A novel scaly Sn3O4/TiO2 nanobelt heterostructured photocatalyst was fabricated via a facile hydrothermal route. The scaly Sn3O4 nanoflakes can be synthesized in situ and assembled on surface coarsened TiO2 nanobelts through a hydrothermal process. The morphology and distribution of Sn3O4 nanoflakes can be well-controlled by simply tuning the Sn/Ti molar ratio of the reactants. Compared with single phase nanostructures of Sn3O4 and TiO2, the scaly hybrid nanobelts exhibited markedly enhanced photoelectrochemical (PEC) response, which caused higher photocatalytic hydrogen evolution even without the assistance of Pt as a co-catalyst, and enhanced the degradation ability of organic pollutants under both UV and visible light irradiation. In addition to the increased exposure of active facets and broad light absorption, the outstanding performance is ascribed to the matching energy band structure between Sn3O4 and TiO2 at the two sides of the heterostructure, which efficiently reduces the recombination of photo-excited electron-hole pairs and prolongs the lifetime of charge carriers. Both photocatalytic assessment and PEC tests revealed that Sn3O4/TiO2 heterostructures with a molar ratio of Sn/Ti of 2/1 exhibited the highest photocatalytic activity. This study provides a facile and low-cost method for the large scale production of Sn3O4 based materials in various applications.
A SnO2 gas sensor was prepared by a two-step oxidation process whereby a Sn(II) precursor was partially oxidized by a hydrothermal process and the resulting Sn3O4 nanoplates were thermally oxidized to yield SnO2 nanoplates. The SnO2 sensor was selective and responsive toward ethanol at a temperature as low as 43 °C. This low sensing temperature stems from the rapid charge transport within SnO2 and from the presence of high-energy (001) facets available for oxygen chemisorption. SnO2/TiO2 nanobelt heterostructures were fabricated by a similar two-step process in which TiO2 nanobelts acted as support for the epitaxial growth of intermediate Sn3O4. At temperatures ranging from 43 to 276 °C, the response of these branched nanobelts is more than double the response of SnO2 for ethanol detection. Our observations demonstrate the potential of low-cost SnO2-based sensors with controlled morphology and reactive facets for detecting gases around room temperature.
Subtle changes in
stacking order of layered transition metal dichalcogenides
may have profound influence on the electronic and optical properties.
The intriguing electronic properties of
Td
-WTe
2
can be traced to the break of inversion symmetry resulting
from the ground-state stacking sequence. Strategies for perturbation
of the stacking order are actively pursued for intentional tuning
of material properties, where optical excitation is of specific interest
since it holds the potential for integration of ultrafast switches
in future device designs. Here we investigate the structural response
in
Td
-WTe
2
following ultrafast photoexcitation
by time-resolved electron diffraction. A 0.23 THz shear phonon, involving
layer displacement along the
b
axis, was excited
by a 515 nm laser pulse. Pump fluences in excess of a threshold of
∼1 mJ/cm
2
result in formation, with an ∼5
ps time constant, of a new stacking order by layer displacement along
the
b
axis in the direction toward the centrosymmetric
1
T
* phase. The shear displacement of the layers increases
with pump fluence until saturation at ∼8 pm. We demonstrate
that the excitation of the shear phonon and the stabilization of the
metastable phase are decoupled when using an optical pump as evidenced
by observation of a transition also in samples with a pinned shear
phonon. The results are compared to dynamic first-principles simulations
and the transition is interpreted in terms of a mechanism where transient
local disorder is prominent before settling at the atomic positions
of the metastable phase. This interpretation is corroborated by results
from diffuse scattering. The correlation between excitation of intralayer
vibrations and interlayer interaction demonstrates the importance
of including both short- and long-range interactions in an accurate
description of how optical fields can be employed to manipulate the
stacking order in 2-dimensional transition metal dichalcogenides.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.