Nano-Composite and Method of Producing the Same

Abstract

The present invention is related to a method of producing nano-composites, which has the following steps: providing a solution, the solution has a substrate and a precursor of a zero-dimensional nanoparticles; subjecting a surface of the solution to a plasma to activate the precursor to generate the zero-dimensional nanoparticles in the solution; whereby the nanoparticles are self-assembled on the substrate uniformly to generate the nano-composites.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for producing a nano-composite, and particularly a method for manufacturing self-assembling nano-composite by plasma.

2. Description of the Prior Art

Nanoparticles, such as the precious metal gold (Au), silver (Ag), platinum (Pt) nanoparticles, have been widely used and generally in chemical reaction as catalyst. Germanium (Ge) applied with nano technology is greatly used in the semiconductor industry. Iron (Fe), cobalt (Co), nickel (Ni) and other transition metal nanoparticles were overwhelmingly applied to military, civilian or electronic industry, etc. Due to high specific surface area or enhanced mechanical, modified physical and chemical properties of the metal nanoparticles, the development of nanometer-grade metal materials continuously acquires public attention.

Conventional preparation of nanoparticles is mainly performed by a wet chemical method. This kind of method has an advantage on the production yield. However, for the present preparation method, the reaction time required for preparation is too long (typically several hours are required), the size of nanoparticles is not even, excessive agglomeration of nanoparticles occurs or the additional purification steps to obtain the nanoparticles are too cumbersome, and the used surfactant or chemicals results in environmental pollution. Accordingly, the above problems are significantly limiting the development of nanoparticles.

In order to render nanometer-grade materials multiple-functional, many researches have attempted to take advantage of the semiconductor manufacturing process to generate nano-composite structure. However, the manufacturing process yields little nano-composites and is completely not feasible or beneficial to vast production, which results in a great hindrance in its industrial application.

SUMMARY OF THE INVENTION

In order to change the above-mentioned shortcomings of manufacture of nanoparticles and to solve the problems of methods for producing nano-composites yielding less and lacking of industrial use, the present invention provides a method of producing nanoparticles with uniform particle size by utilizing plasma process, which allows the nanoparticles directly being adsorbed on a pre-selected substrate, so that nanoparticles can self-assemble on the pre-selected substrate. Since the substrate is selected nanometer grade, a resultant different dimensional nano-composite is thus quickly and conveniently generated.

The present invention provides a method for producing nano-composite, comprising the steps of:

providing a reaction solution containing at least one dimensional nanomaterials and a precursor of zero-dimensional nanoparticles; and

applying plasma to a surface of the reaction solution or in the reaction solution to generate the zero-dimensional nanoparticles from the precursor of the zero-dimensional nanoparticles to assemble on the at least one dimensional nanomaterials to obtain a nano-composite dispersed in the reaction solution.

The present invention also provides a diverse multiple-dimensional nano-composite, which is formed by binding the zero-dimensional nanoparticles to the surface of the at least one dimensional nanomaterials, which is due to the electrical potential difference, different charge, surface characteristics or attraction between molecules.

In this way, the present invention includes the following features to achieve the following technical effects:

1. the present invention provides a method for directly producing a large amount of nanoparticles with evenly dispersion through the adjustment of formulation to generate nanoparticles directly synthesized or attached on a surface of a selected substrate, nanoparticles being uniformly attached to the surface of the substrate, which results in an advanced method of producing a self-assembled nano-composite having diverse multiple-dimensional structure to solve the problem in industrial production of nanoparticles, and more to solve the problem in redundant procedure for dispersion of nanoparticles or nano-composites;

2. the present invention provides a solution for resolving the need of nanomaterials for different purpose, by choosing desired nanoparticles and substrates to obtain various diverse multiple-dimensional nano-composite, which result from precise choice of material to grow to concur the barrier of current technique to provide a more diverse, less restrictive, more simple and efficient method for producing the same;

3. the present invention utilizes plasma manufacturing process to increase absorption effect between the metal nanoparticles and the substrate, completely different from the existing particle/substrate synthesis; in the aspect of applications, the present invention provides a substance comprising metal nanoparticles with enhanced Raman spectroscopy, which makes it ideally suitable for enhancing surface Raman spectroscopy (SERS) effect for use in related applications, wherein the resulting nano-composite, compared to pure nanoparticles, more obviously and hugely increase the effect than that of the prior art;

4. the present invention utilizes plasma process to make large amounts of metal particles uniformly disperse in the solution or the surface of the substrate, proven by the analysis of effect on the present invention when is applied to the surface enhanced Raman spectroscopy being beyond better than existing materials; and thus the present invention can be effectively applied to the material characteristics detection, biomedical industry, food safety and environmental pollution monitoring and prevention, and other purposes; and

5. the present invention provides nanoparticles without adding additional surfactant to achieve uniform dispersion of nanoparticles, which solves the problems in the art that requires using an organic solvent, to rendering the process environmentally friendly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 being an illustrative diagram of a preferred embodiment of the reaction apparatus according to the present invention;

FIG. 2 illustrating the first preferred embodiment of the reaction apparatus of the present invention;

FIG. 3 being a schematic view of the first preferred embodiment of the invention further provided in combination with a membrane for proton exchange;

FIG. 4 being a SEM image of the surface of the graphene substrate before reaction;

FIG. 5 being a SEM image of the first preferred embodiment of the present invention, which is obtained after reaction via the method according to the present invention;

FIG. 6 being a diagram obtained from a Raman signal test of the first preferred embodiment of the present invention;

FIG. 7 being a diagram obtained from Raman test of R6G raw material;

FIG. 8 illustrating comparison of the results between the nano-silver graphene composite prepared by the first preferred embodiment of the method according to the present invention the R6G only;

FIG. 9 being a SEM image of the surface of the graphene substrate obtained by the second preferred embodiment of the method according to the present invention;

FIG. 10 illustrating comparison of the results between nano silver graphene composite prepared by the second preferred embodiment of the method according to the present invention and graphene only;

FIG. 11 illustrating comparison of the results between nano silver graphene composite prepared by the second preferred embodiment of the method according to the present invention and R6G only;

FIG. 12 being SEM image of the nano gold particle composite according to the present invention; and

FIG. 13 being a EDS diagram of the nano gold particle composite according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the present invention provides a method for producing a diverse multiple-dimensional nano-composite, which takes advantage of a reaction apparatus 10, and a plasma generating device 20, wherein the reaction apparatus 10 receives a reaction liquid, the reaction liquid comprising at least one precursor of zero-dimensional nanoparticle, where the precursor may be molecular or ionic nanoparticles. The plasma generating device 20 generates plasma onto the surface of the reaction liquid or into the reaction liquid, and the plasma in the reaction liquid reduces or complexes the precursor to form the zero-dimensional nanoparticles uniformly dispersed in the reaction liquid. The reaction liquid could contain a substrate, which is at least one dimensional nanomaterial, and the substrate could be uniformly dispersed or suspended in the reaction liquid, such that the nanoparticles are reduced or generated to attach immediately to the substrate. The nanoparticles self-assembled to form diverse multiple-dimensional nano-composites. The at least one dimensional nanomaterials includes nanotubes, nanowires, nanoribbon, nanosheet or nanospheres or nanopolyhedron. The at least one dimensional nanomaterials could be a sub-micron or other magnitude. As the aforementioned process, the zero-dimensional nanoparticles self-assembled and uniformly dispersed on the surface of the at least one dimensional nanomaterials.

Mainly due to the use of the plasma, the reaction liquid is allowed generating the zero-dimensional nanoparticles, which are uniformly dispersed into the reaction liquid. The reaction liquid contents an amount of charges or charged particles or because of the molecular attraction between the particles, the zero-dimensional nanoparticles hardly aggregate and cumulate but uniformly disperse on the surface of the substrate.

The above plasma generating device 20 includes an atmospheric pressure plasma source or an atmospheric pressure microplasma source. The plasma could be generated by Argon or other gases under one atmospheric pressure or a pressure close to atmospheric pressure to produce the plasma. In the present embodiment, after the plasma was generated at an atmospheric pressure and in contact with the reaction liquid, high-energy particles carried by plasma strike the surface of the liquid to form a hydrated electron. The zero-dimensional nanoparticles in reaction liquid self-assemble on the substrate by hydrated electrons reduction. The zero-dimensional nanoparticles uniformly disperse in the reaction liquid due to large amount of charge or charged particles and no aggregation occurs.

Further, the present invention has an electron receiving unit 30 deposited in the reaction liquid, for receiving released electrons from the plasma generating device 20, and providing a continuous ion for synthesis of metal nanoparticles. For example, when the gold nanoparticles are desired, the electron receiving unit 30 could be made of gold to form a continuous reaction environment. The electron receiving unit 30 provides an ionic form of desired gold nanoparticles in the reaction liquid. The ionic form of desired gold nanoparticles are reduced to form the desired gold nanoparticles.

Further referring to Table 1, the present invention, the preferred embodiment of the reaction liquid is prepared with a precursor of the desired metal nanoparticles, or a precursor of the desired metal nanoparticles and substrate. The precursor of the desired metal nanoparticles is preferably a salt of metal, which is dissolved in a solvent to dissociate into metal ion, such as silver ion, gold ion, copper ion and the like.

The substrate may be two-dimensional nanomaterial, three-dimensional nanomaterial, which include but not limited to graphene, functionalized graphene, molybdenum disulfide (MoS₂), graphene nanoribbon (GNR) or carbon nanotube (CNT) uniformly distributed in the reaction liquid. The generated nanoparticles are adsorbed or adhered to at least a portion of the surface of the substrate.

TABLE 1
Metal for      silver (Ag), gold (Au), copper (Cu), platinum (Pt),
synthesized of iridium (Ir), ferrum (Fe)
Precursor      silver nitrate, Chloroauric Acid, Copper(II) Sulfate,
thereof        Dihydrogen hexachloroplatinate (IV) hexahydrate,
               Iridium(III) chloride trihydrate, iron(III) oxide
Substrate      graphene, MoS2, graphene nanoribbon (GNT), carbon
thereof        nano tube (CNT)

The reaction liquid may further add polysaccharides or other polymers to prevent the nanoparticles agglomeration. The polysaccharides may be but not limited to fructose or glucose. The said polymers may be, for example, polyvinylpyrrolidone (PVP) or trisodium citrate (TSC). The polyvinylpyrrolidone (PVP) and the trisodium citrate have a slight reduction effect, thus to enhance reduction of the nanoparticles.

When depositing the electron receiving unit 30, the substrate could be only uniformly dispersed in the reaction liquid, the precursor may not be necessary during using the electron receiving unit 30. Only when the plasma is applied to the reaction liquid, the electron receiving unit 30 continues to provide an ion for synthesis of nanoparticles in the reaction liquid. Desired nanoparticles are synthesized by reduction, and meanwhile they self-assemble on and attach to the local surface of the substrate.

Referring to FIG. 2, the plasma generating device 20 could produce plasma through the use of high-voltage high-power resistor or voltage stabilizing circuit to stably introduce the current (high voltage and low current (mA)), and then introduce the plasma gas argon (Ar) or other reaction gas to form normal pressure plasma or microplasma.

EXAMPLE 1

The first preferred embodiment of the present invention is manufacture of silver nanoparticles. The reaction apparatus 10 contained a reaction liquid containing a solution of silver nitrate at a concentration ranging from about 1 mM to 0.01 M, graphene and fructose.

The plasma generating device 20 applied a plasma to the reaction liquid. The plasma with high-energy particles struck the surface of the reaction liquid and produced hydrated electrons to obtain silver nanoparticles by reduction. The equation of the reaction in the reaction liquid was as followed:

e_aq+Ag⁺→Ag

e_aqH→H₂+OH⁻

Ag⁺+e_aq→Ag⁰→small Ag cluster→Ag nano particles

Referring to FIG. 3, the present invention could be further provided with a proton exchange membrane in the reaction liquid to achieve the same reaction process.

Referring to Table 2, using the method of Example 1, the present invention is applicable to the manufacture of other metal nanoparticles, wherein the ratio of the concentration of the reaction liquid to the added material was shown in Table 2.

TABLE 2
Zero-
dimensional	Concentration of the
metal	precursor of the desired
nanoparticle	metal nanoparticles	substrate	electrolyte
silver	Silver nitrate for about1	graphene	fructose,
	mM~0.01M		nitric acid
gold	Chloroauric acid for about	graphene	fructose,
	1 mM~0.01M		hydrochloric acid
copper	copper sulfate for about1	graphene	fructose,
	mM~0.01M		nitric acid
platinum	chloroplatinic acid for	graphene	sodium chloride,
	1 mM~0.01M		hydrochloric acid
iron	ferric oxide for about	graphene	sodium chloride
	5~10 wt %
iridium	iridium trichloride for	graphene	citric acid
	about 1 mM~0.01M

EXAMPLE 2

Illustrated was the second preferred embodiment of the present invention, wherein the electron receiving unit 30 could be an electrode for directly providing zero-dimensional nanoparticles, such as a silver electrode, a gold electrode, a copper electrode or a carbon rod. When the plasma generating device 10 provided a large amount of high-energy electrons in the reaction liquid, the electron receiving unit 30 released ions of the zero-dimensional nanoparticles to react with the electrons to generate the zero-dimensional nanoparticles by reduction. The system according to the present embodiment was applicable to manufacture of various metal nanoparticles and further attached to a portion or entire surface of the substrate to generate a diverse multiple-dimensional nanocomposite.

As described in Example 1, the present embodiment was further provided with a proton-exchange membrane in the reaction liquid.

Referring to Table 3, the suitable materials added in the reaction liquid of Example 2 were listed.

TABLE 3
Type of electron
receiving unit	Type of substrate	Type of electrolyte
silver electrode	graphene	fructose, nitric acid
gold electrode	graphene	fructose, hydrochloric acid
copper electrode	graphene	fructose, nitric acid

Referring to FIG. 4 and FIG. 5, FIG. 4 demonstrated a SEM image of the surface of graphene substrate before reaction. FIG. 5 demonstrated a SEM image of the surface of graphene substrate according to the reaction method according the first preferred embodiment of the present invention, wherein the surface of the substrate was attached with many silver nanoparticles, demonstrating the metal nanoparticles could be successfully attached to the surface of graphene substrate.

Referring to FIGS. 12 to 13, an electronic microscopy and EDS detection result shown the growing gold nanoparticles on the surface of the substrate. As shown in FIG. 12, after the plasma treatment, the surface of the substrate formed nanoparticles. With further elemental analysis by EDS, the formed nanoparticles on the surface of the substrate were made of gold. According to this result, the method according to the present invention is useful for effectively forming nanoparticles on various substrates and nanoparticles are self-assembled on the substrate, generating the diverse multiple-dimensional nano-composite.

As the aforementioned Examples, the method according to the present invention can be very efficient to allow nanoparticles self-assembling on selected substrates. The resultant diverse multiple-dimensional nano-composite may have two different characteristics, diverse multiple-dimensional nanomaterials, and can generate novel and unique material properties. It was proven that, to form different combinations of a metal or non-metallic materials of zero-dimensional nanomaterials and a substrate, the reaction liquid, the precursor and the substrate are selected to achieve the desired effect that cannot be reached by the prior art.

The metal and metal nano-composite could be a material for enhancing enhance factor while measured by Raman spectrum of the surface of the material. In general, the spontaneity of the Raman scattering is very weak, such that Raman spectroscopy measurement results are usually difficult to identify, leading to difficulties in measurement. The obtained nano-composite according to the present invention uniformly disperse on a substrate surface, such that when used with other material for analysis, the testing incident light can enhance Raman spectroscopy of the analyte signal by metal nanoparticles/substrate to more clearly identify the test substance.

Referring to FIG. 6, A which represented the nano-composite obtained from silver ions and graphene according to the first embodiment of the present invention, was enhanced by 70 times in Comparison to B, Raman signal of the pure graphene. Therefore, in terms of application of surface enhanced Raman spectroscopy (SERS), the present invention acquired a better surface enhanced Raman spectroscopy effect in comparison to the current technique being directly mixing metal particles with graphene without complete association therebetween.

Referring to FIGS. 7 to 8, FIG. 7 demonstrated a signal of Rhodamine 6G (R6G) in Raman signal test, showing intensity of the R6G feature peaks to be only around dozens. Comparing the silver and graphene nano-composite according to the first preferred embodiment of the present invention in FIG. 8 and Raman signal of R6G in FIG. 7, that panel (a) represented silver and graphene nano-composite prepared by Example 1 of the present invention by using a current of 4 mA, a reaction time of 20 minutes, panel (b) represented silver and graphene nano-composite prepared by Example 1 of the present invention by using a current of 5 mA, a reaction time of 20 minutes, panel (c) represented silver and graphene nano-composite prepared by Example 1 of the present invention by using a current of 6 mA, a reaction time of 20 minutes, and panel (d) represented silver and graphene nano-composite prepared by Example 1 of the present invention by using a current of 7 mA, a reaction time of 20 minutes. Comparing to the R6G test results, Raman signal of the nanoparticles obtained by Example 1 of the present invention was enhanced to about 10 to 60 times.

Referring to FIGS. 4 and 9, FIG. 4 was a SEM image of the surface of the graphene substrate before reaction, and the FIG. 9 was a SEM image of the surface of the graphene prepared by the second preferred embodiment of the method according to the present invention, wherein silver nanoparticles were attached to the graphene substrate, showing the success of the present invention to form metal nanoparticles on the surface of the graphene substrate.

Referring to FIGS. 7, 10 to 11, C in FIG. 10 showed a Raman signal diagram of the silver and graphene nano-composite prepared by Example 2 of the present invention. Comparing to D, a test result of pure graphene material, the present invention could increase the Raman signal to about 200 times. Comparing Raman signal test result of pure R6G in FIG. 7, silver and graphene nano-composite prepared by Example 2 of the present invention as shown in FIG. 11, the present invention further increased Raman signal to about 100 to 400 times.

According to the above results, by using reaction system as the second preferred embodiment of the present invention, the surface of the substrate was able to absorb more of the metal nanoparticles, leading to a resultant enhanced Raman scattering spectra effect higher than that of the first preferred embodiment of the invention. The main factor could be that direct use of electrode made of an element of the synthetic nanoparticles in the second preferred embodiment, comparing to the first preferred embodiment of the present invention. Therefore, in the second preferred embodiment of the present invention, the substrate can adsorb more nanoparticles on its surface. According to the above description, the present invention has the following advantages:

1. the present invention provides a method for directly producing a large amount of nanoparticles with evenly dispersion through the adjustment of formulation to generate nanoparticles directly synthesized or attached on a surface of a selected substrate, nanoparticles being uniformly attached to the surface of the substrate, which results in an advanced method of producing a self-assembled nano-composite having multiple-dimensional structure to solve the problem in industrial production of nanoparticles, and more to solve the problem in redundant procedure for dispersion of nanoparticles or nano-composites;

2. the present invention provides a solution for resolving the need of nanomaterials for different purpose, by choosing desired nanoparticles and substrates to obtain various diverse multiple-dimensional nano-composite, which result from precise choice of material to grow to concur the barrier of current technique to provide a more diverse, less restrictive, more simple and efficient method for producing the same;

3. the present invention utilizes plasma manufacturing process to increase absorption effect between the metal nanoparticles and the substrate, completely different from the existing particle/substrate synthesis; in the aspect of applications, the present invention provides a substance comprising metal nanoparticles with enhanced Raman spectroscopy, which makes it ideally suitable for enhancing surface Raman spectroscopy (SERS) effect for use in related applications, wherein the resulting nano-composite, compared to pure nanoparticles, more obviously and hugely increase the effect than that of the prior art;

4. the present invention utilizes plasma process to make large amounts of metal particles uniformly disperse in the solution or the surface of the substrate, proven by the analysis of effect on the present invention when is applied to the surface enhanced Raman spectroscopy being beyond better than existing materials; and thus the present invention can be effectively applied to the material characteristics detection, biomedical industry, food safety and environmental pollution monitoring and prevention, and other purposes; and

5. the present invention provides nanoparticles without adding additional surfactant to achieve uniform dispersion of nanoparticles, which solves the problems in the art that requires using an organic solvent, to rendering the process environmentally friendly.

Claims

1. A method for producing nano-composite, comprising the steps of: providing a reaction solution containing at least one dimensional nanomaterials and a precursor of zero-dimensional nanoparticles; andapplying plasma to a surface of the reaction solution or in the reaction solution to generate the zero-dimensional nanoparticles from the precursor to assemble on the at least one dimensional nanomaterials to obtain the nano-composite;whereby the nanoparticles self-assemble on the surface of the at least one dimensional nanomaterials in the reaction solution to form the nano-composite dispersed in the reaction solution.

2. The method according to claim 1, wherein the zero-dimensional nanoparticles include metal or non-metal nanoparticles; and the at least one dimensional nanomaterials contain nanotubes, nanowires, nanoribbon, nano-platelets or nano-spheres.

3. The method according to claims 1, wherein the plasma is atmospheric plasma or microplasma; the zero-dimensional nanoparticles are silver nanoparticles, gold nanoparticles, copper nanoparticles, platinum nanoparticles, iridium nanoparticles or iron nanoparticles; and the at least one dimensional nanomaterials comprise nanoparticles of graphene, functionalized graphene or molybdenum disulfide, graphene nanoribbon, or carbon nanotubes.

4. The method according to claims 2, wherein the plasma is atmospheric plasma or microplasma; the zero-dimensional nanoparticles are silver nanoparticles, gold nanoparticles, copper nanoparticles, platinum nanoparticles, iridium nanoparticles or iron nanoparticles; and the at least one dimensional nanomaterials are nanoparticles of graphene, functionalized graphene or molybdenum disulfide, graphene nanoribbon, or carbon nanotubes.

5. The method according to claim 3, wherein the reaction solution further contains silver nitrate, chloroauric acid, copper sulfate, chloroplatinic acid, iridium trichloride or ferric oxide.

6. The method according to claim 4, wherein the reaction solution further contains silver nitrate, chloroauric acid, copper sulfate, chloroplatinic acid, iridium trichloride or ferric oxide.

7. A diverse multiple-dimensional nano-composite, which is formed by binding zero-dimensional nanoparticles to surfaces of at least one dimensional nanomaterials, wherein the zero-dimensional nanoparticles bind to the surfaces of the at least one dimensional nanomaterials by the electrical potential difference, surface characteristics or attraction between molecules.

8. The diverse multiple-dimensional nano-composite according to claim 7, wherein the zero-dimensional nanoparticles include metal or non-metal nanoparticles; the at least one dimensional nanomaterials contain nanotubes, nanowires, nanoribbons, nano-platelets or nano-spheres.

9. The diverse multiple-dimensional nano-composite according to claims 7, wherein the zero-dimensional nanoparticles are silver nanoparticles, gold nanoparticles, copper nanoparticles, platinum nanoparticles, iridium nanoparticles or iron nanoparticles; and the at least one dimensional nanomaterials are nanoparticles of graphene, functionalized graphene or molybdenum disulfide, carbon nanotubes or graphene nanoribbons.

10. The diverse multiple-dimensional nano-composite according to claims 8, wherein the zero-dimensional nanoparticles are silver nanoparticles, gold nanoparticles, copper nanoparticles, platinum nanoparticles, iridium nanoparticles or iron nanoparticles; and the at least one dimensional nanomaterials are nanoparticles of graphene, functionalized graphene or molybdenum disulfide, carbon nanotubes or graphene nanoribbons.

11. The diverse multiple-dimensional nano-composite according to claim 7, wherein the zero-dimensional nanoparticles and the at least one dimensional nanomaterials are subjected to a more than one-atmospheric pressure or a low pressure plasma to have electric potential difference, different charge, surface characteristics or attraction between molecules.