Two-dimensional nanoarchitectonics based on self-assembly.

Top-down nanofabrication techniques, especially photolithography, have advanced nanotechnology to a point where system-process integration with bottom-up self-assembly is now required. Because most lithographic techniques are constrained to two-dimensional planes, investigation of integrated self-assembly systems should focus on two-dimensional organization. In this review, research on two-dimensional nanoartchitectonics is classified and summarized according to the type of interface used. Pattern formation following deposition of vaporized molecules onto a solid surface can be analyzed with high structural precision using scanning probe microscopy under ultra high vacuum. Transitions of adsorbed phases and adjustment of pattern mismatch by conformational changes of adsorbed molecules are discussed, in addition to the forces constraining pattern formation, i.e., two-dimensional hydrogen bond networks, van der Waals forces, and molecule-surface interactions. Molecular deposition at a liquid-solid interface broadens the range of molecules that can be investigated. The more complex molecules discussed in this work are C(60)-fullerene derivatives and designer DNA strands. Gas-liquid interfaces, e.g. between air and water, allow dynamic formations that can adjust to molecular conformational changes. In this case, any resulting patterns can be modulated by varying conditions macroscopically. Using flexible molecules at the fluid air-water interface also permits dynamic operation of molecular machines by macroscopic mechanical motion, thus enabling, hand-operated nanotechnology. Copyright 2010 Elsevier B.V. All rights reserved.