Tunable Synthesis of Prussian Blue in Exponentially Growing Polyelectrolyte Multilayer Films

Abstract

Polyelectrolyte multilayer (PEM) films have become very popular for surface functionalization and the design of functional architectures such as hollow polyelectrolyte capsules. It is known that properties such as permeability to small ionic solutes are strongly dependent on the buildup regime of the PEM films. This permeability can be modified by tuning the ionization degree of the polycations or polyanions, provided the film is made from weak polyelectrolytes. In most previous investigations, this was achieved by playing on the solution pH either during the film buildup or by a postbuildup pH modification. Herein we investigate the functionalization of poly(allylamine hydrochloride)/poly(glutamic acid) (PAH/PGA) multilayers by ferrocyanide and Prussian Blue (PB). We demonstrate that dynamic exchange processes between the film and polyelectrolyte solutions containing one of the component polyelectrolyte allow one to modify its Donnan potential and, as a consequence, the amount of ferrocyanide anions able to be retained in the PAH/PGA film. This ability of the film to be a tunable reservoir of ferrocyanide anions is then used to produce a composite film containing PB particles obtained by a single precipitation reaction with a solution containing Fe(3+) cations in contact with the film. The presence of PB in the PEM films then provides magnetic as well as electrochemical properties to the whole architecture.

Swelling of electrochemically active polyelectrolyte multilayers

“…Their diffusion constants can be determined by recoding the peak currents for different scanning rates in cyclovoltammograms (see Fig. 2B) [36,[50][51][52]. As an alternative, the electron hopping behavior in PEMs can be described by chronoamperometry and electrochemical impedance spectroscopy [39,53 • ].…”

Porous Carbons – Hyperbranched Polymers – Polymer Solvation

“…Hence, Prussian blue can be prepared inside the multilayers [480]. In another approach, the particles were prepared and co-assembled with a polyelectrolyte.…”

Organic and Inorganic Dyes in Polyelectrolyte Multilayer Films

“…This means that electroneutrality is ensured by the preferential incorporation of one type of ions from the electrolyte solution in contact with the film [65]. This property allows such “exponentially growing films” to behave as ion exchange membranes, allowing for instance the incorporation of “colored” redox probes [66,67,68], drugs [69] and dyes [70,71,72,73]. In the investigation published by Burke and Barrett [71], the (PAH-HA) 10 films, where HA represents hyaluronic acid, were deposited from solutions at pH 3 and the film swelling was investigated under the influence of a pH change.…”

“…Such a high concentration of incorporated species is not uncommon for polyelectrolyte multilayer films: The saturation concentration of hexacyanoferrrate anions in (PAH-PGA) n films is of the order of 1 mol L −1 [68]. The same kind of polyelectrolyte multilayer films made from poly( L -glutamic acid) and poly( L -lysine) were loaded with potassium hexacyanoferrate and zinc meso tetrakis(sulfonatophenyl) porphyrin and the obtained composite film was able to reduce C 60 in the organic solvent in contact with the immobilized dye and redox probe [75].…”