Self-assembly

Key point: Components that can self-assemble fall between the sizes that can be controlled chemically and those that can be manipulated by conventional manufacturing; self-assembly offers the crucial technique to bridge top-down and bottom-up methods. Various definitions of self-assembly have been proposed. They include the noncovalent interaction of two or more molecular subunits to form an aggregate with novel structure and properties that are determined by the nature and positioning of the components, the spontaneous assembly of molecules into structured, stable, noncovalently joined aggregates, the spontaneous formation of higher-ordered structures, and the process by which specific components spontaneously assemble in a highly selective fashion into a well- defined, discrete supramolecular architecture. Because the components that assemble fall between the sizes that can be controlled chemically and those that can be manipulated by conventional manufacturing, self-assembly may offer the crucial technique to bridge top-down and bottom-up methods. An example of the application of methods that bridge top-down and bottom-up assembly has been the development of microdevices capable of heterogeneous catalysis, acting as lasers, and as the basis of gas sensing. Potential self-assembly components must be mobile, therefore self-assembly usually takes place in fluid phases or on smooth surfaces. Static self-assembly occurs when the system is at a global or local equilibrium, such as in liquid crystals. Dynamic selfassembly occurs when the system is dissipating energy, such as in an oscillating chemical reaction. Templated self-assembly occurs when systems are organized based on interactions bet-ween the components and regular features in the environment. The QD self-assembly that occurs during strained heteroepitaxy in MBE and the use of laserembossed surfaces for small reaction vessel synthesis in ordered arrays (Section 25.5) are examples of templated self-assembly. Finally, biological self-assembly occurs in systems involving life, such as cells and tissues: entire organisms are elaborate examples of biological self-assembly.

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مواضيع ذات صلة

Quantum wells

Two-dimensional control: quantum wells and solid-state superlattices

One-dimensonal control: carbon nanotubes and inorganic nanowires

Supramolecular chemistry and dimensonality

Morphosynthesis

Chemical vapour deposition

Physical vapour deposition

Nanosized reaction vessels

Vapour-phase synthesis of nanoparticles

Black, absorbing, and specialist pigments

White pigments

Other inorganic hydrogen-storage materials