Ion Permeability
of Polydopamine Films Revealed Using
a Prussian Blue-Based Electrochemical Method
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Abstract
Polydopamine
(PDA) is fast becoming a popular surface modification
technique. Detailed understanding of the ion permeability properties
of PDA films will improve their applications. Herein, we report for
the first time the thickness-independent ion permeability of PDA films
using a Prussian blue (PB)-based electrochemical method. In this method,
PDA films are deposited via ammonium persulfate-induced dopamine polymerization
onto a PB electrode. The ion permeability of the PDA films can thus
be detected by observing the changes in electrochemical behaviors
of the PB coated by PDA films. On the basis of this method, it was
unexpectedly found that the PDA films with thickness greater than
45 nm (e.g., ∼60 and ∼113 nm) can exhibit pH-switchable
but thickness-insensitive permeability to monovalent cations such
as potassium and sodium ions. These observations clearly indicate
the presence of a continuous network of interconnected intermolecular
voids within PDA films, regardless of film thickness