Magnetic nanoparticles of CoFe2O4 have been synthesized under an applied magnetic field through a co-precipitation method followed by thermal treatments at different temperatures, producing nanoparticles of varying size. The magnetic behavior of these nanoparticles of varying size was investigated. As-grown nanoparticles demonstrate superparamagnetism above the blocking temperature, which is dependent on the particle size. The anomalous magnetic behavior is attributed to the preferred Co ions and vacancies arrangements when the CoFe2O4 nanoparticles were synthesized under applied magnetic field. Furthermore, this magnetic property is strongly dependent on the high temperature heat treatments, which produce Co ions and vacancies disorder. We performed the fabrication of condensed and mesoporous silica coated CoFe2O4 magnetic nanocomposites. The CoFe2O4 magnetic nanoparticles were encapsulated with well-defined silica layer. The mesopores in the shell were fabricated as a consequence of removal of organic group of the precursor through annealing. The NiO nanoparticles were loaded into the mesoporous silica. The mesoporous silica coated magnetic nanostructure loaded with NiO as a final product may have potential use in the field of biomedical applications. Growth mechanism of ZnO nanorod arrays on ZnO seed layer investigated by electric and Kelvin probe force microscopy. Both electric and Kelvin force probe microscopy was used to investigate the surface potentials on the ZnO seed layer, which shows a remarkable dependence on the annealing temperature. The optimum temperature for the growth of nanorod arrays normal to the surface was found to be at 600 °C, which is in the range of right surface potentials and energy measured between 500 °C and 700 °C. We demonstrated from both EFM and Kelvin force probe microscopy studies that surface potential controls the growth of ZnO nanorods. This study will provide important understanding of growth of other nanostructures. ZnO nanolayers were also grown by atomic layer deposition techniques. These nanolayers of ZnO demonstrate remarkable optical and electrical properties. These nanolayers were patterned by the Electron Beam Lithography (EBL) technique. A major goal of nanotechnology is to couple the self-assembly of molecular nanostructures with conventional lithography, using either or both bottom-up and top-down fabrication methods, that would enable us to register individual molecular nanostructures onto the functional devices. However, combining the nanofabrication technique with high resolution Electron Beam Lithography, we can achieve 3D bimolecular or/and DNA origami that will be able to identify nucleic acid sequences, antigen targets, and other molecules, as for a perfect nano-biosensor. We have explored some of the nanopatterning using EBL in order to fabricate biomolecule sensing on a single chip with sub nm pitch. The applications are not limited for the bioactivity, but for enhancing immunoreactions, cell culture dishes, and tissue engineering applications.
Layered lithiated transition metal oxides have been extensively developed and investigated as a cathode materials for lithium ion batteries due to the following advantages, such as high output voltage of 3.6 V, high energy density larger than 450Wh/dm3, low self-discharge rate less than 10%, no memory effect resulting in long cycle lives for more than 1000 times charging and discharging, free maintenance and no environmental pollution. The cathode materials in lithium ion battery are generally in the form of LiMO2 (M= Co, Ni, Mn, etc). Currently, lithium vanadium oxides also were studied. It is well known that the synthetic condition and methods are closely related to the electrochemical properties of lithium ion batteries. In this work, the wet chemical sol gel techniques have been used to synthesize LiNiO2 and LiV3O8. In this study, the LiNiO2 particles and LiV3O8 nanorods were successfully synthesized by sol-gel wet chemical methods. Annealing heat treatment influence the crystallinity of the final product, which may be consequently affected their electrochemical performance.
We report on the fabrication of condensed and mesoporous silica coated CoFe2O4 and FeCo alloy magnetic nanocomposites. The CoFe2O4 magnetic nanoparticles were encapsulated by well defined silica layer with a uniform thickness of 5 nm. The mesoporous silica shells lead to a larger magnetic coercivity than that of the pure CoFe2O4 magnetic nanoparticles due to decrease of interparticle interactions and magneto-elastic anisotropy. In addition, the FeCo nanoparticles were coated with condensed and mesoporous silica. As a consequence, the condensed silica protects the reactive FeCo alloy from oxidation up to 300 °C, maintaining the high magnetization of the nanoparticles. However, saturation magnetization of silica coated FeCo nanoparticles is dramatically decreased after annealing at 400 °C due to the oxidation of the FeCo core.
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