Preparation method and application of photodynamic and photothermal synergistic antibacterial degradable super-hydrophobic paper

Abstract

The application discloses a preparation method of a degradable super-hydrophobic paper with synergistic antibacterial effect of photodynamic and photothermal, and specifically comprises the following steps: under light-proof conditions, immersing a paper base in a sodium periodate solution for 4-12 hours, taking out, washing with water and drying; after drying, immersing the paper base in a protein solution for 20 minutes, taking out, washing with water and drying; using a spray gun to apply a MOF particle-containing anhydrous ethanol solution to the paper base, washing with water and drying; repeating the above steps for 3-5 times; immersing the paper base in a polydimethylsiloxane-ethyl acetate solution for 10-20 minutes, taking out and drying to obtain the degradable super-hydrophobic paper; the prepared degradable super-hydrophobic paper has excellent water vapor and oxygen barrier properties, strong mechanical properties, and good photodynamic synergistic photothermal antibacterial performance; efficient and rapid sterilization is realized, the preparation method is simple, the cost is low, no special equipment is required, and the degradable super-hydrophobic paper has great application potential in the field of food packaging.

Description

Technical Field

[0001] This invention belongs to the field of food packaging materials, specifically relating to a method for preparing and applying a biodegradable superhydrophobic paper with synergistic photodynamic and photothermal antibacterial properties. Background Technology

[0002] With the increasing environmental pollution caused by petroleum-based plastics and the growing demands of warehousing and logistics, the need for food packaging that can maintain food quality for extended periods and is both human- and environmentally friendly is constantly growing. Cellulose-based paper materials, as one of the most widely used and oldest food packaging materials, have once again attracted attention. However, the high hydrophilicity, poor water resistance, and inability to effectively extend shelf life of paper packaging limit its application in the modern food packaging field. To improve the hydrophobicity and functionality of paper surfaces, it is often stacked and extruded with plastics or treated with chemical reagents. Although treated paper can effectively extend shelf life and provide some antibacterial effects, the hidden risks to human health and the environment have raised widespread concerns among consumers. Therefore, developing a new type of paper-based packaging has become a common demand from consumers. Inspired by the "lotus effect" in nature, people have noticed the excellent performance of superhydrophobic surfaces in constructing functional surfaces, self-cleaning, and antibacterial adhesion. Therefore, biomimetic construction of superhydrophobic surfaces has become an important research direction in the food packaging field in recent years.

[0003] Constructing superhydrophobic surfaces requires meeting two key requirements: high surface roughness and low surface energy. CN116856202A describes a method for preparing and applying antibacterial and preservative superhydrophobic paper, proposing the introduction of silver nanoparticles to create surface roughness, thereby giving the superhydrophobic paper a spectral antibacterial function. However, the unavoidable aggregation of the nanoparticles poses a significant potential threat to human health, making it unsuitable for food packaging. CN111549568B describes a method for preparing superhydrophobic paper, proposing the addition of octadecylamine emulsion to pulp, along with tannic acid and aluminum chloride hexahydrate to form microcapsules. The resulting superhydrophobic paper exhibits good durability but has limited functionality, making it unsuitable for current food packaging applications. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a simple and environmentally friendly method for preparing biodegradable superhydrophobic paper with synergistic photodynamic and photothermal antibacterial properties. This invention uses a biodegradable paper base as the substrate, employs a human-friendly bridging agent, and utilizes MOF particles with photothermal and photocatalytic effects to construct a roughened surface. Polydimethylsiloxane is used as a low surface energy modifying agent to prepare the biodegradable superhydrophobic paper with synergistic photodynamic and photothermal antibacterial properties. The superhydrophobic paper of this invention possesses excellent water vapor and oxygen barrier properties, strong mechanical properties, good synergistic photodynamic and photothermal antibacterial function, high environmental and mechanical stability, and can achieve full biodegradability in the natural environment.

[0005] The biodegradable superhydrophobic paper of this invention is prepared as follows:

[0006] (1) Under light-protected conditions, immerse the paper base in sodium periodate solution for 4-12 hours, then remove it, wash it with water, and dry it.

[0007] The concentration of the sodium periodate solution is 4-10 g / L, the drying temperature is 37℃, and the drying time is 12-24 h; the paper base is filter paper, cardboard, corrugated paper, or paperboard.

[0008] (2) After drying, the paper base is immersed in the protein solution for 20 minutes, then taken out, washed with water and dried;

[0009] The protein solution contains one or more of collagen, gelatin, and soy protein isolate, with a protein concentration of 4-8 g / L, a drying temperature of 60-80℃, and a drying time of 10-20 min.

[0010] (3) Apply an anhydrous ethanol solution containing MOF particles to the paper base from step (2) using a spray gun, wash with water and dry;

[0011] The anhydrous ethanol solution containing MOF particles contains one or more of PDA@ZIF-8, PDA@MIL-101-Fe, and PDA@UiO-66, with a MOF particle concentration of 10-14 g / L, a drying temperature of 60-80℃, and a drying time of 10-20 min.

[0012] PDA@ZIF-8 is prepared by dissolving 7.44g of zinc nitrate hexahydrate and 0.274g of dopamine hydrochloride in 10mL of water to obtain solution A; dissolving 12.7g of 2-methylimidazole (or 1.45g of terephthalic acid) in 90mL of water to obtain solution B; pouring solution A into solution B, stirring for 1 hour, letting stand for 1 hour, centrifuging and drying to obtain the final product.

[0013] PDA@MIL-101-Fe is prepared by dissolving 4.05 g of ferric chloride hexahydrate and 1.24 g of terephthalic acid in 100 mL of N,N-dimethylformamide (DMF), heating at 120 °C for 24 h, and after the reaction is completed, placing the resulting brown solid product in 100 mL of an aqueous solution containing 0.3 g of dopamine, leaving it at room temperature for 24 h, and then centrifuging and drying it.

[0014] PDA@UiO-66 is prepared by adding 0.25g zirconium tetrachloride, 0.18g terephthalic acid and 5.8g acetic acid to 100mL of DMF, heating at 120℃ for 24h, and after the reaction is completed, placing the resulting white solid product in 100mL of aqueous solution containing 0.3g dopamine, leaving it at room temperature for 24h, and then centrifuging and drying it.

[0015] (4) Repeat steps (2) and (3) 3-5 times;

[0016] (5) The paper base obtained in step (4) is impregnated in polydimethylsiloxane-ethyl acetate solution for 10-20 min, taken out and dried to obtain biodegradable superhydrophobic food packaging paper;

[0017] The polydimethylsiloxane-ethyl acetate solution has a polydimethylsiloxane mass concentration of 1-10%, a drying temperature of 80-100℃, and a drying time of 3-5 hours.

[0018] Another objective of this invention is to apply the biodegradable superhydrophobic paper prepared by the above method to food packaging.

[0019] The beneficial effects of this invention are:

[0020] This invention constructs a microstructure on the paper surface through a layer-by-layer assembly process, and simultaneously achieves a strong bond between the surface microstructure and the paper through a Schiff base reaction. The resulting paper exhibits excellent mechanical properties and stability. Surface modification with polydimethylsiloxane imparts superior superhydrophobicity, achieving a water contact angle of 162.1°. Due to the excellent photodynamic and photothermal properties of MOF particles, the paper prepared by this invention exhibits a 99.9% inhibition rate against Escherichia coli and Staphylococcus aureus under near-infrared light at 880 nm, demonstrating excellent antibacterial performance. Attached Figure Description

[0021] Figure 1 These are scanning electron microscope images of the biodegradable superhydrophobic paper prepared in Example 1 of the present invention at different magnifications;

[0022] Figure 2 This is a high-resolution image of the water contact angle of the biodegradable superhydrophobic paper prepared in Example 1 of the present invention;

[0023] Figure 3The temperature change of the biodegradable superhydrophobic paper prepared in Example 1 of the present invention under near-infrared light irradiation at 880 nm at different optical densities;

[0024] Figure 4 The antibacterial effect of the biodegradable superhydrophobic paper prepared in Example 1 of the present invention on Escherichia coli after being irradiated with 880nm near-infrared light for 15 min is shown in the plate diagram (with untreated Escherichia coli as a blank control).

[0025] Figure 5 The antibacterial effect of the biodegradable superhydrophobic paper prepared in Example 1 of this invention on Staphylococcus aureus after irradiation with 880nm near-infrared light for 15 min is shown in the plate diagram (with untreated Staphylococcus aureus as a blank control).

[0026] Figure 6 The effect of changes in the concentration of the ethanol solution of PDA@ZIF-8 on the wetting properties of the superhydrophobic paper of this invention.

[0027] Figure 7 The effect of the number of impregnation-spraying cycles on the wetting properties of the superhydrophobic paper of this invention. Detailed Implementation

[0028] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Unless otherwise specified, the reagents used in the embodiments are all commercially available reagents.

[0029] Example 1: Preparation of biodegradable superhydrophobic paper with synergistic photodynamic and photothermal antibacterial properties

[0030] 1. Weigh 2g of sodium periodate and dissolve it in 500mL of deionized water to obtain a 4g / L sodium periodate solution. Immerse filter paper in the solution and place it in the dark at room temperature for 4 hours. After removing the filter paper, wash it with water and dry it at 37℃ for 12 hours.

[0031] 2. Weigh 2g of collagen and dissolve it in 500mL of deionized water to obtain a collagen solution of 4g / L. Immerse the filter paper from step 1 in the solution and place it at room temperature for 20 minutes. After removing it, wash it with water and dry it at 60℃ for 20 minutes.

[0032] 3. Dissolve 7.44g of zinc nitrate hexahydrate and 0.274g of dopamine hydrochloride in 10mL of water to prepare solution A; dissolve 12.7g of 2-methylimidazole in 90mL of water to prepare solution B. Pour solution A into solution B, stir for 1-2 hours, let stand for 1 hour, centrifuge and dry to obtain PDA@ZIF-8;

[0033] Prepare a 10 g / L anhydrous ethanol solution of PDA@ZIF-8, apply it to the filter paper prepared in step 2 using a spray gun, wash it with water and dry it at 60°C for 20 min.

[0034] 4. Step 2 (immersion) and step 3 (spraying) constitute one cycle, and the operation is repeated 3 times;

[0035] 5. Prepare a 1% (w / w) polydimethylsiloxane-ethyl acetate solution. Immerse the dried filter paper from step 4 in the solution for 10 minutes, then remove and dry at 80°C for 5 hours to obtain biodegradable superhydrophobic paper. Its scanning electron microscope image is shown below. Figure 1 As can be seen from the figure, after superhydrophobic modification, the surface roughness of the filter paper is significantly improved, and the porous structure of the paper is also improved, which helps it to resist water wetting.

[0036] The water contact angle of the biodegradable superhydrophobic paper prepared in this embodiment was measured using the seat drop method, and the results are shown in the figure. Figure 2 In this embodiment, the water contact angle of the biodegradable superhydrophobic paper is 156°, indicating that it has excellent hydrophobic ability.

[0037] The antibacterial ability of the biodegradable superhydrophobic paper prepared in this embodiment was tested using the following method:

[0038] The prepared biodegradable superhydrophobic paper was cut into circles with a diameter of 13 mm, irradiated with ultraviolet light on both sides for 15 min each, and then placed at the bottom of a test tube. 100 μL of a 10% concentration solution was then added. 3 A bacterial suspension was dropped onto a circular piece of paper. The light was emitted at 880 nm with a density of 0.75 W / cm². 2 After irradiation under near-infrared light for 15 min, 5 mL of LB liquid medium was added and cultured at 37℃ and 180 r / min for 6 h. The medium was serially diluted 10-fold three times, and 100 μL was plated and cultured at 37℃ for 12 h and counted. The blank control was ordinary filter paper.

[0039] from Figure 4 , 5 As can be seen from the above, after being irradiated with 880nm near-infrared light, the biodegradable superhydrophobic paper in this embodiment showed almost no bacterial growth on the plate coated with the culture medium. Compared with the blank control, the biodegradable superhydrophobic paper had an inhibition rate of 99.9% against Escherichia coli and Staphylococcus aureus, demonstrating excellent antibacterial properties.

[0040] The temperature change results of biodegradable superhydrophobic paper under near-infrared light irradiation at 880 nm at different optical densities are shown in the figure. Figure 3 As can be seen from the figure, the temperature of the irradiated area of ​​the biodegradable superhydrophobic paper increases with the increase of near-infrared light irradiation time, showing a good photothermal effect. The highest temperature reached also increases with the increase of light density.

[0041] Example 2: Preparation of biodegradable superhydrophobic paper with synergistic photodynamic and photothermal antibacterial properties

[0042] 1. Weigh 3.5g of sodium periodate and dissolve it in 500mL of deionized water to obtain a 7g / L sodium periodate solution. Immerse the cardboard in the solution and place it in the dark at room temperature for 8 hours. After removing it, wash it with water and dry it at 37℃ for 18 hours.

[0043] 2. Weigh 3g of gelatin and dissolve it in 500mL of deionized water to obtain a 6g / L gelatin solution. Immerse the cardboard in the solution and leave it at room temperature for 20 minutes. After removing it, wash it and dry it at 70℃ for 15 minutes.

[0044] 3. Dissolve 4.05 g of ferric chloride hexahydrate and 1.24 g of terephthalic acid in 100 mL of N,N-dimethylformamide (DMF) and heat at 120 °C for 24 h. After the reaction is complete, place the resulting brown solid product in 100 mL of an aqueous solution containing 0.3 g of dopamine and let it stand at room temperature for 24 h. Then, centrifuge and dry to obtain PDA@MIL-101-Fe.

[0045] Prepare a 12 g / L PDA@MIL-101-Fe solution, apply it to the cardboard obtained in step 2 using a spray gun, wash with water and dry at 70°C for 15 min;

[0046] 4. Step 2 (immersion) and step 3 (spraying) constitute one cycle, and the operation is repeated 4 times;

[0047] 5. Prepare a 5% (w / w) polydimethylsiloxane-ethyl acetate solution, immerse the dried cardboard from step 4 in the solution for 15 min, remove it and dry it at 90°C for 4 h to obtain biodegradable superhydrophobic paper.

[0048] 6. The antibacterial ability of the biodegradable superhydrophobic paper prepared in this embodiment was tested according to the method of Example 1. The antibacterial effect was the same as in Example 1. The water contact angle of the biodegradable superhydrophobic paper prepared in this embodiment was tested and found to be 159.2°.

[0049] Example 3: Preparation of biodegradable superhydrophobic paper with synergistic photodynamic and photothermal antibacterial properties

[0050] 1. Weigh 5g of sodium periodate and dissolve it in 500mL of deionized water to obtain a 10g / L sodium periodate solution. Immerse corrugated paper in the solution and place it in the dark at room temperature for 12 hours. After removing it, wash it with water and dry it at 37℃ for 24 hours.

[0051] 2. Weigh 4g of soy protein isolate and dissolve it in 500mL of deionized water to obtain a collagen solution of 8 g / L. Soak corrugated paper in the solution and leave it at room temperature for 20 min. After removing it, wash it with water and dry it at 80℃ for 10 min.

[0052] 3. Add 0.25 g zirconium tetrachloride, 0.18 g terephthalic acid, and 5.8 g acetic acid to 100 mL of DMF and heat at 120°C for 24 h. After the reaction is complete, place the resulting white solid product in 100 mL of an aqueous solution containing 0.3 g dopamine, let it stand at room temperature for 24 h, and then centrifuge and dry to obtain PDA@UiO-66;

[0053] Prepare a 14 g / L PDA@UiO-66 solution, apply it to the corrugated paper obtained in step two using a spray gun, wash with water and dry at 80°C for 10 min;

[0054] 4. Step 2 (immersion) and step 3 (spraying) constitute one cycle, and the operation is repeated 5 times;

[0055] 5. Prepare a 10% (w / w) polydimethylsiloxane-ethyl acetate solution, immerse the dried corrugated paper from step 4 in the solution for 20 min, remove it and dry it at 100℃ for 3 h to obtain biodegradable superhydrophobic paper.

[0056] 6. The antibacterial ability of the biodegradable superhydrophobic paper prepared in this embodiment was tested according to the method of Example 1. The antibacterial effect was the same as in Example 1. The water contact angle of the biodegradable superhydrophobic paper prepared in this embodiment was tested and found to be 158.6°.

[0057] Example 4: Experiment on the Influence of Key Steps and Condition Parameters in the Method of the Invention on the Quality of the Prepared Antibacterial and Preservative Superhydrophobic Paper

[0058] 1. Effect of different concentrations of PDA@ZIF-8-ethanol solution on the wetting properties of superhydrophobic paper

[0059] (1) The preparation of the biodegradable superhydrophobic paper in this embodiment is the same as in Example 1, except that in step 3, ethanol solutions of PDA@ZIF-8 with concentrations of 6 g / L, 8 g / L, 10 g / L, 12 g / L, and 14 g / L are prepared respectively.

[0060] (2) The water contact angle of the biodegradable superhydrophobic paper was detected by the seat drop method. 5 μl of water was dropped onto the paper sample surface, and the droplet image was taken by a high-resolution camera. Then the contact angle between the droplet and the sample was analyzed.

[0061] See results Figure 6As can be seen from the figure, when the concentration of PDA@ZIF-8 solution is 6 g / L, the water contact angle is 156°. The PDA@ZIF-8 particles attached to the paper substrate are insufficient to cover the cellulose nanofibers, and superhydrophobicity cannot be achieved. As the concentration of PDA@ZIF-8 gradually increases, the static contact angle of the biodegradable superhydrophobic paper surface also increases, reaching the highest at a concentration of 10 g / L. Therefore, when the concentration of PDA@ZIF-8 solution is 10-14 g / L, the biodegradable superhydrophobic paper has superhydrophobic properties.

[0062] 2. The effect of different impregnation times on the wetting properties of the superhydrophobic paper of the present invention.

[0063] (1) The preparation of the biodegradable superhydrophobic paper in this embodiment is the same as in Example 1, except that step 4 is repeated 1, 2, 3, 4, and 5 times;

[0064] (2) The water contact angle of the prepared biodegradable superhydrophobic paper was measured by the seat drop method.

[0065] See results Figure 7 As shown in the figure, when the number of impregnations is 1-2, the water contact angle is 130.4°-147.28°. The PDA@ZIF-8 particles attached to the paper substrate are insufficient to create enough roughness to achieve superhydrophobicity. As the number of impregnations gradually increases, the static contact angle of the biodegradable superhydrophobic paper surface also increases and eventually tends to stabilize. Therefore, the optimal number of repeated impregnations is 3-5 times.

[0066] 3. Performance testing of the biodegradable superhydrophobic paper prepared in the above embodiments.

[0067] The water vapor transmission rate, oxygen transmission rate, and mechanical properties of the biodegradable superhydrophobic paper prepared in Example 1 were tested. The water vapor transmission rate was tested according to the method in GB1037-1988; the oxygen transmission rate was tested according to the method in GB / T19789-2005; and the tensile strength was tested according to the method in GB13022-91. Unmodified filter paper was used as a blank control. The results are shown in Tables 1 and 2.

[0068] Table 1. Water vapor transmission rate and oxygen transmission rate of the product

[0069]

[0070] Table 2 Tensile Strength and Elongation at Break of Products

[0071]

[0072] As can be seen from the table, the water vapor transmission rate and oxygen transmission rate of the biodegradable superhydrophobic paper prepared in Example 1 are both lower than those of the blank control filter paper, indicating that its gas barrier properties have been greatly improved. Its tensile strength and elongation at break are also higher than those of the filter paper, indicating that its mechanical properties have also been improved.

Claims

1. A method for preparing a biodegradable superhydrophobic paper with synergistic photodynamic and photothermal antibacterial properties, characterized in that: The steps are as follows: (1) Under light-protected conditions, immerse the paper base in sodium periodate solution for 4-12 hours, then remove it, wash it with water, and dry it. (2) After drying, the paper base is immersed in the protein solution for 20 minutes, then taken out, washed with water and dried; (3) Apply an anhydrous ethanol solution containing MOF particles to the paper base from step (2) using a spray gun, wash with water and dry; (4) Repeat steps (2) and (3) 3-5 times; (5) The paper base obtained in step (4) is immersed in polydimethylsiloxane-ethyl acetate solution for 10-20 min, taken out and dried to obtain biodegradable superhydrophobic paper; The protein solution contains one or more of collagen, gelatin, and soy protein isolate, with a protein concentration of 4-8 g / L, a drying temperature of 60-80℃, and a drying time of 10-20 min. The MOF particles in the anhydrous ethanol solution containing MOF particles are one or more of PDA@ZIF-8, PDA@MIL-101-Fe, and PDA@UiO-66, with a MOF particle concentration of 10-14 g / L, a drying temperature of 60-80℃, and a drying time of 10-20 min. The mass concentration of polydimethylsiloxane in the polydimethylsiloxane-ethyl acetate solution is 1-10%, the drying temperature is 80-100℃, and the drying time is 3-5 h.

2. The method for preparing the biodegradable superhydrophobic paper with synergistic photodynamic and photothermal antibacterial properties according to claim 1, characterized in that: The concentration of sodium periodate solution is 4-10 g / L, the drying temperature is 37℃, and the drying time is 12-24 h.

3. The method for preparing the biodegradable superhydrophobic paper with synergistic photodynamic and photothermal antibacterial properties according to claim 1, characterized in that: The paper base is filter paper, cardboard, corrugated paper, or paperboard.

4. The application of the biodegradable superhydrophobic paper prepared by the method of photodynamic and photothermal synergistic antibacterial process as described in any one of claims 1-3 in food packaging.

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