Pdop layer exhibiting zwitterionicity: a simple electrochemical interface for governing ion permeability

Abstract

Polydopamine film which contains amine groups and phenolic hydroxyl groups exhibits fully reversible, pH-switchable permselectivity for both cationic and anionic redox-active probe molecules. At high pH the film has a net negative charge that excludes anions but passes cations; at low pH it is positively charged and excludes cations but passes anions.

Deposition Mechanism and Properties of Thin Polydopamine Films for High Added Value Applications in Surface Science at the Nanoscale

“…However, silver is leached in the bacterial suspension and a second reduction step of Ag + cations in Ag is not possible [83,99] Membranes for separations and fuel cells Modification of a polysulfone membrane to make it permselective [78] The permselectivity of polydopamine is pH dependent and also depends on the synthesis method [79,80] Improvement of methanol barrier in fuel cells [102] Films for sensing Highly selective sensing of an analyte can be obtained by imprinting the molecule of interest in the polydopamine film during its formation [104][105][106] Coating of particles for the production of hollow capsules…”

Highly Selective Uptake and Release of Charged Molecules by pH‐Responsive Polydopamine Microcapsules

“…[24] Importantly, we have reported that polydopamine film exhibits zwitterionicity because Pdop molecules have a great deal of amino groups and phenolic groups; they are positively charged because of protonation of the amino group at low pH, while at high pH, they are negatively charged due to deprotonation of the phenolic group ( Figure 1A). [25] Therefore, the charged states of the Pdop coatings are supposed to impact the uptake and release characters of charged molecules.…”

Natural melanin pigments and their interfaces with metal ions and oxides: emerging concepts and technologies

“…[58,79] Polydopamine, a synthetic melanin analog, has been used to selectively extract and separate metal cations from aqueous solutions, leveraging on the different binding affinities of the pigments toward different cations. [67,100,101] Films of polydopamine can reduce Ag + cations into Ag nanoparticles, which impart antibacterial properties to the same films. [83] Self-assembled molecular networks of indole-2-carboxylic acid (I2CA, i.e., melanin's monomer DHICA lacking the two hydroxyl phenolic groups) have been investigated on Au (111) surfaces: I2CA showed, both in ultrahigh vacuum and at liquid/solid interfaces, hydrogen-bonded assemblies from molecular dimers, [102] the next step being the same study with DHI and DHICA.…”