Preparation method and application of dual fluorescence resonance energy transfer light-trapping nanofibers

Abstract

This invention discloses a method for preparing dual fluorescence resonance energy transfer (FRET) light-trapping nanofibers and their application in photocatalytic reactions. The preparation method involves: adding deionized water to polyvinyl alcohol and a cationic polymer and stirring to allow for complete swelling; then sealing the resulting mixture and heating and stirring it in a water bath to obtain a cationic polyvinyl alcohol electrospinning solution; adding tetrasulfonated tetraphenylethylene, Acid Yellow 184, and Fluorescent Pink B to the cationic polyvinyl alcohol electrospinning solution to obtain a fluorescent polyvinyl alcohol spinning solution; and spinning the fluorescent polyvinyl alcohol spinning solution. The photocatalytic fibers of this invention utilize dual FRET effects and donor aggregation luminescence to significantly improve photocatalytic performance. The photocatalyst of this invention exhibits high photocatalytic activity, good substrate universality, and excellent cycling stability, providing an efficient and sustainable solution for photocatalytic reactions.

Description

Technical Field

[0001] This invention relates to a method for preparing double fluorescence resonance energy transfer (FRET) light-harvesting nanofibers and their application in photocatalytic reactions, belonging to the field of nanomaterials technology. Background Technology

[0002] In the fields of chemical synthesis and materials science, photocatalysts have attracted much attention due to their potential applications in environmental remediation, energy conversion, and organic synthesis. These catalysts induce chemical reactions by absorbing light energy to excite electrons, thereby achieving substrate transformation. However, traditional photocatalysts suffer from several limitations, including low light-harvesting efficiency, insufficient photocatalytic activity, limited spectral response range, and poor stability and recyclability. These limitations affect the practical application efficiency and economic viability of photocatalysts.

[0003] To overcome these challenges, researchers have explored fluorescence resonance energy transfer (FRET) technology to improve the light-harvesting efficiency and activity of photocatalysts. FRET is a non-radioactive energy transfer process that enables efficient energy transfer between donor and acceptor fluorescent molecules. However, conventional FRET and single FRET systems typically involve a single energy transfer step, which can lead to low energy transfer efficiency, especially when the distance between the donor and acceptor is large. Furthermore, these systems can usually only effectively utilize light energy within a specific wavelength range, limiting their application under broad-spectrum light sources. Additionally, due to the poor photostability and reproducibility of fluorophores, these systems are prone to photobleaching under prolonged illumination, affecting catalytic efficiency and reusability. Moreover, the small extinction cross-section of organic fluorophores necessitates higher light power to drive the reaction. Summary of the Invention

[0004] The technical problem to be solved by this invention is that traditional photocatalysts have limitations in terms of light capture efficiency, photocatalytic activity, spectral response range, stability, and recyclability.

[0005] To address the above problems, this invention provides a method for preparing dual fluorescence resonance energy transfer light-trapping nanofibers, comprising the following steps:

[0006] Step 1): Add deionized water to polyvinyl alcohol (PVA) and cationic polymer and stir to allow it to swell fully; then seal the resulting mixture and place it in a water bath for heating and stirring until the polyvinyl alcohol is fully dissolved to obtain a transparent and uniform polyvinyl alcohol aqueous solution. After cooling, the cationic polyvinyl alcohol electrospinning solution is obtained.

[0007] Step 2): Add tetrasulfonated tetraphenylethylene (TPE4S), acid yellow 184 (AY184), and fluorescent pink B (PhB) to the cationic polyvinyl alcohol electrospinning solution to obtain a fluorescent polyvinyl alcohol spinning solution.

[0008] Step 3): Transfer the fluorescent polyvinyl alcohol spinning solution into a syringe, spin the nanofibers using a uniaxial electrospinning device, collect the nanofibers using a roller covered with silicone paper, and dry the obtained nanofibers in a forced-air drying oven.

[0009] Preferably, in step 1), the degree of polymerization of polyvinyl alcohol is 1750 and the degree of alcoholysis is 88%; the cationic polymer is at least one of polydimethylammonium chloride (PDADMAC) and polyethyleneimine.

[0010] More preferably, the molecular weight of the polydiene dimethyl ammonium chloride is 5,000-200,000; and the polyethyleneimine is hyperbranched polyethyleneimine or linear polyethyleneimine with a molecular weight of 300-2,000.

[0011] Preferably, in step 1), the ratio of polyvinyl alcohol, cationic polymer, and deionized water is 5-10g: 0-1g: 90-95mL.

[0012] Preferably, in step 1), the temperature of the water bath is 80-100℃, and the heating and stirring time is 5 hours.

[0013] Preferably, in step 2), the amount of each of the three fluorophores is 2.4 × 10⁻⁶ based on the weight of polyvinyl alcohol. -4 -2.4×10 -5 mol / g.

[0014] Preferably, in step 2), the spinning process parameters are: voltage 12kV, receiving distance 15cm, flow rate 0.4mL / h, roller speed 300rpm; drying temperature 50℃, time 12h.

[0015] This invention also provides the application of the dual fluorescence resonance energy transfer light-trapping nanofibers prepared by the above preparation method as photocatalysts in photocatalytic reactions.

[0016] Preferably, the photocatalytic reaction is a cross-coupling dehydrogenation (CDC) reaction between an N-phenyl-tetrahydroisoquinoline derivative and dimethyl phosphite, nitromethane, or acetone.

[0017] Preferably, the dual fluorescence resonance energy transfer light-harvesting nanofibers are used for multiple photocatalytic reactions after being washed with a solvent.

[0018] The principle of this invention is as follows:

[0019] (1) Continuous Two-Step FRET System: This invention significantly improves energy transfer efficiency by constructing a continuous two-step FRET system. Highly efficient energy transfer is achieved by introducing two energy donors (TPE4S and AY184) and one acceptor (PhB) into the nanofibers.

[0020] (2) High specific surface area and porosity carrier: Nanofiber membranes prepared by electrospinning technology have high specific surface area and porosity, providing abundant sites for photocatalytic reactions and improving the reaction rate.

[0021] (3) Enhanced photostability and repeatability: By fixing the fluorophore onto the cationized PVA fiber, the photobleaching of the fluorophore is reduced, and the photostability and reusability are improved.

[0022] (4) Broad spectrum response: By designing a FRET system with a broad spectrum response, the present invention can effectively utilize a broad spectrum light source and improve photocatalytic efficiency.

[0023] Through the above innovative approach, this invention not only solves the problems existing in ordinary FRET and single FRET systems, but also provides a highly efficient, stable and reusable photocatalyst suitable for a variety of photocatalytic reactions.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The photocatalytic fiber of the present invention utilizes the dual FRET effect and the aggregation luminescence effect of the donor to significantly improve the photocatalytic performance, and is particularly suitable for the cross-coupling dehydrogenation (CDC) reaction between N-phenyl-tetrahydroisoquinoline derivatives and phosphites.

[0026] (2) The photocatalyst of the present invention has high photocatalytic activity, good substrate universality and excellent cycle stability, providing an efficient and sustainable solution for photocatalytic reactions. Detailed Implementation

[0027] To make the present invention more apparent and understandable, preferred embodiments are described in detail below.

[0028] This invention provides a method for preparing double fluorescence resonance energy transfer (FRET) light-harvesting nanofibers, comprising the following steps:

[0029] a. Preparation of raw materials and reagents: Tetrasulfonated tetraphenylethylene (TPE4S); Acid Yellow 184 (AY184); Fluorescent Pink B (PhB); Polyvinyl alcohol (PVA, molecular weight 75,000); Polydiallyl dimethyl ammonium chloride (PDADMAC, molecular weight 100,000-200,000); Silver trifluoroacetate; Polyvinylpyrrolidone (PVP); Ethylene glycol (EG); Other conventional chemical reagents.

[0030] b. Preparation of electrospun nanofibers: 10g PVA and different contents of PDADMAC were added to 90mL of deionized water, stirred for 30 minutes to allow it to swell fully, and heated in an 80℃ water bath for 5 hours to obtain a transparent and uniform PVA aqueous solution.

[0031] c. Preparation of light-harvesting nanofibers: Three fluorophores, TPE4S, AY184, and PhB, were added to the PVA electrospinning solution. The solution was magnetically stirred at room temperature for 3 hours, then transferred to a syringe. Electrospinning was performed using a uniaxial electrospinning apparatus at a voltage of 12 kV, a working distance of 15 cm, and a flow rate of 0.4 mL / h. The nanofibers were collected using a roller covered with silicone paper. The obtained nanofibers were dried in a 50°C forced-air drying oven for 12 hours, sealed, and stored in a dark place for later use.

[0032] d. Application of photocatalytic CDC reaction: The reactants N-phenyl-tetrahydroisoquinoline or its derivatives (0.1 mmol) and phosphite (0.2 mL) were dissolved in 10 mL of ethanol and placed in a 20 mL quartz tube. The prepared light-harvesting nanofiber membrane was cut into 1 cm × 1 cm squares and immersed in the above reaction solution. The reaction was carried out under simultaneous irradiation with a 1 W white LED and a 365 nm ultraviolet LED for 4 hours. Samples were taken every 0.5 hours, and the conversion rate of N-aryl-tetrahydroisoquinoline at different time points was monitored by HPLC.

[0033] The TPE4S-AY184-PhB / Ag / PDADMAC / PVA nanofibers prepared by the above steps exhibited excellent photocatalytic performance in the CDC reaction, with high conversion rate and good cycling stability.

[0034] Example 1: The effect of PDADMAC / PVA composite nanofibers with different cationization levels on fluorophore immobilization

[0035] The cationization level of the composite nanofiber membrane was controlled by changing the mass fraction of PDADMAC relative to PVA. First, five groups of PDADMAC / PVA aqueous solutions with different PDADMAC contents were prepared, where the mass fraction of PVA was 10%, and the mass fractions of PDADMAC relative to PVA were 0%, 3%, 5%, 7%, and 10%. These mixed aqueous solutions were used as spinning solutions for electrospinning, and the resulting nanofibers were subjected to zeta potential testing. The test results are shown in Table 1.

[0036] Table 1

[0037] PDADMAC relative to PVA quality score (%) Zeta potential (mV) 0 -1.86 3 2.45 5 5.12 7 8.84 10 12.65

[0038] Take 10g of PDADMAC / PVA aqueous solution with PDADMAC content of 0%, 5%, and 10% respectively, and add 2.4×10 to each group. -4 Nanofiber membranes containing mol of three fluorophores—TPE4S, AY184, and PhB—were prepared by spinning. The adsorption and fixation rates of the composite fiber membranes for these three fluorophores were then determined by desorption experiments. The desorption experiment involved weighing 0.25 g of the fiber membrane and placing it in 100 mL of ethanol for five 6-hour desorption cycles. The final adsorption and fixation rate was determined by measuring the final absorbance. The results are shown in Table 2.

[0039] Table 2

[0040]

[0041]

[0042] Example 2: Optimization of the ratio of the three fluorophores when the main catalyst PhB exhibits the best fluorescence effect

[0043] A spinning solution with a PDADMAC relative content of 10% was selected. First, the optimal ratio of energy transfer between TPE4S and AY184 in the first step was determined. Then, based on this, different contents of PhB were added to determine the ratio of the three fluorophores when the fluorescence effect (which can be considered as the catalytic effect) of the main catalyst PhB was optimal.

[0044] The dosage of the first donor, TPE4S, was 2.4 × 10⁻⁶. -4 Five different molar ratios of one-step FRET light-collecting nanofibers were prepared by electrospinning with different amounts of the second donor AY184 added to polyvinyl alcohol (mol / g). The optimal ratio of the two donors in the first step of FRET was determined by comparing the fluorescence emission peak of AY184. The obtained data are shown in Table 3.

[0045] Table 3

[0046]

[0047] In the first step of FRET, the optimal molar ratio of TPE4S to AY184 for FRET is 10:1. Based on this ratio, different amounts of the main catalyst and the acceptor fluorophore PhB are added to determine the optimal dosage of each dye. That is, the optimal dosage of TPE4S is 2.4 × 10⁻⁶. -4 2.4 × 10 mol / g polyvinyl alcohol, the dosage of AY184 is 2.4 × 10 -5 mol / g polyvinyl alcohol. The optimal amount of PhB was determined for the second step FRET by comparing the fluorescence emission peak levels. The results are shown in Table 4.

[0048] Table 4

[0049]

[0050]

[0051] As shown in Table 4, the optimal molar ratio among the three fluorophores is 10:1:1.

[0052] Example 4: Universality of light-harvesting nanofibers for substrates in photocatalytic CDC reactions

[0053] Photocatalysts were prepared by electrospinning to obtain nanofibers with the optimal ratio of three fluorophores. Their versatility in catalyzing the CDC reaction of N-phenyl-tetrahydroisoquinoline derivatives with dimethyl phosphite or diethyl phosphite was investigated. Reaction conditions: N-phenyl-tetrahydroisoquinoline (0.1 mmol), dimethyl phosphite or diethyl phosphite (0.2 mL), 50 mg of photo-collecting nanofiber membrane (PhB, 1.2 mol%), 10 mL of ethanol, temperature 35 °C, time 4 h, irradiation with 1 W white light + UV LED. The obtained data are shown in Table 5.

[0054] Table 5

[0055] N-phenyl-tetrahydroisoquinoline derivatives Phosphite Substrate conversion rate (%) N-p-methylphenyl-tetrahydroisoquinoline dimethyl phosphite 93.8 N-p-methoxyphenyl-tetrahydroisoquinoline dimethyl phosphite 91.6 N-p-chlorophenyltetrahydroisoquinoline dimethyl phosphite 96.6 N-p-Trifluoromethoxyphenyl-tetrahydroisoquinoline dimethyl phosphite 93.7 N-p-methylphenyl-tetrahydroisoquinoline diethyl phosphite 90.2 N-p-methoxyphenyl-tetrahydroisoquinoline diethyl phosphite 87.1 N-p-chlorophenyltetrahydroisoquinoline diethyl phosphite 93.8 N-p-Trifluoromethoxyphenyl-tetrahydroisoquinoline diethyl phosphite 89.8

[0056] Example 5: Cyclic stability of light-harvesting nanofibers in photocatalytic CDC reaction

[0057] Photo-trapping nanofibers with the optimal ratio of three fluorophores were prepared by electrospinning. Using the CDC reaction between N-phenyl-tetrahydroisoquinoline and dimethyl phosphite as a model, the cycling stability of the described photo-trapping nanofibers in the photocatalytic CDC reaction was investigated. Reaction conditions: N-phenyl-tetrahydroisoquinoline (0.1 mmol), dimethyl phosphite or diethyl phosphite (0.2 mL), 50 mg of photo-trapping nanofiber membrane (PhB, 1.2 mol%), 10 mL of ethanol, temperature 35 °C, time 4 h, irradiation with 1 W white light + UV LED. The obtained data are shown in Table 6.

[0058] Table 6

[0059] Loop count Substrate conversion rate (%) 1 99.6 2 97.1 3 94.4 4 93.8 5 93.3

Claims

1. The application of a dual fluorescence resonance energy transfer light-trapping nanofiber as a photocatalyst in photocatalytic reactions, characterized in that, The photocatalytic reaction is a cross-coupling dehydrogenation reaction between N-phenyl-tetrahydroisoquinoline derivatives and dimethyl phosphite, nitromethane, or acetone; The preparation method of the dual fluorescence resonance energy transfer light-harvesting nanofibers includes the following steps: Step 1): Add deionized water to polyvinyl alcohol and cationic polymer and stir to allow it to swell fully; then seal the resulting mixture and heat and stir it in a water bath until the polyvinyl alcohol is fully dissolved to obtain a transparent and uniform polyvinyl alcohol aqueous solution. After cooling, the cationic polyvinyl alcohol electrospinning solution is obtained. Step 2): Add tetrasulfonated tetraphenylethylene, Acid Yellow 184 and Fluorescent Pink B to the cationic polyvinyl alcohol electrospinning solution to obtain a fluorescent polyvinyl alcohol spinning solution. Step 3): Transfer the fluorescent polyvinyl alcohol spinning solution into a syringe, spin the nanofibers using a uniaxial electrospinning device, collect the nanofibers using a roller covered with silicone paper, and dry the obtained nanofibers in a forced-air drying oven.

2. The application as described in claim 1, characterized in that, In step 1), the degree of polymerization of polyvinyl alcohol is 1750 and the degree of alcoholysis is 88%; the cationic polymer is at least one of polydimethylammonium chloride and polyethyleneimine.

3. The application as described in claim 2, characterized in that, The molecular weight of the polydiene dimethyl ammonium chloride is 5,000-200,000; the polyethyleneimine is hyperbranched polyethyleneimine or linear polyethyleneimine with a molecular weight of 300-2,000.

4. The application as described in claim 1, characterized in that, In step 1), the ratio of polyvinyl alcohol, cationic polymer, and deionized water is 5-10g: 0-1g: 90-95mL.

5. The application as described in claim 1, characterized in that, In step 1), the water bath temperature is 80-100℃, and the heating and stirring time is 5 hours.

6. The application as described in claim 1, characterized in that, In step 2), the amount of each of the three fluorophores used is 2.4 × 10⁻⁶ based on the weight of polyvinyl alcohol. -4 -2.4×10 -5 mol / g.

7. The application as described in claim 1, characterized in that, In step 2), the spinning process parameters are: voltage 12kV, receiving distance 15cm, flow rate 0.4mL / h, roller speed 300rpm; drying temperature 50℃, time 12h.

8. The application as described in claim 1, characterized in that, The dual fluorescence resonance energy transfer light-harvesting nanofibers, after being washed with solvent, are used for multiple photocatalytic reactions.

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