A supramolecular fluorescent material with multiple responses and preparation method thereof

Abstract

The present invention discloses a supramolecular fluorescent material with multiple responses and a preparation method thereof. The system is based on the supramolecular self-assembly of DCSO molecules, and comprises a hydrophobic middle segment of dicyanostyrene (DCS) with fluorescent properties and a hydrophilic end chain of oligo(ethylene glycol) (OEG) with temperature response. At the same time, the DCS group plays the role of an efficient fluorophore, while the OEG chain gives the molecule a temperature-sensitive property. Therefore, DCSO can respond to temperature by self-assembly in the aqueous phase, and can also regulate the fluorescence color by changing the temperature. In addition to responding to temperature, DCSO also responds to solvents, humidity, and ultraviolet radiation, accompanied by changes or quenching of the fluorescence color. The present invention will effectively promote the further development of single-fluorophore luminescent materials with multiple stimulus response functions, such as fluorescent thermometers, solvent polarity indicators, humidity indicators, encryption and erasure of information, etc.

Description

Technical Field

[0001] The invention belongs to the field of supramolecular fluorescent materials, and in particular relates to a supramolecular fluorescent material with multiple responses and a preparation method thereof. Background Art

[0002] Chameleons in nature can quickly "blend in" to their surroundings and successfully disguise themselves to hunt and avoid enemies. Inspired by nature, scientists also hope to create a stimulus-responsive system that can achieve multicolor luminescence performance through simple stimulation from the external environment to meet various real-life needs. The response of molecular systems to external stimuli is basically achieved through reversible molecular movements or reactions, generating certain signals as feedback to the stimulus. In this regard, fluorescent signals are the perfect choice for monitoring reactions due to their advantages such as excellent sensitivity, fast response, low background noise and simplicity. Therefore, in recent decades, the use of fluorescence to monitor functional luminescent materials with stimulus-responsive properties has become increasingly common.

[0003] Most responsive systems based on organic fluorophores usually exhibit fluorescence response to only one specific external stimulus, such as light, mechanical, thermal, and solvation response. However, materials with multiple fluorescence response behaviors based on a single fluorophore are relatively rarely reported. In addition, realizing color-tunable emission materials by using a single fluorophore is another major challenge. Summary of the invention

[0004] The stimulus-responsive fluorescent molecules reported so far generally have the characteristics of a single response, which makes it difficult to meet the diversified application requirements. The design of multiple stimulus-responsive fluorescent molecules is very challenging. To achieve the above purpose, the present invention connects oligo(ethylene glycol) (OEG) groups to both sides of the dicyanostyrene (DCS) motif to obtain a new molecule DCSO, thereby realizing a multi-stimulus-responsive fluorescent system. The OEG group makes the molecule soluble in aqueous media and promotes the self-assembly of amphiphilic molecules. The specific technical solutions adopted are:

[0005] A supramolecular fluorescent material with multiple responses, the supramolecular fluorescent material is based on the supramolecular self-assembly of DCSO molecules in water phase, the chemical structure of DCSO is as follows:

[0006]

[0007] Preferably, DCSO has a temperature response characteristic in water, and the fluorescence luminescence of DCSO blue-shifts as the temperature increases, and red-shifts as the temperature decreases.

[0008] Preferably, DCSO has a solvent response characteristic, and the fluorescence luminescence of DCSO in a solvent red-shifts as the polarity of the solvent increases, and blue-shifts as the polarity of the solvent decreases.

[0009] Preferably, DCSO has a humidity response characteristic, and the fluorescence luminescence of DCSO blue-shifts as the humidity decreases, and red-shifts as the humidity increases.

[0010] Preferably, DCSO has irradiation-responsive thermal properties in water, and the fluorescence luminescence of DCSO blue-shifts as the ultraviolet light irradiation time increases, and is eventually quenched; the fluorescence color change rate of the DCSO aqueous solution under ultraviolet light irradiation is negatively correlated with the concentration of the DCSO aqueous solution.

[0011] The present invention also provides a method for preparing a supramolecular fluorescent material with multiple responses. DCSO is prepared by nucleophilic substitution of compound A and compound B. The preparation process is as follows:

[0012] , and then DCSO is added into water, and self-assembly is driven by hydrophilic and hydrophobic forces to form supramolecular fluorescent materials.

[0013] Preferably, the preparation method of DCSO specifically comprises the following steps:

[0014] Under N2 atmosphere, K2CO3, compound A and acetonitrile were added to the flask, and then the acetonitrile solution of compound B was slowly added dropwise. The mixture was stirred and refluxed at 80-90°C for 20-30 hours, then cooled and concentrated under reduced pressure. The mixture was purified by column chromatography to obtain a yellow viscous oily compound, namely DCSO.

[0015] Preferably, the molar ratio of K2CO3, compound A and compound B is (2.9-4):1:(2.0-2.5).

[0016] Preferably, the synthesis method of compound A is: starting from p-methoxyphenylacetonitrile, demethylating the compound A after electrophilic addition reaction with terephthalaldehyde;

[0017] The synthesis method of compound B is as follows: starting from triethylene glycol monomethyl ether, after condensing with methyl trihydroxybenzoate to form ether, a reduction reaction is performed to convert the ester group into a hydroxyl group, and finally reacting with TMSBr to obtain compound B.

[0018] Preferably, the concentration of DCSO in distilled water is greater than 176 μM.

[0019] The above technical solution has the following advantages:

[0020] (1) The DCSO molecule provided by the present invention comprises a hydrophobic core (dicyanostyrene) with fluorescent properties and a hydrophilic end (polyethylene glycol ether chain) with temperature response. It is an amphiphilic molecule that can self-assemble in the aqueous phase to assemble into fluorescent nanoparticles. Since the conjugated structure of dicyanostyrene is large and the fluorescence is strong, and there are many hydrophobic parts in the middle, the differences between the DCSO assembly forms are magnified, resulting in DCSO having multiple responses. Under various stimuli such as temperature, solvent, humidity, and radiation, its fluorescence color will respond to changes.

[0021] (2) DCSO molecules have different emission colors at different temperatures. At low temperatures, the DCSO aqueous solution is yellow, and at high temperatures, the DCSO aqueous solution is green. The fluorescence emission wavelength blue-shifts as the temperature increases, so it can be used as a fluorescence thermometer.

[0022] (3) DCSO molecules have the characteristic of changing color in response to different solvents. They will show different fluorescence colors depending on the polarity of the solvent. The fluorescence emission wavelength red-shifts as the polarity of the solvent increases, and can be used as a solvent polarity indicator.

[0023] (4) DCSO molecules have the property of changing color in response to humidity. The fluorescence emission wavelength redshifts as the humidity increases. In the thin film state, it responds to water vapor stimulation. Simply by blowing the air dry, the fluorescence color will change from yellow-green to bright blue. It can be used as a humidity indicator.

[0024] (5) DCSO has a significant photoresponsive behavior, showing different colors of fluorescence (yellow-green to blue-green) before and after ultraviolet light irradiation. At the same time, as the irradiation time increases, the fluorescence of the solution gradually quenches, and the fluorescence change rate is negatively correlated with the concentration, which can be used for information encryption and erasure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention, in which:

[0026] Figure 1 It is a schematic diagram of the technical solution of the present invention.

[0027] Figure 2 is the NMR hydrogen of compound DCSO ( 1 H NMR) spectrum.

[0028] Figure 3 is the NMR carbon of compound DCSO ( 13 C NMR) spectrum.

[0029] Figure 4 This is the high-resolution mass spectrum of the compound DCSO, [M+H] +=1517.7522.

[0030] Figure 5 Transmission electron microscopy image of DCSO assembly.

[0031] Figure 6 This is the normalized fluorescence spectrum of DCSO aqueous solution changing with temperature.

[0032] Figure 7 This is the normalized fluorescence spectrum of DCSO solvent-induced color change.

[0033] Figure 8 Figure 1 is a diagram of the DCSO humidity response cycle, where a is a photograph of the fluorescence color change of the test paper soaked in DCSO aqueous solution in dry and wet states, and b is a reversible cycle diagram of the DCSO test paper in the dry-wet state.

[0034] Fig. 9 This is the fluorescence spectrum of compound DCSO in response to radiation. DETAILED DESCRIPTION

[0035] The following disclosure provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0036] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments are all conventional methods in the art unless otherwise specified.

[0037] The present invention provides a supramolecular system with multiple responsiveness. The multiple responsive supramolecular system is based on supramolecular self-assembly of DCSO in water phase. The chemical structure of DCSO is as follows:

[0038]

[0039] The present invention also provides a method for preparing multi-responsive fluorescent supramolecular nanoparticles, wherein DCSO is synthesized from compound A and compound B:

[0040]

[0041] The DCSO molecule has the following behavioral characteristics:

[0042] The first characteristic of DCSO is that it is an amphiphilic molecule. Its molecule contains a polyethylene glycol ether chain (OEG) part, which is a hydrophilic end; and a dicyanostyrene (DCS) part, which is a hydrophobic core. Above the critical aggregation concentration (CAC, the value of which is 176μM as determined by the transmittance experiment), DCSO will be driven by the hydrophilic and hydrophobic forces to form spherical nanoassemblies, such as the attached Figure 5 shown.

[0043] The second characteristic of DCSO is that it is temperature responsive. As the temperature rises, the fluorescence intensity of DCSO at 540nm gradually decreases, the emission peak at 490nm gradually increases, and the fluorescence color changes from yellow-green to cyan. Figure 6 This change can be achieved by 490 / I 540 The relationship between (I represents luminescence intensity) and temperature reveals that with the increase of temperature, there is an inflection point at 54.8°C, reflecting the turbidity point determined by fluorescence. Therefore, it is shown that DCSO has good temperature stimulus responsiveness.

[0044] The third characteristic of DCSO is that it has solvent-induced color change. Since DCSO molecules have a large conjugated structure, there is charge transfer (ICT) of intramolecular photoluminescence. As the polarity of the solvent decreases, different fluorescence colors can be observed, from yellow to green to blue. When the solvent polarity decreases from water to carbon tetrachloride, the fluorescence emission peak blue-shifts from 540nm to 450nm. Figure 7 shown.

[0045] The fourth characteristic of DCSO is that it has humidity-responsive color change properties. When the filter paper is soaked in a DCSO aqueous solution, the fluorescence in the film state is stimulus-responsive to water vapor. Simply blow dry the air and the fluorescence color will change from yellow-green to bright blue, and it can go through multiple cycles, such as the attached Figure 8 This may be due to the dielectric constant of air being close to that of low-polarity solvents, which is consistent with the solvatochromic effect.

[0046] The fifth characteristic of DCSO is that it responds to ultraviolet radiation. Since the cyanostyrene group has a significant light response behavior, the DCSO molecule with dicyanostyrene as the hydrophobic core has the same response characteristics to the stimulation of ultraviolet radiation. The results show that with the extension of irradiation time (irradiation wavelength λ irr =365nm), the fluorescence of the solution gradually changes from bright yellow to light blue and finally quenches. Fig. 9 shown.

[0047] The sixth characteristic of DCSO is concentration response. Under certain conditions of radiation wavelength, radiation time and radiation intensity, the fluorescence change rate of low-concentration DCSO solution is much faster than that of high-concentration solution, and the process of changing from yellow to blue and finally quenching occurs earlier. This characteristic can be used for information encryption. Figure 1 As shown, the "encoding" was initially performed using solutions of different concentrations, all of which had yellow-green fluorescence. After a period of ultraviolet light exposure, the color of the low-concentration solution turned blue, and the information was decrypted; with continued exposure to light, the fluorescence of all samples was quenched, and the information was "erased."

[0048] Example 1

[0049] 1. Synthesis of DCSO: Under N2 protection, add compound A (0.20 g, 0.55 mmol), acetonitrile (8 mL), K2CO3 (0.22 g, 1.59 mmol) to a 50 mL round-bottom flask, then slowly dropwise add a solution of compound B (0.75 g, 1.14 mmol) in acetonitrile (8 mL), reflux at 85 °C, and react overnight. After the reaction is complete, stop stirring. After cooling to room temperature, collect the organic phase, dry it, and spin dry it on a rotary evaporator. Purify the crude product by column chromatography (eluent ratio (DCM: MeOH = 100: 1, v / v)), and collect the spin-dried product to obtain a yellow viscous liquid DCSO. The nuclear magnetic hydrogen spectrum of DCSO is shown in the attached figure. Figure 2 As shown, the NMR carbon spectrum is as shown in the attached Figure 3 As shown in the attached high resolution mass spectra Figure 4 shown.

[0050] 2. DCSO molecules self-assemble in distilled water driven by hydrophilic and hydrophobic forces. The transmittance experiment determined that the critical aggregation concentration of DCSO at 20°C was 176μM. Above this concentration, DCSO assembled into nanoparticles, as shown in the transmission electron microscopy image attached. Figure 5 shown.

[0051] 3. Temperature response: DCSO molecules have temperature response due to their temperature-responsive polyethylene glycol ether chains. When a 0.2 mM aqueous solution of DCSO is prepared at 20°C, DCSO molecules self-assemble into ordered nanospheres, in which the cyanostyrene (CS) parts are tightly packed, and the intramolecular motion is restricted. They have strong emission at 540nm and show yellow fluorescence. As the temperature rises from 20°C to 80°C, the fluorescence intensity of DCSO gradually decreases at 540nm, while a new peak appears at 490nm and gradually increases. At the same time, the fluorescence color changes from yellow to green, see the attached figure. Figure 6 .

[0052] 4. Solvent response: Ten different organic solvent systems were prepared to prepare 0.2 mM DCSO, namely carbon tetrachloride, chloroform, toluene, ether, etc. These ten organic solvents were oscillated by ultrasonic method to make them dispersed evenly. Figure 7 .

[0053] In this embodiment, the ultrasonic instrument used is an ultrasonic cleaning machine commonly used in laboratories, and the frequency is 40 kHz.

[0054] 5. Humidity response: completely immerse the filter paper in the prepared 0.2mM DCSO aqueous solution and wait for 1 minute; take out the immersed filter paper and it will show yellow fluorescence under ultraviolet light, put it on a watch glass and dry it with a hair dryer, and wait for 2 minutes; observe the dried filter paper under ultraviolet light and it will show cyan fluorescence, which is close to the color of low-polarity solvents; continue to immerse the dried filter paper in 0.2mM DCSO aqueous solution and wait for 1 minute; repeat putting it on a watch glass and dry it with a hair dryer, and wait for 2 minutes; the response of DCSO aqueous solution to humidity is shown in the attached figure. Figure 8 shown.

[0055] 6. Response to ultraviolet radiation: Prepare a 0.032mM DCSO aqueous solution and oscillate it ultrasonically for 1 minute. Place the prepared solution under a 365nm ultraviolet lamp for 30 seconds, and observe that the fluorescence color changes from yellow to blue under the ultraviolet lamp. Continue irradiating for 2 minutes, and observe that the fluorescence color has been quenched under the ultraviolet lamp. The response of the DCSO aqueous solution to light radiation is shown in the attached figure. Fig. 9 shown.

[0056] Example 2

[0057] Synthesis of DCSO: Under N2 protection, add compound A (0.55 mmol), acetonitrile (8 mL), K2CO3 (2.2 mmol) to a 50 mL round-bottom flask, then slowly drop a solution of compound B (1.38 mmol) in acetonitrile (10 mL), reflux at 90°C, and react overnight. After the reaction is complete, stop stirring. After cooling to room temperature, collect the organic phase, dry it, and spin dry it on a rotary evaporator. Purify the crude product by column chromatography, and collect the spin-dried product to obtain a yellow viscous liquid DCSO.

[0058] Example 3

[0059] Synthesis of DCSO: Under N2 protection, add compound A (0.55mmol), acetonitrile (8mL), K2CO3 (1.9mmol) to a 50mL round-bottom flask, then slowly drop a solution of compound B (1.24mmol) in acetonitrile (9mL), reflux at 80°C, and react overnight. After the reaction is complete, stop stirring. After cooling to room temperature, collect the organic phase, dry it, and spin dry it on a rotary evaporator. Purify the crude product by column chromatography, and collect the spin-dried product to obtain a yellow viscous liquid DCSO.

[0060] Those skilled in the art will readily appreciate other embodiments of the invention after considering the specification and practicing the invention herein. The invention is intended to cover any variations, uses or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art of the invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0061] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A supramolecular fluorescent material with multiple responses, characterized in that: The supramolecular fluorescent material is based on supramolecular self-assembly of DCSO molecules in water phase, and the chemical structure of DCSO is as follows:

2. The supramolecular fluorescent material with multiple responses according to claim 1, characterized in that: The DCSO has a temperature response characteristic in water, and the fluorescence luminescence of the DCSO blue-shifts as the temperature increases, and red-shifts as the temperature decreases.

3. The supramolecular fluorescent material with multiple responses according to claim 1, characterized in that: The DCSO has a solvent response characteristic. The fluorescence luminescence of the DCSO in the solvent red-shifts as the polarity of the solvent increases, and blue-shifts as the polarity of the solvent decreases.

4. The supramolecular fluorescent material with multiple responses according to claim 1, characterized in that: The DCSO has a humidity response characteristic, and the fluorescence luminescence of the DCSO blue-shifts as the humidity decreases, and red-shifts as the humidity increases.

5. The supramolecular fluorescent material with multiple responses according to claim 1, characterized in that: The DCSO has irradiation-responsive thermal properties in water, and the fluorescence luminescence of the DCSO blue-shifts as the ultraviolet light irradiation time increases, and is eventually quenched; the fluorescence color change rate of the DCSO aqueous solution under ultraviolet light irradiation is negatively correlated with the concentration of the DCSO aqueous solution.

6. The method for preparing the supramolecular fluorescent material with multiple responses according to claim 1, characterized in that: The DCSO is prepared by nucleophilic substitution of compound A and compound B, and the preparation process is as follows: ， Then, the DCSO is added into water, and self-assembly is driven by hydrophilic and hydrophobic forces to form the supramolecular fluorescent material.

7. The method for preparing a supramolecular fluorescent material with multiple responses according to claim 6, characterized in that: The preparation method of DCSO specifically comprises the following steps: Under N2 atmosphere, K2CO3, the compound A and acetonitrile were added to the flask, and then the acetonitrile solution of the compound B was slowly added dropwise. The mixture was stirred and refluxed at 80-90°C for 20-30h, then cooled and concentrated under reduced pressure, and purified by column chromatography to obtain a yellow viscous oily compound, which was the DCSO.

8. The method for preparing a supramolecular fluorescent material with multiple responses according to claim 7, characterized in that: The molar ratio of the K2CO3, the compound A and the compound B is (2.9-4):1:(2.0-2.5).

9. The method for preparing a supramolecular fluorescent material with multiple responses according to claim 6, characterized in that: The synthesis method of the compound A is as follows: starting from p-methoxyphenylacetonitrile, undergoing an electrophilic addition reaction with terephthalaldehyde and then undergoing demethylation to obtain the compound A; The synthesis method of the compound B is as follows: starting from triethylene glycol monomethyl ether, condensing with methyl trihydroxybenzoate to form ether, performing a reduction reaction to convert the ester group into a hydroxyl group, and finally reacting with TMSBr to obtain the compound B.

10. The method for preparing a supramolecular fluorescent material with multiple responses according to claim 6, characterized in that: The concentration of DCSO in distilled water is greater than 176 μM.

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