Edible mycorrhizal sugar complex-graphene conductive film and preparation method thereof

Abstract

The present invention belongs to the field of composite materials technology, specifically relating to an edible mycorrhizal glycoconjugate-graphene conductive film and its preparation method. This invention uses chitosan-glucan complex (CGC), a root glycoconjugate extracted from the mycorrhizae of Flammulina velutipes, as raw material. Extracting CGC from the mycorrhizae requires only mild acid and alkali treatment to remove components such as proteins, minerals, and lipids, while also minimizing damage to the CGC and improving its purity. The prepared CGC, when used as a dispersant, improves graphene agglomeration. Compared to graphene without CGC, at the optimal concentration of CGC added, the median particle size decreased by 43.11%, and the absolute value of the zeta potential increased by 160.07%. The addition of CGC to graphene significantly enhances its dispersibility, improving the tensile strength and conductivity of the CGC-graphene film.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and particularly relates to an edible mycorrhizal sugar complex-graphene conductive film and a preparation method thereof. Background Art

[0002] Chitin-Glucan Complex (CGC), also known as chitin-glucan, is composed of chitin ( β -1,4-poly-N-acetyl-D-glucosamine) and β -High-purity biopolymer composed of two different polysaccharides represented by 1,3-D-glucan; β The flexibility of glucan and the rigidity of chitin complement each other, providing a natural nanocomposite structure. Currently, CGC is mainly derived from crustaceans such as shrimp and crab.

[0003] With the rapid development of my country's Flammulina velutipes industry, annual production has steadily increased. However, the production process produces a significant amount of the mushroom's stipe base (commonly known as the mycorrhiza). During harvest, these stipe bases, due to their high cellulose content and being less tender and crisp than the upper portion, are often discarded. They are then sold in bulk to fertilizer companies for composting or mixed with coal for direct combustion in boilers. However, the mycorrhizae of Flammulina velutipes are also rich in CGCs, accounting for approximately 10-15% of the total mass of the mushroom. This treatment of the mycorrhizae undoubtedly results in a significant waste of resources.

[0004] As a new type of two-dimensional nanocarbon material, graphene is a sheet-like material composed of carbon atoms in sp2 hybrid orbitals. It has excellent mechanical and electrical performance and is widely used in various flexible electronic devices. However, due to the existence of π - π Covalent bonds and strong van der Waals forces. When the graphene concentration is high, graphene is easy to aggregate and difficult to disperse; when the graphene content is low, although its dispersibility is improved, the conductivity of the composite material is significantly reduced, which greatly limits the application of graphene.

[0005] If CGC and graphene can be used as raw materials to produce a material that has both the toughness of CGC and the good conductivity of graphene without the agglomeration problem, it will be of great significance to the field. Summary of the Invention

[0006] In order to solve the above-mentioned technical problems, the present invention provides an edible mycorrhizal glycoconjugate-graphene film and a preparation method thereof. The edible mycorrhizal glycoconjugate extracted from edible mycorrhizae is used as a raw material and combined with graphene as a dispersant, thereby improving the agglomeration problem of graphene. The edible mycorrhizal glycoconjugate-graphene film (CGC-graphene film) obtained by the blending method has good conductive properties.

[0007] The edible mycorrhizal sugar complex-graphene conductive film provided by the present invention is prepared using the edible mycorrhizal sugar complex and graphene as raw materials.

[0008] The edible mycorrhizal sugar complex is prepared by the following method:

[0009] S1 edible fungus root pretreatment:

[0010] The edible fungus roots are cut into segments, allowed to stand under saturated water vapor, and then the high-speed steam is used to entrain the material and quickly eject it after pressure relief, and the ejected material is collected; the edible fungi disclosed in the present invention include but are not limited to Enoki mushrooms, and may also be other types of edible fungi;

[0011] S2 Preparation of edible mycorrhizal sugar complex:

[0012] S21 alcohol treatment: drying the material obtained in S1, crushing it, adding ethanol solution, leaching it, and filtering and collecting the residue;

[0013] S22 water treatment: drying the filter residue in S21, crushing it, adding water for extraction, and filtering and collecting the filter residue;

[0014] S23 deproteinization: take the filter residue from S22, add alkaline solution to treat, then centrifuge, wash the precipitate with water until neutral, and then wash with buffer to obtain alkali-insoluble precipitate;

[0015] S24 Demineralization: Take the alkali-insoluble precipitate in S23, add acid solution to treat, centrifuge, and wash the precipitate with water until neutral; then add alkali solution to treat, centrifuge, wash the precipitate with water until neutral, wash with buffer solution, centrifuge to obtain a precipitate;

[0016] S25 dialysis: The precipitate obtained in S24 is dialyzed with a dialysis membrane and dried to obtain an edible mycorrhizal glycocomplex. The edible mycorrhizal glycocomplex prepared by S1-S2 has a purity of >90%, a chitin content of 30%-40%, and a glucan content of 60%-70%. In fact, the main components of the edible mycorrhizal glycocomplex are chitin and glucan (accounting for more than 90%), and the other components are mainly protein, fat, and ash. The edible mycorrhizal glycocomplex mentioned below is actually a chitin-glucan complex, also known as "CGC";

[0017] Preferably, in the above S1, the edible fungi are cut into segments of 3 to 5 cm, placed under saturated water vapor of 0.7 to 1.5 MPa for 5 to 7 minutes, and then the pressure is released within 1 second;

[0018] In S21, a 95% ethanol solution was added at a weight-to-volume ratio of (0.9-1.1) g to (14-16) L, and ultrasonic extraction was performed at 28-32 °C for 25-35 min.

[0019] In S22, distilled water was added at a weight-to-volume ratio of (0.9-1.1) g to (14-16) L, and the mixture was extracted at 80-90 °C for 1.8-2.2 h.

[0020] In S23, 0.9-1.1 M NaOH solution was added at a weight-to-volume ratio of (0.8-1.2) g to (18-22) L, and the mixture was treated at 70-80 °C for 2-3 h. The mixture was centrifuged and the precipitate was washed with water until neutral. The precipitate was then washed with PBS buffer at pH 7.4 to obtain an alkali-insoluble precipitate.

[0021] In S24, the alkali-insoluble precipitate in S23 is taken, and a 0.9-1.1% HCl solution is added at a weight-to-volume ratio of 1 g to 20 L, and the mixture is treated at 60°C for 1.8-2.2 h, centrifuged, and the precipitate after centrifugation is washed with water until neutral; a 0.9-1.1 M NaOH solution is added at a weight-to-volume ratio of 0.8-1.2 g to 18-22 L, and the mixture is treated at 70-80°C for 2-3 h, centrifuged, and the precipitate after centrifugation is washed with water until neutral, then washed with phosphate buffer, and centrifuged to obtain a precipitate;

[0022] In S25, the precipitate finally obtained in S24 was dialyzed with flowing water for 46 to 50 hours using a dialysis membrane with a molecular weight cutoff of 1000 Da. The liquid in the dialysis bag was freeze-dried to obtain an edible mycorrhizal saccharide complex.

[0023] More preferably, in S1, the edible fungi are cut into segments of 3 to 5 cm, placed under saturated water vapor at 0.7 to 1.5 MPa for 5 to 7 minutes, and then the pressure is released within 1 second;

[0024] In S21, a 95% ethanol solution was added at a weight-to-volume ratio of 1 g solid to 15 L, and ultrasonic extraction was performed at 30 °C for 30 min.

[0025] In S22, distilled water was added at a weight-to-volume ratio of 1 g solid to 15 L, and the mixture was extracted at 85 °C for 2 h.

[0026] In S23, 1 M NaOH was added at a weight-to-volume ratio of 1 g solid to 20 L, and the mixture was treated at 75 °C for 2.5 h. The mixture was centrifuged, and the precipitate was washed with water until neutral, and then washed with PBS buffer, with a pH of about 7.4.

[0027] In S24, the alkali-insoluble precipitate in S23 was taken, and a 1% HCl solution was added at a weight-to-volume ratio of 1 g:20 L to the solid-liquid ratio, and the mixture was treated at 60°C for 2 h. The mixture was centrifuged, and the precipitate after centrifugation was washed with water until neutral. A 1 M NaOH solution was added at a weight-to-volume ratio of 1 g:20 L to the solid-liquid ratio, and the mixture was treated at 75°C for 2.5 h. The mixture was centrifuged, and the precipitate after centrifugation was washed with water until neutral. The precipitate was then washed with phosphate buffer and centrifuged to obtain a precipitate.

[0028] In S25, the precipitate finally obtained in S24 was dialyzed with flowing water for 48 h using a dialysis membrane with a molecular weight cutoff of 1000 Da. The liquid in the dialysis bag was freeze-dried to obtain an edible mycorrhizal saccharide complex.

[0029] The method for preparing the edible mycorrhizal sugar complex-graphene conductive film comprises the following steps:

[0030] (1) dissolving the edible mycorrhizal glycoconjugate prepared by the method in S1-S2 above in an acetic acid solution and homogenizing the solution to obtain an edible mycorrhizal glycoconjugate nanofiber solution;

[0031] (2) adding graphene to the edible mycorrhizal glycocomplex nanofiber solution in (1), performing mechanical stirring and ultrasonic treatment once, and obtaining a uniformly dispersed edible mycorrhizal glycocomplex-graphene dispersion;

[0032] (3) Adding gelatin and glycerol to the edible mycorrhizal glycoconjugate-graphene dispersion, performing secondary mechanical stirring to obtain a mixed solution, then pouring the mixed solution onto a plastic substrate, heating it to dry and form it, and obtaining an edible mycorrhizal glycoconjugate-graphene film. The substrate may also be a substrate of other materials, provided that it does not affect or react with the mixed solution.

[0033] The beneficial effects of the present invention are:

[0034] (1) The present invention only requires mild acid and alkali treatment to extract CGC from edible mycorrhizae to remove components such as protein and lipids from the mycorrhizae, and the use of low-concentration sodium hydroxide and hydrochloric acid solutions can also reduce damage to CGC. Compared with the extraction method of crustaceans, the present invention's method for extracting CGC from edible mycorrhizae is more environmentally friendly and efficient. The CGC prepared by extracting and purifying the steam-pretreated Flammulina velutipes mycorrhizae has a purity of more than 90%, a glucan content of 60% to 70%, and an improved chitin deacetylation degree. This series of changes in properties improves the applicability of CGC for use in thin films.

[0035] (2) The CGC prepared by the present invention can improve the agglomeration problem of graphene when used as a dispersant. Compared with graphene without CGC, the graphene with the optimal concentration of CGC is better.

[0036] Bottom: The median particle size of graphene decreased by 43.11%, and the absolute value of Zeta potential increased by 160.07%. The dispersibility of graphene was greatly improved after adding CGC, which is conducive to the formation of an efficient graphene conductive network, thereby improving the conductive properties of the CGC-graphene film. The CGC-graphene film prepared by the present invention has good conductive properties and excellent mechanical properties. Compared with the single graphene film without adding CGC, under the optimal film preparation process conditions: the tensile strength increased by 62.21%, reaching 136.34 MPa; the conductivity reached 213.34 s / m, an increase of 57.35 times.

[0037] (3) The present invention uses edible mycorrhizae as the raw material for extracting and preparing CGC, reusing discarded edible mycorrhizae resources, realizing the high-value transformation of low-value waste, reducing production costs, and providing a new idea for the preparation of CGC. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Gas chromatograms of CGC prepared in the present invention (Example 1.5, denoted as CGCs; Comparative Example 1, denoted as CGCr); wherein a is a monosaccharide standard, b is the hydrochloric acid hydrolysis product of CGC, and c is the trifluoroacetic acid hydrolysis product;

[0039] Figure 2 The deacetylation degree diagram of CGC prepared by the present invention; wherein a is titration method and b is infrared spectroscopy method;

[0040] Figure 3 Graph showing the effect of the amount of CGC added on the dispersion properties of graphene in the present invention; wherein, a is the median particle size analysis of the CGCs-graphene solution; b is the Zeta potential analysis of the CGCs-graphene solution;

[0041] Figure 4SEM images of the plane (A) and cross-section (a) of the edible mycorrhizal saccharide complex film of the present invention (Comparative Example 4); SEM images of the plane (B) and cross-section (a) of the graphene film (Comparative Example 5); SEM images of the plane (C) and cross-section (c) of the edible mycorrhizal saccharide complex-graphene film (Example 2.2);

[0042] Figure 5 The tensile strength and elongation at break of the edible mycorrhizal saccharide complex-graphene film (a), the edible mycorrhizal saccharide complex film (b), and the graphene film (c) of the present invention;

[0043] Figure 6 It is the electrical conductivity of the edible mycorrhizal sugar complex-graphene film in the present invention. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the present invention, the present invention will be further explained in conjunction with specific embodiments.

[0045] Example 1 Preparation of Chitosan-Glucan Complex (CGC)

[0046] Example 1.1

[0047] Taking Flammulina velutipes as an example, the preparation method of edible mycorrhizal sugar complex-graphene conductive film is as follows:

[0048] S1 Mycorrhizal pretreatment: Fresh Enoki mushroom mycorrhizae were cut into 3-5 cm pieces. The treated samples were placed in a 0.7 MPa saturated steam environment for 5 minutes, and then the pressure was released within 1 second. The high-speed steam was used to entrain the material and the ejected material was quickly ejected. The ejected material was collected and set aside for later use.

[0049] S2 Preparation of edible mycorrhizal sugar complex:

[0050] S21 Alcohol treatment: After the material obtained in S1 was dried and crushed, 95% ethanol solution was added at a solid-liquid ratio of 1:15 (g / L), and ultrasonic extraction was performed at 30°C for 30 min. The residue was collected by filtration;

[0051] S22 water treatment: Take the filter residue from S21, add distilled water at a solid-liquid ratio of 1:15 (g / L), extract at 85°C for 2h, and collect the filter residue by filtration;

[0052] S23 deproteinization: Take the filter residue from S22 and add

[0053] Add 1 M NaOH solution, treat with alkali at 75 °C for 2.5 h, centrifuge, take the precipitate after centrifugation, wash with water until neutral, and then wash with pH 7.4 PBS buffer;

[0054] S24 Demineralization: Take the above alkali-insoluble precipitate, add 1% HCl at a solid-liquid ratio of 1:20 (g / L), acidify at 60°C for 2 h, centrifuge, take the precipitate after centrifugation and wash it with water until neutral, and deproteinize the acid-insoluble precipitate again using the same method as S23;

[0055] S25 dialysis: The centrifuged precipitate obtained in S24 was dialyzed with flowing water for 48 h using a dialysis membrane with a molecular weight cutoff of 1000 Da. The liquid in the dialysis bag was taken and freeze-dried to obtain the edible mycorrhizal saccharide complex.

[0056] Example 1.2

[0057] The difference from Example 1.1 is that in step S1, the treated sample is left to stand for 7 minutes under the action of 0.7 MPa saturated water vapor, and the other steps are the same.

[0058] Example 1.3

[0059] The difference from Example 1.2 is that in step S1, the treated sample is left to stand for 5 minutes under the action of 1.5 MPa saturated water vapor, and the other steps are the same.

[0060] Example 1.4

[0061] The difference from Example 1.3 is that in step S1, the treated sample is left to stand for 7 minutes under the action of 1.5 MPa saturated water vapor, and the other steps are the same.

[0062] Example 1.5

[0063] The difference from Example 1.3 is that in step S1, the treated sample is left to stand for 7 min under the action of 1.1 MPa saturated water vapor. The other steps are the same and are recorded as CGCs.

[0064] Example 2 Preparation of edible mycorrhizal sugar complex-graphene film

[0065] Example 2.1

[0066] The edible mycorrhizal glycoconjugate prepared in Example 1.5 was dissolved in a 2 wt% acetic acid solution at a solid-liquid ratio of 1:100 (g / mL), and then dispersed at a speed of 10,000 r / min for 3 min using a homogenizer shearing machine to obtain a 1% glycoconjugate nanofiber solution. Graphene was added to the glycoconjugate nanofiber solution at a solid-liquid ratio of 5:1 (mg / mL), and then mechanically stirred at a speed of 5,000 r / min for 80 min and ultrasonically treated for 1 h to obtain a uniformly dispersed edible mycorrhizal glycoconjugate-graphene dispersion. 0.5% gelatin and 0.25% glycerol were added to the edible mycorrhizal glycoconjugate-graphene dispersion, and mechanically stirred for a second time at 5,000 r / min for 30 min. The mixture was then poured onto a rotating plastic substrate and heated to dry and form, finally obtaining an edible mycorrhizal glycoconjugate-graphene film.

[0067] Example 2.2

[0068] The difference from Example 2.1 is that the edible mycorrhizal glycoconjugate was dissolved in a 2 wt% acetic acid solution at a solid-liquid ratio of 1:50 (g / mL), and then dispersed using a homogenizer at a speed of 10,000 r / min for 3 min to obtain a 2% edible mycorrhizal glycoconjugate nanofiber solution; 1.5% gelatin and 0.75% glycerol were added to the edible mycorrhizal glycoconjugate-graphene dispersion; the other steps were the same.

[0069] Example 2.3

[0070] The difference from Example 2.1 is that the edible mycorrhizal glycoplex was dissolved in a 2 wt% acetic acid solution at a solid-liquid ratio of 1:33 (g / mL), and then dispersed using a homogenizer at a speed of 10,000 r / min for 3 min to obtain a 3% edible mycorrhizal glycoplex nanofiber solution; 2% gelatin and 1% glycerol were added to the edible mycorrhizal glycoplex-graphene dispersion; the other steps were the same.

[0071] Comparative Example 1

[0072] The difference from Example 1 is that the pretreatment in step S1 is not performed, and the fresh mycorrhizae of Flammulina velutipes are dried and crushed before directly proceeding to step S2 to prepare a glycoconjugate, which is recorded as CGCr.

[0073] Comparative Example 2

[0074] The difference from Example 1 is that in step S1, the treated sample is left to stand for 5 minutes under the action of 0.6 MPa saturated water vapor.

[0075] Comparative Example 3

[0076] The difference from Example 1 is that in step S1, the treated sample is left to stand for 7 minutes under the action of 1.6 MPa saturated water vapor.

[0077] Comparative Example 4

[0078] The difference from Example 2.2 is that graphene was not added to the edible mycorrhizal glycocomplex nanofiber solution. The other steps were the same to obtain an edible mycorrhizal glycocomplex film.

[0079] Comparative Example 5

[0080] The difference from Example 2.2 is that the edible mycorrhizal glycoconjugate was not dissolved in the 2 wt % acetic acid solution, and then dispersed at a speed of 10,000 r / min for 3 min using a homogenizer shearing machine to obtain a 0% edible mycorrhizal glycoconjugate nanofiber solution. The other steps were the same to obtain a graphene film.

[0081] Test Example 1

[0082] The extraction rate and purity of CGC obtained in each example and comparative examples 1-3 in Example 1 were measured, and the results are shown in Table 1.

[0083] Wherein, CGC extraction rate = (CGC mass / Flammulina velutipes mycorrhiza mass) × 100%;

[0084] Among them, CGC purity = (chitin content + glucan content) / CGC mass × 100%. The chitin content determination shall refer to GB / T 38479-2021, and the glucan content determination shall refer to QB / T 4572-2021.

[0085] Table 1 Extraction rate and purity of edible mycorrhizal glycoconjugates in different groups

[0086] Group Glycoconjugate yield (%) Purity of sugar complex (%) Example 1.1 11.02±0.15 90.71±0.23 Example 1.2 11.89±0.12 90.57±0.19 Example 1.3 12.58±0.22 91.37±0.31 Example 1.4 12.29±0.17 91.52±0.26 Example 1.5 13.32±0.37 92.32±0.21 Comparative Example 1 8.39±0.29 77.32±0.26 Comparative Example 2 10.21±0.21 84.55±0.21 Comparative Example 3 7.69±0.17 91.70±0.28

[0087] As shown in Table 1, by comparing Examples 1.1-1.5 and Comparative Examples 1-3, it can be seen that the pretreatment of mycorrhizae with S1 in the method of the present invention can significantly improve the purity and yield of the prepared glycoconjugate. When the saturated water vapor pressure during pretreatment is too high, the purity of the prepared glycoconjugate is higher but the yield of the glycoconjugate is significantly reduced. This may be because high temperature causes the hydrolysis of some glycosidic bonds in the glycoconjugate, resulting in a low extraction rate of the glycoconjugate.

[0088] Test Example 2

[0089] The components of the sugar complexes prepared in Example 1.5 and Comparative Example 1 were determined, and the results are shown in Tables 2 and Figure 1 shown.

[0090] The determination methods of chitin and glucan are as follows: the same as in Experiment 1;

[0091] The determination methods for protein, fat and moisture are as follows: ash content refers to the method of GB 5009.4-2016, fat content refers to the method of GB 5009.6-2016, and protein content refers to the method of GB 5009.5-2016.

[0092] In Table 2, the proportions of chitin and glucan refer to the respective proportions of the two components in the pure edible mycorrhizal glycocomplex, that is, the pure edible mycorrhizal glycocomplex after removing other components such as protein, fat, and ash. Taking Example 1.5 in Table 1 as an example, 91.32±0.21% of the components are pure edible mycorrhizal glycocomplex, so the total proportion of chitin and glucan in the above-mentioned pure edible mycorrhizal glycocomplex is 100%. Protein, fat, ash and other substances are the main impurity components of the glycocomplex, which is based on the samples containing impurities in Table 1. For example, taking Example 1.5 in Table 1 as an example, approximately 9% of the components are impurities. The contents of components such as protein, fat, and ash in this impurity are shown in Table 2 below.

[0093] Table 2 Main chemical components of glycoconjugates prepared by different preparation methods

[0094] Group Glucan% Chitosan% protein% Fat% Ash % Comparative Example 1-CGCr 62.50±0.78 37.50±0.88 0.60±0.58 4.79±0.04 0.70±0.54 Example 1-5-CGCs 69.13±0.81 31.87±0.98 0.48±0.50 3.58±0.05 0.42±0.24

[0095] In the above table, the proportion of chitosan and glucan is the proportion of the purity of the glycoconjugate.

[0096] As shown in Table 2, the ratio of glucan to chitin in the CGCr prepared in Comparative Example 1 is

[0097] The chitosan content in the CGCs prepared in Example 1.5 was 62.50:37.50. Compared to CGCs extracted from Tremella fuciformis (72:28) and Lentinus edodes (67:33), the chitosan content in the enoki mushroom mycorrhizal CGCs was higher, and similar to the chitosan content in commercially available glycoconjugate products (30%-50%). The CGCs prepared in Example 1.5 had a glucan-to-chitosan ratio of 69.13:31.78. Compared to the CGCs in Comparative Example 1, the relative content of the glucan component in the CGCs in Example 1.5 increased, while the protein, fat, and ash contents in the CGCs decreased, resulting in higher purity of the CGCs.

[0098] Test Example 3

[0099] The deacetylation degree of the sugar complexes prepared in Example 1.5 and Comparative Example 1 was determined. Figure 2 shown.

[0100] and Figure 2 The corresponding table is as follows:

[0101] Table 3 Comparison of deacetylation degree between the embodiment and the comparative example

[0102]

[0103] Note: Figure 2 In the figure, the diagonal lines are the results of titration testing; the checkered lines are the results of infrared spectroscopy testing.

[0104] like Figure 2 As shown, the deacetylation degrees of the samples prepared in Example 1.5 and Comparative Example 1 were measured by titration and infrared spectroscopy. Deacetylation is one of the most fundamental structural parameters for evaluating chitin-glucan complexes. The deacetylation degrees of CGCr (Comparative Example 1) were 21.78% and 32.19%, respectively, as measured by titration and infrared spectroscopy. Those of CGCs (Example 1.5) were 29.80% and 48.30%, respectively.

[0105] Although there were some differences in the deacetylation degree of CGCs determined by the two methods, the deacetylation degree of CGCs was higher than that of CGCs. This suggests that the pretreatment caused the hydrolysis of some acetyl groups of chitin in the glycoconjugate to produce acetic acid, thereby increasing the deacetylation degree of CGCs.

[0106] Test Example 4

[0107] The particle size and Zeta potential of the dispersions of Examples 2.1-2.3 and Comparative Example 5 were compared. Figure 3 shown.

[0108] and Figure 3 The corresponding table is as follows:

[0109] Table 4 Comparison of particle size and zeta potential of dispersions of Examples and Comparative Examples

[0110] CGCs addition amount% Median particle size (mm) Zeta voltage (mV) 0% 8121±100 -8.59±0.11 1% 5282±120 -12.76±1.12 2% 4620±124 -22.34±0.76 3% 5175±143 -21.76±0.66

[0111] like Figure 3 As shown in a, by comparing the median particle size of the dispersion, it can be seen that the graphene dispersion

[0112] (Comparative Example 5) Due to its high specific surface area, strong van der Waals forces, and inherent hydrophobicity, it is difficult to disperse in water, resulting in severe agglomeration problems, resulting in a relatively large particle size of 8121 nm. As the amount of CGCs added increases, the median particle size of graphene gradually decreases, reaching a minimum of 4620 nm. However, after the CGCs addition exceeds 2%, the median particle size begins to increase again.

[0113] like Figure 3As shown in Figure 2b, a comparison of the zeta potentials of the dispersions reveals that the graphene dispersion (Comparative Example 5) has a potential of -8.59 mV, indicating that the graphene in the dispersion is negatively charged. With the addition of CGCs, the potential of the dispersion further decreases, indicating that the presence of CGCs stabilizes the graphene dispersion in the solution. When the CGCs addition level is 2%, the potential of the mixture reaches -22.34 mV, indicating a larger absolute value of the potential. Combining the two dispersion analysis methods, the graphene dispersion is optimal when the CGCs addition level is 2% (Example 2.2).

[0114] Under the condition of adding CGC at the optimal concentration, that is, the addition amount of CGCs is 2% (Example 2.2): the median particle size of the graphene dispersion is reduced by 43.11%, and the absolute value of the Zeta potential is increased by 160.07%. The dispersibility of the graphene dispersion is greatly improved after adding CGC, which is conducive to the formation of an efficient graphene conductive network, thereby improving the conductive properties of the CGC-graphene film. The CGC-graphene film prepared by the present invention has good conductive properties and excellent mechanical properties. Compared with the single graphene film without adding CGC, under the optimal film preparation process conditions: the tensile strength is increased by 62.21%, and its value reaches 136.34 MPa (as shown in the attached figure). Figure 5 The conductivity reached 213.34 s / m, which is increased by 57.35 times (see attached Figure 6 shown).

[0115] The corresponding table is as follows:

[0116] Table 5 Comparison of tensile strength and elongation at break between examples and comparative examples

[0117] Tensile strength MPa Elongation at break % Comparative Example 4 59.34±1.56 43.55±0.45 Comparative Example 5 84.05±5.91 21.24±0.44 Example 2.2 136.34±4.94 12.06±0.65

[0118] The following table is with Figure 6 Corresponding conductivity data:

[0119] Table 6 Comparison of conductivity between examples and comparative examples

[0120] Comparative Example 4 Comparative Example 5 Example 2.1 Example 2.2 Example 2.3 Electrical conductivity (S / m) 0 3.72 ±2.78 74.07±5.23 213.34±4.21 207.25±5.32

[0121] As can be seen from Tables 5 and 6, Example 2.2 exhibits the highest tensile strength, the lowest elongation at break, and the highest electrical conductivity. Comparative Example 4, on the other hand, exhibits the lowest tensile strength, the highest elongation at break, and very low electrical conductivity. This demonstrates that the edible mycorrhizal glycoconjugate nanofiber solution and graphene work together to impart excellent tensile strength and electrical conductivity to the final film. This also demonstrates that graphene significantly enhances the electrical conductivity of the final product.

[0122] Test Example 5

[0123] The microstructures of the films prepared in Example 2.2, Comparative Examples 4 and 5 were observed using a scanning electron microscope. Figure 4 shown.

[0124] like Figure 4 As shown, the sugar complex film (Comparative Example 4) has a smooth surface and a dense cross section. The graphene film (Comparative Example 5) has a relatively flat surface and a relatively dense thick lamellar stacking structure in cross section. Compared with the two, the sugar complex-graphene composite film (Example 2.2) has wrinkles on the surface but no agglomeration of any particles; the cross section of the sugar complex-graphene composite film is a dense lamellar stacking structure, and the thin flake shape of graphene indicates that the van der Waals force between graphenes is weakened; this shows that the addition of sugar complexes helps to improve the dispersibility of the graphene solution. The good dispersibility of the graphene solution is conducive to the formation of a continuous and efficient conductive network inside the film, and the thin flake graphene is conducive to the formation of a continuous and efficient conductive network inside the film.

[0125] Graphene weakens the scattering effect of carriers, reduces the sheet resistance of the film, and thus enhances the conductivity of the film; this dense layered structure can improve the interfacial bonding force between the sugar complex and graphene, thereby enhancing the mechanical properties of the film.

[0126] Test Example 6

[0127] Comparing the mechanical properties of Example 2.2 with Comparative Examples 4 and 5, the results are as follows: Figure 5 shown.

[0128] like Figure 5 As shown, the glycoconjugate film without graphene (Comparative Example 4) exhibited the lowest tensile strength, at 59.21 MPa. The addition of graphene significantly increased the tensile strength of the composite film, while significantly decreasing its elongation at break. The tensile strength of the glycoconjugate-graphene composite film (Example 2.2) was greater than that of the glycoconjugate film (Comparative Example 4) and the graphene film (Comparative Example 5), further demonstrating that the co-modification of graphene and glycoconjugates significantly broadens the application prospects of composite films.

[0129] Test Example 7

[0130] Comparing the conductivity of Example 2.2 with Comparative Examples 4 and 5, the results are as follows: Figure 6 shown.

[0131] like Figure 6As shown, the conductivity of the glycoconjugate film (Comparative Example 4) was 0, while the conductivity of the glycoconjugate-graphene composite films with different ratios was greater than 0. When the glycoconjugate addition level was low, the conductivity of the glycoconjugate-graphene film was poor, but as the glycoconjugate addition level increased, the conductivity of the composite film increased. When the glycoconjugate addition level was 2% (Example 2.2), the conductivity of the composite film reached a maximum of 213.34 s / m, and as the glycoconjugate addition level continued to increase, the conductivity stabilized. In summary, the conductivity of the glycoconjugate-graphene composite film prepared by the present invention was higher than the conductivity of the polyaniline-hydroiodic acid-reduced graphene film (61 s / m) and the conductivity of the nanocrystalline cellulose / graphene composite film (176 s / m), but lower than the conductivity of the carbon nanotube / graphene composite film (448 s / m).

[0132] This indicates that the sugar complex-graphene film prepared in the present invention has good electrical conductivity.

Claims

1. An edible mycorrhizal sugar complex-graphene conductive film, characterized in that: The conductive film is prepared using edible mycorrhizal sugar complex and graphene as raw materials; The edible mycorrhizal sugar complex is prepared by the following method: S1 edible fungus root pretreatment: Cut the edible fungus roots into segments, place them under saturated steam at 0.7-1.5 MPa for 5-7 minutes, then release the pressure and use high-speed steam to entrain the material and quickly eject it, and collect the ejected material. S2 Preparation of edible mycorrhizal sugar complex: S21 alcohol treatment: drying the material obtained in S1, crushing it, adding ethanol solution, leaching it, filtering it, and collecting the residue; S22 water treatment: drying the filter residue in S21, crushing it, adding water for extraction, filtering it, and collecting the filter residue; S23 deproteinization: Take the filter residue from S22, add alkali solution to treat, centrifuge, wash the precipitate with water until neutral, and then wash with buffer to obtain alkali-insoluble precipitate; S24 Demineralization: Take the alkali-insoluble precipitate in S23, add acid to treat, centrifuge, and wash the precipitate with water until it is neutral; then add alkali solution to treat, centrifuge, wash the precipitate with water until it is neutral, wash it with buffer, and centrifuge to obtain a precipitate; S25 dialysis: taking the precipitate obtained in S24, dialyzing it with a dialysis membrane, and drying it to obtain the edible mycorrhizal sugar complex.

2. The edible mycorrhizal sugar complex-graphene conductive film according to claim 1, characterized in that: In S1, the edible fungi were cut into 3-5 cm segments, placed in 0.7-1.5 MPa saturated steam for 5-7 min, and then depressurized within 1 s. In S21, a 95% ethanol solution was added at a solid-liquid ratio of 0.9-1.1:14-16 g / L, and ultrasonic extraction was performed at 28-32 °C for 25-35 min. In S22, distilled water was added at a solid-liquid ratio of 0.9-1.1:14-16 g / L, and the mixture was extracted at 80-90 °C for 1.8-2.2 h. In S23, 0.9-1.1 M NaOH solution is added at a solid-liquid ratio of 0.8-1.2:18-22 g / L, and the mixture is treated at 70-80°C for 2-3 h. The mixture is centrifuged, and the precipitate after centrifugation is washed with water until neutral, and then washed with PBS buffer at pH 7.4 to obtain an alkali-insoluble precipitate. In S24, the alkali-insoluble precipitate in S23 is taken, and a 0.9-1.1% HCl solution is added at a weight-to-volume ratio of 1 g to 20 L, and the mixture is treated at 60°C for 1.8-2.2 h, centrifuged, and the precipitate after centrifugation is washed with water until neutral; a 0.9-1.1 M NaOH solution is added at a solid-to-liquid ratio of 0.8-1.2 g / L to 18-22 g / L, and the mixture is treated at 70-80°C for 2-3 h, centrifuged, and the precipitate after centrifugation is washed with water until neutral, then washed with phosphate buffer, and centrifuged to obtain a precipitate; In S25, the precipitate finally obtained in S24 is dialyzed with flowing water for 46 to 50 hours using a dialysis membrane with a molecular weight cutoff of 1000 Da. The liquid in the dialysis bag is freeze-dried to obtain an edible mycorrhizal saccharide complex.

3. The edible mycorrhizal sugar complex-graphene conductive film according to claim 1, characterized in that: In S1, the edible fungi were cut into 3-5 cm segments, placed in 0.7-1.5 MPa saturated steam for 5-7 min, and then depressurized within 1 s. In S21, a 95% ethanol solution was added at a weight-to-volume ratio of 1 g solid to 15 L, and ultrasonic extraction was performed at 30 °C for 30 min. In S22, distilled water was added according to the weight-volume ratio of solid to liquid of 1 g:15 L, and the mixture was heated at 85 °C. Extraction for 2 h; In S23, 1 M NaOH solution was added at a weight-to-volume ratio of 1 g solid to 20 L, and the mixture was treated at 75 °C for 2.5 h. The mixture was centrifuged, and the precipitate after centrifugation was washed with water until neutral, and then washed with PBS buffer at pH 7.4 to obtain an alkali-insoluble precipitate. In S24, the alkali-insoluble precipitate in S23 was taken, and a 1% HCl solution was added at a weight-to-volume ratio of 1 g:20 L to the solid-liquid ratio, and the mixture was treated at 60°C for 2 h. The mixture was centrifuged, and the precipitate after centrifugation was washed with water until neutral. A 1 M NaOH solution was added at a weight-to-volume ratio of 1 g:20 L to the solid-liquid ratio, and the mixture was treated at 75°C for 2.5 h. The mixture was centrifuged, and the precipitate after centrifugation was washed with water until neutral. The precipitate was then washed with phosphate buffer and centrifuged to obtain a precipitate. In S25, the precipitate finally obtained in S24 was dialyzed with flowing water for 48 h using a dialysis membrane with a molecular weight cutoff of 1000 Da. The liquid in the dialysis bag was freeze-dried to obtain an edible mycorrhizal saccharide complex.

4. The method for preparing the edible mycorrhizal sugar complex-graphene conductive film according to claim 1, comprising the following steps: (1) dissolving the edible mycorrhizal saccharide complex prepared in claim 1 in an acetic acid solution and homogenizing to obtain an edible mycorrhizal saccharide complex nanofiber solution; (2) adding graphene to the edible mycorrhizal glycocomplex nanofiber solution in (1), performing mechanical stirring and ultrasonic treatment once, and obtaining a uniformly dispersed edible mycorrhizal glycocomplex-graphene dispersion; (3) Adding gelatin and glycerol to the edible mycorrhizal glycocomplex-graphene dispersion, performing secondary mechanical stirring to obtain a mixed solution, then pouring the mixed solution onto a substrate, heating it to dry and shape it, and obtaining an edible mycorrhizal glycocomplex-graphene film.

5. The method for preparing the edible fungus root sugar complex-graphene conductive film according to claim 4, wherein: In (1), the mass concentration of the edible mycorrhizal sugar complex nanofiber solution is 1~3%; the mass concentration of the acetic acid solution is 2%; and the homogenization condition is: dispersion at a speed of 10000 r / min for 3 min.

6. The method for preparing the edible fungus root sugar complex-graphene conductive film according to claim 4, characterized in that: (2), the mass volume ratio of graphene and edible mycorrhizal sugar complex nanofiber solution is: 5 mg: 1 mL.

7. The method for preparing the edible mycorrhizal sugar complex-graphene conductive film according to claim 4, wherein: (2), the speed of mechanical stirring is 5000 r / min; The incubation time was 80 min, during which ultrasonic treatment was performed for 1 h.

8. The method for preparing the edible mycorrhizal sugar complex-graphene conductive film according to claim 4, wherein: (3), based on the weight percentage, the amount of gelatin added is 0.5-2% of the edible mycorrhizal glycocomplex-graphene dispersion, and the amount of glycerol added is 0.25-1% of the edible mycorrhizal glycocomplex-graphene dispersion.

9. The method for preparing the edible fungus root sugar complex-graphene conductive film according to claim 4, wherein: (3), the secondary mechanical stirring speed is 5000 r / min and the time is 30 min.

Images