Abstract
Limitations of achieving highly sensitive and stable surface-enhanced Raman scattering (SERS) substrate greatly concern the suitable method for fabrication of large-area plasmonic nanostructures. Herein we report a simple approach using template-based synthesis to create a highly ordered two-dimensional array of gold-silver alloy nanowires, followed by the controlled dealloying process. This particular step of mild acid etching (15%v/v nitric acid for 5 min) allowed the formation of Raman hot spots on the nanowire tips while maintaining the integrity of highly active alloy composition and rigid nanowire array structure. Full consideration of SERS substrate performance was accomplished using 4-mercaptobenzoic acid (4-MBA) as a probe molecule. Exceedingly higher SERS signal (150-fold) can be achieved with respect to typical gold film substrate. Moreover, an excellent stability of SERS substrate was also determined for over 3 months storage time. In contrast to the previous studies which stability improvement was accomplished at a cost of sensitivity reduction, the simultaneous improvement of sensitivity and stability makes the controlled dealloying process an excellent choice of SERS substrate fabrication. In addition, uniformity and reproducibility studies indicated satisfactory results with the acceptable values of relative standard deviation.
Highlights
Nanowires (NWs) have received a great interest as building blocks for hierarchical assembly of complex nanostructures
It has been widely recognized that the use of template-based electrochemical deposition technique can be used to produce nanowires with controlled diameter, length, and elemental composition
Since there is no prior report on the morphological evolution of porous nanowires using mild etching conditions, 3 sets of experiments were performed in this study using nitric acid concentration of 15, 20, and 30%v/v and etching time of 1, 3, and 5 min
Summary
Nanowires (NWs) have received a great interest as building blocks for hierarchical assembly of complex nanostructures. The use of Ag NWs in SERS applications offers great electromagnetic field enhancement especially hierarchical Ag structures, the major drawback of metallic Ag is the rapid oxidation at the surface of nanostructures. This results in a dramatic decrease of SERS activity over time[11,12]. The novel controlled dealloying process proposed here offered an improved SERS signal from roughened surface, but surprisingly high stability can be obtained without diminishing the initial SERS signal, in contrast to previously reported procedures of protective layer coating
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