Porous nanoscale materials often have useful properties because of their proportionally large surface areas. Now, UCLA scientists have devised a way to make porous germanium, a semiconductor used in fiber optics and electrical components. This discovery means that nanoporous materials could soon be used to develop new kinds of solar cells or highly sensitive electronic sensors.

Until now chemists have had difficulty forming germanium that contains regularly spaced, nanoscale holes. Previous nanoporous materials were made from oxides, which are ideal for use as catalysts but have only a narrow range of usefulness in electronics. Using a technique called "surfactant templating," UCLA chemist Sarah Tolbert and colleagues combined a soap-like molecule, or "surfactant" with a special preparation of germanium molecules. Under the right conditions these two components mix and arrange themselves into a honeycomb lattice. The new compound is chemically treated to remove the surfactant, leaving a skeleton of germanium with very thin walls.

Porous germanium prepared in this way has an enormous surface area - 500 square meters per gram. That makes it ideal for use in highly sensitive sensors and detectors, in which tiny traces of a material must adhere to a surface to be detected.

Tolbert and her team used several approaches, one of which being extended x-ray absorption fine structure (EXAFS) techniques at SSRL's Beam Lines 4-1 and 6-2, to characterize these new nanoscale structures.

To learn more about this research see the full scientific highlight at:
http://www-ssrl.slac.stanford.edu/ research/highlights_archive/Ge.html

"Hexagonal Nanoporous Germanium through Surfactant-Driven Self-Assembly of Zintl Clusters" D. Sun, A.E. Riley, A.J. Cadby, E.K. Richman, S.D. Korlann, and S.H. Tolbert, Nature, 441, 1126-1130, (2006).