Preparation of a heat-sensitive three-step cascade light harvesting system and its photocatalytic application

Abstract

The application discloses a kind of thermosensitive three-step cascade light trapping systems and its preparation method and application, the system is formed by the nanometer particle of amphiphilic molecule TPEG, Eosin Y, Nile red and chlorophyll e6 with low critical solution temperature characteristics by ultrasonic self-assembly.The three-step energy transfer cascade path of TPEG→Eosin Y→Nile red→chlorophyll e6 is realized by the hydrophobic nanocavity constructed by TPEG.The temperature control response of energy transfer path is realized using the temperature control phase change characteristics of TPEG.Meanwhile, based on the redox potential of chlorophyll e6, under light induction, dual active oxygen species of ¹O₂ and O₂•⁻ are generated, forming a multi-dimensional synergistic catalytic mechanism.The system of the application shows excellent energy transfer efficiency and photocatalytic activity under mild conditions, significantly improves the conversion yield of amidation and Schiff base synthesis reaction, and has good thermal response reversibility and mechanical stability, providing a new strategy for the design of artificial photocatalytic system.

Description

Technical Field

[0001] This invention belongs to the fields of organic light-emitting materials and supramolecular photocatalysis, specifically relating to the preparation of a thermosensitive three-step cascade light-harvesting system and its photocatalytic application. Background Technology

[0002] Artificial light-harvesting systems achieve efficient energy capture and directional transport by mimicking the ordered assembly of pigment molecules in natural photosynthesis. Despite significant progress in this field, several bottlenecks remain in current research.

[0003] Regarding the number of energy transfer steps, existing researchers, such as Zhang Dengqing et al., have reported a three-step cascaded artificial light-harvesting system using an AIE active metal ring as the light-harvesting antenna, eosin Y (ESY) and sulforhodamine 101 (SR101) as relays, and near-infrared chlorophyll e6 (Ce6) as the final acceptor (MTPEPt1 → ESY → SR101 → Ce6). This system achieves efficient three-step sequential energy transfer through close contact and spectral overlap between donor and acceptor molecules. However, this system has the following shortcomings: (1) The donor is a metal ring structure containing the precious metal platinum, resulting in high material costs and the risk of metal residue; (2) This system does not involve any photocatalytic applications, and the energy is ultimately used only to generate singlet oxygen (…). 1 (2) The system lacks the utilization of free radical species such as superoxide anion (O2•-); (3) The system does not have temperature response reversibility and cannot achieve environmental adaptive adjustment of the energy transfer path.

[0004] In the field of photocatalysis, existing researchers such as Sun Guangping et al. have constructed a three-step cascaded light-harvesting system based on the cationic column [5] aromatic CP5-TPESF-DBT-SR101-Ce6, which is excited by energy transfer to Ce6. 1 O2 was used to achieve the photo-oxidation of 4-(methylthio)toluene (yield 89%). However, the donor of this system is a macrocyclic columnar aromatic hydrocarbon rather than a nonlinear amphiphilic molecule, so it also lacks temperature responsiveness, and the catalytic reaction is limited to the oxidation of thioethers, making it difficult to extend to more complex C–N bond construction reactions.

[0005] It is evident that existing technologies still face significant bottlenecks in three areas: "precise construction of cascaded pathways," "intelligent regulation of environmental response," and "multi-dimensional synergistic catalytic mechanisms." In particular, existing systems often rely on metal complexes as light-harvesting antennas, posing a risk of heavy metal residue and exhibiting limited functionality. Therefore, developing an intelligent light-harvesting system based on purely organic amphiphilic molecules, possessing dynamic environmental response capabilities, and capable of driving dual reactive oxygen species synergistic catalysis, is of significant scientific value and practical application importance for reducing the energy barrier of photocatalytic synthesis and improving the efficiency of green manufacturing. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a three-step cascaded biomimetic light-harvesting system based on the thermosensitive amphiphilic molecule TPEG and its preparation method. This system employs a confined assembly strategy to precisely arrange receptor chromophores within nanocavities, constructing an efficient three-step energy transfer pathway. Furthermore, the temperature-controlled phase transition properties of TPEG enable real-time opening and closing control of the energy transfer pathway. Simultaneously, by introducing the redox-active tertiary receptor Ce6, photoinduced generation is promoted. 1 The dual reactive oxygen species O2 and O2•- form a multidimensional synergistic catalytic mechanism, which significantly reduces the conversion energy barrier of organic reactions under mild conditions and achieves nonlinear enhancement of photocatalytic synthesis efficiency.

[0007] A thermosensitive three-step cascaded light-harvesting system, wherein the system is formed into nanoparticles by ultrasonic self-assembly of an amphiphilic molecule TPEG with low critical solution temperature characteristics, a first energy acceptor eosin YESY, a second energy acceptor Nile red NiR, and a third energy acceptor chlorophyll e6Ce6.

[0008] The molar ratio of TPEG, ESY, NiR and Ce6 in the nanoparticles is 1000 : 10~40 : 10~40 : 10~40;

[0009] The system forms uniform nanoparticles through ultrasonic treatment, driven by hydrophobic interaction, so that the average center-to-center distance of each molecule is controlled within 10 nm.

[0010] Under ultraviolet light excitation, the system forms a three-step continuous fluorescence resonance energy transfer cascade path, namely TPEG→ESY→NiR→Ce6, through the FRET effect.

[0011] Preferably, the amphiphilic molecule TPEG comprises a hydrophobic fluorescent group tetraphenylethylene as the parent core and a temperature-responsive methoxy-terminated oligoethylene glycol linked by a phenoxy group as a hydrophilic chain.

[0012] The structural formula of the TPEG is:

[0013] .

[0014] Preferably, the critical aggregation concentration of the amphiphilic molecule TPEG is 38 μM, and the TPEG forms nanoparticles through self-assembly in the aqueous phase; the cloud point temperature of the TPEG at concentrations of 38 μM to 200 μM is 32 to 37 °C.

[0015] Preferably, when the molar ratio of TPEG, ESY, NiR and Ce6 in the nanoparticles is 1000:40:40:40, the system achieves the optimal three-step cascaded fluorescence resonance energy transfer efficiency.

[0016] Preferably, the system has thermal response reversibility, and after at least 20 heating / cooling cycles between 25 °C and 60 °C, the nanoparticle assembly structure remains stable and can recover to its initial temperature response behavior.

[0017] Preferably, when the temperature rises, the oligoethylene glycol segments in the TPEG break through the hydrogen bonds between OEG and water molecules, causing the molecular chains to dehydrate and collapse, resulting in the disaggregation of nanoparticles and temporarily interrupting the FRET cascade energy transfer path; when the temperature decreases, OEG and water molecules reassociate, the nanoparticles reassemble, and the FRET cascade path is restored.

[0018] Preferably, when the third-level energy acceptor Ce6 receives excited-state energy from the second-level energy acceptor NiR, it can promote the generation of two reactive oxygen species, singlet oxygen and superoxide anion, through a photoinduced process.

[0019] This invention also provides a method for preparing the above system, comprising the following steps:

[0020] S1: Dissolve the amphiphilic molecule TPEG in deionized water to prepare a concentration of 3.8 × 10⁻⁶. -5 M~1×10 -3 The solution of M was subjected to ultrasonic treatment at 40 kHz for 2-3 min to induce TPEG self-assembly into nanoparticles.

[0021] S2: Add the first-level energy acceptor ESY to the TPEG nanoparticle solution, and sonicate again at 40 kHz for 2-3 min to form a TPEG-ESY complex.

[0022] S3: Add the secondary energy acceptor NiR to the TPEG-ESY complex, and sonicate again at 40 kHz for 2-3 min to form the TPEG-ESY-NiR complex;

[0023] S4: Add Ce6, the third-level energy acceptor, to the TPEG-ESY-NiR complex, and sonicate again at 40 kHz for 2-3 min to finally form the TPEG-ESY-NiR-Ce6 system.

[0024] The present invention also provides an application of the aforementioned thermosensitive three-step cascade light-harvesting system in photocatalytic organic reactions, wherein the system is used to catalyze amidation reactions, Schiff base synthesis reactions, or other similar photocatalytic organic synthesis reactions involving reactive oxygen species.

[0025] Preferably, the photocatalytic method includes the following steps:

[0026] Step 1: Prepare the light-harvesting system, wherein the light-harvesting system contains an aqueous solution of TPEG with a concentration of 0.5 mM; add the organic substrate to be catalyzed to the light-harvesting system and mix thoroughly;

[0027] Step 2: Under irradiation with a 365-375 nm ultraviolet lamp, react at room temperature for 18 h;

[0028] Step 3: Detect and collect the product by chromatography.

[0029] The above technical solution has the following advantages or beneficial effects:

[0030] (1) This invention constructs a three-step continuous cascaded energy transport network by confined assembly of the amphiphilic molecule TPEG, orderly arranging ESY, NiR, and Ce6 in a nanocavity, realizing unidirectional energy transfer from the donor to the tertiary acceptor. Compared with traditional physical mixing systems, it greatly reduces the nonradiative energy transition loss, successfully breaks the limitation of the number of energy transfer steps, and provides sufficient excited-state energy for subsequent complex catalytic reactions.

[0031] (2) The LCST characteristic of the OEG chain in the TPEG molecule of this invention endows the system with environmental responsiveness, realizing dynamic intelligent path control based on hydrogen bond breaking. When the temperature rises, the OEG chain dehydrates and collapses, causing the particles to disassemble and interrupting the cascade path in real time. This mechanism deeply couples catalytic activity with the system structure state, realizing temperature-controlled responsive regulation of photocatalytic reactions, and exhibiting flexibility superior to static systems.

[0032] (3) This invention, through the unique electrochemical activity of Ce6, promotes the development of... 1 The three-step system generates two reactive oxygen species, O2 and O2•-. Examples show that the three-step system exhibits a higher O2•- yield compared to the two-step system. Both reactive oxygen species participate in the substrate activation process, achieving a bidirectional reduction of the energy barrier for the transition state of the organic reaction, demonstrating significant synergistic catalytic characteristics. Specifically, at a moderate energy transfer efficiency of 60.6%, a photocatalytic conversion yield as high as 91% is achieved, breaking through the traditional design approach of light-harvesting systems that solely rely on high energy transfer efficiency. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention, wherein:

[0034] Figure 1This is a schematic diagram illustrating the construction and application of the temperature-responsive three-step continuous light-harvesting system of the present invention. It shows the chemical structure of the thermosensitive amphiphilic molecule TPEG, the supramolecular self-assembly process, the three-step cascade energy transfer pathway, the dynamic response of the structure at different temperatures, and the dual reactive oxygen generation mechanism. It also summarizes the entire process of photocatalytic application.

[0035] Figure 2 The image shows the 1H NMR spectrum of the compound TPEG.

[0036] Figure 3 The image shows the carbon NMR spectrum of the compound TPEG.

[0037] Figure 4 This is the high-resolution mass spectrum of the compound TPEG;

[0038] Figure 5 This is a graph showing the critical aggregation concentration (CAC) of compound TPEG. Figure 5 (a) Curve showing the change in transmittance of the system as the TPEG concentration increases; Figure 5 (b) The critical aggregation concentration (CAC) of TPEG was determined to be 38 μM by bilinear fitting, and the difference in Tyndall effect before and after assembly was shown, demonstrating the formation conditions of nanoparticles.

[0039] Figure 6 This is a temperature response curve obtained from the transmittance experiment of compound TPEG. Figure 6 (a) The change in transmittance of TPEG solution with increasing temperature (cloud point test) visually demonstrates the LCST behavior; Figure 6 (b) A series of 20 heating / cooling cycles demonstrated that the system has excellent thermal response reversibility and structural stability;

[0040] Figure 7 The temperature-response fluorescence emission spectrum of compound TPEG is shown. Figure 7 (a) The changes in fluorescence emission intensity of TPEG nanoparticles at different temperatures from 20 to 60 °C reflect the effect of temperature on energy transfer state; Figure 7 (b) The fluorescence recovery performance of TPEG nanoparticles after 20 heating / cooling cycles between 20 °C and 60 °C was demonstrated. The results showed that the fluorescence emission intensity did not decrease significantly, which reflects the high stability and high reproducibility of the TPEG support structure.

[0041] Figure 8 This is a schematic diagram of the three-step continuous energy transfer of the compound TPEG. Figure 8 (a, c, e) show the redshift and cascade characteristics of fluorescence emission spectra after gradually loading ESY, NiR, and Ce6 onto nanoparticles, respectively; Figure 8(b, d, f) The overlap between the donor emission spectrum and the acceptor absorption spectrum demonstrates that the components have an energy level matching degree that enables efficient FRET.

[0042] Figure 9 Capture of compound TPEG 1 UV absorption spectrum of O2;

[0043] Figure 10 UV absorption spectrum of compound TPEG capturing O2•-;

[0044] Figure 11 The photocatalytic yield of the light-harvesting system (TPEG / ESY / NiR / Ce6) under different temperature conditions was determined.

[0045] Figure 12 The yield of photocatalysis in the light-harvesting system (TPEG / ESY / NiR / Ce6) after multiple heating / cooling cycles is given. Detailed Implementation

[0046] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0047] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0048] Example 1

[0049] (1) Synthesis and structural characterization of compound TPEG

[0050] In this embodiment, compound TPEG was synthesized using compound 1 as a raw material. The structural formula of compound 1 is shown below:

[0051] ;

[0052] Under a nitrogen atmosphere, 1.10 g of potassium carbonate (7.9 mmol), 1.83 g of compound 1 (5.3 mmol), and 20 mL of acetonitrile solution were added to a three-necked flask.

[0053] Subsequently, 2.60 g (5.3 mmol) of p-toluenesulfonic acid hexaethylene glycol monoester was dissolved in 10 mL of acetonitrile, and the resulting solution was slowly added dropwise to the above reaction system.

[0054] After the addition was complete, the reaction system was heated to reflux and stirred continuously for 24 hours. After the reaction was completed, the reaction solution was naturally cooled to room temperature, and the solvent was removed by rotary evaporation under reduced pressure to obtain the crude product.

[0055] The crude product was further purified by silica gel column chromatography to obtain a pale yellow viscous oily compound, TPEG (3.02 g, 4.77 mmol, yield 90%).

[0056] The 1H NMR spectrum of compound TPEG is as follows: Figure 2 As shown:

[0057] The carbon NMR spectrum of compound TPEG is as follows: Figure 3 As shown:

[0058] High-resolution mass spectra of compound TPEG, such as Figure 4 As shown:

[0059] Based on the above experimental characterization results, the structure of the synthesized compound TPEG was determined to be:

[0060] .

[0061] (2) Fabrication and physical property evaluation of supramolecular nanoparticle antennas

[0062] In this embodiment, the fluorescent antenna is obtained by self-assembly of the compound TPEG, and the preparation process includes the following steps:

[0063] The compound TPEG was dissolved in deionized water to prepare a concentration of 1×10⁻⁶. -4 The solution of M was continuously sonicated for 3 min using a 40 kHz ultrasonic processor, causing it to self-assemble into stable, uniform nanoparticles driven by hydrophilic-hydrophobic interactions. The TPEG concentration was 1 × 10⁻⁶. -4 At time M, the average particle size of the nanoparticles was 78±8 nm, and the polydispersity index (PDI) was 0.18, indicating a narrow particle size distribution and good particle size uniformity.

[0064] like Figure 5 As shown, when the TPEG concentration is higher than 38 μM, it can self-assemble into nanoparticles in the aqueous phase. When the concentration is lower than 38 μM, TPEG exists in the form of single molecules and cannot construct an effective hydrophobic cavity. When the concentration reaches or exceeds 38 μM, the system self-assembles into stable nanoparticles, which can effectively load chromophores and realize cascade energy transfer.

[0065] Tests revealed that the system exhibits a low critical solution temperature (LCST) characteristic. At a concentration of 200 μM, the cloud point temperature is 35.0 °C. Below this temperature, OEG chains associate with water molecules through hydrogen bonds to form a hydration layer, resulting in a transparent system. Above this temperature, hydrogen bonds break, molecular chains dehydrate and collapse, inducing phase separation and leading to a significant decrease in transmittance. The temperature at which the solution transmittance decreases to 50% of its initial value is defined as the cloud point temperature, i.e., the low critical solution temperature (LCST). This characteristic endows TPEG with excellent temperature response behavior. Please refer to [reference needed]. Figure 6 , Figure 6 The temperature response curve was obtained from the TPEG transmittance experiment, where... Figure 6 (a) is a graph showing the determination of cloud point temperature. Figure 6 (b) is a temperature response cyclic test graph.

[0066] Transmittance and fluorescence intensity measurements confirmed that after 20 heating / cooling cycles within the temperature range of 25 °C to 60 °C, the fluorescence recovery rate still exceeded 98%, demonstrating excellent thermal reversibility. Figure 7 As shown, when the temperature is increased to 60.0℃, the fluorescence emission intensity decreases significantly compared to the initial value; when the system is cooled to room temperature, its fluorescence emission can quickly recover to the initial level, indicating that the system has excellent thermal reversibility and fluorescence stability.

[0067] (3) Construction of a three-step cascaded light-harvesting system and optimization of energy transfer path

[0068] This step aims to achieve optimal matching of the energy gradient by precisely controlling the molar ratio of the donor to the acceptor.

[0069] Using the TPEG nanoparticles prepared in step (2) as the energy donor, Eosin Y (ESY) as the first-step energy acceptor A1, Nile Red (NiR) as the second-step energy acceptor A2, and Chlorophyll e6 (Ce6) as the third-step energy acceptor A3, a three-step continuous light-harvesting system was constructed. The specific preparation method is as follows:

[0070] A 100 μM TPEG aqueous solution was prepared and firstly sonicated for 2 min to induce self-assembly of TPEG nanoparticles. Then, ESY was added to the nanoparticle solution, and the mixture was sonicated again for 2 min to load and form TPEG-ESY composite nanoparticles. Next, NiR was added, and the mixture was sonicated again for 2 min to form TPEG-ESY-NiR composite nanoparticles. Finally, Ce6 was added, and the mixture was sonicated again for 2 min with intermittent oscillation to achieve the final TPEG-ESY-NiR-Ce6 composite nanoparticles, with a donor-acceptor molar ratio of D / A1 / A2 / A3 = 1000:40:40:40. The fluorescence emission intensity of the samples at each stage was then measured using a fluorescence spectrophotometer.

[0071] Fluorescence spectroscopy analysis revealed that adding the fluorescent dye ESY to the supramolecular nanoparticles of TPEG, such as... Figure 8 As shown in (a), the fluorescent color gradually changes from blue to green. Figure 8 (b) shows that the absorption wavelength of TPEG and the emission wavelength of ESY overlap to a certain extent, which ensures that fluorescence resonance energy transfer can occur to form TPEG-ESY.

[0072] Adding the fluorescent dye NiR to the supramolecular nanoparticles of TPEG-ESY, such as... Figure 8 As shown in (c), the fluorescent color gradually changes from green to red. Figure 8 As shown in (d), the absorption wavelength of TPEG-ESY and the emission wavelength of NiR overlap to a certain extent, which ensures that fluorescence resonance energy transfer can occur to form TPEG-ESY-NiR.

[0073] Adding the fluorescent dye Ce6 to the supramolecular nanoparticles of TPEG-ESY-NiR, such as... Figure 8 As shown in (e), the fluorescent color gradually changes from red to orange. Figure 8 (f) shows that the absorption wavelength of TPEG-ESY-NiR and the emission wavelength of Ce6 overlap to a certain extent, which ensures that fluorescence resonance energy transfer can occur to form TPEG-ESY-NiR-Ce6.

[0074] Under the condition that the donor-acceptor ratio D / A1 / A2 / A3 = 1000:40:40:40, the system can achieve efficient three-step continuous energy transfer, and the three-level cascade energy transfer efficiency can reach up to 60.6%.

[0075] In this embodiment, the instrument used for ultrasound is a conventional laboratory ultrasonic cleaner with a working frequency of 40 kHz.

[0076] Under 40 kHz ultrasonic oscillation, TPEG nanoparticles provide hydrophobic nanocavities, driving the distribution of dye molecules from the aqueous phase to the hydrophobic core. This process not only achieves dye solubilization but also precisely controls the average center-to-center distance of the four molecules within the effective distance (<10 nm) required for FRET to occur through hydrophobic repulsion. This distance range corresponds precisely to the effective transfer distance of FRET (R0≈5-10 nm). Only within this distance range can efficient three-step cascaded energy transfer be achieved, ensuring the unidirectional flow of electronic excited state energy driven by the molecular energy level gradient (TPEG→ESY→NiR→Ce6).

[0077] The preparation methods for other different donor-acceptor ratios "D / A1 / A2 / A3 = 1000 / 40 / 40 / 5, 1000 / 40 / 40 / 10, 1000 / 40 / 40 / 20, 1000 / 40 / 40 / 30, and 1000 / 40 / 40 / 40" are the same as described above. Table 1 below compares the FRET efficiency and photocatalytic performance under different donor-acceptor molar ratios.

[0078] Table 1 Comparison of FRET efficiency and photocatalytic performance under different donor-acceptor molar ratios

[0079]

[0080] The significant increase in yield did not stem from a simple increase in the number of energy transfer steps, but rather from the complete cascaded path constructed after the introduction of Ce6. This specific path induced the generation of… 1 The dual reactive oxygen species, with O2 and O2•- working synergistically, achieve precise activation of the transition state in the amidation reaction.

[0081] The two-step system without Ce6 (TPEG / ESY / NiR, molar ratio 1000:40:40, total acceptor concentration 80 μM) exhibited a catalytic yield of 68% (see Table 2, item 9), with a FRET efficiency of 44.2%. Compared to the two-step system without Ce6, the three-step system (molar ratio 1000:40:40:40, total acceptor concentration 120 μM) showed a 16.4 percentage point increase in FRET efficiency and a 23 percentage point increase in yield. The yield improvement significantly exceeded the FRET efficiency improvement, indicating that the advantage of the three-step system stems not only from the increased acceptor concentration but also from the complete three-level cascade pathway established after the introduction of Ce6 and the resulting... 1 The synergistic catalytic effect of O2 and O2•- dual reactive oxygen species. If the yield increase is driven solely by the increase in concentration, the yield increase should be comparable to the increase in FRET efficiency. However, the actual data deviates from this linear relationship, demonstrating the non-obviousness of the three-step cascade design.

[0082] Example 2

[0083] Compound 9,10-anthratridiyl-bis(methylene)dimalonic acid (ABDA) was used as the detection agent in aqueous solution. 1 O2 indicator. Dissolve 50 µM photocatalyst in 3.0 mL of aqueous solution containing 0.5 mM ABDA. Then place the mixture in a cuvette and irradiate with a 3-5W UV lamp.

[0084] The compound N,N,N′,N′-tetramethylphenylenediamine (TMPD) was used as an indicator for the detection of O2•- in aqueous solution. 50 µM of the photocatalyst was dissolved in 3.0 mL of a solution containing 0.5 mM TMPD. The mixture was then placed in a cuvette and irradiated with a 10 W UV lamp.

[0085] The photocatalysts are: TPEG-ESY-NiR-Ce6, TPEG-ESY-NiR, TPEG-ESY, TPEG, ESY-NiR-Ce6, and a blank control. The photocatalysts were prepared as described in Example 3.

[0086] Different catalysts produce 1 O2 levels were recorded using a UV-Vis absorption spectrophotometer, and the absorbance change (A0-A) at 397 nm was used for further analysis. Results are as follows: Figure 9 As shown, the absorption intensity of ABDA gradually increases with increasing irradiation time.

[0087] The generation of O2•- by different catalysts was recorded using a UV-Vis spectrophotometer, and the change in absorbance at 561 nm (A-A0) was used for further analysis. The results are as follows: Figure 10 As shown, the absorption intensity of TMPD gradually increases with increasing irradiation time.

[0088] Under ultraviolet light excitation, a cascaded energy transfer funnel was constructed. The introduction of the terminal acceptor Ce6 not only completed the energy capture process but also, through its unique redox potential, achieved dual excitation of oxygen molecules during photoinduced electron transfer, meaning that the system simultaneously generated singlet oxygen within 18 hours of light irradiation. 1 O2) and superoxide anion (O2•-).

[0089] Example 3

[0090] The temperature-responsive photocatalytic amidation reaction of the light-harvesting system includes the following steps:

[0091] Step 1: Using a pipette, sequentially transfer 100 μL of TPEG aqueous solution (5 mM), 100 μL of ESY DMSO solution (0.2 mM), 100 μL of NiR DMSO solution (0.2 mM), and 100 μL of Ce6 DMSO solution (0.2 mM) into a 20 mL round-bottom flask, then add deionized water to a total volume of 10 mL. After sonicating for 2 min to ensure uniform distribution of the components, add 1.0 mmol of potassium thioacetate and 0.5 mmol of p-anisidine sequentially to the system. React under UV irradiation at room temperature for 18 h to obtain the corresponding amide product, with a catalytic efficiency of up to 91%. 1 O2 is mainly used for the initial activation of the substrate, while O2•-, as a nucleophilic activator, synergistically lowers the transition state energy barrier of the amidation reaction, thereby achieving a yield of 91% under mild conditions.

[0092] Step 2: The prepared light-harvesting system (TPEG / ESY / NiR / Ce6) was subjected to photocatalytic reaction at different temperature conditions (25 ℃, 30 ℃, 40 ℃, 50 ℃, and 60 ℃) for 18 h. The products were detected and collected by high-performance liquid chromatography. Figure 11 As shown, the catalytic activity of the system gradually decreases with increasing reaction temperature, and the product yield shows a downward trend. This verifies the temperature control response performance of the system. This temperature control characteristic can not only be used for on / off control, but also serve as an environmental adaptive protection mechanism to prevent irreversible damage or side reactions caused by overheating in high-temperature environments.

[0093] Specific information on the amidation of anisidine under the above conditions is shown in Table 2 below.

[0094] Table 2. Specific information on the amidation of anisidine.

[0095]

[0096] Standard indicates the reaction conditions as follows: potassium thioacetate (0.2 mmol), p-methoxyaniline (0.1 mmol), TPEG / ESY / NiR / Ce6 aqueous solution (containing 0.5 mol% TPEG, 10 mL; 1000:40:40:40), LED lamp (365-375 nm), room temperature, air atmosphere, reaction for 18 h.

[0097] Step 3: The prepared light-harvesting system (TPEG / ESY / NiR / Ce6) is subjected to multiple heating / cooling cycles (5, 10, 15 and 20 times) between 25 °C and 60 °C before being used for photocatalytic amidation reaction. Figure 12It can be clearly observed that the yield remains basically unchanged after more than 20 heating / cooling cycles, and the system can still maintain stable temperature response behavior, which proves the good mechanical stability and catalytic durability of the system.

[0098] Example 4

[0099] The photocatalytic Schiff base (imine) synthesis reaction of the light-harvesting system includes the following steps:

[0100] Step 1: Using a pipette, sequentially transfer 100 μL of TPEG aqueous solution (5 mM), 100 μL of ESY DMSO solution (0.2 mM), 100 μL of NiR DMSO solution (0.2 mM), and 100 μL of Ce6 DMSO solution (0.2 mM) into a 20 mL round-bottom flask, then add deionized water to a total volume of 10 mL. After sonication for 2 min, add o-phenylenediamine (1.0 mmol) and benzaldehyde (0.5 mmol) sequentially to the system. React under UV irradiation at room temperature for 18 h to obtain the corresponding product, with a catalytic efficiency of up to 95%.

[0101] Step 2: The prepared light-harvesting system (TPEG / ESY / NiR / Ce6) was placed under different temperature conditions (25 ℃, 30 ℃, 40 ℃, 50 ℃ and 60 ℃) for photocatalytic reaction for 18 h. The products were detected and collected by high performance liquid chromatography.

[0102] Specific information regarding the Schiff base (imine) synthesis reaction under the above conditions is shown in Table 3 below.

[0103] Table 3. Specific information on the synthesis reaction of Schiff bases (imines)

[0104]

[0105] Standard indicates the reaction conditions as follows: o-phenylenediamine (0.1 mmol), benzaldehyde (0.1 mmol), TPEG / ESY / NiR / Ce6 aqueous solution (containing 0.5 mol% TPEG, 10 mL; 1000:40:40:40), LED lamp (365–375 nm), room temperature, air atmosphere, and reaction time of 18 h.

[0106] Comparative Example 1: Physical Mixed Control System

[0107] The purpose of this Comparative Example 1 is to compare the effects of confined assembly and simple mixing on energy efficiency.

[0108] Comparative Example 1 aims to verify the necessity of micro-nano confined assembly of TPEG nanoparticles in constructing a high-efficiency light-harvesting system. TPEG, ESY, NiR, and Ce6 were directly dispersed in deionized water at the same molar ratio as in step (3) of Example 1, without ultrasonic treatment. Performance was tested under the same illumination conditions. Experimental results showed that the fluorescence emission spectrum of this mixed system exhibited only weak background signals from each acceptor, no obvious cascade energy transfer (FRET) effect was observed, and the photocatalytic yield was less than 10%.

[0109] Comparative Example 1 demonstrates that the nanoparticles formed by ultrasonic triggering of TPEG are not simply dilution supports, but rather the core framework for constructing the FRET system. Only by precisely controlling the intermolecular distance between donor and acceptor molecules within the effective radius of FRET through confined assembly can a continuous energy transfer funnel be formed. Conventional physical mixing suffers significant energy loss due to its inability to overcome intermolecular distance limitations, confirming that confined assembly based on TPEG molecular design is the physical foundation for realizing cascade catalysis.

[0110] Comparative Example 2: Receptor Sequence Mismatch System

[0111] The purpose of this comparative example 2 is to compare the effects of energy level matching and disordered loads.

[0112] Comparative Example 2 aims to verify the technical necessity of ESY→NiR→Ce6 spectral energy level ladder matching in achieving efficient cascade transport. Two comparative schemes were designed: Scheme A, Ce6 was directly loaded into the TPEG / ESY system (spanning NiR); Scheme B, Ce6 was replaced with coumarin 6 (its absorption peak is about 450 nm, with very low overlap with the NiR emission peak at 620-650 nm), constructing a TPEG / ESY / NiR / Coumarin 6 system. Tests were conducted under the same conditions as in step (3) of Example 1. Experimental results showed that the fluorescence resonance energy transfer efficiency of both schemes dropped sharply, and the amidation reaction yield fell below 35%.

[0113] The above results demonstrate that the specific receptor sequence (ESY→NiR→Ce6) of this invention constructs an optimal energy transport path based on energy level matching. Deviating from this ordered energy level sequence leads to increased nonradiative transition losses in excited-state energy, thus confirming that the receptor combination and arrangement order of this invention are not randomly selected, but rather a key technology for achieving efficient cascaded energy enhancement.

[0114] Comparative Example 3

[0115] Under the same conditions as step (3) in Example 1, NiR was replaced with the hydrophilic dye Cy5-COOH to construct a four-component system of TPEG / ESY / Cy5-COOH / Ce6 (D / A1 / A2 / A3=1000:40:40:40). The absorption peak of Cy5-COOH was about 650 nm, which is close to the emission peak of NiR at about 636-638 nm.

[0116] Experimental results:

[0117] Although the emission spectra of Cy5-COOH and ESY show significant overlap, the FRET efficiency of this system is only 48.5% (compared to 60.6% for the three-step TPEG / ESY / NiR / Ce6 system); the catalytic amidation yield drops to 55%. Moreover, compared to the two-step TPEG / ESY / NiR system without Ce6 (yield 68%), the four-component system formed by replacing NiR with Cy5-COOH has an even lower yield (55%).

[0118] Although Cy5-COOH is spectrally similar to NiR, its higher hydrophilicity results in lower loading efficiency and spatial localization within the hydrophobic cavity of TPEG compared to NiR, leading to a significant decrease in actual effective FRET efficiency and catalytic amidation yield. This indicates that similar spectral characteristics alone are insufficient to achieve efficient energy transfer in this system; the compatibility of NiR's hydrophobic properties with the hydrophobic cavity of TPEG is equally crucial.

[0119] This further confirms that the success of NiR in this application lies not only in its optical properties, but also in its special affinity for the hydrophobic cavity of TPEG.

[0120] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A thermally sensitive three-step cascaded light-trapping system, characterized in that, The system consists of nanoparticles formed by ultrasonic self-assembly of the amphiphilic molecule TPEG with low critical solution temperature characteristics, the first energy acceptor YESY, the second energy acceptor NiR, and the third energy acceptor chlorophyll e6 Ce6. The molar ratio of TPEG, ESY, NiR and Ce6 in the nanoparticles is 1000 : 10~40 : 10~40 : 10~40; The system forms uniform nanoparticles through ultrasonic treatment, driven by hydrophobic interaction, so that the average center-to-center distance of each molecule is controlled within 10 nm. Under ultraviolet light excitation, the system forms a three-step continuous fluorescence resonance energy transfer cascade path, namely TPEG→ESY→NiR→Ce6, through the FRET effect.

2. The system according to claim 1, characterized in that, The amphiphilic molecule TPEG contains a hydrophobic fluorescent group tetraphenylethylene as the parent core and a temperature-responsive methoxy-terminated oligoethylene glycol linked by a phenoxy group as the hydrophilic chain. The structural formula of the TPEG is: 。 3. The system according to claim 2, characterized in that, The critical aggregation concentration of the amphiphilic molecule TPEG is 38 μM, and the TPEG forms nanoparticles through self-assembly in the aqueous phase; the cloud point temperature of the TPEG at concentrations of 38 μM to 200 μM is 32 to 37 °C.

4. The system according to claim 1, characterized in that, When the molar ratio of TPEG, ESY, NiR and Ce6 in the nanoparticles is 1000:40:40:40, the system achieves the optimal three-step cascaded fluorescence resonance energy transfer efficiency.

5. The system according to claim 1, characterized in that, The system exhibits thermal reversibility, maintaining a stable nanoparticle assembly structure after at least 20 heating / cooling cycles between 25 °C and 60 °C, and is able to recover to its initial temperature response behavior.

6. The system according to claim 1, characterized in that, When the temperature rises, the oligoethylene glycol segments in the TPEG break through the hydrogen bonds between OEG and water molecules, causing the molecular chains to dehydrate and collapse, resulting in the disaggregation of nanoparticles and temporarily interrupting the FRET cascade energy transfer path. When the temperature drops, OEG and water molecules reassociate, the nanoparticles reassemble, and the FRET cascade path is restored.

7. The system according to claim 1, characterized in that, When the third-level energy acceptor Ce6 receives excited-state energy from the second-level energy acceptor NiR, it can promote the generation of two reactive oxygen species, singlet oxygen and superoxide anion, through a photoinduction process.

8. The method for preparing the system according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Dissolve the amphiphilic molecule TPEG in deionized water to prepare a concentration of 3.8 × 10⁻⁶. -5 M~1×10 -3 The solution of M was subjected to ultrasonic treatment at 40 kHz for 2-3 min to induce TPEG self-assembly into nanoparticles. S2: Add the first-level energy acceptor ESY to the TPEG nanoparticle solution, and sonicate again at 40 kHz for 2-3 min to form a TPEG-ESY complex. S3: Add the secondary energy acceptor NiR to the TPEG-ESY complex, and sonicate again at 40 kHz for 2-3 min to form the TPEG-ESY-NiR complex; S4: Add Ce6, the third-level energy acceptor, to the TPEG-ESY-NiR complex, and sonicate again at 40 kHz for 2-3 min to finally form the TPEG-ESY-NiR-Ce6 system.

9. The application of the thermosensitive three-step cascaded light-harvesting system according to any one of claims 1-7 in photocatalytic organic reactions, characterized in that: The system is used to catalyze amidation reactions, Schiff base synthesis reactions, or other similar photocatalytic organic synthesis reactions involving reactive oxygen species.

10. The application according to claim 9, characterized in that, The photocatalytic method includes the following steps: Step 1: Prepare the light-harvesting system, wherein the light-harvesting system contains an aqueous solution of TPEG with a concentration of 0.5 mM; add the organic substrate to be catalyzed to the light-harvesting system and mix thoroughly; Step 2: Under irradiation with a 365-375 nm ultraviolet lamp, react at room temperature for 18 h; Step 3: Detect and collect the product by chromatography.

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