University of Belgrade, Institute for Multidisciplinary Research
Abstract
Hierarchical nanostructures with multiporous tin oxide nanofibers (SnO2-
MPNFs) and zinc oxide nanorods (ZnO-NRs) have been synthesized by combining
electrospinning technique and hydrothermal method. A solution containing
uniformly distributed tin (Sn) and silicon (Si) species of precursors, as well as a
sacrificial polymer (PVP) was electrospun using a single-nozzle spinneret to
fabricate nanofibers. In virtue of the Kirkendall effect driven by calcination at
550 °C, the SiO2-cored SnO2 nanofibers (SnO2-SiO2-NFs) deliberated from PVP
were formed and used as backbones for further hydrothermal growth of ZnO-NRs.
By varying the hydrothermal reaction time (0.5–2 h) at the constant concentration of
SnO2-SiO2-NFs, zinc (Zn) precursor, directing agent (hexamethylenetetramine,
HMT) and aqueous ammonia, the density, length and thickness of ZnO-NRs were
controlled. Nanofibers and ZnO-NRs/SnO2-MPNFs heterostructures are confirmed
by X-ray diffraction (XRD), field-emission scanning electron microcopy (FE-SEM),
energy dispersive spectrometer (EDS), transmission electron microscopy (TEM) and
elemental mapping analysis.
The hydrothermal treatment conducted at 90 °C in aqueous ammonia allowed:
a) selective etching of SiO2 from the SnO2-SiO2-NFs core and SiO2 trapped between
SnO2 particles, and b) effective growth of ZnO-NRs. The process resulted in
ZnO-NRs/SnO2-MPNFs heterostructures with ZnO-NRs of 1–5 μm in length
attached to SnO2-MPNFs, the shell of which was composed of ultra-fine SnO2
crystallites (~5 nm in size) and where the four porous channels create the core
instead of SiO2. Photocatalytic performance of the heterostructures was investigated
toward different organic azo-dyes (methylene blue, methyl orange) and obvious
enhancement was demonstrated in degradation of the organic pollutant, compared to
primary SnO2-based nanofibers
