Search

Cu 2 O/exfoliated graphite composites (Cu 2 O/EG (1 wt%), Cu 2 O/EG (4 wt%), Cu 2 O/EG (7 wt%), Cu 2 O/EG (10 wt%), and Cu 2 O/EG (15 wt%)) were prepared by the precipitation method. The photocatalytic activity of the material was evaluated using the decolorization of methyl orange (MO) solution as model reaction. Results showed that Cu 2 O deposited on the worm-like flakes of EG in the form of nanocrystals. The EG provided a three-dimensional environment for photocatalytic reaction and endowed a high adsorption capacity for the sample. Under optimal conditions, the decolorization efficiencies of MO for 60 min reached 96.7%. Recycling of the catalyst showed Cu 2 O/EG composites (10 wt%) to possess high photocatalytic efficiency even when repeatedly used for five times. [ABSTRACT FROM AUTHOR]

Lanthanide-doped upconversion photoluminescent nanoparticles with unique anti-Stokes spectroscopic properties excel in many fields of application. Ytterbium-based self-sensitized fluorides with rich Yb3+ possess higher absorption efficiency of incident near infrared laser, and are more favorable for photoluminescence or optical heating applications. In this work, α-NaYbF 4 :Tm3+ crystalline nanoparticles are synthesized, which exhibit intense ultraviolet self-sensitized upconversion photoluminescence and highly efficient optical heating capability under 980 nm laser excitation. NaYbF 4 :Tm3+ nanocrystals emit multi-band luminescence with emission peaks located in the ultraviolet, blue and red spectral regions. The energy transfer mechanism and electronic transition pathways for the Upconversion luminescence are investigated based on the energy level scheme, and are further confirmed by luminescent dynamic analysis. Due to cross-relaxations between Tm3+ and energy back transfer from Tm3+ to Yb3+ processes, the NaYbF 4 : 1 mol% Tm3+ nanoparticles possess the highest luminescence intensity. The luminescent dynamic characteristics, such as decay time and rise time, vary with Tm3+ doping concentrations. Highly efficient optical heating effect is observed in the NaYbF 4 :Tm3+ nanoparticles with slope efficiency of photothermal conversion for 10 s laser irradiation is as high as 100.48 °C/W. [ABSTRACT FROM AUTHOR]

SO 4 2 − / ZrO 2 -carbon nanotubes (CNTs) were prepared through direct precipitation using ZrOCl 2 ·8H 2 O and H 2 SO 4 as raw materials and CNTs as support. The structure of composite samples was characterized through X-ray diffraction, scanning electron microscopy, energy-dispersive spectrometry, and Fourier-transform infrared spectroscopy. Results show that CNTs may provide large surface areas and ZrO 2 tetragonal was closely coated on CNTs surface. This catalyst was used to synthesize acetophenone ethylene glycol ketal. Factors influencing the synthesis of ketalization were also discussed and optimum reaction conditions were confirmed. Experimental results show that the yield of acetophenone ethylene glycol ketal was approximately 98.5% under optimum reaction conditions. [ABSTRACT FROM AUTHOR]

Bismuth trioxide (Bi 2 O 3) is known for its simple composition but rich polymorphism that allows a number of phase-dependent physicochemical properties and technical applications. We here report our controllable synthesis of highly discrete β-Bi 2 O 3 (tetragonal) nanoparticles (NPs) via the thermal oxidation of nearly-monodisperse Bi NPs. The size and shape (spherical and tear- or rod-like) of β-Bi 2 O 3 NPs are tunable by the size of parent Bi NPs whereas β and α (monoclinic) polymorphs can be selectively achieved by tailoring the oxidation temperature. The phase stability of β polymorph from room temperature to 450 °C enables us to perform an in situ high-temperature XRD study on the temperature dependence of its lattice parameters, which reveals a marked thermal expansion anisotropy in β-Bi 2 O 3 with a linear thermal expansion coefficient of +35.1 × 10−6 °C−1 in the c axis, fifteen times higher than that in the a axis. Meanwhile, the narrow band gap (2.27 eV for β vs. 2.77 eV for α) and strong visible-light absorption endow β-Bi 2 O 3 NPs with a good photocatalytic activity for the visible-light Rhodamine B dye degradation. We expect that our work could be a valuable reference for the studies on the size, shape and polymorph control, thermal property, and photocatalytic application of Bi 2 O 3. [ABSTRACT FROM AUTHOR]

S 2 O 8 2− /TiO 2 –exfoliated graphite (EG) solid acid catalysts were prepared by a sol–gel method using Ti(OCH 2 CH 2 CH 2 CH 3 ) 4 and (NH 4 ) 2 S 2 O 8 as raw materials, as well as EG as support. The structure of the composite samples was characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectrometry, and Fourier-transform infrared spectroscopy. The results demonstrate TiO 2 anatase to be closely coated on the surface of exfoliated graphite. The effects of calcination temperature on the acidity, texture, and catalytic performance of S 2 O 8 2− /TiO 2 –EG solid acid catalysts were further studied. Factors influencing the synthesis of acetalation were discussed, and the optimum reaction conditions were confirmed. Experimental results show that the yield of benzaldehyde glycol acetal was about 98.8% under the following conditions: molar ratio of benzaldehyde to glycol of 1:1.5, catalyst quantity of 0.5% of feedstock, and reaction time of 50 min. [ABSTRACT FROM AUTHOR]