A nanoscale chiral nanoscroll array continuous film, a preparation method thereof and application thereof in polarization-sensitive photocatalysis

Abstract

A nano-scale chiral Swiss roll array continuous film, a preparation method and application thereof in polarization-sensitive photocatalysis belong to the technical field of photocatalytic materials.The method disclosed by the application relates to colloidal interface self-assembly, mask etching and glancing angle deposition, and the preparation process has the characteristics of low cost, high throughput and large area.The size of the Swiss roll metamaterial is reduced to the nano scale through colloidal etching technology, and strong chiral optical response in the visible light region is realized.When the chirality of the Swiss roll array matches the polarization direction of the circularly polarized light, the photocatalytic reaction rate is significantly improved, and the selective control of the photocatalytic reaction is realized.In addition, the nano-scale chiral Swiss roll array continuous film can be recycled only by simple and low-cost treatment, which provides a sustainable and flexible tool for chiral photocatalysis, realizes the selective control of the photocatalytic reaction, and has important significance in actual photocatalytic applications.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a nanoscale chiral Swiss roll array continuous film, its preparation method, and its application in polarization-sensitive photocatalysis. Background Technology

[0002] Chirality is a geometric property that prevents an object from being superimposed on its mirror image. It is ubiquitous in nature and plays a crucial role in chemistry, biology, physics, and medicine. [1] Chiral metamaterials hold significant importance in various fields, including chemistry, biomedicine, and chiral sensing. Among these metamaterials, Swiss roll structures have attracted considerable attention over the past few decades due to their ideal chirality. [2] Advances in nanofabrication technology have facilitated the development of Swiss roll metamaterials. However, transitioning Swiss roll metamaterials to the optical frequency range requires reducing them to the nanoscale, which remains a challenge.

[0003] Manipulating chirality at the nanoscale has attracted widespread attention from scientists. Circularly polarized light (CPL) is an ideal source of chirality. [3] Due to its near-perfect enantiomeric purity, high practicality, and flexible spectral tunability, it has been used in the synthesis of chiral materials. [4-7] However, it is rarely applied to the selective control of plasma photocatalysis. Currently, the generation of asymmetric hot electrons in photochemical reactions has been confirmed through theoretical simulations, but experimental verification is scarce. In the few works available, Govorov et al. reported a polarization-sensitive photocatalytic reaction using a hybrid structure of Au and TiO2 nanoparticles encapsulating SiO2. [8] The matching of the chirality of the catalyst with the polarization direction of circularly polarized light is a decisive factor in the catalytic rate. Kuang et al. reported polarization-dependent photocatalysis based on chiral gold-silver dimer nanostructures. [9] However, these works are all based on chiral nanoparticles dispersed in solution, which have poor integration and are complex and time-consuming to recycle and reuse.

[0004] [1]Valev VK; Baumberg JJ; Sibilia C., Adv.Mater., 2013, 25(18), 2517-2534.

[0005] [2]Pendry JB,Science,306(2004),1353-1355.

[0006] [3]Li J.;Wang M.;Wu Z,Nano Lett.,2021,21(2),973-979.

[0007] [4] Besteiro LV; Movsesyan A., Nano Lett., 21(24),10315-10324.

[0008] [5]Yeom J.; Yeom B.; Chan H.,Nat.Mater.,2015,14(1),66-72.

[0009] [6] Saito K.; Tatsuma T., Nano Lett., 2018, 18(5), 3209-3212.

[0010] [7] Morisawa.K.; Ishida T.; Tatsuma T., ACS Nano, 2020, 14(3), 3603-3609.

[0011] [8] Negrin-Montecelo Y.; Movsesyan A.; Gao J., J. Am. Chem. Soc., 2022, 144(4), 1663-1671.

[0012] [9]Hao C.;Xu L.;Ma W.,Adv.Funct.Mater.,2015,25(36),5816-5822. Summary of the Invention

[0013] The purpose of this invention is to provide a nanoscale chiral Swiss roll array continuous film, its preparation method, and its application in polarization-sensitive photocatalysis.

[0014] The method described in this invention involves colloidal interface self-assembly, mask etching, and grazing angle deposition. The fabrication process is characterized by low cost, high throughput, and large area. The nanoscale chiral Swiss roll array continuous film prepared by this invention reduces the size of the Swiss roll metamaterial to the nanoscale using colloidal etching technology, achieving a strong chiral optical response in the visible light region. The nanoscale chiral Swiss roll array continuous film exhibits polarization-dependent photocatalytic activity; that is, when the chirality of the Swiss roll array matches the polarization direction of circularly polarized light, the photocatalytic reaction rate is significantly improved, achieving selective control of the photocatalytic reaction. Furthermore, the nanoscale chiral Swiss roll array continuous film can be recycled with simple and low-cost processing, providing a sustainable and flexible tool for chiral photocatalysis. In summary, the nanoscale chiral Swiss roll array continuous film exhibits a strong chiral response in the visible light region, can be used for polarization-dependent photocatalysis, and achieves selective control of photocatalytic reactions, which has significant implications for practical photocatalytic applications.

[0015] The present invention discloses a nanoscale chiral Swiss roll array continuous film, its preparation method, and its application in polarization-sensitive photocatalysis. The steps are as follows:

[0016] 1) On the hydrophilically treated substrate, spin-coat a layer of photoresist at a speed of 2000-5000 rpm, cure at 80-120℃ for 1-2 hours, and cool to room temperature to obtain a photoresist film with a thickness of 0.4-2 μm on the substrate.

[0017] 2) A hydrophobic polystyrene microsphere mixture of deionized water and ethanol is slowly added dropwise to a pre-prepared deionized water surface to obtain a polystyrene microsphere monolayer on the gas-liquid surface; then an anionic surfactant (sulfonate or sulfonate salt, etc.) is added dropwise to obtain a hexagonal close-packed polystyrene microsphere monolayer; this hexagonal close-packed polystyrene microsphere monolayer is transferred to the photoresist film prepared in step 1) and allowed to dry naturally;

[0018] 3) Place the sample prepared in step 2) in a plasma etching machine. During the etching process, the diameter of the polystyrene microspheres gradually decreases, and the photoresist film at the bottom is etched into a frustum array. Stop etching before the microspheres completely disappear.

[0019] 4) Place the sample prepared in step 3) in a vacuum coating chamber and thermally evaporate and deposit gold film 1 at a certain incident angle. Then, deposit silver film 1 on the opposite side of gold film 1. Gold film 1 and silver film 1 form the first layer structure of the Swiss roll. Then, rotate the substrate counterclockwise or clockwise by 90° and thermally evaporate and deposit gold film 2 at the same incident angle. Then, deposit silver film 2 on the opposite side of gold film 2. Gold film 2 and silver film 2 form the second layer structure of the Swiss roll. Finally, deposit gold film 3 on the opposite side of gold film 1 so that the gold film forms a continuous Swiss roll. The angle between the substrate normal direction and the deposition direction, i.e., the incident angle, is 10° to 60°. The deposition thickness of gold film 1, gold film 2, gold film 3, silver film 1, and silver film 2 is 10 to 70 nm.

[0020] 5) Immerse the sample prepared in step 4) in 3-25 mL of toluene and sonicate it at 40% power (40W) for 20-60 s to remove the residual polystyrene microspheres that have not been etched away.

[0021] 6) The sample prepared in step 5) is transferred to anhydrous ethanol and soaked for 1-3 hours to remove the photoresist film. It is then rinsed with deionized water and dried naturally to obtain a hollow chiral Swiss roll nanoarray continuous film.

[0022] 7) The sample prepared in step 6) was immersed in a Rhodamine B aqueous solution with a concentration of 2-10 ppm and irradiated with left-handed and right-handed circularly polarized light generated by a 532 nm laser for 0-12 hours respectively. After the light irradiation started, the sample was taken out of the solution periodically and analyzed with a UV-Vis spectrophotometer to test the polarization-sensitive photocatalytic performance of the nanoscale Swiss roll nanoarray film.

[0023] Furthermore,

[0024] The substrate in step 1) is a glass plate or a quartz plate.

[0025] In step 2), the diameter of the polystyrene microspheres is 0.3–3 μm.

[0026] The hydrophobic polystyrene microspheres in step 2) were obtained by the method described in the following steps:

[0027] (1) Add 4-8 mL of deionized water to a 1-5 mL deionized water dispersion of polystyrene microspheres with a concentration of 1-15 wt% and a diameter of 0.3-3 μm, sonicate at 100% power (100W) for 20-30 min, and then centrifuge at 4000-8900 rpm for 20-30 min to remove the supernatant.

[0028] (2) Add 4-8 mL of deionized water to the precipitate of lower polystyrene microspheres, sonicate at 100% power (100W) for 20-30 min, and then centrifuge at 4000-8900 rpm for 20-30 min to remove the supernatant.

[0029] (3) Repeat step (2) 6 to 10 times;

[0030] (4) Add 4-8 mL of a 1:1 mixture of ethanol and deionized water to the precipitate of the lower polystyrene microspheres, sonicate at 100% power (100W) for 20-30 min, and then centrifuge at 4000-8900 rpm for 20-30 min to remove the supernatant.

[0031] (5) Repeat step (4) 10 to 15 times;

[0032] (6) Add 1-2 mL of a 1:1 mixture of ethanol and deionized water to the precipitate of the lower layer of polystyrene microspheres, and sonicate at 100% power (100W) for 60-120 min to obtain a hydrophobic polystyrene microsphere mixture of deionized water and ethanol.

[0033] Step 3) The etching atmosphere for plasma etching is oxygen, the gas flow rate is 10-60 sccm, the etching pressure is 5-10 mTorr, the etching temperature is 5-25℃, the etching power is 100-500W, and the etching time is 60-300s.

[0034] In step 4), the vacuum degree for thermal evaporation deposition is 2 × 10⁻⁶. -4 ~5×10 -4 Pa, deposition rate is

[0035] The present invention features simple operational steps, reducing the size of the Swiss roll metamaterial to the nanoscale through colloidal etching, thereby achieving a strong chiral optical response in the visible light region. The nanoscale chiral array film exhibits polarization-dependent photocatalytic activity, enabling selective control of the photocatalytic reaction. Furthermore, this array film can be recycled with only simple and low-cost processing, providing a sustainable and flexible tool for chiral photocatalysis. Attached Figure Description

[0036] Figure 1 A schematic diagram of the process for fabricating a chiral Swiss roll nanoarray continuous film; wherein, substrate 1, photoresist 2, polystyrene microspheres 3, and metal film 4; step A: anisotropic plasma etching; step B: tilted deposition of gold film 1 (θ=30°, Step C: Deposit silver film 1 on the opposite side of gold film 1 (θ = -30°). Step D1: Deposit gold film 2 at an angle (θ = 30°); Rotate clockwise 90°); Step E1: Deposit silver film 2 on the opposite side of gold film 2 (θ = -30°, Rotate clockwise 90°); Step F1: Deposit gold film 3 on the opposite side of gold film 1 (θ = -30°, Step G1: Remove residual polystyrene microspheres and photoresist; Step D2: Deposit gold film 2 at an angle (θ = 30°). (Rotate counterclockwise 90°); Step E2: Deposit silver film 2 on the opposite side of gold film 2 (θ=-30°, Rotate counterclockwise 90°); Step F2: Deposit gold film 3 on the opposite side of gold film 1 (θ=-30°, Step G2: Remove residual polystyrene microspheres and photoresist.

[0037] Figure 2 This is a scanning electron microscope (SEM) image of a right-handed Swiss roll nanoarray. The SEM image shows that the pore diameter gradually decreases in the upper part of the Swiss roll structure due to tilted deposition.

[0038] Figure 3 The circular dichroism (CD) spectrum of the chiral Swiss roll nanoarray, as measured experimentally, exhibits a clear chiral signal in the visible light region of 300–800 nm.

[0039] Figure 4 The image shows the photocatalytic performance of a chiral Swiss roll array film under circularly polarized light irradiation.

[0040] (A) shows the spectrum of the maximum absorption peak of Rhodamine B at 554 nm over time under irradiation with left-handed Swiss roll light at 532 nm using both left-handed polarized (LCP) and right-handed polarized (RCP) light. The maximum absorption peak at 554 nm decreases with increasing time, indicating a decrease in the concentration of Rhodamine B in the solution.

[0041] (B) shows the normalized degradation rate graphs of the left-handed Swiss roll under different polarized light irradiation (assuming a linear relationship between degradation rate and reaction time: normalized degradation rate = absorbance of Rhodamine B at 554 nm / reaction time). The degradation rate of Rhodamine B by the left-handed Swiss roll under left-handed polarized light irradiation is higher than that under right-handed polarized light irradiation. Therefore, graphs (A) and (B) demonstrate that the degradation performance of the left-handed Swiss roll is stronger under left-handed polarized light irradiation than under right-handed polarized light irradiation.

[0042] (C) shows the spectrum of the maximum absorption peak of Rhodamine B at 554 nm over time under left-handed and right-handed polarized light irradiation at 532 nm. The maximum absorption peak of Rhodamine B at 554 nm decreases with increasing time, indicating a decrease in the concentration of Rhodamine B in the solution.

[0043] (D) shows the normalized degradation rate graphs of the right-handed Swiss roll under different polarized light irradiation. The degradation rate of Rhodamine B by the right-handed Swiss roll under right-handed polarized light irradiation is higher than that under left-handed polarized light irradiation. Therefore, graphs (C) and (D) demonstrate that the degradation performance of the right-handed Swiss roll is stronger under right-handed polarized light irradiation than under left-handed polarized light irradiation. These four graphs demonstrate that the enantiomers of the chiral Swiss roll nanoarray film exhibit polarization-sensitive photocatalytic activity. Detailed Implementation

[0044] Example 1: Preparation of hydrophilic glass slides

[0045] Cut the glass slide into pieces 2cm wide and 2.5cm long using a glass cutter. Place the pieces in a mixed solution of 98% concentrated sulfuric acid and 30% hydrogen peroxide (volume ratio of concentrated sulfuric acid to hydrogen peroxide is 7:3). Heat the solution in a water bath at 80°C for 3 hours. Then wash the glass slides 6 times with deionized water and dry them with nitrogen gas.

[0046] Example 2: Preparation of photoresist thin film

[0047] The photoresist stock solution (BP212-37, positive photoresist, purchased from Beijing Kehua Microelectronics Materials Co., Ltd.) was spin-coated onto a hydrophilic glass substrate using a desktop spin coater at a speed of 3000 rpm (spray coating time of 30 s). The substrate was then cured in an oven at 88°C for 2 hours and cooled to room temperature, thus obtaining a photoresist film with a thickness of 2 μm on the glass substrate.

[0048] Example 3: Preparation of a mixed solution of hydrophobic polystyrene microspheres in deionized water and ethanol

[0049] (1) Add 8 mL of deionized water to a 2 mL deionized water dispersion of polystyrene microspheres with a concentration of 5 wt% and a diameter of 700 nm, sonicate at 100% power (100 W) for 20 min, and then centrifuge at 8000 rpm for 25 min to remove the supernatant.

[0050] (2) Add 8 mL of deionized water to the precipitate of lower polystyrene microspheres, sonicate at 100% power (100W) for 20 min, and then centrifuge at 8000 rpm for 25 min to remove the supernatant.

[0051] (3) Repeat step (2) 6 times;

[0052] (4) Add 8 mL of a 1:1 mixture of ethanol and deionized water to the precipitate of the lower polystyrene microspheres, sonicate at 100% power (100W) for 20 min, and then centrifuge at 8000 rpm for 25 min to remove the supernatant.

[0053] (5) Repeat step (4) 15 times;

[0054] (6) Add 1 mL of a 1:1 mixture of ethanol and deionized water to the precipitate of the lower layer of polystyrene microspheres, and sonicate at 100% power (100W) for 60 min to obtain a hydrophobic polystyrene microsphere mixture of deionized water and ethanol.

[0055] Example 4: Preparation of hexagonal close-packed monolayer polystyrene colloidal crystals

[0056] Using a 1mL medical syringe, 0.5mL of a mixture of deionized water and ethanol containing polystyrene microspheres was drawn and slowly and evenly diffused onto a pre-prepared deionized water surface, thus obtaining a monolayer of polystyrene microspheres on the gas-liquid surface. Then, 1-2 drops of a 10wt% sodium dodecyl sulfate aqueous solution were added, resulting in a hexagonal close-packed polystyrene microsphere monolayer. Using tweezers, a glass substrate with a photoresist film was tilted and submerged below the water surface, then quickly lifted, transferring the hexagonal close-packed polystyrene microsphere monolayer structure onto the photoresist film. The substrate was then dried at room temperature.

[0057] Example 5: Fabrication of a nano-frustum array of photoresist

[0058] The sample prepared in Example 4 was placed in an oxygen reactive plasma etching machine. Under the conditions of etching temperature of 20°C, etching power of 100W, etching gas pressure of 10mTorr, and oxygen flow rate of 60sccm, the etching was carried out for 230s. The diameter of the polystyrene microspheres gradually decreased, and the photoresist at the bottom was etched into a frustum array. The etching was stopped before the polystyrene microspheres completely disappeared.

[0059] Example 6: Vapor Deposition Method for Metallic Gold and Silver

[0060] The sample prepared in Example 5 was placed on the sample stage of the vacuum coating chamber and subjected to a 5×10⁻⁶ molten metal coating process. -4 At a vacuum degree of Pa, with A gold film 1 is thermally evaporated and deposited at a deposition rate of 30° and an incident angle of 30°. A silver film 1 is then deposited on the opposite side of the gold film 1, forming the first layer structure of the Swiss roll. The substrate is then rotated 90° counterclockwise or clockwise, and a gold film 2 is thermally evaporated and deposited. A silver film 2 is then deposited on the opposite side of the gold film 2, forming the second layer structure of the Swiss roll. Finally, a gold film 3 is deposited on the opposite side of the gold film 1 to form a continuous Swiss roll. The angle between the substrate normal and the deposition direction, i.e., the incident angle, is 30°. The deposition thickness of gold films 1, 2, 3, 1, and 2 is 15 nm.

[0061] Example 7: Preparation of Hollow Chiral Swiss Roll Nanoarray Continuous Film

[0062] The sample prepared in Example 6 was immersed in 5 mL of toluene and ultrasonically treated with 40% power (40W) for 30 s to remove residual polystyrene microspheres. Then it was immersed in anhydrous ethanol for 1 h to remove the photoresist film. It was rinsed with deionized water and air-dried to obtain a hollow nanoscale chiral Swiss roll nanoarray continuous film.

[0063] Experimental Example 8: A Method for Detecting the Polarization-Sensitive Photocatalytic Performance of Nanoscale Swiss Roll Array Films

[0064] The sample prepared in Example 7 was immersed in a Rhodamine B solution with a concentration of 4.79 mg / L and irradiated with left-handed and right-handed polarized light generated by a laser with a wavelength of 532 nm for 12 h, respectively. The sample was taken out of the solution every 2 h and analyzed with a UV-Vis spectrophotometer.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the method of the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the essence of the method of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a nanoscale chiral Swiss roll array continuous film, comprising the following steps: 1) On the hydrophilically treated substrate, spin coat a layer of photoresist at a speed of 2000~5000 rpm, cure at 80~120 °C for 1~2 h, and cool to room temperature to obtain a photoresist film with a thickness of 0.4~2 μm on the substrate. 2) A hydrophobic polystyrene microsphere mixture of deionized water and ethanol was slowly added dropwise to the surface of deionized water to obtain a polystyrene microsphere monolayer on the gas-liquid surface; then an anionic surfactant was added dropwise to obtain a hexagonal close-packed polystyrene microsphere monolayer; the hexagonal close-packed polystyrene microsphere monolayer was transferred to the photoresist film prepared in step 1) and allowed to dry naturally. 3) Place the sample prepared in step 2) in a plasma etching machine. During the etching process, the diameter of the polystyrene microspheres gradually decreases, and the photoresist film at the bottom is etched into a frustum array. 4) Place the sample prepared in step 3) in a vacuum coating chamber and thermally evaporate and deposit gold film 1 at a certain incident angle. Then, deposit silver film 1 on the opposite side of gold film 1. Gold film 1 and silver film 1 form the first layer structure of the Swiss roll. Then, rotate the substrate counterclockwise or clockwise by 90° and thermally evaporate and deposit gold film 2 at the same incident angle. Then, deposit silver film 2 on the opposite side of gold film 2. Gold film 2 and silver film 2 form the second layer structure of the Swiss roll. Finally, deposit gold film 3 on the opposite side of gold film 1 so that the gold film forms a continuous Swiss roll. The angle between the substrate normal direction and the deposition direction, i.e., the incident angle, is 10°~60°. The deposition thickness of gold film 1, gold film 2, gold film 3, silver film 1, and silver film 2 is 10~70 nm. 5) Immerse the sample prepared in step 4) in 3-25 mL of toluene and sonicate it at 40% power for 20-60 s to remove the residual polystyrene microspheres that have not been etched away. 6) Transfer the sample prepared in step 5) into anhydrous ethanol and soak for 1-3 h to remove the photoresist film, rinse with deionized water and air dry to obtain a hollow nanoscale chiral Swiss roll nanoarray continuous film, wherein the array continuous film is composed of continuous hollow Swiss roll structural units.

2. The method for preparing a nanoscale chiral Swiss roll array continuous film as described in claim 1, characterized in that: The substrate in step 1) is a glass plate or a quartz plate.

3. The method for preparing a nanoscale chiral Swiss roll array continuous film as described in claim 1, characterized in that: The polystyrene microspheres in step 2) have a diameter of 0.3~3 μm.

4. The method for preparing a nanoscale chiral Swiss roll array continuous film as described in claim 1, characterized in that: The hydrophobic polystyrene microspheres in step 2) were obtained by the method described in the following steps. (1) Add 4-8 mL of deionized water to a deionized water dispersion of 1-5 mL polystyrene microspheres with a concentration of 1-15 wt% and a diameter of 0.3-3 μm, sonicate at 100% power for 20-30 min, and then centrifuge at 4000-8900 rpm for 20-30 min to remove the supernatant. (2) Add 4-8 mL of deionized water to the precipitate of lower polystyrene microspheres, sonicate at 100% power for 20-30 min, and then centrifuge at 4000-8900 rpm for 20-30 min to remove the supernatant. (3) Repeat step (2) 6 to 10 times; (4) Add 4-8 mL of a 1:1 mixture of ethanol and deionized water to the precipitate of the lower polystyrene microspheres, sonicate at 100% power for 20-30 min, and then centrifuge at 4000-8900 rpm for 20-30 min to remove the supernatant. (5) Repeat step (4) 10 to 15 times; (6) Add 1-2 mL of a 1:1 mixture of ethanol and deionized water to the precipitate of the lower layer of polystyrene microspheres, and sonicate at 100% power for 60-120 min to obtain a hydrophobic polystyrene microsphere mixture of deionized water and ethanol.

5. The method for preparing a nanoscale chiral Swiss roll array continuous film as described in claim 1, characterized in that: Step 3) The etching atmosphere for plasma etching is oxygen, the gas flow rate is 10~60 sccm, the etching pressure is 5~10 mTorr, the etching temperature is 5~25 °C, the etching power is 100~500 W, and the etching time is 60~300 s.

6. The method for preparing a nanoscale chiral Swiss roll array continuous film as described in claim 1, characterized in that: Step 4) The vacuum degree for thermal evaporation deposition is 2 × 10⁻⁶. -4 ~5×10 -4 Pa, deposition rate is 0.8~1.5 Å / s.

7. A nanoscale chiral Swiss roll array continuous film, characterized in that: It is prepared by the method described in any one of claims 1 to 6.

8. The application of the nanoscale chiral Swiss roll array continuous film as described in claim 7 in polarization-sensitive photocatalysis.

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