Heterogeneous Oriented Structure model of thermoelectric transport in conducting polymers.

Understanding transport phenomena in conducting polymers (CP) is a main issue in order to optimize their performance and despite intense investigations, the influence of their microstructure remains controversial. By analyzing the thermoelectric measurements performed on highly oriented and non-oriented CP films, we show that an Heterogeneous Oriented Structure (HOSt) model considering both ordered and disordered domains is able to account for the thermoelectric transport in CP. This model unveils the key role of the crystallinity, the anisotropy and the alignment degree of these domains.

Thermopower, figure of merit and Fermi integrals.

The thermoelectric efficiency accounting for the conversion of thermal energy into electricity is usually given by the figure of merit which involves three transport coefficients, with the thermopower, the electrical and the thermal conductivities. These coefficients can be defined at a semi-classical level as a function of Fermi integrals which only allow analytical approximations in either highly degenerate or strongly non-degenerate regimes. Otherwise, the intermediate regime which is of interest in order to describe high thermoelectric performance requires numerical calculations.

Thermopower scaling in conducting polymers.

By directly converting heat into electricity, thermoelectric effects provide a unique physical process from heat waste to energy harvesting. Requiring the highest possible power factor defined as ασ, with the thermopower α and the electrical conductivity σ, such a technology necessitates the best knowledge of transport phenomena in order to be able to control and optimize both α and σ. While conducting polymers have already demonstrated their great potentiality with enhanced thermoelectric performance, the full understanding of the transport mechanisms in these compounds is still lacking.

The development of stable aqueous suspensions of PEGylated SPIONs for biomedical applications.

We report here the development of stable aqueous suspensions of biocompatible superparamagnetic iron oxide nanoparticles (SPIONs). These so-called ferrofluids are useful in a large spectrum of modern biomedical applications, including novel diagnostic tools and targeted therapeutics. In order to provide prolonged circulation times for the nanoparticles in vivo, the initial iron oxide nanoparticles were coated with a biocompatible polymer poly(ethylene glycol) (PEG).

Scaling behavior in thermoelectric misfit cobalt oxides.

We investigate both thermoelectric and thermodynamic properties of the misfit cobalt oxide [Bi1.7Co0.3Ca2O4]RS0.

Structural organization of pi conjugated highly luminescent molecular material.

We report on striking evidence for a room temperature structural phase instability in p-hexaphenyl, inducing a nonplanar conformation of the molecules. Solid state proton NMR and single crystal x-ray diffraction allow the analysis of the organization, the individual dynamics and the involved symmetry breaking. The analysis of Raman spectra above and below room temperature reveals a singular behavior suggesting a modification of the overlap between the electronic wave function induced by the nonplanarity.

Universality and critical behavior at the Mott transition.

We report conductivity measurements of Cr-doped V2O3 using a variable pressure technique. The critical behavior of the conductivity near the Mott insulator to metal critical endpoint is investigated in detail as a function of pressure and temperature. The critical exponents are determined, as well as the scaling function associated with the equation of state.

Mott transition and transport crossovers in the organic compound kappa-(BEDT-TTF)2Cu[N(CN)2]Cl.

We have performed in-plane transport measurements on the two-dimensional organic salt kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl. A variable (gas) pressure technique allows for a detailed study of the changes in conductivity through the insulator-to-metal transition. We identify four different transport regimes as a function of pressure and temperature (corresponding to insulating, semiconducting, "bad metal," and strongly correlated Fermi-liquid behaviors).