Thin film nanofabrication via layer-by-layer adsorption of tubule halloysite, spherical silica, proteins and polycations

The microcylinders of halloysite of 50 nm diameter, 500 nm length and with 20 nm diameter hollow inner core were used in the assembly by alternate adsorption with poly(ethyleneimine) (PEI), which resulted in the formation of ordered multilayers containing from 2 up to 20 layers of the tubules glued together by polycation interlayers. The tubules in each monolayer are loosely packed; they form a network in the remaining 50% empty space. The total thickness of the (halloysite/PEI)14 film was found to be 720 nm, i.e. 54 nm for the layer pair. The tubule/sphere superlattice films were also assembled through alternation of halloysite, 45-nm diameter silica spheres and linear polycations. An assembly of alcohol dehydrogenase (ADH) and halloysite loaded with nicotinamide adenine dinucleotide in alternation with PEI was accomplished. This assembly is designed to provide a direct supply of the ADH-cofactor to the enzyme immobilized in polyion films.