Supramolecular hydrogels formed through non-covalent interactions of low molecular weight hydrogelators (LMWH) show great potential applications in different fields, such as delivery of therapeutics, injectable biomaterials, catalysis or materials chemistry. Generally, the self-assembly of LMWH is triggered by a sol-gel process through an external stimulus able to switch their solubility, such as temperature, pH or solvent change and chemical or enzymatic reactions. In this work, we introduced a new strategy to trigger and control the self-assembly of Fmoc-FFpY peptides: by direct electrostatic interactions with a polycation without dephosphorylation of the peptides. The resulting hydrogels show enhanced mechanical properties in comparison to gels of Fmoc-FFpY induced by enzymatic dephosphorylation. Peptide self-assembly yields -sheets, revealed by circular dichroism and infrared spectroscopy. Characteristic distances predicted by geometry optimization in the gas phase are in agreement with X-ray scattering data and TEM observations. It is proposed that core-shell cylinders are formed in which polycation chains decorate the micellar structures of Fmoc-FFpY peptides through electrostatic interactions between the charged amine groups of the polycations and the phosphate groups of the peptides. Since the gels form quickly and have superior mechanical properties, applications as injectable biomaterials are foreseen. This work opens a route towards a new class of self-assembled hydrogels, where Fmoc tripeptides can be self-assembled with specific polycations to obtain, for example, antimicrobial hydrogels.

In the present paper we describe a phase transfer of aqueous synthesized gold nanoparticles (AuNPs) from water to toluene using secondary amines: dioctylamine, didodecylamine, and dioctadecylamine. The effect of the hydrocarbon chain length and amount of amines on the transfer efficiency were investigated in the case of nanoparticles (NPs) with three different sizes: 5, 9, and 13 nm. Aqueous colloids were precisely characterized before the transfer process using UV-vis spectroscopy, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). Nanoparticles were next transferred to toluene and characterized using UV-vis and DLS techniques. It was found that dioctadecylamine provides the most effective transfer of nanoparticles. No time-dependent changes in the NP size were observed after 12 days, showing that the dioctadecylamine-stabilized nanoparticles dispersed in toluene were stable. This indicates that long hydrocarbon chains of dioctadecylamine exhibit sufficiently hydrophobic properties of nanoparticles and consequently their good dispersibility in nonpolar solvent.