Diffusion coating, definition

The term A is related to the flow profile of the mobile phase as it traverses the stationary phase. The size of the stationary phase particles, their dimensional distribution, and the uniformity of the packing are responsible for a preferential path and add mainly to the improper exchange of solute between the two phases. This phenomenon is the result of Eddy diffusion or turbulent diffusion, considered to be non-important in liquid chromatography or absent by definition in capillary columns, and WCOT (wall coated open tubular) in gas phase chromatography (Golay s equation without term A, cf. 2.5). 

The patterning strategy (high molecular mass adsorbate and robust covalent attachment) can be extended to sub-lOOnm sized patterns by exploiting AFM-tip assisted transfer of PAMAM dendrimers. By scanning smfaces with an AFM tip, which has been previously coated with the dendrimers, molecules can be deposited onto, say, sihcon, mica or SAMs of NHS - CIO. In the case of mica and oxidized sihcon substrates, the originally deposited patterns were detectable, but the AFM friction images showed that dendrimer molecules may have diffused over the substrates. Based on the cmrently available data, spontaneous diffusion or tip-induced effects cannot be differentiated. It is, however, clear that the patterns produced do not possess sufficient stability and definition to be of any use. 

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