Ionic-Liquid-Based Acidic Aqueous Biphasic Systems for Simultaneous Leaching and Extraction of Metallic Ions.

The first instance of an acidic aqueous biphasic system (AcABS) based on tributyltetradecyl phosphonium chloride ([P44414 ][Cl]) and an acid is here reported. This AcABS exhibits pronounced thermomorphic behavior and is shown to be applicable to the extraction of metal ions from concentrated acidic solutions. Metal ions such as cobalt(II), iron(III), platinum(IV) and nickel(II) are found to partition preferentially to one of the phases of the acidic aqueous biphasic system and it is here shown that it successfully allows the difficult separation of CoII from NiII , here studied at 24 and 50 °C.

Possibilities and limitations in separating Pt(IV) from Pd(II) combining imidazolium and phosphonium ionic liquids.

An investigation on a process designed for separating Pt(IV) and Pd(II) dissolved in acidic aqueous solution containing HCl using two ionic liquids, 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([OMIM][NTf2]) and trihexyltetradecylphosphonium bromide (Cyphos 102), is presented. To this end, the single extraction of platinum in [OMIM][NTf2] has been investigated as a function of the initial concentration of Pt(IV) ions dissolved in 1 M HCl. The distribution coefficient for Pt(IV), present in water as a PtCl6(2-) anion, decreases with the concentration of Pt(IV). The extraction of Pd(II) towards [OMIM][NTf2] or Cyphos 102 as a function of the concentration of HCl in the aqueous phase is also reported. Pd(II), present as PdCl4(2-) in water, is not extracted using [OMIM][NTf2]. On the other hand, the distribution coefficients of Pd(II) using Cyphos 102 are above 2000. In this ionic liquid, Pd(II) is extracted as a PdBr4(2-) anion. Separation of Pt(IV) from Pd(II) was then carried out starting from aqueous phases containing 1 M HCl and various initial concentrations of Pt(IV). The influence of the number of extraction steps using [OMIM][NTf2] on the extraction of Pt(IV) was also studied. Unlike the results obtained from single extraction experiments of Pt(IV), consecutive extraction of Pt(IV) in water using [OMIM][NTf2] does not improve significantly the extraction of this metal ion. The second step of the extraction process carried out using Cyphos 102 leads to the quantitative extraction of Pd(II) and Pt(IV) remaining in the aqueous phase.

A Label-Free Impedimetric DNA Sensor Based on a Nanoporous SnO2 Film: Fabrication and Detection Performance.

Nanoporous SnO2 thin films were elaborated to serve as sensing electrodes for label-free DNA detection using electrochemical impedance spectroscopy (EIS). Films were deposited by an electrodeposition process (EDP). Then the non-Faradic EIS behaviour was thoroughly investigated during some different steps of functionalization up to DNA hybridization. The results have shown a systematic decrease of the impedance upon DNA hybridization. The impedance decrease is attributed to an enhanced penetration of ionic species within the film volume. Besides, the comparison of impedance variations upon DNA hybridization between the liquid and vapour phase processes for organosilane (APTES) grafting on the nanoporous SnO2 films showed that vapour-phase method is more efficient. This is due to the fact that the vapour is more effective than the solution in penetrating the nanopores of the films. As a result, the DNA sensors built from vapour-treated silane layer exhibit a higher sensitivity than those produced from liquid-treated silane, in the range of tested target DNA concentration going to 10 nM. Finally, the impedance and fluorescence response signals strongly depend on the types of target DNA molecules, demonstrating a high selectivity of the process on nanoporous SnO2 films.

Electrochemical deposition of platinum nanoparticles on carbon: a study by standard and anomalous X-ray diffraction.

This paper is devoted to an alternative method to characterize platinum nanoparticles: X-ray powder diffraction with synchrotron radiation in classical and anomalous dispersion modes. We could straightforwardly determine the mean diameter and the surface concentration of carbon-supported platinum nanoparticles, even down to diameters of 2-3 nm and catalyst amounts of 0.03 mgcm(-2). We could study early stages of the formation of electrochemically prepared platinum nanoparticles from [PtCl4(2-) species preadsorbed on carbon inside a carbon-Nafion layer, to obtain a fuel-cell electrode. Our X-ray diffraction (XRD) results demonstrate that, provided the superficial concentration is not too high, new and smaller particles appear for each current pulse, since there is not any strong nucleation limitation for the high overvoltages obtained. Hydrogen evolution becomes the main electrochemical phenomenon on particles of sufficient size and it explains the noteworthy size limitation. Better yields of Pt metal are obtained for smaller current densities and longer times: the rate-determining step is then not electrochemical, but chemical or related to superficial diffusion.