JP2014240538A - Method for manufacturing composite of metal nanoparticles and cellulose-based fiber - Google Patents

Abstract

An object of the present invention is to provide a low-cost and environmentally friendly method for supporting metal nanoparticles on the surface of a cellulose fiber. A cellulosic fiber having an aldehyde group on the surface is brought into contact with an aqueous metal compound solution, and the metal compound is reduced by the aldehyde group to form metal nanoparticles on the fiber surface. Since the metal compound can be reduced by the aldehyde group present on the surface of the cellulosic fiber, the amount of the reducing agent solution used can be greatly reduced when supporting the metal nanoparticles on the fiber surface, or the reducing agent solution. May not be used. [Selection] Figure 2

Description

  The present invention relates to a method for producing a composite of metal nanoparticles and cellulosic fibers.

  Metal nanoparticles are expected to be applied as highly functional catalysts in material production processes that are in harmony with the environment. However, since metal nanoparticles are difficult to handle, a material capable of holding metal nanoparticles is indispensable for a practical catalyst or the like. Conventionally, studies have been made to hold metal nanoparticles with a polymer material. For example, a method of kneading metal nanoparticles and a polymer material is known. However, the composite obtained in this manner contains metal nanoparticles inside the polymer material, and the metal nanoparticles contained therein cannot participate in the catalytic reaction, so that the catalytic activity is sufficient. There was a problem of not.

  For this reason, a method for supporting metal nanoparticles on the surface of cellulose nanofibers has been developed (Patent Document 1). Specifically, a method of reducing metal ions bonded to carboxyl groups of nanofibers to metal nanoparticles by a gas phase reduction method using hydrogen and a liquid phase reduction method using a reducing agent such as a sodium borohydride aqueous solution. Is disclosed.

International Publication No. 2010/095574

  However, the method for producing a composite in which metal nanoparticles are supported on cellulose nanofibers described in Patent Document 1 uses a reducing agent solution to support metal nanoparticles on cellulose nanofibers. The problem is that the load is large and the cost is industrially high.

It is an object of the present invention to provide a method with a low environmental load for supporting metal nanoparticles on the surface of a cellulosic fiber. Ie:
1. Step 1 of preparing a cellulosic fiber having an aldehyde group on the surface, and contacting the cellulosic fiber with an aqueous metal compound solution to reduce the metal compound with an aldehyde group on the surface of the cellulosic fiber; Step 2 of forming metal nanoparticles on the surface
The manufacturing method of the composite_body | complex of a metal nanoparticle and a cellulose fiber containing this.
2. The metal nanoparticles may include carboxyl groups or carboxylate groups generated by oxidation of the aldehyde groups, carboxyl groups or carboxylate groups further included on the surface of the cellulose fiber in the step 1, or both of them. 2. The production method according to 1 above, which is bonded.
3. The said metal nanoparticle is a manufacturing method of said 1 or 2 containing the element which belongs to 8-12 group in a periodic table.
4). The average particle diameter calculated | required from the transmission electron microscope image of the said metal nanoparticle is a manufacturing method of any one of said 1-3 which is 1-50 nm.
5. The said cellulosic fiber is a manufacturing method of any one of said 1-4 which is a pulp.
6). The said cellulosic fiber is a manufacturing method of any one of said 1-4 which is a cellulose nanofiber.
7). 7. The production method according to 6 above, wherein the cellulose nanofiber is crystalline.
8). The average fiber diameter calculated | required from the transmission electron microscope image of the said cellulose nanofiber is a manufacturing method of said 6 or 7 which is 2.5-20 nm.
9. The said cellulose fiber is a manufacturing method of any one of said 1-8 which is a cellulose fiber obtained by oxidizing a cellulose using N-oxyl compound in water.
10. The composite_body | complex manufactured with the manufacturing method of any one of said 1-9.

  According to the production method of the present invention, the metal compound can be reduced by the aldehyde group present on the surface of the cellulosic fiber, so that the amount of the reducing agent solution used is greatly reduced when the metal nanoparticle is supported on the fiber surface. Or a reducing agent solution may not be used.

Photographs of oxidized pulp sheets prepared in Example 1, Comparative Example 1 and Comparative Example 2 SEM image of oxidized pulp sheet prepared in Example 1 and Comparative Example 1 Results of XRD analysis of materials prepared in Example 1 and Comparative Example 1 Results of EDX analysis of the material prepared in Example 1 UV-visible light absorption spectrum in the reduction reaction using the material prepared in Example 1 SEM image of oxidized pulp sheet prepared in Example 2 SEM image of the pulp sheet prepared in Comparative Example 3

  The method for producing a composite according to the present invention comprises (Step 1) a step of preparing a cellulose fiber having an aldehyde group on the surface, and (Step 2) contacting the cellulose fiber with an aqueous metal compound solution to form the cellulose A step of reducing the metal compound by an aldehyde group on the surface of the fiber to form metal nanoparticles on the surface of the cellulosic fiber.

1. Process 1
(1) Cellulose-based fiber Cellulose-based fiber is a fiber (fiber) mainly composed of cellulose, which is a polysaccharide in which glucose is β-1,4-glycosidically bonded, or a derivative thereof. Cellulose fibers include fibers of various cellulose derivatives such as partially methylated cellulose, partially acetylated cellulose, and partially carboxymethylated cellulose in addition to cellulose fibers, and chitin that is similar in structure to cellulose. -Chitosan fiber may be included.

The cellulosic fiber of the present invention has at least an aldehyde group on its surface. Furthermore, you may have a carboxyl group and / or a carboxylate group. Refers to a group represented by -COOH and carboxyl groups, -COO the carboxylate groups ^- refers to a group represented by, it refers to a group represented by -CHO the aldehyde group. The counter ion of the carboxylate group is not particularly limited. As will be described later, when the metal compound forms an ionic bond with the carboxylate group, this metal ion serves as a counter. The carboxyl group and the carboxylate group are collectively referred to as an “acid group”.

The content of acid groups and aldehyde groups in the cellulosic fiber can be measured by the following method:
Using a precisely weighed dry cellulose fiber sample, 60 mL of 0.5-1 mass% slurry is prepared, and the pH is adjusted to about 2.5 with 0.1 mol / L hydrochloric acid aqueous solution. Then, 0.05 mol / L sodium hydroxide aqueous solution is dripped and electrical conductivity measurement is performed. The measurement is continued until the pH is about 11. From the amount of sodium hydroxide consumed (V) until the change in electrical conductivity shows a mild acid neutralization stage, the acid group amount X1 is determined using the following equation:
X1 (mmol / g) = V (mL) × 0.05 / mass of cellulose fiber (g)
The acid group amount X1 represents the total amount of carboxyl groups and carboxylate groups in 1 g of cellulose fiber (that is, the amount of “acid groups”).

  Subsequently, the pH of the sample is adjusted to 4 to 5 with acetic acid, and an oxidation reaction is further performed at room temperature for 48 hours using a 2 mass% aqueous sodium chlorite solution. The acid group amount X2 is obtained in the same manner as described above for the obtained sample. The amount of aldehyde group is determined by the difference between X2 and X1.

  In the present invention, the amount of aldehyde groups is preferably from 0.1 to 1.0 mmol / g, more preferably from 0.2 to 0.6 mmol / g. The amount of the acid group is not particularly limited, but is about 0.2 to 2.2 mmol / g, and preferably 0.2 to 2.0 mmol / g.

  Cellulose fibers preferably have high-density aldehyde groups on the surface. The density of aldehyde groups on the fiber surface can be expressed by the amount of aldehyde groups per unit area. When the aldehyde groups are uniformly dispersed at a high density on the fiber surface, the reduction of the metal compound is promoted. In addition, the aldehyde group itself is oxidized to a carboxyl group by reducing the metal compound, which may become a supporting point for the metal nanoparticles, so that the aldehyde group is uniformly dispersed at high density on the fiber. If so, the formation of high-density and uniform metal nanoparticles is considered to be promoted. If the metal nanoparticles can be highly dispersed on the fiber while maintaining a fine form, it is considered that the activity when used as a catalyst is excellent.

In addition, since the acid groups on the surface of the cellulosic fiber may become a supporting contact point for the metal compound, it is also preferable that the acid groups exist in high density in addition to the aldehyde groups. The density of acid groups on the fiber surface can be represented by the amount of acid groups per unit area, and the amount of acid groups per unit area can be represented by the amount of charge per unit area. Its range is preferably 0.01~0.6C / ^{m 2.} The amount of charge can be determined from the amount of acid groups, surface area, and Faraday constant of the cellulosic fiber. The surface area is determined by a known method such as the BET method.

  The cellulosic fiber is preferably derived from crystalline cellulose. Crystalline cellulose has advantages such as high strength and difficulty in dissolving in a solvent. Cellulosic fibers obtained from natural cellulose as a raw material are crystalline. Examples of natural cellulose include natural cellulose from plants, bacteria, algae, and animals. Of these, natural cellulose derived from plants or animals (particularly from sea squirts) is preferred. The crystal structure is not particularly limited as long as it is a known crystal structure. Examples of known crystal structures include cellulose type Iβ.

  Cellulose fibers having an aldehyde group on the surface may be obtained by a known method. For example, it can be obtained by oxidizing cellulose in water using an oxidizing agent in the presence of a compound selected from the group consisting of N-oxyl compounds and bromides, iodides, or mixtures thereof. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and a cellulose fiber having an aldehyde group and a carboxyl group or a carboxylate group on the surface can be obtained. The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by mass or less.

  The N-oxyl compound refers to a compound that can generate a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction.

  The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can oxidize cellulose as a raw material. For example, 0.01 to 10 mmol is preferable, 0.01 to 1 mmol is more preferable, and 0.05 to 0.5 mmol is more preferable with respect to 1 g of absolutely dry cellulose. Moreover, about 0.1-4 mmol / L with respect to a reaction system is good.

  Bromide is a compound containing bromine, examples of which include alkali metal bromides that can dissociate and ionize in water. Further, an iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used can be selected as long as the oxidation reaction can be promoted. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and still more preferably 0.5 to 5 mmol with respect to 1 g of absolutely dry cellulose.

  As the oxidizing agent, known ones can be used, and for example, halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, peroxide and the like can be used. Of these, sodium hypochlorite is preferable because it is inexpensive and has a low environmental impact. The appropriate amount of the oxidizing agent used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, further preferably 1 to 25 mmol, and most preferably 3 to 10 mmol with respect to 1 g of absolutely dry cellulose. . For example, 1-40 mol is preferable with respect to 1 mol of N-oxyl compounds.

  The cellulose oxidation process allows the reaction to proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40 ° C, and may be room temperature of about 15 to 30 ° C. As the reaction proceeds, a carboxyl group is generated in the cellulose, so that the pH of the reaction solution is reduced. In order to advance the oxidation reaction efficiently, an alkaline solution such as an aqueous sodium hydroxide solution is added to maintain the pH of the reaction solution at about 8 to 12, preferably about 10 to 11. The reaction medium is preferably water because it is easy to handle and hardly causes side reactions.

  The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 to 6 hours, for example, about 0.5 to 4 hours.

  The oxidation reaction may be performed in two stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first-stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt generated as a by-product in the first-stage reaction. Can be oxidized well.

  The amount of the carboxyl group, carboxylate group, and aldehyde group of the cellulose fiber can be adjusted by controlling the amount of the oxidizing agent added and the reaction time.

  The cellulosic fiber thus obtained has aldehyde groups and acid groups on the surface and hardly exists inside. This is presumably because the oxidant hardly diffuses into the fiber.

  The fiber length and fiber width of the cellulosic fiber are not particularly limited, and the fiber length of 0.1 to 10 μm and the fiber diameter of about 1 to 100 nm, preferably 2.5 to It may be about 20 nm (corresponding to cellulose nanofiber), fiber length 0.1 to 10 mm, fiber diameter 1 to 100 μm (corresponding to pulp), or between cellulose nanofiber and pulp Fiber diameter and fiber width.

  The average fiber diameter of the cellulosic fiber is determined from a scanning or transmission electron microscope image (SEM or TEM) or an atomic force microscope image (AFM). It is preferably obtained from a scanning or transmission electron microscope image.

2. Process 2
In step 2, the metal compound aqueous solution is brought into contact with a cellulose fiber having an aldehyde group on the surface, and the metal compound is reduced by the aldehyde group of the cellulose fiber to form metal nanoparticles on the surface of the cellulose fiber.

(1) Contact between Cellulose Fiber and Metal Compound Aqueous Solution Cellulosic fiber and metal compound aqueous solution are contacted to bond the metal compound to the aldehyde group or acid group of the cellulose fiber. Metal compounds are thought to form coordinate bonds and hydrogen bonds with these groups. Moreover, it is thought that the metal ion derived from a metal compound forms an ionic bond with a carboxylate group. At this stage, the metal compound is considered to be bonded to these groups at the atomic level or the molecular level, and thus metal nanoparticles are not formed.

The metal compound aqueous solution is an aqueous solution of a metal salt or an organometallic compound. The metal is preferably an element belonging to Group 8-12 of the periodic table. Examples of metal salts include complexes (complex ions), halides, nitrates, sulfates, and acetates. The metal salt is preferably water-soluble. Moreover, since these salts of precious metals may have low water solubility, it is preferable to use chloroplatinic acid (H ₂ PtC ₁₆ ) or chloroauric acid (HAuCl ₄ ).

  Regarding the contact method, a cellulose fiber dispersion prepared in advance and a metal compound aqueous solution may be mixed. Alternatively, a dispersion containing cellulosic fibers may be applied onto a substrate to form a film, and the metal compound aqueous solution may be dropped and impregnated into the film. At this time, the film may remain fixed on the substrate or may be peeled from the substrate. Moreover, you may make a cellulose fiber made into a sheet form impregnated with an aqueous metal compound solution. At this time, the metal compound aqueous solution can be impregnated with a sheet obtained by mixing the cellulose fiber of the present invention and a known fiber.

  Although the density | concentration of metal compound aqueous solution is not specifically limited, 0.1-10 times mole amount is preferable with respect to the amount of aldehyde groups or acid groups of a cellulose fiber, and 0.5-2 times mole amount is more preferable. For example, an aqueous metal compound solution of about 0.1 to 10 mM can be used.

  You may adjust suitably the time to contact according to a density | concentration and temperature. For example, about 1 minute to 24 hours, for example, about 1 minute to 12 hours, or about 2 to 12 hours, or about 2 to 3 hours. Although the temperature at the time of making it contact is not specifically limited, 20-40 degreeC is preferable. In addition, the pH of the liquid at the time of contact is preferably 2.5 to 13.

(2) Reduction by aldehyde group The metal compound which contacted the cellulose fiber is reduced by the aldehyde group contained in the cellulose fiber. Metal nanoparticles are formed by this reduction reaction. Although this mechanism is not clear, it is guessed as follows. A metal compound or an ion derived from a metal compound that has been bonded to an acid group by an ion exchange reaction or the like is reduced to a metal. At this time, the produced metal is supported on the surface of the cellulosic fiber. Similarly, the generated neighboring metals are integrated with each other, so that the particles grow to form nanoparticles. On the other hand, metal compounds that are present in the vicinity of the cellulosic fiber but not bound to the fiber surface are also reduced to produce a metal. This metal quickly integrates with the metal on the surface of the cellulosic fiber to form metal nanoparticles.

  It can be said that the metal nanoparticles thus formed were synthesized using aldehyde groups or acid groups present on the surface of the cellulosic fiber as a scaffold.

(3) Metal nanoparticle The element which comprises a metal nanoparticle is although it does not specifically limit, It is preferable that it is an element which belongs to 8-12 group in a periodic table. By periodic table is meant the periodic table of the IUPAC inorganic chemical nomenclature revised in 1998. Among these, Ru, Fe, Co, Rh, Ni, Pd, Pt, Cu, Ag, Au, or Zn are preferable. The composite of the present invention includes a large number of metal nanoparticles, but it is not necessary that all the metal nanoparticles are composed of a single element. For example, 50% of the total number of metal nanoparticles may be composed of only one element 1, and the remaining 50% may be composed of only another element 2. Moreover, a part of all metal nanoparticles may be comprised with the alloy of the elements 1 and 2, and the remainder may be comprised from the single element. It is preferable to appropriately prepare a catalyst composed of a single element or a plurality of elements according to the application of the catalyst.

  The average particle diameter of the metal nanoparticles is determined from a scanning or transmission electron microscope image (SEM or TEM), an atomic force microscope image (AFM), or X-ray diffraction. In the present invention, the average particle size of the metal nanoparticles is preferably in the range of 1 to 50 nm when determined from a scanning or transmission electron microscope image. Specifically, for the average particle diameter, a scanning or transmission electron microscope image of the complex of the present invention is prepared, and from the image, the equivalent circle diameter of primary particles of a plurality of metal nanoparticles is obtained, and these values are averaged. Is required. The average particle size affects the catalyst characteristics and the like of the composite of the present invention. Therefore, the suitable range varies depending on the type of metal. For example, when the metal nanoparticles are Pt, the average particle diameter is preferably 1 to 50 nm, but when the metal nanoparticles are Au, the average particle diameter is preferably 1 to 10 nm.

  It is preferable that the metal nanoparticles are uniformly dispersed on the cellulosic fiber surface. This is because it has excellent activity when used as a catalyst. The dispersion state of the metal nanoparticles can be represented by the average particle diameter of the metal nanoparticles and the amount of the metal nanoparticles per unit mass of the cellulose fiber. That is, the dispersion state of the metal nanoparticles can be defined by D = “amount of metal nanoparticles per unit mass of cellulose fiber” / “average particle diameter of metal nanoparticles”. As described above, the average particle diameter of the metal nanoparticles is preferably 1 to 50 nm. On the other hand, the amount of metal nanoparticles per unit mass of cellulose fiber can be expressed by “mol number of metal element in metal nanoparticle” / “mass of cellulose fiber”. The range is preferably 0.001 mmol / g cellulose to 10 mol / g cellulose, more preferably 0.01 mmol / g cellulose to 5 mol / g cellulose, and still more preferably 0.1 mmol / g cellulose to 1 mol / g cellulose. Therefore, D is preferably 0.00002 mmol / g cellulose / nm to 10 mol / g cellulose / nm, more preferably 0.0002 mmol / g cellulose / nm to 5 mol / g cellulose / nm, and 0.002 mmol / g cellulose / nm. More preferably, ˜1 mol / g cellulose / nm.

  The composite of the present invention is supported on the surface of the cellulosic fiber by using, as a contact point, an acid group generated by oxidizing an acid group or an aldehyde group present on the surface of the cellulosic fiber. That is, the metal nanoparticles are fixed to the cellulosic fiber surface via acid groups present on the cellulosic fiber surface. The chemical bond for immobilization includes a coordination bond, a hydrogen bond, or an ionic bond. The bonding state can be analyzed by X-ray photoelectron spectroscopy or infrared spectroscopy.

  When the nanoparticles of the metal M are supported on the surface of the cellulosic fiber, the composite of the present invention may be referred to as “M composite”. For example, a complex in which the metal M is platinum is referred to as a “platinum complex”.

3. Use of the complex of the present invention The complex of the present invention can be used as a catalyst for various reactions. In particular, the complex of the present invention is preferably used as a compound oxidation or reduction catalyst. Examples of the compound include organic substances such as 4-nitrophenol and methanol, and inorganic substances such as nitric oxide. Since the composite of the present invention contains cellulose having affinity for water and an organic solvent, it can be dispersed in a solvent to form a dispersion. A compound can be charged into this dispersion to conduct a catalytic reaction. The conditions for the catalytic reaction may be appropriately adjusted depending on the target compound.

  Alternatively, the dispersion containing the composite of the present invention may be applied on a substrate such as glass to form a film, and the reaction may be carried out by charging the reaction system. Alternatively, a catalytic reaction may be performed by passing a reaction solution through the film.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited to this.

<Manufacture of cellulose fiber (pulp) having an aldehyde group>
Bleached softwood unbeaten pulp (manufactured by Nippon Paper Industries Co., Ltd.) 5 g (absolutely dried) was converted to N-oxyl compound 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, Sigma Aldrich) 78 mg (0. 5 mmol) and 754 mg (7.4 mmol) of sodium bromide were dissolved, and the mixture was stirred until the pulp was uniformly dispersed. After adding 8 ml of 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with 0.5N aqueous hydrochloric acid solution to start the oxidation reaction (oxidation treatment). During the reaction, the pH in the system was lowered, but a 0.5N aqueous sodium hydroxide solution was successively added to adjust the pH to 10. After reacting for 2 hours, the mixture was filtered through a glass filter and washed thoroughly with water to obtain a cellulose fiber (oxidized pulp) having a carboxyl group amount of 1.18 mmol / g and an aldehyde amount of 0.349 mmol / g.

(Carboxyl group content of oxidized pulp)
Prepare 60 ml of 0.5% by weight slurry of oxidized pulp, add 0.1 M hydrochloric acid aqueous solution to pH 2.5, then add 0.05 N aqueous sodium hydroxide solution dropwise until the pH is 11 Was calculated from the amount (a) of sodium hydroxide consumed in the neutralization step of the weak acid where the change in electrical conductivity was gradual, using the following equation.
Amount of carboxyl group [mmol / g pulp] = a [ml] × 0.05 / oxidized pulp mass [g].

(Aldehyde group content of oxidized pulp)
The oxidized pulp was converted from aldehyde groups to carboxyl groups using an aqueous sodium chlorite solution. By measuring the difference in the amount of carboxyl groups before and after conversion, the amount of aldehyde groups in the oxidized pulp was measured.

<Manufacture of oxidized pulp sheet>
The obtained oxidized pulp was diluted to 0.1% with tap water, and a handmade sheet was prepared using a round handmade device (manufactured by Tozai Seiki). The prepared sheet was dried at 105 ° C. for 20 minutes by a blower dryer to complete an oxidized pulp sheet.

<Example 1>
As a result of immersing the oxidized pulp sheet obtained above in 0.5 mM HAuCl ₄ for 12 hours, the oxidized pulp sheet after the immersion changed from white to reddish purple (FIG. 1B). Further, as a result of observation with a scanning electron microscope (FESEM), it was shown that synthesis was performed with nanoparticles having a particle size of about 10 nm dispersed on the fiber surface (FIG. 2B). Further, when the metal-supported oxidized pulp sheet was confirmed by X-ray diffraction (XRD), a peak of Au crystal was obtained at a position of 2θ = 38 ° (FIG. 3B). Furthermore, a characteristic X-ray peak derived from Au was confirmed by energy dispersive X-ray analysis (EDX) (FIG. 4). Further, the catalytic performance of this sheet was evaluated by following the aqueous reduction reaction from 4-nitrophenol (NP) to 4-aminophenol (AP) by ultraviolet / visible spectroscopy (UV-vis) analysis (FIG. 5). ) As a result, it was confirmed that 4-nitrophenol decreased and 4-aminophenol increased with the passage of time.

<Comparative Example 1>
The color of the oxidized pulp sheet obtained above (a sheet containing an aldehyde group and a carboxyl group not carrying a metal) was white (FIG. 1 (a)). Further, as a result of observation with a scanning electron microscope, adhesion of metal nanoparticles to the sheet was not confirmed (FIG. 2 (a)). Further, when X-ray diffraction was confirmed, a peak of Au crystal was not confirmed at a position of 2θ = 38 ° (FIG. 3 (a)).

<Comparative example 2>
After all the aldehyde groups of the oxidized pulp sheet obtained above were oxidized and converted to carboxyl groups, the sheet was immersed in HAuCl ₄ for 12 hours. As a result, no change in sheet color was observed (FIG. 1 (c)). ).

<Example 2>
5 g (absolutely dried) of bleached softwood unbeaten pulp (made by Nippon Paper Industries Co., Ltd.) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (Sigma Aldrich) and 754 mg (7.4 mmol) of sodium bromide were dissolved. Stir until evenly dispersed. After adding 15.6 ml (30 mmol) of 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with 0.5N aqueous hydrochloric acid solution to start the oxidation reaction (oxidation treatment). During the reaction, the pH in the system was lowered, but a 0.5N aqueous sodium hydroxide solution was successively added to adjust the pH to 10. After reacting for 2 hours, the mixture was filtered through a glass filter and washed thoroughly with water to obtain a cellulose fiber (oxidized pulp) having a carboxyl group amount of 1.65 mmol / g and an aldehyde group amount of 0.23 mmol / g.

5 g of the oxidized pulp obtained above was stirred in 0.25 L of a 32 mM CuCl ₂ .2H ₂ O solution for 1 hour, and then excess CuCl ₂ was removed by dehydration and washing. Allowed to stand for a period of time to generate metal nanoparticles.

<Metal nanoparticle-supported oxidized pulp sheet>
The metal nanoparticle-supported oxidized pulp obtained above was diluted to 0.1% with tap water, and a handmade sheet was prepared using a round handmade device (manufactured by Tozai Seiki). The prepared sheet was dried at 105 ° C. for 20 minutes by a blow dryer to complete the sheet. As a result of observing the sheet with a scanning electron microscope (FESEM), it was shown that the sheet was synthesized with Cu nanoparticles having a particle size of about 30 nm dispersed on the fiber surface (FIG. 6).

<Example 3>
As a result of carrying out in the same manner as in Example 2 except that a 16 mM CuCl ₂ solution was used, it was shown that synthesis was performed in a state where Cu nanoparticles having a particle diameter of about 30 nm were dispersed on the fiber surface.

<Example 4>
As a result of carrying out in the same manner as in Example 2 except that 32 mM AgNO ₃ solution was used, it was shown that Ag nanoparticles having a particle diameter of about 30 nm were synthesized on the fiber surface.

<Example 5>
As a result of carrying out in the same manner as in Example 2 except that 1.41 g of ascorbic acid was added as a reducing agent after stirring for 1 hour using a 32 mM AgNO ₃ solution, Ag nanoparticles having a particle size of 30 nm were dispersed on the fiber surface. It was shown that it was synthesized in the state.

<Example 6>
The oxidized pulp obtained in the same manner as in Example 2 was made into a slurry having a solid concentration of 1% by mass, and treated with a high-pressure homogenizer at 20 ° C. and a pressure of 140 MPa five times to obtain a transparent cellulose nanofiber dispersion. To 500 g of the cellulose nanofiber dispersion obtained above, 8 mmol of CuCl ₂ .2H ₂ O was added and stirred for 1 hour, and then allowed to stand for 24 hours to produce metal nanoparticles. As a result, it was shown that Cu nanoparticles with a particle diameter of about 30 nm were synthesized in a dispersed state.

<Example 7>
As a result of carrying out in the same manner as in Example 6 except that 8 mmol of AgNO ₃ was used, it was shown that Ag nanoparticles having a particle diameter of about 30 nm were synthesized in a dispersed state.

<Comparative Example 3>
The same procedure as in Example 2 was conducted except that bleached softwood unbeaten pulp (manufactured by Nippon Paper Industries Co., Ltd.) was not oxidized. Cu nanoparticles were not observed on the fiber surface (FIG. 7).

Claims (10)

Step 1 of preparing a cellulosic fiber having an aldehyde group on the surface, and contacting the cellulosic fiber with an aqueous metal compound solution to reduce the metal compound with an aldehyde group on the surface of the cellulosic fiber; Step 2 of forming metal nanoparticles on the surface
The manufacturing method of the composite_body | complex of a metal nanoparticle and a cellulose fiber containing this.   The metal nanoparticles may include carboxyl groups or carboxylate groups generated by oxidation of the aldehyde groups, carboxyl groups or carboxylate groups further included on the surface of the cellulose fiber in the step 1, or both of them. The manufacturing method of Claim 1 which has couple | bonded.   The said metal nanoparticle is a manufacturing method of Claim 1 or 2 containing the element which belongs to 8-12 group in a periodic table.   The average particle diameter calculated | required from the transmission electron microscope image of the said metal nanoparticle is a manufacturing method of any one of Claims 1-3 which is 1-50 nm.   The said cellulosic fiber is a manufacturing method of any one of Claims 1-4 which is a pulp.   The said cellulosic fiber is a manufacturing method of any one of Claims 1-4 which is a cellulose nanofiber.   The manufacturing method according to claim 6, wherein the cellulose nanofiber is crystalline.   The manufacturing method of Claim 6 or 7 whose average fiber diameter calculated | required from the scanning electron microscope image of the said cellulose nanofiber is 2.5-20 nm.   The said cellulose fiber is a manufacturing method of any one of Claims 1-8 which is a cellulose fiber obtained by oxidizing a cellulose using N-oxyl compound in water.   The composite_body | complex manufactured with the manufacturing method of any one of Claims 1-9.