Facile synthesis of nearly monodisperse AgCu alloy nanoparticles with synergistic effect against oxidation and electromi
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Facile synthesis of nearly monodisperse AgCu alloy nanoparticles with synergistic effect against oxidation and electromigration Qianqian Dou1
, Yang Li1, Ka Wai Wong1, Ka Ming Ng1,a)
1
Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong 999077, China Address all correspondence to this author. e-mail: [email protected]
a)
Received: 7 November 2018; accepted: 11 February 2019
Bimetallic nanoparticles (NPs) have attracted a great deal of attention due to the synergistic interaction between metal components. In this work, the thermal process in which the reducing agent is not expensive or hazardous as those in traditional methods was employed to prepare alloy Ag–Cu NPs. The molar ratio between Ag and Cu was varied from 1:9 to 9:1. Nearly monodisperse NPs with alloy structure were characterized by X-ray diffraction and high-resolution transmission electron microscopy with energy dispersive spectroscopy In comparison with monometallic Ag and Cu NPs, the alloyed Ag–Cu NPs showed better monodispersity, especially when the ratio between Ag and Cu was 1:1. Moreover, the alloyed Ag–Cu NPs exhibited enhanced resistance to electromigration and oxidation, the respective problem of pure Ag and Cu. The alloyed Ag–Cu NPs also exhibited improved properties than a mixture of Ag–Cu NPs. This study should serve as the foundation for exploring high performance alloyed bimetallic NPs.
Introduction The use of metal nanoparticles (NPs) for conducting electricity in electronic devices such as touch screens and solar panels was initiated decades ago [1]. Most common are silver (Ag), copper (Cu), and gold (Au) metals [2]. Ag is the top choice because it is nontoxic, has a high electrical and thermal conductivity, and is relatively stable in the presence of oxygen although the high price of Ag is a handicap [3, 4]. Therefore, many recent studies have focused on replacing Ag NPs with alternative metals, such as Cu [5], nickel (Ni) [6], and tin (Sn) [7]. Cu has received the most attention because of its low cost and relatively high conductivity. Since Cu is easily oxidized in ambient atmosphere, various attempts have been made to stabilize Cu NPs. Coating of Cu NPs with a relatively inert material is an effective way [8]. Diverse materials such as surfactant, metal oxide, polymer, and carbon have been introduced to serve as an oxygen barrier [9]. These nonmetallic coverings often have low electric conductivity, which hinders the application of the NPs in printed electronics. Conductive metals could be used. The disadvantages are that separate procedures are required to synthesize the core and shell, and that the over-
ª Materials Research Society 2019
growth is hard to control [10]. An alternative is Cu-based bimetallic NPs that are less susceptible to oxidation [11]. Compared to monometallic NPs, bimetallic NPs have shown better optical, electronic, and catalytic properties, which can be attributed to ensemble and electronic effects [12]. Among the candidates, Ag is probably the
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