ERC FUNDED PROJECTS

Coupling of atoms is the basis of chemistry, yielding the beauty and richness of molecules and materials. Herein I introduce nanocrystal chemistry: the use of semiconductor nanocrystals (NCs) as artificial atoms to form NC molecules that are chemically, structurally and physically coupled. The unique emergent quantum mechanical consequences of the NCs coupling will be studied and tailored to yield a chemical-quantum palette: coherent coupling of NC exciton states; dual color single photon emitters functional also as photo-switchable chromophores in super-resolution fluorescence microscopy; electrically switchable single NC photon emitters for utilization as taggants for neuronal activity and as chromophores in displays; new NC structures for lasing; and coupled quasi-1D NC chains manifesting mini-band formation, and tailored for a quantum-cascade effect for IR photon emission. A novel methodology of controlled oriented attachment of NC building blocks (in particular of core/shell NCs) will be presented to realize the coupled NCs molecules. For this a new type of Janus NC building block will be developed, and used as an element in a Lego-type construction of double quantum dots (dimers), heterodimers coupling two different types of NCs, and more complex NC coupled quantum structures. To realize this NC chemistry approach, surface control is essential, which will be achieved via investigation of the chemical and dynamical properties of the NCs surface ligands layer. As outcome I can expect to decipher NCs surface chemistry and dynamics, including its size dependence, and to introduce Janus NCs with chemically distinct and selectively modified surface faces. From this I will develop a new step-wise approach for synthesis of coupled NCs molecules and reveal the consequences of quantum coupling in them. This will inspire theoretical and further experimental work and will set the stage for the development of the diverse potential applications of coupled NC molecules.

2 499 750 €

Start date: 2017-11-01, End date: 2022-10-31

This proposal is aimed at developing and applying novel ultra-sensitive methods for studying the structure and dynamics of surfaces on an atomic scale, focusing on water surfaces in particular. The proposal consists of two main instrument development projects which are based on magnetic manipulation of molecular beams: (1) Developing a ground-breaking apparatus which uses a pre-polarized H2O molecular beam in order to perform NMR measurements on dilute surface science systems, measurements which were impossible using conventional NMR approaches. (2) Developing a unique second-generation helium spin echo spectrometer which is sensitive to motion on an unprecedentedly wide time scale range. This instrument will be capable of measuring atomic scale surface dynamics of systems which were previously beyond the realm of experimentalists. Both of these novel instruments will be primarily used to study the atomic scale structure and dynamics of water surfaces. Studying these systems is particularly challenging due to the delicate and complex nature of the surface, nevertheless, there is an extensive interest in studying water surfaces due to the key role they play in a wide range of research fields and applications. Examples include atmospheric chemistry, where ozone depleting reactions are catalyzed on ice surfaces, Material sciences and nano-technology, where the interaction and reactivity of a surface with water can determine the performance of novel miniature devices and even astrophysics where star birth reactions take place on ice surfaces. We intend to exploit the new contrast mechanisms and the unique time scales made available by the novel instruments we will develop, in order to obtain new experimental insights into this exciting research field.

1 850 000 €

Start date: 2012-10-01, End date: 2017-09-30

Critical for the function of many proteins, allosteric communication involves transmission of the effect of binding at one site of a protein to another through conformational changes. Yet the structural and dynamic basis for allostery remains poorly understood. In particular, there is no method to follow coordinated large-scale motions of domains and subunits in proteins as they occur. Since the subunits of allosteric proteins often contain multiple domains, any such method entails probing the dynamics along several intra-protein distances simultaneously. This proposal aims at ameliorating this deficiency by creating the experimental framework for exploring time-dependent coordination of allosteric transitions of multiple units within proteins. Our methodology will rely on single-molecule FRET spectroscopy with multiple labels on the same protein and advanced analysis. We will explore fundamental issues in protein dynamics: relative motions of domains within subunits, propagation of conformational change between subunits, and synchronization of these motions by effector molecules. To investigate these issues, we have carefully selected three model systems, each representing an important scenario of allosteric regulation. While the homo-oligomeric protein-folder GroEL conserves symmetry in a concerted transition between major structural states, the symmetry of the homo-oligomeric disaggregating machine ClpB is broken via a sequential transition. Symmetry is attained only after binding to DNA and ligands in the third system, the family of RXR heterodimers. This exciting project will provide the very first catalogue of coordinated and time-ordered motions within and between subunits of allosteric proteins and the first measurement of the time scale of the conformational spread through a large protein. It will enhance dramatically our understanding of how allostery contributes to protein function, influencing future efforts to design drugs for allosteric proteins.

2 484 722 €

Start date: 2017-05-01, End date: 2022-04-30

"This research is aimed at developing and validating a novel approach for time resolved imaging of structural dynamics, using single photon Coulomb explosion imaging (CEI) with ultrafast extreme UV (EUV) pulses to probe laser initiated ultrafast structural rearrangement and fragmentation dynamics. The emerging field of ultrafast EUV pulses attracts increasing amount of scientific attention, predominantly concentrated on understanding aspects of the generation process, as well as on measuring record breaking attosecond pulses at increasingly high photon energies and photon flux. I propose to direct the unique properties of ultrafast EUV pulses towards time resolved studies of molecular reaction dynamics that are inaccessible with conventional ultrafast laser systems. Time resolved single photon CEI will make possible the visualization of complex dynamics in polyatomic systems; specifically, how laser driven electronic excitation couples into nuclear motion in a wide range of molecular systems. In contrast to earlier attempts, in which CEI was driven with intense near-IR pulses that can alter the observed dynamics, the proposed single photon CEI will remove the masking intense field effects and provide a simple and general probe. A comprehensive experimental effort is proposed - to conduct a direct comparison of intense field CEI to the proposed single EUV photon approach. Successful implementation of this research will endow us with a new way to visualize and understand the underlying quantum mechanisms involved in chemical reactions. With this new technology I hope to be able to provide unique insight into molecular fragmentation and rearrangement dynamics during chemical reactions and to resolve long standing basic scientific questions, such as the concerted or sequential nature of double proton transfer in DNA base-pair models. Finally, the ""table top"" techniques developed in my lab will mature and become applicable to the emerging ultrafast EUV user facilities."

1 499 000 €

Start date: 2012-11-01, End date: 2018-10-31