Nanotechnology has made incredible progress over the past decade opening up totally new realms of science, especially at the intersection between disciplines. The new understanding that has been developed as well as exciting new material systems is now being applied to many important societal issues. Of special importance are issues of sustainability including energy production and control of global warming issues. Featuring invited lectures by leading scientists in the field from both Italy and the United States, the conference will present recent research in Nanotechnology, Materials, and Energy that has characterized scientific research in both countries, with special emphasis on collaborative and joint research efforts. Lectures will focus on topics such as Novel nanoscale materials including graphene and other single layer materials including boron nitride and molybdenum sulfide, organic films, nanotubes and other functional materials as well as many energy-related applications based on these concepts.
This conference is hosted by the Italian Academy for Advanced Studies in America at Columbia University
Location: The Italian Academy | 1161 Amsterdam Ave (just south of 118th St) | New York, NY.
Molding Optical Wavefronts: Flat Optics based on Metasurfaces
Metasurfaces based on sub-wavelength patterning have major potential for realizing arbitrary control of the wavefront of the diffracted light by achieving local control of the phase amplitude and polarization. We discuss novel devices based on this technique; a salient feature is the ability to create an arbitrary analog phase profile (often with a single digital mask). A variety of flat optical components, including lenses, polarizers, vortex plates, coatings, holograms and couplers with polarization invariant coupling efficiency will be presented.
Tuning metal-support interactions in ceria based catalysts
Heterogeneous catalysts that are used in a wide variety of industrial and environmental applications already take advantage of the synergy between a support and the supported phases. Some oxides, such as the reducible ceria, can participate in the catalytic cycle by providing reactive oxygen through formation of vacancies.
This paper will present some recent developments in understanding the role of metal-support interaction by means of investigating model heterogeneous catalysts based on supported metal crystals on ceria and on the design of active metal core-oxide shell catalysts. These studies were carried out in the framework of a joint collaboration with the research groups of Professor Raymond Gorte and of Professor Christopher Murray, both at the University of Pennsylvania.
1. Cargnello, M.; Fornasiero, P.; Gorte, R. J., Catal. Lett., 2012, 142, 1043
2. Cargnello, M.; Delgado Jaén, J.J.; Hernández Garrido, J.C.; Bakhmutsky, K.; Montini, T.; Calvino Gámez, J.J.; Gorte, R.J.; Fornasiero, P., Science 2012, 337, 713
3. Cargnello, M.; Grzelczak, M.; Rodríguez-González, B.; Syrgiannis, Z.; Bakhmutsky, K.; La Parola, V.; Liz-Marzán, L.; Gorte, R. J.; Prato, M.; Fornasiero, P., J. Am. Chem. Soc., 2012, 134, 11760
4. Cargnello, M.; Doan-Nguyen, V.; Gordon, T.R.; Diaz, R.E.; Stach, E.A.; Gorte, R.J.; Fornasiero, P.; Murray C.B., submitted 2013.
Electronic and Optical Properties of MoS2 at Monolayer Thickness
Abstract: MoS2 is a prototype of a family of atomically thin metal dichalcogenides. Although the structure of the monolayer is similar to that of graphene, the A and B sublattice are occupied either by Mo atoms or by a pair of S atoms, rather than by C atoms. This difference in symmetry causes MoS2 to be a semiconductor with a significant band gap. Through characterization of the optical properties of the material as a function of thickness, we show that quantum confinement effects lead to a crossover in MoS2 from a bulk indirect gap semiconductor to a direct gap semiconductor at monolayer thickness . As is common for lower-dimensional materials, excitonic effects are also very strong in MoS2, as we demonstrate through the spectroscopic identification of charged excitons (trions) . Another distinctive feature of this material is the possibility of producing long-lived valley polarization by excitation with circularly polarized light, as we demonstrate through photoluminescence measurements .
 K. F. Mak et al., Phys. Rev. Lett. 105, 136805 (2010).
 K. F. Mak et al., Nature Mater. 12, 207–211 (2013).
 K. F. Mak et al., Nature Nanotech. 7, 494-498 (2012).
Colloidal Inorganic Nanocrystals: from Synthesis, to Assembly, to the Study of their Transformations
Colloidal inorganic nanocrystals are among the most exploited nanomaterials to date, due to their extreme versatility. Research on nanocrystals has advanced rapidly in the past fifteen years. This talk will highlight recent progress by our group in several key areas related to nanocrystals: advanced synthesis, assembly, surface functionalization and the study of chemical and structural transformations in these materials.
Dipartimento di Fisica
Universitá di Trieste
Charge transfer processes in organic nano- and hetero-structures
The performances and efficiency of organic material-based photovoltaic devices are strongly affected by charge transfer processes at interfaces (organic-organic and organic-inorganic). To improve the device performances, these processes and their correlation with the electronic structure of the interfaces must be understood. Spectroscopic studies based on synchrotron radiation experimental techniques of these hetero-structures will be presented, in particular the experiments that probe the charge transfer processes at organic interfaces and provide a time scale for charge dynamics.
Multi-component nanocrystal self-assembly as a route to multi-functional materials and devices: building with artificial atoms
Monodisperse colloidal nanocrystals (NCs) are in a sense "artificial atoms" with tunable electronic, magnetic, and optical properties controlled by tailoring crystal shape, structure and surface passivation. NCs provide ideal building blocks for the assembly of new thin films and devices, and this talk will focus on opportunities to organize the NCs into superlattice films that retain and in many cases enhance the inherent mesoscopic properties of the individual particles. The potential to design new materials and devices expands dramatically with the creation of binary NC superlattices (monolayers and multilayer) BNSLs. I will show how differently sized CdSe, CdTe, PbS, PbSe, CoPt3, Fe2O3, Au, Ag, Pd and NaYF4: Re (Re= rare earths) nanocrystals can be directed to self-assemble into a rich array of multi-functional nanocomposites (metamaterials). Devices based on these new multi-component nanoscale assemblies will be discussed along with some new research directions that focus on emergent physical phenomena in the NC assemblies.
Prospects for Hydrogen Storage in Graphene
Graphene is an intriguing material that shows promise for hydrogen storage. In this talk we will present theoretical and experimental evidence showing how --through changing the curvature of graphene-- the energy barrier for absorbing and desorbing atomic hydrogen attached to the pi-bonds of graphene can be removed, making it possible to attach and release hydrogen at room temperature, a mechanism that can be exploited for room-temperature hydrogen storage applications.
Probing van der Waals Forces at the Single-Molecule Level
Single molecule junctions represent an attractive platform to understand and control functionality of materials and devices at the nanoscale. While their electronic transport properties have received tremendous attention thus far, measurements of mechanics are new and allow for a
more complete understanding of the structure-function relationship at the atomic scale. Here we report simultaneous measurement of force and electrical conductance across single Au-Bipyridine-Au junctions using a conducting atomic force microscope (AFM). We show that van der Waals (vdW) interactions play a key role in the junction mechanics. Our measurements thus enable a quantitative characterization of vdW interactions at metal/organic interfaces in these single-molecule junctions .
 Aradhya, S. V., Frei, M., Hybertsen, M. S. & Venkataraman, L., Nature Materials, 11, 872- 876 (2012).
Materials Synthesis and Processes Development for Flexible Opto-electronic Devices
Printed opto-electronics is a new technology envisioning the fabrication of electronic devices, solar cells, and batteries -- to cite just a few -- using printing methodologies instead of conventional vapor-phase/high-temperature processes employed in the silicon industry. Since organic and hybrid materials can be formulated and printed more efficiently, they will be the key enablers of this technology. In this presentation I will describe the materials and process development enabling the fabrication of unconventional opto-electronic devices, such as displays, circuits, and solar modules, all on flexible foils. I will focus particularly on describing synthetic details of new organic semiconductors and dielectric. Examples of unconventional electronic materials include organic small molecules and polymers, metal chelates and complexes, and hybrid organic-inorganic metal oxides. Along with the process development, I will discuss spin- and slot-dye coating, inkjet printing, and gravure printing.
The exploration of innovative materials and device architectures is constantly fostering our solar conversion research activity, aiming at low-cost and highly efficient solutions.From conceptually new mesostructured solar cells, based on self-assembling hybrid perovskites, to full inorganic bulk heterojunction solar cells based on versatile nanocrystals, we have been exploring viable routes for an effective market impact of third-generation photovoltaics.
Our vision is based on solution-processable materials and low-temperature cell manufacturing, matching the requirements of existing technologies, for large-scale device production at reasonable production costs. Furthermore we are pursuing the implementation of such solar-converting components into multifunctional devices; one example we conceived is a photovoltachromic cell integrating both photovoltaic and photoelectrochromic functionalities, targeting building integration.
Electron Transport in van der Waals Heterostructures
The recent advent of atomically thin two-dimensional materials such as graphene, hexa boronitride, layered transition metal chalcogenide and many strongly correlated materials, has provided a new opportunity to study novel quantum phenomena in low dimensional systems. Combinations of different layered constituents further produce heterogeneous and functional materials. We will discuss how novel electron transport phenomena can occur across the heterointerfaces of designed quantum stacks to realize exotic charge transport phenomena in atomically controlled quantum heterostructures.
Electron and Optical Spectroscopies of Atomically Controlled Graphene Nanoribbons on Au: Insights from Ab-Initio Calculations
Graphene nanostructures have striking properties related to their lateral confinement, that can open a band gap and induce a semiconducting behavior. Key features connected to the tunability of electronic and optical properties as a function of structural parameters, e.g. width and edge structure of graphene nanoribbons (GNR), have been predicted theoretically; however, only recently atomic control of GNR geometry was demonstrated on Au(111) susbtrate. These advancements have allowed the first measurements of the band gap and the topology of the occupied bands by STS and ARPES techniques.
In this work we combine cutting edge theoretical and experimental techniques to study the electronic and optical properties of specific armchair (AGNR) and chevron nanoribbons. Quasiparticle energies and excitonic effects are computed within the so-called GW-BSE scheme for the isolated ribbons; the presence of the substrate is accounted for by means of a classical image charge model for the screened Coulomb interaction.
Our findings show that the metallic substrate induces a significant reduction of the energy gap as compared to the isolated ribbons. For N=7 AGNR (7-AGNR), it brings the GW gap from 3.7±0.1 eV to 2.3-2.7 eV on Au(111). On the contrary, the position of the optical peaks remain unaltered. Our results are in very good agreement with the experimental values obtained by STS and differential reflectance data (RDS), indicating that this scheme can provide quantitative predictions for electron and optical spectroscopies of nanoribbons on weakly coupled substrates such as Au.
Furthermore, the combination of RDS experiments and ab initio simulations beyond DFT allows us to catch nanoribbons in the act of their formation, following the build-up of their quasi-1D excitons. In fact, the main phases observed by RDS on Au –from isolated molecular precursors to the final nanoribbon structure obtained by intramolecular cyclodehydrogenation— are characterized by distinct signatures that we can assign to excitonic states with very different binding energies, a clear manifestation of the modified electron/hole localization and interactions induced by the changes in intermolecular bonding and conformation during the formation process.
All organic photovoltaics for renewable and sustainable energy production
Organic photovoltaics (OPV) represent the newest generation of technologies in solar power generation, offering the benefits of highly automated, low energy-consumption and cost-effective roll-to-roll production through printing, while providing the consumer with the added features of flexibility and low weight. With its unique features and potential for very low cost, OPV enables the development of new consumer nomadic applications and the long term possibility of easy deployment in Building Integrated Photo Voltaics (BIPV).
The current challenges reside in the combinations needed to increase efficiencies to 8-10% (module level), and to increase expected lifetime of up to 20 years, while decreasing production costs to 0.5 Eur/Wp, and taking into account the environmental impact and footprint. Here we will report on activities and results achieved within national and European networks, which bring together industrial, institutional and academic partners to make an impact on materials and processes, while demonstrating their market-relevant implementations.
Flatland: Electrons Moving at Surfaces
The movement of electrons in two dimensions is a pervasive theme in current condensed matter studies in physics and chemistry. We seek to learn how electron motion can be trapped by subtle surface barriers or how their motion can be manipulated by light or electron impact. We can probe this motion with ultrafast light pulses or high-energy-resolution electron spectroscopy. My talk will tell how we have examined this world in collaboration with teams at Elettra in Italy and those at Brookhaven National Laboratory in the US.
Functional materials based on carbon nanostructures
In combination with catalysts of different natures, carbon nanotubes and graphene can serve as energy transducers for many practical purposes. This lecture will focus on experiments aimed at the splitting of water molecules to give oxygen (and therefore molecular hydrogen), ideal properties for clean energy generation. Also, multi-walled carbon nanotubes, embedded inside mesoporous layers of oxides (TiO2, ZrO2, or CeO2), which in turn contain dispersed metal nanoparticles (Pd or Pt) produce nanocomposites with remarkable performance for the water−gas-shift reaction, photocatalytic reforming of methanol, and Suzuki coupling.
A quantum spin Hall effect in monolayer graphene without time reversal symmetry
The quantum spin Hall (QSH) effect is a two-dimensional electronic phase characterized by an excitation gap in the bulk but gapless, helical boundary states. Since its original discovery in HgCdTe quantum wells, the QSH effect has become nearly synonymous with the time-reversal invariant two-dimensional topological insulator. I will describe recent experiments in which we demonstrate a QSH effect without time reversal symmetry, realized by exploiting the particle-hole symmetry of the anomalous Landau level in monolayer graphene and the conservation of spin. Using large in-plane magnetic fields, we drive a transition from a spin-unpolarized insulating phase to a spin-polarized metallic phase with ~2e2/h conductance, in which we observe the nonlocal transport signatures of the QSHE. Simultaneous capacitance measurements, which probe the bulk, show that throughout the transition and into the QSH regime, the bulk gap never closes. The transition itself occurs via an intermediate canted antiferromagnetic state that hosts gapped, partially helical edge states.
James Yardley (Columbia University)
Alberto Morgante (CNR-IOM and Uni. of Trieste)
Tony Heinz (Columbia University)
Vittorio Pellegrini (CNR-Nano and Scuola Normale Superiore, Pisa)