Mission:

This IRG will investigate metamaterials- particularly chiral, quasiperiodic and hyperbolic MMs – and MM-inspired structures with unusual properties such as near-field plates and hyperlenses, and develop understanding applicable to communication, sensing and imaging.

Research Overview:

Metamaterials (MMs) are homogeneous artificial mixtures, that is, composites for which the distance be-tween neighboring inclusions is significantly smaller than the wavelength of interest. Recent advances in assembly methods, micro- and nanofabrication, coupled with an increased understanding of their electro-magnetic (EM) response have led to the synthesis of composites whose behavior is quite unlike those of natural materials. Negative refraction, cloaking, plasmonic hot-spots, super-resolution, and high-frequency magnetism are but a few of the terms that were introduced into the scientific vocabulary during the past decade following continuous progress in MMs research. This IRG program provides a comprehensive approach for the development of novel composites; particularly chiral, quasiperiodic and hyperbolic MMs; and MMs-inspired struct

ures with unusual physical properties, such as near-field (NF) plates and hyperlenses. The research combines state-of-the-art self-organized, epitaxial growth and lithographic techniques with the development of innovative NF experimental tools, together with a strong theoretical basis and a multiplicity of characterization methods.

An example of the way recent breakthroughs in metamaterialsresearch has opened up new frontiers in photonics is the recent demoonstration by Shalaev and coworkers at Purdue that the high losses normally present in plasmonic MMs can be overcome by incorporating gain media within the composite. In another example, at the University of Michigan, Merlin and colleagues have devised novel structures such as near-field plates for superresolution imaging. Based on these and related  breakthroughs, IRG2 explores this newly opened frontier of MMs as a partnership between Michigan and Purdue, with additional collaborations from the University of Texas and Wayne State University.

IRG2 makes, models, and studies autonomous motors and pumps that convert the free energy of local chemical, optical, thermal, and acoustic fields to motion. In addition to providing information about the mechanisms of motility, the study of synthetic motors helps address fundamental questions about emergent collective behavior at low Reynolds number and on length scales from sub-nanometers to hundreds of micrometers. Much of our understanding of active matter derives from continuum theories coupled to observations of complex biological swimmers or externally driven colloidal particles. The observation in abiotic systems of many behaviors previously associated with purely biological processes suggest intriguing questions as to the underlying principles that govern both. The IRG2 team pursues a bottom-up approach to understanding motility, sensing and emergent collective behavior in autonomously driven synthetic systems by combining theory and numerical modeling with the synthesis and experimental study of new classes of motors.

Important findings in IRG2 include the discovery of synthetic autonomous nanomotors and micropumps driven by catalysis and light, elucidation of their self-electrophoretic propulsion mechanisms, discovery of complex swarming, predator-prey, and spatio-temporal oscillatory behavior in colloidal motor assemblies, engineering of chemotaxis, steering, and cargo delivery in motor systems, demonstration of catalytically powered motion at the nm scale of individual catalyst molecules, including (non-motor) enzyme molecules, characterization of momentum transfer by active swimmers at length scales from colloidal to molecular, and discovery of two new acoustic motor propulsion mechanisms that are tolerant of electrolyte solutions and gel media, including the interior of living cells.

The vision of this IRG is to drive, “Transformational improvement in solar energy conversion through fundamental materials innovation.”  There are two aspects to its strategy for realizing this vision. The first involves its core research mission directed at “Understanding, controlling and exploiting the unique properties of group IV nanostructures in photovoltaic architectures.” The second is to be an enabler acting as a “nucleation and growth point for a broad range of materials research in solar energy conversion.” The research program is directed at creating technology discontinuities that significantly shorten the time scale for solar energy to make a major contribution to world energy production. Critical to success is the Center’s integration of unique nano materials synthesis, novel characterization and computational interrogation. 

The vision of IRG-1, Electrostatic Control of Materials, is to use a set of new techniques for electrostatic manipulation of charge carrier density at material surfaces as a universal platform to probe and control electronic properties in novel materials. Recently developed methods based on ionic liquids, ionic gels, and solid electrolyte structures are being used to generate unprecedented charge densities in a variety of materials, up to significant fractions of an electron per unit cell, enabling dramatic property modification. Opportunities include reversible control of magnetic order and properties, fine-tuning of insulator-metal and superconducting transitions, novel electronic and opto-electronic device concepts, discovery of new electronic and magnetic phases, and determination of the limits of transport in new materials. The IRG is exploring three classes of materials of exceptional current interest as test cases: (i) organic conductors; (ii) metal chalcogenides; and (iii) complex oxides.

 

IRG 2: Molecular Crystal Growth Mechanisms assembles a team from Chemical Engineering, Chemistry, Mathematics, and Physics to investigate the fundamental science of molecular crystal growth, an area of vital interest for pharmaceuticals, organic electronics, and other technologies. While crystal growth of metals, semiconductors, and binary oxides is highly developed, understanding of basic elements of molecular crystal growth is lacking. The IRG advances the understanding of essential aspects of crystal growth science and engineering, investigating nucleation, dislocation generation and structure, multi-step assembly at the unit cell level, and origins of non-classical morphologies in molecular crystals. IRG 2 combines theoretical modeling, computer simulation, and experiment to develop predictive models  of crystal structure and free energy and to investigate the dynamic aspects of crystal growth.

 

Senior Participants: Daniella Buccella, Bruce. Garetz, David G. Grier, Maranda Holmes-Cerfon, B. Kahr, Robert Kohn, Jin Montclare, Mark Tuckerman, Michael D. Ward, Marcus Weck. 

Mission

• Answer fundamental questions about the basic properties of spin excitations in organic semiconductors (OSEC).
• Apply this knowledge toward development and fabrication of spin-related OSEC devices.

Why Organic Spintronics?

• Rich physics from the precursor polaron-pair state: spin-mediated organic electronics.
• Rich chemistry: OSEC are lightweight, environmentally friendly, inexpensive, and very versatile.
• Engineering and commercializationpotential: several existing companies focus on organic optoelectronics.

Questions

The goal of IRG-2 in Organic Spintronics is to provide insight to the following questions:

• Can we control the ratio between spin triplet and singlet excitations in OSEC and organic devices?
• Can we control and manipulate the interaction between spin-aligned carriers and nuclear spin polarization?
• Can organic-ferromagnet electrodes serve as spin injectors into OSEC?
• What are the temperature limitations of organic spintronics?
• Can we control the spin-injected current by an external electric field?
• Is there a Hanle effect in organic spin valves?
• How do we make devices stable?

Potential Applications

• Organic spin-valves → inexpensive mass-producible magnetic sensors (data storage).
• Spin-organic LED with color tuned by magnetic field → displays.
• Organic optoelectronic devices → environmental sensors (e.g., electronic properties change as a function of imbibed gas).
• Organic photovoltaics → more efficient, inexpensive, and robust solar cells.

The Materials Research Science and Engineering Center (MRSEC) at the University of Alabama carries out a vigorous program on materials with potential applications in ultra-high density data storage. Two interdisciplinary groups investigate thin films and particulate materials, respectively. Of particular interest in thin films are fundamental studies of magnetotransport, nanoscale surface studies, the investigation of high speed magnetic switching phenomena, as well as nanoscale tribological studies. In the area of particulate materials the focus is on potential applications in flexible (tape and floppy disk) storage media. Investigations include the synthesis of small, orientable magnetic nanoparticles, and the characterization and simulation of the microstructure of magnetic particle dispersions. The Center has an educational outreach program to high school science teachers and has very strong links with the information storage industry.

Principal Investigators
Robert J. Cava (Chemistry)
Andrew B. Bocarsly (Chemistry)

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No artificial photosynthesis process has yet been industrialized to economically produce chemical fuels from renewable feedstock. Our long‐term goal for this project is to find new semiconductor‐photocatalysts to increase the diversity and efficiency of energy converting materials while addressing the issue of the excess greenhouse gas CO2 in the atmosphere. One PI has extensive knowledge in solid‐state materials design, while the other is an expert in photoelectrochemistry. Specific goals of this project are: 1) To look for new semiconductor photocatalysts with robust corrosion resistance and suitable band‐gaps for water photolysis or CO2 reduction catalysis under visible light irradiation, with a focus on bandgap engineering through systematic doping and nitriding/sulfiding; 2) to develop synthetic methods that optimize photocatalysts’ efficiency in water photolysis and CO2 reduction and study their structural/physical‐photocatalytic property relationships; 3) to establish a straightforward electrochemical methodology to screen potential semiconductor‐photocatalysts by using a custom‐built photoelectrochemical cell that directly compares samples’ current density under dark and illuminated conditions and performs bulk electrolysis analysis.

The laws of equilibrium statistical mechanics impose severe constraints on the properties of conventional materials assembled from inanimate building blocks. Consequently, such materials cannot exhibit spontaneous motion or perform macroscopic work. Inspired by biological phenomena such as ciliary beating, Drosophila cytoplasmic streaming and actin treadmilling, this IRG will develop an entirely new category of materials assembled from animate, energy-consuming building blocks. Released from the constraints of equilibrium, such materials will acquire new functionalities.  For example, in contrast to conventional gels, which remain quiescent unless driven by external forces, the spontaneous internal flows of active gels exert macroscopic force on the boundaries of a rheometer. Such force-producing active fluids are just one example of highly-sought biomimetic functionalities that are found in internally driven active materials. Fully functional biological structures are fragile and difficult to control and are thus poorly suited for materials science applications. To overcome this limitation, we will develop tunable and robust biomimetic systems from a few well-characterized building blocks. These systems will serve as an ideal platform for developing novel material applications, testing fundamental models of far-from-equilibrium active matter, and potentially shedding light on self-organization in living cells. Ultimately, our work will bridge the chasm between the remarkable properties of animate biological organelles or cells and traditional materials science, which has focused on building inanimate structures.

Mission

• Understand the basic properties of surface plasmon polaritons (SPP) in conventional metals, their alloys, and exotic metals, from THz to the UV spectral range.
• Apply this knowledge to develop new devices and spectroscopic capabilities.

Why Plasmonic Metamaterials?

• THz Plasmonic Metamaterials
  • Conventional dielectric materials are lossy in the far-infrared
  • In contrast, conventional and exotic metals exhibit low loss
  • Almost no device technologies currently exist in the THz range
• Magneto-Plasmonics for Organic Spintronics
  • Spin polarization in organic spintronic devices diminishes with temperature due to smaller surface spin polarization
  • Use of magneto-plasmons may increase the spin polarization at the FM surface and reduce its temperature dependence
• UV Plasmonics
  • UV excitation allows access to resonant electronic states of photochemical precursors and biological molecules
  • Use Al and new alloys for high field enhancement in the UV
  • Localized immobilization and direct detection of biomolecules

Questions

The goal of IRG-1 is to provide insight to the following questions:

• What are the dielectric/magnetic/electronic property limitations for supporting SPPs?
• Can we synthesize appropriate materials to obtain the desired plasmonic response?
• What are the SPP properties of superconductors above and below the phase transition temperatures?
• To what extent do magneto-plasmons influence the spin polarization at the ferromagnetic/organic interface?
• To what extent can photochemical reactions be locally enhanced and spatially controlled?
• Can hot spots be used to interrogate chemical structure and reactions on the molecular scale?