Magnetic and structural characterization of thiol capped ferromagnetic Ag nanoparticles

Dodecanethiol capped Ag nanoparticles (NPs) have been independently synthesized by the well-known Brust method under the same physical-chemical conditions. The obtained NP present similar sizes ( ∼ 2 nm) but different magnetic behaviors. The extended x-ray absorption fine structure analyses at the K-edge of Ag did not reveal any noticeable structural nor topological differences among the samples. In clear contrast with the structure provided for thiol capped ferromagnetic Au NPs, the analysis also brings out the existence of Ag–S bonds in a diffuse region surrounding a reduced Ag core where the magnetism of the Ag NPs would be located. This record was migrated from the OpenDepot repository service in June, 2017 before shutting down

Towards the design of contrast enhanced agents systematic Ga3 doping on magnetite nanoparticles

The main objective of the preparation of the Fe3 amp; 8722;xGaxO4 0.14 amp; 8804; x amp; 8804; 1.35 system was to further the knowledge of the magnetic response of Ga3 doped magnetite for application as MRI contrast agents. With this purpose, monodisperse nanoparticles between 7 and 10 nm with different amounts of gallium were prepared from an optimized protocol based on thermal decomposition of metallo organic precursors. Thorough characterization of the sample was conducted in order to understand the influence of gallium doping on the structural, morphological and magnetic properties of the Fe3 amp; 8722;xGaxO4 system. X ray diffraction and X ray absorption near edge structure measurements have proved the progressive incorporation of Ga in the spinel structure, with different occupations in both tetrahedral and octahedral sites. Magnetization measurements as a function of field temperature have shown a clear dependence of magnetic saturation on the gallium content, reaching an Ms value of 110 Am2 kg amp; 8722;1 at 5 K for x 0.14 significantly higher than bulk magnetite and considerably decreasing for amounts above x 0.57 of gallium. For this reason, nanoparticles with moderate Ga quantities were water transferred by coating them with the amphiphilic polymer PMAO to further analyse their biomedical potential. Cytotoxicity assays have demonstrated that Fe3 amp; 8722;xGaxO4 PMAO formulations with x amp; 8804; 0.57, which are the ones with better magnetic response, are not toxic for cells. Finally, the effect of gallium doping on relaxivities has been analysed by measuring longitudinal T1 amp; 8722;1 and transverse T1 amp; 8722;1 proton relaxation rates at 1.4 T revealing that nanoparticles with x 0.14 Ga3 content present remarkable T2 contrast and the nanoparticles with x 0.26 have great potential to act as dual T1 T2 contrast agent