In this paper, we report the synthesis of size-controlled (6 and 18 nm) monodisperse magnetic iron oxide nanoparticles, from the pyrolysis of iron oxyhydroxide with oleic acid in high temperature solvents. Superconducting Quantum Interface Device (SQUID) measurements revealed that the iron oxide nanoparticles exhibit a superparamagnetic behavior at room temperature. In order to evaluate their potential applications as contrast agents in Nuclear Magnetic Resonance (NMR) imaging, we investigated using 1H NMR spectroscopy (at a magnetic field 4.7 T) the changes in $T_1$ and $T_2$ relaxation times in the colloidal aqueous solution at various concentration of nanoparticles. The following transverse ($r_2$) and longitudinal ($r_1$) relaxivities were found: ($r_2 = 17.85 mM^{-1}s^{-1}, r_1 = 6.90 mM^{-1}s^{-1}$) and($r_2 = 9.20 mM^{-1}s^{-1}, r_1 = 4.30 mM^{-1}s^{-1}$) for nanoparticle sizes of 18 and 6 nm, respectively. These results confirm that the synthesized nanoparticles have both high $r_1$ and $r_2$ relaxivities and thus the capacity for positive or negative contrast enhancement. This effect increaseswith the nanoparticle size. We also developed a new recognition motif of a saccharide type (mannose coating) for targeting biological models (plants) at the tissue and cellular levels in order to track the flow of the water and saccharide (which are the main drivers of plant growth) in NMR imaging. Moreover, we demonstrated that this saccharide motif provides good biocompatibility and biodistribution in a physiological medium

Our study concerns nano-objects consisting in an iron oxide core of 10(±2) nm or 20(±5) nm size, which exhibit superparamagnetic behavior, whose shell is constituted of dendrons carrying a dye. The characterization of the magnetic properties of these nano-objects together with their relaxivity into MRI will be presented in this poster. Their detection in an intraoperative context requires an instrument able to detect the extremely weak magnetic signature of the superparamagnetic nanoparticle in a noisy environment. A magnetic probe based on an AC magnetic field excitation of the nano-object coupled to an inductive gradiometer sensor has been designed to achieve this measurement. A conductive layer surrounding the probe is used to provide a shielding, thanks to the eddy current which will limit the leakage magnetic field outside of the probe. The principle of the probe and its ability to measure the magnetic signature of the magnetic nano-objects will be discussed.

Nondestructive studies of physiological processes in agronomic products require increasingly higher spatial and temporal resolutions. Nuclear Magnetic Resonance (NMR) imaging is a non-invasive technique providing physiological and morphological information on biological tissues. The aim of this study was to design a robust and accurate quantitative measurement method based on NMR imaging combined with contrast agent (CA) for mapping and quantifying water transport in growing cherry tomato fruits. A multiple flip-angle Spoiled Gradient Echo (SGE) imaging sequence was used to evaluate the intrinsic parameters maps M0 and T1 of the fruit tissues. Water transport and paths flow were monitored using Gd3+/[Fe(CN)6]3−/D − mannitol nanoparticles as a tracer. This dynamic study was carried out using a compartmental modeling. The CA was preferentially accumulated in the surrounding tissues of columella and in the seed envelopes. The total quantities and the average volume flow of water estimated are: 198 mg, 1.76 mm3/h for the columella and 326 mg, 2.91 mm3/h for the seed envelopes. We demonstrate in this paper that the NMR imaging technique coupled with efficient and biocompatible CA in physiological medium has the potential to become a major tool in plant physiology research.

Le principe de la RMN/IRM est basé sur la détection du spin d’un noyau atomique par exemple le 13C, 31P et le proton 1H. L'échantillon est placé dans un champ magnétique statique (4.7 Tesla) qui polarise les spins. L’aimantation est basculée par des impulsions radiofréquences (200MHz, longueur d’onde de l’ordre du mètre). La relaxation de l'aimantation génère un champ électromagnétique à la fréquence de Larmor qui est détecté par une antenne de réception. Dans notre cas, nous utilisons une sonde de taille micrométrique que nous positionnons à une distance sublongueur d’onde de l’objet. Nous sommes donc en champ proche et donc dans les conditions de détection des ondes évanescentes. Notre dispositif nouveau dans la RMN/IRM collecte du champ proche électrique à travers un couplage capacitif et non inductif comme cela se fait classiquement. Ce système a une détection localisée au voisinage de sa pointe.

The local magnetic properties of the one dimensional inner space of the nanotubes are investigated using 13C nuclear magnetic resonance spectroscopy of encapsulated fullerene molecules inside single walled carbon nanotubes. Isotope engineering and magnetically purified nanotubes have been advantageously used on our study to discriminate between the different diamagnetic and paramagnetic shifts of the resonances. Ring currents originating from the π electrons circulating on the nanotube, are found to actively screen the applied magnetic field by −36.9 ppm. Defects and holes in the nanotube walls cancel this screening locally. What is interesting, that at high magnetic fields, the modifications of the NMR resonances of the molecules from free to encapsulated can be exploited to determine some structural characteristics of the surrounding nanotubes, never observed experimentally.

In the present study, we investigated Cs-intercalated single wall carbon nanotubes (SWCNTs) using 133Cs Nuclear Magnetic resonance. We show that there are two types of Cs cations depending on the insertion level. Indeed, at low concentrations, Static spectra analysis shows that the Cs(α)+ species are fully ionized, i.e. α equal ca.1, while at higher concentrations a second paramagnetically shifted line appears, indicating the formation of Cs(β)+ ions with β < α ∼ +1. At low concentrations and low temperatures the Cs(α)+ ions exhibit a weak hyperfine coupling to the SWCNT conduction electrons, whereas, at higher temperatures, a thermally activated slow-motion diffusion process of the Cs(α)+ ions occurs along the interstitial channels present within the carbon nanotube bundles. At high concentrations, the Cs(β)+ ions seem to occupy well defined positions relative to the carbon lattice. As a matter of fact, the Korringa relaxation behavior suggests a strong hyperfine coupling between Cs nuclei and conduction electrons in the carbon nanotubes and a partial charge transfer, which suggest a plausible Cs(6s)-C(2p) hybridization.