Integrated Calendar

Metal halide perovskites (MHPs) have re-emerged as exceptional semiconductor materials for photovoltaics and optoelectronics, gaining tremendous attention in the fields of materials and energy harvesting over the past decade. Their unique properties, alongside their relatively cheap and easy production, make them excellent candidates as materials for the next-generation optoelectronic technologies. Besides their technological advantage, their soft ionic lattice and anharmonic potential, that are part of the underlying reasons for their unusual and outstanding performance, challenge the well-established models of classical semiconductor physics and provoke many scientific research opportunities and questions. In order to intrinsically study these outstanding behaviors, a simple system is requires, diminishing complexities that can arise when examining the popularly studied polycrystalline thin films that contain multiple defects, mainly grain boundaries. Over the past decade, our group has been developing and mastering the surface-guided growth of horizontal semiconductor NWs, which can be employed to grow arrays of epitaxial single crystal MHP NWs. These NWs offer a unique opportunity as a simple model-system for investigating the intrinsic properties of MHPs, due to their single crystal nature and quasi one-dimensional structure. These are especially suitable for the investigation of how lattice strain affects the materials’ properties, considering their inherent heteroepitaxial strain.
The aim of this PhD work was to gain insight on the growth of surface-guided CsPbBr3 NWs, as a representative of the MHP family, and study the effect of epitaxial strain on their structure and properties. To achieve this goal, we first developed the crystal growth of the surface-guided CsPbBr3 NWs on sapphire, by a few different vapor-phase methods. We inspected their growth in situ using simple optical microscopy to try to learn how these unique materials grow. These were followed by integration of the NWs into nanodevices in order to examine their optoelectronic properties, with a special emphasis on the influence of strain on their performance. We finally exemplified a high-throughput study using an automated optical system that can probe many NWs in a short amount of time, to develop a charge-carrier behavior model based on a large amount of data. Studying the epitaxially strained surface-guided CsPbBr3 NWs provides important insight into the crystal growth and optoelectronic properties of MHPs

A critical factor determining the biological activities of sphingolipids (SLs) is their N-acyl chain length, which in mammals is determined by a family of six ceramide synthases (CerS). Using site-directed mutagenesis and biochemical analyses, we have found a short sequence in a loop located between the last two putative transmembrane domains (TMDs) of the CerS, determines their acyl-CoA specificity. The specificity of a chimeric protein based on the backbone of CerS5 (which generates C16-ceramide), but containing 11 residues from CerS2 (which generates C22–C24-ceramides), allowed the enzyme to generated C22– C24 and other ceramides. Moreover, a similar chimeric protein based on the backbone of CerS4 (which normally generates C18–C22 ceramides) displayed significant activity toward C24:1-CoA.

Our organs exhibit complex and precise shapes which emerge during embryonic development. While biology has focused on a genetic study of organ formation, we have a limited understanding of the mesoscale mechanical forces which shape organs. A central question is how the physical form of an organ self-organizes from the collective activity of its constituents - thousands of fluctuating microscopic biological cells. Establishing a physical framework for understanding organ shape across scales requires a tight interplay between experiment and theory. However, organ development occurs within the embryo, an extraordinarily complex and coupled system with limited experimental access. To address this challenge, we developed a minimal quantitative system to study the dynamics of organ shape formation in a dish. By combining materials science with stem-cell research tools, we recreated the formation of the human neural tube - the first milestone in brain development. Experiments and vertex-model simulations reveal that a wetting transition can explain the complex dynamics of neural tube formation. Our approach paves the way for a predictive understanding of human organ formation in health and disease.

When Hanbury-Brown and Twiss proposed to use photon correlations for stellar interferometry in 1954 the idea was received with great skepticism. Yet, the use of photon correlations for various uses, from identification of quantum emitters to emitter counting grew over the years. In the talk, I will describe some of our efforts in using HBT correlations and their derivatives in superresolution microscopy and in advanced spectroscopy of quantum emitters, as well as the technological advances enabling this.