Nanofabrication of Double-Gyroid Thin Films

Abstract

Nanoporous silica films with the double-gyroid structure offer tremendous technological potential for sensors 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-surfacearea electrodes, photoelectrochemical devices, photovoltaics, and thermoelectrics. Here, we report a new robust synthesis of highly ordered nanoporous silica films with the double-gyroid structure by evaporationinduced self-assembly (EISA) at room temperature and laboratory humidity using a commercially available EO 17 -PO 12 -C 14 surfactant. The continuous nanoporous films are synthesized on conducting electrodes. Electrochemical impedance spectroscopy is then used to quantitatively measure the accessible surface area of the underlying electrode via transport through the pore system. It is found that the double-gyroidstructure silica films expose a much higher fraction of the electrode than other commonly synthesized nanostructures such as 2D centered rectangular or 3D rhombohedral nanostructures. The double-gyroid nanoporous-film-coated electrodes are then used to fabricate inverse double-gyroid platinum nanostructures by electrodeposition, followed by etching to remove the silica. The structure of both the nanoporous silica films and the nanoporous platinum films (after etching) have been elucidated using high-resolution field-emission scanning electron microscopy (FESEM), comparing measured and simulated 2D grazing angle-of-incidence small-angle X-ray scattering (GISAXS) patterns, and comparing observed and simulated transmission electron microscopy (TEM) images. Both films are highly (211) oriented and described by a cubic Ia3 hd space group that has undergone uniaxial contraction perpendicular to the substrate. Upon this contraction, Ia3 hd symmetry is broken, but the films retain the double-gyroid topology. The nanoporous silica 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 the sub-5 nm length scale.

A Re-Evaluation of the Morphology of a Bicontinuous Block Copolymer−Ceramic Material

“…Compression of a cubic lattice breaks the screw-axis and glide-plane symmetries of the Ia3d space-group and {110} and {200} reflections are no longer forbidden. 18,19 Thus, the observation of {110} and {200} reflections does not rigorously exclude a double gyroid structure distorted by lattice compression (distorted-G).…”

Singular Geometry of the Momentum Space: From wire networks to quivers and monopoles

“…Recently, a new nano-material in the form of a double gyroid has been synthesized [38]. It is based on a thickened triply-periodic minimal surface, whose complement consists of two non-intersecting channels.…”

“…It is based on a thickened triply-periodic minimal surface, whose complement consists of two non-intersecting channels. These can be filled with conducting or semiconducting materials [38] to function as nanowire networks with potentially useful electronic properties [26]. The nontrivial topology of such a network has motivated our study of its commutative and noncommutative geometry [21].…”

“…The Material and Production. A solid-state double gyroid can be synthesized by selfassembly at the nanoscale, as demonstrated by Urade et al [38]. The first step is production of a nanoporous silica film with the structure of unidirectionally cotracted double gyroid (DG) with lattice constant of about 18 nm.…”

“…The pores in the structure can then be filled with other materials to form nanowires. Fabrication of platinum DG nanowires by electrodeposition has been demonstrated in [38], where it has also been mentioned that the process can be used for other metals or semiconductors.…”