Conductance and Ionic Association of Imidazolium-Based Ionic Liquids in <i>N</i>,<i>N</i>‑Dimethylacetamide

The electrical conductivity of dilute solutions of the ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate [emim]­[BF₄] and 1-butyl-3-methylimidazolium tetrafluoroborate [bmim]­[BF₄] in <i>N</i>,<i>N</i>-dimethylacetamide (DMA) have been measured over the temperature range from (283.15 to 318.15) K. The conductance data was analyzed using the low concentration Chemical Model (lcCM) in terms of the ionic association constant, <i>K</i>_A, the limiting molar conductivities, Λ_o, and distance parameters, <i>R</i>. Slight ionic association was found for the ionic liquids in DMA within the investigated temperature range. From the temperature dependence of the limiting molar conductivities the Eyring activation enthalpy of charge transport was designated. The thermodynamic parameters such as Gibbs free energy, entropy, and enthalpy for the process of ion pair formation were estimated from the ion association constants at various temperatures. The obtained results were compared with those in <i>N</i>,<i>N</i>-dimethylformamide

Viscosity coefficients of KCl, NaCl, NaI, KNO₃, LiNO₃, NaBPh₄ and Bu₄NI in water-rich binary mixtures containing propan-2-ol at 298.15 K

<p>Viscosities of KCl, NaCl, NaI, KNO₃, LiNO₃, NaBPh₄ and Bu₄NI solutions (from ~0.01 M to ~0.05 M) in water (1) + propan-2-ol) (2) binary mixtures with mole fractions of propan-2-ol, <i>x</i>₂ = 0.01, 0.02, 0.05, 0.075, 0.10 and 0.15, were determined at 298. 15 K. The relative viscosity data have been analysed and interpreted in terms of the Jones–Dole equation, <i>η</i>_r = <i>A</i>∙<i>c</i>^1/2 + <i>B</i>∙<i>c</i>. The obtained results allowed to determine the values of <i>B</i>_± coefficients for individual ions using the assumption about the equality . All the results presented in this article have been discussed in terms of ion–solvent interactions.</p

Effect of the Alkyl Chain Length of Secondary Amines on the Phase Transfer of Gold Nanoparticles from Water to Toluene

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