, in an acidic HCl atmosphere, the film fluorescence is significantly weakened, and the CIE coordinates change to (0.1923, 0.2154), showing a weak blue emission; in an alkaline NH3 atmosphere, the film fluorescence recovers, and the CIE coordinates change to (0.3417, 0.3525), showing a stronger white emission.

[0028] Therefore, the white fluorescent film described in this embodiment has good mechanical properties, is easy to device, and can undergo observable and significant fluorescence changes under acidic gas stimulation, showing good application prospects in environmental monitoring and chemical sensing.

[0029] The specific embodiments of the present invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A stimulus-responsive fluorescent thin film, characterized in that, This includes rare-earth ion complexes capable of emitting red and green fluorescence, tetraphenylethylene (TPE) complexes capable of emitting blue fluorescence, and cationic surfactants; among which: The coordination center ions of the rare earth ion complexes capable of emitting red and green fluorescence are Eu and... 3+ and Tb 3+ Its ligand is L1, and the structure of L1 is shown below: ； Where n = 1 - 10; The coordination center ion of the TPE complex capable of emitting blue fluorescence is a divalent metal ion Ni. 2+ Its ligand is L2, and the structure of L2 is shown below: ； Where m = 1 - 10; The cationic surfactant is a quaternary ammonium salt surfactant containing an alkyl chain; The fluorescent film is a uniform, continuous, self-supporting transparent film; the film contains Eu 3 +:Tb 3+ The molar ratio of TPE is 3:1:0.06-3:1:0.18; the molar ratio of metal ions to ligands in the red and green fluorescent complexes is 2:3, and the molar ratio of divalent metal ions to ligands in the blue fluorescent complex is 1:

1.

2. The stimulus-responsive fluorescent film according to claim 1, characterized in that, The fluorescent film is stimulating to acidic gases.

3. The stimulus-responsive fluorescent film according to claim 2, characterized in that, In an acidic HCl atmosphere, the fluorescence of the fluorescent film is significantly reduced, and the CIE coordinates become (0.1923, 0.2154), showing a weak blue emission; in an alkaline NH3 atmosphere, the fluorescence of the film recovers, and the CIE coordinates become (0.3417, 0.3525), showing a stronger white emission.

4. A method for preparing a stimulus-responsive fluorescent thin film according to claim 1, characterized in that, Includes the following steps: Step 1: Prepare complex solutions of red, green, and blue primary color fluorescence respectively; Step 2: Uniformly mix the red, green, and blue primary color fluorescent complexes from Step 1; Step 3: Add cationic surfactant, mix thoroughly, and then separate the precipitate; Step 4: Compact the precipitate to obtain a uniform, continuous, self-supporting transparent film.

5. The preparation method according to claim 4, characterized in that, In step 4, the precipitation compaction film pressing process is carried out at room temperature and requires a mild pressure.

6. The preparation method according to claim 5, characterized in that, The pressure is applied by fingers or rollers.

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