KR20180049906A - Method for manufacturing silver nanowires - Google Patents

Abstract

One embodiment of the present invention provides a method for manufacturing silver nanowires which is able to manufacture silver nanowires (AgNWs) of a high aspect ratio having fewer defects and having economic efficiency such that the method for manufacturing silver nanowires is applicable to mass production.

Description

METHOD FOR MANUFACTURING SILVER NANOWIRES < RTI ID = 0.0 >

The present invention relates to a method for producing silver nanowires.

Transparent conduction electrodes (TCEs) are used in a wide range of technical fields such as touch screen panels (TSP), thin-film solar cells, transparent displays, and flexible displays . Conventionally used conductive transparent electrodes include indium-tin oxide (ITO) thin films formed by sputtering. ITO thin films exhibit high transmittance and low sheet resistance. However, the mechanical strength such as bending stress is weak, and when applied to a large area TSP, there is a problem that the translucency decreases and the sheet resistance rises.

Accordingly, various alternative materials such as carbon nanotubes, graphenes, conductive polymers, and metal nanowires have been actively developed. Of these, one-dimension metal nanowires are attracting attention as new materials that can be applied to large-area touch screen panels, thin-film solar cells, flexible OLEDs, and transparent displays, and they are highly permeable, Research on silver nanowires (AgNWs) is underway. Conventionally, various manufacturing methods including a hard template method and a soft template method have been suggested as manufacturing methods of silver nanowires. Among them, a solution phase synthesis method using polyol reduction is popular. However, these methods are disadvantageous in that it is difficult to obtain silver nanowires having a high aspect ratio, and synthesis speed is slow. In addition, a high cost is consumed in the separation and purification of the silver nanowire thus produced, which is disadvantageous in that it is not industrially applicable.

Through an embodiment of the present invention, it is possible to manufacture silver nanowires (AgNWs) which can be manufactured at a high yield with a high aspect ratio of silver nanowires which are inexpensive, suitable for mass production and have few defects .

As described above, the solution-phase synthesis method of silver nanowires using the conventional polyol reduction is disadvantageous in that it is difficult to obtain silver nanowires having a high aspect ratio, high cost is consumed in separation and purification, Has come.

The present invention solves the above problems and provides a silver nanowire which can be manufactured at a high yield in a high aspect ratio silver nanowire (AgNWs) which is inexpensive, suitable for mass production, and has few defects And a manufacturing method thereof.

Specifically, one embodiment of the present invention is a method for preparing a silver nanowire comprising: preparing a silver nanowire through a reduction reaction in a solution containing a silver salt, a polyol solvent, a capping agent, a surfactant, and a halogen catalyst; Wherein the reduction reaction is performed in a tubular reactor in which the lower portion of the reactor is tapered. ≪ Desc / Clms Page number 3 > The lower portion of the reactor may be tapered, which means that the width of the reactor gradually narrows from a certain point in the lower portion of the reactor. FIG. 6 is an exemplary configuration diagram of a tubular reactor in which the lower portion of the reactor is tapered. FIG. However, the present invention is not limited to such a shape, but may be appropriately modified.

In the case of silver nanowires prepared by stirring a mixed solution of silver halide and polyol solvent in a closed system, the silver nanowires produced by the rotation of the stirring of the solution are subjected to shear stress with the wall surface of the reactor, Lt; / RTI > Thus, the shape of the silver nanowire may be destroyed, making it impossible to obtain high quality silver nanowires having a high aspect ratio.

When a tubular reactor having a tapered bottom portion is used as in the embodiment of the present invention, the prepared silver nanowire is placed on the lower portion of the tapered portion which is not affected by agitation , It is possible to prevent damage due to shear stress with the reactor wall surface. Thus, silver nanowires of high quality having a high aspect ratio can be obtained, and silver nanowires can be continuously produced by using a tubular reactor.

The method of making silver nanowires more specifically comprises the steps of injecting a first solution comprising a halogen catalyst, a capping reagent, a polyol solvent, and a surfactant into the reactor; Heating the first solution; And dropwise adding a second solution containing a silver salt and a polyol solvent to the heated first solution.

The step of dropwise introducing a second solution containing a silver salt and a polyol solvent into the heated first solution may be carried out under agitation of 100 rpm or more and 400 rpm or less. If the agitation speed is too slow, silver ions that do not participate in the growth of silver nanowires may increase, resulting in the problem of obtaining a large amount of amorphous silver nanoparticles. If the agitation speed is too fast, the silver nanowire produced may be destroyed, resulting in a problem of obtaining only a large amount of silver nanoparticles.

The stirring may be performed by mechanical stirring. In this case, the impeller used for the mechanical mixing is preferably a screw type impeller.

The height of the lower portion of the reactor, which is tapered, may be 10% or more and 30% or less by height relative to the total reactor height of 100%. If the tapered shape at the lower portion of the reactor is formed too long, the influence of agitation may greatly affect the lower portion of the reactor, and damage of the nanowires may occur in the lower portion of the reactor. If the taper shape of the lower portion of the reactor is too short, the produced silver nanowire may not be sufficiently placed under the tapered reactor.

 Here, the agitation may be performed at a position within a range of not less than 20% by height from the top of the reactor, and not more than 60% by height, with respect to the reactor height of 100% of the height of the reactor. By performing stirring at the position within the above range, the influence of stirring transmitted to the lower portion of the tapered reactor can be minimized. In addition, through this agitation, 10 < RTI ID = 0.0 >% < / RTI > from the bottom of the reactor for an average rotational speed of the solution in the range of 20% The average rotational speed of the solution in the lower portion of the tapered reactor of not less than 10% and not more than 30% of the height is controlled to be not less than 1/100 and not more than 1/20 so that the damage of the silver nanowires, .

The reactor is located at a lower portion of the reactor, and includes a discharge unit capable of discharging the prepared silver nanowire solution. And a valve capable of opening and closing the discharge portion. It may be possible to continuously perform the reduction reaction while dropping the second solution with the valve opened and simultaneously discharging the prepared silver nanowire through the reactor outlet portion . Specifically, it may be to open the valve immediately after confirming the nanowire production visually through the turbidity of the initial reaction solution. The opening timing of the valve may be sufficient at a time when the stable continuous reaction is not disturbed, but is not limited thereto.

The method of manufacturing silver nanowires according to an embodiment of the present invention may further include the step of precipitating the silver nanowires continuously discharged as described above under an aqueous solution of NaCl to separate the silver nanowires have.

Specifically, the step of precipitating the silver nanowires discharged from the reactor by precipitating the silver nanowires under an aqueous NaCl solution may be carried out in a precipitation reactor containing the silver nanowire solution discharged from the discharge part of the reactor have. The precipitation reactor may be separately provided to accommodate the silver nanowire solution discharged from the reactor.

Conventionally, silver nanowires were prepared through a reaction in a batch type reactor during the production of silver nanowires by polyol reduction, and silver nanowires were separated and purified through separate separation processes such as centrifugation. These additional processes have added cost and time, and they are not suitable for mass production and thus are difficult to be industrialized.

However, in the case of the silver nanowire manufacturing method according to an embodiment of the present invention, silver nanowires produced through the natural precipitation in the NaCl solution may be separated, so that a separate process such as centrifugation may not be performed. Thus, the process can be simplified and mass production of silver nanowires can be achieved at low cost, and it can be very easy to be industrialized.

Specifically, the NaCl content in the NaCl aqueous solution may be 20 wt% or more and 30 wt% or less based on 100 wt% of the total amount of the NaCl aqueous solution. In the NaCl aqueous solution of the concentration range, silver nanowires can be separated quickly and in high yield.

Dropwise introducing a second solution comprising a silver salt and a polyol solvent into the heated first solution, wherein the rate of dropwise dropping the second solution into the first solution is 1.0 ml / min or more, and 20 ml / min or less. If the feeding rate of the second solution is too slow or too fast, silver nanoparticles may be generated in a large amount. The discharging rate of the solution containing the silver nanowires discharged through the discharging portion of the reactor may be 1.0 ml / min or more and 20 ml / min or less. If the discharging rate is too low, too much silver nanowires produced in the lower portion of the reactor may accumulate and may be damaged by the influence of agitation. If the discharge rate is too high, there may arise a problem that the reduction reaction in the reactor is not sufficiently performed.

The step of heating the first solution may be heating to a temperature of 100 ° C or higher, and 250 ° C or lower. If the heating temperature is too low, the growth of silver nanowires may be inhibited, and silver nanoparticles may be produced in large quantities. If the heating temperature is too high, the silver nanowire may grow rapidly, leading to a problem of larger diameter or shorter length.

Hereinafter, the materials used in the reaction will be described in more detail.

"Capping reagent" refers to a chemical agent that preferentially interacts with and adheres to the side surface of the growing silver nanowire such that the cross-sectional surface of the silver nanowire can be crystallized. This capping reagent interacts more strongly with the lateral surface than interacts with the cross-sectional surface of the growing silver nanowire. Thus, the side surface is passivated, while the cross-sectional surface can be used for further crystallization to produce silver nanowires. Such a capping reagent may be poly (vinylpyrrolodone), polyvinyl alcohol, or a mixture of two or more thereof. More specifically, it may be poly (vinylpyrrolodone). However, other materials suitable for the role of the capping reagent can be employed, but the present invention is not limited thereto.

The weight average molecular weight (M _w ) of the capping reagent poly (vinyl pyrrolidone) may be 5,000 or more, and 1,500,000 or less. More specifically 5,000 or more, and 360,000 or less. If the weight average molecular weight of the poly (vinylpyrrolidone) capping reagent is too high, the viscosity of the reaction solution may increase and the yield of silver nanowires may decrease. Accordingly, when the concentration is within the above range, the viscosity of the reaction solution is optimized, and the yield of silver nanowires can be maximized.

"Silver salt" refers to a neutral compound having a positively charged silver ion and a negatively charged counter ion. The counter ion can be inorganic or organic. Specifically, the silver salt may be AgNO ₃ , AgClO ₄ , Ag (pyridine) ₂ , or a mixture of two or more thereof. Silver salts are dissolved in a solvent such as polyol, decomposed into silver ions and counter ions having opposite charges, and then silver ions are reduced by the polyol solvent to generate silver. The type of the silver salt is merely an example, but is not limited thereto.

Wherein the capping reagent in the first solution is poly (vinylpyrrolodone), the poly (vinylpyrrolidone) to the silver ion (Ag ⁺ ) contained in the silver salt in the second solution, (PVP) repeating unit in poly (vinylpyrrolodone) may be greater than 1.0 and less than 16.0. More specifically greater than 1.0, and less than 6.0. If the molar ratio of the capping reagent to the silver ion is too low, the capping of the growing silver nanowire may not be sufficiently achieved and the yield of silver nanowires of high aspect ratio may be lowered. If the molar ratio of the capping reagent to the silver ion is too large, the capping reagent may act on the crystal growth surface of the silver, so that the high aspect ratio of the silver nanowire may be lowered or the viscosity of the reaction solution may be increased to decrease the yield of the silver nanowire.

"Halogen catalyst" refers to salt additives including cations and anions. Salt additives are ionically separated into polar solvents such as water, alcohols and polyols (including ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol and glucose). The cation may be organic or inorganic. Anions are generally inorganic and include halogen ions (Cl-, Br-, F-, etc.). Due to the presence of such a catalyst, the anisotropic nanostructures containing silver atoms preferentially grow into seeds that form silver nanowires, thereby obtaining nanowires with a relatively high yield and relatively high monodispersity . The halogen catalyst may be NaBr, KBr, AgCl, KCl, or a mixture of two or more thereof. However, other materials capable of serving as a halogen catalyst can be employed, and the present invention is not limited thereto.

"Surfactant" serves as an auxiliary capping reagent and an interphase catalyst. Such a surfactant may be sodium dodecyl sulfate (SDS), sodium 2-ethyl hexyl sulfate, or a mixture of two or more thereof. More specifically, it may be, but is not limited to, sodium dodecyl sulfate (SDS).

Specifically, the concentration of the surfactant in the first solution may be greater than 0.24 mM, and less than 10.0 mM. More specifically greater than 0.24 mM, and less than 3.60 mM. If the concentration of the surfactant is too low, a large amount of amorphous silver particle aggregates may be produced, which may reduce the yield of silver nanowires. If the concentration of the surfactant is too high, silver ions may be delivered to the growing silver nanowire at too high a rate, resulting in the generation of a large amount of amorphous silver particles. More specifically, the yield of high-quality silver nanowires having a high aspect ratio within the range of more than 0.3 mM to 2.0 mM can be improved.

"Polyol solvent" refers to polar solvents in which silver salts, halogen catalysts, and capping reagents are dissolved. In addition, the polyol solvent functions as a reducing agent to transform silver salts into elemental metals. Generally, the reducing solvent may be a chemical reagent comprising at least two hydroxyl groups. The polyol solvent may be ethylene glycol, 1,2-propylene glycol, glycerol, or a mixture of two or more thereof. However, other materials may be employed as the polyol solvent suitable for reduction, but the present invention is not limited thereto.

Through an embodiment of the present invention, it is possible to manufacture silver nanowires (AgNWs) which can be manufactured at a high yield with a high aspect ratio of silver nanowires which are inexpensive, suitable for mass production and have few defects .

FIG. 1 is an electron microscope (SEM) photograph of a synthetic AgNW according to a change in mole ratio of Ag ⁺ ion: PVP repeat unit in one embodiment of the present invention.
2 is an electron micrograph (SEM) photograph of a synthetic AgNW according to a stirring speed (rpm) and a reaction time change.
3 is an electron micrograph of the synthetic AgNW according to the surfactant (SDS) content.
4 is an electron micrograph of AgNW synthesized using a NaCl / NaBr nucleating agent.
FIG. 5 is an electron micrograph of a mechanical stirrer impeller structure and reaction time of synthesized AgNW of a Batch type round cylindrical reactor.
6 is a view showing the structure of a tubular reactor which is an open tapered type reactor.
7 is an electron micrograph of AgNW synthesized using a tubular reactor, which is an open tapered tubular reactor of FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

In the following examples of the present invention, examples of the polyol solvent include ethylene glycol (EG), AgNO ₃ as silver salt, NaCl / NaBr as a halogen catalyst, poly (vinylpyrrolodone) ) And sodium dodecylsulfate (SDS) as a surfactant. All of the above reagents were used as purchased from Sigma Aldrich.

Comparative Example  1: Using a round three-necked flask Batch type  silver Nanowire  Produce.

1.875 g of polyvinylpyrrolidone (PVP, molecular weight 40,000) was added to a 100-ml round three-necked flask, and 20 ml of ethylene glycol was added thereto. Then, PVP and SDS were dissolved using a magnetic stir bar to prepare a first solution Respectively. To a 50 ml flask was added 1.875 g of AgNO ₃ and 5 ml of ethylene glycol, followed by stirring to prepare a second solution.

Then, the second solution was put in a dropping funnel, and the solution was added dropwise to the first solution heated at 160 ^° C at a rate of 1 ml / min. The magnetic stir bar was agitated for an appropriate time to prepare silver nanowires. After confirming that the reaction solution turned to gray, the reaction was terminated by cooling to room temperature.

After the reaction was completed, acetone was added in an excess amount of about 5 times and centrifugation was carried out to precipitate the silver nanowires. The solvent was removed. Then, acetone was added again, and the silver nanowires were redispersed and centrifuged twice. the resulting nanowires and in the Ag ⁺ ion compared to evaluate the conversion rate (wt%) to Ag metal and the resulting of the Ag metal component obtained by using a scanning electron microscope, it was evaluated for the ratio of the particles compared to the nanowire.

Comparative Example  2: Including surfactant (SDS) Batch type  silver Nanowire  Produce.

Silver nanowires were prepared in the same manner except that 0.115 g of sodium dodecyl sulfite (SDS) was added in addition to PVP in the preparation of the first solution of Comparative Example 1.

Comparative Example 3: NaCl / NaBr Seed the kerosene  inclusive Batch type  silver Nanowire  Produce.

Silver nanowires were prepared in the same manner as in the preparation of the first solution, except that NaCl / NaBr was added at a concentration of 0.001 / 0.00095 mMol as a nucleating agent in addition to the components of Comparative Example 2. The production of silver nanowires by the polyol method is carried out in such a manner that not only the concentration ratio of the reaction composition such as AgNO ₃ , the capping reagent PVP, the surfactant SDS, the nucleating agent NaCl / NaBr, but also the reaction time after injecting the second solution containing AgNO ₃ , Stirring speed, and the like. In this comparative experiment, conversion ratios of the silver nanowire products obtained by changing these conditions, the ratio of the nanoparticles to the silver nanowires, and the like are shown in Table 1 and FIGS.

Sample No. AgNO ₃ solution PVP / SDS solution SDS
(Mm) Stirrer speed
(rpm) Reaction Time after edition of PVP / SDS
(min) Ag: PVP
(mole ratio) AgNO ₃ (g) EG
(ml) PVP
(g) PVP
(MW) EG
(ml) SDS
(g) AgNW-P1 1.875 5 1.875 40,000 20 0.115 0.30 250 5 1: 1.5 AgNW-P2 0.937 5 1.875 40,000 20 0.115 0.30 250 5 1: 3.0 AgNW-P3 0.703 5 1.875 40,000 20 0.115 0.30 250 5 1: 4.0 AgNW-P4 0.469 5 1.875 40,000 20 0.115 0.30 250 5 1: 6.0 AgNW-S1 0.703 5 1.875 40,000 20 0.092 0.24 250 5 1: 4.0 AgNW-P3 0.703 5 1.875 40,000 20 0.115 0.30 250 5 1: 4.0 AgNW-S2 0.703 5 1.875 40,000 20 0.138 0.36 250 5 1: 4.0 AgNW-S3 0.703 5 1.875 40,000 20 0.161 0.42 250 5 1: 4.0 AgNW-S4 0.703 5 1.875 40,000 20 0.184 0.48 250 5 1: 4.0 AgNW-R1 0.703 5 1.875 40,000 20 0.115 0.30 80 5 1: 4.0 AgNW-P3 0.703 5 1.875 40,000 20 0.115 0.30 250 5 1: 4.0 AgNW-R2 0.703 5 1.875 40,000 20 0.115 0.30 500 5 1: 4.0 AgNW-P3 0.703 5 1.875 40,000 20 0.115 0.30 250 5 1: 4.0 AgNW-T1 0.703 5 1.875 40,000 20 0.115 0.30 250 10 1: 4.0 AgNW-T2 0.703 5 1.875 40,000 20 0.115 0.30 250 15 1: 4.0

1 is an electron microscope (SEM) photograph of a synthetic AgNW according to a change in molar ratio of Ag ⁺ ion: PVP repeat unit.

Specifically, in FIG. 1, the molar ratios of Ag ⁺ ion: PVP repeat unit are 1: 1.5, 1: 3.0, 1: 4.0, and 1: 6.0.

2 is an electron micrograph (SEM) photograph of the synthetic AgNW according to the agitation speed (rpm) and the reaction time change.

Specifically, FIGS. 2 (a) to 2 (c) show the results of a change in the stirring speed, namely (a) 80 rpm, (b) 250 rpm, and (c) 500 rpm. 2 (d) to 2 (f) show the results of (d) 5 minutes, (e) 10 minutes, and (f) 15 minutes depending on the reaction time.

Figure 3 is an electron micrograph of the synthetic AgNW according to the surfactant (SDS) content, wherein (a) 0.24 mM, (b) 0.30 mM, (c) 0.36 mM, (d) 0.42, and (e) 0.48 mM will be.

FIG. 4 is an electron micrograph of AgNW synthesized using a NaCl / NaBr nucleating agent, wherein (a) NaCl / NaBr = 0.00 / 0.00 mMol NaBr = 0.003 / 0.00295 mMol, and (c) NaCl / NaBr = 0.001 / 0.00095 mMol.

As shown in Table 1 and FIG. 1-4, the optimum condition of the silver nanowires by a closed system batch reaction using a round three-necked flask is as follows.

The molar ratio of the Ag ⁺ ions in the second solution to the PVP repeating units in the first solution is preferably 1: 4 in the case of the closed batch reaction.

(2) In the closed batch reaction using a round three-necked flask, the ratio of silver nanowires obtained as the reaction time increased after dropping the ethylene glycol containing AgNO ₃ into the second solution was remarkably decreased when the silver nanowires were produced, This is because when the magnetic stir bar rotates and agitates, it collides with the bottom surface of the three-necked flask, and the resulting silver nanowire is mechanically impacted to transform the amorphous into nanoparticles. As a disadvantage of the closed- .

③ In addition to the capping reagent PVP in the first solution, the surfactant SDS can be added to significantly increase the rate of silver nanowire synthesis. This is because the SDS can smoothly supply the countercurrent ion to the growing nanowire crystallization cross-section by exchanging Na ⁺ to Ag ⁺ .

(4) Capping in the first solution By introducing NaCl / NaBr nucleating agent in addition to reagents PVP and surfactant SDS, the diameter of silver nanowires generated is reduced, and silver nanowires are coated on the film to form transparent electrode films necessary for touch panels and flexible OLED devices It is possible to significantly reduce the haze when preparing the catalyst.

To overcome the disadvantages described above, a round three-necked flask reactor and a magnetic stir bar were connected to a cylindrical reactor (Resin Kettle) and a mechanical stirrer to produce silver nanowires at a high synthesis yield of silver nanowires The reaction was changed.

Comparative Example  4: Cylindrical reactor application Batch type  silver Nanowire  Produce.

In a 500 ml cylindrical reactor equipped with a mechanical stirrer, 15.0 g of polyvinylpyrrolidone and 0.92 g of SDS were added, and 160 ml of ethylene glycol was added and dissolved in a mechanical stirrer to prepare a first solution. 5.624 g of AgNO ₃ and 40 ml of ethylene glycol were placed in a 100 ml flask and stirred to prepare a second solution.

Then, the second solution was added to the dropping funnel and added dropwise to the first solution heated at 160 ^° C at a rate of 1 ml / min. The impeller shape and stirring speed of the mechanical stirrer were changed as shown in Table 2 below And silver nanowires were prepared by reacting them for an appropriate time. After completion of the reaction, the silver nanowires were recovered by centrifugation, and the metal conversion rate and the amorphous silver particle ratio versus silver nanowire were evaluated. The results are shown in Table 2 and FIG. 5 The advantages and disadvantages are as follows.

Sample
No. AgNO ₃ solution PVP / SDS solution Stirrer
(rpm) Reaction time
(min) Impeller
type Yield
(wire: particle) AgNO ₃
(g) EG
(ml) PVP
(g) PVP
(M _W ) EG
(ml) SDS
(g) AgNW-MD1 5.624 40 15 40,000 160 0.92 150 5 denticulated NA AgNW-MD2 5.624 40 15 40,000 160 0.92 150 10 denticulated NA AgNW-MD3 5.624 40 15 40,000 160 0.92 150 15 denticulated NA AgNW-MS1 5.624 40 15 40,000 160 0.92 150 5 screw 70.0% (75: 25) AgNW-MS2 5.624 40 15 40,000 160 0.92 150 10 screw 79.4% (80:20) AgNW-MS3 5.624 40 15 40,000 160 0.92 150 20 screw 45.7% (70:30) AgNW-MS4 5.624 40 15 10,000 160 0.92 150 5 screw 92.0% (90:10) AgNW-MS5 5.624 40 15 10,000 160 0.92 150 10 screw 94.0% (90: 10) AgNW-MS6 5.624 40 15 10,000 160 0.92 150 15 screw 94.2% (90:10)

FIG. 5 is an electron micrograph of a mechanical stirrer impeller structure and a reaction time of a synthetic AgNW of a batch-type round cylindrical reactor, wherein (a) to (c) show a denticulated impeller (D) to (f) are obtained by using a screw type impeller and PVP having a weight average molecular weight of 40,000, (g) to (i) screw type impellers and And PVP having an average molecular weight of 10,000.

Referring to FIG. 5, the following results are confirmed.

(1) When the shape of the impeller of the mechanical stirrer is a sawtooth shape, the morphology of the nanowire is rapidly impacted with the increase of the reaction time, and the amorphous particle is changed into the particle.

(2) When the mechanical stirrer was changed into a screw type and the stirring speed was lowered to 150 rpm than that of Comparative Example 1-3, the ratio of the nanowires increased. (2) If the reaction time exceeded 5 minutes after completion of the solution addition, Silver particles have increased, which means that the nanowires are not shocked.

When the weight average molecular weight of PVP contained in the first solution of the nanowire synthesis solution was lowered from 40,000 to 10,000, the Ag metal conversion rate and silver nanowire formation rate of Ag + ion were increased due to the decrease of the viscosity of the synthesis solution.

However, since the silver nanowire manufacturing method using the cylindrical reactor described above is a batch type reactor, the reaction time is long, the synthesis efficiency is low, and the reactant composition is changed according to the reaction time. have. To solve these problems, silver nanowires were fabricated into a continuous reactor using an open system continuous reactor using a tapered tubular reactor having a reduced entrance and a valve at the lower end of the tubular tubular reactor.

Example  1: Tapered tubular reactor In the Open System  Manufacture of continuous silver nano wire.

15.0 g of polypyrrolidone, 0.92 g of SDS and 200 ml of ethylene glycol were added to a 500 ml Tapered tubular reactor equipped with a mechanical stirrer (Fig. 6), followed by addition of 0.001 mMol / 0.00095 mMol NaCl / NaBr nucleating agent ethylene glycol solution Followed by stirring to prepare a first solution. 5.624 g of AgNO ₃ and 100 ml of ethylene glycol were placed in a 200 ml flask and stirred to prepare a second solution. The second solution was placed in a dropping funnel and added dropwise to the first solution heated at 160 ^° C at a rate of 1 ml / min while reacting with a screw type impeller at an appropriate speed for a suitable time to prepare silver nanowires . After 30 minutes, the valve at the lower outlet was opened and discharged at a rate of 1 ml / min to produce silver nanowires by a continuous reaction.

Example  2: Tapered tubular reactor In the Open System  Manufacture of continuous silver nano wire.

The first and second solutions were prepared in the same manner as in Example 1, and 150 ml of the first solution was placed in a tapered tubular reactor equipped with a four-necked injection port on the upper plate of the reactor, heated at 160 ^° C and 50 ml of the second solution 1 solution and reacted with stirring for 30 minutes. Next, the remaining 50 ml of the first solution and the 50 ml of the second solution are added to the dropping funnel and simultaneously dropped at a rate of 1 ml / min. While stirring at 250 rpm using a screw type impeller, And then discharged at a rate of 2 ml / min to produce silver nanowires by a continuous reaction. The results of silver nanowire synthesis obtained in Examples 1 and 2 are shown in Table 3 and Figs. 7-8.

Next, the recovery and purification of silver nanowires synthesized using a tapered tubular reactor were investigated.

Example  3: Tapered tubular reactor The obtained  silver Nanowire  Recovery and purification.

Using a tapered tubular reactor, silver nitrides were prepared in the same manner as in Example 2, and about 25 ml of the silver nanowire reaction solution was introduced into a 2,000-5,000 ml aqueous 25% NaCl solution by opening the lower outlet valve of the reactor. After stirring slowly, the mixture was allowed to stand at room temperature for 6 hours to form a silver nanowire precipitate by a natural sedimentation method. Next, the supernatant was removed using a siphon and then washed twice with 2,000 ml of pure water. The supernatant was removed, and the precipitated silver nanowires were separated and purified.

6 is a view showing the structure of a tubular reactor which is an open tapered type reactor.

AgNW was synthesized and recovered using a tubular reactor which was an open tapered tubular reactor of FIG. 6, and the results are shown in Table 3 below.

Reaction condition for synthesis of AgNWs with tapered tubular reactor Recovery of AgNWs AgNO ₃ solution PVP solution Temp
( ^o C) rpm Reaction
Time
(min) 25 wt% NaCl aq. solution
(g) Precipitation Yield
(%)
(wire: particle) AgNO ₃
(g) EG
(ml) PVP
(g) PVP
(M _W ) EG
(ml) SDS
(g) NaBr
(mM) 10.14 50 40.0 40,000 200 1.5 0.05 160 100 10 5,000 72.7
(85:15) 10.14 50 40.0 40,000 300 1.5 0.05 160 100 10 4,000 77.1
(90:10)
10.14 50 40.0 10,000 200 1.5 0.05 160 100 10 2,000 89.9
(90:10)

FIG. 7 is an electron micrograph of AgNW synthesized using a tubular reactor which is an open tapered reactor of FIG. 6, (a) low magnification and (b) high magnification.

As shown in Table 3 and Figs. 6 to 7, the case of synthesizing AgNW using a tubular reactor which is an open tapered type is evaluated as follows.

① Open System A tapered tubular reactor was used to obtain a silver nanowire with an aspect ratio of 1000: 1 at an average diameter of 30 + 5 nm and a length of 30 m.

(2) The method of introducing the first and second solutions into the tapered tubular reactor can be changed as in Example 1 and Example 2, and the shape of the silver nanowires obtained thereby can be controlled.

③ Using a tapered tubular reactor, silver nanowires were prepared and about 25 ml of silver nanowire reaction solution was taken in 2,000-5,000 ml of 25% NaCl aqueous solution by opening the lower outlet valve of the reactor, then slowly stirred for about 10 minutes, The AgNW was recovered and purified without Centrifuge method by forming a silver nanowire precipitate by natural sedimentation.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (15)

Preparing a silver nanowire through a reduction reaction in a solution containing a silver salt, a polyol solvent, a capping reagent, a surfactant, and a halogen catalyst;
Wherein the reduction reaction is performed in a tubular reactor in which a lower portion of the reactor is tapered.
Silver nanowires. The method of claim 1,
The method for producing silver nanowires includes:
Introducing into the reactor a first solution comprising a halogen catalyst, a capping reagent, a polyol solvent, and a surfactant;
Heating the first solution; And
And dropwise introducing into the heated first solution a second solution comprising silver salt and a polyol solvent.
Silver nanowires. 3. The method of claim 2,
The reactor comprises:
A discharge unit located in the lower portion of the reactor and capable of discharging the prepared silver nanowire solution; And
And a valve capable of opening and closing the discharge portion.
Silver nanowires. 4. The method of claim 3,
The method for producing silver nanowires includes:
With the valve open,
Wherein the reducing reaction is continuously performed while discharging the solution containing the silver nanowire through the reactor outlet while dropwise introducing the second solution.
Silver nanowires. 5. The method of claim 4,
In the silver nanowire manufacturing method,
The valve is opened at the time of confirming the manufacture of the nanowire at the initial stage of the reaction,
Silver nanowires. 5. The method of claim 4,
And precipitating the discharged silver nanowires under an aqueous NaCl solution to separate the silver nanowires.
Silver nanowires. The method of claim 6,
Precipitating the discharged silver nanowires under an aqueous solution of NaCl to separate the silver nanowires;
Wherein the solution is carried out in a precipitation reactor containing a silver nanowire solution discharged from an outlet of the reactor.
Silver nanowires. 8. The method of claim 7,
The content of NaCl in the NaCl aqueous solution,
With respect to 100 wt% of the total amount of the NaCl aqueous solution,
20 wt% or more, and 30 wt% or less.
Silver nanowires. 9. The method of claim 8,
The discharge speed of the solution containing the silver nanowires discharged through the discharging portion of the reactor is,
0.1 ml / sec or more, and 20 ml / sec or less.
Silver nanowires. 3. The method of claim 2,
The height of the lower portion of the reactor, which is tapered,
For a total reactor height of 100% height,
10% or more, and 30% or less.
Silver nanowires. 3. The method of claim 2,
In the first solution, the capping reagent is poly (vinylpyrrolodone)
The molar ratio of the PVP repeating unit in the poly (vinylpyrrolodone) to the silver ion (Ag ⁺ ) contained in the silver salt in the second solution is,
1.0, and less than 16.0.
Silver nanowires. 3. The method of claim 2,
Wherein the concentration of the surfactant in the first solution is at least < RTI ID =
Greater than 0.24 mM, and less than 10.0 mM.
Silver nanowires. 3. The method of claim 2,
The surfactant,
Sodium dodecyl sulfate (SDS), sodium 2-ethyl hexyl sulfate, or a mixture of two or more thereof.
Silver nanowires. 3. The method of claim 2,
The capping reagent,
Poly (vinylpyrrolidone), polyvinyl alcohol, or a mixture of two or more thereof.
Silver nanowires. 3. The method of claim 2,
The halogen-
NaBr, KBr, AgCl, KCl, or a mixture of two or more thereof.
Silver nanowires.

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