Composite Materials and Films Based on Melanins, Polydopamine, and Other Catecholamine-Based Materials

Abstract

Polydopamine (PDA) is related to eumelanins in its composition and structure. These pigments allow the design, inspired by natural materials, of composite nanoparticles and films for applications in the field of energy conversion and the design of biomaterials. This short review summarizes the main advances in the design of PDA-based composites with inorganic and organic materials.

Keywords: composite films; core-shell nanoparticles; melanin; polydopamine.

Figure 1

Transmission electron microscopy (TEM) images and corresponding particle size distribution histograms of (a) Pt-decorated multi-walled carbon nanotubes (Pt/MWNTs) and (b) Pt/MWNTs with polydopamine (Pt/MWNTs-PDA) catalysts used in the design of polyelectrolyte membrane-based fuel cells. (c) Polarization and (d) power density curves of fuel cell (Pt/MWNTs)₅₀ and (Pt/MWNTs-PDA)₅₀. The composite membranes were produced by 50 spray cycles on a hot substrate. Reprinted from [22], Copyright (2016), with permission from Elsevier.

Figure 2

Composites obtained by adding Alcyan Blue (AB) in an oxygenated dopamine solution as shown at the top. (a) Digital pictures of glass slides after being put in dopamine–AB blends with AB concentrations of 0.05, 0.1, and 0.2 mM after 1, 3, and 24 h of reaction. The dopamine concentration was the same, 10.6 mM, in all experiments and the films were deposited from 50 mM Tris buffer at pH 8.5 using dissolved O₂ as the oxidant. (b) Ultraviolet-visible (UV-Vis) spectra taken on quartz slides put in dopamine–AB mixtures after 3 h of reaction and increasing the AB concentration from 0.05 to 0.2 mM as indicated in the inset. (c) UV-Vis spectra taken on quartz slides put in dopamine–AB mixtures after 24 h of reaction and increasing the AB concentration from 0.05 to 0.2 mM as indicated in the inset. (d) Evolution with time of the Cu/C (●) and the C/N (▲) ratios for the polydopamine (PDA)–AB (0.1 mM) films, and the C/N (■) ratio for the PDA films. These atomic ratios are obtained from X-ray photoelectron spectroscopy (XPS). Reprinted from [36], Copyright (2015), with permission from Elsevier.

Figure 3

Layer-by-layer deposition of clay and poly(allylamine hydrochloride) (PAH) followed by post-modification with polydopamine. (a) Cross-sectional scanning electron microscope (SEM) image of a poly(allylamine hydrochloride)–montmorillonite (PAH-MMT)₁₅@polydopamine-coated film obtained after 14 h of contact with dopamine (2 mg mL⁻¹) in oxidizing conditions (pH = 8.5, O₂ as the oxidant). (b) X-ray diffractogram of the MMT powder (^____) of (PAH–MMT)₁₅ film before (^____) and after (^____) 14 h of contact with dopamine in oxidizing conditions. (c) Cyclic voltammetry (at a potential scan rate of 100 mV s⁻¹) measured on a pristine amorphous carbon electrode (^____), on the same electrode covered with a (PAH-MMT)₁₀–PAH film (^____) and after 14 h of dopamine oxidation (^____). The redox probe was 1 mM K₄Fe(CN)₆ dissolved in 50 mM Tris buffer + 150 mM NaCl (pH = 8.5). (d) Surface topography over (1 µm × 1 µm) of (PAH–MMT)₁₀ and (PAH–MMT)₁₀@polydopamine films and distribution of their corresponding elastic moduli. Reproduced with permission from [43].

Figure 4

Variation of the hydrodynamic diameter of polydopamine (PDA) particles, as measured by dynamic light scattering; with the concentration of human serum albumin (HSA) added in the dopamine solution (10.6 mM in the presence of 50 mM Tris buffer at pH = 8.5). Dopamine has been oxidized with dissolved O₂ (open vessel) for 24 h at room temperature before the measurement. Reprinted from [52], Copyright (2014), with permission from Elsevier. The inset (personal data from the author) represents a transmission electron micrograph of the PDA suspension obtained in the presence of HSA at 1 mg mL⁻¹.

Figure 5

Composite alginate–catechol@polydopamine membranes. (a) Images showing the responsivity of PDA-alginate–catechol (PDA-Algcat) membranes to the addition of water. (b) Scanning electron microscopy (SEM) images of the dry membrane obtained from an Algcat solution at 20 mg mL⁻¹ and (c) its UV-Vis spectrum. ABS: Absorbance. (d) Pull-off data of a PDA-Algcat membrane at different concentrations of Algcat depending on the side of the membrane (30% relative humidity), and (e) pull-off data as a function of the relative humidity. Reprinted from [61]. Copyright (2017) American Chemical Society.

Figure 6

Influence of the presence of dopamine in pyrrole solutions on the properties of the obtained particles. (a) Particle size as determined by dynamic light scattering and films; (b) Peak force in peeling tests; (c) Electrical conductivity after polymerization in the presence of ammonium persulfate. Pyrrole and dopamine structures are shown at the top. Adapted with permission from [68].