Carboxylated poly(amidoamine) PAMAM dendrimers (generation 4.5) have been utilized for the synthesis and stabilization of ferrimagnetic iron oxide nanoparticles. Oxidation of Fe(II) at slightly elevated pH and temperature results in the formation of highly soluble nanocomposites of iron oxides and dendrimer, which are stable under a wide range of temperatures and pH's. Size exclusion chromatography indicates aggregates in the 20-30-nm size regime, consistent with the oligomeric nature of the composite material. Transmission electron microscopy reveals small assemblies of mineral cores with electron diffraction and high-resolution TEM data, indicative of the mineral maghemite. SQUID magnetometry demonstrated that this crystalline composition exhibited superparamagnetism at room temperature. NMR relaxation studies of solvent (water) protons revealed unusually high T1 and T2 relaxivities, which make these materials excellent candidates as contrast agents for MR imaging.

No abstract

Single crystals of Bis(thiourea) cadmium chloride (BTCC), and Tris(thiourea) zinc sulphate (TZnS) have been grown from saturated aqueous solution by slow evaporation method at room temperature. The laser b a n and FT-IR spectra on these crystals are recorded in the frequency range 50-4000cm-'. The spectral data of BTCC and TZnS are interpreted on the basis of thiourea crystal vibrational data. The vibrational frequencies in the FT-IFt &d Raman spectra of BTCC and TZnS establish that ZnSOr and CdClz metal complex are coordinated with thiourea by the metal to sulfur bonds. The effect of the metal complexation on thiourea molecule and nature of bands due to different vibrational modes have been discussed. The lattice vibrational frequencies changes have also been observed and analyzed.