Layer-by-layer self-assembled tubular films containing polyoxometalate on electrospun nanofibers

Self-assembled polyoxometalate (H3PMo12O40) ultrathin tubular films were fabricated on electrospun cellulose acetate (CA) nanofibers via the electrostatic layer-by-layer (LBL) adsorption of oppositely charged polyethylenimine (PEI) and H3PMo12O40. The films coated fibers were characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and wide-angle X-ray diffraction (WAXD). The morphology of LBL films coated CA nanofibers was studied by regulating the pH value and ionic strength of PEI solutions, the number of PEI/H3PMo12O40 bilayers, and the concentration of H3PMo12O40. The results indicated that the growth of LBL films fabricated at a PEI pH of 2.5 and a H3PMo12O40 pH of 2.5 (PEI2.5/H3PMo12O402.5) was much quicker than that of films of PEI and H3PMo12O40 adsorbed at pH 9 and 2.5 (PEI9/H3PMo12O402.5), respectively. Moreover, the concentration of H3PMo12O40, the number of coating bilayers, and the ionic strength of PEI solutions also showed strong influence to the growth of LBL films on nanofibers. Additionally, the high porous LBL films coated fibers were found after the deposition of PEI/H3PMo12O40 films from a high ionic strength of PEI solutions.