How to combine oxidation-resistance and electrochemical properties for copper nanowires? A magical touch using phenylenediamine

Among the available metal nanowires, copper nanowires exhibit excellent electrochemical properties and thus have been identified as a promising candidate for nano-devices fabrication. Going with the current trends, the next generation catalytic systems requires stable and efficient electrochemical materials. Copper nanowires have been shown to have better electrochemical efficiency over bulk copper. However, copper nanowires are easily oxidized under humid and mild conditions thus affecting their performance.

Presently, several post-synthesis methods have been developed to enhance the oxidation resistance of the copper wires, such as coating copper nanowires with metallic layers or graphene oxides. However, these methods are unfavorable for large scale production, and also reduce or block the electrochemical responses of copper nanowires. Therefore, the synthesis of oxidation resistant and electrochemically active copper nanowires have attracted significant attention of researchers. In a recently published literature, the alkyl amines on the copper nanowires surfaces have been shown to protect copper nanowire to some extent. However, synthesis of high-performance copper nanowires has remained a great challenge due to oxidation in most of polar or nonpolar solvents.

To this note, Texas A&M University scientists: Dr. Tan Zhang, Farhad Daneshvar (Ph.D candidate), Shaoyang Wang and led by Professor Hung-Jue Sue cross-examined the feasibility of using phenylenediamine isomers for fabricating high-performance copper nanowire structures as an alternative to alkyl amines. They also demonstrated the multiple roles of the amine groups during the synthesis of copper nanowires including coordination, reducing and capping agents for promoting the growth and protection of copper nanowires in an aqueous environment. Their work is currently published in the journal, Materials and Design.

In brief, the research team thoroughly exploring the significance of diamines in the synthesis of high-performance copper nanowires. In addition, they analyzed the various steps involved in the fabrication and growth of the copper nanowires. Eventually, they examined the oxidation resistance and electrochemical properties of the resultant copper nanowires.

The authors observed that phenylenediamine reduced to copper (II) ions to stable copper (I) ions, which was a vital step in the synthesis of the copper nanowires. Consequently, copper nanowires exhibited different growth paths. This was attributed to the different copper ions reduction strengths thus signifying the importance of both oxidation potential and coordination structures. Furthermore, the oxidation strengths of the three phenylenediamine isomers, that is, para, meta, and ortho were noted to be different. This further provided adequate protection to the copper nanowires.

In summary, the study by Texas A&M University researchers is the first to use aromatic diamines to synthesize copper nanowires. To actualize their study, it was necessary to cover the copper nanowires with a thin polyphenylediamine polymer layer to enhance its oxidation resistance and electrochemical properties. In addition, the resulting nanowires are favorable for use in various applications like batteries and biosensors. Altogether, their study provides vital information that will pave the way for syntheses of high-performance metal nanowires.