Thermal relaxation in combination with fiberglass confined interpenetrating networks: a key calcination process for as-desired free standing metal oxide nanofibrous membranes

Abstract

With unprecedented solar light active ZnWO₄/mixed-phased TiO₂ nanofibers as a model nanostructure, we showed that by simply allowing as-spun organic–inorganic hybrid samples to undergo thermal relaxation in combination with fiberglass confined calcination, as-desired and free-standing metal oxide nanofibrous membranes could be achieved for the first time. Under an electron microscope, the resulting metal oxide nanofibers were revealed to be freely interwoven without fixed crosslinks between the two contacting points and the fiber’s contour between any two slightly touching points appeared either curved or moderately digressed away from their original direction. The absence of crosslinking was attributed to the porous surface of the fiberglass fabric which offered a certain degree of spatial freedom to the membranes during calcination, leading to enhanced stress relaxation within the fiber during thermal annealing above the materials’ T_g. Such unique fibrous conformations promoted stress transfer along the fibers’ contours and prevented any possible stress concentration, enabling the calcined sample to withstand certain degrees of mechanical stress and so become less likely to fracture. We further demonstrated that the specific combination of metal precursors led to a photocatalytic platform for solar light induced deposition of a single layer of fully dispersed and highly catalytic noble metal nanoparticles.