EPR and SAXS studies of a TiO2-based gel

The response of a photosensitive TiO2-based gel to UV light is described. Upon irradiation, the gel adsorbs light at 365 nm and becomes dark blue due to the transformation of the Ti4+ centers into Ti3+. This behavior is revealed using electron paramagnetic resonance spectroscopy as a function of the gel chemical composition. The structure of the TiO2 network is studied by small angle x-ray scattering

Magnetic behaviour of nickel-cyclam complexes in mesoporous silica: EPR investigations

International audienceElectron paramagnetic resonance (EPR) investigations are carried out on mesoporous silica (SBA15) functionalized by Ni-cyclam complexes (1,4,8,11-tetraazacyclotetradecane groups chelating nickel ions). The magnetic behaviour of nickel-cyclam groups, their mutual interactions and dispersions in the mesoporous silica are compared with respect to the doping rates and the synthesis procedures. The spin–spin interactions and the relaxation processes were clarified from the thermal evolution in the temperature range (4 K, 300 K) of the paramagnetic spin susceptibilities and EPR line widths. Thus, the relaxation mechanisms seem marked by the Jahn–Teller effect on the nickel ions mediated by exchange interactions between nearest spins. Isolated Ni-cyclam molecules are involved in some samples while others show the formation of clusters where phonon-assisted one-dimensional (1D) ferromagnetic ordering occurs below 45 K. The performed experiments point out the efficiency of the EPR technique to probe the degree of functionalization of mesoporous silica by Ni-cyclam molecules and to give valuable feedback to improve the synthesis routes

EPR in functional structures based on doped (nano, meso)- porous silica and titanium dioxide

International audienc

SiC nanocrystals embedded in polymer matrix : a new electro-optical nanocomposite

International audienc