Monolithic, high surface area, three-dimensional GeO2 nanostructures

We report a sol-gel synthesis of monolithic three-dimensional GeO2 nanostructures (aerogels). Transmission electron microscopy shows that these ultralow-density (similar to 99.2% porous) nanostructures are formed by a continuous network of elongated amorphous GeO2 nanoligaments, similar to 15-20 nm in diameter and similar to 50-200 nm in length. As a result, monoliths exhibit a high surface area of similar to 60 m(2) g(-1). A comparison of soft x-ray absorption spectra at Ge L-3 and O K edges with theoretical densities of states reveals that the electronic structure of aerogels is similar to that of hexagonal GeO2, indicating a (distorted) tetrahedral environment of Ge atoms in the amorphous nanostructure.