Naphtha catalytic cracking to olefins over zirconia-titania catalyst

The zirconia-titania based catalyst was synthesized by a co-participation method to study the catalytic cracking of heavy naphtha (dodecane) into high added-value chemical to olefins. The nanocrystal size catalysts were...

Зависимость поверхностной энергии от температуры и давления для макро- и нанокристалла

Based on the RP-model of a nanocrystal, an analytical method is developed for calculating the specific surface energy (), isochoric and isobaric derivatives of the  function with respect to temperature, and isothermal derivatives of the  function with respect to pressure and density. It is shown that the method is applicable for both macro-and nanocrystals with a given number of atoms and a certain surface shape. To implement this method, the parameters of the Mie–Lennard-Jones paired interatomic potential were determined in a self-consistent way based on the thermoelastic properties of the crystal. The method was tested on macrocrystals of 15 single-component substances: for 8-FCC crystals (Cu, Ag, Au, Al, Ni, Rh, Pd, Pt) and for 7-BCC crystals (Fe, V, Nb, Ta, Cr, Mo, W). The calculations were made at different temperatures and showed good agreement with the experimental data. Using the example of FCC-Rh, the change in surface properties with a decrease of the nanocrystal size along the isotherms of 10, 300, 2000 K is studied. It is shown that at high pressures and low temperatures, there is a region where the  function increases at an isomorphic-isothermal-isobaric decrease in the nanocrystal size. As the temperature increases, this area disappears.

Spectroscopic and Microscopic Correlation of SRO-HFCVD Films on Quartz and Silicon

This work is focused on making a correlation between results obtained by using spectroscopy and microscopy techniques from single and twofold-layer Silicon-Rich Oxide (SRO) films. SRO films single-layer and twofold-layer characterizations were compared considering the conditions as-grown and with thermal treatment at 1100 °C for 60 min in a nitrogen atmosphere. The thickness of the single-layer film is 324.7 nm while for the twofold-layer film it is 613.2 nm; after heat-treated, both thicknesses decreased until 28.8 nm. X-ray Photoelectron Spectroscopy shows changes in the excess-silicon in single-layer SRO films, with 10% in as-grown films and decreases to 5% for the heat-treated films. Fourier Transform Infrared Spectroscopy (FTIR) exhibits three characteristic vibrational modes of SiO2, as well as, the vibrating modes associated with the Si-H bonds, which disappear after the heat treatment. With UV–Vis spectroscopy results we obtained the absorbance and the absorption coefficient for the SRO films in order to calculate the optical bandgap energy (Egopt), which increased with heat-treatment. The energy peaks of the photoluminescence spectra were used to calculate the silicon nanocrystal size, obtaining thus an average size of 1.89 ± 0.32 nm for the as-grown layer, decreasing the size to 1.64 ± 0.01 nm with the thermal treatment. On the other hand, scanning electron microscopy and high-resolution transmission electron microscopy images confirm the thickness of the twofold-layer SRO films as 628 nm for the as-grown layer and 540 nm for the layer with heat-treatment, and the silicon nanocrystal size of 2.3 ± 0.6 nm for the films with thermal treatment.

Glycol ether additives control the size of PbS nanocrystals at reaction completion

In the colloidal synthesis of PbS quantum dots, added glycol ethers variably suppress the formation of metastable cluster intermediates. This achieves control of nanocrystal size in reactions run to completion.

The role of the capping agent and nanocrystal size in photoinduced hydrogen evolution using CdTe/CdS quantum dot sensitizers

Light-driven hydrogen evolution using CdTe/CdS quantum dots as sensitizers depends on the nature of the capping agent and nanocrystal size.