This invention provides a multifunctional magnetic composition that can be used in applications such as slimebots and sensors. In one embodiment, said composition, comprises: a) 0.005-5 wt. % of a source of tetrafunctional borate ions; b) a buffer for maintaining pH at 6.5 to 9.5; c) 0.005-80 wt. % of magnetic particles; and d) a polymeric glue having hydroxyl groups; wherein said tetrafunctional borate ion, buffer and magnetic particles are crosslinked in said polymeric glue to form a non-Newtonian fluid composition.

The invention is directed to a method and a system for producing a ferrofluid comprising providing a stock solution with Fe(II) and Fe(III); mixing the stock solution with a base to form magnetic nanoparticles and a spent solution, said method further comprising a separation step of separating the nanoparticles from the spent solution by applying a magnet to immobilize the nanoparticles and remove at least part of the spent solution as supernatant from the immobilized nanoparticles. In another aspect, the invention is directed to the resulting ferrofluid.

Silica-coated magnetic nanoparticles with greater ability to remain dispersed, and methods of making and using silica-coated magnetic nanoparticles. The magnetic nanoparticles comprise a core and a coating, where the core comprises Fe.sub.3O.sub.4 or other magnetic material and the coating has a thickness of from about 1.5 nm to about 2 nm. The magnetic nanoparticles are useful for preparing nucleic acids for analysis, by separating nucleic acids from other components and by normalizing nucleic acid concentrations.

A composition having high dispersibility of a magnetic particle to have storage stability and a heat transport device using the composition. The composition contains a particle and an aqueous medium including water. The particle contains a magnetic particle and a dispersant including polyacrylic acid or a salt thereof.

Provided are cobalt ferrite particles having a micrometer-order average particle diameter and similar particle diameters. When a cobalt ferrite precursor is treated at a high temperature and a high pressure, an oxidation reaction is caused in the presence of a complexing agent, thereby obtaining intended cobalt ferrite magnetic particles.