Tip enhanced Raman spectroscopy imaging of opaque samples in organic liquid.

Implementation of Tip Enhanced Raman Spectroscopy in liquid is still a challenge. We demonstrate herein its feasibility in an upright illumination/collection configuration. Through a thin layer of organic solvent covering the sample, laser focussing on the tip is possible, enabling TERS imaging in liquid.

IR near-field spectroscopy and imaging of single Li(x)FePO4 microcrystals.

This study demonstrates the unique capability of infrared near-field nanoscopy combined with Fourier transform infrared spectroscopy to map phase distributions in microcrystals of Li(x)FePO4, a positive electrode material for Li-ion batteries. Ex situ nanoscale IR imaging provides direct evidence for the coexistence of LiFePO4 and FePO4 phases in partially delithiated single-crystal microparticles. A quantitative three-dimensional tomographic reconstruction of the phase distribution within a single microcrystal provides new insights into the phase transformation and/or relaxation mechanism, revealing a FePO4 shell surrounding a diamond-shaped LiFePO4 inner core, gradually shrinking in size and vanishing upon delithiation of the crystal. The observed phase propagation pattern supports recent functional models of LiFePO4 operation relating electrochemical performance to material design. This work demonstrates the remarkable potential of near-field optical techniques for the characterization of electrochemical materials and interfaces.

Calcium oxalate precipitation by diffusion using laminar microfluidics: toward a biomimetic model of pathological microcalcifications.

The effect of mixing calcium and oxalate precursors by diffusion at miscible liquid interfaces on calcium oxalate crystalline phases, and in physiological conditions (concentrations and flow rates), is studied using a microfluidic channel. This channel has similar dimensions as the collection duct in human kidneys and serves as a biomimetic model in order to understand the formation of pathological microcalcifications.

Reactivity of nanocolloidal particles gamma-Fe2O3 at the charged interfaces. Part 1. The approach of particles to an electrode.

We are interested here in the reactivity of magnetic nanoparticles at the electrode-electrolyte interface with the aim of the electrochemical synthesis of magnetic and conductive liquids (electronic conduction). The reactivity of charged colloidal particles occurs through a two steps process, the first being the approach toward the electrode with a possible adsorption phenomenon and the second step, the electron transfer. In this first paper we focus on the approach and the deposition of well-defined gamma-Fe(2)O(3) nanoparticles onto conductive substrates like mercury and gold under different conditions in order to vary the interactions particle/substrate especially the electrostatic interactions. The approach of the particles near the electrodes is estimated from the electrochemical currents related to the transformation of the particles. This electrochemical method is validated by coupling several techniques on gold electrodes: direct imaging by atomic force microscopy and study of kinetics by reflectometry. The results show that the electrochemical currents are always associated to adsorption of the particles, so that the electrochemical method can be used to estimate the adsorption of the particles, thus to follow the kinetics. The influence of the electrostatics on the occurrence of adsorption highly depends on the nature of the substrate and on the nature of the colloidal suspension. (ions, pH, ionic strength): whereas electrostatics governs the deposits in some cases, it is totally dominated by other interactions in other cases. Therefore, it seems difficult to predict a priori the existence of adsorption. However, when a deposit occurs, the kinetics and the maximal coverage of the substrates are controlled by the electrostatic interactions between the particles already adsorbed and those, close to the interface, in the bulk of the solution.

Reactivity of nanocolloidal particles gamma-Fe2O3 at charged interfaces. Part 2. Electrochemical conversion. Role of the electrode material.

In this paper we are interested in the reactivity of magnetic nanoparticles at the electrode involved in the electrochemical synthesis of magnetic and conductive liquids. The reactivity of charged colloidal particles occurs in two steps, first the approach toward the electrode with a possible adsorption phenomenon and secondly the electron transfer. In this paper we focus on the electrochemical behaviour of well-defined gamma-Fe(2)O(3) nanoparticles at a gold and at a mercury electrode. Particles can be electrochemically reduced at the two electrodes and can be dispersed into mercury at a highly negative potential. Here, we probe in particular the properties of nanoreactor of the particles, that is to say, the possible conservation of their size after they have undergone the electrochemical process. By correlating complementary techniques (here atomic force microscopy (AFM) observations, Raman spectroscopy and cyclic voltammetry on gold electrode) and by studying the magnetic properties of the material obtained after reduction of the particles on a mercury electrode, we are able to probe both the chemical nature and the physical state of the particles once transformed. Experimental results show that under specific conditions, the particles are individually converted into iron, which justifies their use for preparing a liquid with both magnetic properties and properties of electron conduction.