2 research outputs found
CaF<sub>2</sub>‑Based Near-Infrared Photocatalyst Using the Multifunctional CaTiO<sub>3</sub> Precursors as the Calcium Source
Multistage
formation of fluoride upconversion agents from the related-semiconductor
precursors provides a promising route for the fabrication of near-infrared
(NIR) photocatalysts with high photocatalytic activities. Herein,
the cotton templated CaTiO<sub>3</sub> “semiconduction”
precursors (C-CaTiO<sub>3</sub>) were used to synthesize the NIR photocatalyst
of Er<sup>3+</sup>/Tm<sup>3+</sup>/Yb<sup>3+</sup>–(CaTiO<sub>3</sub>/CaF<sub>2</sub>/TiO<sub>2</sub>) (C-ETYCCT), and the functions
of the Ca<sup>2+</sup> source for CaF<sub>2</sub> and the heterostructure
formations were displayed by C-CaTiO<sub>3</sub>. The generated CaF<sub>2</sub> acted as the host material for the lanthanide ions, and the
heterostructures were constructed among anatase, rutile, and the remaining
CaTiO<sub>3</sub>. The induced oxygen vacancies and Ti<sup>3+</sup> ions enabled the samples to utilize most of the upconversion luminescence
for photocatalysis. The NIR driven degradation rate of methyl orange
(MO) over C-ETYCCT reached 52.34%, which was 1.6 and 2.5 times higher
than those of Er<sup>3+</sup>/Tm<sup>3+</sup>/Yb<sup>3+</sup>–(CaTiO<sub>3</sub>/TiO<sub>2</sub>) (C-ETYCT) and Er<sup>3+</sup>/Tm<sup>3+</sup>/Yb<sup>3+</sup>–(CaTiO<sub>3</sub>/CaF<sub>2</sub>) (C-ETYCC),
respectively. The degradation rates of MO and salicylic acid over
C-ETYCCT with UV–vis–NIR light irradiation were also
much higher than those of other samples, which were mainly results
of the contributions of its high upconversion luminescence and the
efficient electron–hole pair separation
Morphology Evolution and Degradation of CsPbBr<sub>3</sub> Nanocrystals under Blue Light-Emitting Diode Illumination
Under
illumination of light-emitting diode (LED) or sunlight, the green
color of all-inorganic CsPbBr<sub>3</sub> perovskite nanocrystals
(CPB-NCs) often quickly changes to yellow, followed by large photoluminescence
(PL) loss. To figure out what is happening on CPB-NCs during the color
change process, the morphology, structure, and PL evolutions are systematically
investigated by varying the influence factors of illumination, moisture,
oxygen, and temperature. We find that the yellow color is mainly originated
from the large CPB crystals formed in the illumination process. With
maximized isolation of oxygen for the sandwiched film or the uncovered
film stored in nitrogen, the color change can be dramatically slowed
down whether there is water vapor or not. Under dark condition, the
PL emissions are not significantly influenced by the varied relative
humidity (RH) levels and temperatures up to 60 °C. Under the
precondition of oxygen or air, color change and PL loss become more
obvious when increasing the illumination power or RH level, and the
large-sized cubic CPB crystals are further evolved into the oval-shaped
crystals. We confirm that oxygen is the crucial factor to drive the
color change, which has the strong synergistic effect with the illumination
and moisture for the degradation of the CPB film. Meanwhile, the surface
decomposition and the increased charge trap states occurred in the
formed large CPB crystals play important roles for the PL loss