We are currently looking for multiple people at the MS, PhD and Post Doctoral levels to fill open positions related to understanding electron transfer across solid/liquid water interfaces and building the ultimate in surface-specific vibrational spectroscopy. If you care about aqueous photo-electrochemistry (and you should), if you care about building better tools to probe molecular structure and reactivity at buried interfaces (and you should) this is an exciting time. For more details see the flyer: Open Positions
In a thoughtful attempt of the European Commission to combat the dismal Berlin fall weather November 28th brought the news that Kramer’s ERC Consolidator grant proposal — SOLWET: Electron Transfer Across Solid/Liquid Interfaces: Elucidating Elementary Processes from Femtoseconds to Seconds — was “retained for funding”. The generous support this includes will allow the dramatic expansion of our activities studying ultrafast (photo)electrochemistry. Stay tuned for more about what project encompasses and photos from a suitable celebratory activity (as soon as we decide what that might actually be 🙂 ).
Much work by many clever folks over the last 25 years has shown that, contra expectations from classical theories of solutions, some — mostly larger, polarizable — anions adsorb on the air/water interface. While this phenomena has been extensively studied both theoretically and experimentally, understanding the contribution of anion polarizability to the free energy of adsorption has proven surprisingly challenging: anion polarization cannot rationalize known trends in anion adsorption some simulation approaches and interface active anions appear not to be polarized in others. One possible explanation for this state of the affairs is that, in the absence of experimental constraints on interfacial anion polarizability to parameterize classical descriptions or validate interfacial anion polarization calculated from ab-initio simulations, theoretical description of interfacial polarizability is beset by systematic error.
Yujin has just submitted a paper showing that the symmetry of the polarizability tensor of perchlorate, a known interface-active anion, changes by more than 2x in moving from bulk liquid to the air/water interface and that this change is concentration dependent: as the interfacial population of perchlorate increases the polarizability tensor grows still more anisotropic. This work is the first experimental observation of an anion’s interfacial polarizability and the effect that it describes not explicitly parameterized or shown to occur in any theoretical approach. It thus seems likely that reproducing it in simulation is a useful step in trying to resolve the role of polarizability in anion adsorption at the air/water interface (for the preprint see the arXiv).
After a highly successful summer stint in Berlin Nick Pant has returned to McGill. By dint of dogged determination and a knack for finding some (superficially unrelated) prior work he managed to help us get control of the electrodeposition of various FeOx films on several substrates. We (and particularly Julius) are very grateful.
Short answer, yes. If you’re still not convinced see Yujin’s invited reference module, In-Situ Probing of Adsorbates at Electrochemical Interfaces with Vibrational Sum Frequency Spectroscopy, just accepted for publication in the Enclyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry ( e-mail for preprint).
Tobias and Yujin’s paper trying to answer this question for a SAM formed of spiropyrans has been accepted for publication in Journal of Physics: Condensed Matter. In it they show that if you’d like to build an electrochemical sensor using an electrode covered with a photoswitchable SAM (and, well, of course you’d like to) you need to quantitatively account for the influence of the surface potential on the composition of the photostationary states. For those who need more, the abstract:
Surfaces whose macroscopic properties can be switched by light are potentially useful in a wide variety of applications. One such promising application is electrochemical sensors that can be gated by optically switching the electrode on or off. One way to make such a switchable electrode is by depositing a self-assembled monolayer of bistable, optically switchable molecules onto an electrode surface. Quantitative application of any such sensor requires understanding how changes in interfacial field affect the composition of photostationary states, i.e. how does electrode potential aect the extent to which the electrode is on or off when irradiated, and the structure of the SAM. Here we address these questions for a SAM of a 6-nitro-substituted spiro[2H- 1-benzopyran-2,2′-indoline] covalently attached through a dithiolane linker to an Au electrode immersed in a 0.1 M solution of Tetramethylammonium hexauorophosphate in Acetonitrile using interface-specic vibrational spectroscopy. We find that in the absence of irradiation, when the SAM is dominated by the closed spiropyran form, variations in potential of 1 V have little effect on spiropyran relative stability. In contrast, under UV irradiation small changes in potential can have dramatic eects: changes in potential of 0.2 V can completely destabilize the open, merocyanine form of the SAM relative to the spiropyran and dramatically change the chromophore orientation. Quantitatively accounting for these eects is necessary to employ this, or any other optically switchable bistable chromophore, in electrochemical applications.
In an attempt to further evangelize our efforts in femtosecond time resolved electrochemistry, Kramer gave an invited talk at the Ninth International Conference on Advanced Vibrational Spectroscopy (ICAVS9) in Victoria, Canada titled Towards Experimentally Probing the Hydrogen Evolution Reaction on Pt and Au with Femtosecond Time Resolution.
Nick Pant (undergraduate student from McGill University) has arrived to do a summer internship with us (under Julius’ wing) to work on electrochemical characterization of Fe-oxides. His stay is supported through the DAAD Rise Germany program.
In a continued attempt to tell as many people as possible about our ongoing activities Yujin went on a China tour giving talks at the Harbin Institute of Technology to chemical engineers on May 15th (Application of Vibrational Sum Frequency Spectroscopy to Study Various Surfaces and Interfaces) and at the State Key Laboratory of Physical Chemistry of Solid Surfaces Xiamen University, on May 18th (Probing Electrochemical Interfaces with Vibrational Sum Frequency Spectroscopy). In pursuit of the same goal Kramer went to Kaiserslautern, because it’s closer, for this year’s Bunsentagung where he gave a talk on May 26th titled Towards a Femtosecond Resolved View of the Mechanism of the Hydrogen Evolution Reaction on Au.
In this year’s spring meeting of the Condensed Matter Section of the DPG (Dresden, March 19-24) Yujin entertained the assembled multitudes with his view of the electrochemical oxidation of gold and out theory collaborator Sergery Levchenko told the world about our view of why CH2 is stabilized at steps on the basal plane of Ruthenium. If you’re interested in gold oxidation stay tuned but if you’d like to know more about CH2 stabilization, well, you’re in luck. Harald’s paper on this very subject is available in Journal of Physical Chemistry C (or by e-mailing us for a reprint).