Preparation method and application of a carbon dot flexible high-transmittance visible light anti-ultraviolet film

Abstract

The present invention discloses a method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film and its application, and relates to the field of paper protection technology. S1. Dissolve a linear polymer, an amino-containing small molecule organic compound, a carboxylic acid or a sugar in a mass ratio of 1:0.5-2.5:0.5-2.5 in a solvent and stir evenly, react at 100°C-300°C for 4-48 hours to obtain a mixture I, and subject the mixture I to centrifugal filtration, dialysis, and freeze-drying to obtain carbon dots; S2. Dissolve the prepared carbon dots in a solvent and stir evenly to prepare a 0.01mg / ml-100mg / ml carbon dot solution; dissolve the film-forming polymer material in water and heat to dissolve to prepare a 0.01mg / ml-100mg / ml film-forming polymer solution. Mix and stir the film-forming polymer solution and the carbon dot solution in a volume ratio of 10:1-1:10, and finally dry to form a film. The film prepared by the invention has excellent ultraviolet absorption characteristics and hardly absorbs in the visible light region. When applied to paper protection, it can prevent ultraviolet damage to the paper without affecting the appearance and viewing effect of the paper.

Description

Technical Field

[0001] The present invention relates to the technical field of paper protection, and in particular to a preparation method of a carbon dot flexible high-transmittance visible light anti-ultraviolet film and an application thereof. Background Art

[0002] Paper artifacts such as ancient books, archives, calligraphy, and paintings have witnessed the history of human civilization and have very important historical value and research significance. However, due to the influence of storage and transportation conditions, many papers have yellowed, acidified, brittle, and even cracked, which seriously affects the life and value of paper artifacts.

[0003] An important reason for paper aging is the damage of high-energy ultraviolet rays to paper. The chromophores in paper easily absorb ultraviolet rays in sunlight to produce free radicals, and induce a series of chain reactions leading to the generation of acidic groups and the cleavage of the cellulose main chain, resulting in the acidification, oxidation, yellowing of paper, and the reduction of strength and life. Therefore, it is of great significance to study the anti-ultraviolet protection of paper.

[0004] At present, most of the anti-ultraviolet protection materials for paper use graphene, titanium dioxide and some organic matter. PengTian et al. used graphene oxide as a UV protector and sprayed the protector on paper samples to protect rice paper. et al. proposed a coating composed of starch, methyl cellulose and nano-TiO2, which uses the ultraviolet blocking performance of TiO2 to protect paper through a coating method. The nano-composite coating with an appropriate concentration has an anti-ultraviolet effect on paper. Jicheng Xu et al. used the ultraviolet absorber 2-(2′-hydroxy-3′, 5′-di-tert-butylphenyl)-5-chloro-benzothiazole to prepare a series of polymer material films for protecting rice paper. However, there are relatively few materials currently used for ultraviolet protection of paper, and the composition and appearance of the paper may be changed during the protection process. In order to solve the above problems, the present invention provides a method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film and its application in the anti-ultraviolet protection of paper. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film and its application, so as to solve the problems mentioned in the above background technology. The prepared film has excellent ultraviolet absorption properties and almost no absorption in the visible light region. When used for paper protection, it can prevent ultraviolet damage to the paper without affecting the appearance and ornamental effect of the paper.

[0006] To achieve the above object, the present invention provides a method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film, which specifically comprises the following steps:

[0007] S1. Preparation of carbon dots: dissolving a linear polymer, an amino-containing small molecule organic compound, a carboxylic acid or a sugar in a solvent, stirring the mixture to obtain a mixture I, and subjecting the mixture I to centrifugal filtration, dialysis and freeze drying to obtain carbon dots;

[0008] S2. Preparation of a carbon dot flexible, highly transparent, visible light, UV-proof film: dissolve the carbon dots prepared in step S1 in a solvent and stir to prepare a 0.01 mg / ml to 100 mg / ml carbon dot solution; then dissolve a film-forming polymer material in water to prepare a 0.01 mg / ml to 100 mg / ml film-forming polymer solution; mix the above-mentioned film-forming polymer solution and the carbon dot solution, stir evenly, and dry to form a film.

[0009] Preferably, in step S1, the mass ratio of the linear polymer, the amino-containing small molecule organic compound, the carboxylic acid or the sugar is 1:0.5-2.5:0.5-2.5; the reaction temperature is 100°C-300°C, and the reaction time is 4-48h.

[0010] Preferably, in step S1, the linear polymer is one of polyethyleneimine, polyvinyl alcohol and polyacrylamide.

[0011] Preferably, in step S1, the amino-containing small molecule organic compound is one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, ethylenediamine and urea.

[0012] Preferably, in step S1, the carboxylic acid is one of citric acid, malic acid and salicylic acid; and the sugar is one of glucose, chitosan and fructose.

[0013] Preferably, in steps S1 and S2, the solvent is one of deionized water, anhydrous ethanol, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and cyclohexane.

[0014] Preferably, in step S2, the volume ratio of the film-forming polymer solution to the carbon dot solution is 10:1 to 1:10.

[0015] Preferably, in step S2, the film-forming polymer material is one or more of polyvinyl alcohol, polyacrylic acid, polyethyleneimine, polyvinylidene fluoride, cellulose acetate, and cellulose nitrate.

[0016] The present invention also provides a carbon dot flexible high-transmittance visible light anti-ultraviolet film prepared by the above preparation method.

[0017] The present invention also provides the use of the prepared carbon dot flexible high-transmittance visible light anti-ultraviolet film in the anti-ultraviolet protection of paper.

[0018] Therefore, the present invention provides a method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film and its application, and the specific beneficial effects are as follows:

[0019] (1) The carbon dots prepared by the present invention are a kind of zero-dimensional nanomaterials, which have the advantages of wide range of raw materials, simple preparation, good biocompatibility, and especially excellent ultraviolet absorption and photoluminescence properties;

[0020] (2) The present invention uses carbon dots and a film-forming polymer material to prepare a flexible anti-ultraviolet film. The carbon dots have good ultraviolet absorption characteristics, and the film-forming polymer material has excellent structural strength and oil and solvent resistance. The prepared film has excellent anti-ultraviolet light aging and degradation performance, and has almost no absorption in the visible light region. The transmittance in the visible light region is high but does not affect the visual effect of the paper.

[0021] (3) When the film prepared by the present invention is used for paper protection, it can prevent ultraviolet rays from damaging the paper without affecting the appearance and ornamental effect of the paper, and will not change the original composition of the paper to cause damage. At the same time, the synthesis method is simple and easy to control, and the operation method for protecting the paper is simple.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a transmission electron microscope (TEM) image of the carbon dots prepared in Example 1 of the method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film of the present invention;

[0024] Figure 2 The ultraviolet-visible absorption spectrum of the carbon dots prepared in Example 1 of the method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film of the present invention;

[0025] Figure 3 The UV-visible transmittance spectra of the films prepared in Example 1, Example 6 and Example 7 of the method for preparing a carbon dot flexible high-transmittance visible light anti-UV film of the present invention at different carbon dot contents. DETAILED DESCRIPTION

[0026] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The drying and film-forming method in the present invention is one of natural drying at room temperature, heating drying, vacuum heating drying and freeze drying.

[0028] Embodiment 1

[0029] This embodiment provides a method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film, comprising the following steps:

[0030] S1. Dissolve 0.5 g polyethyleneimine, 1 g citric acid and 0.5 g o-phenylenediamine in 20 ml deionized water, place the solution on a magnetic stirrer and stir at 400 rpm for uniform mixing, then transfer the solution to a reactor and react at 160° C. for 12 hours. Take the supernatant of the mixture, centrifuge, filter, dialyze and freeze-dry to obtain carbon dots.

[0031] S2. Take 0.01 g of the carbon dots prepared in step S1 and dissolve it in 20 ml of deionized water, place it on a magnetic stirrer and stir it at 400 rpm to prepare a 0.5 mg / ml carbon dot solution. Dissolve 1 g of polyvinyl alcohol in 20 ml of deionized water and heat it to 95°C to completely dissolve it to prepare a 0.05 g / ml polyvinyl alcohol solution. Mix the polyvinyl alcohol solution and the carbon dot solution and stir them evenly, and heat and dry them at 60°C to form a film.

[0032] Embodiment 2

[0033] The difference between this embodiment and the first embodiment is that the mass of citric acid in the first embodiment is changed to 2 g, and the rest is the same as the first embodiment, which will not be repeated here.

[0034] Embodiment 3

[0035] The difference between this embodiment and the first embodiment is that the mass of citric acid in the first embodiment is changed to 0.5 g, and the rest is the same as the first embodiment, which will not be repeated here.

[0036] Embodiment 4

[0037] The difference between this embodiment and the first embodiment is that 0.5 g of polyethyleneimine in the first embodiment is replaced with 0.5 g of polyvinyl alcohol, and the rest is the same as the first embodiment, which will not be repeated here.

[0038] Embodiment 5

[0039] The difference between this embodiment and the first embodiment is that 0.5 g of o-phenylenediamine in the first embodiment is replaced by 0.5 g of m-phenylenediamine, and the rest is the same as the first embodiment, which will not be repeated here.

[0040] Embodiment 6

[0041] The difference between this embodiment and the first embodiment is that the carbon dots in the first embodiment are changed to 0.001 g, and the rest are the same as the first embodiment, which will not be repeated here.

[0042] Embodiment 7

[0043] The difference between this embodiment and the first embodiment is that the carbon dots in the first embodiment are changed to 0.1 g, and the rest are the same as the first embodiment, which will not be repeated here.

[0044] Embodiment 8

[0045] The only difference between this embodiment and the first embodiment is that 1 g of polyvinyl alcohol in the first embodiment is replaced by a mixture of 0.5 g of polyvinyl alcohol and 0.5 g of cellulose acetate, and the rest is the same as the first embodiment, which will not be repeated here.

[0046] Embodiment 9

[0047] The only difference between this embodiment and the first embodiment is that the 20 ml of deionized water for dissolving the carbon dots in step S2 of the first embodiment is replaced with 20 ml of anhydrous ethanol, and the rest is the same as the first embodiment, which will not be repeated here.

[0048] Test example

[0049] The carbon dot film prepared in Example 1, Example 6 and Example 7 was cut into 2 cm*2 cm square pieces, and the rice paper was cut into 2 cm*2 cm square pieces, and the carbon dot film was covered on the rice paper for UV protection. On this basis, the rice paper was changed into handmade bamboo paper, kraft paper, mulberry paper or machine-made paper.

[0050] Experimental testing

[0051] (a) If Figure 1 FIG. 1 is a transmission electron microscope (TEM) image of carbon dots in Example 1. It can be seen from the image that the carbon dots are quasi-spherical in structure and have an average particle size of 1.59 nm.

[0052] (ii) The carbon dots prepared in the preparation process of Example 1 were prepared into aqueous solutions at 0.02 mg / ml, 0.04 ml / ml, 0.06 mg / ml, 0.08 mg / ml, and 0.10 mg / ml, and UV-visible absorption spectra were tested. The results are shown in Figure 2 As shown by Figure 2 It can be seen that carbon dots have excellent absorption characteristics in the ultraviolet band, with obvious ultraviolet absorption in the range of 300nm-400nm. With the increase of carbon dot concentration, the absorption intensity increases significantly, and the absorption wavelength becomes slightly wider; there is less absorption in the band greater than 400nm.

[0053] (III) The carbon dot films prepared in the preparation process of Example 1, Example 6 and Example 7 were tested for UV-visible absorption spectrum. The results are as follows: Figure 3 As shown by Figure 3It can be seen that the transmittance of the carbon dot film in the range of 200nm-400nm is relatively low, and the transmittance of the film with a high carbon dot concentration is even lower; in the band greater than 400nm, the transmittance of the film increases sharply, indicating that the film has good transmittance in the visible light band.

[0054] (IV) Anti-ultraviolet light aging degradation test

[0055] The carbon dot films obtained in Example 1, Example 6 and Example 7 were cut into 2 cm*2 cm square pieces, covered on 2 cm*2 cm square rice paper pieces and handmade bamboo paper pieces, and placed in a 40W UV aging box. At the same time, the square rice paper pieces and handmade bamboo paper pieces not covered with carbon dot films were placed in a 40W UV aging box for UV aging for 30 days. The pH of the rice paper pieces was measured using a Sanxin pH5F flat pen pH meter.

[0056] The experimental results show that the pH of the rice paper protected by the carbon dot film in Example 1 is reduced from 6.8 to 6.6, the pH of the rice paper protected by the carbon dot film in Example 6 is reduced from 6.8 to 6.3, the pH of the rice paper protected by the carbon dot film in Example 7 is reduced from 6.8 to 6.7, and the pH of the rice paper without carbon dot film protection is reduced from 6.8 to 5.4. In addition, the pH of the handmade bamboo paper protected by the carbon dot film in Example 1 is reduced from 6.1 to 5.3, the pH of the handmade bamboo paper protected by the carbon dot film in Example 6 is reduced from 6.1 to 4.7, the pH of the handmade bamboo paper protected by the carbon dot film in Example 7 is reduced from 6.1 to 5.7, and the pH of the handmade bamboo paper without carbon dot film protection is reduced from 6.1 to 4.3. It shows that the protection of the carbon dot film makes the ultraviolet degradation of paper slower. And the higher the content of carbon dots in the carbon dot film, the slower the ultraviolet degradation of paper.

[0057] In summary, the present invention discloses a method for preparing a carbon dot flexible high-transmittance visible light anti-UV film and its application. The carbon dot flexible high-transmittance visible light anti-UV film is prepared by a simple method of mixing carbon dots with film-forming polymer materials. The prepared film has excellent resistance to ultraviolet light aging and degradation, has high transmittance in the visible light region, does not affect the visual effect of paper, and will not change the original composition of the paper to cause damage.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film, characterized in that: The specific steps include: S1. Preparation of carbon dots: dissolving a linear polymer, an amino-containing small molecule organic compound, a carboxylic acid or a sugar in a solvent, stirring the mixture to obtain a mixture I, and subjecting the mixture I to centrifugal filtration, dialysis and freeze drying to obtain carbon dots; S2. Preparation of a carbon dot flexible high-transmittance visible light anti-ultraviolet film: dissolving the carbon dots prepared in step S1 in a solvent and stirring to prepare a 0.01 mg / ml-100 mg / ml carbon dot solution; then dissolving a film-forming polymer material in water to prepare a 0.01 mg / ml-100 mg / ml film-forming polymer solution; mixing the above film-forming polymer solution and the carbon dot solution and stirring them evenly, and drying to form a film; In step S1, the mass ratio of the linear polymer, the amino-containing small molecule organic compound, and the carboxylic acid or sugar is 1:0.5~2.5:0.5~2.5; In step S1, the linear polymer is one of polyethyleneimine, polyvinyl alcohol and polyacrylamide.

2. The method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film according to claim 1, characterized in that: In step S1, the reaction temperature is 100° C. to 300° C., and the reaction time is 4 to 48 hours.

3. The method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film according to claim 1, characterized in that: In the step S1, the small molecule organic compound containing an amino group is one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, ethylenediamine, and urea.

4. The method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film according to claim 1, characterized in that: In the step S1, the carboxylic acid is one of citric acid, malic acid and salicylic acid; the sugar is one of glucose, chitosan and fructose.

5. The method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film according to claim 1, characterized in that: In the steps S1 and S2, the solvent is one of deionized water, anhydrous ethanol, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and cyclohexane.

6. The method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film according to claim 1, characterized in that: In the step S2, the volume ratio of the film-forming polymer solution to the carbon dot solution is 10:1 to 1:

10.

7. The method for preparing a carbon dot flexible high-transmittance visible light anti-ultraviolet film according to claim 1, characterized in that: In the step S2, the film-forming polymer material is one or more of polyvinyl alcohol, polyacrylic acid, polyethyleneimine, polyvinylidene fluoride, cellulose acetate, and cellulose nitrate.

8. A carbon dot flexible high-transmittance visible light anti-ultraviolet film, characterized in that: The carbon dot flexible high-transmittance visible light anti-ultraviolet film is prepared by the preparation method described in any one of claims 1-7.

9. The carbon dot flexible high-transmittance visible light anti-ultraviolet film according to claim 8, characterized in that: The carbon dot flexible high-transmittance visible light anti-ultraviolet film is used for anti-ultraviolet protection of paper.

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