Urea-involved silver nanoparticles, and preparation method and application thereof

Abstract

This invention discloses a urea-based silver nanoparticle, its preparation method, and its application. The preparation method includes the following steps: adding urea and silver nitrate to ethylene glycol, stirring at room temperature until dissolved, and then subjecting to ultrasonic water bath treatment to obtain solution A; adding polyvinylpyrrolidone to ethylene glycol, stirring at room temperature until dissolved to obtain solution B; preheating and maintaining the temperature of solution B, and then dripping solution A into the preheated solution B while stirring, allowing it to stand and maintain the temperature to obtain a silver nanoparticle mother liquor; performing solid-liquid separation on the silver nanoparticle mother liquor, and purifying the separated precipitate to obtain silver nanoparticles. This invention uses urea instead of halide ions as a control agent, resulting in silver nanoparticles with good dispersibility, high purity, and uniform particle size. Furthermore, the preparation method is simple to operate, uses widely available and low-cost raw materials, and the experimental equipment and conditions are easy to implement and have good reproducibility.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial synthesis technology, specifically relating to a urea-involved silver nanoparticle, its preparation method, and its application. Background Technology

[0002] With the development of new-generation information industry technology and the iteration of photovoltaic industry technology, the requirements for silver powder (silver nanoparticles) are becoming increasingly higher, especially the demand for silver powder with high conductivity and low temperature curing is becoming more and more urgent. The preparation of silver nanoparticles with uniform particle size and high dispersion is the prerequisite and key to improving the performance and adaptability of silver powder.

[0003] Furthermore, among existing technologies, the liquid-phase reduction method in chemical processes is widely used in the synthesis of silver nanoparticles due to its ease of operation, good reproducibility, and low requirements for equipment and experimental conditions. In recent years, most researchers have used NaBH4, ascorbic acid, and other reducing agents to prepare silver nanoparticles. However, the synthesized silver nanoparticles have problems such as easy agglomeration and uneven particle size, and the cost is relatively high. After many years of development, the application and promotion of these methods have become more difficult. Therefore, developing a process method for producing silver powder (silver nanoparticles) that can improve the dispersion of nanoparticles and solve the problems of uneven particle size and high production costs is one of the main problems that researchers are currently working on. Summary of the Invention

[0004] In view of this, the main objective of the present invention is to provide a method for preparing silver nanoparticles involving urea, which greatly reduces the time and cost of preparing silver nanoparticles in the prior art, improves the dispersion of nanoparticles, and solves the problem of uneven particle size.

[0005] Another objective of this invention is to provide silver nanoparticles obtained using the above method.

[0006] Another objective of this invention is to provide an application of silver nanoparticles in the preparation of silver paste.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: a method for preparing urea-involved silver nanoparticles, the method specifically including the following steps:

[0008] Step 1: Add urea and silver nitrate to ethylene glycol and stir at room temperature until dissolved. Then, perform ultrasonic water bath treatment to obtain solution A. Add polyvinylpyrrolidone to ethylene glycol and stir at room temperature until dissolved to obtain solution B.

[0009] Step 2: Preheat and keep the solution B at a constant temperature, then add the solution A dropwise into the preheated solution B, stir, and let it stand at a constant temperature to obtain the silver nanoparticle mother liquor;

[0010] Step 3: Perform solid-liquid separation on the mother liquor containing the silver nanoparticles, and purify the precipitate obtained by separation to obtain silver nanoparticles.

[0011] Preferably, in step 1, the concentration of urea is 0.5–5.0 g / L; the concentration of silver nitrate is 3.0–10.0 g / L; and the concentration of polyvinylpyrrolidone is 0.5–5.0 g / L.

[0012] Preferably, in step 2, the solution B is preheated to 120-190°C, the heat preservation time is 20-50 minutes, and the standing heat preservation time is 0.5-1.5 hours.

[0013] Preferably, in step 2, the dripping rate of solution A is 0.1 to 0.5 mL / min, and the dripping time is 8 to 12 min.

[0014] Preferably, the stirring rate in steps 1 and 2 is 200–500 rpm / min.

[0015] Preferably, in step 2, the volume ratio of solution A to solution B is 1.5 to 2.5:1.

[0016] Preferably, the specific method of step 3 is as follows:

[0017] Step 3-1: Add deionized water to the silver nanoparticle mother liquor and stir until homogeneous to obtain mixture A; perform solid-liquid separation on mixture A to obtain precipitate W1;

[0018] Step 3-2: Add ethanol to the precipitate W1 and sonicate until it is evenly dispersed to obtain mixture B; perform solid-liquid separation on mixture B to obtain precipitate W2;

[0019] Step 3-3: Repeat step 3-2 3-5 times until the conductivity of the washing filtrate is less than 10 μS / cm, thus obtaining silver nanoparticles.

[0020] Preferably, in step 3-3, the specific washing process is as follows: first wash with deionized water, then wash thoroughly with ethanol 3-5 times.

[0021] The technical solution of the present invention is as follows: a silver nanoparticle is prepared by the above method, and the average diameter of the silver nanoparticle is 130-210 nm.

[0022] Another technical solution of the present invention is implemented as follows: the application of silver nanoparticles in the preparation of silver paste. A coarse paste is prepared by mixing silver powder, resin, and various solvents, then ground using a three-roll mill, followed by screen printing and sintering. The measured volume resistivity is 7.8 × 10⁻⁶. -6Ω·cm.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The method of this invention uses urea instead of halide ions as a control agent, which results in silver nanoparticles with good dispersibility, high purity, and uniform particle size. At the same time, the preparation method of this invention is simple to operate, the raw materials are widely available and the cost is low, the experimental equipment and conditions are easy to implement, and the repeatability is good. Attached Figure Description

[0025] The present invention will now be described in further detail with reference to the accompanying drawings.

[0026] Figure 1 SEM image (a) and particle size distribution diagram (b) of the silver nanoparticles prepared in Example 1 of the present invention;

[0027] Figure 2 The XRD pattern of the silver nanoparticles prepared in Example 1 of this invention;

[0028] Figure 3 SEM image (a) and particle size distribution diagram (b) of silver nanoparticles prepared in Example 2 of the present invention;

[0029] Figure 4 SEM image (a) and particle size distribution diagram (b) of the silver nanoparticles prepared in Example 3 of the present invention;

[0030] Figure 5 SEM image (a) and particle size distribution diagram (b) of the silver nanoparticles prepared in Example 4 of this invention;

[0031] Figure 6 SEM image (a) and particle size distribution diagram (b) of the silver nanowires prepared in Comparative Example 1 of this invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] The instrument information used in the embodiments of this invention is as follows:

[0034] The electronic balance was a ME104E manufactured by Mettler Toledo Instruments Ltd.; the magnetic stirrer was an IKARCT basic manufactured by IKARCT (Guangzhou) Instrument Equipment Co., Ltd.; the benchtop high-speed centrifuge was a TG16-WS manufactured by Hunan Xiangyi Laboratory Instrument Development Co., Ltd.; the ultrasonic cleaner was a KQ5200 manufactured by Kunshan Ultrasonic Instrument Co., Ltd.; and the scanning electron microscope was a SU8010 manufactured by HITACHI. The elemental composition of the samples was analyzed using energy-dispersive X-ray spectroscopy (EDS).

[0035] The reagent information used in this invention is as follows:

[0036] Urea, molecular formula CO(NH2)2, manufactured by Aladdin Reagent; reagent purity AR; silver nitrate, molecular formula AgNO3, reagent purity AR≥99.8%, manufactured by Tianjin Damao Chemical Reagent Factory; ethylene glycol (EG), molecular formula (CH2OH)2, reagent purity AR≥98.5%, manufactured by Tianjin Damao Chemical Reagent Factory; polyvinylpyrrolidone (PVP), molecular formula (C6H9NO). n The reagent purity is AR, and the manufacturer is Aladdin Reagent; anhydrous ethanol, with the molecular formula C2H5OH, has a reagent purity of AR≥99.7%, and the manufacturer is Tianjin Damao Chemical Reagent Factory.

[0037] This invention provides a method for preparing urea-based silver nanoparticles, which specifically includes the following steps:

[0038] Step 1: Add urea and silver nitrate to ethylene glycol, stir at room temperature until dissolved, and then perform ultrasonic water bath treatment to obtain solution A. Add polyvinylpyrrolidone to ethylene glycol, stir at room temperature until dissolved to obtain solution B. The concentration of urea is 0.5-5.0 g / L; the concentration of silver nitrate is 3.0-10.0 g / L; and the concentration of polyvinylpyrrolidone is 0.5-5.0 g / L.

[0039] Step 2: Preheat solution B to 120–190°C and maintain this temperature for 20–50 min. Then, add solution A dropwise to the preheated solution B at a rate of 0.1–0.5 mL / min, completing the dropwise addition in 8–12 min. Maintain a stirring rate of 200–500 rpm / min during the dropwise addition. Allow the solution to stand for 0.5–1.5 h to obtain a silver nanoparticle mother liquor. The volume ratio of solution A to solution B is 1.5–2.5:1.

[0040] Step 3: Perform solid-liquid separation on the mother liquor containing the silver nanoparticles, and purify the separated precipitate to obtain silver nanoparticles. The specific method is as follows:

[0041] Step 3-1: Add deionized water to the silver nanoparticle mother liquor and stir until homogeneous to obtain mixture A; perform solid-liquid separation on mixture A to obtain precipitate W1;

[0042] Step 3-2: Add ethanol to the precipitate W1 and sonicate until it is evenly dispersed to obtain mixture B; perform solid-liquid separation on mixture B to obtain precipitate W2;

[0043] Step 3-3: Repeat step 3-2 3-5 times to make the conductivity of the washing filtrate less than 10 μS / cm, and obtain silver nanoparticles; the specific washing process is as follows: first wash with deionized water, and then wash thoroughly with ethanol 3-5 times.

[0044] This embodiment also provides a silver nanoparticle, which is prepared by the above method, and the average diameter of the silver nanoparticle is 130-210 nm.

[0045] The following are specific examples.

[0046] Example 1

[0047] Step 1: Solution preparation: Place 10.0 mg of urea and 20.0 mg of silver nitrate together in 4.0 mL of ethylene glycol and stir to dissolve at room temperature for 30 min to obtain complex solution A. Sonicate solution A for 10 min and place it in an ice bath until the dripping stage. Place 0.001 g of PVP in 2.0 mL of ethylene glycol and stir to dissolve at room temperature for 30 min to obtain solution B.

[0048] Step 2, High-temperature reaction: Transfer solution B to a 20 mL single-necked flask, preheat to 150 °C and maintain the temperature for 30 min. Use a microfluidic peristaltic pump to drip solution A into the preheated solution B at a rate of 0.2 mL / min, while maintaining the magnetic stirrer speed at 300 rpm / min. After the dripping is completed, seal the single-necked flask and let it stand for 1.0 h to obtain the AgNPs mother liquor; wherein the volume ratio of solution A to solution B is 2:1.

[0049] Step 3: Purify and separate the AgNPs mother liquor: Purification is performed according to the following method:

[0050] Step 3-1: Transfer the prepared AgNPs mother liquor to a 50.00 mL centrifuge tube, add deionized water equivalent to 3 times the volume of the AgNPs mother liquor, stir evenly to obtain mixture A, centrifuge at 4000 rpm for 10 min, remove the supernatant to obtain precipitate W1.

[0051] Step 3-2: Add ethanol equivalent to 3 times the volume of W1 to W1, and sonicate for 10 minutes to disperse it evenly, obtaining mixture B.

[0052] Step 3-3: Repeat step 3-2 three times, ensuring the conductivity of the washing filtrate is less than 10 μS / cm, to obtain purified silver nanoparticles.

[0053] The purified silver nanoparticles (AgNPs) were dispersed in a small amount of ethanol and characterized by scanning electron microscopy. The results are shown in [reference needed]. Figure 1 It can be seen that the AgNPs prepared in Example 1 have a high purity of 92% and a size of approximately 145 nm.

[0054] Example 2

[0055] Step 1: Solution preparation: Place 8.0 mg of urea and 20.0 mg of silver nitrate in 4.0 mL of ethylene glycol and stir to dissolve for 30 min at room temperature to obtain complex solution A. Sonicate solution A for 10 min and place it in an ice bath until the dripping stage. Place 0.005 g of PVP in 2.0 mL of ethylene glycol and stir to dissolve for 30 min at room temperature to obtain solution B.

[0056] Step 2, High-temperature reaction: Transfer solution B to a 20 mL single-necked flask, preheat to 170 °C and keep warm for 30 min. Use a microfluidic peristaltic pump to drip solution A into the preheated solution B at a rate of 0.2 mL / min while stirring. The magnetic stirrer speed is 300 rpm / min. After the dripping is completed, seal the single-necked flask and let it stand for 1.0 h to obtain AgNPs mother liquor; wherein the volume ratio of solution A to solution B is 2:1.

[0057] Step 3: Purify and separate the AgNPs mother liquor: Purification is performed according to the following method:

[0058] Step 3-1: Transfer the prepared AgNPs mother liquor to a 50.00 mL centrifuge tube, add deionized water equivalent to 3 times the volume of the AgNPs mother liquor, stir evenly to obtain mixture A, centrifuge at 4000 rpm for 10 min, remove the supernatant to obtain precipitate W1.

[0059] Step 3-2: Add ethanol equivalent to 3 times the volume of W1 to W1, and sonicate for 10 minutes to disperse it evenly, obtaining mixture B.

[0060] Step 3-3: Repeat step 3-2 three times, ensuring the conductivity of the washing filtrate is less than 10 μS / cm, to obtain purified silver nanoparticles.

[0061] The purified silver nanoparticles (AgNPs) were dispersed in a small amount of ethanol and characterized by scanning electron microscopy. The results are shown in [reference needed]. Figure 2 It can be seen that the average diameter of the AgNPs prepared in Example 2 is 135 nm.

[0062] Example 3

[0063] Step 1: Solution preparation: Place 6.0 mg of urea and 20.0 mg of silver nitrate in 4.0 mL of ethylene glycol and stir to dissolve for 30 min at room temperature to obtain complex solution A. Sonicate solution A for 10 min and place it in an ice bath until the dripping stage. Place 0.005 g of PVP in 2.0 mL of ethylene glycol and stir to dissolve for 30 min at room temperature to obtain solution B.

[0064] Step 2, High-temperature reaction: Transfer solution B to a 20 mL single-necked flask, preheat to 140 °C and keep warm for 30 min. Use a microfluidic peristaltic pump to drip solution A into the preheated solution B at a drip rate of 0.2 mL / min while stirring. The magnetic stirrer speed is 300 rpm / min. After the dripping is completed, seal the single-necked flask and let it stand for 1.0 h to obtain AgNPs mother liquor; wherein the volume ratio of solution A to solution B is 2:1.

[0065] Step 3: Purify and separate the AgNPs mother liquor: Purification is performed according to the following method:

[0066] Step 3-1: Transfer the prepared AgNPs mother liquor to a 50.00 mL centrifuge tube, add deionized water equivalent to 3 times the volume of the AgNPs mother liquor, stir evenly to obtain mixture A, centrifuge at 4000 rpm for 10 min, remove the supernatant to obtain precipitate W1.

[0067] Step 3-2: Add ethanol equivalent to 3 times the volume of W1 to W1, and sonicate for 10 minutes to disperse it evenly, obtaining mixture B.

[0068] Step 3-3: Repeat step 3-2 three times, ensuring the conductivity of the washing filtrate is less than 10 μS / cm, to obtain purified silver nanoparticles.

[0069] The purified silver nanoparticles (AgNPs) were dispersed in a small amount of ethanol and characterized by scanning electron microscopy. The results are shown in [reference needed]. Figure 3 It can be seen that the average particle size of AgNPs prepared in Example 3 is 175 nm, and the mass fraction of AgNPs reaches 87%.

[0070] Example 4

[0071] Step 1: Solution preparation: Place 4.0 mg of urea and 20.0 mg of silver nitrate together in 4.0 mL of ethylene glycol and stir to dissolve for 30 min at room temperature to obtain complex solution A. Sonicate solution A for 10 min and place it in an ice bath until the dripping stage. Place 0.005 g of PVP in 2.0 mL of ethylene glycol and stir to dissolve for 30 min at room temperature to obtain solution B.

[0072] Step 2, High-temperature reaction: Transfer solution B to a 20 mL single-necked flask, preheat to 160 °C and keep warm for 30 min. Use a microfluidic peristaltic pump to drip solution A into the preheated solution B at a rate of 0.10 mL / min while stirring. The magnetic stirrer speed is 300 rpm / min. After the dripping is completed, seal the single-necked flask and let it stand for 1.0 h to obtain AgNPs mother liquor; wherein the volume ratio of solution A to solution B is 2:1.

[0073] Step 3: Purify and separate the AgNPs mother liquor: Purification is performed according to the following method:

[0074] Step 3-1: Transfer the prepared AgNPs mother liquor to a 50.00 mL centrifuge tube, add deionized water equivalent to 3 times the volume of the AgNPs mother liquor, stir evenly to obtain mixture A, centrifuge at 4000 rpm for 10 min, remove the supernatant to obtain precipitate W1.

[0075] Step 3-2: Add ethanol equivalent to 3 times the volume of W1 to W1, and sonicate for 10 minutes to disperse it evenly, obtaining mixture B.

[0076] Step 3-3: Repeat step 3-2 three times, ensuring the conductivity of the washing filtrate is less than 10 μS / cm, to obtain purified silver nanoparticles.

[0077] The purified silver nanoparticles (AgNPs) were dispersed in a small amount of ethanol and characterized by scanning electron microscopy. The results are shown in [reference needed]. Figure 4 As can be seen from the figure, the average particle size of the AgNPs prepared in Example 4 is 205 nm. The AgNPs synthesized under these conditions are mostly cubic blocks, with a small number of long rods and triangular pyramids.

[0078] Comparative Example 1

[0079] The ratio of urea, silver nitrate, and PVP is adjusted to exceed the ratio described in this patent.

[0080] Step 1: Solution preparation: Place 10.0 mg of urea and 25.5 mg of silver nitrate in 1.5 mL of ethylene glycol and stir to dissolve for 30 min at room temperature to obtain complex solution A. Sonicate solution A for 10 min and place it in an ice bath until the dripping stage. Place 0.001 g of PVP in 4 mL of ethylene glycol and stir to dissolve for 30 min at room temperature to prepare solution B.

[0081] Step 2, High-temperature reaction: Transfer solution B to a 20 mL single-necked flask, preheat to 150 °C and keep warm for 30 min. Use a syringe pump to drip solution A into the preheated solution B at a rate of 0.20 mL / min while maintaining magnetic stirring at 300 rpm / min. After the dripping is complete, seal the single-necked flask and let it stand for 1.0 h to obtain AgNPs mother liquor; wherein the volume ratio of solution A to solution B is 1:1.

[0082] Step 3, Purify and separate the mother liquor: Purification is carried out according to the following method:

[0083] Step 3-1: Transfer the prepared mother liquor to a 50.00 mL centrifuge tube, add ethanol equivalent to 3 times the volume of the mother liquor, sonicate for 10 min to disperse it evenly, and obtain mixture A. Centrifuge at 4000 rpm for 10 min, remove the supernatant, and obtain precipitate W1.

[0084] Step 3-2: Add ethanol equivalent to 3 times the volume of W1 to W1, and sonicate for 10 minutes to disperse it evenly, obtaining mixture B.

[0085] Step 3-3: Repeat step 3-2 three times to obtain the purified sample.

[0086] The purified sample was dispersed in a small amount of ethanol and characterized by scanning electron microscopy. The results are shown in [reference needed]. Figure 5 As can be seen from the figure, the silver nanowires (AgNWs) with high purity obtained in this comparative example have an average diameter of 87.45 nm and a length of 32 μm.

[0087] In summary, by using urea instead of halide ions as a control agent and strictly controlling the amounts of urea, silver nitrate, and polyvinylpyrrolidone, silver nanoparticles (AgNPs) with uniform particle size and high dispersion can be prepared. Conversely, AgNWs or other products are easily obtained.

[0088] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing silver nanoparticles involving urea, characterized in that, The method specifically includes the following steps: Step 1: Add urea and silver nitrate to ethylene glycol, stir at room temperature until dissolved, then perform ultrasonic water bath treatment to obtain complex solution A. Sonicate complex solution A for 10 minutes and place in an ice bath until the dripping stage. Add polyvinylpyrrolidone to ethylene glycol, stir at room temperature until dissolved to obtain solution B. The concentration of urea is 0.5–5.0 g / L; the concentration of silver nitrate is 3.0–10.0 g / L; and the concentration of polyvinylpyrrolidone is 0.5–5.0 g / L. Step 2: Preheat solution B to 120–190°C, then maintain the temperature for 20–50 min. Add the complexing solution A to solution B at a rate of 0.1–0.5 mL / min, stirring and allowing to stand for 0.5–1.5 h to obtain a silver nanoparticle mother liquor. The volume ratio of the complexing solution A to solution B is 1–3:

1. Step 3: Perform solid-liquid separation on the mother liquor of the silver nanoparticles, and purify the separated precipitate to obtain silver nanoparticles; the average diameter of the silver nanoparticles is 130-210 nm.

2. The method for preparing urea-involved silver nanoparticles according to claim 1, characterized in that, In step 2, the infusion time is 8 to 12 minutes.

3. The method for preparing urea-involved silver nanoparticles according to claim 1 or 2, characterized in that, The stirring rate in steps 1 and 2 is 200–500 rpm / min.

4. The method for preparing urea-involved silver nanoparticles according to claim 1, characterized in that, The specific method for step 3 is as follows: Step 3-1: Add deionized water to the silver nanoparticle mother liquor and stir until homogeneous to obtain mixture A; perform solid-liquid separation on mixture A to obtain precipitate W1; Step 3-2: Add ethanol to the precipitate W1 and sonicate until it is evenly dispersed to obtain mixture B; perform solid-liquid separation on mixture B to obtain precipitate W2; Step 3-3: Repeat step 3-2 3-5 times until the conductivity of the washing filtrate is less than 10 μS / cm, thus obtaining silver nanoparticles.

5. The method for preparing urea-involved silver nanoparticles according to claim 4, characterized in that, In step 3-3, the specific washing process is as follows: first wash with deionized water, then wash thoroughly with ethanol 3-5 times, and the conductivity of the resulting washing filtrate is less than 10 μS / cm.

Images