CN110283345B - Starch silver nanowire flexible composite electrode material and preparation method thereof - Google Patents

Abstract

The invention discloses a starch silver nanowire flexible composite electrode material and a preparation method thereof; the method comprises the following steps: (1) preparing cross-linked starch; (2) preparing graft copolymerization starch; (3) preparing a flexible modified starch film; (4) and (3) preparing the composite electrode material. The method comprises the steps of preparing grafted spindle starch from potato starch serving as a raw material through high crosslinking, graft copolymerization and saponification hydrolysis, preparing a starch film, and bonding the starch film with silver nanowires by a wire bar coating methodAnd preparing the composite electrode. The product of saponifying the polar group-containing graft copolymer starch has super water absorbability, can absorb several hundred to several thousand times of its own weight of deionized water, and is resistant to certain ions such as Cu²⁺,Cr²⁺,Pb²⁺Has adsorption effect. The silver nanowires have high conductivity and antibacterial property, can simultaneously exert the electrochemical disinfection performance and the antibacterial capability of the silver nanowires, and can be used for preparing the degradable electrode material by compounding the silver nanowires and the electrochemical disinfection performance, the ion adsorption and the sensor, so that the degradable electrode material can be widely applied to the fields of electrochemical disinfection, ion adsorption, sensors and the like.

Description

Starch silver nanowire flexible composite electrode material and preparation method thereof

Technical Field

The invention belongs to the technical field of preparation of composite electrode materials, and particularly relates to a starch silver nanowire flexible composite electrode material and a preparation method thereof.

Background

In the 21 st century, human beings have faced great challenges in energy crisis and environmental protection, and people have looked to the development of green energy and the invention of novel renewable materials. In the past, cellulose, starch, chitosan and the like are used as raw materials, and are combined with conductive materials such as graphene, silver nanowires, polyaniline and the like to prepare a composite conductive material which is applied to solar cells, electrodes, flexible transparent conductive films, sensors and the like.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a starch silver nanowire flexible composite electrode material and a preparation method thereof. The invention takes starch as raw material to modify the starch, prepares grafting shuttle base starch through high crosslinking, graft copolymerization and saponification hydrolysis, prepares modified starch into starch film, then combines with conductive material silver nano wire to prepare composite electrode material, combines the strong water absorption of grafting shuttle base starch, the strong adsorption performance to metal ions and the antibacterial conductive function of silver nano wire, and can be applied to the fields of electrochemistry, sensors, water treatment and the like.

The invention is realized by the following technical scheme:

a preparation method of a starch silver nanowire flexible composite electrode material comprises the following steps:

the method comprises the following steps: preparation of crosslinked starch

Preparing a starch milk solution, preheating, adjusting the pH value, adding a mixed solution of acetic anhydride and citric acid, carrying out water bath reaction, filtering, washing and drying;

step two: preparation of graft-copolymerized starch

Preparing crosslinked starch emulsion, introducing nitrogen to expel oxygen, adding ammonium ceric nitrate and acrylonitrile, reacting, saponifying and hydrolyzing, and adjusting pH value;

step three: preparation of modified starch film

Adding glycerol into the starch milk solution obtained in the step two, stirring and centrifuging, pouring the mixture into a culture dish for film forming by a tape casting method, and drying for later use;

step four: preparation of composite electrode material

Dissolving silver nanowires in isopropanol solution, soaking a starch film in deionized water for demoulding, uniformly coating the silver nanowires on the starch film by using a coating wire rod, drying at room temperature, and cutting.

In the first step: the relation between the addition amount of the mixed solution of acetic anhydride and citric acid and the quality of starch is 0.04-0.06 mL/g, and the ratio of citric acid to acetic anhydride is 1: 30-1: 40.

In the second step: the mass relation between the ammonium ceric nitrate and the starch is 1 to 3 percent.

In the second step: the saponification hydrolysis is to use 5% -10% sodium hydroxide to react at 75-80 ℃ until the color is changed from reddish brown to light yellow.

In the second step: adding acrylonitrile and starch with the mass relation of 0.5-1 mL/g, wherein the reaction condition is that the mixture is stirred for 45-60 minutes at the temperature of 40-60 ℃; the concentration of the starch milk solution is 4-6%.

In the third step: the relationship between the glycerol addition amount and the starch solution amount is 10 to 20 percent.

In the first step: the concentration of the starch milk solution is 30-40%; the preheating time is 5-10 min, the preheating temperature is 50-60 ℃, and the pH value is adjusted to 9-12 (the final pH adjustment is preferably 6.5-8);

the temperature of the water bath reaction is 50-60 ℃, and the time of the water bath reaction is 100-120 min;

the washing is carried out by alternately washing with acetone and water, and the drying is carried out by a (10HS type) electrothermal constant-temperature drying oven at 40 ℃.

The third step is as follows: the amount of the starch emulsion solution prepared by the starch film is 20-30 ml; the centrifugation time is 5-8min, and the rotating speed is 3000-5000 r/min; the drying is a (10HS type) electric heating constant temperature drying oven, and the drying is carried out for 12 to 14 hours at the temperature of 30 to 50 ℃.

The fourth step is as follows: during coating, the silver nanowires are dissolved in isopropanol, and the concentration is adjusted to 10 mg/mL; the room-temperature drying is natural drying for 12-16 h; the line width of the coating wire rod is 50 mu m; the number of the coating layers is 1-5; the cutting area is 1-3 cm²Is square.

The preparation method can obtain the starch silver nanowire flexible composite electrode material.

The invention is based on the following principle: the method is characterized in that starch is used as a raw material, grafted spindle starch is prepared through high crosslinking, graft copolymerization and saponification hydrolysis, and then the starch is prepared into a starch film to be combined with silver nanowires. Through cross-linking graft copolymerization, more abundant active groups are introduced into a starch molecular chain to form a high-efficiency water absorbent and adsorbent, besides, cross-linking starch molecules are formed by closely stacking spherical molecules and present the structural characteristics of a crystalline high polymer, grafted carboxyl starch is a typical amorphous structure, and grafted molecular chains are bonded on three-dimensional high cross-linking starch to form a loose and coral-shaped random microporous structure, so that the microporous structure increases the specific surface area, the adsorption sites of the grafted carboxyl starch molecules on ions are not only on the surfaces of the grafted carboxyl starch molecules, but also can be diffused to any possible-COONa sites, and the adsorption capacity is remarkably increased.

After the silver nanowires are electrified, the special linear nanometer mechanism of the silver nanowires greatly reduces charge transition, current flows on the wires at low loss and high speed, a large amount of charges are accumulated on the surfaces of the wires, high strength is generated around the silver nanowires, the silver nanowires can penetrate cell membranes, electroporation is caused, and bacteria die. The grafted shuttle-based starch has adsorbability on water and strong adsorbability on certain ions, and the network structure of the grafted shuttle-based starch can be tightly combined with metal ions to prepare a starch film which is combined with conductive material silver nanowires to synthesize a composite electrode material, so that the advantages of the grafted shuttle-based starch and the conductive material silver nanowires are exerted together.

Compared with the prior art, the invention has the following beneficial effects and advantages:

the composite electrode material is formed by combining a graft copolymerization starch film and conductive silver nanowires, has the characteristics of the silver nanowires besides the properties of starch and synthetic macromolecules, is a novel electrode material and has wide application.

The water absorption of the invention. Starch molecules are modified, a large number of polar groups are introduced, the starch molecules are easy to combine with water molecules, can absorb water and swell in water without dissolving, the absorption speed is high, the starch molecules become colorless and transparent gel-like substances after absorbing water, and when the surrounding water content is lower than that of gel, the starch molecules can slowly release water, can be repeatedly used and is often applied to super absorbent resins.

The invention also discloses the adsorption property of the invention. The graft copolymerized starch has ion exchange effect on certain ions such as Cu²⁺，Pb²⁺The metal cations have strong adsorption effect, and the adsorbent is applied to resin exchange, has high adsorption capacity, good removability and strong reproducibility, and is a novel reproducible heavy metal ion adsorption remover with wide application.

The silver nanowire has conductivity, and after the silver nanowire is electrified, on one hand, the electrified surface of the silver nanowire generates high electric field breakdown and inactivates bacteria, on the other hand, chlorine generated in the electrolysis process is dissolved in water, and the strong oxidizing property of free chlorine generates a sterilization effect.

Biodegradability of the invention. The starch is degradable and reproducible, is easy to decompose in natural environment, and greatly reduces the problem of environmental pollution.

The method comprises the following steps: the ratio of the citric acid to the acetic anhydride is 1: 30-1: 40, the more the acetic anhydride is used, the higher the crosslinking degree of the product is, when the ratio of the mixed acid is 1: 30-1: 40, the crosslinking degree is the maximum value, the ratio of the mixed acid is continuously increased, and the crosslinking degree begins to decrease. When the amount of acetic anhydride added is reduced, the formation of mixed anhydride is incomplete. Therefore, the ratio of the mixed acid (citric acid: acetic anhydride) is 1:30 to 1: 40. The relation between the addition amount of the mixed solution of the acetic anhydride and the citric acid and the quality of the starch is 0.04-0.06 mL/g, and the more the addition amount of the mixed acid is, the larger the crosslinking degree is. When the addition amount of the mixed acid reaches 0.04-0.06 mL/g, the crosslinking degree value is the maximum. However, when the amount of the mixed acid added was increased after exceeding 0.06mL/g, the degree of crosslinking began to decrease. Therefore, the relation between the optimal mixed acid addition amount and the dry weight of the starch is 0.04-0.06 mL/g.

The method comprises the following steps: the preheating time is 5-10 min, the preheating temperature is 50-60 ℃, the preheating temperature is lower than 50 ℃ or the time is less than 5min, the activation energy required by the reaction cannot be reached, and the reaction is incomplete; when the preheating temperature is higher than 60 ℃ or the time exceeds 10min, the initiator is easy to aggregate, and the diffusion of the monomer to the reaction point on the starch chain is hindered, so that the grafting rate is reduced.

In the second step of the invention: the mass relation between ammonium ceric nitrate and starch is 1-3%, because the grafting rate is increased and then decreased with the increase of the concentration of ammonium ceric nitrate as an initiator. The concentration of ammonium cerium nitrate is increased, the number of free radicals on a starch chain is increased, the grafting reaction is accelerated, the homopolymerization reaction is slowed down, and the grafting rate is increased; when the mass relationship between the initiator ammonium cerium nitrate and the starch is more than 3%, the excessive initiator is aggregated to prevent the monomer from diffusing to the reaction points on the starch chain, so that the grafting rate is reduced.

In the second step of the invention: the reaction conditions are at 40 ℃ to 60 ℃ because at low temperatures, polymerization does not occur; with increasing reaction temperature, the grafting rate increases first and then decreases. The temperature rise increases the diffusion of the monomer to the molecular chain of the starch, and the swelling of the starch is promoted; the fluidity of the monomer and the collision probability of the starch macromolecules are increased, and when the temperature is higher than 60 ℃, the homopolymerization rate is accelerated, the chain is prevented from transferring to the monomer, and the grafting rate is reduced.

In the second step of the invention: the mass relation between the added acrylonitrile and the starch is 0.5-1 mL/g, because the grafting efficiency and the grafting rate are increased and then reduced along with the increase of the concentration of the acrylonitrile monomer. The increased grafting rate may be due to an increased probability of monomer around the starch and thus increased probability of collisions between reactants. However, with a monomer concentration higher than 1mL/g, homopolymerization is superior to grafting, and grafting efficiency is decreased. The alkyl group length of the monomer is increased, a steric hindrance effect is generated, and the grafting rate is reduced.

The invention comprises the following steps: the relationship between the amount of the added glycerol and the amount of the starch solution is 10-20 percent, because the starch film is not flexible enough and is easy to crack when too little starch is added, and the function of the graft is influenced when the added glycerol is too much.

The invention comprises the following steps: the amount of the starch milk solution for preparing the starch film is 20-30 ml, because too little amount of the starch milk solution can cause the film thickness to be too thin and the mechanical property to be poor, the subsequent treatment is influenced, and too much amount of the starch milk solution can cause the electrode thickness to be too large and the flexibility of the electrode is influenced. The centrifugation time is 5-8min, and the rotating speed is 3000-5000 r/min, because too low or too short centrifugation rotating speed easily causes the air bubbles to be removed unclean, thus resulting in uneven film, and too long or too high rotating speed can cause uneven deposition of starch solution, uneven film formation and being not beneficial to the combination of the film and the conductive material.

The invention comprises the following steps: the drying is carried out naturally for 12-16 h at room temperature, because the drying speed of an oven is too high, the film is easy to deform, the surface is easy to wrinkle, and the subsequent treatment is not facilitated.

Drawings

FIG. 1 is an AFM image of the surface of the composite electrode material prepared in example 1.

FIG. 2 is an AFM image of the surface of the composite electrode material prepared in example 2.

FIG. 3 is an AFM image of the surface of the composite electrode material prepared in example 3.

Fig. 4 is a graph showing changes in conductivity (sheet resistance) of the composite electrode materials prepared in examples 1 to 3.

Fig. 5 is a graph of the electrical conductivity (sheet resistance) versus time (stability) of the composite electrode materials prepared in examples 1-3.

FIG. 6 is a graph showing the relationship between the water absorption capacity of the electrode and the water absorption time.

FIG. 7 is a graph showing the relationship between the metal ion adsorption performance of an electrode pair and the mass of the electrode.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

Example 1

The first step is as follows: weighing 6g of potato starch in a triangular flask by using an electronic balance, adding 20mL of distilled water to prepare 30% starch emulsion, uniformly stirring, preheating at 50 ℃ in a water bath kettle for 10min, measuring the pH by using test paper, adjusting the pH to 9, slowly adding 0.36mL of mixed solution of 0.01mL of citric acid and 0.35mL of acetic anhydride, carrying out water bath at 55 ℃, keeping the pH constant in the reaction process, and reacting for 100 min. And after the reaction is finished, adjusting the pH value of the solution to 7, performing suction filtration, washing, drying and crushing to obtain a finished product.

The second step is that: adding 50mL of deionized water into 3g of the crosslinked starch obtained in the previous step, uniformly stirring, introducing nitrogen for about half an hour to remove oxygen, adding 0.03g of ammonium cerium nitrate, uniformly stirring, adding 3mL of acrylonitrile, stirring for 55 minutes at about 40 ℃, performing saponification hydrolysis by using 5% sodium hydroxide, controlling the system temperature to 85 ℃, reacting until the system color is changed from reddish brown to light yellow, cooling, and adjusting the pH to be slightly acidic by using 2% hydrochloric acid.

The third step: and (3) adding 3mL of glycerol into 30mL of the starch solution, uniformly stirring, centrifuging at 5000r/min for 5min, placing in a culture dish, forming a film by a tape casting method, drying in an oven at 30 ℃ for 13h, and soaking in distilled water to take out the starch film.

The fourth step: uniformly dispersing silver nanowires in isopropanol to prepare a silver nanowire solution of 10mg/mL, uniformly coating the silver nanowire solution on a starch film by using a coating wire rod (the line width is 50 micrometers), wherein the thickness of the silver nanowire solution is 1 layer, naturally drying a composite electrode material at room temperature for 16 hours after a solvent is naturally volatilized at room temperature, finally obtaining an electrode material with a uniform surface, cutting the electrode material into a rectangle of 1X3cm, and the area of the electrode is 3cm²。

Example 2

The first step is as follows: weighing 6g of potato starch in a triangular flask by using an electronic balance, adding 15mL of distilled water to prepare 40% starch emulsion, uniformly stirring, preheating at 55 ℃ for 7min in a water bath kettle, measuring the pH by using test paper, adjusting the pH to 12, slowly adding 0.31mL of starch by mass, namely a mixed solution of 0.01mL of citric acid and 0.3mL of acetic anhydride, carrying out water bath at 60 ℃, keeping the pH constant in the reaction process, and reacting for 110 min. And after the reaction is finished, adjusting the pH value of the solution to 8, performing suction filtration, washing, drying and crushing to obtain a finished product.

The second step is that: adding 50mL of deionized water into 2g of the crosslinked starch obtained in the previous step, uniformly stirring, introducing nitrogen for about half an hour to remove oxygen, adding 0.04g of ammonium ceric nitrate, uniformly stirring, adding 1.5mL of acrylonitrile, stirring for 45 minutes at about 60 ℃, performing saponification hydrolysis by using 10% sodium hydroxide, controlling the temperature of a system to be 75 ℃, reacting until the color of the system is changed from reddish brown to light yellow, cooling, and adjusting the pH value to be slightly acidic by using 2% hydrochloric acid.

The third step: taking 25ml of the starch solution, adding 4ml of glycerol, uniformly stirring, centrifuging at 4000r/min for 6min, placing in a culture dish, forming a film by a tape casting method, drying in an oven at 50 ℃ for 12h, soaking in distilled water, and taking out the starch film.

The fourth step: uniformly dispersing silver nanowires in isopropanol to prepare a 10mg/mL silver nanowire solution, uniformly coating the solution on a starch film by using a coating wire rod (the line width is 50 micrometers), wherein the thickness of the solution is 3 layers, naturally drying the composite electrode material at room temperature for 12 hours after the solvent is naturally volatilized at room temperature, finally obtaining an electrode material with a uniform surface, cutting the electrode material into a rectangle of 1X1cm, and the area of the electrode is 1cm²。

Example 3

The first step is as follows: weighing 7g of potato starch in an electronic balance, adding 20mL of distilled water to prepare 35% starch emulsion, uniformly stirring, draining water, preheating for 5min at 60 ℃ in a bath kettle, measuring the pH value by using test paper, adjusting the pH value to 10, slowly adding 0.28mL of starch by mass, mixing a solution of citric acid and acetic anhydride with the proportion of 0.007mL, carrying out water bath at 50 ℃, keeping the pH value constant in the reaction process, and reacting for 120 min. And after the reaction is finished, adjusting the pH value of the solution to 6.5, performing suction filtration, washing, drying and crushing to obtain a finished product.

The second step is that: adding 50mL of deionized water into 2.5g of the crosslinked starch obtained in the previous step, uniformly stirring, introducing nitrogen for about half an hour to remove oxygen, adding 0.075g of aqueous solution of ammonium ceric nitrate, uniformly stirring, adding 1.25mL of acrylonitrile, stirring for 60 minutes at about 50 ℃, performing saponification hydrolysis by using 7% of sodium hydroxide, controlling the temperature of the system to 80 ℃, reacting until the color of the system is changed from reddish brown to light yellow, cooling, and adjusting the pH to be slightly acidic by using 2% hydrochloric acid.

The third step: and (3) taking 20ml of the starch solution, adding 2ml of glycerol, uniformly stirring, centrifuging at 3000r/min for 8min, placing in a culture dish, forming a film by a tape casting method, drying in an oven at 40 ℃ for 14h, and soaking in distilled water to take out the starch film.

The fourth step: uniformly dispersing silver nanowires in isopropanol to prepare a 10mg/mL silver nanowire solution, uniformly coating the solution on a starch film by using a coating wire rod (the line width is 50 micrometers), wherein the thickness of the solution is 5 layers, naturally drying a composite electrode material at room temperature for 14 hours after a solvent is naturally volatilized at room temperature, finally obtaining an electrode material with a uniform surface, cutting the electrode material into a rectangle of 1X2cm, and the area of the electrode is 2cm²。

As described above, the present invention can be preferably realized.

According to the invention, potato starch is used as a raw material, the grafting spindle base starch is prepared through high crosslinking, graft copolymerization and saponification hydrolysis, then the starch film is prepared, and the wire rod coating method is combined with the silver nanowire to prepare the composite electrode. The product of saponifying the polar group-containing graft copolymer starch has super water absorbability, can absorb several hundred to several thousand times of its own weight of deionized water, and is resistant to certain ions such as Cu²⁺,Cr²⁺,Pb²⁺Has adsorption effect. The silver nanowires have high conductivity and antibacterial property, can simultaneously exert the electrochemical disinfection performance and the antibacterial capability of the silver nanowires, and can be used for preparing the degradable electrode material by compounding the silver nanowires and the electrochemical disinfection performance, the ion adsorption and the sensor, so that the degradable electrode material can be widely applied to the fields of electrochemical disinfection, ion adsorption, sensors and the like.

The embodiments of the present invention are not limited to the above-described embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and they are included in the scope of the present invention.

Claims (3)

1. A preparation method of a starch silver nanowire flexible composite electrode material is characterized by comprising the following steps:

the method comprises the following steps: preparation of crosslinked starch

Preparing a starch milk solution, preheating, adjusting the pH value, adding a mixed solution of acetic anhydride and citric acid, carrying out water bath reaction, filtering, washing and drying;

the relation between the addition amount of the mixed solution of acetic anhydride and citric acid and the quality of starch is 0.04-0.06 mL/g, and the ratio of citric acid to acetic anhydride is 1: 30-1: 40;

step two: preparation of graft-copolymerized starch

Preparing crosslinked starch emulsion, introducing nitrogen to expel oxygen, adding ammonium ceric nitrate and acrylonitrile, reacting, saponifying and hydrolyzing, and adjusting pH value;

the mass relation of ammonium ceric nitrate and starch is 1-3%;

the saponification hydrolysis is that 5 to 10 percent of sodium hydroxide is used for reacting at the temperature of between 75 and 80 ℃ until the color is changed from reddish brown to faint yellow;

adding acrylonitrile and starch with the mass relation of 0.5-1 mL/g, wherein the reaction condition is that the mixture is stirred for 45-60 minutes at the temperature of 40-60 ℃; the concentration of the starch milk solution is 4-6%;

step three: preparation of modified starch film

Adding glycerol into the starch milk solution obtained in the step two, stirring and centrifuging, pouring the mixture into a culture dish for film forming by a tape casting method, and drying for later use;

the relationship between the glycerol adding amount and the starch solution amount is 10 to 20 percent;

the amount of the starch emulsion solution prepared by the starch film is 20-30 ml; the centrifugation time is 5-8min, and the rotating speed is 3000-5000 r/min; drying is carried out in an electric heating constant-temperature drying oven at the temperature of 30-50 ℃ for 12-14 h;

step four: preparation of composite electrode material

Dissolving silver nanowires in isopropanol solution, soaking a starch film in deionized water for demoulding, uniformly coating the silver nanowires on the starch film by using a coating wire rod, drying at room temperature, and cutting;

during coating, the silver nanowires are dissolved in isopropanol, and the concentration is adjusted to 10 mg/mL; the room-temperature drying is natural drying for 12-16 h; the line width of the coating wire rod is 50 mu m; the number of the coating layers is 1-5; the cutting area is 1-3 cm²Is square.

2. The preparation method of the starch silver nanowire flexible composite electrode material as claimed in claim 1, characterized in that in the step one: the concentration of the starch milk solution is 30-40%; the preheating time is 5-10 min, the preheating temperature is 50-60 ℃, and the pH value is adjusted to 9-12;

the temperature of the water bath reaction is 50-60 ℃, and the time of the water bath reaction is 100-120 min;

the washing is performed by alternately washing with acetone and water, and the drying is performed by drying at 40 ℃ in an electrothermal constant-temperature drying oven.

3. The starch silver nanowire flexible composite electrode material obtained by the preparation method of claim 2.

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