Melanin‐Containing Films: Growth from Dopamine Solutions versus Layer‐by‐Layer Deposition

Abstract

Films formed by oxidation of dopamine are of interest for functionalisation of solid-liquid interfaces owing to their versatility. However, the ability to modulate the properties of such films, for example, permeability to ionic species and the absorption coefficient, is urgently needed. Indeed, melanin films produced by oxidation of dopamine absorb strongly over the whole UV/Vis part of the electromagnetic spectrum and are impermeable to anions even for a film thickness as low as a few nanometers. Herein we combine oxidation of dopamine to produce a solution containing dopamine-melanin particles and their alternating deposition with poly(diallyldimethylammonium chloride) to produce films which have nearly the same morphology as pure dopamine-melanin films but are less compact, more transparent and more permeable to ferrocyanide anions.

Kinetics of polydopamine film deposition as a function of pH and dopamine concentration: Insights in the polydopamine deposition mechanism

“…Indeed, rough films induce important light scattering, which not only reduces the intensity of the reflected light but also may induce some changes in the polarization of the reflected light. Nevertheless, we have already shown, in the case of films prepared at 2 g L À1 , that the thickness determined by ellipsometry is close (within 10%) to that determined by AFM on scratched films [37].…”

“…5 of Ref. [37]). In order to know whether such aggregates contribute to the deposition of polydopamine films, we did two experiments.…”

Morphological and Chemical Composition Characterization of Commercial Sepia Melanin

“…Due to the presence of melanin polymer in sepia ink, sepia ink possesses antimicrobial activity [14]. Melanin coating is model of coating for both biological investigations and smart surface science [15].…”

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

“…The films prepared by oxidation of dopamine using O 2 as the oxidant had an extinction coefficient of (2.6±0.4)×10 6 m −1 [74] at 589 nm in close agreement with the values obtained by the group of Bothma et al [38]. The extinction coefficient of the films could be reduced by a factor of two when melanin particles (also produced by oxygen mediated oxidation of a 2-mg mL −1 buffered dopamine solution) were deposited on the quartz substrate in a layer-by-layer approach using poly (diallyldimethyl ammonium chloride) as the polycation [74]. Photopyroelectric spectroscopy was performed on electropolymerized melanin films.…”