Chemistry Commons^™

Ultrafast Dynamics Of Triplet Excitons In Alq3-Bridge-Pt(Ii)Porphyrin Electroluminescent Materials, Victor A. Montes, Cesar Perez-Bolivar, Leandro A. Estrada, Joseph Shinar, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

Excited-state dynamics are crucial for maximizing the performance of organic light-emitting diodes (OLEDs). Because electron-hole recombination yields singlet and triplet excited states in a 3:1 ratio, it is important to harvest the energy of triplets in light-emitting processes. Self-assembled multichromophore electroluminescent materials consisting of a trisquinolinolate aluminum(III) (Alq(₃)) donor, fluorene-based conjugated oligomers; as a bridge, and Pt(II)tetraphenylporphyrin as an acceptor and phosphorescent emitter are described. In these materials, the energy of singlet as well as triplet states is harvested and emitted as red phosphorescence from the porphyrin acceptor. Attention was devoted to the triplet exciton dynamics, which was …

Cholesteric Liquid Crystal Displays As Optical Sensors Of Barbiturate Binding, R. Carlisle Chambers, Elissa J. Bell, Tauni M. Records, Anna Cherian, Karen Ragan, Bonnie Swartout

Faculty Publications - Department of Biological & Molecular Science

The influence on the optical properties of cholesteric liquid crystal displays (LCDs) was examined for neutral molecule binding by mesogen/receptors in the mesomorphic phase. The motivation was to prepare neutral molecule sensors that use a colour change to signal analyte binding. A receptor that binds barbiturate analytes was modified with two or one cholesteryl groups to yield compounds 2 and 3, respectively. LCDs were prepared by incorporating one of the receptor/mesogen compounds into a cholesteric LC blend along with a potential Hbonding guest. The optical properties of the LCDs were then determined by measuring the absorbance of the displays. For …

Instrumentation And Metrology For Single Rna Counting In Biological Complexes Or Nanoparticles By A Single-Molecule Dual-View System, Hui Zhang, Dan Shu, Faqing Huang, Peixuan Guo

Faculty Publications

Limited by the spatial resolution of optical microscopy, direct detection or counting of single components in biological complexes or nanoparticles is challenging, especially for RNA, which is conformationally versatile and structurally flexible. We report here the assembly of a customized single-molecule dual-viewing total internal reflection fluorescence imaging system for direct counting of RNA building blocks. The RNA molecules were labeled with a single fluorophore by in vitro transcription in the presence of a fluorescent AMP. Precise calculation of identical or mixed pRNA building blocks of one, two, three, or six copies within the bacteriophage phi29 DNA packaging motor or other …

Modification Of Carboplatin By Jurkat Cells, Anthony J. Di Pasqua, Jerry Goodisman, Deborah J. Kerwood, James C. Dabrowiak, Bonnie B. Toms

Chemistry - All Scholarship

Using [¹H,¹⁵N] heteronuclear single quantum coherance (HSQC) NMR and ¹⁵N-labeled carboplatin, 1, we show that Jurkat cells affect the rate of disappearance of the HSQC NMR peak in culture medium for this Pt²⁺ anticancer drug. The decay or disappearance rate constant for 1 in culture medium containing cells is k1=kc[CO32-]+km+kuN, where k_c is the rate constant for reaction of 1 with carbonate in the medium, k_m is the rate constant for reaction of 1 with all other components of the medium, and k_u is the rate constant for reaction of …

Antimony Vibrations In Skutterudites Probed By ¹²¹Sb Nuclear Inelastic Scattering, Hans Christian Wille, Raphäel P. Hermann, Ilya Sergueev, Olaf Leupold, Peter Van Der Linden, Brian C. Sales, Fernande Grandjean, Gary J. Long, Rudolf Rüffer, Yuri V. Shvyd'ko

Chemistry Faculty Research & Creative Works

The specific lattice dynamic properties of antimony in the unfilled CoSb₃ and filled EuFe₄Sb₁₂ skutterudites have been determined by nuclear inelastic scattering at the ¹²¹Sb nuclear resonance energy of 37.1298(2) keV with a 4.5 meV high-resolution backscattering sapphire monochromator. The Sb partial vibrational density of states (DOS) shows a maximum centered at 17 and 16 meV in CoSb₃ and EuFe₄Sb₁₂, respectively. The difference between the Sb DOSs of CoSb₃ and EuFe₄Sb₁₂ reveals that upon filling there is a transfer of 10% of the vibrational states toward …

Intrinsic Conformational Preferences Of And An Anomeric-Like Effect In 1-Substituted Silacyclohexanes, Abby Jones Weldon, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

A series of ab initio computations have been performed to estimate the CCSD(T) complete basis set limit of the axial/equatorial energy difference for the chair conformation of 1-fluoro, 1-chloro, 1-methyl, 1-hydroxy, and 1-methoxysilacyclohexanes. The equatorial conformation is more stable than the axial by 0.21 kcal mol-1 for 1-methylsilacyclohexane, while the axial position is more stable for 1-fluoro, 1-chloro, and 1-methoxysilacyclohexane (by 0.09, 0.40, and 0.15 kcal mol-1, respectively). The axial and equatorial orientations of 1-hydroxysilacyclohexane are nearly electronically isoenergetic (equatorial favored by 0.03 kcal mol^-1). Zero-point vibrational energy corrections have very little effect on the relative energies (less …

Benzimidazolium Surfactants For Modification Of Clays For Use With Styrenic Polymers, Marius C. Costache, Matthew Heidecker, Evangelos Manias, Rakesh K. Gupta, Charles A. Wilkie

Chemistry Faculty Research and Publications

Nanocomposites of polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS) and high impact polystyrene (HIPS) were prepared with two new homologous benzimidazolium surfactants used as organic modifications for the clays. The morphology of the polymer/clay hybrids was evaluated by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM), showing good overall dispersion of the clay. The thermal stability of the polymer/clay nanocomposites was enhanced, as evaluated by thermogravimetric analysis. From cone calorimetric measurements, the peak heat release rate of the nanocomposites was decreased by about the same amount as seen for other organically-modified, commercially available clays.

Generation Of Molecular Complexity From Cyclooctatetraene: Synthesis Of A Protected 2-(3′-Carboxy-2′-Benzoylcyclopentyl)Glycine, Subhabrata Chaudhury, Sergey V. Lindeman, William A. Donaldson

Chemistry Faculty Research and Publications

Synthesis of a protected 2-(3′-carboxycyclopentyl)glycine rac-11, possessing four contiguous chiral carbons, was accomplished in six steps (20% yield) from the hydrocarbon cyclooctatetraene.

Revealing Nano-Confinement In Degradation And Relaxation Studies Of Two Structurally Different Polystyrene-Clay Systems, Kai Chen, Charles A. Wilkie, Sergey Vyazovkin

Chemistry Faculty Research and Publications

Degradation and relaxation studies have been performed on two polystyrene (PS)−montmorillonite clay nanocomposites, one of which has an intercalated PS−clay structure and the other an exfoliated PS−clay brush structure. Compared to virgin PS, both nanostructured materials have demonstrated the following similarities: (a) a high yield of α-methylstyrene in the degradation products as measured by infrared spectroscopy; (b) larger values of the activation energy of the thermal degradation as determined by isoconversional kinetic analysis of thermogravimetric data; and (c) larger values of the activation energy for the glass transition as found from the frequency dependence of the glass transition temperature measured …

Ferrocene And Ferrocenium Modified Clays And Their Styrene And Eva Composites, Charles Manzi-Nshuti, Charles A. Wilkie

Chemistry Faculty Research and Publications

In this work, ferrocene- and ferrocenium-containing salts were employed to modify montmorillonite. X-ray measurements show an increase in the interlayer spacing upon clay modification, which means that the larger and more organophilic cations were inserted into the gallery space of montmorillonite. Attempts to prepare nanocomposites of polystyrene and ethylene vinyl acetate copolymers lead to immiscible systems; the morphology of these systems was elucidated with TEM, XRD and cone calorimetry. The thermal stability of the composites is greater than that of the virgin polymer.

Gnep Quarterly Input – Unlv July 1 Through September 30, 2007, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects, activities and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the Global Nuclear Energy Partnership (GNEP) through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

The Tropical Forest And Fire Emissions Experiment: Trace Gases Emitted By Smoldering Logs And Dung From Deforestation And Pasture Fires In Brazil, Ted J. Christian, Robert J. Yokelson, João A. Carvalho, David W.T. Griffith, Ernesto C. Alvarado, José Carlos Santos, Turibio Gomes Soares Neto, Carlos A.Gurgel Veras, Wei Min Hao

Chemistry and Biochemistry Faculty Publications

Earlier work showed that Amazonian biomass burning produces both lofted and initially unlofted emissions in large amounts. A mobile, Fourier transform infrared spectrometer (FTIR) measured the unlofted emissions of 17 trace gases from residual smoldering combustion (RSC) of logs as part of the Tropical Forest and Fire Emissions Experiment (TROFFEE) during the 2004 Amazonian dry season. The RSC emissions were highly variable and the few earlier RSC measurements lay near the high end of combustion efficiency observed in this study. Fuel consumption by RSC was ∼5% of total for a planned deforestation fire. Much regional RSC probably occurs in the …

The Tropical Forest And Fire Emissions Experiment: Emission, Chemistry, And Transport Of Biogenic Volatile Organic Compounds In The Lower Atmosphere Over Amazonia, Thomas Karl, Alex Guenther, Robert J. Yokelson, Jim Greenberg, Mark Potosnak, Donald R. Blake, Paulo Artaxo

Chemistry and Biochemistry Faculty Publications

Airborne and ground-based mixing ratio and flux measurements using eddy covariance (EC) and for the first time the mixed layer gradient (MLG) and mixed layer variance (MLV) techniques are used to assess the impact of isoprene and monoterpene emissions on atmospheric chemistry in the Amazon basin. Average noon isoprene (7.8 +/- 2.3 mg/m(2)/h) and monoterpene fluxes (1.2 +/- 0.5 mg/m(2)/h)compared well between ground and airborne measurements and are higher than fluxes estimated in this region during other seasons. The biogenic emission model, Model of Emissions of Gases and Aerosols from Nature (MEGAN), estimates fluxes that are within the model and …

Reduction Of Esters To Ethers Utilizing The Powerful Lewis Acid Bf2otf·Oet2, Brian Pagenkopf, Nicholas A. Morra

Chemistry Publications

No abstract provided.

Reactivity Of [Re2(Co)8(Mecn)2] With Thiazoles: Hydrido Bridged Dirhenium Compounds Bearing Thiazoles In Different Coordination Modes, Shariff E. Kabir, Faruque Ahmed, Anamika Das, Mohammad R. Hassan, Daniel T. Haworth, Sergey V. Lindeman, G. M. Golzar Hossain, Tasneem Siddiquee, Dennis W. Bennett

Chemistry Faculty Research and Publications

Reactions of the labile compound [Re₂(CO)₈(MeCN)₂] with thiazole and 4-methylthiazole in refluxing benzene afforded the new compounds [Re₂(CO)₇{μ-2,3-η²-C₃H(R)NS}{η¹-NC₃H₂(4-R)S}(μ-H)] (1, R = H; 2, R = CH₃), [Re₂(CO)₆{μ-2,3-η²-C₃H(R)NS}{η¹-NC₃H₂(4-R)S}₂(μ-H)] (3, R = H; 4, R = CH₃) and fac-[Re(CO)₃(Cl){η¹-NC₃H₂(4-R)S}₂] (5, R = H; …

Oxygen Measurement Via Phosphorescence: Reaction Of Sodium Dithionite With Dissolved Oxygen, Zhimin Tao, Jerry Goodisman, Abdul-Kader Souid

Chemistry - All Scholarship

A homemade instrument for the measurement of oxygen concentration in aqueous solutions measures the decay rate of the phosphorescence of a Pd-porphyrin complex (phosphor) dissolved in the solution, which is flashed every 0.1 s with 630 nm light. The concentration of O ₂ is a linear function of the decay rate. The instrument is used to study the reaction of dithionite (S ₂O ₄ ^2-) with O ₂ at 25°C and 37°C. It is found that the ratio of dithionite to oxygen consumed in the reaction is 1.2 ± 0.2 at 25°C and 1.7 ± 0.1 at 37°C, …

Inclusion Of Electrochemically Active Guests By Novel Oxacalixarene Hosts, Daniel Sobransingh, Mahender B. Dewal, Jacob Hiller, Mark D. Smith, Linda S. Shimizu

Faculty Publications

We demonstrate for the first time the utility of oxacalixarenes as hosts and investigate the forces that influence the thermodynamics of binding.

Novel Perturbation Approach For The Structure Factor Of The Attractive Hard-Core Yukawa Fluid, Andrij Trokhymchuk, Roman Melnyk, Filip Moucka, Ivo Nezbeda

Faculty Publications

A novel perturbation approach for the structure factor S(k) of the Lennard-Jones-type Yukawa fluid with z=1.8 is presented. An approach is based on a new reference system, that is, the short-range Yukawa model with z0 > z=1.8. By choosing for the reference system the value z0=6, it is shown that (i) the proposed approach for S(k) performs much better than the traditional hard-sphere reference perturbation method does; (ii) the use of an approximate mean spherical (MSA) description of the reference structure factor provides the results for S(k) that are more accurate as those obtained from the direct MSA computations; and (iii) …

Ovarian Cancer G Protein–Coupled Receptor 1, A New Metastasis Suppressor Gene In Prostate Cancer, Lisam Shanjukumar Singh, Michael Berk, Rhonda Oates, Zhenwen Zhao, Haiyan Tan, Ying Jiang, Aimin Zhou, Kashif Kirmani, Rosemary Steinmetz, Daniel Lindner, Yan Xu

Chemistry Faculty Publications

Background

Metastasis is a process by which tumors spread from primary organs to other sites in the body and is the major cause of death for cancer patients. The ovarian cancer G protein–coupled receptor 1 (OGR1) gene has been shown to be expressed at lower levels in metastatic compared with primary prostate cancer tissues.

Methods

We used an orthotopic mouse metastasis model, in which we injected PC3 metastatic human prostate cancer cells stably transfected with empty vector (vector-PC3) or OGR1-expressing vector (OGR1-PC3) into the prostate lobes of athymic or NOD/SCID mice (n = 3–8 mice per group). Migration of PC3 …

Quantum Confinement Of Crystalline Silicon Nanotubes With Nonuniform Wall Thickness: Implication To Modulation Doping, Binghai Yan, Xiao Cheng Zeng, Jian Wu, Bing-Lin Gu, Wenghui Duan

Xiao Cheng Zeng Publications

First-principles calculations of crystalline silicon nanotubes (SiNTs) show that nonuniformity in wall thickness can cause sizable variation in the band gap as well as notable shift in the optical absorption spectrum. A unique quantum confinement behavior is observed: the electronic wave functions of the valence band maximum and conduction band minimum are due mainly to atoms located in the thicker side of the tube wall. This is advantageous to spatially separate the doping impurities from the conducting channel in doped SiNTs. Practically, the performance of the SiNT-based transistors may be substantially improved by selective p/n doping in the thinner side …

Isolation Of The Saddle And Crown Conformers Of Cyclotriveratrylene (Ctv) Oxime, Marlon R. Lutz Jr., David C. French, Peter Rehage, Daniel P. Becker

Chemistry: Faculty Publications and Other Works

The oxime of cyclotriveratrylene (CTV) has been prepared and the individual crown and saddle conformers were isolated and characterized. The equilibrium constant was measured in CDCl3 and in DMSO-d6 and was shown to favor the crown conformer by an order of magnitude in DMSO-d6, relative to an approximately equal mixture at equilibrium in CDCl3. The time course for interconversion of the saddle to the crown was measured by 1H NMR and the t1/2 of the saddle was determined to be 2.45 h in CDCl3 at 25 °C, and 3.71 h in DMSO-d6.

Snell's Law Of Refraction Observed In Thermal Frontal Polymerization, John A. Pojman, Veronika Viner, Burcu Binici, Shanna Lavergne, Melanie Winsper, Dmitry Golovaty, Laura Gross

Faculty Publications

We demonstrate that Snell’s law of refraction can be applied to thermal fronts propagating through a boundary between regions that support distinct frontal velocities. We use the free-radical frontal polymerization of a triacrylate with clay filler that allows for two domains containing two different concentrations of a peroxide initiator to be molded together. Because the polymerization reaction rates depend on the initiator concentration, the propagation speed is different in each domain. We study fronts propagating in two parallel strips in which the incident angle is 90°. Our data fit Snell’s law v_r/v_i = sin θ_r/sin …

Organic Geochemical Investigation Of A Highly Contaminated Urban Waterway: The Gowanus Canal, Brooklyn, New York, Usa, Michael A. Kruge, Kevin K. Olsen, Eric A. Stern

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

The Gowanus Canal is an industrial waterway constructed in the mid-19^th century by widening and deepening a natural tidal channel. It is ca. 3 km in length and empties into Gowanus Bay, an arm of New York Harbor. Its banks, reinforced by bulkheads and piers, became the site of intensive industrial activity, including oil refining, coal gasification, soap making and tanning. Even though much of the industrial activity along the canal has ceased, its sediments remain highly enriched in organic and inorganic contaminants, with combined sewer outfalls continuing to transport pollutants into the canal. The canal area remains densely …

Aromatase And Cox In Breast Cancer: Enzyme Inhibitors And Beyond, Robert W. Brueggemeier, Bin Su, Yasuro Sugimoto, Edgar S. Diaz-Cruz, Danyetta D. Davis

Chemistry Faculty Publications

Aromatase expression and enzyme activity in breast cancer patients is greater in or near the tumor tissue compared with the normal breast tissue. Complex regulation of aromatase expression in human tissues involves alternative promoter sites that provide tissue-specific control. Previous studies in our laboratories suggested a strong association between aromatase (CYP19) gene expression and the expression of cyclooxygenase (COX) genes. Additionally, nonsteroidal anti-inflammatory drugs (NSAIDs) and COX selective inhibitors can suppress CYP19 gene expression and decrease aromatase activity. Our current hypothesis is that pharmacological regulation of aromatase and/or cyclooxygenases can act locally to decrease the biosynthesis of estrogen and may …

A Novel Empirical Free Energy Function That Explains And Predicts Protein–Protein Binding Affinities, Joseph Audie, Suzanne Scarlata

Chemistry & Physics Faculty Publications

A free energy function can be defined as a mathematical expression that relates macroscopic free energy changes to microscopic or molecular properties. Free energy functions can be used to explain and predict the affinity of a ligand for a protein and to score and discriminate between native and non-native binding modes. However, there is a natural tension between developing a function fast enough to solve the scoring problem but rigorous enough to explain and predict binding affinities. Here, we present a novel, physics-based free energy function that is computationally inexpensive, yet explanatory and predictive. The function results from a derivation …

Magnetic Properties Of Variable-Sized Fe3o4 Nanoparticles Synthesized From Non-Aqueous Homogeneous Solutions Of Polyols, D. Caruntu, Gabriel Caruntu, Charles J. O'Connor

Chemistry Faculty Publications

The magnetic behaviour of well-dispersed monodisperse Fe3O4 nanoparticles with sizes varying between 6.6 and 17.8 nm prepared in a non-aqueous medium was investigated. The smaller nanocrystals exhibit superparamagnetism with the blocking temperatures increasing with the particle size, whereas the biggest particles are ferromagnetic at room temperature. The saturation magnetization values are slightly smaller than that of the bulk material, suggesting the existence of a disordered spin configuration on their surface. The thickness of the magnetically inert shell was estimated from the size variation of the magnetization at 1.9 Å. The dipole–dipole interactions between the particles were tuned by changing the …

2,3,8,12,13-Penta­Meth­Oxy-5h-Dibenzo­[C,N]Acridin-7(6h)-One Toluene Solvate, Marlon R. Lutz Jr, Matthias Zeller, Daniel P. Becker Ph.D.

Chemistry: Faculty Publications and Other Works

The title compound, C26H25NO6·C7H8, formed by an unexpected tandem reaction of Beckmann rearrangement, electrophilic aromatic addition and subsequent demethyl­ation, was crystallized as its toluene solvate. The crystal under investigation was found to be nonmerohedrally twinned by a rotation around the reciprocal axis [100]; the twin ratio refined to 0.688 (2):0.312 (2). The mol­ecule exhibits an unusual helical arrangement of three six-membered rings that are all connected at one central C atom. The helix effectively performs one full turn around this atom, and the thread pitch, as defined by the distance of the terminal C atoms of the helix, is 4.98 …

Thermal Stability Of Nanostructurally Stabilized Zirconium Oxide, Fereydoon Namavar, Gonghua Wang, Chin Li Cheung, Renat F. Sabirianov, Xiao Cheng Zeng, Wai Ning Mei, Jaeil Bai, Joseph R. Brewer, Hani Haider, Kevin L. Garvin

Xiao Cheng Zeng Publications

Nanostructurally stabilized zirconium oxide (NSZ) hard transparent films were produced without chemical stabilizers by the ion beam assisted deposition technique (IBAD). A transmission electron microscopy study of the samples produced below 150 °C revealed that these films are composed of zirconium oxide (ZrO₂) nanocrystallites of diameters 7.5 ± 2.3 nm. X-ray and selected-area electron diffraction studies suggested that the as-deposited films are consistent with cubic phase ZrO₂. Rutherford backscattering spectroscopy (RBS) indicated the formation of stoichiometric ZrO₂. The phase identity of these optically transparent NSZ films was in agreement with cubic ZrO₂, …

Ab Initio Study Of Hydrogen Adsorption On Benzenoid Linkers In Metal–Organic Framework Materials, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

We have computed the energies of adsorption of molecular hydrogen on a number of molecular linkers in metal–organic framework solid materials using density functional theory (DFT) and ab initio molecular orbital methods. We find that the hybrid B3LYP (Becke three-parameter Lee–Yang–Parr) DFT method gives a qualitatively incorrect prediction of the hydrogen binding with benzenoid molecular linkers. Both local-density approximation (LDA) and generalized gradient approximation (GGA) DFT methods are inaccurate in predicting the values of hydrogen binding energies, but can give a qualitatively correct prediction of the hydrogen binding. When compared to the more accurate binding- energy results based on the …

First Total Synthesis And Structural Reassignment Of (-)-Aplysiallene., Jian Wang, Brian L Pagenkopf

Chemistry Publications

The first total synthesis of (-)-aplysiallene has been completed in 16 steps and features a key sequential Mukaiyama aerobic oxidative cyclization to prepare the fused bis-THF core. The original stereochemical assignment has been revised as shown.