New type of nanoparticles, nanomicelles formed in water-saturated organic solutions of HFeCl4 and HClO4: Composition, structure and properties

Abstract

It has been shown, by IR spectroscopy, that two types of nanomicelles are formed in water-saturated tributylphosphate (TBP) containing HFeCl₄ or HClO₄. Nanomicelles of type A contain one HAn molecule, whereas nanomicelles of type B contain up to 3–4 HAn molecules. Unlike classic micelles, nanomicelles A and B have a stable, almost stoichiometric, composition. The core of type A contains 26 or 30 H₂O molecules and one H₅O₂⁺ cation. Two protons of H₅O₂⁺ are bonded to two TBP molecules from the solvate shell around the core. The first and second hydrate shells are formed around the other two protons from six water molecules inequivalent to the other water molecules of the core. The FeCl₄⁻ anion is located in the solvate shell from a bimolecular layer of TBP molecules, whereas ClO₄⁻ contacts with the core. The composition and structure of type B with different numbers of incorporated HAn molecules has been determined. The polarizing effect of the ClO₄⁻ anion on the H₅O₂⁺ cation has been found to be sufficiently strong to be detectable in the IR spectra only in nanomicelles B containing HClO₄ molecules. In this case the effect of the anion is experienced even by 2 TBP and 2 H₂O molecules from the first coordination sphere of H₅O₂⁺. Possible explanations for the ease of formation of mixed (HCl+HFeCl₄) nanomicelles are discussed.