self-assembly
(rus. самосборка)
—
a process of formation of ordered supramolecular structures or media in which the components (elements) of original structure remain almost unchanged but band together to form the resulting complex structure.
Description
Self-assembly is a typical method to fabricate nanostructures (nanomaterials) in the "bottom-up" process. The main problem that hampers implementation of this concept is the need to influence the system's parameters and set properties of individual particles in such a way as to make them get organised into the desired structure. Self-assembly forms the basis of many supramolecular chemistry processes where "instructions" on how to assemble large objects are "encoded" in the structural features of individual molecules. We should distinguish self-assembly from self-organisation, which can be used as a mechanism to create complex "patterns", processes and structures at a higher hierarchical level of organisation than the one observed in the initial system (see the Figure). The differences lie in numerous and multi-choice component interactions at low levels which have their own, local, laws of interaction different from the laws of collective behaviour of the ordering system itself. The self-organisation processes are characterised by their different scale of interaction energies as well as restrictions of the system's degrees of freedom on several different levels of organisation. Thus, the self-assembly process is a simpler phenomenon. Nevertheless, we should not go to extremes assuming, for example, that the growth of monocrystals is nothing but the self-assembly of atoms (which agrees, in principle, with the definition); although, on the other hand, the self-assembly of larger objects, e.g. micro beads of the same size forming a dense spherical packing to grow the so-called photonic crystal (three-dimensional diffraction grating composed of micro beads) is a typical example of self-assembly. The term "self-assembly" can be applied to the formation of self-monomolecular layers (e.g., molecules of thiols on the smooth surface of gold film), formation of Langmuir-Blodgett films, layer-by-layer deposition etc.
Illustrations
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Examples of self-assembly: typical projections of binary superlattices formed by different nanoparticles, and model elementary cells of corresponding 3D structures. Author: Dmitry Talapin, University of Chicago, USA [1]. |
Author
- Goodilin Evgeny A.
Sources
- Philosophy of nanosynthesis (in Russian). // Nanometr, 2007. — www.nanometer.ru/2007/12/15/samosborka_5415.html (reference date: 12.12.2011).
- Self-assembly // Wikipedia, the free Encyclopedia. — http://en.wikipedia.org/wiki/Self-assembly (reference date: 12.12.2011).