Electrochemical Investigation of the Growth of Copper Nanowires in the Presence of Ethylenediamine through Mixed Potential

Abstract

Copper (Cu) nanowires about 90 nm in mean diameter and lengths of about 50 μm were successfully synthesized by electroless deposition at 60 • C in the presence of ethylenediamine (EDA). Without addition of EDA, only large Cu particles were formed in the solution. On the other hand, high quality nanowires were formed in the presence of 176 mM EDA. Below this amount, shorter Cu nanowires were observed. The mixed potential shifted to more negative values without EDA, indicating faster reduction rate. It is possible that EDA does not only act as a structure-directing agent, but also slows down Cu deposition. This condition favors formation of long and thin Cu nanowires. Then again, in all EDA concentrations experiment, the mixed potential is below the oxidation-reduction potential of the Cu(II)/Cu redox pair, suggesting Cu depositions occurs instantaneously at 60 • C. Cu nanowire transparent conducting electrode attained a sheet resistance of about 197 sq −1 at a 61% optical transmittance. Copper (Cu) nanowire is gaining a lot of attention due to its viability as a material for transparent conductive film commonly used in various optoelectronic devices, such as flat panel display, organic light emitting diodes (OLED) and touch sensor.1-3 Bulk Cu has high electrical and heat conductivity.4-5 Thus, Cu is traditionally used as wires in mains cables in houses and buildings and as heat exchangers in hot water tanks. Cu is also an abundant element and has excellent recyclability. This makes Cu an attractive alternative for both indium tin oxide (ITO) film and silver (Ag) nanowires for transparent conducting applications in future electronic devices.Solution-phase synthesis of Cu nanowires in both organic and aqueous media are currently being widely used to prepare uniform ultralong nanowire.1-11 While organic syntheses have produced quality nanowires, they are relatively more expensive than those performed in aqueous media due to high cost of reagents and higher energy requirement to initiate the chemical reaction. [4][5][7][8][9][10][11] The synthesis of Cu nanowires at low temperatures (0-80• C), specifically in aqueous solution, has been challenging due to difficulties in promoting nanowire growth and preventing oxidation. [1][2][3]6,12,13 Nevertheless, the use of water and low temperatures would greatly simplify the preparation method for Cu nanowires and make the process commercially feasible.In recent reports, surfactants, such as ethylenediamine (EDA), 1,6,8,12,13 hexadecylamine (HDA) 7 and octadecylamine (ODA), 2,10 have played a significant role in preventing oxidation and controlling the dimension of Cu nanowires prepared in water. Other studies have even utilized two surfactants at the same time to further increase length of the Cu nanowires and improve their surface quality. 3,4,11,14 For example, the diameter of Cu nanowires synthesized with EDA was decreased by about 55% when a small amount of cetyltrimethyl ammonium bromide (CTAB) was added into the solution.14 Additionally, the surface roughness of the Cu ...

Modulating the Growth Rate, Aspect Ratio, and Yield of Copper Nanowires with Alkylamines

“…The main disadvantage of Cu nanowires is that, unlike Ag and Au, they are easily oxidized by atmospheric oxygen. Therefore, many research articles have been devoted to the synthesis of Cu nanowires, as well as coating methods to protect Cu nanowires from oxidation. − Methods to make Cu nanowires include chemical vapor deposition, , electrochemical deposition in templates, , and solution-phase syntheses. − Among these methods, solution-phase synthesis has the greatest potential for producing large quantities of nanowires at low cost . The solution-phase synthesis of Cu nanowires requires low reaction temperatures (60–100 °C) and can proceed at atmospheric pressure.…”

“…The two main solution-phase syntheses for Cu nanowires involve the use of (1) ethylenediamine (EDA) in an alkaline (8–15 M NaOH) aqueous solution ,,,,− and (2) alkylamines (e.g., hexadecylamine or octadecylamine) in a neutral aqueous solution. − In the first synthesis, electrons from the oxidation of hydrazine (N 2 H 4 ) reduce tetrahydroxocuprate­(II) and dihydroxocuprate­(I) complexes while EDA promotes anisotropic growth by selectively inhibiting oxidation on the (111) facets at the end of a growing Cu nanowire . The dimensions of Cu nanowires can be controlled by changing the concentrations of NaOH, EDA, N 2 H 4 , reaction temperature, and stirring during the reaction. ,− For example, a decrease in the reaction temperature from 70 to 60 °C can increase the aspect ratio from 1860 to 5700, and a decrease in N 2 H 4 below 5.7 mM can decrease the diameter from 65 to 35 nm . Higher concentrations of EDA can reduce the nanowire aspect ratio and can also result in the formation of tapered Cu nanowires …”

Review on the Synthesis and Antioxidation of Cu Nanowires for Transparent Conductive Electrodes

“…Tan et al 80 demonstrated the necessity of using hydrazine to promote anisotropic reduction of Cu(II). Without EDA, only Cu particles are formed in the solution.…”

Study on Growth Mechanism of Cu Nanowires and Its Application as Transparent Conducting Electrode

“…The growth of CuNWs also was determined by the concentration of EDA. When EDA is injecting on the solution, CuNWs begin growth along the axial onedimensional (1-D) [13]. Fig.…”