Keywords: Copper nanowires, hydrothermal

Abstract: In this paper, copper nanowires with different aspect ratios were synthesized by hydrothermal method at

150 ℃, using environmentally friendly and inexpensive reagents such as chloride dihydrate (CuCl

· 2H

O),

tetradecylamine (TDA), and glucose. Moreover, the effects of different reaction times and reactant ratios on

the synthesis were investigated to obtain copper nanowires with different aspect ratios spanning from 150 to

500.

1 INTRODUCTION

Copper nanowires are becoming increasingly

popular due to their advantages of good electrical

conductivity, low cost and abundant crustal content.

The applications of copper nanowires mainly depend

on their different aspect ratios. For example, copper

nanowires with low aspect ratio can be used for

catalytic reactions(He et al., 2014) and antimicrobial

applications(Jiang et al., 2015). High aspect ratio

copper nanowires can be used as transparent

electrodes(Guo et al., 2013) and they are also

applied in solar cells(Yu et al., 2016), organic light

emitting diodes(Eritt et al., 2010), and smart

windows(Runnerstrom et al., 2014). Therefore, it is

necessary to control the aspect ratio of the

synthesized copper nanowires. Zhang et al.

synthesized ultrathin semicircle-shaped copper

nanowires with the aspect ratio of around 2000,

which can be used in optical devices(Zhang et al.,

2018). Deshmukh et al. obtained high aspect ratio

copper nanowires which were used to fabricate

copper nanowire films with a sheet resistance of

24.5 Ω/sq, and a transmittance of T =

71%(Deshmukh et al., 2018). Wang et al.

successfully prepared copper nanowires by

hydrothermal method with aspect ratio of

approximately 2500(Wang et al., 2018). In this

paper, we prepared copper nanowires by a

hydrothermal method in an environmentally friendly

approach and investigated the effects of different

parameters in order to achieve controllable synthesis

of copper nanowires.

2 EXPERIMENTAL

2.1 Materials

Chloride dihydrate (Aladdin, AR), tetradecylamine

(Aladdin, 96%), and glucose (Aladdin, AR) were

used for the synthesis of copper nanowires.

Trichloromethane (Aladdin, 96%), ethanol (Aladdin,

99.7%), and hexane (Aladdin, 97%) were used as

solvents in centrifugal purification.

2.2 Synthesis of Copper Nanowires

Firstly, 0.34 g of copper chloride dihydrate, 0.36 g

of glucose and 1.6 g of tetradecylamine were

dissolved in 80 ml of deionized water. Then, the

mixture was stirred magnetically for half an hour.

Secondly, the solution was poured into a 100 ml

reaction tank, then charged into the reaction vessel,

and reacted at 150 ° C for 4 hours. Finally, after the

resulting solution was cooled down, the supernatant

was poured off, and the remaining red fibrous

material was collected. The fibrous material was

purified by centrifugation with deionized water, n-

hexane and chloroform, respectively. Finally, a pure

red material was obtained and stored in n-hexane.

Controllable Synthesis of Copper Nanowires by Hydrothermal

Method

Jinfeng Liu, Xiaohong Wang and Xiuqing Gong

Materials Genome Institute, Shanghai University, Chengzhong road, Shanghai 201800, China

Liu, J., Wang, X. and Gong, X.

Controllable Synthesis of Copper Nanowires by Hydrothermal Method.

DOI: 10.5220/0008187602030207

In The Second International Conference on Mater ials Chemistry and Environmental Protection (MEEP 2018), pages 203-207

ISBN: 978-989-758-360-5

203

Figure 1: SEM images of CuNWs. a. nCu : nglucose = 1:2; b. nCu : nglucose = 1:1; c. nCu : nglucose = 3:2; d. nCu :

nglucose = 2:1.

3 RESULTS AND DISCUSSION

3.1 Effect of Reactant Ratio

The effect of reactant ratios on the reaction was

investigated, especially the ratio between copper

chloride dihydrate and glucose. The amounts of

tetradecylamine and copper chloride dihydrate were

kept constant while the amount of glucose was

changed. The copper nanowires were obtained at the

same reaction time and reaction temperature.

Figure 1 exhibits the SEM images of CuNWs

synthesized with different reagent ratios. The

different reactant ratios caused the copper nanowires

to exhibit different morphologies. As seen from the

images in Figure 1, copper nanowires were formed

as the amount of glucose decreased, but several

copper crystals were also observed in Figure 1d. The

reason for this behaviour could be that ： the

presence of five hydroxyl groups in one glucose

molecule, and the ratio of Cu2+ to glucose

molecules should be 1:0.4 in theory. The amount of

steric hindrance agents remained constant, so the

directional growth of copper crystals was limited. As

a result of decreasing ratio of glucose, less copper

nanoparticles were obtained and they were not fully

elongated along the [110] direction(Jin et al., 2011)

to generate CuNWs conforming to the Ostwald

ripening process. This also explained why addition

of less glucose resulted in the formation of thinner

and shorter CuNWs (as described below). In order to

study the difference in morphology, 50 to 100

copper nanowires with different reactant ratios were

measured, their length was tested, and finally their

aspect ratio was calculated, as shown in Figure 2.

Figure 2 illustrates the effect of different reactant

ratios on the diameter of copper nanowires. As the

amount of glucose decreased, there was an overall

trend of decreasing diameter, which was because

less CuNPs led to incomplete growth. Therefore, the

copper nanowires with different aspect ratios can be

obtained.

MEEP 2018 - The Second International Conference on Materials Chemistry and Environmental Protection

204

Figure 2: Change in diameter of copper nanowires with different reactant ratios. The inset is a line chart indicating the

relationship between the reactant ratio and the aspect ratio.

3.2 Effect of Reaction Time

The effect of reaction time on the synthesis was also

investigated, by keeping the ratio of reactants the

same, and changing the reaction time to 4h, 8h, 16h,

24h, and 32h.

Figure 3 shows the scanning electron

micrographs of copper nanowires prepared at

different reaction times. CuNPs grew in a particular

orientation due to the selective binding of steric

agent TDA to {100} facets of Cu (Jia et al., 2013).

The amount of TDA was constant, indicating limited

steric effects, and a prolonged reaction time led to a

more complete growth of CuNPs. In theory, the

purity of CuNWs should be better with increase in

reaction time. However, a small of amount of

CuNPs were observed in Figure 3b, Figure 3c and

Figure 3d, which could be due to an insufficient

purification process.

As seen in Figure 4, as the reaction time

increased, the diameter of the copper nanowires

decreased and the aspect ratio increased. When the

reaction time increased, the time of oriented growth

became longer. As a result, the length of copper

nanowires increased, and the diameter decreased as

the amount of reactants remained constant, which is

consistent with Ostwald ripening.

Figure 3: SEM images of CuNWs prepared with different reaction times. a. 8h; b. 16h; c. 24h; d. 32h.

Controllable Synthesis of Copper Nanowires by Hydrothermal Method

205

Figure 4: Change in diameter of copper nanowires with different reaction times. The inset is a line chart indicating the

relationship between the reaction time and the aspect ratio.

4 CONCLUSIONS

In this work, copper nanowires were controllably

prepared by a TDA-assisted hydrothermal method.

Moreover, the effects of different reactant ratios and

reaction times on the morphology of the resulting

copper nanowires were investigated. By varying the

above reaction parameters, CuNWs were obtained

with different aspect ratios ranging from 150 to 500.

When the amount of glucose decreased and reaction

time increased, thinner CuNWs were obtained. Thus,

the results of this work could help guide the

production of suitable CuNWs for different

applications such as sensors and solar cells.

ACKNOWLEDGEMENTS

This work was sponsored by the Shanghai Pujiang

Program (17PJ1402800) and the National Natural

Science Foundation of China (21775101).

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