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The nature of solvation of Reichardt’s dye in ionic liquids is investigated through semiempirical calculations. We build on the basis of electrostatic considerations a cluster of three ionic pairs that represent the first solvation shell of the dye. The spatial organization of this shell is a balance between sterical, electrostatic and, in the case of functionalized ionic liquids, specific interactions. This model is not sufficient to obtain values of ET(30) quantitatively comparable to the experimental ones, but some qualitative features can be rationalized. The resulting scenario of solute–solvent interactions is different with respect to molecular solvents. Thus, we suggest caution in comparing ionic and molecular solvents through solvatochromic scales.

The fungal pathways of melanin synthesis have so far been little considered as a source of bio-inspiration in the field of functional materials, despite the interesting properties exhibited by Ascomycetes melanins from 1,8-dihydroxynaphthalene (1,8-DHN), including the ability to shield organisms from ionizing radiation. Herein, the processing techniques and characterizations of mycomelanin thin films obtained from the solid state polymerization of 1,8-DHN is reported for the first time. Overall, the results highlighted the role of synthetic mycomelanin thin films as a prototype of next generation bioinspired interfaces featuring high structural regularity and ultrasmooth morphology, high robustness against peroxidative bleaching and adhesion under water conditions, good biocompatibility and unprecedented effects in inducing the spontaneous differentiation of embryonic stem cells prevalently towards the endodermal lineages in the absence of added factors. These data open up new avenues towards the applications of this biomaterial in the fields of tissue engineering and regenerative medicine.

Despite the growing scientific and technological relevance of polydopamine (PDA), a eumelanin-like adhesive material widely used for surface functionalization and coating, knowledge of its structural and physicochemical properties, including in particular the origin of paramagnetic behavior, is still far from being complete. Herein, we disclose the unique ability of ionic liquids (ILs) to disassemble PDA, either as a suspension or as a thin film, up to the nanoscale, and to establish specific interactions with the free radical centers exposed by deaggregation of potential investigative value. Immersion of PDA-coated glasses into four different ILs ([C1C1im][(CH3O)HPO2], [C1C1im]- [(CH3O)CH3PO2], [C1C1im][(CH3O)2PO2], [N1888][C18:1]) at room temperature caused the fast and virtually complete removal of the coating as determined by UV−visible spectroscopy and scanning electron microscopy (SEM). Transmission electron microscopy (TEM) analysis of the colored supernatants from PDA suspensions in ILs revealed the presence of nanostructures not exceeding 50 nm in diameter. Electron paramagnetic resonance (EPR) analysis indicated profound IL-dependent modifications in signal intensity, line-width, and g-factor values of PDA. These differences were interpreted in terms of a partial conversion of C-centered radicals into O-centered semiquinone-type components following destacking and interaction with the anion component in ILs. The discovery of ILs as a powerful tool to disassemble PDA under mild conditions provides a new entry both to detailed investigations of this biopolymer on the nanoscale and to mild removal of coatings from functionalized surfaces, greatly expanding the scope of PDA-based surface functionalization strategies.