| Abstract
| - Nanoporous silica films with the double-gyroid structure offer tremendous technological potential forsensors and separations because of their high surface area and potentially facile transport properties.Further, metals and semiconductors with similar structure open up new opportunities for high-surface-area electrodes, photoelectrochemical devices, photovoltaics, and thermoelectrics. Here, we report a newrobust synthesis of highly ordered nanoporous silica films with the double-gyroid structure by evaporation-induced self-assembly (EISA) at room temperature and laboratory humidity using a commercially availableEO17−PO12−C14 surfactant. The continuous nanoporous films are synthesized on conducting electrodes.Electrochemical impedance spectroscopy is then used to quantitatively measure the accessible surfacearea of the underlying electrode via transport through the pore system. It is found that the double-gyroid-structure silica films expose a much higher fraction of the electrode than other commonly synthesizednanostructures such as 2D centered rectangular or 3D rhombohedral nanostructures. The double-gyroidnanoporous-film-coated electrodes are then used to fabricate inverse double-gyroid platinum nanostructuresby electrodeposition, followed by etching to remove the silica. The structure of both the nanoporoussilica films and the nanoporous platinum films (after etching) have been elucidated using high-resolutionfield-emission scanning electron microscopy (FESEM), comparing measured and simulated 2D grazingangle-of-incidence small-angle X-ray scattering (GISAXS) patterns, and comparing observed and simulatedtransmission electron microscopy (TEM) images. Both films are highly (211) oriented and described bya cubic Ia3̄d space group that has undergone uniaxial contraction perpendicular to the substrate. Uponthis contraction, Ia3̄d symmetry is broken, but the films retain the double-gyroid topology. The nanoporoussilica and the platinum nanowires have a characteristic wall or wire thicknesses of approximately 3 nm.This nanofabrication process opens up a facile general route for fabrication of ordered structures on thesub-5 nm length scale.
- A simple and easily reproducible strategy for assembling nanoporous silica films having the double-gyroid structure is presented. Taking advantage of the highly open and accessible nature of the pore system, we electrodeposited Pt using double-gyroid silica film as a temple to create self-supporting Pt nanowire networks with high fidelity.
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