Showing papers by "Praveen K. Thallapally published in 2011"
TL;DR: Cucurbit[7]uril (CB[7], in its amorphous solid state, shows one of the highest CO(2) sorption capacities among known organic porous materials at 298 K and 0.1 and 1 bar.
94 citations
TL;DR: This review will focus on the use of various nanoparticulate and polymeric systems that have been developed for imaging and drug delivery to the lymph system, how these new devices improve upon current technologies, and where further improvement is needed.
71 citations
TL;DR: A well-known organic host, tris-o-phenylenedioxycyclotriphosphazene, exists in two polymorphic guest-free forms: the thermodynamic nonporous high density phase and the kinetic nanoporous low-density phase as mentioned in this paper.
40 citations
TL;DR: In this paper, a two-dimensional layered coordination polymer [Co(2,4'-bpdc)(H2O)]n containing one-dimensional double-stranded left-handed helical channels from achiral building block 2, 4'-biphenyldicarboxylic acid (2, 4'H2bpdc) was reported.
Abstract: Two dimensional layered like coordination polymer [Co(2,4'-bpdc)(H2O)]n containing one-dimensional double-stranded left-handed helical channels from achiral building block 2,4'-biphenyldicarboxylic acid (2,4'-H2bpdc) was reported. The resultant crystals were not racemic as evidenced by the observation of strong signals in vibrational circular dichroism (VCD) and circular dichroism (CD) spectra
33 citations
TL;DR: A metal-organic framework obtained from a flexible organic linker shows a breathing phenomenon upon adsorption of saturated hydrocarbons.
28 citations
TL;DR: The results indicated that the Cu-BTC-containing stationary phase had limited thermal stability (220 °C) and strong general retention for analytes and selectivity was not observed for aromatic compounds (including nitroaromatics) or nitroalkanes.
Abstract: The metal-organic framework Cu-BTC was evaluated for its ability to selectively interact with Lewis-base analytes, including explosives, by examining retention on GC columns packed with Chromosorb W HP that contained 3.0% SE-30 along with various loadings of Cu-BTC. SEM images of the support material showed the characteristic Cu-BTC crystals embedded in the SE-30 coating on the diatomaceous support. Results indicated that the Cu-BTC-containing stationary phase had limited thermal stability (220°C) and strong general retention for analytes. Kovats index calculations showed selective retention (amounting to about 300 Kovats units) relative to n-alkanes for many small Lewis-base analytes on a column that contained 0.75% Cu-BTC compared to an SE-30 control. Short columns that contained lower loadings of Cu-BTC (0.10%) were necessary to elute explosives and related analytes; however, selectivity was not observed for aromatic compounds (including nitroaromatics) or nitroalkanes. Observed retention characteristics are discussed.
26 citations
TL;DR: A new plywood-like network from ligand 2H(2) exhibiting an unprecedented six-way chiral helical packing motif is identified, which extends the list of invariant rod packings.
20 citations
01 Sep 2011
TL;DR: In this paper, two aerogel formulations were investigated, one based on silica aerogels and the second based on chalcogen-based aeroglobels, for the removal and immobilization of iodine and krypton, specifically 129I and 85Kr.
Abstract: The materials development summarized here is in support of the Waste Forms campaign, Volatile Radionuclide task. Specifically, materials are being developed for the removal and immobilization of iodine and krypton, specifically 129I and 85Kr. During FY 2011, aerogel materials were investigated for removal and immobilization of 129I. Two aerogel formulations were investigated, one based on silica aerogels and the second on chalcogen-based aerogels (i.e., chalcogels). A silica aerogel was tested at ORNL for total I2 sorption capacity. It was determined to have 48 mass% capacity while having little physisorbed I2 (I2 not taken up in the aerogel pores). For 85Kr, metal organic framework (MOF) structures were investigated and a new MOF with about 8 mass% capacity for Xe and Kr. The selectivity can be changed from Xe > Kr to Xe < Kr simply by lowering the temperature below 0 C. A patent disclosure has been filed. Lastly, silicon carbide (SiC) was loaded with Kr. The diffusion of Kr in SiC was found to be less than detectable at 500 C.
16 citations
TL;DR: Structural results indicate the organic linkers in Ni\DOBDC are the primary binding sites for both n-hexane and cyclohexane molecules, and at all temperatures and loadings examined in present work, n- Hexane clearly showed stronger binding with Ni\ DOBDC than cyclo hexane, which was found to be the result of the ability of n- hexane to reconfigure its structure to a greater degree than cyclosorbates and adsorbents.
Abstract: Enhancing the efficiency of the Rankine cycle, which is utilized for multiple renewable energy sources, requires the use of a working fluid with a high latent heat of vaporization. To further enhance its latent heat, a working fluid can be placed in a metal organic heat carrier (MOHC) with a high heat of adsorption. One such material is Ni\DOBDC, in which linear alkanes have a higher heat of adsorption than cyclic alkanes. We carried out molecular dynamics simulations to investigate the structural, diffusive, and adsorption properties of n-hexane and cyclohexane in Ni\DOBDC. The strong binding for both n-hexane and cyclohexane with Ni\DOBDC is attributed to the increase of the heat of adsorption observed in experiments. Our structural results indicate the organic linkers in Ni\DOBDC are the primary binding sites for both n-hexane and cyclohexane molecules. However, at all temperatures and loadings examined in present work, n-hexane clearly showed stronger binding with Ni\DOBDC than cyclohexane. This was found to be the result of the ability of n-hexane to reconfigure its structure to a greater degree than cyclohexane to gain more contacts between adsorbates and adsorbents. The geometry and flexibility of guest molecules were also related to their diffusivity in Ni\DOBDC, with higher diffusion for flexible molecules. Because of the large pore sizes in Ni\DOBDC, energetic effects were the dominant force for alkane adsorption and selectivity.
12 citations
TL;DR: In this article, the adsorption and diffusivity of a metal organic framework with the organic linker tetrakis[4-(carboxyphenyl)oxamethyl]methane, the metal salt, Zn2+, and an organic pillar, 4,4′-bipyridin was studied using molecular dynamics simulations.
10 citations
Patent•
10 Oct 2011
TL;DR: In this article, a thermal energy storage material is described, including a host-guest complex wherein the combined rotational, vibrational, translational, and binding energies of a guest molecule are dependent upon the temperature of the surrounding environment.
Abstract: A thermal energy storage material is described, including a host-guest complex wherein the combined rotational, vibrational, translational, and binding energies of a guest molecule are dependent upon the temperature of the surrounding environment. The host-guest complex may include nanoparticles having a topography, such as nanotubes, nanobowls, nanospheres, and nanocages. The host-guest complex may include a metal organic framework. The guest of the host-guest complex may be water, carbon dioxide, carbon monoxide, nitrogen, oxygen, acetone, methanol, ethanol, or another inert compound.