The rinsing volume is important for avoiding cross-contamination of deposition solutions. While many multilayer films grow well even without rinsing, one
should carefully calculate the required rinsing volumes to avoid cross-contaminations in the case of LbL-assembly by dipping. Of course this is only relevant
when the rinsing solution is in a beaker into which the substrate is immersed
(e.g., dipping robot). When the substrate is withdrawn from a deposition
solution a thin film of the deposition solution will adhere to its surface, the
8j 1 Layer-by-Layer Assembly (Putting Molecules to Work)
volume of the adhering liquid can be estimated from the surface area of the
immersed object, assuming a thickness of the adhering liquid film of a few
microns. The dilution factor of the first rinsing bath is calculated by dividing the
volume of the first rinsing bath by the estimated volume of the adhering liquid.
Each further rinsing bath will increase the dilution factor correspondingly. The
number and volume of the rinsing baths should be chosen such that the overall
dilution factor is at least 1:106, otherwise the liquid adhering on the surface of
the substrate will contaminate the following deposition solution. Cross-contamination and the depletion of the concentration of the adsorbing molecules are
frequently underestimated, especially with large surface areas and with a large
number of deposited layers.