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Wednesday saw a full day of technical talks as well as a presentation in Symposium X by Lionel Vayssieres of the International Research Center for Renewable Energy on pursuing a low-cost and sustainable way to generate hydrogen as a green energy source. In the evening, MRS honored award recipients during the Awards Ceremony.
The Awards Ceremony commenced on Wednesday evening, with a growing platform of MRS honors. Before announcing the award recipients, however, MRS President Oliver Kraft and MRS Past President Tia Benson Tolle paid tribute to the Meeting Chairs of the 2015 MRS Spring Meeting, who drew in 5000 presentations and 5500 attendees from 50 countries! Meeting Chair Lia Stanciu of Purdue University accepted the recognition on behalf of her colleagues: Artur Braun (EMPA), Hongyou Fan (Sandia National Laboratories), Ken Haenen (Hasselt University & IMEC vzw), and Jeremy A. Theil (Quantumscape, Inc.). Kraft also revealed the recipients of the 2015 Grassroots Grants funded through the Materials Research Foundation, and he recognized two new University Chapters.
In celebrating 30 years of publication of the Journal of Materials Research (JMR), Kraft announced the inaugural JMR Paper of the Year Award: “Thermophysical properties of SnO2-based transparent conductive films: Effect of dopant species and structure compared with In2O3-ZnO-, and TiO2-based films,” by Nobuto Oka and Saori Yamada of Aoyama Gakuin University, Takashi Yagi and Naoyuki Taketoshi of National Metrology Institute of Japan, and Junjun Jia and Yuzo Shigesato of Aoyama Gakuin University - JMR 29(15) 2014.
He then announced the Gold and Silver Graduate Student Award recipients.
Gold Graduate Student Awards
Neelkanth Bardhan, Massachusetts Institute of Technology
Valerio D'Innocenzo, Istituto Italiano di Tecnologia
Yiyang Li, Stanford University
Maria Lukatskaya, Drexel University
Edward Sachet, North Carolina State University
Jorik van de Groep, FOM Institute AMOLF
Zi Jing Wong, University of California, Berkeley
Jihyeon Yeom, University of Michigan
Chenjie Zeng, Carnegie Mellon University
Silver Graduate Student Awards
Hadiseh Alaeian, Stanford University
Assaf Ben-Moshe, Tel Aviv University
Matteo Bianchini, Institut Laue-Langevin
Jairo Diaz, Purdue University
Duc Duong, Stanford University
Jihyun Hong, Seoul National University
Po-Chun Hsu, Stanford University
Deep Jariwala, Northwestern University
Yong Lin Kong, Princeton University
Priyank Kumar, Massachusetts Institute of Technology
Jinxing Li, University of California, San Diego
Yahua Liu, City University of Hong Kong
Yiding Liu, University of California, Riverside
Simiao Niu, Georgia Institute of Technology
Hongjie Peng, Tsinghua University
Suchol Savagatrup,University of California, San Diego
Zhi Wei Seh, Stanford University
Anshul Sharma, Kent State University
Chenghao Wu, University of California, Berkeley
Xi Yin, University of Illinois at Urbana-Champaign
Yingjie Zhang, University of California, Berkeley
Nanjia Zhou, Northwestern University
MRS Vice President/President-Elect Kristi S. Anseth recognized the recipients of the MRS Postdoctoral Award endowed by the Jiang Family Foundation and MTI Corporation: Dustin Janes, The University of Texas at Austin, and Yuan Yang, Massachusetts Institute of Technology.
Anseth recognized the Outstanding Young Investigators: Karena W. Chapman of Argonne National Laboratory and Ali Javey of University of California, Berkeley.
She then recognized Seth R. Marder (Georgia Institute of Technology) for the Mid-Career Researcher Award endowed by Aldrich Materials Science, and John M. Carpenter (Argonne National Laboratory) for the Innovation in Materials Characterization Award endowed by Toh-Ming Lu and Gwo-Ching Wang.
Kraft returned to the podium to announce the 2015 MRS Fellows.
Symposium X: Frontiers of Materials Research
Lionel Vayssieres, International Research Center for Renewable Energy
Advanced Low Cost Energy Materials from Aqueous Solutions
Lionel Vayssieres has a dream: a low-cost and sustainable way to generate hydrogen as a green energy source using only a cheap semiconductor and the two most abundant and geographically balanced free resources available on this planet—the sun and seawater. The dream is a specific example of a major challenge facing today’s materials researchers: namely, the development of new materials that lead to new technologies, which lead to new industries accompanied by better jobs and improved living conditions. Vayssieres advocated a chemical approach based on nanoparticle arrays as a way to achieve this goal. With a comprehensive understanding of materials growth and properties relationships and the use of quantum confinement and nanoscale strategies, he showed that it is possible to raise the theoretical limits of materials performance. As desirable as this is, it’s value is limited if the improvements cannot be implemented on a large scale. This is an additional reason why the use of chemical methods to produce materials and structures is important.
In a whirlwind tour starting in the 1990s at the time that quantum-dot research was popular, Vayssieres demonstrated how to use nucleation and growth equations, thermodynamic modeling involving parameters such as surface tension, pH, and ionic strength, together with low-cost design to generate crystalline oxide arrays of quantum rods and dots with controlled orientation, size, and shape on various substrates at nano-, meso-, and microscales by aqueous chemical growth at low temperature. Early experiments with transition-metal oxides and eventually actinides validated the theoretical approach for particles in aqueous solution. Building on that success, the work progressed to coatings on a variety of substrates (including Teflon). Control of the thermodynamic parameters yielded a variety of sizes and shapes, while growth kinetics affected the orientation of the particle arrays.
One outcome was the rehabilitation of iron oxide, which had not been useful for dye-sensitized solar photovoltaics but became so in the form of nanorods with diameters matching the minority-carrier (hole) diffusion length, so that recombination would not occur, an example of how nanoscaling can change the properties of a material. Vayssieres completed the presentation by describing early experiments to test the idea of hydrogen production in seawater with quantum-dot-sensitized iron oxide quantum rods, which provided full visible light absorption. The requirements are more stringent than for photovoltaics because not only must charges be generated, separated, and collected, but they must also do chemistry in water. The experiments provided a proof-of-principle and work is continuing. They also demonstrated that top-level chemistry with very inexpensive materials like iron oxide is feasible.
Symposium C: Perovskite Solar Cells
Understanding Formation, Operation and Stability of Perovskite Solar Cells
Henry J. Snaith, University of Oxford
Henry J. Snaith and colleagues are working tirelessly to understand how perovskite solar cells work, why they work, and how to make them better. He provided a brief history of this nascent topic and suggested that the field is moving more and more toward the thin-film device architecture. One of the most fascinating topics today in perovskite solar cells is the source of the hysteresis in the J-V curves. Snaith provided one hypothesis and some experimental evidence that perhaps the hysteresis is due at least in part to the device contacts. He also addressed the concerns of long-term structural and thermal stability. Through a series of photoluminescence experiments, the team showed that the perovskite solar cells are quite resistant to phase changes due to stress factors such as heat. The thermal stability, however, remains somewhat challenging. Most perovskite solar cells degrade at 85°C in air over the course of a day. Devices incorporating FAPbI3, remarkably, showed much less instability under these conditions. Factors surrounding the perovskite crystallization process are among the most important variables for efficient device fabrication. The Snaith team and colleagues studied this process thoroughly using XRD and found that removal of the organic species plays a strong role in driving crystallization. Therefore they varied the source of the lead species and observed different crystallization rates. They determined the kinetics for crystallization and found that Pb(NO3)2 had the lowest required activation energy.
Symposium M: Nanoscale Heat Transport—From Fundamentals to Devices
Thermal Conductivity of Ultrathin Crystalline and Amorphous Silicon Nanotubes
Renkun Chen, University of California, San Diego
Due to their disordered nature, it is widely acknowledged that the thermal conductivity of amorphous structures are generally lower compared to their crystalline counterparts. However, Renkun Chen’s research team found that this does not apply for silicon nanotubes. The team discovered that amorphous-silicon (a-Si) displayed a higher thermal conductivity than crystalline-silicon (c-Si) nanotubes. Chen explained that the phonon softening observed only in c-Si was the reason behind this interesting phenomenon. The team concluded that there is a strong correlation between the thermal and mechanical properties of the silicon nanotubes. Moreover, for both c-Si and a-Si, the team learned that increasing the thickness of the nanotube led to an increase in thermal conductivity.
Symposium V: Resonant Optics—Fundamentals and Applications
2D Materials and Heterostructures: Towards an Age of Atomic-scale Photonics
Linyou Cao, North Carolina State University
Linyou Cao explores the realization of atomic-scale photonics, which are extremely flexible, exciton-based devices. The strong exciton binding energy in transition metal dichalcogenide monolayers (TMDCs) enables interesting properties. Cao’s group developed controlled scalable synthesis of molybdenum disulfide (MoS2) with high-quality, uniform surfaces, low defects, and high crystallinity, along with excellent control of the layer number. Studying the dielectric function of the MoS2, Cao found that it exhibited a strange behavior with increasing layer number—first it decreased, then increased. To understand this, Cao approached the problem with a quantum picture. He found that thick layers are described by a quantum well model, which assumes a constant excitonic binding energy, and very thin layers are described by a quantum confinement model, which assumes a varying excitonic binding energy. This model matched the experimental results very well. He plans to use MoS2 to develop atomic scale devices.
Symposium R: Photoactive Nanoparticles and Nanostructures
Bottom-Up Approaches for Precisely Nanostructuring Hybrid Organic/Inorganic Multi-Component Composites
Yang Qin, University of New Mexico, Albuquerque
Researchers have found that organics photovoltaics (OPVs) made with a controlled, periodic morphology and well-controlled domain sizes exhibit enhanced performance over bilayer and bulk heterojunction OPVs. As such, Yang Qin fabricated P3HT composite nanofibers through self-assembly to achieve ordering. Additionally, Qin studied the effects of attaching fullerene derivatives to the functionalized NWs, which increased the nanofiber widths (confirmed with SEM images). The P3HT NWs are shown to be well-ordered in straight lines. Additionally, the percentage of P3HT in face-on configurations increases with the use of composite fibers, rather than edge-on configurations, which allows for enhanced absorption. Qin’s work “demonstrates the feasibility of achieving stable and tunable morphologies in OPVs” through manipulation of ordering and functionalization. Future work will involve the addition of quantum dots on the P3HT NW surface, as this should enhance absorption further.
Symposium S: Semiconductor Nanowires and Devices for Advanced Applications
Nanowire-Based Bulk Heterojunction Solar Cells
Silvija Gradecak, Massachusetts Institute of Technology
The earth receives enough solar energy from the sun to fuel the entire earth for more than a year. Solar cells haven’t yet gained popularity as researchers are still working to develop photovoltaics (PVs) that are flexible, lightweight, and transparent. Nanostructures are advantageous for use in bulk heterojunction solar cells (HJSCs), as they demonstrate increased transport and absorption, and decouple these two processes. To investigate the effects of nanowires (NWs) in HJSCs, Silvija Gradecak blended gallium arsenide (GaAs) nanowires (NWs) with P3HT, spun on indium tin oxide (ITO), to form an organic PV (OPV). The OPV showed an efficiency of 2.3%, which is considered quite decent for such devices, attributing the GaAs NWs to providing enhanced light absorption. However, Gradecak revealed that the GaAs NWs in fact account for very little improvement in absorption, just 3%, and the increased device performance after the introduction of NWs was due to the ordering of P3HT, which enhances the transport properties. Therefore, she shifted her focus to improving the ordering of P3HT. Ultimately, Gradecak designed a device using graphene as a transparent electrode, zinc oxide NWs, and PbS quantum dots to achieve a device with 8% efficiency (a 4x increase!), which exhibits stable performance over three months of testing.
Symposium T: Graphene and Carbon Nanotubes
A Polymer Chemistry of Graphene
Klaus Müllen, Max-Planck-Institute for Polymer Research
Top-down approaches have been successful in producing bulk quantities of graphene nanoribbons, but the processes often leave the materials damaged. “This is a key message from my point of view,” Klaus Müllen said; “Chemical knowledge is still needed here.” Applying their insights as organic chemists to materials science, the Müllen group has developed a method for producing nitrogen-doped graphene with increased charge carrier density. These N-doped graphenes have found great utility so far in energy applications. By wrapping cobalt oxide inside of a graphene sheet, the high capacity of the inorganic material is married to the superior morphological properties of graphene, making an excellent battery material. N-doped graphene has also been incredibly useful in the oxygen reduction reaction inside fuel cells, with catalytic activity superior to platinum in both acidic and basic media. This is very promising since platinum is simply too expensive for mass production. While the energy applications of graphene have largely been realized, graphene has not been very useful in transistor applications because it lacks a bandgap. “Unless you are happy with a switch that will never be off, you must do something about it,” Müllen said. Using the molecular precursors synthesized in his group, many types of atomically precise graphene nanoribbons have been made with perfect edge structures.
Bottom-Up Solution Synthesis of Narrow Pristine and Nitrogen-Doped Graphene Nanoribbons
Alexander Sinitskii, University of Nebraska–Lincoln
Graphene is a great material with many uses, but the lack of bandgap limits its utility in electronics. Alexander Sinitskii is working to change this by providing gram-scale solution syntheses of narrow graphene nanoribbons, which have a bandgap greater than 1 eV. The group studied bulk quantities of graphene nanoribbons using a variety of microscopic and spectroscopic techniques. The high degree of structural integrity and lack of defects was indicated by the sharpness of the G-band in the Raman spectrum of the nanoribbons. Interestingly, these nanoribbons assemble into larger nanostructures that could be seen by AFM and STM. Bulk measurements on pellets of nanoribbons indicated that they were semiconducting in nature. In addition, the Sinitskii group has utilized chemical synthesis to introduce nitrogen-based doping motifs into the chevron-type graphene nanoribbons. Further processing of these materials into devices is the subject of ongoing investigation within the group.
Symposium DD: Tailored Disorder—Novel Materials for Advanced Optics and Photonics
Bioinspired Photonic Nanostructures with Short-Range Order
Hui Cao, Yale University
We detect colors from pigments, dyes, and paints via the chemical process of selective wavelength absorption. Nature, however, can also create colors via a physical process: interference effects as light interacts with the nanostructures on the surface of a material. Known as structural colors, these physically-formed hues can be found in iridescent beetle shells and butterfly wings, which transform when the angle of incident light changes as the periodicity varies at different angles. The feathers of certain birds, however, manage to retain the same color regardless the change in angle of incident light. Piqued by this suppression of iridescence, Hui Cao and her group determined the physical mechanism of color formation is due to short-range order created by neighboring air spaces in bird feather barbs. The researchers used self-assembly of polystyrene spheres to mimic the short-range order, while avoiding the complete crystallization that would generate long-range order. In making paint, they found at 1 µm thickness, blue light is reflected. Adding C to act as a melanin, or broadband absorber, they generated color, rather than grey. Interestingly, when the bird feathers first form, the homogeneous nature of the cell has no index contrast, so no color forms initially. It forms after the dying cells cut from nutrition undergo a phase separation that manages to stop before reaching the red region, which is a phenomenon not lab-replicable yet. It appears spinodal decomposition is in effect.
Symposium II: Organic Bioelectronics—Materials, Processes, and Applications
Flexible Optoelectronic Fibers for Multimodal Interaction with Neural Circuits
Andres Canales, Massachusetts Institute of Technology (MIT)
Dynamically mapping neural behavior during activity is an extraordinary challenge that requires implementing flexible, biocompatible, minimally invasive, and durable probes. Canales and colleagues at MIT have fabricated fiber-based probes that address these issues. Through a thermal drawing process, where a preform of a few cm in size is heated in a controlled manner to reduce it by more than 50 times, the researchers obtained a probe that is flexible (stiffness of 10 N/m), has 25% optical transmission at 500 μm curvature even after repeated deformation, and is durable (functions for over 2 months). When implanted into a mouse, the research team was able to optically stimulate motion (leg motion) and reproducibly record the neural activity as well as relate stimulation to motion to neural activity. For drug delivery applications, freely moving mice were injected with a neural signal blocker, CNQX, and their neural activity was successfully recorded at stages of pre-injection, drug interaction, and recovery from the drug. These electrodes continued monitoring for 2 months and are still functioning at 10 months. To further push the electrode size envelope smaller, the researchers utilized a multiple drawing step process that includes selective etching, producing electrodes with a signal-to-noise ratio of 13 ± 6 in a moving mouse. The research team hopes these developments will help to understand and map neural activity and treat conditions such as depression.
Flexible Multimodal Organic Devices for Neural Interface
Marc Daniel Ferro, Ecole Nationale Supérieure des Mines de Saint Etienne
Flexible implantable multimodal devices for neural interfaces have offered less invasive alternatives to monitoring neural activity in the brain. Organic transistors developed by Ferro and colleagues can now stimulate and record high-frequency electrical signals on individual neurons in the hippocampus. Utilizing organic electrochemical transistors (OECTs) and PEDOT:PSS electrodes yields tunable capacitance that can be exploited by deep brain stimulation applications. Once the organic transistors are implanted into the hippocampus, a single neuron can be stimulated and neural activity recorded; however, the area affected is localized. To increase the number of neurons that can be excited by OECTs, the researchers have used two-photon stimulation that can stimulate up to 35 neurons while recording with a PEDOT:PSS electrode with good signal-to-noise ratio. This work has potential for developing non-invasive tools for neural interfaces.
Symposium QQ: Plasma-Based Materials Science and Engineering
One-Step Generation of Alloyed, Core@Shell and Core@Shell@Shell Nanoparticles by Gas Aggregation
Yves Huttel , Instituto de Ciencia de Materiales de Madrid, Spain
The ever increasing popularity of nanotechnology has led to the increase in demand of multi-functional nanoparticles for advanced applications. Continued developments in the fabrication of these high quality nanoparticles remain crucial in the progress of the field. Yves Huttel of Instituto de Ciencia de Materiales de Madrid presented an improved design of the standard “ion cluster source (ICS)” process for the generation of high-purity nanoparticles. The standard ICS process utilizes one magnetron source to produce nanoparticles. Huttel’s new design called the “multiples ion cluster source (MICS)” is a one-step process which modifies the ICS by replacing the single magnetron with three independent magnetrons that can work individually. The new design is capable of producing alloyed nanoparticles and nanoparticles with core@shell (e.g., Co core in Au shell) and core@shell@shell (e.g., Co core in Ag shell further encapsulated by Au shell) structure. Up to 25 different combinations of nanoparticles can be fabricated using the MICS process. Furthermore, the size and chemical composition of the produced nanoparticles are controllable and tunable, making it an excellent process for the generation of high-purity nanoparticles.
Symposium VV: Science and Technology of Superconducting Materials
Superconducting Materials for LHC Upgrades
Amalia Ballarino, CERN
With CERN’s plan to expand their facilities, comes the challenges. One of which is the ability to build a better performing, higher energy Large Hadron Collider (LHC). Amalia Ballarino explained the target performance CERN wants to achieve to be able to build a more efficient LHC. The main focus of their project were the superconducting links and the magnets employed in the LHC. Ballarino proposed that the LHC will rely on the use of high performance 12T Nb3Sn quadrupole magnets to replace the present 8T Nb-Ti quadrupoles. MgB2 will also be used as the superconducting link between the cryogenic feed boxes and the magnet coils. The group also plans to use High Temperature Superconducting (HTS) dipole magnet insert, choosing between the two options: REBCO and Bi-2212 conductors. With these promising upgrades, we look forward to more exciting breakthroughs and developments coming from CERN.
Science as Art Winners
First Place Winners
Shang-Hsuan Wu, Academia Sinica
"Nano Peony Flower"
Jiayu Wan, University of Maryland
Yanwen Yuan, Nanyang Technological University
"Graphitic Carbon Nitride under UV Light"
Second Place Winners
Peter Weiss, CEA
"Andy Warhol's nano-Guitar "
Son Tung Ha , Nanyang Technological University
"The Perovskite Sunflower"
Magnus Jonsson, Linkoping University
Wednesday Poster Awards
Pteridine Redox Centers Inspired by Biological Energy Metabolism for Sustainable Rechargeable Batteries
Jihyun Hong, Seoul National University
Electronic Transport Studies of Hematite Nanoparticles for Photovoltaic Application
Jan Mock, Institute of Energy and Climate Research, JPUs
Terahertz Split Ring Resonators Using Displacement Current
Shao Liu, University of Minnesota
Not shown: Process Path Functions in Rolling and Heat Treating of Meta-Stable Cubic Zr-18Nb Alloy
Ali Tabei, Georgia Institute of Technology
MRS TV Video of the Day
Interview with Karena W. Chapman, 2015 MRS Outstanding Young Investigator Award Winner
Scanning the Meeting
About the Meeting Scene
- This Meeting Scene e-mail was compiled and edited by Judy Meiksin, with writers Jan Mary Bayolo, Ryan R. Cloke, Tanya Das, Alison Hatt, Arthur L. Robinson, Carol Tseng and Evangeline Wong. Photos are taken by Andrea Pekelnicky. Photo editing is performed by Rebecca Yokum. This newsletter is produced by Kirby Morris.
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