RESUMEN
Here, we report direct band gap transition for Gallium Phosphide (GaP) when alloyed with just 1-2 at% antimony (Sb) utilizing both density functional theory based computations and experiments. First principles density functional theory calculations of GaSbxP(1-x) alloys in a 216 atom supercell configuration indicate that an indirect to direct band gap transition occurs at x = 0.0092 or higher Sb incorporation into GaSbxP(1-x). Furthermore, these calculations indicate band edge straddling of the hydrogen evolution and oxygen evolution reactions for compositions ranging from x = 0.0092 Sb up to at least x = 0.065 Sb making it a candidate for use in a Schottky type photoelectrochemical water splitting device. GaSbxP(1-x) nanowires were synthesized by reactive transport utilizing a microwave plasma discharge with average compositions ranging from x = 0.06 to x = 0.12 Sb and direct band gaps between 2.21 eV and 1.33 eV. Photoelectrochemical experiments show that the material is photoactive with p-type conductivity. This study brings attention to a relatively uninvestigated, tunable band gap semiconductor system with tremendous potential in many fields.
RESUMEN
Functionalizing nanoparticle surfaces is essential for achieving homogeneous dispersions of monodisperse particles in polymer nanocomposites for successful utilization in engineering applications. Functionalization reduces the surface energy of the nanoparticles, thereby limiting the tendency to agglomerate. Moreover, reactive groups on the surface can also participate in the polymerization, creating covalent bonds between the inorganic and organic phases. In this paper, a fluidized bed inductively coupled plasma (FB-ICP) reactor is used to break apart the agglomerates and functionalize commercial TiO2 nanoparticle powders in a batch of several grams. The fluidized bed could be implemented into a continuous flow reactor, potentially making this a viable method to treat larger quantities of commercial powders. The particles are treated with acrylic acid (AA) and tetraethylorthosilicate (TEOS) plasma and the functionalized particles were collected separately from bulk powder. High resolution transmission electron microscopy (HRTEM) analysis showed that the particles were coated uniformly with polymer coatings with thicknesses around a few nanometers. Fourier-transformed infrared spectroscopy (FTIR) studies of the polymer-coated particles showed the presence of different functional groups (poly-acrylic acid/siloxane) similar to that present in the bulk films. The dispersion behavior of the TiO2 nanoparticles showed much improvement with reduced agglomerate size.
RESUMEN
Here, we report the synthesis of Si(x)Ge(1-x) nanowires with x values ranging from 0 to 0.5 using bulk nucleation and growth from larger Ga droplets. Room temperature Raman spectroscopy is shown to determine the composition of the as-synthesized Si(x)Ge(1-x) nanowires. Analysis of peak intensities observed for Ge (near 300 cm(-1)) and the Si-Ge alloy (near 400 cm(-1)) allowed accurate estimation of composition compared to that based on the absolute peak positions. The results showed that the fraction of Ge in the resulting Si(x)Ge(1-x) alloy nanowires is controlled by the vapor phase composition of Ge.