Preparation method and application of a temperature-stimulated responsive supramolecular artificial light-harvesting system

Abstract

The application relates to the field of supramolecular fluorescent materials, in particular to a preparation method and application of a temperature-stimulated supramolecular artificial light capturing system. The preparation method of the supramolecular artificial light capturing system comprises the following steps: under N2 protection, K2CO3 and the compound 1 are added into a flask provided with a magnetic stirrer, acetonitrile is used as a solvent, the compound 2 is slowly added dropwise, and the reaction is stirred at room temperature overnight; after the reaction is completed, the stirring is stopped, the organic phase is collected, dried, spin-dried by a rotary evaporator, column chromatography is carried out, the spin-dried product is collected, and the M in the form of sticky oil is obtained; the M is added into distilled water, and self-assembly is driven by hydrophilic and hydrophobic forces. The application discloses a preparation method and application of a new fluorescent adjustable and temperature-stimulated high-efficiency artificial light capturing system, and further prepares a temperature-controlled white light emitting material based on the temperature-variable artificial light capturing system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of supramolecular fluorescent materials, more particularly, it relates to a preparation method and application of a temperature-stimulated supramolecular artificial light-harvesting system. BACKGROUND

[0002] Solar energy has great potential as a clean, cheap and sustainable energy source, but in nature it must be captured by plants and converted into useful forms of energy. The most important way at present is through photosynthesis, which is also the basis of all life activities on earth. The process of photosynthesis includes two important steps, absorbing solar energy and converting solar energy into chemical energy. In the process of energy transfer, hundreds of chlorophyll molecules (complexes of chlorophyll, carotene, etc. with proteins) in the leaf are systematically composed of an efficient energy capture and transmission system, called light-harvesting system (LHS), which can effectively capture light and transmit excitation energy to the acceptor of the reaction center through multi-step energy transfer. Therefore, in the past few decades, as the first step of natural photosynthesis, the principle of light-harvesting system has been studied in depth. Supramolecular self-assembly has attracted the interest of many researchers due to its simple preparation and dynamic reversibility in constructing artificial light-harvesting systems.

[0003] It is well known that temperature has a great influence on photosynthesis. This is because the process of photosynthesis is an enzyme-controlled process, and enzymes only have high activity at the optimum temperature (i.e. 25-35℃). Due to the protein characteristics of enzymes, these enzymes generally lose function at temperatures above 40℃, so photosynthesis is inhibited under such higher temperature conditions. Revealing the relationship between light harvesting and temperature will promote research in this field, not only helping to study its mechanism, but also helping to stimulate its wide application in various fields. However, the existing technology mainly studies the process of energy transfer in light harvesting and the use of captured energy, without considering the impact of temperature on artificial systems, and even less research on the inhibition of light harvesting at high temperature. SUMMARY

[0004] The present disclosure provides a preparation method and application of a temperature-stimulated supramolecular artificial light-harvesting system, a new preparation method and application of a fluorescent adjustable and temperature-stimulated high-efficiency artificial light-harvesting system, and further preparation of a temperature-controlled white light emitting material based on the variable temperature artificial light-harvesting system.

[0005] In a first aspect, the present disclosure provides a temperature-stimulated supramolecular artificial light-harvesting system, which is based on supramolecular self-assembly of M (amphiphilic molecule) in aqueous solution, and the chemical structure of M is as follows:

[0006]

[0007] The first characteristic of M is that it is an amphiphilic molecule. Its molecule contains oligoethylene glycol (OEG) chains, which are hydrophilic segments, and cyanostilbene moieties, which are hydrophobic segments. When its tested concentration is above the critical aggregation concentration (CAC), and its transmittance is measured to be 125 μM, M will form spherical nanoassemblies driven by hydrophilic-hydrophobic interactions, at which point it exhibits blue fluorescence.

[0008] The second characteristic of M is that it contains a large number of triethylene glycol groups. At low temperatures, the oxygen atoms in these groups form a hydrogen bond network with water, resulting in a homogeneous phase. However, as the temperature increases, the hydrogen bonds are broken, leading to phase separation and subsequent turbidity of the solution. The temperature at which the solution's transmittance drops to half of its original transmittance is called the "cloud point," also known as the critical dissolution temperature (LCST). Therefore, M exhibits temperature-responsiveness.

[0009] The third characteristic of M is that it exists in water in different aggregate forms during the heating / cooling transition, thus exhibiting thermoresponsive fluorescence. When the solution is at 25°C, M molecules self-assemble into ordered nanospheres, with the cyanostilbene moieties tightly packed. This significantly enhances the confinement of intramolecular motion, resulting in strong blue light emission at 450 nm. As the temperature increases from 25°C to 50°C, the fluorescence intensity of M gradually decreases at 450 nm, while a new peak appears at 390 nm and gradually increases. Simultaneously, the fluorescence color changes from bright blue to bluish-violet. This is because the phase transition of the OEG chains during heating alters the self-assembly behavior of M, leading to a blue-shifted fluorescence.

[0010] The fourth characteristic of M is that its hydrophobic cyanostyrene group is an aggregation-induced emission (AIE) group, thus M exhibits aggregation-induced fluorescence enhancement due to nanoparticle formation. This property makes it possible to construct artificial light-harvesting systems. The amphiphilic dye 4,7-bis(2-thienyl)-benzo[2,1,3]thiadiazole (DBT) is loaded into M supramolecular nanoparticles via ultrasound. In this case, the M group acts as the energy donor (D), and DBT acts as the energy acceptor (A). When DBT is encapsulated within the confined space of the nanoparticle, the distance between the donor and acceptor is sufficiently close, creating conditions for fluorescence resonance energy transfer (FRET). Studies of the light-harvesting performance of this system revealed a good overlap between the absorption spectrum of DBT and the fluorescence spectrum of M. At a donor-acceptor ratio (D / A = 1:20), the energy transfer efficiency (Φ) is [missing value]. ET The efficiency can reach around 56.9%. However, in environments with higher temperatures of 50°C, energy transfer will decrease significantly.

[0011] The fifth feature of M is that the fluorescently tunable and temperature-responsive artificial light-harvesting system constructed by DBT can emit white light at room temperature, as shown in Figure 7 By changing the DBT content to 1.67% of M, (0.32, 0.31) close to white light emission is achieved in the CIE chromaticity diagram. After heating, there is a reversible transition from white light to light purple fluorescence, which is similar to the high temperature inhibition of natural photosynthesis, and demonstrates a kind of biomimetic stimulus-responsive light-harvesting system.

[0012] Preferably, M is prepared by electrophilic substitution of compound 1 and compound 2, and the chemical structure of compound 1 is as follows:

[0013]

[0014] The chemical structure of compound 2 is as follows:

[0015]

[0016] The reaction of compound 1 and compound 2 to generate M is as follows:

[0017]

[0018] In a second aspect, the present disclosure provides a preparation method of a temperature stimulus-responsive supramolecular artificial light-harvesting system, comprising the following steps:

[0019] (1) Under N2 protection, K2CO3 and compound 1 are added to a flask equipped with a magnetic stirrer, acetonitrile is used as the solvent, and compound 2 is slowly added dropwise, and the reaction is stirred at room temperature overnight;

[0020] (2) After the reaction is completed, stop stirring, collect the organic phase, dry, spin dry with a rotary evaporator, column chromatography, and collect the spin-dried product to obtain the viscous oil M;

[0021] (3) The M is added to distilled water, and self-assembly occurs driven by hydrophilic and hydrophobic forces.

[0022] Preferably, in step (3), the critical aggregation concentration of M is 125 μM, and M exists in the form of nanoscale assemblies.

[0023] Preferably, M has a low critical solution temperature behavior (LCST), and the cloud point temperature of the assembly of M in water is 39.3°C at a concentration of 625 μM. Above 39.3°C, the M solution becomes turbid, and below 39.3°C, the M solution becomes clear.

[0024] Preferably, the assembly of M emits blue fluorescence at room temperature, and the assembly of M emits purple fluorescence above 39.3°C.

[0025] Preferably, the LCST behavior of the M is adjustable, and the cloud point of the M decreases with the increase of the concentration, and the cloud point temperature of the M decreases from 42.6℃ to 36.5℃ when the concentration of the M increases from 78 μM to 2500 μM.

[0026] In a third aspect, the present disclosure provides an application of a temperature-stimulus-responsive supramolecular artificial light-harvesting system, which is applied to simulate photosynthesis.

[0027] Preferably, the application comprises the following steps:

[0028] The aqueous solution of the M is prepared, and the hydrophobic dye 4,7-di(2-thienyl)-benzo[2,1,3]thiadiazole (DBT) is loaded by using ultrasonic method, the M is used as a donor D, the DBT is used as an acceptor A, and the molar ratio of the donor to the acceptor D / A is 20:1-300:1.

[0029] Preferably, below the cloud point temperature, pure white light emission is prepared by regulating the DBT, above the cloud point temperature, white light emission is changed into light purple, and under the continuous cycle of cooling or heating, the fluorescence color is changed cyclically from white or light purple.

[0030] The light-harvesting system has temperature response performance, and the T c is 39.3℃, when the temperature of the system gradually increases to be higher than the T c , the assembly of the compound M will have a transition from regular shape to loose structure, the solution gradually becomes turbid with the gradual decrease of the transmittance, and the energy transfer efficiency between the donor and the acceptor also has a large decrease. Therefore, the control of the light-harvesting process can be realized objectively by controlling the increase and decrease of the temperature, and thus a reversible "light-harvesting switch" is successfully prepared.

[0031] In summary, the present application has the following beneficial effects:

[0032] 1. Since the M molecule in the present application contains a hydrophobic core and a hydrophilic end (polyethylene glycol ether chain) with temperature response, it is an amphiphilic molecule, and this design has a double-edged effect, that is, it can not only self-assemble in water, but also respond to temperature by LCST, and the M molecule exists in different aggregation forms in water during the heating or cooling transition, thereby having thermoresponsive fluorescence. In the process of gradually increasing the temperature, the M shows obvious blue shift, and this feature can be used for temperature visualization.

[0033] 2. In this application, M uses the cyanostilbene moiety of the AIE group as a hydrophobic core, which enables M to have enhanced fluorescence emission after being assembled into regular assembled nanospheres. After disassembly, the fluorescence intensity will decrease significantly, which perfectly matches the design requirement of "heating-induced disassembly, thereby inhibiting light-harvesting ability". The assembly of M can load the acceptor DBT to carry out the FRET process. When the acceptor ratio D / A is 1 / 20, the energy transfer efficiency can be improved.

[0034] 3. The temperature-stimuli-responsive light-harvesting system constructed by M in this application can achieve objective control over the light-harvesting effect by artificially adjusting the ambient temperature.

[0035] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the scope of protection of this disclosure. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the technical solution of this application;

[0037] Figure 2 It is the nuclear magnetic resonance hydrogen of compound M ( 1 H NMR spectrum;

[0038] Figure 3 This is the high-resolution mass spectrum of compound M, [M+Na]. + =820.3855;

[0039] Figure 4 The figures are system temperature response diagrams determined by transmittance experiments, (a) is the cloud point measurement diagram, and (b) is the temperature response cycle diagram.

[0040] Figure 5 This is the thermal response fluorescence spectrum of M;

[0041] Figure 6 This is an energy transfer diagram of M versus DBT;

[0042] Figure 7 This is the white light emission pattern of M@DBT. Detailed Implementation

[0043] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0044] Example

[0045] Example 1

[0046] The application of a temperature-responsive supramolecular artificial light-harvesting system includes the following steps:

[0047] (1) Synthesis of M: In a 100 mL three-necked flask, K2CO3

[0048] (0.10 g, 0.72 mmol), compound 1 (0.11 g, 0.50 mmol) was added, dry MeCN (5 mL) was added, 2 was added dropwise slowly under stirring, the reaction was stirred at room temperature for 24 h. The reaction was finished, the stirring was stopped. The organic phase was collected, dried, rotary evaporator was used to dry, column chromatography was used to collect and dry the product, yellow viscous liquid M was obtained. The nuclear magnetic resonance spectrum of hydrogen of M is shown in Figure 1, and the high-resolution mass spectrum is shown in Figure 2. Figure 2 Figure 3

[0049] (2) M molecules self-assemble in distilled water driven by hydrophilic and hydrophobic interaction, the critical aggregation concentration of M is 125 μM, above which M assembles into nanoparticles.

[0050] (3) M molecules have temperature response due to the polyethylene glycol ether chain with temperature response, a 625 μM aqueous solution of M is prepared, the cloud point temperature T c is 39.3°C under this condition. The temperature response in this step is reversible, and can be cycled more than 5 times, as shown in Figure 3. Figure 4

[0051] (4) A 250 μM aqueous solution of M is prepared, and the hydrophobic dye 4,7-bis(thienyl-2-)-benzothiadiazole DBT is loaded by ultrasonic method, M groups act as energy donors (D), and DBT acts as energy acceptors (A), a donor-acceptor solution with a donor-acceptor molar ratio of D / A = 1:20 is prepared, and the fluorescence spectrum is measured, and the Φ ET is 56.9%, as shown in Figure 4. Figure 6

[0052] (5) A 250 μM aqueous solution of M is prepared, and 4.17 μM of the hydrophobic dye 4,7-bis(thienyl-2-)-benzothiadiazole DBT is loaded by ultrasonic method, white light emission is realized at room temperature, and the calculation in the CIE diagram is (0.31, 0.32), the fluorescence spectrum is measured under this condition, and the energy transfer efficiency is 43.9%. As shown in Figure 5. Figure 7

[0053] In this embodiment, the ultrasonic instrument used is a laboratory commonly used ultrasonic cleaner, and the frequency is 40 kHz.

[0054] Example 2

[0055] ​​​​​The application of a temperature stimulus responsive supramolecular artificial light-harvesting system, in this embodiment, the temperature response of M was determined, M molecules have a temperature response due to the polyethylene glycol ether chain with temperature response, M was prepared in a 625 μM aqueous solution, at 25°C, M molecules self-assembled into ordered nanospheres, with cyanostilbene moieties tightly packed, intramolecular motion limited, with strong emission at 450 nm, bright blue fluorescence emission. As the temperature increased from 25°C to 50°C, the fluorescence intensity of M gradually decreased at 450 nm, while a new peak appeared at 390 nm and gradually increased. At the same time, the fluorescence color changed from bright blue to blue-violet, as shown in Figure 5 .

[0056] Example 3

[0057] The application of a temperature stimulus responsive supramolecular artificial light-harvesting system prepared according to the method of Example 2, except that in this embodiment, the supramolecular polymer formed by compound M was used as the energy donor, and the fluorescent dye DBT was used as the acceptor, and the preparation method was as follows:

[0058] Step 1: Prepare an aqueous solution of M, load DBT using ultrasonic method, prepare a donor / acceptor solution with A / D = 1:20, ultrasonic for 10 min, shake during the process, measure the fluorescence intensity of the sample using a fluorescence spectrophotometer;

[0059] Step 2: Prepare a 250 μM aqueous solution of M, load DBT using ultrasonic method, prepare a donor / acceptor solution with A / D = 1:60, ultrasonic for 10 min, shake during the process, measure the fluorescence intensity of the sample using a fluorescence spectrophotometer;

[0060] Step 3: Prepare a 250 μM aqueous solution of M, load DBT using ultrasonic method, prepare a donor / acceptor solution with A / D = 1:75, ultrasonic for 10 min, shake during the process, measure the fluorescence intensity of the sample using a fluorescence spectrophotometer;

[0061] Step 4: Prepare a 250 μM aqueous solution of M, load DBT using ultrasonic method, prepare a donor / acceptor solution with A / D = 1:100, ultrasonic for 10 min, shake during the process, measure the fluorescence intensity of the sample using a fluorescence spectrophotometer;

[0062] Step 5: Prepare a 250 μM aqueous solution of M, load DBT using ultrasonic method, prepare a donor / acceptor solution with A / D = 1:300, ultrasonic for 10 min, shake during the process, measure the fluorescence intensity of the sample using a fluorescence spectrophotometer;

[0063] The solution ratios described in the above steps are D / A = 20 / 1, 60 / 1, 75 / 1, 100 / 1, 300 / 1, respectively, and the combined fluorescence spectrum is shown in Figure 6 .

[0064] Example 4

[0065] Energy transfer efficiency calculation:

[0066] The fluorescence spectra of M and DBT@M in Example 3 were measured under 355 nm excitation, respectively;

[0067] Energy transfer efficiency (Φ ET ) was calculated by equation S1:

[0068] Φ ET = 1 - I DA / I D (eq. S1)

[0069] where I DA and I D are the fluorescence intensities of DBT@M (donor and acceptor) and M (donor) at 450 nm under 355 nm excitation, respectively, where [M] = 2.5 x 10 -4 mol / L, [DBT] = 8.3 x 10 -7 mol / L. The data were substituted into equation S1 to obtain the energy transfer efficiency of energy transfer of D / A = 1:20 was 56.9%.

[0070] Example 5

[0071] The application of the temperature-stimulated supramolecular artificial light-harvesting system prepared according to the method of Example 3 was different, except that a 250 μM aqueous solution of M was prepared in step (1), DBT was loaded by ultrasonic method, a donor-acceptor solution of D / A = 60:1 was prepared, and the fluorescence spectrum was measured to obtain Φ ET 43.9%.

[0072] Example 6

[0073] The application of the temperature-stimulated supramolecular artificial light-harvesting system prepared according to the method of Example 3 was different, except that a 250 μM aqueous solution of M was prepared in step (1), DBT was loaded by ultrasonic method, a donor-acceptor solution of D / A = 75:1 was prepared, and the fluorescence spectrum was measured to obtain Φ ET 40.3%.

[0074] Example 7

[0075] The application of the temperature-stimulated supramolecular artificial light-harvesting system prepared according to the method of Example 3 was different, except that a 250 μM aqueous solution of M was prepared in step (1), DBT was loaded by ultrasonic method, a donor-acceptor solution of D / A = 100:1 was prepared, and the fluorescence spectrum was measured to obtain Φ ET 31.0%.

[0076] Example 8

[0077] The application of the temperature-stimulated supramolecular artificial light-harvesting system prepared according to the method of Example 3, except that a 250 μM aqueous solution of M was prepared, DBT was loaded by ultrasonic method, a donor / acceptor (D / A) ratio of 300:1 was prepared, and the fluorescence spectrum was measured, and Φ ET was 21.5%.

[0078] Example 9

[0079] A 250 μM aqueous solution of M was prepared, and the hydrophobic dye 4,7-di(thienyl-2-)-benzothiadiazole (DBT) was loaded by ultrasonic method. When the content of DBT was 1.67% of M, (0.32, 0.31) close to white light emission was achieved in the CIE chromaticity diagram. After heating, a transition from white light to light purple fluorescence occurred, and the fluorescence color was reversible with temperature change.

[0080] The above merely describes exemplary specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present disclosure, and such changes or replacements should be encompassed within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A temperature-responsive supramolecular artificial light-harvesting system, characterized in that, The temperature-responsive supramolecular light-harvesting system is based on the supramolecular self-assembly of an amphiphilic molecule M in an aqueous phase, the chemical structure of which is as follows: The supramolecular artificial light-harvesting system uses M as the donor D and 4,7-bis(2-thienyl)-benzo[2,1,3]thiadiazole (DBT) as the acceptor A, with a molar ratio of donor D to acceptor A of 20:1-300:

1.

2. The temperature-responsive supramolecular artificial light-harvesting system according to claim 1, characterized in that, M is prepared by electrophilic substitution of compound 1 and compound 2, and the chemical structure of compound 1 is as follows: ； The chemical structure of compound 2 is as follows: ； The reaction formula for the formation of M from the reaction of compound 1 and compound 2 is as follows: 。 3. The method for preparing a temperature-responsive supramolecular artificial light-harvesting system according to claim 2, characterized in that, Includes the following steps: (1) Under N2 protection, K2CO3 and compound 1 were added to a flask equipped with a magnetic stirrer, and compound 2 was slowly added dropwise using acetonitrile as solvent. The mixture was stirred at room temperature and reacted overnight. (2) After the reaction is complete, stop stirring, collect the organic phase, dry it, evaporate it using a rotary evaporator, perform column chromatography, and collect the evaporated product to obtain the viscous oily substance M; (3) Add the M to distilled water, and self-assembly is driven by hydrophilic-hydrophobic interaction; (4) The hydrophobic dye 4,7-bis(2-thienyl)-benzo[2,1,3]thiadiazole (DBT) was loaded using the ultrasonic method.

4. The method for preparing a temperature-responsive supramolecular artificial light-harvesting system according to claim 3, characterized in that, In step (3), the critical aggregation concentration of M is 125 μM, and M exists in the form of nano-assemblies.

5. The method for preparing a temperature-responsive supramolecular artificial light-harvesting system according to claim 3, characterized in that, The M exhibits low critical solution temperature (LCST) behavior, with the turbidity point of the M assembly in water being 39.3°C at a concentration of 625 μM. Above 39.3°C, the M solution becomes turbid, and below 39.3°C, the M solution becomes clear.

6. The method for preparing a temperature-responsive supramolecular artificial light-harvesting system according to claim 3, characterized in that, The assembly of M exhibits blue fluorescence at room temperature and purple fluorescence at temperatures above 39.3°C.

7. The method for preparing a temperature-responsive supramolecular artificial light-harvesting system according to claim 5, characterized in that, The LCST behavior of M is adjustable, and the cloud point of M decreases as the concentration increases. When the concentration of M increases from 78 μM to 2500 μM, the cloud point temperature of M decreases from 42.6 °C to 36.5 °C.

8. The application of the temperature-stimulation-responsive supramolecular artificial light-harvesting system prepared by the method according to any one of claims 3-7, characterized in that, The temperature-responsive supramolecular artificial light-harvesting system is applied in the simulation of photosynthesis.

9. The application of the temperature-responsive supramolecular artificial light-harvesting system according to claim 8, characterized in that, Pure white light emission was prepared by controlling DBT below the cloud point temperature. Above the cloud point temperature, the white light emission turned into pale purple. With continuous cooling or heating cycles, the fluorescence color changed cyclically from white to pale purple.

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