Polyoxometalate nanotubes from layer-by-layer coating and thermal removal of electrospun nanofibres

We have recently fabricated Keggin-type polyoxometalate (H4SiW12O40) nanotubes by calcining layer-by-layer (LBL) structured ultrathin hybrid film coated electrospun fibrous mats. The hybrid film coated electrospun fibrous mats were obtained from the alternate deposition of positively charged poly(allylamine hydrochloride) (PAH) and negatively charged H4SiW12O40 on the surface of negatively charged cellulose acetate (CA) nanofibres using the electrostatic LBL self-assembly technique. The fibrous mats were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared (FT-IR) spectroscopy, and wide-angle x-ray diffraction (WAXD). It was found that the morphology of hybrid PAH/H4SiW12O40 film coated fibrous mats was strongly influenced by the number of deposition bilayers and the pH of dipping solutions. The fibrous mats were contracted and H4SiW12O40 nanotubes with a wall thickness of about 50 nm can be fabricated after calcination at high temperature. Additionally, the FT-IR and WAXD results indicated that the pure H4SiW12O40 nanotubes were obtained with a Keggin structure.