A new sensitive organic/inorganic hybrid material based on titanium oxide for the potentiometric detection of iron(III).

The formation of a new hybrid material based on titanium dioxide as inorganic support and containing an iron organochelator (ICL670) is described. An organophosphorous coupling agent was used to graft the organic molecule on the oxide surface. The attachment of the organic substrate was well-confirmed by FTIR (DRIFT), solid-state (31)P and (13)C CPMAS NMR, thermal analysis and the integrity of the structural and morphological parameters were verified using XRD and TEM analyses. The interaction between the material and dissolved iron(III) was also investigated through potentiometric measurements and demonstrated the interest of this new non-siliceous based hybrid material. The obtained linear evolution of the open circuit potential from 10(-2) to 10(-6) mol L(-1) can be used for the analytical detection of iron(III).

Insights into the potentiometric response behaviour vs. Li+ of LiFePO4 thin films in aqueous medium.

The potentiometric response of PLD-made LiFePO(4) thin films versus Li(+) ions in aqueous solutions has been investigated, and a sensitivity of 54 mV dec(-1) has been observed in a Li(+) concentration range of 1-10(-4) M. Physical and electrochemical measurements of electrodes aged in aqueous medium show a slight surface oxidation with formation of heterosite-FePO(4) that we show to be responsible for the stable potential response measured. Cyclic voltamperometry measurements operated in different Li(+) concentration clearly highlight the key relation between the material lithium ion insertion/de-insertion capability and its potentiometric sensing response implying a faradaic-governed sensing mechanism. Based on such a finding, selection criteria (enlisting among others the potential of the redox couple, the nature of the insertion process) are herein underlined in the search for new sensitive materials.

Study of the insertion/deinsertion mechanism of sodium into Na0.44MnO2.

Pure Na0.44MnO2 samples were prepared via a solid-state route by carefully tuning the synthesis conditions. Insertion/deinsertion of sodium into the well-crystallized particles leads to capacities as high as 140 mA.h/g. A potentiostatic intermittent titration technic, together with in situ X-ray diffraction measurements, enabled us to evidence the presence of six biphasic transitions within a potential range of 2-3.8 V (vs Na+/Na). The insertion process within the NaxMnO2 system is fully reversible over the 0.25 < x < 0.65 composition range and presents some degree of irreversibility as values of x below 0.25 are reached. Furthermore, we similarly showed that HCl treatment has a detrimental effect on these electrochemical properties because of structural and textural evolutions.