From Biomineralization to Bio-Inspired Routes for Controlling the Structure and Properties of Materials: Reusing Proven Tricks on New Materials
Boaz Pokroy
In the course of biomineralization, organisms produce a large variety of functional biogenic crystals that exhibit fascinating mechanical, optical, magnetic and other characteristics. More specifically, when living organisms grow crystals they can effectively control polymorph selection as well as the crystal morphology, shape, and even atomic structure. Materials existing in nature have extraordinary and specific functions, yet the materials employed in nature are quite different from those engineers would select.
I will show how we have emulated specific strategies used by organisms in forming structural biogenic crystals, and have applied these strategies biomimetically so as to form new structural nanomaterials with new properties and characteristics. This bio-inspired approach involves the adoption of three specific biological strategies:
(i) control the short-range order of nanoamorphous materials.
(ii) control the morphology of single crystals of various functional materials so that they can have intricate and curved surfaces and yet maintain their single-crystal nature.
(iii) entrap organic molecules into single crystals of functional materials so as to tailor and manipulate their electronic structure.
Mutually Reinforced Polymer-Graphene Bilayer Membrane for Energy-Efficient Acoustic Transduction
Doron Naveh
Graphene holds promise for thin, ultralightweight, and high-performance nanoelectromechanical transducers. However, graphene-only devices are limited in size due to fatigue and fracture of suspended graphene membranes. Here, a lightweight, flexible, transparent, and conductive bilayer composite of polyetherimide and single-layer graphene is prepared and suspended on the centimeter scale with an unprecedentedly high aspect-ratio of 105. The coupling of the two components leads to mutual reinforcement and creates an ultra-strong membrane that supports 30 000 times its own weight. Upon electromechanical actuation, the membrane pushes a massive amount of air and generates high-quality acoustic sound. The energy efficiency is ≈10–100 times better than state-of-the-art electrodynamic speakers. The bilayer membrane’s combined properties of electrical conductivity, mechanical strength, optical transparency, thermal stability, and chemical resistance will promote applications in electronics, mechanics, and optics.
Kinetics and Mechanism of Guided Nanowire Growth
Ernesto Joselevich
The large-scale assembly of NWs with controlled orientation on surfaces remains one challenge toward their integration into practical devices. During the last decade, we have reported the growth of perfectly aligned, millimeter-long, horizontal NWs of GaN [1], ZnO [2], ZnSe [3], ZnTe [4], CdSe [5], CdS [6], CsPbBr3 [7] and other materials, with controlled crystallographic orientations on different planes of sapphire [1-7], SiC [8], quartz [9], and spinel [10]. The growth directions and crystallographic orientation of the NWs are controlled by their epitaxial relationship with the substrate, as well as by a graphoepitaxial effect that guides their growth along surface steps and grooves. We demonstrated the massively parallel “self-integration” of NWs into circuits via guided growth [11] and the production of optoelectronic nanosystems, including photodetectors, photodiodes and photovoltaic cells [12]. Here, I will briefly present and overview of the topic, and the focus on our systematic studies aimed at understanding the mechanism of guided nanowire growth based on both in situ and ex situ kinetic studies [13].
References
[3] Adv. Mater. 2015, 27, 3999.
[4] J. Phys. Chem. C, 2016, 120, 18087.
[6] J. Am. Chem. Soc., 2017, 139, 15958.
[7] Nano Lett., 2018, 18, 424.
[8] Nano Lett. 2013, 13, 5491.
[10] J. Phys. Chem. C 2014, 118, 19158.
[12] ACS Nano 2017, 11, 6155.
[13] PNAS 2020, 117, 152.
Handedness Control and Spontaneous Symmetry Breaking in The Formation of Chiral Nanocrystals
Gil Markovich
We have recently been studying the handedness controlled synthesis of inorganic nanocrystals made of materials which crystallize in chiral space-groups, such as a-HgS, Te, Se. Here I will describe the strong chiral amplification in the colloidal synthesis of intrinsically chiral terbium phosphate nanocrystals, quantitatively measured via the circularly polarized luminescence of europium dopant ions within the nanocrystals. We obtained 100% enantiomeric purity of the nanocrystals by using chiral tartaric acid molecules in the synthesis which act as an external “chiral field”, sensitively directing the amplified nanocrystal handedness through a discontinuous transition between left- and right-handed excess. The amplification involves also spontaneous symmetry breaking into either left- or right-handed nanocrystals below a critical temperature, in the absence of the tartaric acid molecules. These characteristics suggest a conceptual framework for chiral amplification, based on the statistical thermodynamics of critical phenomena, which we use to quantitatively account for the observations. Our results demonstrate how chiral minerals with high enantiomeric excess could have grown locally in a primordial racemic aqueous environment.
Semiconductor Nanocrystal Optoelectronics of Colloidal Quantum Wells
Hilmi Volkan Demir
In this talk, we will introduce the emerging field of semiconductor nanocrystal optoelectronics with most recent examples of their optoelectronic devices and photonic structures made of atomically-flat tightly-confined nanocrystals, the quasi-2D colloidal quantum wells (CQWs), also popularly nick-named ‘nanoplatelets’. Among various extraordinary features of theirs, we will show that these CQWs enable record high optical gain coefficients [1] and can achieve optical gain thresholds at the level of sub-single exciton population per CQW on the average [2]. Next, we will present a new tool for controlled stacking and oriented self-assemblies of these nanoplatelets, which provides us with a powerful ability to tune and master their excitonic properties as well as the level of achievable energy transfer [3]. Using three-dimensional constructs of such face-down oriented slabs of CQWs with monolayer precision, we will demonstrate ultra-thin optical gain medium and lasers of these CQW assemblies [4]. Finally, we will show record high-efficiency colloidal LEDs using CQWs employed as the electrically-driven active emitter layer [5]. Given their current accelerating progress, these solution-processed quantum materials hold great promise to challenge their epitaxial thin-film counterparts in semiconductor optoelectronics in the near future.
[1] Guzelturk et al., HVD, Nano Letters 19, 277 (2019)
[2] Taghipour et al., HVD, Nature Comm 11, 3305 (2020)
[3] Erdem et al., HVD, Nano Letters 19, 4297 (2019)
[4] Erdem et al., HVD, Nano Letters 20, 6459 (2020)
[5] Liu et al., HVD, Advanced Materials 32, 1905824 (2020)
Combining DFT and Experiments to Study Perovskite Crystals
Hasan Şahin
It will be in the form of a short summary of the theoretical and experimental studies performed in my presentation group. In particular, I will give information about the results we have obtained on perovskite crystals and how the Density Functional Theory is used to illuminate them. Stability, dopant and charging dependent properties and magnetism of cesium lead halide type perovskites will be included in my talk.
A Place Where Everyone Matters – Interfaces in Functional Nanostructures
Maya Bar-Sadan
Although nanostructures contain tenths of thousands of atoms, the atoms at the interfaces make most of the impact on the functionality, especially regarding the catalytic activity. It is therefore an important mission to control the formation of interfaces at the atomic scale, but that is easier said than done. First, it is hard to characterize and understand what was obtained in the synthesis. Then, relating the specific structures to the macroscopic properties requires overcoming issues of adequate sampling and statistics, reproducibility to the atomic scale features and abundance of similar structures within a synthetic batch. Last, there are confusing cases where we synthesize a certain structure to best of our knowledge and spontaneous rearrangements produce other active particles. Here, I will present a few such cases.
Dual Nano-Patterns Obtained by Directed Self-Assembly of Ultra-confined Block Copolymer Films
Roy Shenhar
Directed self-assembly of block copolymers facilitates the creation of films with highly oriented domains over large areas. However, further enhancing our control over surface design requires the ability to create regions of a desired pattern which could be arbitrarily spaced.
We have recently discovered that the utilization of substrates with topographically-defined stripes leads to the formation of different morphologies in the trenches and on the plateaus in ultra-confined block copolymer films. This is explained by the fact that capillary action drives more material to deposit in the trenches than on the plateaus during spin coating. The high sensitivity of the patterns displayed by ultra-confined films to minute differences in film thickness and substrate selectivity gives rise to different patterns in the trenches and on the plateaus. Specifically, we were able to demonstrate the formation of hexagonally packed dots on the plateaus concomitant with featureless appearance of the slightly thicker films in the trenches, owing to the ability of the latter to accommodate lying lamellae. As the widths of the trenches are controlled by the lithographic design, this situation facilitates the creation of patterned domains that are spaced by featureless regions as needed.
High throughput Computational Screening of Porous Materials for Energy Applications
Seda Keskin Avcı
We have witnessed the quick growth of a new generation nanoporous materials named as metal organic frameworks (MOFs) in the last decade. MOFs have exceptional physical, chemical, and structural properties which make them promising for a large variety of applications, mainly for CO2 separation. The number of MOFs has been increasing very rapidly and experimental identification of materials exhibiting high separation potential is simply impractical. High-throughput computational screening studies in which several thousands of MOFs are evaluated to identify the best candidates for a target separation is crucial in directing experimental efforts to the most useful materials. In my talk, I will show how molecular simulations were used to screen the entire MOF database (~55,000 MOFs) to identify the best materials for CO2 separation from flue gas (CO2/N2) and landfill gas (CO2/CH4) in addition to CO2/H2 and CH4/H2 separations. The top performing MOFs for each gas separation were identified based on the combination of these metrics. I will also discuss the relations between structural properties of MOFs and their performances to provide structure-property relationships that can serve as a map for experimental synthesis of new MOFs with better performances. These results will accelerate the design and development of novel materials for efficient CO2 capture and separation.
Towars Bridging the Gap Between Homogeneous and Heterogeneous Catalysis Through Supramolecular Chemistry
Görkem Günbaş
Catalysts are crucial components for making and breaking of chemical bonds in an effective and selective manner, which is crucial for converting basic chemicals into useful products for society. Traditionally, catalysis is divided into homogeneous catalysis and heterogeneous catalysis. Catalytic system that can combine advantages of both homogenous and heterogeneous catalysis remains to be one of the most significant challenge in the area. We envisioned that using a supramolecular chemistry to build a catalytic system in a bottom-up fashion could be the key approach to overcome this challenge. With this motivation; we set our goal to realize a catalyst where a metal with a defined ligand sphere is attached to a logically designed small molecule, which can then assemble into a well-defined heterogeneous catalysts. Here we will discuss results on supramolecular systems developed in our group and our efforts towards their
utilization in “synthesis” of novel catalytic systems.
Kelvin Probe Force Microscopy under Electrochemical Reaction Conditions: The Graphene Membrane Approach
Baran Eren
Much of our existing fundamental understanding of the surfaces involved in heterogeneous catalysis (both thermal or electrochemical) relies on studies of model single crystals using surface-sensitive techniques that typically require rarefied ultra-high vacuum conditions. However, to truly understand how catalysts operate requires working with more complex materials such as nanoparticles and at much higher gas pressures (or inside liquids), respectively referred to as the ‘material gap’ and the ‘pressure gap’. In this talk, I am going to introduce a novel approach to tackle this challenge by using specially designed micro-reactor that enables performing surface-sensitive experiments in the presence of liquids, under electrochemical reaction conditions, to reveal the chemical state of NPs. The reactor involves the use of graphene membranes and Kelvin probe force microscopy (KPFM) measurements, to detect the changes on the work function of the nanoparticles under electrocatalytic reaction conditions. Prototype study of oxidation and reduction of Cu nanoparticles, and thereby the changes in work function measured through graphene, will be presented. Future directions with this novel approach will also be discussed.
Nanocrystals for Efficient Electroluminescent Devices
Evren Mutlugün
Semiconductor quantum dots are promising materials for lighting and display technologies for their superiour color conversion properties, high absorption coefficient and stabilities. In general, quantum dots based on II-VI and III-V materials can be excited by optical or electrical pumping and provide high efficiency light generation. Thanks to the quantum confinement, quantum dots posess spectrally pure emission and replace the conventional phosphor materials especially for display technologies. They have started to emerge in the display market, providing novel solutions for LCD backlighting to generate superiour white light and thus gain commercial importance.
Not only for optical pumping, but also for the electrical pumping, quantum dots can generate the formation of excitons which can be utilized for the display technologies. In this respect, new generation high performance quantum dot LEDs that can provide superiour light purity, stability, and brightness will be on focus of technology in the coming years.
This talk will emphasize on our recent work on the development of electroluminescent devices based on these colloidal nanocrystals.
Nanophotonics: Enabling Technology for Next-Generation Biosensors
Hatice Altuğ
Emerging healthcare needs with global health crisis, precision medicine and point-of-care diagnostics are demanding breakthrough developments in biosensing and bioanalytical tools. Current biosensors are lacking precision, bulky, and costly, as well as they require long detection times, sophisticated infrastructure and trained personnel, which limit their applications. My laboratory is focused on to address these challenges by exploiting novel optical phenomena at nanoscale and engineering toolkits such as nanophotonics, nanofabrication, microfluidics and data science. In particular, we use photonic nanostructures based on plasmonic and dielectric metasurfaces that can confine light below the fundamental diffraction limit and generate strong electromagnetic fields in nanometric volumes. In this talk I will present how we exploit nanophotonics and combine it with imaging, biology, chemistry and data science techniques to achieve high performance biosensors. I will introduce ultra-sensitive Mid-IR biosensors based on surface enhanced infrared spectroscopy for chemical specific detection of molecules, large-area chemical imaging and real-time monitoring of protein conformations in aqueous environment. Next, I will describe our effort to develop ultra-compact, portable, rapid and low-cost microarrays and their use for early disease diagnostics in real-world settings. Finally, I will highlight label-free optofluidic biosensors that can perform one-of-a-kind measurements on live cells down to the single cell level, and provide their overall prospects in biomedical and clinical applications.
Laser based printing: From Liquids to Microstructures
Hagay Shpaisman
Assembly of materials into microstructures under laser guidance is attracting wide attention. The ability to pattern various materials and to form 2D and 3D structures with micron/sub-micron resolution and less energy and material waste compared with standard top-down methods make laser-based printing promising for many applications in sensing, medical devices and microelectronics. Assembly from liquids provides smaller feature size than powders and has advantages over other states of matter in terms of the relatively simple setup, easy handling, and recycling. However, the simplicity of the setup conceals a variety of underlying mechanisms, which cannot be identified simply according to the starting or resulting materials.
Here, we shed light on one of the mechanisms through systematic analysis of photo-thermal reaction products forming iron oxide and silver at different interfaces. Examination of the nanostructure of deposits on a substrate using high-resolution transmission electron microscopy and selected area diffraction pattern analysis reveals a combination of both amorphous and crystalline moieties. We found that focusing the laser inside the solution leads to exclusive formation of crystalline products, while focusing at the liquid/air interface leads to formation of amorphous products due to kinetic considerations. Ring-shaped microstructures observed on the substrate indicate that microbubbles are involved in the deposition. Our findings suggest that crystalline nanoparticles formed in solution are pinned to the base of the microbubbles. These stationary deposits absorb the laser light, resulting in extensive local heating, which leads to a fast thermal-reaction of the metal ions that are added as amorphous nanostructures. The presence of both crystalline and amorphous nanostructures therefore results from two different mechanisms.
Selected relevant publications:
1. Armon, N., Greenberg, E., Layani, M., Rosen, Y. S., Magdassi, S. & Shpaisman, H. Continuous Nanoparticle Assembly by a Modulated Photo-Induced Microbubble for Fabrication of Micrometric Conductive Patterns. ACS Appl. Mater. Interfaces 9, 44214–44221 (2017).
2. Greenberg, E., Armon, N., Kapon, O., Ben‐Ishai, M. & Shpaisman, H. Nanostructure and Mechanism of Metal Deposition by a Laser‐Induced Photothermal Reaction. Adv. Mater. Interfaces 1900541 (2019). doi:10.1002/admi.201900541
3. Armon, N., Greenberg, E., Edri, E., Kenigsberg, A., Piperno, S., Kapon, O., Fleker, O., Perelshtein, I., Cohen-Taguri, G., Hod, I. & Shpaisman, H. Simultaneous laser-induced synthesis and micro-patterning of a metal organic framework. Chem. Commun. 55, 12773–12776 (2019).
Atomically Thin Semiconductors: Synthesis and Applications
Ariel Ismach
The ability to synthesize large-area and high quality atomic films is a prerequisite for their successful integration into a wide variety of novel and existing technologies. Here we show the growth of transition metal dichalcogenides (TMDs) via modified chemical vapor deposition (CVD) methods using volatile precursors. The use of high vapor pressure precursors allows for the controlled delivery to the growth sample, and therefore, suitable for homogeneous and large-scale synthesis, as required for many applications. However, one of the problems with these precursors is the small domain size usually obtained. In order to address these issues, two different concepts were implemented and will be described: i. Seeded-growth and, ii. Pulsed-growth approaches. In the first, and following the success in the seeded-growth of nanoparticles, nanowires, films and 3D crystals, the growth of 2D materials is demonstrated. The description of the methodology as well as the influence of the seed-material on the grown layered domains will be described. In the second, a modified approach in which the metal and chalcogen precursors are delivered in a pulsed fashion is demonstrated. This approach allows to achieve a significant increase in the domain size, from ~10 nm (or below) to ~10s of microns. Another advantage of using volatile precursors is the ability to control the lateral and vertical heterostructures formation, and will be described as well. Following this work and in order to expand our growth capabilities, the growth of monochalcogenides using lessons learned while growing TMDs will be briefly described. I will finalize by describing some of the potential applications addressed in our lab.
Insights from Molecular Simulations for Molecular Self-Assembly
Aykut Erbaş
Self-assembly of low-molecular-weight amphiphilic molecules provides a unique and powerful toolbox to design functional biomimetic materials. Yet, even small variations in weak intermolecular interactions or assembly conditions can tremendously alter topology, isotropy, and space-dimensions of the final structures. Based on our recent research with Stupp Lab, I will talk about two such examples; self-assembly of amphiphilic peptide into vesicles and high-aspect ratio nanofibers, and molecular self-assembly guided by hydrogel-scaffolds. Via these two examples, I discuss several generic mechanisms to direct and control the self-assembly of amphiphilic molecules into prescribed structures.
Ultrafast Laser-Driven Self-Organized Nano-And Micro-Structuring
F. Omer Ilday
Towards Designing Material Properties in Polypeptide Nanofibrils With H-Bonds.
Ulyana Shimovich
The process of protein self-assembly into a fibrillar structure generates the strongest biomaterials in the world, like silk fibers, but unfortunately, it is also associated with the development of neurodegenerative diseases. Although the universality of the fibril structure’s reliance on hydrogen bonds (H-bonds) is well documented, our understanding of the mechanism and fundamental principles of H-bond formation in fibrils and their link to the fibril’s exceptional material properties as well as their association with disease is still very limited. We provide spectroscopic evidence implicating perturbations in the H-bonded pattern of fibrillating amyloid peptide models and in the consequent changes to the mechanical properties of fibrillar materials. We show that, contrary to widespread expectations, steric hindrance, achieved via aliphatic-to-aromatic amino acid substitution, does not affect the natural propensity of the peptides to form amyloidogenic types of fibrils. These perturbations, however, trigger changes in H-bonded networks and conformational changes that alter key molecular events in the fibrillation process and lead to variations in the fibril morphology, structural composition, and mechanical properties. The accumulated knowledge provides a general framework for better understanding the role of H-bonds in functional and disease-associated fibrillar self-assembly and for unraveling the missing link between H-bonds’ characteristics, protein packing in fibrillar constructs, and the resulting material properties of protein nanofibrils.
Universality of Dissipative Self-Assembly From Quantum Qots to Human Cells.
Serim Ilday
Self-assembly research has started with a question: Can we design and build planned structures and functionalities, starting from simple building blocks? A vast body of work points to the possibility of this approach. However, the demonstrations so far suffer from being extremely specific solutions. Change, e.g., the material or the experimental conditions slightly and to repeat the same achievement, takes months/years. The question is: Can self-assembly methodologies transcend the specificity of the systems that are being studied? In this talk, I will argue that fundamental principles of universal self-assembly lie in the intrinsic physical mechanisms, namely, nonlinearity, fluctuations, and feedback that drive and control self-assembly processes. I will showcase this approach on a diverse spectrum of materials starting from simple, passive, identical quantum dots up to complex, active, non-identical human cells with sophisticated internal dynamics. Then, I will demonstrate the effectiveness of this approach, using completely different experimental settings and materials.
Elucidating the Role of Boron in Persistent Luminescence in Strontium Aluminate Phosphors by Atomic Resolution Imaging
Cleva Ow-Yang
For safety and productivity, we consume 15 percent of global electricity for lighting and generate 5 percent of worldwide greenhouse gas emissions. Imagine if we could consume no electrical power when lighting our workspaces and living environments. This goal is what motivates us to develop long afterglow powders. We believe the key is to understand the relationship between the atomic arrangements in ceramic phosphors that enable extending the duration of afterglow. Although it has been known for > 20 years that the addition of boron oxide during synthesis dramatically extends the afterglow from 10 minutes to > 10 hours in strontium aluminate co-doped by divalent Eu and trivalent Dy (SAED), the pivotal role of boron is still not well understood. In this talk, I will discuss the latest developments in our understanding of the mechanism by which boron extends the persistent luminescence in SAED. We show that boron incorporates into the ceramic powders, and its presence induces the incorporation of Eu and Dy ions into adjacent sites in the Sr sub-lattice. We show also that boron in the amorphous intergranular phase tunes the concentration of Eu and Dy in the crystals supporting the persistent luminescence. We present an evolving model consistent with observations from atomic resolution imaging and spectroscopy in a spherical aberration-corrected scanning transmission electron microscope, nano-cathodoluminescence, micro-Raman, and other spatially resolved structural and chemical analyses.