30 July 2010
Vol 329, Issue 5991

About The Cover

Cover image expansion

COVER Lead sulfide nanocrystals (green, lead; orange, sulfur) self-assemble in solution, forming two-dimensional aggregates and ultrathin single-crystal sheets on the micrometer scale. The formation of dense and highly ordered oleic acid monolayers (dark blue spheres with long projections) on the sheets' surfaces helps drive the oriented attachment of the nanocrystals, resulting in a material with outstanding photoconductive properties. See page 550. Image: Christian Klinke/Hamburg University, Germany