Physical Sciences and Mathematics Commons^™

Optical-Optical Double Resonance, Laser Induced Fluorescence, And Revision Of The Signs Of The Spin-Spin Constants Of The Boron Carbide (Bc) Free Radical, Fumie X. Sunahori, Ramya Nagarajan, Dennis J. Clouthier

Chemistry Faculty Publications

The cold boroncarbide free radical (BC X  ⁴Σ⁻) has been produced in a pulsed discharge free jet expansion using a precursor mixture of trimethylborane in high pressure argon. High resolution laser induced fluorescencespectra have been obtained for the B  ⁴Σ⁻–X  ⁴Σ⁻ and E  ⁴Π–X  ⁴Σ⁻ band systems of both ¹¹BC and ¹⁰BC. An optical-optical double resonance (OODR) scheme was implemented to study the finer details of both band systems. This involved pumping a single rotational level of the B state with one laser and then …

Crystal Structure Of (E)-13-(Pyrimidin-5-Yl)Parthenolide, Shobanbabu Bommagani, Narsimha Reddy Penthala, Sean Parkin, Peter A. Crooks

Chemistry Faculty Publications

The title compound, C₁₉H₂₂N₂O₃, {systematic name (1aR,4E,7aS,8E,10aS,10bR)-1a,5-dimethyl-8-[(pyrimidin-5-yl)­methylid­ene]-2,3,6,7,7a,8,10a,10b-octa­hydro­oxireno[2′,3′:9,10]cyclo­deca­[1,2-b]furan-9(1aH)-one} was obtained from the reaction of parthenolide [systematic name (1aR,7aS,10aS,10bR,E)-1a,5-dimethyl-8-methyl­ene-2,3,6,7,7a,8,10a,10b-octa­hydro­oxireno[2′,3′:9,10]cyclodeca­[1,2-b]furan-9(1aH)-one] with 5-bromo­pyrimidine under Heck reaction conditions, and was identified as an E isomer. The mol­ecule possesses ten-, five- (lactone) and three-membered (epoxide) rings with a pyrimidine group as a substituent. The ten-membered ring displays an approximate chair–chair conformation, while the lactone ring shows a flattened …

Solution-Printed Organic Semiconductor Blends Exhibiting Transport Properties On Par With Single Crystals, Muhammad R. Niazi, Ruipeng Li, Er Qiang Li, Ahmad R. Kirmani, Maged Abdelsamie, Qingxiao Wang, Wenyang Pan, Marcia M. Payne, John E. Anthony, Detlef-M. Smilgies, Sigurdur T. Thoroddsen, Emmanuel P. Giannelis, Aram Amassian

Chemistry Faculty Publications

Solution-printed organic semiconductors have emerged in recent years as promising contenders for roll-to-roll manufacturing of electronic and optoelectronic circuits. The stringent performance requirements for organic thin-film transistors (OTFTs) in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require performance currently achieved by organic single-crystal devices, but these suffer from scale-up challenges. Here we present a new method based on blade coating of a blend of conjugated small molecules and amorphous insulating polymers to produce OTFTs with consistently excellent performance characteristics (carrier mobility as high as 6.7 cm²V⁻¹s⁻¹, low threshold …

The Nicotine Metabolite, Cotinine, Alters The Assembly And Trafficking Of A Subset Of Nicotinic Acetylcholine Receptors, Ashley M. Fox, Faruk H. Moonschi, Christopher I. Richards

Chemistry Faculty Publications

Exposure to nicotine alters the trafficking and assembly of nicotinic receptors (nAChRs), leading to their up-regulation on the plasma membrane. Although the mechanism is not fully understood, nicotine-induced up-regulation is believed to contribute to nicotine addiction. The effect of cotinine, the primary metabolite of nicotine, on nAChR trafficking and assembly has not been extensively investigated. We utilize a pH-sensitive variant of GFP, super ecliptic pHluorin, to differentiate between intracellular nAChRs and those expressed on the plasma membrane to quantify changes resulting from cotinine and nicotine exposure. Similar to nicotine, exposure to cotinine increases the number of α4β2 receptors on the …

Comparison Of The Crystal Structures Of 4,4′-Bis­­[3-(4-Methyl­Piperidin-1-Yl)Prop-1-Yn-1-Yl]-1,1′-Bi­Phenyl And 4,4′-Bis­­[3-(2,2,6,6-Tetra­Methyl­Piperidin-1-Yl)Prop-1-Yn-1-Yl]-1,1′-Biphen­Yl, Anqi Wan, Narsimha Reddy Penthala, E. Kim Fifer, Sean Parkin, Peter A. Crooks

Chemistry Faculty Publications

As part of a comprehensive program to discover α9α10 nicotinic acetyl­choline receptor antagonists, the title compounds C₃₀H₃₆N₂, (I), and C₃₆H₄₈N₂, (II), were synthesized by coupling 4,4′-bis­(3-bromo­prop-1-yn-1-yl)-1,1′-biphenyl with 4-methyl­piperidine and 2,2,6,6-tetra­methyl­piperidine, respectively, in aceto­nitrile at room temperature. In compound (I), the biphenyl system has a twisted conformation with a dihedral angle of 26.57 (6)° between the two phenyl rings of the biphenyl moiety, while in compound (II), the biphenyl moiety sits on a crystallographic inversion centre so the two phenyl rings are exactly coplanar. The terminal piperidine rings in …

Comparison Crystal Structure Conformations Of Two Structurally Related Biphenyl Analogues: 4,4'-Bis[3-(Pyrrolidin-1-Yl)Prop-1-Yn-1-Yl]-1,1'-Biphenyl And 4,4'-Bis{3-[(S)-2-Methylpyrrolidin-1-Yl]Prop-1-Yn-1-Yl}-1,1'-Biphenyl, Anqi Wan, Narsimha Reddy Penthala, E. Kim Fifer, Sean Parkin, Peter A. Crooks

Chemistry Faculty Publications

The title compounds, C₂₆H₂₈N₂, (I), and C₂₈H₃₂N₂, (II), were designed based on the structure of the potent 910 nicotinic acetyl­choline receptor antagonist ZZ161C {1,1'-[[1,1'-biphen­yl]-4,4'-diylbis(prop-2-yne-3,1-di­yl)]bis­(3,4-di­methyl­pyridin-1-ium) bromide}. In order to improve the druglikeness properties of ZZ161C for potential oral administration, the title compounds (I) and (II) were prepared by coupling 4,4'-bis­(3-bromo­prop-1-yn-1-yl)-1,1'-biphenyl with pyrrol­idine, (I), and (S)-2-methyl­pyrrolidine, (II), respectively, in aceto­nitrile at room temperature. The asymmetric unit of (I) contains two half mol­ecules that each sit on sites of crystallographic inversion. As a result, the biphenyl ring systems in …

Heterogeneous Oxidation Of Catechol, Elizabeth A. Pillar, Ruixin Zhou, Marcelo I. Guzman

Chemistry Faculty Publications

Natural and anthropogenic emissions of aromatic hydrocarbons from biomass burning, agro-industrial settings, and fossil fuel combustion contribute precursors to secondary aerosol formation (SOA). How these compounds are processed under humid tropospheric conditions is the focus of current attention to understand their environmental fate. This work shows how catechol thin films, a model for oxygenated aromatic hydrocarbons present in biomass burning and combustion aerosols, undergo heterogeneous oxidation at the air–solid interface under variable relative humidity (RH = 0–90%). The maximum reactive uptake coefficient of O₃(g) by catechol γ_O3 = (7.49 ± 0.35) × 10^–6 occurs for …

Localization Length Scales Of Triplet Excitons In Singlet Fission Materials, Sam L. Bayliss, Karl J. Thorley, John E. Anthony, Hélène Bouchiat, Neil C. Greenham, Alexei D. Chepelianskii

Chemistry Faculty Publications

We measure the dielectric confinement length scales of triplet excitons in organic semiconductors by jointly measuring their microwave-domain electric and magnetic susceptibilities. We apply this technique to characterize triplet excitons in two singlet fission materials with distinct solid-state packing and correlate the extracted localization length scales with the role of the excitonic environment. By using the magnetic susceptibility simultaneously determined through our experiments, we compare the independently extracted dielectric and spin-spin localization length scales, highlighting the role of local anisotropy on the properties of excitonic triplet states.

Far From 'Easy' Spectroscopy With The 8Π And Griffin Spectrometers At Triumf-Isac, Steven W. Yates, P. E. Garrett, A. J. Radich, J. M. Allmond, C. Andreoiu, G. C. Ball, P. C. Bender, L. Bianco, V. Bildstein, H. Bidaman, R. Braid

Chemistry Faculty Publications

The 8π spectrometer, installed at the TRIUMF-ISAC facility, was the world's most sensitive γ-ray spectrometer dedicated to β-decay studies. A description is given of the 8π spectrometer and its auxiliary detectors including the plastic scintillator array SCEPTAR used for β-particle tagging and the Si(Li) array PACES for conversion electron measurements, its moving tape collector, and its data acquisition system. The recent investigation of the decay of ¹²⁴Cs to study the nuclear structure of ¹²⁴Xe, and how the β-decay measurements complemented previous Coulomb excitation studies, is highlighted, including the extraction of the deformation parameters for the excited 0^{+ …}

Quantitative Analysis Of The Density Of Trap States At The Semiconductor-Dielectric Interface In Organic Field-Effect Transistors, Peter J. Diemer, Zachary A. Lamport, Yaochuan Mei, Jeremy W. Ward, Katelyn P. Goetz, Wei Li, Marcia M. Payne, Martin Guthold, John E. Anthony, Oana D. Jurchescu

Chemistry Faculty Publications

The electrical properties of organic field-effect transistors are governed by the quality of the constituting layers, and the resulting interfaces. We compare the properties of the same organic semiconductor film, 2,8-difluoro- 5,11-bis (triethylsilylethynyl) anthradithiophene, with bottom SiO₂ dielectric and top Cytop dielectric and find a 10× increase in charge carrier mobility, from 0.17 ± 0.19 cm² V⁻¹ s⁻¹ to 1.5 ± 0.70 cm² V⁻¹ s⁻¹, when the polymer dielectric is used. This results from a significant reduction of the trap density of states in the semiconductor band-gap, and a decrease in the …

Enzyme Localization, Crowding, And Buffers Collectively Modulate Diffusion-Influenced Signal Transduction: Insights From Continuum Diffusion Modeling, Peter M. Kekenes-Huskey, Changsun Eun, J. A. Mccammon

Chemistry Faculty Publications

Biochemical reaction networks consisting of coupled enzymes connect substrate signaling events with biological function. Substrates involved in these reactions can be strongly influenced by diffusion “barriers” arising from impenetrable cellular structures and macromolecules, as well as interactions with biomolecules, especially within crowded environments. For diffusion-influenced reactions, the spatial organization of diffusion barriers arising from intracellular structures, non-specific crowders, and specific-binders (buffers) strongly controls the temporal and spatial reaction kinetics. In this study, we use two prototypical biochemical reactions, a Goodwin oscillator, and a reaction with a periodic source/sink term to examine how a diffusion barrier that partitions substrates controls reaction …

Boron-Rich Benzene And Pyrene Derivatives For The Detection Of Thermal Neutrons, Henok A. Yemam, Adam Mahl, Unsal Koldemir, Tyler Remedes, Sean Parkin, Uwe Greife, Alan Sellinger

Chemistry Faculty Publications

A synthetic methodology is developed to generate boron rich aromatic small molecules based on benzene and pyrene moieties for the detection of thermal neutrons. The prepared aromatic compounds have a relatively high boron content up to 7.4 wt%, which is important for application in neutron detection as ¹⁰B (20% of natural abundance boron) has a large neutron induced reaction cross-section. This is demonstrated by preparing blends of the synthesized molecules with fluorescent dopants in poly(vinyltoluene) matrices resulting in comparable scintillation light output and neutron capture as state-of-the art commercial scintillators, but with the advantage of much lower cost. The …

Secondary Organic Aerosol Formation From The Β-Pinene+No3 System: Effect Of Humidity And Peroxy Radical Fate, C. M. Boyd, J. Sanchez, L. Xu, Alexis J. Eugene, T. Nah, W. Y. Tuet, Marcelo I. Guzman, N. L. Ng

Chemistry Faculty Publications

The formation of secondary organic aerosol (SOA) from the oxidation of β-pinene via nitrate radicals is investigated in the Georgia Tech Environmental Chamber (GTEC) facility. Aerosol yields are determined for experiments performed under both dry (relative humidity (RH) < 2 %) and humid (RH = 50 % and RH = 70 %) conditions. To probe the effects of peroxy radical (RO₂) fate on aerosol formation, "RO₂ + NO₃ dominant" and "RO₂ + HO₂ dominant" experiments are performed. Gas-phase organic nitrate species (with molecular weights of 215, 229, 231, and 245 amu, which likely correspond to molecular formulas of C₁₀H₁₇NO₄, C₁₀H₁₅NO₅, C₁₀H₁₇NO …

Crystal Structure Of Orthorhombic {Bis-[(Pyridin-2-Yl)Methyl](3,5,5,5-Tetrachloropentyl)Amine-Κ3N,N',N''}Chloridocopper(Ii) Perchlorate, Katherine A. Bussey, Annie R. Cavalier, Jennifer R. Connell, Margaret E. Mraz, Kayode D. Oshin, Tomislav Pintauer, Danielle L. Gray, Sean Parkin

Chemistry Faculty Publications

In the title compound, [CuCl(C₁₇H₁₉Cl₄N₃)]ClO₄, the Cu^II ion adopts a distorted square-planar geometry defined by one chloride ligand and the three nitro­gen atoms from the bis­[(pyridin-2-yl)meth­yl](3,5,5,5-tetra­chloro­pent­yl)amine ligand. The perchlorate counter-ion is disordered over three sets of sites with refined occupancies 0.0634 (17), 0.221 (16) and 0.145 (7). In addition, the hetero-scorpionate arm of the bis­[(pyridin-2-yl)meth­yl](3,5,5,5-tetra­chloro­pent­yl)amine ligand is disordered over two sets of sites with refined occupancies 0.839 (2) and 0.161 (2). In the crystal, weak Cu⋯Cl inter­actions between symmetry-related mol­ecules create a dimerization with a chloride occupying the apical …

Low-Voltage Polymer/Small-Molecule Blend Organic Thin-Film Transistors And Circuits Fabricated Via Spray Deposition, Simon Hunter, Jeremy W. Ward, Marcia M. Payne, John E. Anthony, Oana D. Jurchescu, Thomas D. Anthopoulos

Chemistry Faculty Publications

Organic thin-film electronics have long been considered an enticing candidate in achieving high-throughput manufacturing of low-power ubiquitous electronics. However, to achieve this goal, more work is required to reduce operating voltages and develop suitable mass-manufacture techniques. Here, we demonstrate low-voltage spray-cast organic thin-film transistors based on a semiconductor blend of 2,8-difluoro- 5,11-bis (triethylsilylethynyl) anthradithiophene and poly(triarylamine). Both semiconductor and dielectric films are deposited via successive spray deposition in ambient conditions (air with 40%–60% relative humidity) without any special precautions. Despite the simplicity of the deposition method, p-channel transistors with hole mobilities of >1 cm²/Vs are realized at −4 …

The Neutron Time-Of-Flight Cross Section Program At The University Of Kentucky - Adventures In Analysis Ii, J. R. Vanhoy, S. F. Hicks, B. C. Combs, B. P. Crider, A. J. French, E. A. Garza, S. L. Henderson, T. J. Howard, S. H. Liu, S. Nigam, R. L. Pecha, E. E. Peters, Francisco M. Prados-Estévez, Marcus T. Mcellistrem, B. J. Rice, T. J. Ross, Z. C. Santonil, L. C. Sidwell, J. L. Steves, Steven W. Yates

Chemistry Faculty Publications

Elastic and inelastic neutron differential cross sections are measured at the University of Kentucky Accelerator Laboratory (www.pa.uky.edu/accelerator/) at incident energies in the fast neutron region. The laboratorys facilities and instrumentation will be described and our measurement and analysis procedures outlined. Many corrections are required for neutron scattering experiments and the analysis utilizes information from many other cross section data sets and model calculations. Exploring and understanding the limitations of the foundational information and procedures are important for controlling the accuracy of the cross section results. We are examining the limitations in neutron detection efficiency, the normalization of (n,n′ …

“No-Spin” States And Low-Lying Structures In 130Xe And 136Xe, T. J. Ross, E. E. Peters, Anagha Chakraborty, B. P. Crider, Ajay Kumar, S. H. Liu, Marcus T. Mcellistrem, Francisco M. Prados-Estévez, J. R. Vanhoy, Steven W. Yates

Chemistry Faculty Publications

Inelastic neutron scattering on solid ¹³⁰XeF₂ and ¹³⁶XeF₂ targets was utilized to populate excited levels in ¹³⁰Xe and ¹³⁶Xe. When calculating nuclear matrix elements vital to the understanding of double-beta decay, it is important to have a clear understanding of the low-lying level structure of both the parent and daughter nucleus. Of particular relevance to double-beta decay searches are the assignments of 0⁺ states. We show here that in the case of ¹³⁰Xe there are several discrepancies in the adopted level structure. We found that one previous 0⁺ candidate level (1590 …

Studies Of 54,56Fe Neutron Scattering Cross Sections, S. F. Hicks, J. R. Vanhoy, A. J. French, S. L. Henderson, T. J. Howard, R. L. Pecha, Z. C. Santonil, B. P. Crider, S. Liu, Marcus T. Mcellistrem, E. E. Peters, Francisco M. Prados-Estévez, T. J. Ross, Steven W. Yates

Chemistry Faculty Publications

Elastic and inelastic neutron scattering differential cross sections and γ-ray production cross sections have been measured on ^54,56Fe at several incident energies in the fast neutron region between 1.5 and 4.7 MeV. All measurements were completed at the University of Kentucky Accelerator Laboratory (UKAL) using a 7-MV Model CN Van de Graaff accelerator, along with the neutron production and neutron and γ-ray detection systems located there. The facilities at UKAL allow the investigation of both elastic and inelastic scattering with nearly mono-energetic incident neutrons. Time-of-flight techniques were used to detect the scattered neutrons for the differential cross section measurements. …

Dipole Strength Distributions From Higs Experiments, V. Werner, N. Cooper, P. M. Goddard, P. Humby, R. S. Ilieva, G. Rusev, J. Beller, C. Bernards, B. P. Crider, J. Isaak, J. H. Kelley, E. Kwan, B. Löher, E. E. Peters, N. Pietralla, C. Romig, D. Savran, M. Scheck, A. P. Tonchev, W. Tornow, Steven W. Yates, M. Zweidinger

Chemistry Faculty Publications

A series of photon scattering experiments has been performed on the double-beta decay partners ⁷⁶Ge and ⁷⁶Se, in order to investigate their dipole response up to the neutron separation threshold. Gamma-ray beams from bremsstrahlung at the S-DALINAC and from Compton-backscattering at HIGS have been used to measure absolute cross sections and parities of dipole excited states, respectively. The HIGS data allows for indirect measurement of averaged branching ratios, which leads to significant corrections in the observed excitation cross sections. Results are compared to statistical calculations, to test photon strength functions and the Axel-Brink hypothesis

Inelastic Neutron Scattering Studies Of 76Ge And 76Se: Relevance To Elevance To Neutrinoless Double-Β Decay, B. P. Crider, E. E. Peters, T. J. Ross, Marcus T. Mcellistrem, Francisco M. Prados-Estévez, J. M. Allmond, J. R. Vanhoy, Steven W. Yates

Chemistry Faculty Publications

Inelastic neutron scattering measurements were performed at the University of Kentucky Accelerator Laboratory on enriched ⁷⁶Ge and ⁷⁶Se scattering samples. From measurements at incident neutron energies from 2.0 to 4.0 MeV, many new levels were identified and characterized in each nucleus; level lifetimes, transition probabilities, multipole mixing ratios, and other properties were determined. In addition, γ-ray cross sections for the ⁷⁶Ge(n,n′γ) reaction were measured at neutron energies up to 5.0 MeV, with the goal of determining the cross sections of γ rays in 2040-keV region, which corresponds to the region of interest in the neutrinoless double β …

Descant And Β-Delayed Neutron Measurements At Triumf, V. Bildstein, P. E. Garrett, S. F. Ashley, G. C. Ball, L. Bianco, D. Bandyopadhyay, J. Bangay, B. P. Crider, G. Demand, G. Deng, I. Dillman, A. Finlay, A. B. Garnsworthy, G. Hackman, B. Hadinia, R. Krücken, K. G. Leach, J-P. Martin, Marcus T. Mcellistrem, C. J. Pearson, E. E. Peters, Francisco M. Prados-Estévez, A. Radich, F. Sarazin, C. Sumithrarachchi, C. E. Svensson, J. R. Vanhoy, J. Wong, Steven W. Yates

Chemistry Faculty Publications

The DESCANT array (Deuterated Scintillator Array for Neutron Tagging) consists of up to 70 detectors, each filled with approximately 2 liters of deuterated benzene. This scintillator material o_ers pulse-shape discrimination (PSD) capabilities to distinguish between neutrons and γ-rays interacting with the scintillator material. In addition, the anisotropic nature of n – d scattering allows for the determination of the neutron energy spectrum directly from the pulse height spectrum, complementing the traditional time-of-flight (ToF) information. DESCANT can be coupled either to the TIGRESS (TRIUMF-ISAC Gamma-Ray Escape …

Inelastic Neutron Scattering Studies Of 132,134Xe: Elucidating Structure In A Transitional Region And Possible Interferences For 0vββ Searches, E. E. Peters, T. J. Ross, B. P. Crider, S. F. Ashley, Anagha Chakraborty, M. D. Hennek, Ajay Kumar, S. H. Liu, Marcus T. Mcellistrem, Francisco M. Prados-Estévez, J. S. Thrasher, Steven W. Yates

Chemistry Faculty Publications

Highly enriched (> 99.9%) ¹³²Xe and ¹³⁴Xe gases were converted to solid ¹³²XeF₂ and ¹³⁴XeF₂ and were used as scattering samples for inelastic neutron scattering measurements at the University of Kentucky Accelerator Laboratory (UKAL). Lifetimes of levels up to 3.5MeV in excitation energy in these xenon isotopes were measured using the Doppler-shift attenuation method, allowing the determination of reduced transition probabilities. Gamma rays corresponding to new transitions and levels have been observed. In particular, tentative new excited 0⁺ states and associated decays have been examined in an effort to elucidate the structure of …

Bh2 Revisited: New, Extensive Measurements Of Laser-Induced Fluorescence Transitions And Ab Initio Calculations Of Near-Spectroscopic Accuracy, Fumie X. Sunahori, Mohammed Gharaibeh, Dennis J. Clouthier, Riccardo Tarroni

Chemistry Faculty Publications

The spectroscopy of gas phase BH₂ has not been explored experimentally since the pioneering study of Herzberg and Johns in 1967. In the present work, laser-induced fluorescence (LIF) spectra of the òB₁(Πu)-X̃²A₁ band system of ¹¹BH₂, ¹⁰BH₂, ¹¹BD₂, and ¹⁰BD₂ have been observed for the first time. The free radicals were "synthesized" by an electric discharge through a precursor mixture of 0.5% diborane (B₂H₆ or B₂D₆) in high pressure argon at the exit of …

Collectivity Of 0+ States In 160Gd, S. R. Lesher, C. Casarella, A. Aprahamian, B. P. Crider, R. Ikeyama, I. R. Marsh, Marcus T. Mcellistrem, Erin E. Peters, F. M. Prados-Estévez, M. K. Smith, Z. R. Tully, J. R. Vanhoy, Steven W. Yates

Chemistry Faculty Publications

Excited 0⁺ states in ¹⁶⁰Gd have been examined with the (n,n′γ) reaction at incident neutron energies up to 2.8 MeV. Gamma-ray excitation functions and angular distribution measurements allow the confirmation of the existence of 0⁺ states at 1379.70 keV and 1558.30 keV, but we reject the assignments of additional previously suggested 0⁺ candidates. Limits on the level lifetimes of the observed 0⁺ states permit an evaluation of the collectivity of these states.

Ground-State And Pairing-Vibrational Bands With Equal Quadrupole Collectivity In 124Xe, A. J. Radich, P. E. Garrett, J. M. Allmond, C. Andreoiu, G. C. Ball, L. Bianco, V. Bildstein, S. Chagnon-Lessard, D. S. Cross, G. A. Demand, A. Diaz Varela, R. Dunlop, P. Finlay, A. B. Garnsworthy, G. Hackman, B. Hadinia, B. Jigmeddorj, A. T. Laffoley, K. G. Leach, J. Michetti-Wilson, J. N. Orce, M. M. Rajabali, E. T. Rand, K. Starosta, C. S. Sumithrarachchi, C. E. Svensson, S. Triambak, Z. M. Wang, J. L. Wood, J. Wong, S. J. Williams, Steven W. Yates

Chemistry Faculty Publications

The nuclear structure of ¹²⁴Xe has been investigated via measurements of the β+/EC decay of ¹²⁴Cs with the 8πγ-ray spectrometer at the TRIUMF-ISAC facility. . . .

For the remainder of this abstract, please visit: http://dx.doi.org/10.1103/PhysRevC.91.044320

Applied Quantum Chemistry: Spectroscopic Detection And Characterization Of The F2Bs And Cl2Bs Free Radicals In The Gas Phase, Bing Jin, Phillip M. Sheridan, Dennis J. Clouthier

Chemistry Faculty Publications

In this and previous work [D. J. Clouthier, J. Chem. Phys. 141, 244309 (2014)], the spectroscopic signatures of the X₂BY (X = H, halogen, Y = O, S) free radicals have been predicted using high level ab initio theory. The theoretical results have been used to calculate the electronic absorption and single vibronic level (SVL) emission spectra of the radicals under typical jet-cooled conditions. Using these diagnostic predictions, the previously unknown F₂BS and Cl₂BS free radicals have been identified and characterized. The radicals were prepared in a free jet expansion by subjecting precursor …

Capillary Effects In Guided Crystallization Of Organic Thin Films, Alta Fang, Anna K. Hailey, Abigail Grosskopf, John E. Anthony, Yueh-Lin Loo, Mikko Haataja

Chemistry Faculty Publications

Recently, it has been demonstrated that solvent-vapor-induced crystallization of triethylsilylethynyl anthradithiophene (TES ADT) thin films can be directed on millimeter length scales along arbitrary paths by controlling local crystal growth rates via pre-patterning the substrate. Here, we study the influence of capillary effects on crystallization along such channels. We first derive an analytical expression for the steady-state growth front velocity as a function of channel width and validate it with numerical simulations. Then, using data from TES ADT guided crystallization experiments, we extract a characteristic channel width, which provides the smallest feature size that can be obtained by this technique.

Photophysics Of Organic Semiconductors: From Ensemble To The Single-Molecule Level, Rebecca Grollman, Whitney E. B. Shepherd, Alexander Robertson, Keshab R. Paudel, John E. Anthony, Oksana Ostroverkhova

Chemistry Faculty Publications

We present photophysical properties of functionalized anthradithiophene (ADT) and pentacene (Pn) derivatives, as well as charge and energy transfer properties of donor-acceptor (D/A) pairs of these derivatives. All molecules studied were fluorescent and photostable enough to be imaged on the single-molecule level in a variety of polymeric and in a functionalized benzothiophene (BTBTB) crystalline host using room-temperature wide- field epifluorescence microscopy. Flexibility of functionalization of both guest (ADT, Pn) and host (BTBTB or polymer) molecules can be used for systematic studies of nanoscale morphology and photophysics of D/A organic semiconductor bulk heterojunctions, as well as in applications relying on FRET, …

Repressive Mutations Restore Function-Loss Caused By The Disruption Of Trimerization In Escherichia Coli Multidrug Transporter Acrb, Zhaoshuai Wang, Meng Zhong, Wei Lu, Qian Chai, Yinan Wei

Chemistry Faculty Publications

AcrAB-TolC and their homologs are major multidrug efflux systems in Gram-negative bacteria. The inner membrane component AcrB functions as a trimer. Replacement of Pro223 by Gly in AcrB decreases the trimer stability and drastically reduces the drug efflux activity. The goal of this study is to identify suppressor mutations that restore function to mutant AcrB_P223G and explore the mechanism of function recovery. Two methods were used to introduce random mutations into the plasmid of AcrB_P223G. Mutants with elevated drug efflux activity were identified, purified, and characterized to examine their expression level, trimer stability, interaction with AcrA, and …

Design Of Organic Ternary Blends And Small-Molecule Bulk Heterojunctions: Photophysical Considerations, Kallarakkal Ramakrishnan Rajesh, Keshab Paudel, Brian Johnson, Rawad Hallani, John E. Anthony, Oksana Ostroverkhova

Chemistry Faculty Publications

We explored relationships between photophysical processes and solar cell characteristics in solution-processable bulk heterojunctions (BHJs), in particular: (1) polymer donor:fullerene acceptor:small-molecule (SM) nonfullerene acceptor, (2) polymer donor:SM donor:SM nonfullerene acceptor, and (3) SM donor:SM nonfullerene or fullerene acceptor. Addition of a nonfullerene SM acceptor to “efficient” polymer:fullerene BHJs led to a reduction in power conversion efficiency (PCE), mostly due to decreased charge photogeneration efficiency and increased disorder. By contrast, addition of an SM donor to “inefficient” polymer:SM nonfullerene acceptor BHJs led to a factor of two to three improvement in the PCE, due to improved charge photogeneration efficiency and transport. …