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The photocatalytic characteristics of nanometer-sized TiO 2 powder prepared by a homogeneous-precipitation process (HPP) were compared with those of a commercial powder to determine which powder was better able to remove metal ions, such as lead and copper, from aqueous equimolar metalethylenediaminetetraacetic acid (EDTA) solution. In aqueous lead-EDTA solution, the TiO 2 powder fabricated by HPP had 3.5 times higher initial adsorption of lead ion and a 1.5 times faster rate for the complete elimination of lead ions than did the commercial powder. In an aqueous copper-EDTA solution, the TiO 2 powder fabricated by HPP also showed higher initial adsorption and a faster elimination rate for copper ions than did the commercial powder. Similarly, the photocatalytic properties were enhanced as the specific surface area increased, and the TiO 2 powder fabricated by HPP, which consisted of coagulated primary particles 20 nm in size, with chestnut-burr shapes, had a larger specific surface area (ϳ180 m 2 /g) than that of the commercial powder (ϳ55 m 2 /g).

ZnO nanopowder was prepared by a novel “solution-combustion method (SCM)” and it was used as a semiconductor photocatalyst to evaluate its photoreduction properties. Aqueous Pb-EDTA and Cu-EDTA solutions of heavy metal ions (Pb and Cu) were used for the photocatalysis reaction under UV illumination. The result was then compared with other semiconductor photocatalyst powder such as TiO2 powder (P25; Degussa) and TiO2 powder prepared by homogeneous precipitation process at low temperature (HPPLT). In the removal of Pb++ ions, the ZnO nanopowder showed 2.6 fold higher removal rate than P25 TiO2 powder and 1.8 fold higher than HPPLT TiO2. Also the ZnO nanopowder showed the highest removal rate of the Cu++ ions from the solution among the different photocatalyst powders compared. The superior photoreduction ability of the ZnO nanopowder appears to be due to its excellent UV absorption characteristics. This was confirmed by the photoluminescence (PL) measurement.

The properties of molecule-optical elements such as lenses or prisms based on the interaction of molecules with optical fields depend in a crucial way on the molecular quantum state and its alignment created by the optical field. Herein, we consider the effects of state-dependent alignment in estimating the optical dipole force acting on the molecules and, to this end, introduce an effective polarizability which takes proper account of molecular alignment and is directly related to the alignment-dependent optical dipole force. We illustrate the significance of including molecular alignment in the optical dipole force by a trajectory study that compares previously used approximations with the present approach. The trajectory simulations were carried out for an ensemble of linear molecules subject to either propagating or standing-wave optical fields for a range of temperatures and laser intensities. The results demonstrate that the alignment-dependent effective polarizability can serve to provide correct estimates of the optical dipole force, on which a state-selection method applicable to nonpolar molecules could be based. We note that an analogous analysis of the forces acting on polar molecules subject to an inhomogeneous static electric field reveals a similarly strong dependence on molecular orientation

ZnO nanopowders were prepared by Solution Combustion Method (SCM). The ZnO nanopowders synthesized using Zn(OH)2 and glycine as an oxidant and a fuel (with fuel/ oxidant ratio, F/O=0.8), showed excellent crystalline and photocatalytic characteristics. To confirm photocatalytic activities of the prepared ZnO powder, total organic carbon (TOC) was tried to remove from aqueous phenol solution. Surprisingly, SCM ZnO nanopowder shows 1.6 fold higher destruction rates of the organic pollutant than P-25 TiO2 nanopowder which is known as a kind of standard photocatalyst.