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

Abstract

The invention discloses a preparation method of photodynamic and photo-thermal synergistic antibacterial degradable super-hydrophobic paper, which specifically comprises the following steps: under a dark condition, dipping a paper base in a sodium periodate solution for 4-12 hours, taking out, washing with water, and drying; soaking the dried paper base in a protein solution for 20 minutes, taking out the paper base, cleaning the paper base with water, and drying the paper base; an absolute ethyl alcohol solution containing MOF particles is applied to the paper base through a spray gun, and the paper base is washed with water and dried; repeating the steps for 3-5 times; dipping the paper base in a polydimethylsiloxane-ethyl acetate solution for 10-20 minutes, taking out the paper base, and drying the paper base to obtain the degradable super-hydrophobic paper, the degradable super-hydrophobic paper prepared by the preparation method disclosed by the invention has excellent water vapor and oxygen barrier property, strong mechanical property and better photodynamic synergistic photo-thermal antibacterial property; and moreover, the preparation method is simple, low in cost and free of special equipment requirements, and has huge application potential in the field of food packaging.

Description

Technical Field

[0001] The present invention belongs to the field of food packaging materials, and specifically relates to a preparation method and application of degradable super-hydrophobic paper with synergistic antibacterial effects of photodynamic and photothermal properties. Background Art

[0002] With the increasing environmental pollution caused by petroleum-based plastics and the growing demand for warehousing and logistics, people's demand for food packaging that can maintain food quality for a long time and is friendly to the human body and the environment is also growing. As one of the most widely used and oldest food packaging materials, cellulose-based paper materials have attracted people's attention again. However, due to the high hydrophilicity, poor water resistance and inability to effectively extend the shelf life of paper packaging, its application in the new era of food packaging is limited. In order to improve the hydrophobicity and functionality of the paper surface, people often stack and extrude it with plastic or treat it with chemical reagents. Although the treated paper can effectively extend the shelf life and play a certain antibacterial role, the hidden human and environmental risks behind it have caused widespread concern among consumers. Therefore, the development of a new type of paper-based packaging has become a common call of current consumers. Inspired by the "lotus leaf effect" in nature, people have noticed the excellent performance of superhydrophobic surfaces in constructing functional surfaces, self-cleaning, and anti-bacterial adhesion. Therefore, biomimetic construction of superhydrophobic surfaces has become an important research direction in the field of food packaging in recent years.

[0003] The construction of super-hydrophobic surface must meet the two requirements of higher surface roughness and lower surface energy. CN116856202A is a preparation method and application of a super-hydrophobic paper for antibacterial preservation, and it is proposed to introduce nano silver particles to construct surface roughness, so that the super-hydrophobic paper has a spectrum antibacterial function. However, the nanoparticles used will cause a potential threat to the human body that cannot be ignored due to their inevitable agglomeration phenomenon, and are not suitable for food packaging. CN111549568B is a preparation method of a super-hydrophobic paper, and it is proposed to add octadecylamine emulsion to pulp, and add tannic acid and aluminum chloride hexahydrate to form microcapsules, and the obtained super-hydrophobic paper refers to having good durability, but the functionality is single, which is not suitable for current food packaging applications. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for preparing a degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial, which is simple and environmentally friendly. The present invention uses a biodegradable paper base as a substrate, uses a human-friendly bridging agent, and MOF particles with photothermal and photocatalytic effects to construct a rough surface. Polydimethylsiloxane is used as a low surface energy modification agent to prepare a degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial. The super-hydrophobic paper of the present invention has excellent water vapor and oxygen barrier properties, strong mechanical properties, good photodynamic and photothermal synergistic sterilization functions, high environmental and mechanical stability, and can achieve full biodegradation in a natural environment.

[0005] The preparation of the degradable super-hydrophobic paper of the present invention is as follows: (1) Immerse the paper substrate in sodium periodate solution for 4-12 hours in a dark environment, then wash with water and dry; The concentration of the sodium periodate solution is 4-10 g / L, the drying temperature is 37° C., and the drying time is 12-24 h; the paper base is filter paper, cardboard, corrugated paper or paperboard; (2) After drying, the paper base is immersed in the protein solution for 20 minutes, then taken out, washed with water and dried; The protein in the protein solution is one or more of collagen, gelatin, and soy protein isolate, the protein concentration is 4-8 g / L, the drying temperature is 60-80° C., and the drying time is 10-20 min; (3) using a spray gun to apply the anhydrous ethanol solution containing MOF particles to the paper substrate in step (2), washing with water and drying; 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, the MOF particle concentration is 10-14 g / L, the drying temperature is 60-80° C., and the drying time is 10-20 min; PDA@ZIF-8 is prepared by dissolving 7.44 g zinc nitrate hexahydrate and 0.274 g dopamine hydrochloride in 10 mL water to prepare solution A; dissolving 12.7 g 2-methylimidazole (or 1.45 g terephthalic acid) in 90 mL water to prepare solution B, pouring solution A into solution B, stirring for 1 h, standing for 1 h, centrifuging and drying; 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 placing the obtained brown solid product in 100 mL of an aqueous solution containing 0.3 g of dopamine after the reaction is completed. After standing at room temperature for 24 h, the product is centrifuged and dried. PDA@UiO-66 is prepared by adding 0.25 g zirconium tetrachloride, 0.18 g terephthalic acid and 5.8 g acetic acid to 100 mL DMF, heating at 120°C for 24 h, placing the obtained white solid product in 100 mL of an aqueous solution containing 0.3 g dopamine after the reaction is completed, placing it at room temperature for 24 h, and then centrifuging and drying it. (4) Repeat steps (2) and (3) 3-5 times; (5) immersing the paper base obtained in step (4) in a polydimethylsiloxane-ethyl acetate solution for 10-20 minutes, taking it out and drying it to obtain a degradable super-hydrophobic food packaging paper; The mass concentration of polydimethylsiloxane in the polydimethylsiloxane-ethyl acetate solution is 1-10%, the drying temperature is 80-100° C., and the drying time is 3-5 hours.

[0006] Another object of the present invention is to apply the degradable super-hydrophobic paper prepared by the above method in food packaging.

[0007] Beneficial effects of the present invention: The present invention constructs a microstructure on the surface of paper by layer-by-layer assembly, and at the same time, the surface microstructure is firmly bonded to the paper through Schiff base reaction, so that the prepared paper exhibits good mechanical properties and stability; through surface polydimethylsiloxane modification, it exhibits good superhydrophobic properties, and the water contact angle can reach 162.1°. Since MOF particles have good photodynamic and photothermal properties, the paper prepared by the present invention has an antibacterial and sterilization rate of up to 99.9% against Escherichia coli and Staphylococcus aureus under near-infrared light at 880nm, showing excellent antibacterial properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 The scanning electron microscope images of the degradable super-hydrophobic paper prepared in Example 1 of the present invention at different magnifications; Figure 2 This is a high-resolution image of the water contact angle of the degradable super-hydrophobic paper prepared in Example 1 of the present invention; Figure 3 The temperature change of the degradable super-hydrophobic paper prepared in Example 1 of the present invention under near-infrared light irradiation at 880 nm at different optical densities; Figure 4 The antibacterial effect of the degradable super-hydrophobic paper prepared in Example 1 of the present invention on Escherichia coli after being irradiated with 880nm near-infrared light for 15min is shown on a coated plate (with Escherichia coli without any treatment as a blank control); Figure 5Antibacterial effect of the degradable super-hydrophobic paper prepared in Example 1 of the present invention on Staphylococcus aureus after irradiation with 880nm near-infrared light for 15min (Staphylococcus aureus without any treatment is used as blank control) Figure 6 The figure shows the influence of the concentration change of the ethanol solution of PDA@ZIF-8 on the wetting properties of the superhydrophobic paper of the present invention.

[0009] Figure 7 The figure shows the influence of the number of immersion-spraying cycles on the wetting properties of the super-hydrophobic paper of the present invention. DETAILED DESCRIPTION

[0010] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Unless otherwise specified, the reagents in the embodiments are conventional commercially available reagents. Example 1: Preparation of degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial properties 1. Weigh 2g of sodium periodate and dissolve it in 500mL of deionized water to obtain a 4g / L sodium periodate solution. Immerse the filter paper in it and place it in the dark at room temperature for 4 hours. Take it out and wash it with water and dry it at 37℃ for 12 hours. 2. Weigh 2 g of collagen and dissolve it in 500 mL of deionized water to obtain a 4 g / L collagen solution. Immerse the filter paper in step 1 and place it at room temperature for 20 min. Take it out, wash it with water and dry it at 60°C for 20 min. 3. Dissolve 7.44 g zinc nitrate hexahydrate and 0.274 g dopamine hydrochloride in 10 mL water to prepare solution A; dissolve 12.7 g 2-methylimidazole in 90 mL water to prepare solution B, pour solution A into solution B, stir for 1-2 h, let stand for 1 h, centrifuge and dry to obtain PDA@ZIF-8; 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 with water and dry at 60 °C for 20 min; 4. Step 2 dipping and step 3 spraying are one cycle, and the operation is repeated 3 times; 5. Prepare a 1% polydimethylsiloxane-ethyl acetate solution, immerse the filter paper dried in step 4 in the solution for 10 minutes, take it out and dry it at 80°C for 5 hours to obtain a degradable super-hydrophobic paper; its scanning electron microscopy image is shown in Figure 1 ,As can be seen from the figure, after the super-hydrophobic modification, the surface roughness of the filter paper has been significantly improved, and the porous structure of the paper has also been improved, which helps it not be wetted by water.

[0011] The water contact angle of the degradable super-hydrophobic paper prepared in this embodiment was measured by the sessile drop method, and the results are shown in the following table. Figure 2 The water contact angle of the degradable super-hydrophobic paper in this embodiment is 156°, indicating that it has excellent hydrophobic ability.

[0012] The antibacterial ability of the degradable super-hydrophobic paper prepared in this example was tested as follows: The prepared degradable super-hydrophobic paper was cut into a circle 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 the 10% 3 The bacterial suspension was dropped onto a circular paper and the optical density was 0.75 W / cm at 880 nm. 2 After irradiation with near-infrared light for 15 min, 5 mL of LB liquid culture medium was added and cultured at 37 °C and 180 r / min for 6 h. The cells were diluted 10 times three times, 100 μL was taken to plate, cultured at 37 °C for 12 h and counted; the blank control was ordinary filter paper; from Figure 4 , 5 It can be seen that after the degradable super-hydrophobic paper of this embodiment is irradiated with 880nm near-infrared light, there is almost no colony growth on the plate coated with the culture solution of the degradable super-hydrophobic paper of this embodiment. Compared with the blank control, the antibacterial rate of the degradable super-hydrophobic paper against Escherichia coli and Staphylococcus aureus is 99.9%, which has excellent antibacterial properties. The temperature change results of degradable super-hydrophobic paper under near-infrared light irradiation at 880nm with different optical densities are shown in Figure 3 As can be seen from the figure, as the near-infrared light irradiation time of the degradable superhydrophobic paper increases, the temperature of the irradiated area continues to increase, showing a good photothermal effect, and the maximum temperature reached also increases with the increase of optical density.

[0013] Example 2: Preparation of degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial properties 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 it and place it in the dark at room temperature for 8 hours. Take it out and wash it with water and dry it at 37℃ for 18 hours. 2. Weigh 3g of gelatin and dissolve it in 500mL of deionized water to obtain a 6g / L gelatin solution. Immerse the cardboard in it and place it at room temperature for 20 minutes. Take it out, wash it, and dry it at 70℃ for 15 minutes. 3. Dissolve 4.05 g of ferric chloride hexahydrate and 1.24 g of terephthalic acid in 100 mL of N,N-dimethylformamide (DMF), heat at 120 °C for 24 h. After the reaction, place the obtained brown solid product in 100 mL of an aqueous solution containing 0.3 g of dopamine, place it at room temperature for 24 h, and then centrifuge and dry it to obtain PDA@MIL-101-Fe. Prepare 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; 4. Step 2 dipping and step 3 spraying are one cycle, and the operation is repeated 4 times; 5. Prepare a polydimethylsiloxane-ethyl acetate solution with a mass concentration of 5%, immerse the cardboard dried in step 4 in the solution for 15 minutes, take it out and dry it at 90°C for 4 hours to obtain a degradable super-hydrophobic paper; 6. The antibacterial ability of the degradable super-hydrophobic paper prepared in this embodiment was detected by referring to the method in Example 1. The antibacterial effect was the same as in Example 1. The water contact angle of the degradable super-hydrophobic paper prepared in this embodiment was detected, and the water contact angle was 159.2°.

[0014] Example 3: Preparation of degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial properties 1. Weigh 5 g of sodium periodate and dissolve it in 500 mL of deionized water to obtain a 10 g / L sodium periodate solution. Immerse the corrugated paper in it and place it in the dark at room temperature for 12 h. Take it out and wash it with water and dry it at 37 ° C for 24 h. 2. Weigh 4 g of soy protein isolate and dissolve it in 500 mL of deionized water to obtain 8 g / L collagen solution. Immerse the corrugated paper in it and place it at room temperature for 20 min. Take it out and wash it with water and dry it at 80°C for 10 min. 3. Add 0.25g zirconium tetrachloride, 0.18g terephthalic acid and 5.8g acetic acid to 100mL DMF and heat at 120° for 24h. After the reaction, place the obtained white solid product in 100mL of aqueous solution containing 0.3g dopamine, place it at room temperature for 24h, and then centrifuge and dry it to obtain PDA@UiO-66; Prepare 14 g / L PDA@UiO-66 solution, apply it to the corrugated paper obtained in step 2 using a spray gun, wash with water and dry at 80 °C for 10 min; 4. Step 2 dipping and step 3 spraying are one cycle, and the operation is repeated 5 times; 5. Prepare a polydimethylsiloxane-ethyl acetate solution with a mass concentration of 10%, immerse the corrugated paper dried in step 4 in the solution for 20 minutes, take it out and dry it at 100° C. for 3 hours to obtain a degradable super-hydrophobic paper; 6. The antibacterial ability of the degradable super-hydrophobic paper prepared in this embodiment was detected by referring to the method in Example 1. The antibacterial effect was the same as in Example 1. The water contact angle of the degradable super-hydrophobic paper prepared in this embodiment was detected, and the water contact angle was 158.6°.

[0015] Example 4: Experimental study on the effects of key steps and condition parameters in the method of the present invention on the quality of the obtained antibacterial and fresh-keeping super-hydrophobic paper 1. Effect of different PDA@ZIF-8-ethanol solution concentrations on the wetting properties of superhydrophobic paper (1) The preparation of the degradable superhydrophobic paper in this embodiment is the same as that in Example 1, except that in step 3, 6 g / L, 8 g / L, 10 g / L, 12 g / L, and 14 g / L of PDA@ZIF-8 ethanol solutions are prepared respectively; (2) The water contact angle of the prepared biodegradable superhydrophobic paper was measured using the sessile drop method. A 5 μl water droplet was dropped onto the surface of the paper sample. The image of the droplet was captured by a high-resolution camera, and then the contact angle between the droplet and the sample was analyzed. Results Figure 6 ,It can be seen from the figure that when the concentration of PDA@ZIF-8 solution is 6g / L, the water contact angle is 156°, and the PDA@ZIF-8 particles attached to the paper base are not enough 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 surface of the degradable superhydrophobic paper also increases, reaching the highest at a concentration of 10g / L. Therefore, when the concentration of PDA@ZIF-8 solution is 10-14g / L, the degradable superhydrophobic paper has superhydrophobic properties.

[0016] 2. The influence of different immersion times on the wetting properties of the superhydrophobic paper of the present invention.

[0017] (1) The preparation of the degradable super-hydrophobic paper in this embodiment is the same as that in Example 1, except that step 4 is repeated 1, 2, 3, 4, or 5 times; (2) Testing the water contact angle of the prepared biodegradable superhydrophobic paper using the sessile drop method Results Figure 7 , it can be seen from the figure that when the number of immersions is 1-2 times, the water contact angle is 130.4°-147.28°, and the PDA@ZIF-8 particles attached to the paper substrate are not enough to build sufficient roughness and cannot achieve superhydrophobicity. As the number of immersions increases, the static contact angle of the degradable superhydrophobic paper surface also increases, and finally tends to be stable, so the optimal number of repeated immersions is 3-5 times.

[0018] 3. Performance testing of the degradable super-hydrophobic paper prepared in the above embodiment.

[0019] The water vapor permeability, oxygen permeability and mechanical properties of the degradable super-hydrophobic paper prepared in Example 1 were tested; the water vapor permeability was tested according to the method in GB1037-1988; the oxygen permeability was tested according to the method in GB / T19789-2005; the tensile strength was tested according to the method in GB13022-91, with unmodified filter paper as a blank control; the results are shown in Tables 1 and 2; Table 1 Water vapor transmission rate and oxygen transmission rate of products

[0020] Table 2 Tensile strength and elongation at break of products

[0021] As can be seen from the table, the water vapor permeability and oxygen permeability of the degradable super-hydrophobic 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 degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial properties, characterized in that: Here are the steps: (1) Immerse the paper substrate in sodium periodate solution for 4-12 hours in a dark environment, then wash with water and dry; (2) After drying, the paper base is immersed in the protein solution for 20 minutes, then taken out, washed with water and dried; (3) using a spray gun to apply the anhydrous ethanol solution containing MOF particles to the paper substrate in step (2), washing with water and drying; (4) Repeat steps (2) and (3) 3-5 times; (5) Immerse the paper base obtained in step (4) in a polydimethylsiloxane-ethyl acetate solution for 10-20 minutes, take it out and dry it to obtain a degradable super-hydrophobic paper.

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

3. The method for preparing the photodynamic and photothermal synergistic antibacterial degradable super-hydrophobic food packaging paper according to claim 1, characterized in that: The protein in the protein solution is one or more of collagen, gelatin, and soy protein isolate, the protein concentration is 4-8 g / L, the drying temperature is 60-80° C., and the drying time is 10-20 min.

4. The method for preparing the degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial properties according to claim 1, characterized in that: 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, the MOF particle concentration is 10-14 g / L, the drying temperature is 60-80° C., and the drying time is 10-20 min.

5. The method for preparing the degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial properties according to claim 1, characterized in that: The mass concentration of polydimethylsiloxane in the polydimethylsiloxane-ethyl acetate solution is 1-10%, the drying temperature is 80-100° C., and the drying time is 3-5 h.

6. The method for preparing the degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial properties according to claim 1, characterized in that: The paper base is filter paper, cardboard, corrugated paper or paperboard.

7. Use of the degradable super-hydrophobic paper prepared by the method for preparing the degradable super-hydrophobic paper with photodynamic and photothermal synergistic antibacterial properties according to any one of claims 1 to 6 in food packaging.

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