Showing papers by "Somnath C. Roy published in 2010"

Toward Solar Fuels: Photocatalytic Conversion of Carbon Dioxide to Hydrocarbons

Abstract: The past several decades have seen a significant rise in atmospheric carbon dioxide levels resulting from the combustion of hydrocarbon fuels. A solar energy based technology to recycle carbon dioxide into readily transportable hydrocarbon fuel (i.e., a solar fuel) would help reduce atmospheric CO2 levels and partly fulfill energy demands within the present hydrocarbon based fuel infrastructure. We review the present status of carbon dioxide conversion techniques, with particular attention to a recently developed photocatalytic process to convert carbon dioxide and water vapor into hydrocarbon fuels using sunlight.

Synthesis and applications of electrochemically self-assembled titania nanotube arrays

Abstract: Highly ordered vertically oriented TiO2 nanotube arrays fabricated by electrochemical anodization offer a large surface area architecture with precisely controllable nanoscale features. These nanotubes have shown remarkable properties in a variety of applications including, for example, their use as hydrogen sensors, in the photoelectrochemical generation of hydrogen, dye-sensitized and solid-state heterojunction solar cells, photocatalytic reduction of carbon dioxide into hydrocarbons, and as a novel drug delivery platform. Herein we consider the development of the various nanotube array synthesis techniques, different applications of the TiO2 nanotube arrays, unresolved issues, and possible future research directions.

Syntheses, characterization, and X-ray crystal structures of two cis-dioxovanadium(V) complexes of pyrazole-derived, Schiff-base ligands

Abstract: Two mononuclear cis-dioxovanadium(V) complexes of pyrazole-derived, Schiff-base ligands have been synthesized and characterized. Single crystal X-ray analyses were performed with N ′-[(3-methyl-1H-pyrazole-5-yl)carbonyl]pyridine-2-carbohadrazonamido cis-dioxovanadium(V), {[VO2(PzOAP)] · H2O} (1), and 5-methyl-N-[(1E)-1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazonate cis-dioxovanadium(V), {[VO2(PzCAP)]} (2). Both complexes crystallize in monoclinic crystal systems with different space groups. Complex 1 crystallizes in the space group P21/c, 2 in space group C2/C. In each complex, the vanadium sits within a distorted square pyramidal geometry with an N2O3 chromophore. The τ parameters of the complexes (0.33 for 1, 0.22 for 2) support their square pyramidal geometry. The interesting finding in the work is that the alkoxide oxygen, imino nitrogen, and pyridine nitrogen take part in the coordination process leaving the pyrazole rings inactive in coordination.

Synthesis, characterization and spectrochemical studies on a few binuclear µ-oxo molybdenum(V) complexes of pyrimidine derived Schiff base ligands

Abstract: Ten new binuclear singly oxo-bridged molybdenum complexes (complexes 1–10) were prepared using five pyrimidine derived Schiff base ligands and two Mo(V) precursors (NH4)2MoOCl5 and (NH4)2MoOBr5. The ligands are prepared by the condensation of 4,6-dimethyl 2-hydrazino pyrimidine with salicylaldehyde (for HL1), o-hydroxy acetophenone (for HL2) and substituted salicylaldehydes (for HL3, HL4 and HL5) respectively. These ligands are already reported as good donors for Mo(VI) state. The µ-oxo Mo(V) complexes reported here bears a distorted octahedral geometry around each Mo atom with either N2O2Cl or N2O2Br chromophores. Fine variations in the spectroscopic behaviour of the complexes are observed in accordance with the varying electron donating properties of the ligands. All the complexes are unstable in solution and X-ray quality crystal of complex 1 could be isolated. All the complexes are characterized by IR and UV-Vis spectra.

Time-curvature and time-torsion of virtual bubbles as fluid mixing indicators

Abstract: Massive data sets describing vector fields from computational fluid dynamic simulations on high-performance computers can no longer be visualized directly by displaying the data values at each point in time and space, but require data reduction to analyze the essential properties. We describe early results of work in progress to visualize a dataset of 500GB of raw data, consisting out of multiple time steps from a CFD simulation describing the mixing of fluids within a Stirred tank. The objective is to assess the quality of the mixing of the fluids after some time. We compute pathlines with out-of-core memory management to handle the massive dataset on a single desktop machine and use these to trace the evolution of user-specified initial geometric structures. On top of these structures we compute quantities indicating the mixture, such as curvature and torsion of the pathlines as information complementary to the intrinsic curvature of the evolving time surfaces.