Free-standing layer-by-layer assembled films of magnetite nanoparticles

A new technique for preparation of free-standing ultrathin films is present ed. These films were made by layer-by-layer (LBL) deposition process, which is utilized for coatings on solid substrates and colloids. A film composed of alternating layers of magnetite nanoparticles and poly(diallyldimethyla mmonium bromide) was assembled on cellulose acetate, which was subsequently dissolved in acetone. From the suspended state, the LBL film can be transf erred onto any solid or porous support. The strength of the film was observ ed to significantly increase when every other layer of magnetite was replac ed with a layer of alumosilicate sheets serving as a molecular framework fo r the assembly.