RESUMEN
Novel multifeatured hollandite K1.46Fe0.8Ti7.2O16 (KFTO) was synthesized by a simple hydrothermal method. Magnetic KFTO microrods were well controlled to long rectangular rods with pyramid-shaped tops. A KFTO growth mechanism was proposed on the basis of examining phase and morphology of the samples acquired at different reaction times. The KFTO morphology was confirmed by the calculated surface energies. The UV-vis diffuse reflectance spectra of KFTO microrods showed double absorption with band gaps of 2.01 and 2.16 eV, which was further confirmed by photoluminescence. First-principles studies revealed that the double absorption and magnetic properties originate from the d-d transitions of Fe3+ under the crystal field. The magnetic property could be applied in ferromagnetic semiconductor devices and the double absorption could be applied in visible-light harvesting. This work highlights the multifunctional KFTO microrods with low cost and environmental friendliness.
RESUMEN
The noble metals Au, Ag and Pt were loaded onto Na0.9Mg0.45Ti3.55O8 (NMTO) using a chemical bath deposition method devised in our recent work for the first time. The composite photocatalysts exhibit more effective photodegradation of methylene blue, due to the Schottky barrier built between NMTO and noble metal. Hot electrons generated during localized surface plasmon processes in metal nanoparticles transfer to the semiconductor, manifesting as a depression of surface potential directly detectable by scanning Kelvin probe microscopy. The key factor responsible for the improved ability of semiconductor-based photocatalysts is charge separation. The most effective weight concentrations of Au, Ag and Pt loaded onto NMTO were found to be 5.00%, 12.6% and 5.55% respectively. NMTO loaded with noble metals shows good photostability and recyclability for the degradation of methylene blue. A possible mechanism for the photodegradation of methylene blue over NMTO loaded with noble metals is proposed. This work highlights the potential application of NMTO-based photocatalysts, and provides an effective method to detect localized surface plasmons.
RESUMEN
A facile one-step hydrothermal process was developed for fabrication of three-dimensional hierarchical NiTe2@MoS2 heterostructures. A few layers of MoS2 uniformly grew on the NiTe2 nanorods, possessing a higher surface area. The strategy was extended to CoTe2@MoS2 heterostructures with a few layers of MoS2. The photocatalytic activities of the heterostructures were evaluated by the photodegradation of methylene blue. The composites show strong adsorption ability and much better photocatalytic efficiency in comparison with pure MoS2 microflowers and NiTe2 nanorods. Especially, the NiTe2@MoS2 heterostructure with 40 wt% of MoS2 presents the highest performance in photocatalytic degradation of dye molecules, which is attributed to the formation of hierarchical network between NiTe2 nanorods and MoS2 nanosheets. And the possible mechanism of the enhanced photocatalytic activities was discussed.
RESUMEN
CoTe and CoTe2 nanorods with average diameter of 100 nm were synthesized by a simple hydrothermal process, and different CoTe2 nanostructures were obtained by changing the NaOH concentration. CoTe nanorods exhibit weak ferromagnetism while CoTe2 nanorods present paramagnetic behavior. Different magnetic behaviors occur in the other CoTe2 nanostructures due to Na+ entrance into CoTe2 crystals. A first-principles study on Na-doped CoTe2 confirms the magnetic characteristics.