A nano-silver particle for conductive ink in electronic 3D printing and its preparation method

Abstract

This invention discloses a method for preparing nano-silver particles for conductive inks used in electronic 3D printing. The method employs diethanolamine for surface ligand exchange to modify the surface of dispersant-protected nano-silver particles. The nano-silver particles prepared by this method have a particle size of 20nm–80nm, a uniform particle size distribution, and a near-spherical morphology. This invention utilizes diethanolamine to perform surface ligand exchange with the dispersant attached to the surface of the nano-silver particles, effectively removing the dispersant and obtaining near-spherical nano-silver particles. This eliminates the need for subsequent complex washing processes, effectively ensuring the conductivity of the nano-silver particles. The reaction is mild, the operation is simple, and it is suitable for the field of conductive inks for electronic 3D printing.

Description

Technical Field

[0001] This invention relates to the field of nano-silver powder preparation technology, specifically to a nano-silver particle for conductive ink in electronic 3D printing and its preparation method. Background Technology

[0002] Electronic 3D printing refers to the technology of fabricating electronic engineering devices from electronically conductive materials using high-precision 3D printing techniques (such as piezoelectric inkjet printing, aerosol jet printing, and electrohydraulic printing). It shows great promise in fields such as information technology, energy storage, flexible wearables, medicine, aerospace, and military applications, and is crucial for supporting the transformation and upgrading of traditional industries. Electronic 3D printing technology can construct material microstructures in situ and achieve microscale control of these structures, making it of significant exploratory value for the development of high-performance electronic engineering devices.

[0003] Conductive ink, as a core material in electronic 3D printing technology, is one of the key factors in its development. Nanomaterials, due to their excellent electrical properties, have become highly sought-after functional materials for conductive inks. Among them, nano-silver materials, with their superior conductivity, stable oxidation resistance, and relatively low manufacturing cost, demonstrate significant research value and application prospects.

[0004] The silver nanoparticles used in the preparation of conductive inks must meet requirements such as small particle size (<100nm), good chemical stability, and strong dispersibility to ensure good conductivity and printing quality. Liquid-phase chemical reduction is a common method for preparing silver nanoparticles, enabling the stable preparation of small-sized (<100nm) particles. This method typically requires the addition of a protective agent (such as polyvinylpyrrolidone, PVP) to achieve uniform dispersion of the silver nanoparticles. However, PVP adheres to the surface of the silver nanoparticles and is difficult to remove, usually requiring multiple washes using methods such as high-speed shaking, heating, and pH adjustment to partially remove it. This significantly affects the conductivity of the silver nanoparticles, limiting their application in conductive inks. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a method for preparing nano-silver particles for conductive inks in electronic 3D printing. This method uses diethanolamine to exchange surface ligands with the dispersant attached to the surface of the nano-silver particles, effectively removing the dispersant and obtaining nano-silver particles with a near-spherical morphology. This eliminates the need for complex subsequent washing processes, effectively ensuring the conductivity of the nano-silver particles. The reaction is mild and the operation is simple, solving the problem that existing methods such as high-speed oscillation, heating, and pH adjustment affect the conductivity of nano-silver particles during washing.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing nano-silver particles for conductive ink for electronic 3D printing, characterized in that diethanolamine is used for surface ligand exchange, and the surface of the nano-silver particles protected by the dispersant is modified to prepare nano-silver particles for conductive ink for electronic 3D printing.

[0007] The above-mentioned method for preparing nano-silver particles for conductive ink in electronic 3D printing is characterized by employing a liquid-phase chemical reduction method, specifically including the following steps:

[0008] Step 1: Dissolve silver nitrate in deionized water to obtain a silver nitrate aqueous solution, and then add acetonitrile to the silver nitrate aqueous solution to obtain a silver solution;

[0009] Step 2: Dissolve the dispersant and reducing agent in deionized water to obtain a dispersant solution and a reducing agent solution, respectively.

[0010] Step 3: Mix the silver solution obtained in Step 1 with the dispersant solution obtained in Step 2 and stir until homogeneous. Then heat to the reaction temperature and add the reducing agent solution obtained in Step 2 dropwise at the reaction temperature. After the addition is complete, continue the reaction at room temperature to obtain a solution of nano-silver particles.

[0011] Step 4: Centrifuge and concentrate the nano-silver particle solution obtained in Step 3, and then wash it with deionized water to obtain nano-silver concentrate.

[0012] Step 5: Disperse the concentrated nano-silver solution obtained in Step 4 in deionized water, then add diethanolamine and stir to react. After centrifugation and concentration, wash with deionized water. Repeat the dispersion, stirring, centrifugation and concentration and washing process. Finally, wash with anhydrous ethanol and concentrate to obtain nano-silver particles for conductive inks for electronic 3D printing.

[0013] The method for preparing nano-silver particles for conductive ink in electronic 3D printing, as described above, is characterized in that the concentration of the silver nitrate aqueous solution in step one is 0.1 mol·L⁻¹. -1 The volume ratio of water to acetonitrile in the silver solution is 1:0.5–2. By controlling the volume ratio of water to acetonitrile in the silver solution, the concentration of the silver solution system is adjusted, thereby controlling the subsequent reaction rate.

[0014] The above-mentioned method for preparing nano-silver particles for conductive ink in electronic 3D printing is characterized in that the dispersant in step two is polyvinylpyrrolidone (PVP) or hexadecyltrimethylammonium bromide (CTAB), and the molecular weight of polyvinylpyrrolidone (PVP) is 40,000.

[0015] The above-mentioned method for preparing nano-silver particles for conductive ink in electronic 3D printing is characterized in that the reducing agent in step two is ascorbic acid, hydrazine hydrate, sodium borohydride, ferrous sulfate, or sodium sulfite.

[0016] The method for preparing nano-silver particles for conductive ink in electronic 3D printing, as described above, is characterized in that: the stirring speed in step three is 300 rpm to 600 rpm; the dropwise addition is performed using a dropping funnel, and the dropping rate is controlled so that the dropping time is not less than 20 minutes; the reaction temperature is 0 to 50°C, the ambient temperature is 10°C to 25°C, and the reaction continues at ambient temperature for not less than 40 minutes. By controlling the dropping rate, reaction temperature, and reaction time, the reaction rate is controlled, ensuring complete reaction.

[0017] The method for preparing nano-silver particles for conductive ink in electronic 3D printing is characterized in that the centrifugal concentration in steps four and five is performed at a speed of 10,000 rpm to 14,000 rpm for 8 minutes, and the centrifugal concentration is repeated three times.

[0018] The method for preparing nano-silver particles for conductive ink in electronic 3D printing, as described above, is characterized in that the concentration of the nano-silver solution formed by dispersing the nano-silver concentrate in deionized water in step five is 0.1 mol·L⁻¹. -1 The volume ratio of the diethanolamine to the dispersed silver nanoparticle solution is 1:20.

[0019] Meanwhile, this invention also discloses a type of silver nanoparticle for conductive ink in electronic 3D printing. The silver nanoparticle, prepared by the above-described method, has a particle size of 20 nm to 80 nm, a uniform particle size distribution, and a near-spherical morphology. Piezoelectric inkjet printing and aerosol jet printing technologies generally require silver nanoparticles with a particle size below 100 nm, and a near-spherical shape is more conducive to conductivity than a spherical shape. Therefore, the silver nanoparticles prepared by this invention meet the usage requirements of these fields in terms of particle size, morphology, and distribution.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. This invention uses diethanolamine to exchange surface ligands with the dispersant attached to the surface of silver nanoparticles, effectively removing the dispersant and modifying the silver nanoparticles. This eliminates the need for subsequent complex washing processes, avoids the adverse effects of post-washing, and effectively ensures the conductivity of the silver nanoparticles, making them suitable for conductive inks in electronic 3D printing.

[0022] 2. The silver nanoparticles prepared by this invention are spherical nanoparticles, and the particle size of the silver nanoparticles can be controlled to 20nm to 80nm by controlling the reaction temperature. The reaction is mild, the operation is simple, and it is suitable for widespread application.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 This is a process flow diagram for preparing the nano-silver particles of the present invention.

[0025] Figure 2 This is a process flow diagram of surface ligand exchange using diethanolamine in this invention.

[0026] Figure 3 This is a scanning electron microscope image of the silver nanoparticles prepared in Example 1 of the present invention.

[0027] Figure 4 This is a low-magnification transmission electron microscope image of the silver nanoparticles prepared in Example 1 of the present invention.

[0028] Figure 5 This is a high-magnification transmission electron microscope image of the silver nanoparticles prepared in Example 1 of the present invention.

[0029] Figure 6 The image shows the X-ray diffraction pattern of the silver nanoparticles prepared in Example 1 of this invention.

[0030] Figure 7 This is a zeta potential diagram of the nano-silver solution before and after the reaction with diethanolamine in Example 1 of the present invention.

[0031] Figure 8 This is a scanning electron microscope image of the silver nanoparticles prepared in Example 2 of the present invention.

[0032] Figure 9 This is a high-resolution transmission electron microscope image of the silver nanoparticles prepared in Example 3 of the present invention.

[0033] Figure 10 This is a high-resolution transmission electron microscope image of the silver nanoparticles prepared in Example 4 of the present invention. Detailed Implementation

[0034] The deionized water used in Examples 1 to 4 of this invention all had a conductivity of less than 2 μS·cm. -1 .

[0035] Example 1

[0036] like Figure 1 As shown, this embodiment uses a liquid-phase chemical reduction method for preparation, and the specific process includes the following steps:

[0037] Step 1: Dissolve 1.7g of silver nitrate in 100mL of deionized water to obtain a silver nitrate aqueous solution. Then add 50mL of acetonitrile to the silver nitrate aqueous solution to obtain a silver solution.

[0038] Step 2: Dissolve 2.5g of polyvinylpyrrolidone (PVP) with a molecular weight of 40,000 in 50mL of deionized water to obtain a 5% dispersant solution; dissolve 1.76g of ascorbic acid in 100mL of deionized water to obtain a reducing agent solution.

[0039] Step 3: Mix the silver solution obtained in Step 1 with the dispersant solution obtained in Step 2 and stir evenly at 300 rpm to 600 rpm. Then heat to the reaction temperature of 25°C. At the reaction temperature of 25°C, add the reducing agent solution obtained in Step 2 dropwise using a dropping funnel. Control the dropping rate during the dropping process so that the dropping time is not less than 20 min. After the dropping is completed, continue the reaction at room temperature of 10°C to 25°C for 40 min to obtain a solution of nano-silver particles.

[0040] Step 4: Centrifuge the nano-silver particle solution obtained in Step 3 at a speed of 11000 rpm to 14000 rpm for 8 minutes. Then wash with deionized water. Repeat the operation 3 times to obtain nano-silver concentrate.

[0041] Step 5: Disperse the concentrated nano-silver solution obtained in Step 4 in 100 mL of deionized water to form a concentration of 0.1 mol·L⁻¹. -1 A nano-silver solution was prepared, and then 5 mL of diethanolamine was added and the mixture was stirred for 2 hours. After centrifugation and concentration, the solution was washed with deionized water. The centrifugation speed was 11000 rpm to 14000 rpm for 8 minutes. This dispersion, stirring, centrifugation, and washing process was repeated to ensure complete ligand exchange. Figure 2 As shown, the final product is washed with anhydrous ethanol and concentrated to obtain nano-silver particles for conductive inks used in electronic 3D printing.

[0042] Figure 3 Here is a scanning electron microscope image of the silver nanoparticles prepared in this embodiment. Figure 3 It can be seen that the silver nanoparticles are uniformly dispersed.

[0043] Figure 4 This is a low-magnification transmission electron microscope image of the silver nanoparticles prepared in this embodiment. Figure 4 It can be seen that the morphology of the silver nanoparticles is spherical and uniform.

[0044] Figure 5 This is a high-magnification transmission electron microscope image of the silver nanoparticles prepared in this embodiment. Figure 5It can be seen more intuitively that the size of the silver nanoparticles is 60nm.

[0045] Figure 6 The X-ray diffraction pattern of the silver nanoparticles prepared in this embodiment is shown below. Figure 6 It can be seen that the composition of the nano-silver particles is silver, and the silver powder has been successfully prepared.

[0046] Figure 7 This is a zeta potential diagram of the silver nanoparticle solution before and after the reaction with diethanolamine in this embodiment. Figure 7 It can be seen that the zeta potential of the nano-silver solution after surface ligand exchange with diethanolamine is significantly increased, indicating that the surface potential of the nano-silver particles is increased, the stability of the solution is improved, and the conductivity is enhanced.

[0047] In step two of this embodiment, the dispersant polyvinylpyrrolidone (PVP) can be replaced with hexadecyltrimethylammonium bromide (CTAB), and the reducing agent ascorbic acid can be replaced with hydrazine hydrate, sodium borohydride, ferrous sulfate, or sodium sulfite.

[0048] Example 2

[0049] The difference between this embodiment and Embodiment 1 is that the reaction temperature in step three is 50°C.

[0050] Figure 8 Here is a scanning electron microscope image of the silver nanoparticles prepared in this embodiment. Figure 8 It can be seen that the silver nanoparticles prepared in this embodiment are relatively uniformly dispersed, have a spherical morphology, and all have a size of less than 80 nm.

[0051] Example 3

[0052] The difference between this embodiment and Example 1 is that 100 mL of acetonitrile is added in step one; 1.17 g of ascorbic acid is used in step two; and the reaction temperature is 10 °C in step three.

[0053] Figure 9 This is a high-resolution transmission electron microscope image of the silver nanoparticles prepared in this embodiment. Figure 9 As can be seen, the silver nanoparticles prepared in this embodiment are uniformly dispersed, have a spherical morphology, and a size of 40 nm.

[0054] Example 4

[0055] The difference between this embodiment and Example 1 is that 200 mL of acetonitrile is added in step one; 1.17 g of ascorbic acid is used in step two; and the reaction temperature is 0 °C in step three.

[0056] Figure 10 This is a high-resolution transmission electron microscope image of the silver nanoparticles prepared in this embodiment. Figure 10As can be seen, the silver nanoparticles prepared in this embodiment are uniformly dispersed, have a spherical morphology, and a size of 20 nm.

[0057] Examples 1 to 4 and Figures 5-10 The comparison shows that the reduction rate of silver nitrate is slower due to the decrease in the concentration and temperature of the reaction system, resulting in smaller and more uniform particle size of the prepared silver nanoparticles.

[0058] In summary, this invention discloses a method for preparing nano-silver particles for conductive inks used in electronic 3D printing. The method involves liquid-phase chemical reduction, using diethanolamine for surface ligand exchange, and then surface modification of the PVP-protected nano-silver particles to obtain the final product. The nano-silver particles prepared by this invention are near-spherical with a uniform and controllable particle size distribution and good dispersibility, specifically ranging from 20 nm to 80 nm. Furthermore, the zeta potential indicates good stability, making it suitable for preparing conductive inks for electronic 3D printing. Compared to methods that use complex washing steps to remove PVP from the surface of the nano-silver particles, the preparation method in this invention eliminates these complex washing steps and offers advantages such as mild reaction conditions and simple operation.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing nano-silver particles for conductive ink in electronic 3D printing, characterized in that, Surface ligand exchange with diethanolamine was used to modify the surface of dispersant-protected silver nanoparticles, thus preparing conductive silver nanoparticles for electronic 3D printing ink. The preparation method employs a liquid-phase chemical reduction method, and the specific process includes the following steps: Step 1: Dissolve silver nitrate in deionized water to obtain a silver nitrate aqueous solution, and then add acetonitrile to the silver nitrate aqueous solution to obtain a silver solution; Step 2: Dissolve the dispersant and reducing agent in deionized water to obtain a dispersant solution and a reducing agent solution, respectively. Step 3: Mix the silver solution obtained in Step 1 with the dispersant solution obtained in Step 2 and stir until homogeneous. Then heat to the reaction temperature and add the reducing agent solution obtained in Step 2 dropwise at the reaction temperature. After the addition is complete, continue the reaction at room temperature to obtain a solution of nano-silver particles. Step 4: Centrifuge and concentrate the nano-silver particle solution obtained in Step 3, and then wash it with deionized water to obtain nano-silver concentrate. Step 5: Disperse the concentrated silver nanoparticle solution obtained in Step 4 in deionized water, then add diethanolamine and stir to react. After centrifugation and concentration, wash with deionized water. Repeat the dispersion, stirring, centrifugation, concentration, and washing process. Finally, wash with anhydrous ethanol and concentrate to obtain silver nanoparticles for conductive inks used in electronic 3D printing. The concentration of the silver nanoparticle solution formed after dispersing the concentrated silver nanoparticle solution in deionized water is 0.1 mol·L⁻¹. -1 The volume ratio of the diethanolamine to the dispersed silver nanoparticle solution is 1:

20.

2. The method for preparing nano-silver particles for conductive ink in electronic 3D printing according to claim 1, characterized in that, The concentration of the silver nitrate aqueous solution mentioned in step one is 0.1 mol·L⁻¹. -1 The volume ratio of water to acetonitrile in the silver solution is 1:0.5~2.

3. The method for preparing nano-silver particles for conductive ink in electronic 3D printing according to claim 1, characterized in that, The dispersant mentioned in step two is polyvinylpyrrolidone (PVP) or hexadecyltrimethylammonium bromide (CTAB), and the molecular weight of polyvinylpyrrolidone (PVP) is 40,000.

4. The method for preparing nano-silver particles for conductive ink in electronic 3D printing according to claim 1, characterized in that, The reducing agent mentioned in step two is ascorbic acid, hydrazine hydrate, sodium borohydride, ferrous sulfate, or sodium sulfite.

5. The method for preparing nano-silver particles for conductive ink in electronic 3D printing according to claim 1, characterized in that, The stirring speed in step three is 300 rpm to 600 rpm; the dropwise addition is carried out using a dropping funnel, and the dropping speed is controlled so that the dropping time is not less than 20 minutes; the reaction temperature is 0 to 50°C, the ambient temperature is 10°C to 25°C, and the reaction continues at ambient temperature for not less than 40 minutes.

6. The method for preparing nano-silver particles for conductive ink in electronic 3D printing according to claim 1, characterized in that, In step four, the centrifugation concentration is performed at a speed of 10,000 rpm to 14,000 rpm for 8 minutes, and the centrifugation concentration is repeated 3 times.

7. A type of silver nanoparticle for conductive ink in electronic 3D printing, characterized in that, The conductive ink for electronic 3D printing is prepared by the method described in any one of claims 1 to 6. The nano-silver particles have a particle size of 20 nm to 80 nm, a uniform particle size distribution, and a spherical morphology.

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