Chemistry Commons^™

Observation Of Earlier Two-To-Three Dimensional Structural Transition In Gold Cluster Anions By Isoelectronic Substitution: MauN- (N=8–11; M=Ag,Cu), Lei-Ming Wang, Rhitankar Pal, Wei Huang, Xiao Cheng Zeng, Lai-Sheng Wang

Xiao Cheng Zeng Publications

The effects of isoelectronic substitution on the electronic and structural properties of gold clusters are investigated in the critical size range of the two-dimensional (2D)-three-dimensional (3D) structural transition (MAu_{n ⁻}, n=8–11; M=Ag,Cu) using photoelectron spectroscopy and density functional calculations. Photoelectron spectra of MAu_{n ⁻} are found to be similar to those of the bare gold clusters Au_n+1 ⁻ , indicating that substitution of a Au atom by a Ag or Cu atom does not significantly alter the geometric and electronic structures of the clusters. The only exception occurs at n …

Isomer Identification And Resolution In Small Gold Clusters, Wei Huang, Rhitankar Pal, Lei-Ming Wang, Xiao Cheng Zeng, Lai-Sheng Wang

Xiao Cheng Zeng Publications

A variety of experimental techniques are used to resolve energetically close isomers of Au_{7 ⁻} and Au_{8 ⁻} by combining photoelectron spectroscopy and ab initio calculations. Two structurally distinct isomers are confirmed to exist in the cluster beam for both clusters. Populations of the different isomers in the cluster beam are tuned using Ar-tagging, O₂-titration, and isoelectronic atom substitution by Cu and Ag. A new isomer structure is found for Au_{7 ⁻}, which consists of a triangular Au₆ unit with a dangling Au atom. Isomer-specific photoelectron spectra of Au_{8 ⁻} are obtained …

Two-Dimensional To Three-Dimensional Structural Transition Of Gold Cluster Au 10 During Soft Landing On Tio 2 Surface And Its Effect On Co Oxidation, Hui Li, Yong Pei, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

We investigate the possible structural transition of a planar Au₁₀ cluster during its soft landing on a TiO₂ (110) surface with or with no oxygen defects. The collision between the gold cluster and the oxide surface is simulated using the Car–Parrinello quantum molecular dynamics method. Both high-speed and low-speed conditions typically implemented in soft-landing experiments are simulated. It is found that under a high-speed condition, the gold cluster Au₁₀ can undergo a sequence of structural transitions after colliding with a defect-free TiO₂ (110) surface. When the TiO₂ (110) surface possesses oxygen vacancies, however, chemical bonds …

Icosahedral B12-Containing Core–Shell Structures Of B80, Hui Li, Nan Shao, Bo Shang, Lan-Feng Yuan, Jinlong Yang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Low-lying icosahedral (I_h) B₁₂-containing structures of B₈₀ are explored, and a number of core–shell isomers are found to have lower energy than the previous predicted B₈₀ fullerene. The structural transformation of boron clusters from tubular structure to core–shell structure may occur at a critical size less than B₈₀.

Graphene-Like Bilayer Hexagonal Silicon Polymorph, Jaeil Bai, Hideki Tanaka, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

We present molecular dynamics simulation evidence for a freezing transition from liquid silicon to quasi-twodimensional (quasi-2D) bilayer silicon in a slit nanopore. This new quasi-2D polymorph of silicon exhibits a bilayer hexagonal structure in which the covalent coordination number of every silicon atom is four. Quantum molecular dynamics simulations show that the stand-alone bilayer silicon (without the confinement) is still stable at 400 K. Electronic band-structure calculations suggest that the bilayer hexagonal silicon is a quasi-2D semimetal, similar to a graphene monolayer, but with an indirect zero band gap.

Associative Learning In Larval Dosophila Melanogaster: The Role Of Heredity In Learning Speed And Persistence Of Leaning Into Adulthood, Jasmin Hicklen, Domonique Jones, Michelle Vieyra

Journal of the South Carolina Academy of Science

No abstract provided.

The Effects Of The Sumter Wastewater Treatment Plant On The Survival And Reproduction Of Ceriodaphnia Dubia In Chronic Toxicity Tests, Erin Worley, Pearl R. Fernandes, S. Michele Harmon, Jeff Steinmetz

Journal of the South Carolina Academy of Science

No abstract provided.

Isomerization As A Key Path To Molecular Products In The Gas-Phase Decomposition Of Halons, Aimable Kalume, Lisa George, Scott Reid

Chemistry Faculty Research and Publications

The decomposition of halons remains controversial concerning the branching between radical and molecular products. The latter channel, where it has been found, is presumed to occur via a constrained symmetric multicenter transition state. Isomerization pathways in the gas-phase chemistry of halons have rarely been considered, despite the fact that the iso-halons, which feature a halogen−halogen bond, are widely recognized as important reactive intermediates in condensed phases. In this Letter, detailed calculations and modeling of the unimolecular decomposition of several important halons, including CF₂Cl₂, CF₂Br₂, and CHBr₃, reveal that isomerization is …

Immobilization Of Motile Bacterial Cells Via Dip-Pen Nanolithography, Dorjderem Nyamjav, Sergey Rozhok, Richard C. Holz

Chemistry Faculty Research and Publications

A strategy to bind bacterial cells to surfaces in a directed fashion via dip-pen nanolithography (DPN) is presented. Cellular attachment to pre-designed DPN generated microarrays was found to be dependent on the shape and size of the surface feature. While this observation is likely due in part to a dense, well formed mercaptohexadecanoic acid (MHA) monolayer generated via DPN, it may also simply be due to the physical shape of the surface structure. Motile Pseudomonas aeruginosa bacterial cells were observed to bind to DPN generated mercaptohexadecanoic acid/poly-L-lysine (MHA/PLL) line patterns, 'blocks' made up of eight lines with 100 nm spacings, …

The Stereochemistry Of Selected Supramolecular Complexes Of Cucurbiturils And The Effect Of Homogeneous Equilibria And Electron Transfer Of The Guest, Arumugam Thangavel

Doctoral Dissertations

"From a practical perspective, host-guest complexes are vehicles for understanding and using supramolecular interactions for purposeful function in sensors, molecular machines and switches, while from a fundamental perspective they may lead to novel supramolecular protection schemes in basic organic reactions. This dissertation examines the interactions of cucurbiturils as barrel-shaped hosts, exhibiting a hydrophobic cavity, with substituted benzoylpyrydinium, phenypyrylium, and diazaanthraquinonediium cations as guests. In water, N-methyl-4-(p-substituted benzoyl)pyridinium cations exist in equilibrium with their hydrated forms (gem-diols), whose concentrations depend on the para substituent. In the presence of cucurbit7uril (CB[7]), the benzoyl group shows a preference for the CB[7] cavity, and …

Conversion Of Racemic Ibuprofen To (S)-Ibuprofen, David Chavez-Flores

Open Access Theses & Dissertations

Ibuprofen is a common Non-Steroidal Anti-Inflammatory Drug (NSAID) sold as a racemic or equal mixture of (R) and (S) mirror-image enantiomers. Without patent protection, ibuprofen is an orphan drug even though one enantiomer, (S)-ibuprofen, provides relief three times faster than its racemic mixture with fewer side effects. The goal of this research was to develop a facile, environmentally benign (no waste of ibuprofen or catalysts), and inexpensive process to convert a commercially available racemic mixture of ibuprofen to the therapeutically active (S)-ibuprofen.

After many attempts, the most successful conversion of racemic ibuprofen to (S)-ibuprofen was the in situ racemization and …

Experimental Determination Of The Weiss Temperature Of Mn12-Ac And Mn12-Ac-Meoh, Christos Lampropoulos, Shiqi Li, Lin Bo, Bo Wen, M P. Sarachik, P Subedi, A D. Kent, Y Yeshurun, A J. Millis, S Mukherjee, G Christou

Chemistry Faculty Research and Scholarship

We report measurements of the susceptibility in the temperature range from 3.5 to 6.0 K of a series of Mn₁₂-ac and Mn₁₂-ac-MeOH samples in the shape of rectangular prisms of length l_c and square cross section of side l_a. The susceptibility obeys a Curie-Weiss law, χ=C/(T−θ), where θ varies systematically with sample aspect ratio. Using published demagnetization factors, we obtain θ for an infinitely long sample corresponding to intrinsic ordering temperatures T_c≈0.85 K and ≈0.74 K for Mn₁₂-ac and Mn₁₂-ac-MeOH, respectively. The difference in T_c for …

Reduced Electronic Spaces For Modeling Donor/Acceptor Interactions, Robert J. Cave, Stephen T. Edwards '06, John A, Kouzelos '07, Marshall D. Newton

All HMC Faculty Publications and Research

Diabatic states for donor (D) and acceptor (A) interactions in electron transfer (ET) processes are formulated and evaluated, along with coupling elements (H_DA) and effective D/A separation distances (r_DA), for reduced electronic spaces of variable size, using the generalized Mulliken Hush model (GMH), applicable to an arbitrary state space and nuclear configuration, and encompassing Robin−Day class III and as well as class II situations. Once the electronic state space is selected (a set of n ≥ 2 adiabatic states approximated by an orbital space based on an effective 1-electron (1-e) Hamiltonian), the charge-localized GMH …

Approaches Towards The Synthesis Of Bradyoxetin, Vanildo Martins Lima Braga

Electronic Theses and Dissertations

Quorum sensing bacteria produce and release chemical signal molecules (like N-acyl homoserine lactones, AHL) that increase in concentration as a function of cell density. The responses cover a large spectrum of process such as the virulence in Staphylococcus aureus, competence for DNA-uptake in Bacillus subtilis and Streptococcus pneumoniae, sporulation in Bacillus subtilis, conjugal plasmid transfer in Enterococcus faecalis, and bacteriocin production in lactic acid bacteria. The collapse of (AHL) signaling system in bacteria represents an attractive therapeutic approach towards the development of new antibiotics. Recently, a new extracellular modulator was isolated from a symbiotic bacterium (Bradyrhizobium japonicum) that nodulates soybean. …

Molecular Mechanics Studies Of Enzyme Evolutionary Mechanisms, Manoj Singh

All Dissertations

In the current dissertation, closely related studies to quantify the mechanism underlying enzyme evolution have been discussed. The HIV-1 protease and beta-lactamase enzymes were used as model systems for these studies. These are well known enzymes that are associated with drug resistance and are associated with the pathogenic diseases, and therefore, developing molecular level understanding of drug resistance through these enzymes has fundamental as well as practical importance.
In chapter 2, the relationship between errors in modeled protein structures and associated binding affinity predictions to small molecules is established. The results of this study are applicable in addressing a wide …

Synthesis And Characterization Of A [Ru(Bpy)2(Ncs)2] Derivative For Use As A Dye-Sensitizer In Nanocrystalline Solar Cells, Joel Thomas Kirner

Honors Program Theses

After extensive review of the field of dye-sensitized solar cells, the molecule [Ru(4,4’- dicarboxy-2,2’-bipyridine)(4,4’-di-(2-(2-pyridyl)ethenyl)-2,2’-bipyridine)(NCS)2] has been designed as an original contribution to the field. This dye sensitizer was chosen by derivatizing upon the structure of the standard sensitizer, cis-diisothiocyanatobis(4,4’-dicarboxylic acid-2,2’- bipyridine)ruthenium(II) (N3), by extending the conjugation of one bipyridine ligand. This structural derivatization should enhance light harvesting by red-shifting the dye’s absorbance and increasing the dye’s molar absorptivity, which should result in a dye-sensitized solar cell with higher efficiency. The Density Functional Theory (DFT) molecular orbital calculations of the new dye complex indicate that the HOMO is highly localized …

Toward A General Approach For Rna-Templated Hierarchical Assembly Of Split-Proteins, Jennifer L. Furman, Ahmed H. Badran, Oluyomi Ajulo, Jason R. Porter, Cliff I. Stains, David J. Segal, Indraneel Ghosh

Cliff Stains Publications

The ability to conditionally turn on a signal or induce a function in the presence of a user-defined RNA target has potential applications in medicine and synthetic biology. Although sequence-specific pumilio repeat proteins can target a limited set of ss- RNA sequences, there are no general methods for targeting ssRNA with designed proteins. As a first step toward RNA recognition, we utilized the RNA binding domain of argonaute, implicated in RNA interference, for specifically targeting generic 2-nucleotide, 3′ overhangs of any dsRNA. We tested the reassembly of a split-luciferase enzyme guided by argonaute-mediated recognition of newly generated nucleotide overhangs when …

The Efficacy Of Chemistry Outreach Programs On Middle School Students, Erica M. Dumeyer

Mahurin Honors College Capstone Experience/Thesis Projects

The current project was designed to determine if science outreach programs affect the attitude of the students toward science and increase the science content knowledge of the students participating in the program. Students from middle schools surrounding the Bowling Green area participated in the project. The data set includes a total of 850 students from 7th and 8th grade. Students were given a pre-test (taken several days before the presentation) and a post-test (taken several days after the presentation). The tests contain both subjective, affective as well as objective, content questions. The individual student pre-/post-tests were index numbered to protect …

Charge Transfer And Nanostructure Formation During Electroless Etching Of Silicon, Kurt W. Kolasinski

Chemistry Faculty Publications

No abstract provided.

Contact Angle Of A Nano-Drop On A Heterogeneous Surface, John Ritchie

Theses and Dissertations

CONTACT ANGLE OF A NANO-DROP ON A HETEROGENEOUS SURFACE By John Andre Ritchie, Master of Science A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University Virginia Commonwealth University, 2010 Major Director: Dr. Alenka Luzar, Professor of Chemistry

We examine the relation between contact angle of a nanodrop of water and the location of surface-water interaction energy at the perimeter and beneath the drop. Young’s equations gives the relationship between surface tension, at the three phase solid liquid vapor interface, and contact angle on a homogeneous surface. Cassie and Baxter …