CN110586952A - Room temperature preparation method of nano metal powder and conductive ink thereof - Google Patents

Abstract

The invention discloses a room temperature preparation method of nanometer metal powder and conductive ink thereof. The room temperature preparation method of nanometer metal powder comprises the following steps: injecting solution B into solution A at room temperature and in an ultrasonic state to obtain a mixed solution, Adding a washing solvent into the mixed solution, washing by centrifugation, and the precipitate obtained after washing is nanometer metal powder. The preparation of conductive ink with nano-metal powder comprises the following steps: ultrasonically dispersing the nano-metal powder in a mixed solvent to obtain a nano-metal conductive ink. Compared with the prior art, the particle size of the nano-metal powder prepared by the present invention is 5- 20nm, with high oxidation resistance, it will not be oxidized when stored in the air for more than one year, and large-scale production can be realized at room temperature; the conductive ink has high conductivity, and the resistivity of electronic devices after infrared sintering in air is only that of traditional gold and silver wires 2‑8 times of copper wire or about 20 times of copper wire, and the resistivity can remain unchanged for a long time in the air.

Description

Room temperature preparation method of nanometer metal powder and conductive ink thereof

technical field

The invention belongs to the technical field of nanometer material preparation, and in particular relates to a room temperature preparation method of nanometer metal powder and conductive ink thereof.

Background technique

Printed electronics technology refers to the printing of various conductive inks on various substrates to prepare large-area, flexible and low-cost electronic products or devices. Conductive ink can be applied in many fields such as: electronic newspaper (EP), curved display screen, wireless intelligent identification electronic tag (RFID), printed circuit board (PCB), thin film sensor (TFS) and solar panel (TFSB), etc. With the social and economic development trend of green production, energy saving and emission reduction, conductive ink will surely become a key material for the sustainable development of printed electronics technology and the electronics industry.

Conductive inks are mainly composed of metal nanoparticles (gold, silver, copper or nickel, etc.) or non-metallic fillers (carbon materials, etc.), thermosetting resins, benign solvents, and some surfactants, plasticizers, and defoamers that improve ink properties. etc., and the preparation of metal nanoparticles or non-metallic fillers with conductive function is the key to ink quality, because it is the only source of conductivity for printed wires or conductive patterns. Generally speaking, because the conductivity of metal itself is higher than that of non-metal, the conductivity of metal-based conductive ink is higher than that of non-metal-based conductive ink.

At present, there are many research reports on metal-based conductive inks. Companies such as Flint Ink Company of the United States and ABC Nanotechnology of South Korea have developed commercially available nano-silver conductive inks. However, due to the high production cost and complicated process, large-scale applications cannot be realized. In China, only universities and scientific research institutes conduct research, and it is still in its infancy. Most of the reported methods for preparing silver nanoparticles require heating at a certain temperature. For example, the low temperature reported in Chinese patent CN 102220045A still requires 20-70°C, and the preparation method is complicated. , the preparation process or the solvent of the conductive ink has environmental pollution, etc. In order to improve its oxidation resistance, an inert atmosphere protection is often required. After sintering at 50-150 ° C, the final resistivity is as high as close to 1000 micro-ohm cm, and the practical application range is relatively large. Small, difficult to achieve large-scale production. In order to make the prepared conductive pattern have higher conductivity (lower resistivity), it generally needs to be sintered under the protection of 120-320°C inert atmosphere, such as nitrogen, argon, etc., and the operation process is complicated. °C (such as CN 101870832A). Therefore, it is necessary to develop and prepare nano-metal powders and conductive inks that can be mass-produced at room temperature, green, pollution-free, and highly stable, and high-conductivity nano-metal conductive inks that can be sintered by low-power microwaves in the air.

Contents of the invention

In view of the deficiencies in the prior art, the object of the present invention is to provide a method for preparing nano-metal powder at room temperature, and another object of the present invention is to provide a method for preparing conductive ink with the above-mentioned nano-metal powder;

Another object of the present invention is to provide an application of the above-mentioned conductive ink in improving the resistivity of electronic devices.

The purpose of the present invention is achieved through the following technical solutions.

A method for preparing nanometer metal powder at room temperature, comprising the following steps:

1) At room temperature, in an ultrasonic state, inject solution B into solution A to obtain a mixed solution, wherein the preparation methods of solution A and solution B are as follows:

Solution A: place the organic protective agent and reducing agent in deionized water and evenly dissolve the organic protective agent and reducing agent in the deionized water, adjust the pH value to 7.5-11 after dissolution, and obtain A solution, wherein the The organic protective agent is a nonionic surfactant and a cationic/anionic surfactant, and the molar ratio of the nonionic surfactant to the cationic/anionic surfactant is (0.1～2):1 ;

In the above technical solution, the concentration of the organic protective agent in the deionized water in which the organic protective agent is dissolved is 0.01-1.5mol/L.

In the above technical solution, the concentration of the reducing agent in the deionized water in which the reducing agent is dissolved is 0.04-0.6 mol/L.

In the above technical solution, the nonionic surfactant is polyvinylpyrrolidone, oleic acid, alkanolamide or fatty alcohol polyoxyethylene ether.

In the above technical solution, the cationic surfactant is 12, 14, 16, 18 alkyltrimethylammonium bromide, ammonium chloride, silicone oil or panthenol.

In the above technical solution, the anionic surfactant is sodium dodecylbenzenesulfonate, sodium fatty alcohol polyoxyethylene ether sulfate or sodium dodecylsulfate.

In the above technical solution, the reducing agent is a mixture of two or more of sodium hypophosphite, vitamin C (ascorbic acid), D-ascorbic acid and glucose.

In the above technical solution, the pH value is adjusted to 7.5-11 by adding an alkaline substance, and the alkaline substance is concentrated ammonia water and/or sodium hydroxide.

Solution B: adding the metal salt to deionized water, so that the metal salt is uniformly dissolved in the deionized water to obtain solution B, wherein the metal salt is copper salt, gold salt or silver salt;

Based on the amount of substances, the ratio of the reducing agent, the organic protecting agent and the metal salt is (4-20):(1-5):1;

In the above technical scheme, the concentration of the metal salt in the deionized water that dissolves the metal salt is

0.01-1mol/L.

In the above technical solution, the silver salt is one or more of silver nitrate, silver nitrite, silver acetate, silver carbonate, silver phosphate and silver chitosan.

In the above technical solution, the copper salt is one or a mixture of copper sulfate pentahydrate, copper chloride and copper nitrate.

In the above technical scheme, the gold salt is chloroauric acid and/or gold nitrate.

In the step 1), the operation method for uniformly dissolving the organic protective agent and the reducing agent in the deionized water is: continuous stirring for 3-30 minutes and then ultrasonication for 3-30 minutes.

In the step 1), the operation method for uniformly dissolving the metal salt in the deionized water is as follows: continuous stirring for 3-30 minutes and then ultrasonication for 3-30 minutes.

2) adding a washing solvent into the mixed solution, washing by centrifugation, and the precipitate obtained after washing is nano metal powder.

In the step 2), the ratio of the mixed solution to the washing solvent is 1:(2-5) in parts by volume.

In the step 2), the washing solvent is any one or a mixture of ethanol, acetone, and deionized water.

The method for preparing conductive ink with the above-mentioned nano-metal powder comprises the following steps: ultrasonically dispersing the nano-metal powder in a mixed solvent to obtain a nano-metal conductive ink, wherein the viscosity of the mixed solvent is 8-10000cps, by mass percentage In total, the nanometer metal powder accounts for 5-80%, and the mixed solvent accounts for 20-95%.

In the above technical scheme, the mixed solvent is ethanol, ethylene glycol, glycerol, diethylene glycol, monomethyl ether, ethyl acetate, butyl acetate, methoxy-2 propanol acetate, A mixture of two or more of butyl acetate, acrylic resin, silane coupling agent and deionized water.

In the above technical scheme, in terms of mass percentage, the mixed solvent is: ethanol 0-30wt%, ethylene glycol 5-30wt%, glycerol 3-20wt%, diethylene glycol 5-30wt%, monomethanol Ethyl ether 5-20wt%, ethyl acetate 0-8wt%, butyl acetate 0-5wt%, methoxy-2 propanol acetate 0-20wt%, butyl acetate 0-10wt%, acrylic resin 0- 20wt% and silane coupling agent 0-5wt%, the balance is deionized water.

The application of above-mentioned conductive ink in improving the resistivity of electronic device, described conductive ink is coated on the substrate of electronic device, infrared sintering or furnace temperature sintering 0～15min, the resistivity of the electronic device obtained is pure metal (gold, 2 to 8 times that of silver or copper), wherein the power of infrared sintering is 0-15W, and the furnace temperature is 25-100°C.

The coating method of coating the conductive ink on the substrate of the electronic device is inkjet, oil pen writing or brushing. When the coating method is inkjet, the viscosity of the mixed solvent is 8-20cps; When the coating method is oil pen writing, the viscosity of the mixed solvent is 20-1000cps; when the coating method is brushing, the viscosity of the mixed solvent is 1000-10000cps.

Compared with the prior art, the beneficial effects of the present invention are as follows:

1) The nanometer metal powder prepared by the present invention has a particle size of 5-20nm, has high oxidation resistance, and is not oxidized when stored in the air for more than one year, and large-scale production can be realized at room temperature;

2) The conductive ink prepared by the present invention has high conductivity, and the resistivity of electronic devices after infrared sintering in air is only 2-8 times that of traditional gold and silver wires or about 20 times that of copper wires, and can be placed in the air for a long time Resistivity remains constant;

3) The conductive ink of the present invention is suitable for preparing various printed electronic devices or functional parts thereof, and the process is simple, and large-scale production can be realized.

Description of drawings

Fig. 1 is the XRD collection of illustrative plates and the TEM photomicrograph of the conductive ink prepared by the present invention, wherein (a) is the XRD collection of collections after initial and storage 12 months, (b) TEM photomicrograph and conductive ink figure of gold nanoparticles;

Fig. 2 is the XRD collection of illustrative plates and the TEM photomicrograph of the conductive ink prepared by the present invention, wherein (a) is the XRD collection of collections after initial and storage 12 months, (b) TEM photomicrograph and conductive ink figure of silver nanoparticles;

Fig. 3 is the XRD collection of illustrative plates and the TEM photomicrograph of the conductive ink prepared by the present invention, wherein (a) is the XRD collection of collections after initial stage and storage 12 months, (b) TEM photomicrograph and conductive ink figure of copper nanoparticles;

Fig. 4 is that the electrical resistivity of embodiment 7 gained electronic device changes with sintering power;

Fig. 5 is that the resistivity of the electronic device obtained in embodiment 8 changes with the number of times of spraying;

FIG. 6 shows the resistivity of the electronic device obtained in Example 9 as a function of sintering time.

Detailed ways

In the following examples, the solid drugs were all purchased from Aladdin Pharmaceutical Co., Ltd., and the purity was 99.9% analytically pure. Except for the self-made ion water laboratory, the above-mentioned organic solvents were all purchased from Tianjin Jiangtian Uniform Technology Co., Ltd., the solvent mass fraction All greater than 99.7%.

The inkjet printer model is hp1010, and the infrared heating lamp for infrared sintering is provided by Guangzhou Langpu Photoelectric Technology Co., Ltd., with a power of 0-100W.

The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

Example 1

A method for preparing nanometer metal powder (gold powder) at room temperature, comprising the following steps:

1) At a room temperature of 20-25°C, under ultrasonic conditions, inject solution B into solution A to obtain a mixed solution, wherein the preparation methods of solution A and solution B are as follows:

Solution A: Dissolve the organic protective agent and reducing agent in deionized water and continue to stir for 10 minutes, then sonicate for 10 minutes, so that the organic protective agent and reducing agent are uniformly dissolved in the deionized water, and adjust by adding alkaline substances after dissolution When the pH value reaches 8, a solution A is obtained, wherein the alkaline substance is sodium hydroxide. The organic protective agent is a nonionic surfactant and a cationic surfactant, and the ratio of the nonionic surfactant to the cationic surfactant is 0.5:1 in terms of molar ratio; the organic protective agent is dissolved in the deionized water of the organic protective agent The concentration of the reducing agent is 0.05mol/L, and the concentration of the reducing agent in the deionized water in which the reducing agent is dissolved is 0.1mol/L; the nonionic surfactant is polyvinylpyrrolidone; the cationic surfactant is 16 alkyl trimethyl bromide Ammonium; the reducing agent is a mixture of sodium hypolinate and glucose, and the ratio of the parts by mass of sodium hypolinate to glucose is 2:1.

Solution B: Add the metal salt to deionized water, continue to stir for 15 minutes and then ultrasonically for 15 minutes, so that the metal salt is uniformly dissolved in the deionized water to obtain solution B, wherein the metal salt is chloroauric acid, and the metal salt is dissolved in the deionized water. The concentration of the metal salt in deionized water is 0.01 mol/L.

According to the amount of substances, the ratio of reducing agent, organic protective agent and metal salt is 10:5:1;

2) Adding a washing solvent to the mixed solution, washing by centrifugation, the precipitate obtained after washing is nano metal powder, wherein, in parts by volume, the ratio of the mixed solution to the washing solvent is 1:3, and the washing solvent is ethanol .

The prepared gold nanoparticles are shown in Figure 1(a), which confirms that the obtained gold nanoparticles (nano-metal powder) have good oxidation resistance, and the size of the gold particles is shown in Figure 1(b) TEM micrograph, about 5-15nm.

Example 2

A preparation method at room temperature of nano metal powder (silver powder) for infrared sintering, comprising the following steps:

1) At room temperature, in an ultrasonic state, inject solution B into solution A to obtain a mixed solution, wherein the preparation methods of solution A and solution B are as follows:

Solution A: Dissolve the organic protective agent and reducing agent in deionized water and continue to stir for 5 minutes, then ultrasonicate for 5 minutes, so that the organic protective agent and reducing agent are uniformly dissolved in the deionized water, and then adjust by adding alkaline substances When the pH value reaches 9, a solution A is obtained, wherein the alkaline substance is concentrated ammonia water. Organic protective agent is nonionic surfactant and anionic surfactant, and in molar ratio, the ratio of nonionic surfactant and anionic surfactant is 0.8:1; Organic protective agent dissolves the deionized water of this organic protective agent The concentration of the reducing agent is 0.08mol/L, and the concentration of the reducing agent in the deionized water dissolving the reducing agent is 0.3mol/L; the nonionic surfactant is oleic acid; the anionic surfactant is sodium dodecylbenzenesulfonate; The reducing agent is a mixture of vitamin C (ascorbic acid) and glucose, and the ratio of the mass parts of vitamin C (ascorbic acid) to glucose is 2:1.

Solution B: Add the metal salt to deionized water, continue to stir for 5 minutes and then ultrasonicate for 5 minutes, so that the metal salt is uniformly dissolved in the deionized water to obtain solution B, wherein the metal salt is silver nitrate, and the metal salt is dissolved in the deionized water. The concentration of the metal salt in deionized water is 0.05 mol/L.

Based on the amount of substances, the ratio of reducing agent, organic protective agent and metal salt is 6:1.6:1;

2) Add a washing solvent to the mixed solution, and wash by centrifugation. The precipitate obtained after washing is nano-metal powder (silver nanoparticles), wherein, in parts by volume, the ratio of the mixed solution to the washing solvent is 1:4 , the washing solvent is deionized water.

The prepared gold nanoparticles are shown in Fig. 2(a), which confirms that the obtained silver nanoparticles have good oxidation resistance. At the same time, the TEM micrographs show that the size of gold particles is about 5-20nm, as shown in Figure 2(b).

Example 3

A room temperature preparation method of nano metal powder (copper powder) for infrared sintering, comprising the following steps:

1) At room temperature, in an ultrasonic state, inject solution B into solution A to obtain a mixed solution, wherein the preparation methods of solution A and solution B are as follows:

Solution A: Dissolve the organic protective agent and reducing agent in deionized water and continue to stir for 8 minutes, then ultrasonicate for 8 minutes, so that the organic protective agent and reducing agent are uniformly dissolved in the deionized water, and adjust by adding alkaline substances after dissolution When the pH value reaches 10.5, a solution A is obtained, wherein the alkaline substance is sodium hydroxide. The organic protective agent is a nonionic surfactant and a cationic surfactant, and the ratio of the nonionic surfactant and the cationic surfactant is 1:1 in terms of molar ratio; the organic protective agent is dissolved in the deionized water of the organic protective agent The concentration of the reducing agent is 0.1mol/L, and the concentration of the reducing agent in the deionized water that dissolves the reducing agent is 0.5mol/L; the nonionic surfactant is oleic acid; the cationic surfactant is 14 alkyltrimethylammonium chloride ; The reducing agent is a mixture of D-ascorbic acid and sodium hypophosphite, and the mass fraction ratio of D-ascorbic acid and sodium hypophosphite is 2:1.

Solution B: Add the metal salt to deionized water, continue to stir for 5 minutes and then ultrasonicate for 5 minutes, so that the metal salt is uniformly dissolved in the deionized water to obtain solution B, wherein the metal salt is copper sulfate pentahydrate, and the metal salt is in The concentration of the deionized water in which the metal salt was dissolved was 0.025 mol/L.

Based on the amount of substances, the ratio of reducing agent, organic protective agent and metal salt is 20:4:1;

2) Adding a washing solvent to the mixed solution, washing by centrifugation, the precipitate obtained after washing is nano metal powder, wherein, in parts by volume, the ratio of the mixed solution to the washing solvent is 1:3.5, and the washing solvent is acetone .

The prepared copper nanoparticles are shown in Fig. 3(a), which confirms that the obtained silver nanoparticles have good oxidation resistance. At the same time, the TEM micrograph in Figure 3(b) shows that the gold particle size is about 20-80nm.

Example 4

The method for preparing conductive ink with the nano-metal powder (gold powder) of the above-mentioned embodiment 1 comprises the following steps: ultrasonically dispersing the nano-metal powder in a mixed solvent to obtain a nano-metal conductive ink, wherein, by mass percentage, the nano-metal powder is 60%, mixed solvent is 40%, the viscosity of mixed solvent is 2000cps, mixed solvent is: ethanol 10wt%, ethylene glycol 25wt%, glycerol 10wt%, diethylene glycol 15wt%, monomethyl ether 10wt%, Ethyl acetate 5wt%, 2-methoxypropanol acetate 10wt%, acrylic resin 10wt%, silane coupling agent 5wt%.

The prepared nano-silver conductive ink is shown in Figure 1(b) inset, showing that the obtained ink is purple,

Example 5

The method for preparing conductive ink with the nano-metal powder of the above-mentioned embodiment 2 comprises the following steps: ultrasonically dispersing the nano-metal powder in a mixed solvent to obtain a nano-metal conductive ink, wherein, by mass percentage, the nano-metal powder is 20%, The mixed solvent is 80%, the viscosity of the mixed solvent is 20cps, and the mixed solvent is: ethanol 15wt%, ethylene glycol 20wt%, glycerin 13wt%, diethylene glycol 25wt%, monomethyl ether 10wt%, acrylic resin 10wt %, silane coupling agent 5wt%, and the balance is deionized water.

The as-prepared nanosilver conductive ink is shown in the inset of Fig. 2(b), showing that the obtained ink is dark yellow-brown.

Example 6

The method for preparing conductive ink with the nano-metal powder of the above-mentioned embodiment 3 comprises the following steps: ultrasonically dispersing the nano-metal powder in a mixed solvent to obtain a nano-metal conductive ink, wherein, by mass percentage, the nano-metal powder is 60%, Mixed solvent is 40%, and the viscosity of mixed solvent is 80cps, and mixed solvent is: ethanol 8wt%, ethylene glycol 20wt%, glycerol 10wt%, diethylene glycol 25wt%, monomethyl ether 10wt%, ethyl acetate 5wt%, 2-methoxy propanol acetate 10wt%, acrylic resin 5wt%, silane coupling agent 2wt%, and the balance is deionized water.

The as-prepared nano-copper conductive ink is shown in the inset of Fig. 3(b), showing that the obtained ink is purple-red.

Example 7

The electronic device is prepared with the conductive ink of Example 4, and the conductive ink is coated on the substrate of the electronic device by the brushing method, and the infrared sintering is carried out for 6 minutes, and the power of the infrared sintering is 1, 3, 5, 8, 10 and 13W respectively , where, when the infrared sintering power is 10W, the measured length of the conductive pattern is L=5cm, the cross-sectional area S=1×10 ^-3 cm ² , the resistance R=0.34Ω, and the resistivity calculation formula is ρ=RS/L , the calculated resistivity ρ=6.8 micro-ohm·cm is about 2.8 times that of pure gold resistivity ρ=2.40 micro-ohm·cm.

The resistivity test in Figure 4 shows that the resistivity of the gold conductive pattern gradually decreases with the increase of the sintering power, and when the sintering power is 10 watts, it shows that the resistivity reaches a stability of about ρ=6.8 micro-ohm·cm.

Example 8

Prepare electronic device with the conductive ink of embodiment 5, adopt Hewlett-Packard 1010 printer, the method for inkjet printing 1,3,6 and 10 times respectively is coated with conductive ink on the flexible photo paper substrate, 90 ℃ of oven temperature sintering 10min, infrared The power of sintering is 4W, wherein, after inkjet printing 10 times, the measured length of the conductive pattern is L=5cm, the cross-sectional area S=1×10 ^-6 cm ² , the resistance R=40Ω, and the resistivity calculation formula is ρ= RS/L, calculated to obtain its resistivity ρ=8 micro-ohm·cm, which is about 5 times of the resistivity of pure silver ρ=1.58 micro-ohm·cm.

The test resistivity is shown in Figure 5, which shows that the resistivity gradually decreases with the increase of the number of spraying, and when spraying for 10 times, it shows that the resistivity reaches a stable value, which is about ρ=8 micro-ohm·cm.

Example 9

Use the conductive ink of Example 6 to prepare electronic devices, use the oil pen writing method to coat the conductive ink on the substrate of the electronic device, and conduct infrared sintering for 1 to 15 minutes. The power of infrared sintering is 5W. The length of the conductive pattern is L=5cm, the cross-sectional area S=1× ^10-6 cm ² , and the resistance R=68Ω. The resistivity calculation formula is ρ=RS/L, and the calculated resistivity ρ=13.6 micro-ohms. cm, which is about 5 times that of pure copper resistivity ρ=1.68 micro-ohm·cm.

The measured resistivity is shown in Figure 6, which shows that the resistivity of the copper conductive pattern gradually decreases with the prolongation of the infrared sintering time. After sintering for 12 minutes, the displayed resistivity reaches a stable level, which is about ρ=13.6 micro-ohm·cm.

The present invention has been described as an example above, and it should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacements that can be made by those skilled in the art without creative labor all fall within the scope of this invention. protection scope of the invention.

Claims (10)

1. A room temperature preparation method of nano metal powder is characterized by comprising the following steps:

1) injecting the solution B into the solution A at room temperature under an ultrasonic state to obtain a mixed solution, wherein the preparation method of the solution A and the solution B is as follows:

solution A: placing an organic protective agent and a reducing agent into deionized water, uniformly dissolving the organic protective agent and the reducing agent into the deionized water, and adjusting the pH value to 7.5-11 after the organic protective agent and the reducing agent are dissolved to obtain a solution A, wherein the organic protective agent is a nonionic surfactant and a cationic/anionic surfactant, and the molar ratio of the nonionic surfactant to the cationic/anionic surfactant is (0.1-2): 1;

solution B: adding metal salt into deionized water, and uniformly dissolving the metal salt in the deionized water to obtain a solution B, wherein the metal salt is copper salt, gold salt or silver salt;

according to the amount of the substances, the ratio of the reducing agent to the organic protective agent to the metal salt is (4-20): (1-5): 1;

2) and adding a washing solvent into the mixed solution, washing by centrifuging, and obtaining a precipitate which is nano metal powder after washing.

2. The room temperature preparation method of claim 1, wherein the concentration of the organic protective agent in deionized water in which the organic protective agent is dissolved is 0.01-1.5 mol/L;

the concentration of the reducing agent in deionized water for dissolving the reducing agent is 0.04-0.6 mol/L;

the nonionic surfactant is polyvinylpyrrolidone, oleic acid, alkylolamide or fatty alcohol-polyoxyethylene ether;

the cationic surfactant is 12/14/16/18 alkyl trimethyl ammonium bromide, ammonium chloride, silicone oil or panthenol;

the anionic surfactant is sodium dodecyl benzene sulfonate, sodium fatty alcohol-polyoxyethylene ether sulfate or sodium dodecyl sulfate.

3. The room temperature preparation method according to claim 2, wherein the reducing agent is a mixture of two or more of sodium hypophosphite, vitamin C, D-ascorbic acid, and glucose;

the pH value is adjusted to 7.5-11 by adding alkaline substances, wherein the alkaline substances are concentrated ammonia water and/or sodium hydroxide.

4. The room temperature preparation method of claim 3, wherein the concentration of the metal salt in the deionized water in which the metal salt is dissolved is 0.01 to 1 mol/L;

the silver salt is one or more of silver nitrate, silver nitrite, silver acetate, silver carbonate, silver phosphate and chitosan silver;

the copper salt is one or a mixture of more than one of copper sulfate pentahydrate, copper chloride and copper nitrate; the gold salt is chloroauric acid and/or gold nitrate.

5. The room temperature preparation method of claim 4, wherein in the step 1), the operation method for uniformly dissolving the organic protective agent and the reducing agent in the deionized water comprises the following steps: continuously stirring for 3-30 minutes, and then carrying out ultrasonic treatment for 3-30 minutes;

in the step 1), the operation method for uniformly dissolving the metal salt in the deionized water comprises the following steps: continuously stirring for 3-30 minutes, and then carrying out ultrasonic treatment for 3-30 minutes;

in the step 2), the ratio of the mixed solution to the washing solvent is 1 (2-5) in parts by volume;

in the step 2), the washing solvent is any one or a mixture of two of ethanol, acetone and deionized water.

6. The method for preparing the conductive ink from the nano metal powder as claimed in claims 1 to 5, which is characterized by comprising the following steps: and ultrasonically dispersing the nano metal powder in a mixed solvent to obtain the nano metal conductive ink, wherein the viscosity of the mixed solvent is 8-10000cps, the nano metal powder accounts for 5-80% by mass percent, and the mixed solvent accounts for 20-95%.

7. The method according to claim 6, wherein the mixed solvent is a mixture of two or more of ethanol, ethylene glycol, glycerol, diethylene glycol, monomethyl ether, ethyl acetate, butyl acetate, methoxy-2 propanol acetate, butyl acetate, acrylic resin, a silane coupling agent, and deionized water.

8. The method according to claim 7, wherein the mixed solvent is, in mass percent: 0-30 wt% of ethanol, 5-30 wt% of ethylene glycol, 3-20 wt% of glycerol, 5-30 wt% of diethylene glycol, 5-20 wt% of monomethyl ether, 0-8 wt% of ethyl acetate, 0-5 wt% of butyl acetate, 0-20 wt% of methoxy-2-propanol acetate, 0-10 wt% of butyl acetate, 0-20 wt% of acrylic resin, 0-5 wt% of a silane coupling agent and the balance of deionized water.

9. The application of the conductive ink obtained by the method of claim 7 or 8 in improving the resistivity of an electronic device is to coat the conductive ink on a substrate of the electronic device, and perform infrared sintering or furnace temperature sintering for 0-15 min to obtain the electronic device with the resistivity 2-8 times that of a pure metal, wherein the infrared sintering power is 0-15W, and the furnace temperature sintering temperature is 25-100 ℃.

10. The use according to claim 9, wherein the conductive ink is applied on the substrate of the electronic device by an inkjet, a pen writing or a brush application method, and when the application method is the inkjet, the mixed solvent has a viscosity of 8 to 20 cps; when the coating method is oil pen writing, the viscosity of the mixed solvent is 20-1000 cps; when the coating method is brushing, the viscosity of the mixed solvent is 1000-10000 cps.