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

We have recently fabricated Keggin-type polyoxometalate (H ₄SiW₁₂O₄₀) 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 H₄SiW₁₂O ₄₀ 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/H ₄SiW₁₂O₄₀ 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 H₄SiW ₁₂O₄₀ 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 H₄SiW₁₂O ₄₀ nanotubes were obtained with a Keggin structure.