Ethylammonium nitrate (ionic liquid) based ferrofluids with citrate-coated nanoparticles and Na ${}^{+}$ counterions were synthesized for a wide range of nanoparticle (NP) volume fractions ( $\mathsf{\Phi }$ ) of up to 16%. Detailed structural analyses on these fluids were performed using magneto-optical birefringence and small angle X-ray scattering (SAXS) methods. Furthermore, the thermophoretic and thermodiffusive properties (Soret coefficient $S_{\mathrm{T}}$ and diffusion coefficient $D_{\mathrm{m}}$ ) were explored by forced Rayleigh scattering experiments as a function of T and $\mathsf{\Phi }$ . They were compared to the thermoelectric potential (Seebeck coefficient, Se) properties induced in these fluids. The results were analyzed using a modified theoretical model on $S_{\mathrm{T}}$ and Se adapted from an existing model developed for dispersions in more standard polar media which allows the determination of the Eastman entropy of transfer ( ${\widehat{S}}_{\mathrm{NP}}$ ) and the effective charge ( $Z_0^{eff}$ ) of the nanoparticles.

Dispersions of charged maghemite nanoparticles (NPs) in EAN (ethylammonium nitrate) a reference Ionic Liquid (IL) are studied here using a number of static and dynamical experimental techniques; small angle scattering (SAS) of X-rays and of neutrons, dynamical light scattering and forced Rayleigh scattering. Particular insight is provided regarding the importance of tuning the ionic species present at the NP/IL interface. In this work we compare the effect of Li⁺, Na⁺ or Rb⁺ ions. Here, the nature of these species has a clear influence on the short-range spatial organisation of the ions at the interface and thus on the colloidal stability of the dispersions, governing both the NP/NP and NP/IL interactions, which are both evaluated here. The overall NP/NP interaction is either attractive or repulsive. It is characterised by determining, thanks to the SAS techniques, the second virial coefficient A₂, which is found to be independent of temperature. The NP/IL interaction is featured by the dynamical effective charge ξ^eff ₀ of the NPs and by their entropy of transfer Ŝ_NP (or equivalently their heat of transport ) determined here thanks to thermoelectric and thermodiffusive measurements. For repulsive systems, an activated process rules the temperature dependence of these two latter quantities.

One dimensional magnetic nanochains (MNCs) of FeNi3 alloy is developed by reducing iron and nickel salts in ethylene glycol in a hydrothermal environment without the use of any external magnetic field or template. The as prepared nanochains, comprised of nanospheres of diameter 350 nm, exhibit an extraordinary length of around 2 µm. The he self assembly of the FeNi3 nanospheres is attributed to strong dipolar interaction. Hydrophilic to hydrophobic surface transformation achieved by using trimethoxysilane and stearic acid, also introduces oleophilicity to the MNCs. After surface modification, the hydrophobic and oleophilic MNCs shows quick and selective absorption of oils from water surface under the influence of magnetic field.