A5055136612- Terahertz technology and applications
- Spectroscopy and Quantum Chemical Studies
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Crystallography and molecular interactions
- Advanced Chemical Physics Studies
- Solid-state spectroscopy and crystallography
- Spectroscopy and Laser Applications
- Metal-Organic Frameworks: Synthesis and Applications
- Organic and Molecular Conductors Research
- Molecular Spectroscopy and Structure
- Molecular Junctions and Nanostructures
- Organic Electronics and Photovoltaics
- Nonlinear Optical Materials Research
- Acoustic Wave Resonator Technologies
- Advanced NMR Techniques and Applications
- Material Dynamics and Properties
- Advanced Chemical Sensor Technologies
- Thermal properties of materials
- Plant and animal studies
- Methane Hydrates and Related Phenomena
- Crystallography and Radiation Phenomena
- Mechanical and Optical Resonators
- Luminescence and Fluorescent Materials
- Perovskite Materials and Applications
University of Rochester
2024-2025
University of Vermont
2018-2024
University of Cambridge
2016-2022
Burlington College
2019-2020
Syracuse University
2014-2019
PRG S&Tech (South Korea)
2014-2017
Bridge University
2016
Smithsonian Institution
2003-2005
United States Geological Survey
2001-2005
National Park Service
1995
Molecular vibrations play a critical role in the charge transport properties of weakly van der Waals bonded organic semiconductors. To understand which specific phonon modes contribute most strongly to electron-phonon coupling and ensuing thermal energetic disorder some widely studied high-mobility molecular semiconductors, state-of-the-art quantum mechanical simulations vibrational constants are combined with experimental measurements low-frequency using inelastic neutron scattering...
Recrystallization of amorphous drugs is currently limiting the simple approach to improve solubility and bioavailability poorly water-soluble by amorphization a crystalline form drug. In view this, molecular mobility, α-relaxation β-relaxation processes with associated transition temperatures Tgα Tgβ, was investigated using dynamic mechanical analysis (DMA). The correlation between onset recrystallization for nine drugs, stored under dry conditions at temperature 296 K, determined. From...
The intermolecular anharmonic potential of crystalline purine is probed by means temperature-dependent terahertz time-domain spectroscopy, low-frequency Raman scattering, X-ray diffraction, and ab initio quasi-harmonic quantum-chemical simulations. As temperature increases, anharmonicity in the interactions results strongly anisotropic thermal expansion - with a negative along b crystallographic axis yielding corresponding bulk structural modifications. observed thermally-induced shifts most...
We present experimental and computational evidence that gate-opening modes for zeolitic imidazole frameworks can be observed at terahertz frequencies. Our work highlights the critical importance to correctly optimise crystal structure prior lattice dynamics analysis. The results support hypothesis low energy vibrational do indeed play a significant role in host-guest interactions ZIFs, such as gas loading.
Abstract The rigidity of poly‐ l ‐proline is an important contributor to the stability many protein secondary structures, where it has been shown strongly influence bulk flexibility. experimental Young's moduli two known helical forms, right‐handed all‐ cis (Form I) and left‐handed trans II), were determined in crystalline state by using approach that combines terahertz time‐domain spectroscopy, X‐ray diffraction, solid‐state density functional theory. Contrary expectations, helices found be...
The ability of l-glutamic acid to crystallize in two different forms has long been the subject study due its commercial importance. While a solvent-mediated phase transformation between α and β polymorphs is prevailing theory, recent reports indicate thermal solid–solid may be possible. However, determining accurate thermodynamic stabilities these crystals challenging. Here new low-temperature single-crystal X-ray diffraction data coupled solid-state density functional theory simulations...
We show clear evidence for a theory proposing that the shape and structure of PES is fundamental factor underlying dynamics at temperatures below glass transition.
Anharmonicity has been shown to be an important piece of the fundamental framework that dictates numerous observable phenomena. In particular, anharmonicity is driving force vibrational relaxation processes, mechanisms are integral proper function chemical processes. However, elucidating its origins proven difficult due experimental and theoretical challenges, specifically related separating anharmonic contributions from other unrelated effects. While no one technique particularly suited for...
Significance Intrinsic fluorescence of nonaromatic amino acids is a puzzling phenomenon with an enormous potential in biophotonic applications. The physical origins this effect, however, remain elusive. Herein, we demonstrate how specific hydrogen bond networks can modulate fluorescence. We highlight the key role played by short bonds, present protein structure, on ensuing provide detailed experimental and molecular evidence to explain these unusual optical properties. Our findings should...
Identifying and characterizing intermolecular forces in the condensed phase is crucial for understanding both micro- macroscopic properties of solids; ranging from solid-state reactivity to thermal expansion. Insight into these interactions enables a holistic comprehension bulk properties, thus them has direct implications supramolecular design. However, even modest changes can create unpredictable structures dynamics. For example, copper(II) acetylacetonate (Cu(C5}H7O2)2)...
We introduce a general approach for the simulation of quantum vibrational states (symmetric and asymmetric) double-well potentials in molecules materials thermodynamic spectroscopic applications. The method involves solving nuclear Schrödinger equation associated with one-mode potential type V(Q) = aQ2 + bQ3 cQ4 (with < 0 c > 0) thus explicitly includes effects. potential, V(Q), is obtained from density functional theory (DFT) calculations performed at displaced configurations along selected...
Cellulose is a common polymer found in natural sources, with the potential to be used wide variety of green and technologically-relevant applications. Despite years effort, precise 3D structure two crystalline polymorphs cellulose, I_alpha I_beta, are currently still unknown due presence disorder intermolecular hydrogen bond networks, hampering an in-depth understanding structure-property relation this material. Disorder networks cellulose I was investigated terahertz spectroscopy, powder...
The low-frequency motions of molecules in the condensed phase have been shown to be vital a large number physical properties and processes. However, case disordered systems, it is often difficult elucidate atomic-level details surrounding these phenomena. In this work, we performed an extensive experimental computational study on molecular solid camphor, which exhibits rich complex structure-dynamics relationship, undergoes order-disorder transition near ambient conditions. combination x-ray...
The identification and characterization of low-frequency vibrational motions metal–organic frameworks (MOFs) allows for a better understanding their mechanical structural response upon perturbation by external stimuli such as temperature, pressure, adsorption. Here, we describe the combination temperature- pressure-dependent terahertz spectroscopy measurements with quantum simulations to measure assign specific modes that directly drive mechanochemical properties this important class porous...
Metal-aqua ion ([M(H2O)n](X+)) formation is a fundamental step in mechanisms that are central to enzymatic and industrial catalysis. Past investigations of such ions have yielded wealth information regarding their properties, however questions still exist involving the exact structures these complexes. A prominent example this hexaaqua copper(II) ([Cu(H2O)6](2+)), with solution versus gas-phase configurations under debate. The differences often attributed intermolecular interactions between...
Zr-oxide secondary building units construct metal-organic framework (MOF) materials with excellent gas adsorption properties and high mechanical, thermal, chemical stability. These attributes have led MOFs to be well-recognized for a wide range of applications, including storage separation, catalysis, as well healthcare domain. Here, we report structure search methods within the Cambridge Structural Database (CSD) create curated subset 102 synthesized date, bringing unique record all...
The two major polymorphs of the active pharmaceutical ingredient indomethacin were studied using a combination experimental low-frequency vibrational spectroscopies, theoretical solid-state density functional theory, and ab initio molecular dynamics calculations. results enable complete spectral assignment IR Raman spectra, yield new insight into energetic dynamical factors present within solids to be understood. Ultimately, these are used rationalize thermodynamic properties crystals, which...
The anisotropic mechanical response of ZIF-8 and ZIF-67 is investigated as a function pressure its main features (including shear-destabilization eventually leading to amorphization) discussed in terms specific lattice vibrations structural changes occurring the framework. At zero pressure, two ZIFs are characterized by an elastic anisotropy with directions maximum minimum stiffness along $\ensuremath{\langle}111\ensuremath{\rangle}$ $\ensuremath{\langle}100\ensuremath{\rangle}$,...
In this study, a method is described to determine the monolayer loading capacity (MLC) of drugs naproxen and ibuprofen, both having high recrystallization tendencies, in mesoporous silica (MS), well known carrier that able stabilize amorphous form drug. The stabilization has been suggested be due direct absorption drug molecules onto MS surface, i.e. monolayer. addition, not contact with surface can fill pores up its pore filling (PFC) potentially stabilized by confinement size being smaller...
In ZIF-8 and its cobalt analogue ZIF-67, the imidazolate methyl-groups, which point directly into void space, have been shown to freely rotate - even down cryogenic temperatures. Using a combination of experimental terahertz time-domain spectroscopy, low-frequency Raman state-of-the-art ab initio simulations, methyl-rotor dynamics in ZIF-67 are fully characterized within context quantum-mechanical hindered-rotor model. The results lend insight fundamental origins experimentally observed...