Formation of Nanoparticle-Containing Multilayers in Nanochannels via Layer-by-Layer Assembly

Arrays of silicon nanochannels were used to investigate the layer-by-layer (LbL) assembly of nanoparticle-containing multilayers in confined geometries. LbL assembly of poly(vinylsulfonic acid)/titania (PVS/TiO2) and poly(diallyldimethylammonium chloride)/silica (PDAC/SiO2) resulted in conformal, uniform thickness multi layers throughout the high-aspect-ratio nanochannels. These multilayers were also calcinated to form nanoporous coatings within the nanochannels. Confined and unconfined multilayers were compared using scanning electron microscopy (SEM), showing significantly lower bilayer thicknesses when layers were assembled in confined geometries. Deposition was found to essentially stop at a nanochannel gap size of 55 nm for the PVS/TiO2 system and at 210 nm for the PDAC/SiO2 system, even though the channels were not plugged. These results provide further evidence of surface charge-induced depletion of unadsorbed species during LbL assembly, which occurs because of the closely spaced walls with like surface charge inherent in confined geometry LbL. This approach offers a simple but powerful new pathway to functionalize nanochannels with nanoporous coatings made from LbL-assembled nanoparticle-containing multilayers. It has applications in the production of functionalized nanofluidic devices for advanced separations utilizing size, charge, and potentially chemical or biological selectivity.