CN110355359A - A kind of ultra-fine silver nanowires and preparation method thereof - Google Patents

Abstract

The invention relates to an ultrafine silver nanowire and a preparation method thereof. Based on the typical method of synthesizing silver nanowires with polyols, an organic reducing agent with stronger reducing power is introduced, and the a-hydroxybenzyl radicals produced by it reduce silver ions, which accelerates the reduction rate of the reaction, and It enables the reduction process of silver ions to proceed at a lower reaction temperature, thereby inhibiting the lateral growth of silver nanowires. At the same time, the additive sodium bromide is added during the reaction process to effectively control the growth of the wire diameter, so that the silver nanowires can grow thinner. The method does not require high-pressure conditions and is simple to operate. The average wire diameter of the prepared silver nanowires is about 13nm, and the aspect ratio is greater than 1000.

Description

A kind of ultrafine silver nanowire and preparation method thereof

technical field

The invention belongs to the field of nanomaterial synthesis, and relates to the synthesis of silver nanowires, in particular to an ultrafine silver nanowire and a preparation method thereof.

Background technique

Compared with the traditional ITO film, silver nanowire transparent conductive film has the characteristics of low-cost manufacturing, excellent sheet resistance and visible light transmittance, easy to realize flexibility, sensitive touch, etc., so it has attracted a lot of attention from academic and industrial circles at home and abroad. widespread attention. Silver nanowire transparent conductive film is prepared by coating a flexible substrate with a liquid-coatable colloid, and this colloid is obtained by preparing a solution of silver nanowire solids, so the preparation of silver nanowire materials It is a key step in the preparation of thin films. In recent years, the preparation of silver nanowires has been a hot research topic in the industry. The length and diameter of silver nanowires are important factors affecting the sheet resistance, transmission, haze and other properties of silver nanowire films. The diameter of silver nanowires is proportional to the haze of its film, and the aspect ratio is related to the number of overlapping wires. The larger the aspect ratio is, the less the number of connection points between wires and wires in the film is, which reduces the contact resistance. The longer the length of the silver wire, the thinner the wire diameter, and the larger the aspect ratio, the better the photoelectric performance of the transparent conductive film. However, most of the silver nanowires prepared by the polyol synthesis method have a minimum diameter of about 20nm. The haze value of the silver wire film under this diameter is slightly higher than that of ITO. Therefore, in order to prepare silver with a lower haze value and better photoelectric performance Nanowire films require the synthesis of silver nanowires with smaller diameters.

Contents of the invention

Aiming at the problems existing in the prior art, the invention provides an ultrafine silver nanowire and a preparation method thereof, and the prepared silver nanowire has a smaller diameter.

The present invention is achieved through the following technical solutions:

A method for preparing ultrafine silver nanowires, comprising the following steps:

Step 1, dissolving PVP, potassium bromide and silver nitrate in ethylene glycol, and mixing uniformly to obtain mixed solution A;

Step 2, add organic reducing agent A to mixed solution A, mix evenly to obtain mixed solution B, heat mixed solution B to the reaction temperature under the condition of feeding nitrogen gas, then stop feeding nitrogen gas, react under airtight conditions, and react After the completion, the reaction solution is quenched to obtain the ultrafine silver nanowire puree; wherein, the organic reducing agent A is a compound capable of generating α-hydroxybenzyl radicals.

Preferably, step 1 is specifically: preparing the ethylene glycol solution of PVP, the ethylene glycol solution of potassium bromide and the ethylene glycol solution of silver nitrate respectively; the ethylene glycol solution of PVP is mixed with the ethylene glycol solution of silver nitrate , stirred, and then dropwise added potassium bromide in ethylene glycol solution, stirred to obtain a mixed solution A.

Further, the preparation of the ethylene glycol solution of PVP is specifically: adding PVP to glycol, heating and stirring to dissolve; the preparation of the ethylene glycol solution of potassium bromide is specifically: adding potassium bromide to ethylene glycol, heating and stirring to dissolve; The preparation of the ethylene glycol solution of silver nitrate is as follows: adding silver nitrate into ethylene glycol, placing it under ultrasonic conditions, and dissolving it completely under an ice bath.

Further, the concentration of PVP in the ethylene glycol solution of PVP is 0.005-0.01g/mL, the concentration of potassium bromide in the ethylene glycol solution of potassium bromide is 0.01-0.030g/mL, and the ethylene glycol solution of silver nitrate The concentration of silver nitrate in the medium is 0.01-0.05g/mL; the volume ratio of the ethylene glycol solution of silver nitrate, the ethylene glycol solution of PVP and the ethylene glycol solution of potassium bromide is 1:(2-6):(0.03 -0.3).

Preferably, the organic reducing agent A is at least A sort of.

Preferably, in step 2, the reaction temperature is 140-170°C, and the reaction time is 60-120min.

Preferably, in step 2, heating the mixed solution B to the reaction temperature under the condition of feeding nitrogen gas is specifically: after feeding nitrogen gas for 5-20 minutes, heating the mixed solution B to 140-170°C for 10-30 minutes.

Preferably, the mass ratio of PVP, potassium bromide, silver nitrate and organic reducing agent A is 1:(0.05-1):(0.5-5):(5-15).

The ultrafine silver nanowires prepared by the preparation method.

The diameter of the ultrafine silver nanowire is 12-14nm.

Compared with the prior art, the present invention has the following beneficial technical effects:

In the present invention, an organic reducing agent capable of producing α-hydroxybenzyl radicals is added to the reactant. Since the radicals have non-coupled electrons, the chemical reactivity is higher, and Ag can be quickly reduced by free electrons on the radicals. ⁺ , which increases the reduction rate of the reaction and inhibits the lateral growth of the silver wire; at the same time, the adsorption of Br ^- on the surface of the Ag core helps to control the diameter of the silver wire through electrostatic balance, making the diameter distribution of the prepared silver nanowires narrower, and the average wire The diameter is thinner, reaching about 13nm, and the aspect ratio is greater than 1000. The thinner the diameter of the silver nanowires, the smaller the number of connection points between the wires in the film, which can significantly improve the photoelectric performance of the silver nanowire conductive film. In addition, the preparation method of the present invention is simple, easy to operate, does not require high pressure conditions, and does not require harsh conditions.

Further, the present invention has low reaction temperature and saves energy.

The diameter distribution of the silver nanowires prepared by the invention is narrower, the average wire diameter is thinner, reaching about 13nm, and the aspect ratio is greater than 1000. The thinner the diameter of the silver nanowires, the smaller the number of connection points between the wires in the film, which can significantly improve the photoelectric performance of the silver nanowire conductive film.

Description of drawings

Fig. 1 is the silver nanowire SEM picture that embodiment 1 prepares;

Fig. 2 is the silver nanowire SEM picture that embodiment 2 prepares;

Fig. 3 is the silver nanowire SEM picture that embodiment 3 prepares;

Fig. 4 is the silver nanowire SEM figure prepared by comparative example 1;

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

A method utilizing an organic reducing agent to prepare ultrafine silver nanowires, comprising the steps of:

(1) Preparation of ethylene glycol solution of PVP: Weigh PVP and dissolve it in glycol, put it on a heating plate and stir to dissolve, and the heating temperature is 130° C. to obtain a PVP solution. The molecular weight of the PVP used is between 55,000 and 1,300,000, and the concentration of the prepared solution is 0.005-0.01 g/mL.

(2) Preparation of ethylene glycol solution of sodium bromide: Weigh a certain mass of potassium bromide and dissolve it in ethylene glycol, place it on a heating plate and dissolve it at 130°C with a concentration of 0.01-0.030g/mL to obtain bromide Potassium solution.

(3) Prepare the ethylene glycol solution of AgNO ₃ : take a certain amount of pretreated silver nitrate and dissolve it in ethylene glycol, put it in an ultrasonic wave, and dissolve it in an ice bath for 5-10 minutes to make it completely dissolve. 0.01-0.05g/mL to obtain silver nitrate solution.

(4) Mix the PVP solution configured in step (1) with the silver nitrate solution configured in step (3), stir for 5-20 min at a rotating speed of 500r/min, then add potassium bromide solution dropwise, and stir at a rotating speed of 1000r/min 20-50min to obtain the mixed solution A. Wherein the volume ratio of silver nitrate solution, PVP solution and potassium bromide solution is 1:(2-6):(0.03-0.3); Potassium bromide drop rate is 0.05-0.3mL/s; Mixed solution temperature keeps 20-40 ℃.

(5) Add organic reducing agent A to the mixed solution A, wherein the mass ratio of A to potassium bromide, silver nitrate, and PVP is (5-15): (0.05-1): (0.5-5): 1. 1500r/ After min stirring for 2-10 minutes, stop to obtain mixed solution B. After passing through nitrogen for 5-20 minutes, heat mixed solution B in an oil bath to 140-170°C, heating time 10-30min, nitrogen flow rate 100-300mL/min. Wherein the organic reducing agent A is a class of compounds that can generate a-hydroxybenzyl radicals, including benzoin, 4,4'-dimethoxybenzoin, 4,4'-dimethylbenzoin, 4,4'-dimethoxy At least one of aminobenzoin and 4,4'-dichlorobenzoin.

(6) After the temperature is raised to the set temperature, the ventilation is stopped, and the closed reactor is left to stand for 60-120 minutes to react, and the reaction liquid is quenched to obtain the ultrafine silver nanowire puree.

Example 1

(1) Prepare the ethylene glycol solution of PVP: weigh PVP and dissolve it in glycol, put it on a heating plate and stir to dissolve, the heating temperature is 130°C, and the concentration of the prepared solution is 0.007g/mL. The molecular weight of the PVP used therein is between 55,000 and 1,300,000.

(2) Preparation of ethylene glycol solution of potassium bromide: Weigh a certain mass of potassium bromide and dissolve it in ethylene glycol, put it on a heating plate and dissolve at 130°C with a concentration of 0.02g/mL.

(3) Prepare the ethylene glycol solution of AgNO ₃ : weigh a certain amount of pretreated silver nitrate and dissolve it in ethylene glycol, put it in an ultrasonic wave, and dissolve it in an ice bath for 5 minutes to make it completely dissolve, the concentration is 0.02g /mL.

(4) Mix the PVP solution configured in step (1) with the silver nitrate solution configured in step (3), stir for 5 min at a rotating speed of 500 r/min, then add potassium bromide dropwise, and stir for 30 min at a rotating speed of 1000 r/min. The volumes of the silver nitrate solution and the PVP solution were 45mL and 145mL respectively, the volume of potassium bromide was 4.5mL, the dropping rate was 0.15mL/s, and the temperature of the mixed solution was maintained at 25°C.

(5) After the stirring is completed, add 0.05mol of organic reducing agent A, stop stirring at 1500r/min for 2min, and then feed the nitrogen gas for 10min, then heat the mixed solution in an oil bath to 155°C, the heating time is about 18min, and the nitrogen flow rate is 200mL/ min. Wherein the organic reducing agent A is benzoin.

(6) After the temperature was raised to the set temperature, the ventilation was stopped, and the closed reactor was allowed to stand for 60 minutes to react, and the reaction liquid was quenched to obtain the ultrafine silver nanowire puree.

The silver nanowires obtained in this example have an average diameter of 12.45 nm, an average length of 14.05 um, and an aspect ratio of 1129. The SEM of the silver nanowire morphology is shown in FIG. 1 .

Example 2

(1) Prepare the ethylene glycol solution of PVP: weigh PVP and dissolve it in glycol, put it on a heating plate and stir to dissolve, and the heating temperature is 130°C. The molecular weight of the PVP used is between 55,000 and 1,300,000, and the concentration of the prepared solution is 0.005 g/mL.

(2) Preparation of ethylene glycol solution of potassium bromide: Weigh a certain mass of potassium bromide and dissolve it in ethylene glycol, put it on a heating plate and dissolve at 130°C, the concentration is 0.01g/mL.

( ₃ ) Prepare the ethylene glycol solution of AgNO3: weigh a certain amount of pretreated silver nitrate and dissolve it in ethylene glycol, put it in an ultrasonic wave, and dissolve it in an ice bath for 8 minutes to completely dissolve it, the concentration is 0.01g /mL.

(4) Mix the PVP solution configured in step (1) with the silver nitrate solution configured in step (3), immediately add potassium bromide dropwise, and then increase the rotating speed to 1000r/min and stir for 20min. The volumes of the silver nitrate solution and the PVP solution were 75mL and 150mL respectively, the volume of potassium bromide was 2mL, and the dropping rate was 0.05mL/s; the temperature of the mixed solution was maintained at 20°C.

(5) After stirring, add 0.03 mol of organic reducing agent A, pass nitrogen gas for 5 minutes, heat the mixed solution in an oil bath to 140°C, the heating time is 10 minutes, and the nitrogen flow rate is 100mL/min. Wherein the organic reducing agent A is 4,4'-dimethyl benzoin.

(6) After the temperature was raised to the set temperature, the ventilation was stopped, and the closed reactor was allowed to stand for 90 minutes to react, and the reaction solution was quenched to obtain the ultrafine silver nanowire puree.

The silver nanowires obtained in this example have an average diameter of 12.54nm, an average length of 13.72um, and an aspect ratio of 1094. The SEM of the silver nanowire morphology is shown in FIG. 2 .

Example 3

(1) Prepare the ethylene glycol solution of PVP: weigh PVP and dissolve it in glycol, put it on a heating plate and stir to dissolve, and the heating temperature is 130°C. The molecular weight of the PVP used is between 55,000 and 1,300,000, and the concentration of the prepared solution is 0.01 g/mL.

(2) Preparation of ethylene glycol solution of potassium bromide: Weigh a certain mass of potassium bromide and dissolve it in ethylene glycol, put it on a heating plate and dissolve at 130° C., the concentration is 0.030 g/mL.

(3) Prepare the ethylene glycol solution of AgNO ₃ : weigh a certain amount of pretreated silver nitrate and dissolve it in ethylene glycol, place it in an ultrasonic wave, and dissolve it in an ice bath for 10 minutes to completely dissolve it, the concentration is 0.05g /mL.

(4) Mix the PVP solution configured in step (1) with the silver nitrate solution configured in step (3), stir for 10 min at a rotating speed of 500 r/min, then add potassium bromide dropwise, and stir for 50 min at a rotating speed of 1000 r/min. The volumes of the silver nitrate solution and the PVP solution are 30mL and 180mL, respectively; the volume of potassium bromide is 9mL, and the dropping rate is 0.3mL/s; the temperature of the mixed solution is maintained at 40°C.

(5) After the stirring is finished, add 0.08mol of organic reducing agent A, stop stirring at 1500r/min for 10min, and after passing nitrogen gas for 20min, heat the mixed solution in an oil bath to 170°C, the heating time is 30min, and the nitrogen flow rate is 300mL/min . Wherein the organic reducing agent A is 4,4'-dimethoxy benzoin.

(6) After the temperature was raised to the set temperature, the ventilation was stopped, and the closed reactor was left to stand for 120 minutes to react, and the reaction liquid was quenched to obtain the ultrafine silver nanowire puree.

The silver nanowires obtained in this example have an average diameter of 13.99 nm, an average length of 16.00 um, and an aspect ratio of 1144. The SEM of the silver nanowire morphology is shown in FIG. 3 .

Comparative example 1 (do not add organic reducing agent A)

(1) Prepare the ethylene glycol solution of PVP: weigh PVP and dissolve it in glycol, put it on a heating plate and stir to dissolve, the heating temperature is 130°C, and the concentration of the prepared solution is 0.007g/mL. The molecular weight of the PVP used therein is between 55,000 and 1,300,000.

(2) Preparation of ethylene glycol solution of potassium bromide: Weigh a certain mass of potassium bromide and dissolve it in ethylene glycol, put it on a heating plate and dissolve at 130°C with a concentration of 0.02g/mL.

(3) Prepare the ethylene glycol solution of AgNO ₃ : weigh a certain amount of pretreated silver nitrate and dissolve it in ethylene glycol, put it in an ultrasonic wave, and dissolve it in an ice bath for 5 minutes to make it completely dissolve, the concentration is 0.02g /mL.

(4) Mix the PVP solution configured in step (1) with the silver nitrate solution configured in step (3), stir for 5 min at a rotating speed of 500 r/min, then add potassium bromide dropwise, and stir for 30 min at a rotating speed of 1000 r/min. The volumes of the silver nitrate solution and the PVP solution were 45mL and 145mL respectively, the volume of potassium bromide was 4.5mL, the dropping rate was 0.15mL/s, and the temperature of the mixed solution was maintained at 25°C.

(5) After the stirring was completed, nitrogen gas was introduced for 10 minutes, and then the mixed solution was heated in an oil bath to 150° C., the heating time was about 18 minutes, and the flow rate of nitrogen gas was 200 mL/min.

(6) After the temperature was raised to the set temperature, the ventilation was stopped, and the closed reactor was allowed to stand for 60 minutes for reaction, and the reaction solution was quenched to obtain the silver nanowire puree.

This comparative example is the silver nanowire puree prepared without adding an organic reducing agent. It can be seen from the electron microscope characterization diagram that the obtained ones at a lower temperature are basically particles and thick and short rods, and no ultra-fine silver nanowires are obtained. , See Figure 4 for the SEM of the morphology of the puree.

Example 4

(1) Prepare the ethylene glycol solution of PVP: weigh PVP and dissolve it in glycol, put it on a heating plate and stir to dissolve, and the heating temperature is 130°C. The molecular weight of the PVP used is between 55,000 and 1,300,000, and the concentration of the prepared solution is 0.008g/mL.

(2) Preparation of ethylene glycol solution of potassium bromide: Weigh a certain mass of potassium bromide and dissolve it in ethylene glycol, put it on a heating plate and dissolve at 130°C, the concentration is 0.020g/mL.

(3) Prepare the ethylene glycol solution of AgNO ₃ : weigh a certain amount of pretreated silver nitrate and dissolve it in ethylene glycol, put it in an ultrasonic wave, and dissolve it in an ice bath for 8 minutes to completely dissolve it, the concentration is 0.035g /mL.

(4) Mix the PVP solution configured in step (1) with the silver nitrate solution configured in step (3), stir for 5 min at a rotating speed of 500 r/min, then add potassium bromide dropwise, and stir for 25 min at a rotating speed of 1000 r/min. The volumes of the silver nitrate solution and the PVP solution were 35mL and 165mL respectively; the volume of potassium bromide was 4mL, and the dropping rate was 0.16mL/s; the temperature of the mixed solution was maintained at 35°C.

(5) After the stirring is finished, add 0.05mol of organic reducing agent A, and stop stirring at 1500r/min for 1min. After nitrogen gas is introduced for 7min, the mixed solution is heated in an oil bath to 150°C, the heating time is 20min, and the nitrogen flow rate is 150mL/min . Wherein the organic reducing agent A is 4,4'-diaminobenzoin.

(6) After the temperature is raised to the set temperature, the ventilation is stopped, the closed reactor is allowed to stand for 80 minutes for reaction, and the reaction liquid is quenched to obtain the ultrafine silver nanowire puree.

Example 5

(1) Prepare the ethylene glycol solution of PVP: weigh PVP and dissolve it in glycol, put it on a heating plate and stir to dissolve, and the heating temperature is 130°C. The molecular weight of the PVP used is between 55,000 and 1,300,000, and the concentration of the prepared solution is 0.008g/mL.

(2) Preparation of ethylene glycol solution of potassium bromide: Weigh a certain mass of potassium bromide and dissolve it in ethylene glycol, put it on a heating plate and dissolve at 130°C, the concentration is 0.020g/mL.

(3) Prepare the ethylene glycol solution of AgNO ₃ : weigh a certain amount of pretreated silver nitrate and dissolve it in ethylene glycol, put it in an ultrasonic wave, and dissolve it in an ice bath for 8 minutes to completely dissolve it, the concentration is 0.035g /mL.

(4) Mix the PVP solution configured in step (1) with the silver nitrate solution configured in step (3), stir for 5 min at a rotating speed of 500 r/min, then add potassium bromide dropwise, and stir for 25 min at a rotating speed of 1000 r/min. The volumes of the silver nitrate solution and the PVP solution were 35mL and 165mL respectively; the volume of potassium bromide was 4mL, and the dropping rate was 0.16mL/s; the temperature of the mixed solution was maintained at 35°C.

(5) After the stirring is finished, add 0.05mol of organic reducing agent A, and stop stirring at 1500r/min for 1min. After nitrogen gas is introduced for 7min, the mixed solution is heated in an oil bath to 150°C, the heating time is 20min, and the nitrogen flow rate is 150mL/min . Wherein the organic reducing agent A is 4,4'-dichlorobenzoin.

(6) After the temperature is raised to the set temperature, the ventilation is stopped, the closed reactor is allowed to stand for 80 minutes for reaction, and the reaction liquid is quenched to obtain the ultrafine silver nanowire puree.

Claims (10)

1. a kind of preparation method of ultra-fine silver nanowires, which comprises the following steps:

Step 1, PVP, potassium bromide and silver nitrate are dissolved in ethylene glycol, are uniformly mixed, obtain mixed solution A；

Step 2, organic reducing agent A is added into mixed solution A, is uniformly mixed, mixed solution B is obtained, in the item for being passed through nitrogen Mixed solution B is warming up to reaction temperature under part, then stops being passed through nitrogen, react under confined conditions, it after the reaction was completed will be anti- Liquid quenching is answered, ultra-fine silver nanowires magma is obtained；Wherein, organic reducing agent A is the chemical combination that can generate Alpha-hydroxy benzyl radicals Object.

2. the preparation method of ultra-fine silver nanowires according to claim 1, which is characterized in that step 1 specifically: match respectively The ethylene glycol solution of the ethylene glycol solution of PVP processed, the ethylene glycol solution of potassium bromide and silver nitrate；By the ethylene glycol solution of PVP with The ethylene glycol solution of silver nitrate mixes, then stirring is added dropwise to the ethylene glycol solution of potassium bromide, stirs, obtains mixed solution A.

3. the preparation method of ultra-fine silver nanowires according to claim 2, which is characterized in that the ethylene glycol for preparing PVP is molten Liquid specifically: PVP is added in glycol, heating stirring dissolution；Prepare the ethylene glycol solution of potassium bromide specifically: by potassium bromide plus Enter in ethylene glycol, heating stirring dissolution；Prepare the ethylene glycol solution of silver nitrate specifically: silver nitrate is added in ethylene glycol, sets In ultrasound condition, made it completely dissolved under ice bath.

4. the preparation method of ultra-fine silver nanowires according to claim 2, which is characterized in that in the ethylene glycol solution of PVP The concentration of PVP is 0.005-0.01g/mL, and the concentration of potassium bromide is 0.01-0.030g/mL, nitre in the ethylene glycol solution of potassium bromide The concentration of silver nitrate is 0.01-0.05g/mL in the ethylene glycol solution of sour silver；The ethylene glycol of the ethylene glycol solution of silver nitrate, PVP The volume ratio of solution and the ethylene glycol solution of potassium bromide is 1:(2-6): (0.03-0.3).

5. the preparation method of ultra-fine silver nanowires according to claim 1, which is characterized in that organic reducing agent A is to rest in peace Perfume, 4,4 '-dimethoxy styraxes, 4,4 '-dimethyl styraxes, 4,4 '-diamino styraxes and 4, in 4 '-dichloro styraxes It is at least one.

6. the preparation method of ultra-fine silver nanowires according to claim 1, which is characterized in that in step 2, reaction temperature is 140-170 DEG C, reaction time 60-120min.

7. the preparation method of ultra-fine silver nanowires according to claim 1, which is characterized in that in step 2, be passed through nitrogen Under conditions of mixed solution B be warming up to reaction temperature be specifically: after being passed through nitrogen 5-20min, mixed solution B is warming up to 140-170 DEG C, heating-up time 10-30min.

8. the preparation method of ultra-fine silver nanowires according to claim 1, which is characterized in that PVP, potassium bromide, silver nitrate Mass ratio with organic reducing agent A is 1:(0.05-1): (0.5-5): (5-15).

9. the ultra-fine silver nanowires that the described in any item preparation methods of claim 1-8 are prepared.

10. ultra-fine silver nanowires according to claim 9, which is characterized in that a diameter of 12-14nm.