42 research outputs found
Influence of CH(OH) isomers on water disinfection by photocatalysis: a computational study
Solar disinfection by photocatalysis is one of the promising methods used for
drinking water disinfection. It leads to the destruction of bacteria like
( ). In this paper, we compare our theoretical
results with experimental ones done previously by A.G. Rinc\'on and his
colleagues concerning the order of decay of CH(OH) isomers in
the presence of titanium dioxide TiO, and show the influence of optical
properties of those molecules on inactivation. According to the
adsorption energy parameter, we find that catechol has the highest adsorption
degree on titanium dioxide, followed by resorcinol, and finally hydroquinone.
Three dihydroxybenzene isomers absorb photons belonging to ultraviolet (UV)
range. The lowest absorption energies of resorcinol, catechol and hydroquinone
are respectively 3.42, 4.44 and 4.49 eV.Comment: 7 pages, 3 figures, 1 tabl
A vibrational circular dichroism implementation within a Slater-type-orbital based density functional framework and its application to hexa- and hepta-helicenes
We describe the implementation of the rotational strengths for vibrational circular dichroism (VCD) in the Slater-type orbital based Amsterdam Density Functional (ADF) package. We show that our implementation, which makes use of analytical derivative techniques and London atomic orbitals, yields origin independent rotational strengths. The basis set dependence in the particular case of Slater-type basis functions is also discussed. It turns out that the triple zeta STO basis sets with one set of polarization functions (TZP) are adequate for VCD calculations. The origin- dependence of the atomic axial tensors is checked by a distributed origin gauge implementation. The distributed and common origin gauge implementations yield virtually identical atomic axial tensors with the Slater-type basis sets employed here, proving that our implementation yields origin independent rotational strengths. We verify the implementation for a set of benchmark molecules, for which the dependence of the VCD spectra on the particular choice of the exchange–correlation functional is studied. The pure functionals BP86 and OLYP show a particularly good performance. Then, we apply this approach to study the VCD spectra of hexa- and hepta- helicenes. In particular we focus on relationships between the sign of the rotational strengths of the two helicenes
Magnetic and Nanostructural Properties of Cobalt–Zinc Ferrite for Environmental Sensors
In this study, we compare nanoparticles (NPs) of Co0.5Zn0.5Fe2O4 spinel ferrite
produced by a novel simple synthetic technique with those made by standard
co-precipitation, sol-gel, and hydrothermal methods. The novel process is based
on the addition of a very small amount of ethanol (only 2 vol% in water with a
low ethanol:metals molar ratio of 0.5:1, not a co-solvent) during co-precipitation
to synthesize a nanopowder, which formed single-phase magnetic spinel ferrite
when heated at 700 !C. This technique produced cobalt–zinc ferrite NPs smaller
than those formed by the other methods, with an average crystallite size of 17 nm
calculated from X-Ray Diffraction and NPs sizes around 30 nm observed by
scanning electron microscopy. A surface area of 32 m2/g, and a total pore volume
of about 0.56 cm3/g, were determined by the BET isotherm. The best catalytic
capabilities for converting ethanol vapor to CO, CO2, and H2O, as well as
magnetic properties, were obtained for Co0.5Zn0.5Fe2O4 synthesized by the
ethanol-assisted co-precipitation. The ethanol conversion rate rapidly increased
above 175 !C, and the total conversion of ethanol was achieved at a relatively low
temperature of 230 !C. This sample also had the largest magnetization of 58.2 A
m2 kg"1 at 3 T, and a very small, near superparamagnetic, coercivity