Nanoclusters of doped zirconium oxide and core-shell iron: Synthesis, characterization and physical properties.

摘要

This dissertation titled "Nanoclusters of Doped ZnO and Core-shell Iron", is focused on the study of synthesis and characterization of two types of nanoclusters; (1) doped ZnO and (2) iron-iron oxide core-shell nanoclusters (NC). We synthesis highly stable, monodispersive crystalline NC of sizes ranging from 2 to 100 nm, using a third generation NC source that combines magnetron sputtering with gas-aggregation technique. PL spectra of ZnO NC films with clusters ∼7 nm size, exhibit significant blueshift of ∼125 meV in the UV region at RT. When small percentages of transition metal or N atoms are added to Zn atoms in the oxygen atmosphere, doped ferromagnetic (FM) ZnO NC are formed. Magnetic moment of Ni (V)-doped sample is much larger than Ti (Co)-doped ZnO NC sample at 300 K. Ti (Co) exhibits isovalent state of +4 (+2) through out the cluster film. V (Ni) in doped ZnO NC shows mixed oxidation states, which results in double exchange interactions that enhances the magnetic moments of V (Ni) than Ti (Co)-doped ZnO cluster films. V-doped ZnO exhibits giant moment of 9.5 mu&Bgr; per dopant atom, which is remarkably high.; Examination of core-shell Fe NCs synthesized by this process allows the detailed study of Fe NCs. NC films are porous and its specific surface areas (SSA) measured by BET are size dependent. SSA increases from 187 to 807 m 2/g initially with decrease in the size of NC from 15.7 to 9.4 rim and then decreases to 135 m2/g with further decreases of size to 5.5 nm. Chemical reactivity of nanoporous films increases with decrease in NC size. Iron-iron oxide NC has enhanced possibilities for distribution, significant chemical reactivity rate and environmentally friendly reaction paths. Magnetic NC have been found promising in several biomedical applications for tagging, imaging, sensing and separation. Stable core-shell iron-iron oxide NC we synthesized have high specific magnetic moments > 150 emu/g.