Abstract
Silver nanowires (AgNWs) hold great promise for applications in wearable electronics, flexible solar cells, chemical and biological sensors, photonic/plasmonic circuits, and scanning probe microscopy (SPM) due to their unique plasmonic, mechanical, and electronic properties. However, the lifetime, reliability, and operating conditions of AgNW-based devices are significantly restricted by their poor chemical stability, limiting their commercial potentials. Therefore, it is crucial to create a reliable oxidation barrier on AgNWs that provides long-term chemical stability to various optical, electrical, and mechanical devices while maintaining their high performance. Here we report a room-temperature solution-phase approach to grow an ultra-thin, epitaxial gold coating on AgNWs to effectively shield the Ag surface from environmental oxidation. The Ag@Au core-shell nanowires (Ag@Au NWs) remain stable in air for over six months, under elevated temperature and humidity (80 °C and 100% humidity) for twelve weeks, in physiological buffer solutions for three weeks, and can survive overnight treatment of an oxidative solution (2% H2O2). The Ag@Au core-shell NWs demonstrated comparable performance as pristine AgNWs in various electronic, optical, and mechanical devices, such as transparent mesh electrodes, surface-enhanced Raman spectroscopy (SERS) substrates, plasmonic waveguides, plasmonic nanofocusing probes, and high-aspect-ratio, high-resolution atomic force microscopy (AFM) probes. These Au@Ag core-shell NWs offer a universal solution towards chemically-stable AgNW-based devices without compromising material property or device performance.
Highlights
Silver nanowires (AgNWs) are known to have the highest electrical and thermal conductivity among metal nanowires, garnering significant attention for their use in transparent conductive films, including thin-film solar cells, supercapacitors, transparent heaters, and touch panels [1,2,3,4,5,6]
Approaches reported to address the long-term stability of AgNWs could be summarized into two major categories: (1) For devices fabricated with AgNW networks, a polymer or ceramic overlayer is coated on the AgNW networks predeposited on a substrate as a corrosion barrier, such as polydimethylsiloxane (PDMS) [18,19,20,21], poly (PMMA) [22, 23], poly (3,4-ethylenedioxythio-phene): poly(styrene sulfonate) (PEDOT: PSS) [24,25,26,27], reduced graphene oxide [28,29,30] and atomic-layer-deposited aluminumdoped zinc oxide (AZO) and aluminum oxide (Al2O3) [2, 31, 32]; (2) A relatively stable metal or carbon shell, such as Ni [33,34,35], C [36,37,38], Zn [39, 40], Sn [41, 42], Au [43,44,45,46] and Pt [47] is chemically grown on the AgNW surface through a solutionphase process before device fabrication
For the humidityassisted oxidative acceleration test, both AgNW and Ag@Au core-shell nanowire-based transparent electrodes were put into a tin container that stayed inside a larger aluminum can, which was filled with 300 mL of water at the bottom to imitate an environment with 100% humidity
Summary
Silver nanowires (AgNWs) are known to have the highest electrical and thermal conductivity among metal nanowires, garnering significant attention for their use in transparent conductive films, including thin-film solar cells, supercapacitors, transparent heaters, and touch panels [1,2,3,4,5,6]. Approaches reported to address the long-term stability of AgNWs could be summarized into two major categories: (1) For devices fabricated with AgNW networks, a polymer or ceramic overlayer is coated on the AgNW networks predeposited on a substrate as a corrosion barrier, such as polydimethylsiloxane (PDMS) [18,19,20,21], poly (methyl methacrylate) (PMMA) [22, 23], poly (3,4-ethylenedioxythio-phene): poly(styrene sulfonate) (PEDOT: PSS) [24,25,26,27], reduced graphene oxide (rGO) [28,29,30] and atomic-layer-deposited aluminumdoped zinc oxide (AZO) and aluminum oxide (Al2O3) [2, 31, 32]; (2) A relatively stable metal or carbon shell, such as Ni [33,34,35], C [36,37,38], Zn [39, 40], Sn [41, 42], Au [43,44,45,46] and Pt [47] is chemically grown on the AgNW surface through a solutionphase process before device fabrication Both methods have shown effectiveness in prolonging the lifetimes of AgNW mesh electrodes. The strategy developed here is cost-efficient and compatible with large-scale device fabrication, offers a universal solution to increase the stability of various high-performance AgNW-based devices for commercialization
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