An
assembly of molecules
around an 'axle'. Applications
include colourfastness of fabric dyes by threading a rod-like azo dye molecule through a ring of six glucose molecules (a cyclodextrin). This assembly is a
rotaxane. The cyclodextrin sleeve protects the dye, yet, despite its
bulkiness, allows the colourant to fasten on to the cellulose in cotton
fibres much better. HP have used memory bits made of rotaxanes, rather than
silicon - the first significant demonstration of 'molecular
electronics'.
In this application
the rotaxane structures are trapped at the intersection of platinum and
titanium wires that are only 40nm wide.
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