Disclosed herein are iron oxide nanoparticles prepared through high-temperature thermal decomposition of an Fe.sup.3+ precursor and an M.sup.+ or M.sup.2+ (M=Li, Na, K, Mg, and Ca) precursor in an oxygen atmosphere. The iron oxide nanoparticles are nanoparticles, in which an alkali metal or alkali earth metal is doped into an Fe vacancy site of -Fe.sub.2O.sub.3, and generate explosive heat even in a biocompatible low AC magnetic field. Through both in vitro and in vivo tests, it was proven that cancer cells could be killed by performing low-frequency hyperthermia using the iron oxide nanoparticles set forth above.

A method of making Co.sub.3O.sub.4 nanorods by thermal decomposition of a cobalt salt is described. A method of using Co.sub.3O.sub.4 nanorods as an electrocatalyst component to a porous carbon electrode is also described. The carbon electrode may be made of carbonized filter paper. Together, this carbon-supported Co.sub.3O.sub.4 electrode may be used for water electrolysis.

A method of making Co.sub.3O.sub.4 nanorods by thermal decomposition of a cobalt salt is described. A method of using Co.sub.3O.sub.4 nanorods as an electrocatalyst component to a porous carbon electrode is also described. The carbon electrode may be made of carbonized filter paper. Together, this carbon-supported Co.sub.3O.sub.4 electrode may be used for water electrolysis.

An e-type iron-based oxide magnetic particle powder has narrow particle size distribution and has a low content of fine particles which do not contribute to magnetic recording characteristics. As a result, a narrow coercive force distribution is achieved and the powder is suitable for increasing recording density of a magnetic recording medium. The powder containing substituting metal elements can be obtained by: adding an alkali to an aqueous solution containing trivalent iron ions and ions of the metals for partially substituting Fe sites to neutralize the aqueous solution to a pH of 1.5 to 2.5; then adding a hydroxycarboxylic acid; further adding the alkali to neutralize the aqueous solution to a pH of 8.0 to 9.0; washing with water a precipitation of an iron oxyhydroxide containing the substituting metal elements produced; and coating the iron oxyhydroxide containing the substituting metal elements with a silicon oxide and heating the resultant.

The method of synthesizing magnetite/maghemite core/shell nanoparticles is a modified co-precipitation method for producing iron oxide (Fe.sub.3O.sub.4/-Fe.sub.2O.sub.3) nanoparticles that allows for production of the Fe.sub.3O.sub.4/-Fe.sub.2O.sub.3 core/shell nanoparticles with a desired shell thickness ranging between about 1 nm to 5 nm for biomedical and data storage applications. Aqueous solutions of ferric and ferrous salts are mixed at room temperature and pH of the mixture is raised to 10. The mixture is then heated at 80 C. for different lengths of time at atmospheric pressure to adjust particle size, and the precipitate is dried at 120 C. in vacuum. Oxidation in an oxygen atmosphere for different lengths of time is used to adjust the thickness of the -Fe.sub.2O.sub.3 shell.

A composition of matter includes a liquid and nanoparticles suspended in the liquid. The nanoparticles each include silica, alumina, and an organosilicon functional group having a molecular weight of at least 200. A method includes functionalizing a surface of nanoparticles with an organosilicon functional group and dispersing the nanoparticles in a liquid to form a suspension. The functional group has a molecular weight of at least 200. The nanoparticles each include silica and alumina at a surface thereof.

Some embodiments provide a system for external manipulation of magnetic nanoparticles in vasculature using a remotely placed magnetic field-generating stator. In one aspect, the systems and methods relate to the control of magnetic nanoparticles in a fluid medium using permanent magnet-based or electromagnetic field-generating stator sources. Such a system can be useful for increasing the diffusion of therapeutic agents in a fluid medium, such as a human circulatory system, which can result in substantial clearance of fluid obstructions, such as vascular occlusions, in a circulatory system resulting in increased blood flow.

Apparatuses for manipulating a color displayed by an article of wear comprising iron oxide colloidal nanocrystals arranged within chains are described. The apparatus includes (a) a magnetic field source, wherein a strength of a magnetic field generated by the magnetic field source is tunable to control the color displayed by the article of wear, and (b) an energy source, wherein energy generated by the energy source is applied to at least some of the chains of nanocrystals to soften materials within the article of wear immediately surrounding the chains of nanocrystals to which the energy is applied.

A structural body that includes a film that has a phase-separated nanostructure where a separate columnar shape phase is dispersed in a matrix phase that are phase-separated in a state of thermal equilibrium. The matrix phase is formed from any one of a p-type semiconductor material and an n-type semiconductor material, and the separate columnar shape phase is formed from the other semiconductor material. The film is formed on a substrate such that the separate columnar shaped phase and the matrix phase have three-dimensional junction planes.

Articles of wear comprises iron oxide colloidal nanocrystals arranged within chains are described. The chains of nanocrystals display a color that is determined by a strength of a magnetic field applied to the chains of nanocrystals, wherein the color is maintained when the magnetic field is removed.