Thermosensitive ultra-long room-temperature phosphorescent organic small molecule gel and anti-counterfeiting application

Abstract

The invention provides thermosensitive ultra-long room-temperature phosphorescent organic micromolecule gel. The thermosensitive ultra-long room-temperature phosphorescent organic micromolecule gel comprises stable gel which is formed by a non-classical organogelator m-BrPBCM with a rigid conjugated structure in an organic solvent. The small organic molecule gel is a supramolecular aggregate formed by self-assembly based on the acting force of intermolecular non-covalent bonds, has the characteristics of large specific surface area, dynamic reversibility, sensitive response to stimulation and the like, and has important application value in numerous research fields such as sensing and recognition, anti-counterfeiting encryption and the like. In order to reduce non-radiative relaxation generated by rotation of carbon chain molecules, the invention synthesizes a non-classical organogelator m-BrPBCM with a rigid conjugated structure, and the non-classical organogelator m-BrPBCM can form stable gel in DMSO. Obvious afterglow of the m-BrPBCM gel can be observed at low temperature, phosphorescence is weakened at room temperature, and the phosphorescence disappears after heating; after the temperature is reduced to the low temperature again, phosphorescence can be recovered, and the method has a wide application prospect in the field of dynamic anti-counterfeiting.

Description

Technical Field

[0001] The invention relates to the field of organic phosphorescent materials, in particular to an ultra-long room temperature phosphorescent organic small molecule gel with thermosensitive properties and a preparation method thereof, as well as applications of the gel in biological imaging, anti-counterfeiting encryption and optoelectronic devices. Background Art

[0002] After absorbing the energy of the excitation light, the electrons of the organic phosphorescent material can jump from the ground state to the singlet excited state (S1), then to the excited triplet state (T1) through intersystem crossing (ISC), and finally decay from the lowest energy level of the triplet state T1 back to the ground state to emit phosphorescence, and its lifetime can reach microseconds or even seconds. Compared with conventional fluorescent materials, phosphorescent materials have the characteristics of long lifetime and large Stokes shift, which can effectively avoid the influence of the excitation light source and have potential applications in biological imaging, anti-counterfeiting encryption and optoelectronic devices. At the same time, the stimuli-responsive ultra-long organic room temperature phosphorescent materials can change under external stimuli, which can further enhance the anti-counterfeiting performance.

[0003] The organic dynamic long-lifetime room temperature phosphorescent materials reported so far are mainly crystalline materials and host-guest doping systems. As a multifunctional soft material with excellent performance, the gel system has the characteristics of sensitive temperature response, easy processing and good repeatability, which can well meet the requirements of practical applications in the field of dynamic anti-counterfeiting. Supramolecular gel is a three-dimensional network structure formed by balanced non-covalent bond forces (hydrogen bonds, π-π, halogen bonds, electrostatics, etc.) between molecules, and has thermal reversibility. Generally, the gel factor obtains a uniform solution when heated, and forms a gel when cooled to room temperature or under ultrasonic conditions. In the gel state, the three-dimensional network structure of the gel can well restrict the movement of molecules; after heating and dissolving, the gel fluidity is enhanced, which can quench triplet excitons. Therefore, gel materials with room temperature phosphorescent properties can be used for dynamic anti-counterfeiting. In recent years, pure organic small molecule room temperature phosphorescent materials have flourished, and some room temperature phosphorescent materials have been reported, but reports on room temperature phosphorescent gel materials are still relatively rare. Therefore, designing room temperature phosphorescent gel materials with excellent performance and thermosensitive properties can well fill the gap in this field. Therefore, it is of great significance to develop room temperature phosphorescent gel materials with thermosensitive properties. Summary of the invention

[0004] The present invention provides a thermosensitive ultra-long room temperature phosphorescent organic small molecule gel, which contains a non-classical organic gel factor m-BrPBCM with a rigid conjugated structure. The gel factor can form a stable gel in dimethyl sulfoxide (DMSO) and exhibits unique thermosensitive phosphorescent properties: it has obvious afterglow at low temperatures, the phosphorescence weakens at room temperature, and the phosphorescence disappears after heating.

[0005] Specifically, the thermosensitive ultra-long room temperature phosphorescent organic small molecule gel of the present invention has the following characteristics: A thermosensitive ultra-long room temperature phosphorescent organic small molecule gel, comprising a non-classical organic gel factor m-BrPBCM with a rigid conjugated structure to form a stable gel in an organic solvent, wherein the organic gel factor m-BrPBCM has a structural formula of The organic solvent includes dimethyl sulfoxide (DMSO) or dimethylformamide (DMF).

[0006] The concentration of the organic gel factor m-BrPBCM is 15-30 mg / mL, and the gel-sol transition temperature is 55°C.

[0007] The preparation method of the thermosensitive ultra-long room temperature phosphorescent organic small molecule gel comprises the following steps: reacting 5-bromoisophthalic acid with dichlorothionyl to obtain 5-bromoisophthaloyl chloride, reacting with carbazole in the presence of NaH, purifying by column chromatography to obtain m-BrPBCM, dissolving m-BrPBCM in DMSO, heating and cooling to room temperature or ultrasonically forming a gel factor, and the reaction formula of the organic gel factor m-BrPBCM is as follows: .

[0008] The present invention also provides an anti-counterfeiting material or a dynamic anti-counterfeiting material, comprising the thermosensitive ultra-long room temperature phosphorescent organic small molecule gel.

[0009] The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel forms an anti-counterfeiting effect or a dynamic anti-counterfeiting effect under ultraviolet light irradiation and / or temperature change to realize an anti-counterfeiting material or a dynamic anti-counterfeiting material.

[0010] The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel is used as an anti-counterfeiting material to display fluorescence under ultraviolet light to form an anti-counterfeiting pattern or logo; The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel as a dynamic anti-counterfeiting material displays fluorescence under ultraviolet light irradiation, and realizes reversible switching of phosphorescence through temperature control to form an anti-counterfeiting pattern or logo.

[0011] The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel is in a gel state at room temperature, gradually rises to 45° C. to a semi-gel state, rises to a sol state again, and then returns to a gel state when cooled to room temperature.

[0012] The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel is in a gel state at room temperature, and is in a fluorescent coloring state when irradiated with ultraviolet light, and is in an afterglow state under an ice water bath. After the temperature is raised to above 45°C, the afterglow disappears and it is in a fluorescent coloring state. After it is lowered to a low temperature again, the phosphorescence can be restored.

[0013] The present invention provides an anti-counterfeiting device, comprising the thermosensitive ultra-long room temperature phosphorescent organic small molecule, which is used for dynamic anti-counterfeiting effect under ultraviolet light irradiation and / or temperature control. The anti-counterfeiting device turns on and off the phosphorescence through temperature changes, thereby displaying specific anti-counterfeiting information under specific conditions.

[0014] The present invention applies the thermosensitive ultra-long room temperature phosphorescent organic small molecules in biological imaging, anti-counterfeiting encryption and optoelectronic devices.

[0015] The technical solution of the present invention has the following beneficial effects: 1. The minimum gel concentration of m-BrPBCM in DMSO is 15 mg / mL, and the gel-sol transition temperature is 55°C.

[0016] 2. The gel emits blue-white fluorescence at room temperature, and a long-wavelength emission peak appears clearly in the delayed spectrum. It has a phosphorescence lifetime of 203.77 ms and a phosphorescence quantum efficiency of 2.12%.

[0017] 3. Under low temperature conditions, the phosphorescence lifetime of the gel increases significantly, and an obvious yellow-green afterglow can be observed in an ice water bath, which can last up to 1.5 seconds.

[0018] 4. In addition, the present invention also relates to the use of the gel in a dynamic anti-counterfeiting method, which realizes the reversible switching of phosphorescence by temperature control to form an anti-counterfeiting pattern or logo. When the anti-counterfeiting pattern or logo is heated to 45°C, the fluorescence does not change significantly but the phosphorescence disappears, and the phosphorescence recovers after cooling to a low temperature. This process can be completely reversibly repeated.

[0019] The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel of the present invention not only fills the blank of room temperature phosphorescent gel materials, but also provides its potential application in the fields of dynamic anti-counterfeiting, bio-imaging, anti-counterfeiting encryption and optoelectronic devices. The gel material has excellent thermosensitive properties and can realize the reversible switch of phosphorescence by temperature control, providing a new means for anti-counterfeiting technology. At the same time, the preparation method of the gel is simple, the raw materials are easily available, and it has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 . H-NMR spectrum of m-BrPBCM.

[0021] Figure 2 . NMR carbon spectrum of m-BrPBCM.

[0022] Figure 3 . High-resolution mass spectrum of m-BrPBCM.

[0023] Figure 4(A) Mechanical properties of m-BrPBCM gel in DMSO (frequency 6.28 rads −1 , strain is 0.1%); (B) sol-gel transition (under sunlight and 365 nm UV light); (C) SEM of dry gel and optical microscope photos of wet gel; (D) XRD of dry gel.

[0024] Figure 5 . (A) H-NMR spectra of the gel at different temperatures; (B) Fluorescence spectra during the sol-to-gel transition process.

[0025] Figure 6 . (A) Steady-state and delayed spectra of the m-BrPBCM gel state; (B) The lifetime of the gel at different temperatures; (C) The afterglow images of the gel at room temperature and 2°C.

[0026] Figure 7 Dynamic anti-counterfeiting devices prepared using m-BrPBCM gel. DETAILED DESCRIPTION

[0027] Example 1 Synthesis of m-BrPBCM 1. Add 5-bromoisophthalic acid (1.0843 g, 4.44 mmol) into a flask, add dropwise a solution of thionyl chloride (1.82 g, 15.3 mmol) in N,N-dimethylformamide (0.3 ml), heat to 80°C and stir vigorously. After reacting for 19 h, 5-bromoisophthaloyl chloride was obtained for later use.

[0028] 2. Under nitrogen, add NaH (0.265 g, 11.04 mmol), then add carbazole (0.492 g, 2.94 mmol) in anhydrous tetrahydrofuran (8 ml), stir at room temperature for 0.5 h, then add 5-bromoisophthaloyl chloride prepared in the previous step dissolved in anhydrous tetrahydrofuran (30 ml), stir at room temperature for 16 h, add water to quench the reaction, and extract with dichloromethane three times. After combining the organic phases, dry with anhydrous sodium sulfate, and purify by column chromatography to obtain 215.6 mg of white solid m-BrPBCM (yield 13.5%). Figure 1 , 2 , 3 are the H-NMR spectrum, C-NMR spectrum and high-resolution mass spectrum of the white solid m-BrPBCM, indicating that the purity of the product obtained in this case is extremely high.

[0029] Example 2 Gel preparation and performance testing The gelation behavior of m-BrPBCM in different solvents was tested by the traditional inversion method: m-BrPBCM was dissolved in the test solvent (concentration 15 mg / ml) under heating conditions, cooled to room temperature or after ultrasound, if it did not flow after inversion, it was considered to have formed a gel. The results showed that m-BrPBCM can form stable gels in DMSO and DMF. At the same time, multiple groups of experiments were conducted to test whether gels could be formed under concentrations of 5 mg / mL, 10 mg / mL, 15 mg / mL, 20 mg / mL, 25 mg / mL, 30 mg / mL, and 35 mg / mL. Finally, it was found that the minimum gel concentration was 15 mg / mL. In addition, the gel was tested by heating from room temperature (25°C) to 85°C, and the gel-sol transition temperature was found to be 55°C.

[0030] Example 3 To better prove the formation of gel, the DMSO gel of m-BrPBCM was tested for thixotropy. The experimental steps were as follows: weigh 20 mg of sample m-BrPBCM, dissolve it in 1 mL of DMSO, heat it to completely dissolve it, and then use ultrasound to make it completely gel. The gel sample was placed in a rheometer, and the test system was selected as a parallel plate. The sample type was determined based on the initial test results, and the parameters were adjusted for thixotropy testing. Figure 4 As shown in Figure A, the storage modulus G` of the gel formed in DMSO is 4671 Pa, and the loss modulus G`` is 771 Pa, which proves the formation of m-BrPBCM gel in DMSO. At the same time, it can be observed that its critical strain value is 4.65%, which further proves that the gel still has a certain strength when the external conditions change.

[0031] Figure 4 Figure B shows the photos of the solution sample and the gel sample under sunlight and 365 nm UV light. It can be observed that the fluorescence of m-BrPBCM in the gel state is also enhanced to a certain extent.

[0032] According to the scanning electron microscope images ( Figure 4 C) shows that the DMSO gel of m-BrPBCM presents a rod-like structure after drying. The nanorods are cross-linked and entangled to form a three-dimensional network structure with certain gaps, but some crystallization occurs. XRD test of the dry gel ( Figure 4 After the dry gel was dried, multiple diffraction peaks were found, which proved this conclusion. According to the optical microscope image of the wet gel, most of them were long and thin nanofiber structures. Therefore, it can be considered that the partial crystallization phenomenon in the dry gel occurred during the freeze-drying process to remove DMSO.

[0033] Example 4 In order to further explore the self-assembly mode of m-BrPBCM in DMSO, the temperature-dependent H NMR spectrum was measured. The experimental steps were as follows: 5 mg of m-BrPBCM sample was placed in an NMR tube, dissolved in 0.5 ml deuterated DMSO, placed in an NMR instrument, and set the programmed temperature mode for testing. Figure 5 As shown in Figure A, with the increase of temperature, protons at different positions in the carbazole unit showed high-field movement and low-field movement. This indicates that the increase in temperature causes the gel to gradually transform into a sol, which in turn causes the change in the intermolecular interaction force between similar carbazole units, thereby changing the electron cloud density of these protons. During the gel-sol transition process, the protons on the aromatic rings undergo a significant displacement with the increase in temperature, which also indicates that the π-π force between the aromatic rings has changed.

[0034] The fluorescence emission of molecules is affected by many factors, and during the sol-gel transition of m-BrPBCM, its fluorescence spectrum also changes. When in the sol state, the temperature in the system is high and the molecular motion rate is high, so the probability of the molecules rotating themselves and colliding with the sol molecules increases, resulting in non-radiative transitions and relatively weak fluorescence emission intensity. Figure 5 It can be observed in Figure B that when m-BrPBCM is in the DMSO sol state, the fluorescence emission intensity is low, and two broad emission peaks appear in the short-wave and long-wave regions, corresponding to the single molecule state and the π aggregate state, respectively. As the temperature decreases, the fluorescence intensity gradually increases, and a certain displacement occurs, and a single emission peak with higher intensity appears at 470 nm. Compared with the fluorescence emission of the single molecule state, this emission peak is significantly red-shifted, but shorter than the emission peak of the π aggregate state in the sol. This shows that the intermolecular π-π interaction is significantly different during the sol-gel transition. Therefore, the balanced intermolecular π-π interaction between m-BrPBCM molecules is the driving force for gel formation and plays a key role in the gelation process.

[0035] Example 5 The experimental steps for the steady-state and delayed spectrum test of the m-BrPBCM gel state are as follows: weigh 4 mg of m-BrPBCM in a cuvette, add 0.2 ml of DMSO solvent, heat to completely dissolve it, ultrasonicate to obtain a gel sample, then put it into the test instrument, set the mode to FL, the excitation wavelength to 370 nm, and test the steady-state spectrum of m-BrPBCM. Then set the mode to PL, the excitation wavelength to 370 nm, and test the delayed spectrum of m-BrPBCM.

[0036] The experimental steps for the life test of m-BrPBCM gel at different temperatures are as follows: prepare the gel sample in the same way, put it into the life test instrument, and test it normally at room temperature. Under 77 K conditions, liquid nitrogen needs to be added to the sample to cool it down, so as to obtain the life of the sample at different temperatures.

[0037] The experimental steps of the m-BrPBCM gel afterglow image shooting test at room temperature and 2℃ are as follows: the gel state sample is also prepared, and then the room temperature is maintained in a dark room, and a handheld UV lamp with a wavelength of 365 nm is used for irradiation, and then a camera is used to record the entire process from the UV lamp turning on to turning off and then the phosphorescence extinguishing, and then the image corresponding to the time node is intercepted. The temperature condition of 2℃ is achieved by placing the sample in an ice water bath (the thermometer monitors and maintains 2℃), and then irradiating it with a handheld UV lamp with a wavelength of 365 nm, and using a camera to record the entire process from the UV lamp turning on to turning off and then the phosphorescence extinguishing, and finally the image corresponding to the time node is intercepted.

[0038] The DMSO gel state of m-BrPBCM emits blue-white fluorescence at room temperature, but its delayed spectrum (delay time 0.1 s) will clearly show a long-wavelength emission peak. Therefore, after turning off the UV light, the yellow-green afterglow of the gel can be observed instantly; its lifetime is 203.77 ms, and the afterglow disappears within 1 s after the excitation light irradiation stops; its phosphorescence quantum efficiency is 2.12% (such as Figure 6 As shown in A). Compared with crystal materials, gel is a soft material, which contains a large number of solvent molecules and oxygen, which has a certain quenching effect on triplet excitons; at the same time, the steric hindrance of the benzene ring is small, and the movement of molecules may lead to non-radiative transitions. These factors may be the reason for the weak afterglow intensity of the DMSO gel of m-BrPBCM. The lifetime under 77K conditions was further tested, and it was found that the lifetime increased significantly under low temperature conditions, proving to be phosphorescent emission. In an ice water bath, the intensity of the afterglow was also significantly enhanced, and obvious yellow-green afterglow could be observed within 1.5 s, indicating that the phosphorescence of the gel material of m-BrPBCM is sensitive to temperature.

[0039] Example 6 Dynamic anti-counterfeiting device prepared using m-BrPBCM gel The afterglow of phosphorescent gel materials is very sensitive to temperature, so it can be used in the field of dynamic anti-counterfeiting. First, the number "888" was made, of which the number "502" was made of DMSO gel of m-BrPBCM, and the remaining part was composed of fluorescent materials with similar fluorescence but no phosphorescent afterglow. Under irradiation with 365nm ultraviolet light, the fluorescence of the number "888" can be clearly observed. Under the condition of ice water bath cooling, since only the number "502" is composed of DMSO gel of m-BrPBCM, only the number "502" has phosphorescent emission, so only the afterglow pattern of 502 can be observed. After heating to 45 degrees to form a semi-gel, there is no obvious change in fluorescence, but the afterglow disappears completely. This process can be repeated completely reversibly, showing good dynamic anti-counterfeiting effects, such as Figure 7 shown.

Claims

1. A thermosensitive ultra-long room temperature phosphorescent organic small molecule gel, characterized in that: The non-classical organic gel factor m-BrPBCM having a rigid conjugated structure forms a stable gel in an organic solvent, wherein the organic gel factor m-BrPBCM has the structural formula The organic solvent includes dimethyl sulfoxide (DMSO) or dimethylformamide (DMF).

2. The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel according to claim 1, characterized in that: The concentration of the organogel factor m-BrPBCM was 15-30 mg / mL, and the gel-sol transition temperature was 55°C.

3. A method for preparing a thermosensitive ultra-long room temperature phosphorescent organic small molecule gel as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: reacting 5-bromoisophthalic acid with dichlorothionyl to obtain 5-bromoisophthaloyl chloride, reacting the 5-bromoisophthalic acid with carbazole in the presence of NaH, purifying the m-BrPBCM by column chromatography, dissolving the m-BrPBCM in DMSO, heating and cooling to room temperature or ultrasonically forming a gel factor, and the reaction formula of the organic gel factor m-BrPBCM is as follows: 。 4. An anti-counterfeiting material or a dynamic anti-counterfeiting material, characterized in that: It comprises the thermosensitive ultra-long room temperature phosphorescent organic small molecule gel as described in any one of claims 1-2.

5. The anti-counterfeiting material or dynamic anti-counterfeiting material according to claim 4, characterized in that: The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel forms an anti-counterfeiting effect or a dynamic anti-counterfeiting effect under ultraviolet light irradiation and / or temperature change to realize an anti-counterfeiting material or a dynamic anti-counterfeiting material.

6. The anti-counterfeiting material or dynamic anti-counterfeiting material according to claim 5, characterized in that: The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel is used as an anti-counterfeiting material to display fluorescence under ultraviolet light to form an anti-counterfeiting pattern or logo; The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel as a dynamic anti-counterfeiting material displays fluorescence under ultraviolet light irradiation, and realizes reversible switching of phosphorescence through temperature control to form an anti-counterfeiting pattern or logo.

7. The anti-counterfeiting material or dynamic anti-counterfeiting material according to claim 5, characterized in that: The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel is in a gel state at room temperature, gradually rises to 45° C. to a semi-gel state, rises to a sol state again, and then returns to a gel state when cooled to room temperature.

8. The anti-counterfeiting material or dynamic anti-counterfeiting material according to claim 7, characterized in that: The thermosensitive ultra-long room temperature phosphorescent organic small molecule gel is in a gel state at room temperature, and is in a fluorescent coloring state when irradiated with ultraviolet light, and is in an afterglow state under an ice water bath. After the temperature is raised to above 45°C, the afterglow disappears and it is in a fluorescent coloring state. After it is lowered to a low temperature again, the phosphorescence can be restored.

9. An anti-counterfeiting device, characterized in that: The thermosensitive ultra-long room temperature phosphorescent organic small molecule comprising any one of claims 1-2 is used for dynamic anti-counterfeiting effect under ultraviolet light irradiation and / or temperature control. The anti-counterfeiting device turns on and off the phosphorescence through temperature changes, thereby displaying specific anti-counterfeiting information under specific conditions.

10. Use of the thermosensitive ultra-long room temperature phosphorescent organic small molecule according to any one of claims 1 to 2 in biological imaging, anti-counterfeiting encryption and optoelectronic devices.

Images