Pre-Applications to Sprout Program Due 4/17

Sprout logoThe Sprout Program is back!

Funded by the Provost’s Office and the Office of Technology Licensing (OTL), Sprout is designed to encourage and support translational research activity within the Brandeis community for faculty, postdocs, and student researchers (graduate and undergraduate) in the Division of Science. The awards (up to $25,000 – no overhead!) are intended to help to advance early-stage technologies to industry adoption thereby bringing your research and entrepreneurial ambitions to life.

Successful pre-applicants will be invited to submit a final application due in late May and to pitch to a panel of industry judges in early June. Pre-apply by April 17.

Herzfeld paper named “2023 Hot PCCP article”

images from Herzfeld paperIn a new paper (DOI: 10.1039/d2cp05648h), selected as a “2023 Hot PCCP article”, the Herzfeld group has shown that the “Lewis dot” representation of electrons can predict states that have otherwise been predicted only by the most advanced implementations of quantum mechanics.

Basically, the structures and reactions of molecules are controlled by the interactions of electrons with each other and with atomic nuclei. However, the process is complicated by the fact that wave properties are important for particles as light as electrons. The gold standard is to explicitly model these properties using wave mechanics. But it is convenient to have an implicit description that is more accessible and intuitive. These are the “Lewis dots” that are generally used to represent bonds and reaction mechanisms in chemistry courses and journal articles. Lewis dots are semi-classical particles: classical in the sense of being associated with a location in space, but non-classical in that they don’t stick to the oppositely charged nuclei and can have two different spin states.

In recent years, the Herzfeld group has sought to quantify this picture. A subtlety is that the interactions between electrons is spin dependent due to the antisymmetry of electron wave functions. This explains why electrons of unlike spin often form pairs. However, the charges of electrons should always repel one another and Linnett suggested already in 1961 that two electrons should only co-localize if they are both sufficiently attracted to the same inter-nuclear region. In their new paper, the Herzfeld group shows that, a careful representation of the effects of wave function anti-symmetry, leads to Linnett-like structures when there are not enough internuclear basins to induce all the electrons to form simple pairs. A striking example is given by benzene. The traditional semi-classical representation of benzene, as a resonance between two structures with alternating single and double bonds, is obviated by a structure with three electrons in each carbon-carbon bond (shown here with the six carbon kernels in teal, six hydrogen kernels in white, and 15 valence electrons of each spin in pink and magenta).

Publication: Emergence of Linnett’s “double quartets” from a model of “Lewis dots.” Judith Herzfeld. Physical Chemistry Chemical Physics, Issue 7, 2023.

Han receives DoD award to purchase X-ray diffraction instrument

Congratulations to Grace Han, Assistant Professor of Chemistry and Landsman Career Development Chair in the Sciences. She has been awarded funds from the Department of Defense to purchase a bench-top X-ray diffraction instrument. This award is part of the DoD’s Defense University Research Instrumentation Program (DURIP) that will provide $59 million in FY 2023 to purchase research equipment at 77 institutions across 30 states.

Changes in the properties of organic materials undergoing transition between solid and liquid phases are employed in a variety of applications, including thermal energy storage, cooling, and actuation. The ability to regulate such phase transitions by light opens up new opportunities to achieve functions with a high spatial precision, triggered by the rapid, remotely applied, and non-invasive stimulus. This capability enables novel applications including photo-controlled heat storage, adhesion, actuation, and catalyst recovery, which the Han group investigates.

The DURIP award from the Air Force Office of Scientific Research (AFOSR) and the Department of Defense (DoD) will enable the Han team to build a new research capability on campus. A non-ambient, benchtop X-ray diffractometer, equipped with light sources and a heating/cooling stage, will allow the group to study how molecules change their geometry and intermolecular interaction in response to irradiation and temperature change. This will yield a deep understanding of photoswitch designs that undergo facile structural changes in solid phase, assisting the discovery and development of light-responsive functional materials.

SciFest XI to be held on Thursday, 8/11/22

Save the Date for SciFest!

SciFest, the Division of Science’s annual celebration of undergraduate research, is a poster session featuring work done by undergraduates in Brandeis laboratories each summer. This is a capstone event for the undergraduate researchers where they can present the results of their research to peers, grad students, and faculty.

Join us for the SciFest XI which will be held on Thursday, August 11, 2022 in the Shapiro Science Center.

Grace Han and 2 Alumni Receive 2022 Sloan Foundation Fellowships

Grace Han group photo

Grace Han (left) and her group.

The Alfred P. Sloan Foundation has announced the winners of the 2022 Sloan Research Fellowships. These fellowships are awarded to early-career scientists that represent the most promising researchers working today. Winners receive $75,000, which can be used to support their research over a two-year term. Grace Han, Assistant Professor of Chemistry and the Landsman Career Development Chair in the Sciences is one of the 2022 recipients.

The major goal of Dr. Grace Han’s research program is to develop functional organic material systems that exhibit phase transitions triggered by external stimuli, notably light. The photo-controlled phase-change materials have a game-changing potential in waste heat recycling and storage, photo-actuation, photo-lithography, and photo-regulated adhesion. In particular, the novel strategy to optically ‘fix’ a liquid phase under fluctuating temperatures allows for a long-term latent heat storage and a triggered release of energy, which is not attainable by conventional phase-change materials such as paraffins or salt hydrates. To achieve this goal, her team investigates the photo-induced structural and polarity changes of molecular switches based on azobenzene, which reversibly controls the phase of materials.
The Sloan Research Fellowship will support the new direction of Han group’s research in expanding the materials set by the rational design of photoswitches with enhanced optical and thermal properties, which will address the challenges of the current state-of-the-art switches.
Two Brandeis alumni also received 2022 fellowships: Netta Engelhardt, BS ’11 (Physics) and Dapeng Bi, PhD ’12 (Physics).

Schmidt-Rohr examines why plants need two different photosystems

In a recent paper in Life (Basel), Klaus Schmidt-Rohr, Professor of Chemistry, introduces a self-explanatory description of the energetics of photosynthesis in plants, the so-called EZ-scheme. It shows the energies of molecules in kJ/mol instead of the classical Z-scheme’s shifted energy differences that are misleadingly encrypted in volts. Unlike its predecessor, the EZ-scheme includes the Kok cycle in the water-splitting complex, charge separation after photon absorption, and the Calvin cycle with carbohydrate synthesis (in a simplified form). It also shows O2 correctly as a high-energy product, due to its relatively weak double bond, and demonstrates that Photosystem II pumps more of the absorbed photon energy into O2 than into the plant.

This paper provides the first valid explanation of why plants need two different photosystems: PSII mostly extracts hydrogen (as protons plus electrons) from H2O, producing PQH2 (plastoquinol), and generates the energetically expensive product O2, providing little energy directly to the plant. PSI is needed to produce significant chemical energy for the organism, in the form of ATP, and to generate a less reluctant hydrogen donor, NADPH. This work fundamentally revises received notions of the energetics of photosynthesis, by pointing out the classical Z-scheme’s bewildering implication that H2O gives off electrons spontaneously to chlorophyll while releasing energy, and by showing that the concept of energy transport by “high-energy electrons” in photosynthesis is misguided, since energy and electrons flow in opposite directions.

Figure #1 from Schmidt-Rohr paper

Figure 1 Simplified EZ-scheme of the energetics of photosynthesis in plants, converting H2O and CO2 to O2 and carbohydrate, [CH2O]. The direction of energy transfer and release is indicated by straight red arrows at the top, formal hydrogen transfer by blue dashed curved arrows at the bottom of the diagram. Three dots … indicate omitted redox reactions.

Schmidt-Rohr K. O2 and Other High-Energy Molecules in Photosynthesis: Why Plants Need Two Photosystems. Life (Basel). 2021 Nov 5;11(11):1191.

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