Seminars & Events

Throughout the academic year, the department hosts several seminars whose presenters range from department graduate students to internationally renowned professors and scientists. The calendar below includes all of our department seminars and events. It is updated frequently with titles and abstracts — you can subscribe using Google Calendar by clicking the "+GoogleCalendar" button in the lower right. 

Seminars

Friday Colloquium Series

Faculty members and graduate students invite professors from other institutions throughout the country and the world to speak at Brown on a Friday afternoon. Friday colloquiua topics span the various fields of chemistry represented by the department. Sometimes, a colloquium seminar is hosted jointly with another department or institute, such as IMNI, the Institute for Molecular and Nanoscale Innovation. Friday afternoons, 4:00pm - 5:00pm, MacMillan Hall 115. Refreshments served at 3:45pm.

Organic Chemistry Seminars

Organic chemistry graduate students are required to give at least two seminars. The first is a literature seminar on a topic of recent interest, and the second is the candidate's thesis research. Invited guests frequently present their research at Organic Seminars as well. Tuesday afternoons, 12:00pm - 1:00pm, GeoChem 351.

Inorganic Chemistry Seminars

Inorganic chemistry graduate students are expected to present one seminar per year on their own research or on another topic of current interest in inorganic chemistry. Research associates, faculty and invited guests often present inorganic seminars as well. Thursday afternoons, 12:00pm - 1:00pm, GeoChem 351.

Physical Chemistry Tea Sessions

Physical chemistry graduate students are expected to present one seminar per year. Topics covered include the graduate students' topics of interest with regard to current research, as well as their own research. Thursday afternoons, 3:00pm - 4:00pm, GeoChem 349/351. Light refreshments served at 2:45pm. 

   

Upcoming Events

  • Understanding actinide-ligand covalency is at the center of efforts to design new separations schemes for spent nuclear fuel, and thus features considerable practical importance. NMR spectroscopy is a widely available means of measuring 5f covalency that is complementary to more established methods, such optical spectroscopy and XANES. However, it has been rarely expolited for this purpose in the past. Herein, I will disucss our efforts to develop NMR spectroscopy for the evaluation the electronic structure of diamagnetic actinide complexes. For example, we recently prepared the bridged thorium nitride complex, [K(18-crown-6)][(R2N)3Th(m-N)(Th(NR2)3] (R = SiMe3), and analyzed its electronic structure by 15N NMR spectroscopy and DFT calculations. This analysis reveals that the Th-Nnitride bond in [(R2N)3Th(m-N)(Th(NR2)3]- features more covalency and a greater degree of bond multiplicity than comparable thorium imido and chalcogenido complexes.

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  • The nanoparticles we make today to address problems in energy and human health will enter the environment tomorrow. But will they be benign or will they lead to deleterious downstream effects to our environment? The Center for Sustainable Nanotechnology is developing and benchmarking design principles for sustainable nanoparticles. In our earlier studies, [J. Chem. Phys. 138, 184903 (2013)] we discovered that coarse-grained Janus nanoparticles can reproduce the structure of the fine-grained particles. However, the dynamics is substantially accelerated. While dissipation can be introduced to rescale the time scales appropriate to obtain accurate diffusional properties, it fails to obtain the correct time scales for higher-order correlation functions. This suggests a need for a dynamically consistent coarse-graining that provides the correct time scales for all orders. [J. Phys. Chem. B 120, 7297 (2016)] We will report our progress in addressing this challenge in the context of sustainable nanoparticles and use fine-grained representations for comparison. We will also demonstrate the implications of these methods on the interactions between nanoparticles and model membranes from Gram-negative bacteria.

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  • Advancing Science Through Diversity

    The Open Chemistry Collaborative in Diversity Equity (OXIDE) is aimed at institutional reform so as to lower inequitable barriers hindering the success of faculty from diverse groups. Professor Rigoberto Hernandez (Johns Hopkins University) will report on OXIDE’s approaches to increase awareness of effective policies and practices that decrease inequitable barriers and improve the diversity climate in chemistry departments.

    If you are interested in joining the Department of Chemistry’s workshop “Advancing Science Through Diversity”, contact [email protected]

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  • Abstract: The rates of chemical reactions (or any activated process) are by definition determined by the flux of reactants (or initial states) that end up as products (or final states). Through the last hundred years of studies on reaction rate theory, it has become clear that this can be equated to the flux through any surface that divides reactants from products as long as only those trajectories that end up as products are included in the flux. Transition state theory (TST) ignores this last clause. It thereby overestimates the rate if any of the trajectories recross the dividing surface. However, its advantage is that it replaces a dynamical calculation with a geometric one. Through the variational principle or perturbation theory, however, one can construct non-recrossing dividing surfaces that lead to exact rates. [Chem. Phys. 370, 270-276 (2010)] These approaches are limited by the nature of the search space of surfaces and the reference dividing surface, respectively. We discovered that the Lagrangian descriptor can be used to resolve the dividing surface directly, [Phys. Rev. Lett. 115, 148301 (2015)] and used it to resolve the reaction geometry of dissipative and driven chemical reactions with increasing complexity. As an aside, it lent itself to the determination of periodic orbits associated with bound motion. We will discuss the accuracy of the method for barrierless reactions, model reactions, ketene isomerization, and LiCN isomerization.

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  • The advent of tabletop sources of intense terahertz pulses has enabled rapid advances in the nascent subfield of nonlinear THz spectroscopy. Terahertz fields can be used to drive collective and molecular electronic, vibrational, and spin responses as well as gas-phase molecular rotations. In some cases, far-from-equilibrium responses including drastic changes in electronic energetics and spectra and electronic and structural phase transitions and can be induced by THz fields.

    Generation and enhancement of strong THz fields will be discussed briefly, and THz light-matter interactions will be reviewed. Examples of highly nonlinear responses to THz electric fields, including colossal Stark shifts and electroluminescence of quantum dots and quantum phase transitions that are monitored using THz, optical, and x-ray probes will be illustrated. Finally, linear and nonlinear THz rotational and electron paramagnetic resonance (EPR) spectroscopy will be discussed.

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  • Abstract: Thermal density functional theory is common in simulations of high-temperature, high-density materials, despite the scarcity of explicitly temperature-dependent electron interaction free energy approximations and disagreement over the impact of these missing thermal effects on calculated properties. Insights from both ensemble density functional theory and the electronic strong-interaction limit can be applied to thermal ensembles, creating new approximation schemes and serving to connect these branches of formal theory with thermal density functional theory and its applications. Numerical demonstrations using the finite-temperature asymmetric Hubbard dimer and the uniform electron gas will be used to examine the advantages and disadvantages of the two approaches.

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  • Engineering Semiconductor Quantum Dots for Biosensing Applications

    Abstract: Semiconductor quantum dots (QDs) act as exceptionally bright photoluminescent beacons in biosensing applications. We build on core/shell material structures and their well-studied emission tuning to focus on biosensing applications through enhancement of the nanoparticle absorption cross-sections. Through absorption tuning of indium phosphide QDs, we have generated multiple colors of cadmium-free, brightness-matched QDs and studied the impact of QD shell thickness on Förster resonance energy transfer (FRET), including QD-QD FRET. Two sensor constructs enable the transduction of differential analyte binding by allosteric transcription factors (aTFs) into fluorescent outputs to quantify nanomolar concentrations of the model analyte. In one design, FRET between a QD and organic dye produces a ratiometric signal based on a change in distance between the analyte-bound and -unbound states. In a second design, the localization (or lack thereof) of QDs on the surface of a bead substrate depends on the presence or absence of the small molecule analyte. The change in spatial localization of the bright QD signal is easily discerned by eye and through analysis of digital images captured on a cell phone camera, enabling the sensitive detection of a small molecule without antibodies or expensive analytical instrumentation. Continued development of QDs and QD coatings for specific biosensing applications ensures that we are using the best nanomaterials for a given purpose

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    24
  • Mar
    13
  • Apr
    17
  • The recent surprising discovery of the salutary effects of low doses (50-200 ppm) of carbon monoxide (CO) in diseases like pulmonary arterial hypertension, COPD, and arterial wall lesions from balloon angioplasty has initiated intense research effort toward exploration of the therapeutic benefits of this so-called toxic gas. Results of such studies have also indicated that moderate doses (>250 ppm) of CO causes rapid reduction of cancer cells (but not normal cell) through cell apoptosis via disruption of mitochondrial function. In addition, CO dramatically sensitizes cancer cells to chemotherapy and imparts antiproliferative effect toward colon, breast, ovary, pancreas, and other cancers. Because of its toxic nature, it is however difficult to employ gaseous CO in hospital settings. We have recently shown that photoactive and biocompatible metal carbonyl complexes with designed ligands can deliver suitable doses of CO to cellular targets under the total control of light. In addition we have shown that these photosensitive CO-releasing molecules (photoCORMs) can be conveniently used to kill human breast and colon cancer cells in a dose-dependent manner through light-induced CO release. Recently we have been successful in incorporating several fluorescent photoCORMs within the pores of silica nanoparticles (SNPs) and have demonstrated (a) their accumulation within cancer cells, (b) fluorescence tracking of the process of CO delivery within the cancer cells, and (c) their eradication by a dose-dependent CO photo delivery. Results from these experiments as well their promise in translation to animal models will be discussed.

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  • May
    1