Flexible humidity-sensitive photoluminescent fibers, their preparation methods and applications

Abstract

This invention provides a flexible humidity-induced photoluminescent fiber, its preparation method, and its applications, relating to the field of photoluminescent fiber preparation technology. The preparation method includes the following steps: S1, firstly, a 2-aminoterephthalic acid solution is prepared using N,N-dimethylformamide as a solvent; then, a rare earth metal-organic framework precursor is added to obtain a precursor mixture solution; S2, the precursor mixture solution is subjected to ultrasonic treatment; S3, the pretreated fiber is placed in the ultrasonically treated precursor mixture solution for a hydrothermal reaction; S4, after the hydrothermal reaction is completed and the solution is cooled to room temperature, the fiber is removed and subjected to washing, drying, and post-processing to obtain the flexible humidity-induced photoluminescent fiber. The obtained flexible humidity-induced photoluminescent fiber possesses good flexibility, fast response time, excellent stability, and high luminescence brightness, showing promising application prospects in the fields of smart wearables and visual smart fibers.

Description

Technical Field

[0001] This application relates to the field of photoluminescent fiber preparation technology, specifically to a flexible humidity-controlled photoluminescent fiber, its preparation method, and its application. Background Technology

[0002] Photoluminescence is the phenomenon where an object emits light after being irradiated by an external light source, gaining energy and becoming excited. It generally involves three main stages: absorption, energy transfer, and light emission. Both light absorption and emission occur during transitions between energy levels, passing through excited states. Energy transfer, on the other hand, is due to the movement of the excited states. Ultraviolet radiation, visible light, and infrared radiation can all induce photoluminescence, such as phosphorescence and fluorescence.

[0003] Assembling moisture-sensitive fluorescent molecules with polymer networks to create sensing materials is considered an effective method for visually detecting humidity. Fluorescence sensing requires no external microelectronic devices; it detects humidity by detecting changes in the microenvironment polarity induced by external moisture on the fluorescent material, which are then excited by UV light to produce different "visually visible" colors. The combination of humidity-sensitive photoluminescence with fibers significantly expands the application prospects of photoluminescence. Humidity-sensitive photoluminescent fibers, as a novel functional material, have wide applications in sensing, bionics, clothing, and medicine.

[0004] The invention patent with publication number CN107747222A provides a fluorescent organic framework based on electrospinning technology and its preparation method. The method first prepares an amino-rich chitosan / polyethylene oxide nanofiber membrane as a substrate nanofiber membrane via electrospinning. Then, the substrate nanofiber membrane is immersed in an activation solution rich in carboxyl groups. The amino groups of the substrate nanofiber membrane link the carboxyl groups of trimellitic acid in the activation solution, resulting in a carboxyl-rich fiber membrane sample. Finally, a solution is prepared by dissolving hydrated fluorescent metal nitrate and trimellitic acid in ethanol and water. The carboxyl-rich fiber membrane sample is immersed in this solution, and the solution is placed in a sealed container. Triethylamine is injected into the container and allowed to evaporate naturally. Fluorescent metal ions and trimellitic acid ligands begin to assemble on the surface of the carboxyl-rich fibers, growing into a MOF crystal / chitosan composite membrane with uniform fluorescence properties. However, this preparation method requires surface chemical modification technology to impart numerous active groups to the surface of the fiber membrane in order to achieve mutual loading between the fiber membrane and the fluorescent material. This will limit and affect the performance of the fiber membrane itself. In addition, since the fiber membrane is not resistant to high temperature, there is a technical defect that the reaction conditions are limited and can only be prepared under low temperature conditions.

[0005] In view of this, it is necessary to study a flexible humidity-sensitive photoluminescent fiber, its preparation method and application, in order to solve the above-mentioned technical problems. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a flexible humidity-induced photoluminescent fiber, its preparation method and application. Using flexible high-temperature resistant fiber as a substrate, regular rare-earth metal-organic framework particles are hydrothermally grown on its surface to obtain the flexible humidity-induced photoluminescent fiber. This fiber material emits bright blue light under ultraviolet light when exposed to moisture, thus obtaining the humidity-induced photoluminescent fiber. The humidity-induced photoluminescent fiber prepared by this invention has good flexibility, excellent luminescent performance and stability, and has good application prospects in the fields of smart wearables and visual smart fibers.

[0007] In a first aspect, embodiments of this application provide a method for preparing flexible humidity-sensitive photoluminescent fibers, comprising the following steps:

[0008] S1. First, a 2-aminoterephthalic acid solution is prepared using N,N-dimethylformamide as a solvent; then, a rare earth metal-organic framework precursor is added to obtain a mixed precursor solution.

[0009] S2, the precursor mixture solution is subjected to ultrasonic treatment;

[0010] S3, the pretreated high-temperature resistant fiber is placed in the precursor mixture solution after ultrasonic treatment and subjected to hydrothermal reaction, wherein the hydrothermal temperature is 120-180℃ and the reaction time is 24-72h;

[0011] S4. After the hydrothermal reaction is completed and the solution is cooled to room temperature, the high-temperature resistant fiber is taken out and cleaned and dried. Humidity-sensitive photoluminescent organic metal framework particles with a predetermined thickness, predetermined particle size and crystal form are uniformly deposited on the surface of the flexible high-temperature resistant fiber to obtain flexible humidity photoluminescent fiber.

[0012] As a further improvement of the present invention, in the precursor mixed solution in step S1, the concentration of the rare earth metal-organic framework precursor is 0.02-0.06 mol / L; and the concentration of the 2-aminoterephthalic acid solution is 0.01-0.03 mol / L.

[0013] As a further improvement of the present invention, in the precursor mixed solution described in step S1, the molar mass ratio of the rare earth metal-organic framework precursor and 2-aminoterephthalic acid is 2.2:1.1 (2:1).

[0014] As a further improvement of the present invention, the rare earth metal-organic framework precursor is one or a mixture of neodymium nitrate hexahydrate, europium nitrate hexahydrate, terbium nitrate hexahydrate, and thionium nitrate hexahydrate.

[0015] As a further improvement of the present invention, in step S3, the high-temperature resistant fiber is one of carbon fiber, metal-based fiber, polyester fiber, polytetrafluoroethylene fiber, and polyimide fiber.

[0016] As a further improvement of the present invention, in step S3, the specific process of the hydrothermal reaction is as follows: the precursor mixture solution is placed in a hydrothermal reactor, and then the pretreated high-temperature resistant fiber is added, wherein the hydrothermal temperature is 120-150°C and the reaction time is 24-48h.

[0017] As a further improvement of the present invention, in step S2, the ultrasonic treatment process is as follows: the precursor mixture solution is placed in an ice bath at 0-10°C, the ultrasonic time is 10-30 min, and the ultrasonic power is 200-500 W.

[0018] As a further improvement of the present invention, in step S3, the pretreatment process of the high-temperature resistant fiber is as follows: the high-temperature resistant fiber is placed in water and alcohol solutions in sequence for ultrasonic cleaning, and then taken out and dried for later use.

[0019] As a further improvement of the present invention, in step S3, the particle size of the humidity-sensitive photoluminescent organometallic framework particles is 1-2 μm, the crystal form is monoclinic, and the deposition thickness is 2-4 μm.

[0020] Secondly, embodiments of this application provide a flexible humidity-induced photoluminescent fiber, which is prepared using the above-described method for preparing flexible humidity-induced photoluminescent fibers;

[0021] The flexible humidity-sensitive photoluminescent fiber comprises a high-temperature resistant fiber matrix and humidity-sensitive photoluminescent organometallic framework particles uniformly deposited and loaded on the surface of the high-temperature resistant fiber; the humidity-sensitive photoluminescent organometallic framework particles have a particle size of 0.5–2.5 μm, a monoclinic crystal structure, and a deposition thickness of 1–4 μm.

[0022] The flexible humidity-sensitive photoluminescent fiber emits blue fluorescence when stimulated by changes in ambient humidity and is irradiated by ultraviolet light.

[0023] Thirdly, embodiments of this application provide applications of the aforementioned flexible humidity-sensitive photoluminescent fiber. These applications include smart wearable devices, smart anti-counterfeiting technologies, and environmental monitoring.

[0024] The beneficial effects of this invention are:

[0025] 1. The method for preparing flexible humidity-induced photoluminescent fiber provided by the present invention firstly pre-treats the surface of high-temperature resistant fiber to make the fiber surface smooth and clean; then, the pre-treated high-temperature resistant fiber is placed in a mixed solution system containing neodymium nitrate hexahydrate (a rare earth metal-organic framework precursor), 2-aminoterephthalic acid and N,N-dimethylformamide, and the high-temperature resistant fiber is chemically treated using a hydrothermal method. The high-temperature hydrothermal reaction causes the growth and deposition of organometallic framework particles on the fiber surface, forming a dense photoluminescent layer, thus obtaining the humidity-induced photoluminescent fiber; the flexible humidity-induced photoluminescent fiber has good flexibility, excellent color-changing properties and stability. In this mixed solution system, neodymium nitrate hexahydrate, 2-aminoterephthalic acid, and N,N-dimethylformamide can undergo the following reaction process: First, hydrothermal growth of fine linear MOF forms a dense film on the fiber surface, which further forms spherical MOF particles. This allows the present invention to directly achieve stable and uniform deposition and loading of fluorescent organometallic framework particles on a smooth fiber surface, overcoming the technical bias of existing technologies where fiber-shaped substrates cannot stably, firmly, and uniformly deposit and load fluorescent material particles.

[0026] 2. The method for preparing flexible humidity-induced photoluminescent fibers provided by this invention can effectively control the deposition thickness, particle size, and crystal form of organic framework metal particles deposited on the surface of high-temperature resistant fibers by adjusting the molar ratio of precursors and hydrothermal reaction parameters. This results in a tight and stable bond between the organic framework metal particles and the fiber substrate, while significantly enhancing the luminescence performance of the fiber. Consequently, the luminescence brightness and stability of the flexible high-temperature resistant fiber are effectively controlled, giving the resulting flexible humidity-induced photoluminescent fiber good flexibility, fast response time, excellent stability, and high luminescence brightness. It has promising application prospects in the fields of smart wearables and visual smart fibers.

[0027] 3. The method for preparing flexible humidity-sensitive photoluminescent fibers provided by this invention, by controlling the deposition thickness, particle size, and crystal form of the organometallic framework particles, can further effectively regulate the mechanical properties of the fibers while achieving humidity-sensitive photoluminescence. Specifically, it can simultaneously and significantly enhance the tensile properties and flexibility of the fibers. This invention links the flexibility of the fibers with the characteristics of the organometallic framework particles to achieve a synergistic effect.

[0028] 4. The flexible humidity-sensitive photoluminescent fiber provided by this invention can emit blue fluorescence of different intensities under ultraviolet light irradiation as humidity changes. It has obvious luminescence effect, fast luminescence time when wet and good stability. When the humidity reaches 100%, the fiber emits extremely bright blue light under ultraviolet light irradiation. It has good application prospects in the fields of smart wearables and visual smart fibers and has great commercial promotion value.

[0029] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0031] Figure 1 This is a scanning electron microscope image of the carbon fiber substrate used in Example 1 of the present invention, with a scale bar of 5 μm.

[0032] Figure 2 The images are scanning electron microscope (SEM) images of the flexible humidity-sensitive photoluminescent fiber prepared in Example 1 of this invention, with scale bars of 50 μm and 2 μm, respectively.

[0033] Figure 3 Optical photographs of the flexible humidity-sensitive photoluminescent fiber prepared in Example 1 of the present invention emitting light when wet (from left to right, the images show water, DMF, ethanol, DMSO, and pure water as blanks).

[0034] Figure 4 The fluorescence spectrum of the organometallic framework in the flexible humidity photoluminescent fiber prepared in Example 1 of the present invention is shown.

[0035] Figure 5 The image shows a comparison of the luminescence intensity of the flexible humidity-sensitive photoluminescent fiber prepared in Example 1 of this invention under different humidity levels (left side: saturated potassium carbonate solution, relative humidity 43.2%; right side: saturated potassium sulfate solution, relative humidity 97.3%).

[0036] Figure 6 This is a scanning electron microscope image of the flexible humidity-sensitive photoluminescent fiber prepared in Comparative Example 1 of this invention. The scale bar is 50 μm. Detailed Implementation

[0037] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0039] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0040] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0041] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0042] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0043] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0044] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0045] To address the technical challenge of stably and firmly loading fluorescent particles onto fiber surfaces, this application provides a method for preparing flexible humidity-induced photoluminescent fibers. The method involves directly using flexible, high-temperature resistant fibers as a substrate, and hydrothermally growing regularly spaced rare-earth metal-organic framework particles on its surface to obtain flexible humidity-induced photoluminescent fibers. These fibers emit bright blue light under ultraviolet light when exposed to moisture, thus yielding humidity-induced photoluminescent fibers. The specific steps include:

[0046] S1. First, a 2-aminoterephthalic acid solution is prepared using N,N-dimethylformamide as a solvent; then, a rare earth metal-organic framework precursor is added to obtain a mixed precursor solution.

[0047] S2, the precursor mixture solution is subjected to ultrasonic treatment;

[0048] S3, the pretreated high-temperature resistant fiber is placed in the precursor mixture solution after ultrasonic treatment and subjected to hydrothermal reaction, wherein the hydrothermal temperature is 120-180℃ and the reaction time is 24-72h;

[0049] S4. After the hydrothermal reaction is completed and the solution is cooled to room temperature, the high-temperature resistant fiber is taken out and cleaned and dried. Humidity-sensitive photoluminescent organic metal framework particles with a predetermined thickness, predetermined particle size and crystal form are uniformly deposited on the surface of the flexible high-temperature resistant fiber to obtain flexible humidity photoluminescent fiber.

[0050] Preferably, in the precursor mixed solution of step S1, the concentration of the rare earth metal-organic framework precursor is 0.02-0.06 mol / L; and the concentration of the 2-aminoterephthalic acid solution is 0.01-0.03 mol / L.

[0051] Preferably, in the precursor mixed solution described in step S1, the molar mass ratio of the rare earth metal-organic framework precursor to 2-aminoterephthalic acid is 2.2:1.1.

[0052] Preferably, the rare earth metal-organic framework precursor is one or a mixture of neodymium nitrate hexahydrate, europium nitrate hexahydrate, terbium nitrate hexahydrate, and thionium nitrate hexahydrate.

[0053] Preferably, in step S3, the high-temperature resistant fiber is one of carbon fiber, metal-based fiber, polyester fiber, polytetrafluoroethylene fiber, and polyimide fiber.

[0054] Preferably, in step S3, the specific process of the hydrothermal reaction is as follows: the precursor mixture solution is placed in a hydrothermal reactor, and then the pretreated high-temperature resistant fiber is added, wherein the hydrothermal temperature is 120-150°C and the reaction time is 24-48h.

[0055] Preferably, in step S2, the ultrasonic treatment process is as follows: the precursor mixture solution is placed in an ice bath at 0-10°C, the ultrasonic time is 10-30 min, and the ultrasonic power is 200-500 W.

[0056] Preferably, in step S3, the pretreatment process of the high-temperature resistant fiber is as follows: the high-temperature resistant fiber is placed in water and alcohol solutions in sequence for ultrasonic cleaning, and then taken out and dried for later use.

[0057] The preparation method of the flexible humidity-sensitive photoluminescent fiber provided by the present invention will be described below with reference to specific embodiments.

[0058] Example 1

[0059] Embodiment 1 of the present invention provides a method for preparing flexible humidity-induced photoluminescent fibers, comprising the following steps:

[0060] S1. Add 0.2 mmol of 2-aminoterephthalic acid to 20 mL of N,N-dimethylformamide solvent to prepare a 0.01 mol / L 2-aminoterephthalic acid solution; then take 0.4 mmol of neodymium nitrate hexahydrate and add it to the 0.01 mol / L 2-aminoterephthalic acid solution to obtain a mixed solution of neodymium nitrate hexahydrate, 2-aminoterephthalic acid and N,N-dimethylformamide precursors.

[0061] S2. Place the precursor mixture of neodymium nitrate hexahydrate, 2-aminoterephthalic acid and N,N-dimethylformamide described in step S1 into a cell disruptor and sonicate it at 300W power for 30 minutes in an ice bath at 2°C for use.

[0062] S3. The carbon fibers (with an average fiber diameter of about 5 μm) were sequentially placed in deionized water and ethanol for ultrasonic cleaning for 15 min, dried and stored for later use; the precursor mixture solution containing neodymium nitrate hexahydrate, 2-aminoterephthalic acid and N,N-dimethylformamide that was ultrasonically treated in step S2 was transferred to a 100 mL polytetrafluoroethylene liner, and then the cleaned carbon fibers were placed in the aforementioned precursor mixture solution and hydrothermally reacted at 120 °C for 48 h;

[0063] In this mixed solution system, neodymium nitrate hexahydrate, 2-aminoterephthalic acid, and N,N-dimethylformamide can undergo the following reaction process: Under hydrothermal conditions, MOFs first grow uniformly on the fiber surface in the form of fine lines. After the bonding force between MOFs and fibers increases and a dense film is formed, the interaction between MOFs causes the fine-line MOFs to further combine into spherical shapes to increase the amount of MOFs deposited. Through the two morphological changes of MOFs, this invention enables the stable and uniform deposition and loading of fluorescent organometallic framework particles directly on the smooth fiber surface.

[0064] S4. After the hydrothermal reaction is completed and the solution is cooled to room temperature, the composite fiber is taken out, cleaned with DMF and ethanol in sequence, and dried to obtain flexible humidity photoluminescent fiber; and the precipitate is collected for later use.

[0065] Please see Figures 1 to 2 As shown, from Figure 1 As can be seen, the surface of the carbon fiber substrate is smooth when untreated. From... Figure 2 As can be seen, after the hydrothermal reaction, a thick layer of Nd-MOF spherical particles with a diameter of about 1 to 2 μm was densely deposited on the surface of the carbon fiber.

[0066] The Nd-MOF spherical particles have a monoclinic crystal system (where each europium ion adopts a nine-coordinate mode to form a 2D network structure, which promotes the loading of MOF on the fiber, and the loading effect of this crystal is significantly better than other conventional crystals), and the deposition thickness is 3 μm.

[0067] The flexible humidity-sensitive photoluminescent fiber prepared in Example 1 exhibits good flexibility and mechanical properties. In particular, its mechanical properties are superior to those of pure carbon fiber.

[0068] Please see Figure 3 As shown, the humidity-sensitive photoluminescent fiber prepared in Example 1 of the present invention only emits bright blue fluorescence when it comes into contact with water.

[0069] Please see Figure 4 As shown, the humidity-induced photoluminescent fiber prepared in Example 1 of the present invention achieves maximum fluorescence intensity in the visible light band when the excitation wavelength is in the range of 320-360nm.

[0070] Please refer to Figure 5 As shown, the prepared photoluminescent fiber emits blue fluorescence of varying brightness with changes in humidity. When the humidity is low, the blue fluorescence emitted by the fiber is weaker, while when the humidity is high, the fiber emits stronger blue fluorescence.

[0071] Comparative Example 1

[0072] Comparative Example 1 provides a method for preparing flexible humidity-induced photoluminescent fibers. The difference from Example 1 is that in step S1, the carbon fibers are not pretreated on the surface. The rest is roughly the same as in Example 1 and will not be described again here.

[0073] Please see Figure 6 As shown, the fiber surface prepared in Comparative Example 1 has fewer MOF particles deposited. This is mainly due to the presence of impurities on the surface of the untreated carbon fiber, which reduces the deposition load of rare earth metal-organic framework particles.

[0074] Comparative Example 2

[0075] Comparative Example 1 provides a method for preparing flexible humidity-induced photoluminescent fibers. Compared with Example 1, the difference is that in step S1, the solvent of 2-aminoterephthalic acid (N,N-dimethylformamide) is replaced with deionized water. The rest is roughly the same as in Example 1, and will not be described again here.

[0076] The fiber surface prepared in Comparative Example 2 was free of particles. This is mainly because water solvents can affect the synthesis of rare earth metal-organic framework particles. Specifically, the MOF particles prepared in Example 1 of this invention will dissolve when exposed to water, so MOF particles cannot be synthesized using water as a solvent. However, the N,N-dimethylformamide in Example 1 can enable rare earth metal-organic framework particles to achieve stable and firm deposition loading.

[0077] Comparative Example 3

[0078] Comparative Example 1 provides a method for preparing flexible humidity-induced photoluminescent fibers. The difference from Example 1 is that the precursor mixture solution is not subjected to ultrasonic treatment in step S2. The rest is roughly the same as Example 1 and will not be described again here.

[0079] The MOF particles deposited on the fiber surface prepared in Comparative Example 3 were not uniform, mainly due to the uneven mixing of the precursor mixture solution without ultrasonic treatment. This application uses low-temperature ultrasonic treatment, which can achieve the technical effect of uniformly dispersing the precursor solution, thereby significantly improving the deposition loading capacity of rare earth metal organic framework particles.

[0080] Examples 2-5

[0081] Examples 2-5 provide a method for preparing flexible humidity-induced photoluminescent fibers. Compared with Example 1, the difference is that in step S1, the fiber substrate is replaced with metal-based fibers, polyester fibers, polytetrafluoroethylene fibers, or polyimide fibers. The rest is roughly the same as in Example 1, and will not be described again here.

[0082] Table 1 shows the performance parameters of Examples 1 to 5.

[0083] Example Types of high temperature resistant fibers Fluorescence properties Deposition thickness Particle size Granular crystal form Example 1 carbon fiber good 2~4μm 1~2μm Monoclinic crystal system Example 2 Metal-based fibers good 2~4μm 1~2μm Monoclinic crystal system Example 3 Polyester fiber good 2~4μm 1~2μm Monoclinic crystal system Example 4 polytetrafluoroethylene fiber good 2~4μm 1~2μm Monoclinic crystal system Example 5 polyimide fiber good 2~4μm 1~2μm Monoclinic crystal system

[0084] As can be seen from Table 1, the type of fiber has the following effect on the humidity-sensitive photoluminescence and mechanical properties: different types of fibers do not affect the deposition thickness, particle size and crystal form of MOF particles, and have no effect on the humidity-sensitive photoluminescence and mechanical properties of the fibers.

[0085] Examples 6-10

[0086] Examples 6-10 provide a method for preparing flexible humidity-induced photoluminescent fibers. Compared with Example 1, the difference is that in step S1, the molar mass ratio of the rare earth metal-organic framework precursor and 2-aminoterephthalic acid is set differently. The rest is roughly the same as in Example 1, and will not be repeated here.

[0087] Table 2 shows the performance parameters for Examples 1 and 6-10.

[0088]

[0089] As shown in Table 2, the effect of the molar mass ratio of rare earth metal-organic framework precursor and 2-aminoterephthalic acid on humidity-sensitive photoluminescence and mechanical properties is as follows: more or less rare earth metal-organic framework precursor will lead to a decrease in MOF deposition thickness and particle size, which in turn leads to a decrease in luminescence performance, but will not affect the crystal form of the particles or the mechanical properties of the fibers.

[0090] The effects of deposition thickness on fiber properties are as follows: the thicker the deposited MOF particles, the longer the fiber's luminescence time and the less prone it is to quenching; excessive deposition thickness leads to weak bonding between MOF particles and fibers, causing them to detach and reducing the fiber's luminescence performance. The effects of deposition thickness on fiber mechanical properties are as follows: within a suitable deposition thickness range, the fiber's mechanical properties will be improved to a certain extent; however, if the deposition thickness exceeds a certain range, the fiber's mechanical properties will be reduced.

[0091] The effect of particle size on fiber properties is as follows: if the particle size is too large, the adhesion force between the particles and the fiber surface is weaker, resulting in poorer fiber luminescence properties. The effect of particle size on fiber mechanical properties is as follows: particle size does not affect the mechanical properties of the fiber.

[0092] The effect of particle crystal form on fiber properties is as follows: regular particle crystal form results in better fiber luminescence properties. The effect of particle crystal form on fiber mechanical properties is as follows: particle crystal form does not affect the mechanical properties of the fiber.

[0093] Examples 11-14

[0094] Examples 11-14 provide a method for preparing flexible humidity-induced photoluminescent fibers. The difference from Example 1 is that the type of rare earth metal-organic framework precursor is different in step S1. The rest is roughly the same as in Example 1 and will not be repeated here.

[0095] Table 3 shows the performance parameters of Examples 1 and 11-14.

[0096]

[0097] As can be seen from Table 3, the type of rare earth metal-organic framework precursor has the following effect on the humidity-sensitive photoluminescence and mechanical properties: different rare earth metal-organic framework precursors do not affect the deposition thickness and particle size of MOF particles, and have no effect on the humidity-sensitive photoluminescence and mechanical properties of the fibers.

[0098] Examples 15-23

[0099] Examples 15-23 provide a method for preparing flexible humidity-induced photoluminescent fibers. Compared with Example 1, the difference lies in the setting of hydrothermal reaction temperature and hydrothermal reaction time in step S3. The rest is roughly the same as Example 1 and will not be described again here.

[0100] Table 4 shows the performance parameters of Examples 1 and 15-23.

[0101]

[0102]

[0103] As shown in Table 4, the effects of hydrothermal reaction temperature and time on humidity-sensitive photoluminescence and mechanical properties are as follows: excessively high hydrothermal reaction temperature or excessively long hydrothermal reaction time will lead to excessively large MOF particle deposition thickness and particle size, decreased particle adhesion, and decreased fiber fluorescence properties; excessively low hydrothermal reaction temperature or excessively short hydrothermal reaction time will lead to MOF particles not forming properly or fewer synthesized particles, thus affecting luminescence properties; however, this will not affect the crystal form of the particles or the mechanical properties of the fibers.

[0104] Examples 24-28

[0105] Examples 24-28 provide a method for preparing flexible humidity-induced photoluminescent fibers. The difference from Example 1 is that the ultrasonic parameters are set differently in step S2. The rest is roughly the same as in Example 1 and will not be described again here.

[0106] Table 5 shows the performance parameters of Examples 1 and 24-28.

[0107]

[0108] As can be seen from Table 5, the effect of ultrasonic parameters on humidity-sensitive photoluminescence and mechanical properties is as follows: ultrasonic parameters within a reasonable range have no effect on the synthesis of MOF particles and their deposition on the fiber surface, thus not affecting the humidity-sensitive photoluminescence and mechanical properties of the fiber.

[0109] In summary, this invention provides a flexible humidity-sensitive photoluminescent fiber, its preparation method, and its application, relating to the field of photoluminescent fiber preparation technology. The preparation method directly uses flexible high-temperature resistant fiber as a substrate, and grows regular rare earth metal-organic framework particles on its surface by hydrothermal growth to obtain flexible humidity-sensitive photoluminescent fiber. When the fiber material is moist, it emits bright blue light under ultraviolet light irradiation, thus obtaining humidity-sensitive photoluminescent fiber. The specific steps include: S1, firstly, preparing a 2-aminoterephthalic acid solution using N,N-dimethylformamide as a solvent; then, adding a rare earth metal-organic framework precursor to obtain a precursor mixture solution; S2, subjecting the precursor mixture solution to ultrasonic treatment; S3, placing the pretreated fiber in the ultrasonically treated precursor mixture solution for a hydrothermal reaction, wherein the hydrothermal temperature is 120–180℃ and the reaction time is 24–72 h; S4, after the hydrothermal reaction is completed and the solution cools to room temperature, removing the fiber and performing post-treatment such as cleaning and drying, uniformly depositing humidity-sensitive photoluminescent organic metal-organic framework particles of predetermined thickness, predetermined particle size, and crystal form on the surface of the flexible fiber to obtain a flexible humidity-sensitive photoluminescent fiber. The obtained flexible humidity-sensitive photoluminescent fiber possesses good flexibility, fast response time, excellent stability, and high luminescence brightness, showing promising application prospects in the fields of smart wearables and visual smart fibers.

[0110] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing flexible humidity-sensitive photoluminescent fibers, characterized in that, Includes the following steps: S1. First, a 2-aminoterephthalic acid solution is prepared using N,N-dimethylformamide as a solvent; then, a rare earth metal-organic framework precursor is added to obtain a precursor mixture solution; in the precursor mixture solution, the molar mass ratio of the rare earth metal-organic framework precursor to 2-aminoterephthalic acid is 2:1; the rare earth metal-organic framework precursor is one or a mixture of neodymium nitrate hexahydrate, europium nitrate hexahydrate, terbium nitrate hexahydrate, and gadolinium nitrate hexahydrate; S2, the precursor mixture solution is subjected to ultrasonic treatment; the ultrasonic treatment process is as follows: the precursor mixture solution is placed in an ice bath at 0~10℃, the ultrasonic time is 10~30min, and the ultrasonic power is 200~500W. S3, the pretreated high-temperature resistant fiber is placed in the precursor mixture solution after ultrasonic treatment and subjected to hydrothermal reaction; the pretreatment process of the high-temperature resistant fiber is as follows: the high-temperature resistant fiber is placed in water and alcohol solutions for ultrasonic cleaning in sequence, and then taken out and dried for later use; the specific process of the hydrothermal reaction is as follows: the precursor mixture solution is placed in a hydrothermal reactor, and then the pretreated fiber is added, wherein the hydrothermal temperature is 120~150℃ and the reaction time is 24~48h; S4. After the hydrothermal reaction is completed and the solution is cooled to room temperature, the fiber is taken out and cleaned and dried. Humidity-sensitive photoluminescent organic metal framework particles with a predetermined thickness, particle size and crystal form are uniformly deposited on the surface of the flexible high-temperature resistant fiber, thereby obtaining the flexible humidity photoluminescent fiber.

2. The method for preparing flexible humidity-sensitive photoluminescent fibers according to claim 1, characterized in that, In step S1, the concentration of the rare earth metal-organic framework precursor in the precursor mixed solution is 0.02~0.06 mol / L; and the concentration of the 2-aminoterephthalic acid solution is 0.01~0.03 mol / L.

3. The method for preparing flexible humidity-sensitive photoluminescent fibers according to claim 1, characterized in that, In step S3, the high-temperature resistant fiber includes one of carbon fiber, metal-based fiber, polyester fiber, polytetrafluoroethylene fiber, and polyimide fiber.

4. The method for preparing flexible humidity-sensitive photoluminescent fibers according to claim 1, characterized in that, In step S4, the humidity-sensitive photoluminescent organometallic framework particles have a particle size of 1~2µm, a monoclinic crystal system, and a deposition thickness of 2~4µm.

5. A flexible humidity-sensitive photoluminescent fiber, characterized in that, It is prepared by the method for preparing flexible humidity-sensitive photoluminescent fibers according to any one of claims 1 to 4; The flexible humidity-sensitive photoluminescent fiber includes a high-temperature resistant fiber matrix and humidity-sensitive photoluminescent organometallic framework particles uniformly deposited on the surface of the high-temperature resistant fiber; the humidity-sensitive photoluminescent organometallic framework particles have a particle size of 0.5~2.5µm, a monoclinic crystal system, and a deposition thickness of 1~4µm. The flexible humidity-sensitive photoluminescent fiber emits blue fluorescence when stimulated by changes in ambient humidity and is irradiated by ultraviolet light.

6. The flexible humidity-induced photoluminescent fiber according to claim 5, or the application of the flexible humidity-induced photoluminescent fiber prepared by the method of any one of claims 1 to 4, characterized in that, Applications of the flexible humidity-sensitive photoluminescent fiber in the fields of smart wearables, smart anti-counterfeiting, and environmental monitoring.

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