WO3/Buckypaper Membranes for Advanced Oxidation Processes

Photocatalytic materials, such as WO₃, TiO₂, and ZnO nanoparticles, are commonly linked onto porous polymer membranes for wastewater treatment, fouling mitigation and permeation enhancement. Buckypapers (BPs) are entanglements of carbon nanotubes, which have been recently proposed as innovative filtration systems thanks to their mechanical, electronic, and thermal properties. In this work, flexible membranes of single wall carbon nanotubes are prepared and characterized as efficient substrates to deposit by chemical vapor deposition thin layers of WO₃ and obtain, in such a way, WO₃/BP composite membranes for application in advanced oxidation processes. The photocatalytic efficiency of WO₃/BP composite membranes is tested against model pollutants in a small continuous flow reactor and compared with the performance of an equivalent homogeneous WO₃-based reactor.

Characterization of the cleaved edge cross section of the heterostructures with GaMnAs layer by the confocal micro-Raman spectroscopy

Confocal micro-Raman spectroscopy was used to measure cross-section linescans of the cleaved edge of heterostructures involving a GaMnAs layer. The investigations revealed a shift of the TO mode in the compressed GaMnAs layer to high frequencies relative to the TO GaAs mode in the substrate and to low frequencies in the tensile GaMnAs layers. These results are in agreement with the different manifestations of the anomalous Hall effect in the GaMnAs layers, with either compressive or tensile strains. It is shown that Raman spectroscopy is an appropriate method for the investigation of cross-sectional semiconductor heterostructures whose total thickness is comparable to the size of the analyzing laser spot.

Nitride surface passivation of GaAs nanowires: impact on surface state density

Surface nitridation by hydrazine-sulfide solution, which is known to produce surface passivation of GaAs crystals, was applied to GaAs nanowires (NWs). We studied the effect of nitridation on conductivity and microphotoluminescence (μ-PL) of individual GaAs NWs using conductive atomic force microscopy (CAFM) and confocal luminescent microscopy (CLM), respectively. Nitridation is found to produce an essential increase in the NW conductivity and the μ-PL intensity as well evidence of surface passivation. Estimations show that the nitride passivation reduces the surface state density by a factor of 6, which is of the same order as that found for GaAs/AlGaAs nanowires. The effects of the nitride passivation are also stable under atmospheric ambient conditions for six months.