Planar Arrays of Nanoporous Gold Nanowires: When Electrochemical Dealloying Meets Nanopatterning

Abstract

Nanoporous materials are of great interest for various technological applications including sensors based on surface-enhanced Raman scattering, catalysis, and biotechnology. Currently, tremendous efforts are dedicated to the development of porous one-dimensional materials to improve the properties of such class of materials. The main drawback of the synthesis approaches reported so far includes (i) the short length of the porous nanowires, which cannot reach the macroscopic scale, and (ii) the poor organization of the nanostructures obtained by the end of the synthesis process. In this work, we report for the first time on a two-step approach allowing creating highly ordered porous gold nanowire arrays with a length up to a few centimeters. This two-step approach consists of the growth of gold/copper alloy nanowires by magnetron cosputtering on a nanograted silicon substrate, serving as a physical template, followed by a selective dissolution of copper by an electrochemical anodic process in diluted sulfuric acid. We demonstrate that the pore size of the nanowires can be tailored between 6 and 21 nm by tuning the dealloying voltage between 0.2 and 0.4 V and the dealloying time within the range of 150-600 s. We further show that the initial gold content (11 to 26 atom %) and the diameter of the gold/copper alloy nanowires (135 to 250 nm) are two important parameters that must carefully be selected to precisely control the porosity of the material.

Plasmonic nanosponges

“…By combining with other synthesis or nanofabrication methods including polyol process, templated process, solid-state dewetting, and different nanolithography techniques, Au-Ag alloys can be formed in many specific forms, and after dealloying, the nanoporous gold can be obtained in the corresponding forms, including the forms of nanotubes [38], nanowires [39], nanoparticles [17,40,41], hollowed nanospheres [42], nanobowls [43], nanodisks [44,45], ordered array of nanoparticles and nanodisks [46][47][48].…”

Dealloying of gold–copper alloy nanowires: From hillocks to ring-shaped nanopores

“…The transmission electron microscopy (TEM) cross-section images of the Au–Cu alloy nanowires show that the hillocks exhibit the same multilayered structure observed for the main body of the nanowire (Supporting Information File 1, Figure S2). This multilayered structure, not present in case of elemental metals, is related to the substrate rotation during the co-sputter deposition [23–24]. …”

“…For this purpose, we applied an electrochemical dealloying process to Au–Cu alloy nanowires, similarly to the conditions used in our previous work [24], to selectively leach copper from the alloy leaving behind a porous skeleton of gold [25–31]. In Fig.…”

Effect of temperature on the synthesis of nanoporous carbon from copper/carbon thin films to nanoporous carbon for sensing applications

“…Enormous efforts have been dedicated lately to the development of novel techniques allowing synthesizing nanoporous materials with adjustable properties, [7,8] including wet-chemical and electrochemical routes [9], template approaches [10], chemical vapor deposition [5,11], pyrolysis of organic polymer precursors [3] and low-energy cluster beam deposition [11].…”