Nanoclusters of nickel oxide using giant vesicles

Giant unilamellar vesicles (GUVs) of dioleoylphosphatidycholine (DOPC) and dipalmitoylphosphatidylethanolamine (DPPE) containing NiCl2 or NiSO4 have been used as templates to prepare nanoparticles of nickel oxide of 35–75 nm size. The GUVs have been studied by steady state fluorescence anisotropy, fluorescence life time measurements, optical microscopy and confocal laser scanning microscopy (CLSM). In general, the GUVs containing the nickel salts show a contraction in size (ranging from 14 to 19 μm) compared with pure GUVs (20–30 μm). Fluorescence anisotropy values show that GUVs with NiCl2 are better organized compared with those containing NiSO4. Transmission electron microscopy (TEM), and powder XRD studies corroborate these findings. The stacking of the lipids in the presence of Ni2+ leading to contraction in the GUVs has been modeled using Gaussian 03 package. Nickel sulfide formed from mixing these vesicles with Na2S containing vesicles, has been further calcined to obtain nanosized clusters of nickel oxide. Scanning electron micrographs of the nickel oxide formed from GUVs with NiCl2 show smaller sizes (35–45 nm) with wider size distributions compared with those from GUVs with NiSO4 (sizes 50–75 nm) that have more uniform sizes. Results suggest that by judicious choice of different anions in the metal salts a method to structure and tune the sizes and morphology of the nanoclusters using GUVs as templates is possible.