NIST Technicalendar November 10 to November 14, 2008 The NIST Technicalendar is issued each Friday. All items MUST be submitted electronically from this web page by 12:00 NOON each Wednesday unless otherwise stated in the NIST Technicalendar. The address for online weekly editions of the NIST Technicalendar and NIST Administrative Calendar is: http://www.nist.gov/tcal/.

In this Issue: Meetings at NIST Meetings Elsewhere Announcements Talks by NIST Personnel NIST Web Site Announcements NIST Administrative Calendar (current)   NIST Vacancy Announcements (current)

Also available: Previous Issues of the Technicalendar Quick Technicalendar (current) Last week's Quick Technicalendar Last week's Technicalendar Detailed Search NIST Journal of Research (Current TOC) Change User Options

10:30 AM - Time-resolved photoluminescence as a sensitive probe of charge separation in colloidal semiconducting nanocrystals

No Scheduled Events

10:45 AM - Thermoelectrics: New Materials by Design?

10:30 AM - Designing a Sustainable Future: Industrial Chemicals from Renewable Feedstocks
10:30 AM - Design and Fabrication of 3D Photonic Crystals via Self-Assembly and Interference Lithography
10:30 AM - Spatio-Temporal Database Systems

10:30 AM - The Quest to Measure Longitude
2:00 PM - ELECTRONIC STRUCTURE AND TRANSPORT OF DISORDERED GRAPHENE

11/10 -- MONDAY

10:30 AM - CNST NANOFABRICATION RESEARCH GROUP: Time-resolved photoluminescence as a sensitive probe of charge separation in colloidal semiconducting nanocrystals
Electronic properties of nanomaterials such as colloidal CdSe nanocrystals (NCs) can be tailored by modifying their size and shape. This adaptability coupled with their ease of processability makes them very attractive materials for light-harvesting applications. Unfortunately the potential of NCs in photovoltaics have yet to be realized. This is due, in large part, to the complex electronic interactions of NC excitons with interfacial states and the surrounding environment, which can induce charge carrier dissociation into long-lived surface trap sites or external acceptor species. Unraveling the nature of these processes is a necessary step towards the creation of efficient NC-based solar cells, but progress in this field is significantly complicated by the inhomogeneous nature of NCs and by the involvement of states that are usually optically inactive. Time-resolved photoluminescence (PL) from CdSe nanocrystalline quantum dots reflects the radiative recombination rates from intrinsic exciton states and also contains information about non-radiative charge separation and recombination processes; however, interpretation of fluorescence transients is non-trivial and typical multi- or stretched exponential analyses yield little specific photophysical information. To address this problem, we have recently developed a method, based on classical Marcus electron transfer theory, whereby ensemble CdSe PL decays, measured over a wide temperature range, may be used to access pertinent information about the nature of charge separation processes in NCs. Using this method we are able to assess the influence of traps on the exciton population dynamics and, for the first time, quantitatively describe the transient PL of CdSe NCs in terms of well defined physical processes. These ideas can be extended to more complicated systems and I will discuss the potential for new PL-based techniques to probe carrier separation and recombination dynamics in multicomponent assemblies of NCs with molecules or other nanoscale systems.
Marcus Jones , Postdoc, University of Toronto, Department of Chemistry,.
Bldg. 217, Rm. H107. (NIST Contact: Nikolai Zhitenev, 301-975-6039, nikolai.zhitenev@nist.gov)


11/11 -- TUESDAY

No Scheduled Events

11/12 -- WEDNESDAY

10:45 AM - NIST CENTER FOR NEUTRON RESEARCH SEMINAR: Thermoelectrics: New Materials by Design?
Thermoelectric materials can use the Seebeck effect to convert thermal energy to electrical power, or, conversely, use the Peltier effect to provide solid-state cooling. Both cases provide useful devices but, unfortunately, their thermodynamic efficiencies are very low, ca. 10%. In principle, the efficiencies of thermoelectric devices could be increased considerably by increasing the electrical conductivity and reducing the thermal conductivity of the active materials. Results from recent efforts to produce more efficient thermoelectric materials will be presented, with an emphasis on novel ways to reduce thermal conductivity.
Mary Anne White , Dalhousie University.
235 Bldg, Rm. E100. (NIST Contact: John Copley, 301-975-5133, john.copley@nist.gov)


11/13 -- THURSDAY

10:30 AM - POLYMERS DIVISION SEMINAR: Designing a Sustainable Future: Industrial Chemicals from Renewable Feedstocks
Erik Hagberg , Archer Daniels Midland Company, Decatur, IL.
224 Bldg, Rm. A312. (NIST Contact: Kate Beers, 301-975-2113, beers@nist.gov)

10:30 AM - CNST NANOFABRICATION RESEARCH GROUP SEMINAR: Design and Fabrication of 3D Photonic Crystals via Self-Assembly and Interference Lithography
Three-dimensional (3D) periodic micro- and nano-structures are of interest to a variety of fields, including microfluidics, tissue engineering, and photonic crystals. This has fueled the development of various 3D microfabrication techniques. Two especially promising approaches are colloidal self-assembly and interference-based lithography. In this talk I will focus on my work in both of these areas, and address their relevance to photonic crystals research. First, I will discuss charge stabilized colloidal sediments. In these systems, strong electrostatic interactions give rise to colloidal crystals with long range order and large inter-particle separations. While they are highly ordered, these crystals lack the inter-particle contacts that impart mechanical stability, and thus do not retain their order when dried. In this work, the gradual addition of salt is used to attenuate the electrostatic repulsion. This contracts the colloidal lattice so that mechanically stable surface contacts are made. Using fluorescence confocal microscopy the particles' 3D locations are determined and their time resolved behavior is observed. This data is used to calculate translational and orientational order parameters that monitor changes in the crystalline structure. Finally, I will describe the design and fabrication of 3D structures using interference lithography. In this approach, the optical interference generated by four or more coherent beams of light creates a 3D periodic intensity distribution that readily transfers into photoresist. The central issue I will address is how to design optics such that a desired 3D structure is produced. To this end, an approach using genetic algorithms (GAs) was developed and applied to the techniques of holographic and phase mask lithography (PML). Examples of GA-based designs that generate diamond-like photonic crystals will be presented along with recent progress using PML to experimentally demonstrate chiral microstructures.
James Rinne , University of Illinois, Beckman Institute.
Bldg. 217, Rm. H107. (NIST Contact: James Liddle, 301-975-6050, james.liddle@nist.gov)

10:30 AM - ITL SEMINAR SERIES: Spatio-Temporal Database Systems
Abstract: Many spatio-temporal objects such as clouds, cars, hurricanes, planes and ships change position or shape continuously and sometimes also periodically. Although in the last decade substantial research was done independently in spatial and temporal data modeling, continuously changing objects require new data models that can capture the interdependency of the spatial and temporal extents of these objects. We describe several new spatio-temporal data models that capture the interdependency of the spatial and temporal extents. We also discuss spatio-temporal query languages, spatio-temporal interpolation algorithms, and data visualizationa nd animation methods. Applications will be illustrated using MLPQ, a prototype database system implemented at the University of Nebraska-Lincoln. Bio: Peter Revesz is a Full Professor in Computer Science and Engineering at the University of Nebraska in Lincoln. His research area is Database systems, including constraint programming, geographic information systems, and bioinformatics, and he has written many papers, the latest three being for 15th International Symposium on Temporal Representation and Reasoning (TIME 08) , the 11th International Conference on Extending Database Technology (EDBT 08),and the 13th East-European Conference on Advances in Databases and Information Systems (ADBIS 09). Peter got his B.S. from Tulane University in 1985 (summa cum laude) in 1985 and his Ph.D. from Brown University in 1991,advised by Paris Kanellakis. He also has developed 3 books, Introduction to Constraint Databases, Springer, New York 2002; (with Bart Kuijpers); Databases, Springer LNCS 3074, Paris, France , June 2004; and (with J. Pustejovsky, P. Revesz), eds., Proc. 13th International Symposium on Temporal Representation and Reasoning IEEE Press, Budapest, Hungary, June 2006; and is now working on another book.
Peter Revesz , University of Nebraska-Lincoln.
Administration Bldg, Lecture Rm. F. (NIST Contact: Larry Reeker, 301-975-5147, larry.reeker@nist.gov)


11/14 -- FRIDAY

10:30 AM - NIST COLLOQUIUM SERIES: The Quest to Measure Longitude
Throughout the great ages of exploration and sail, from the end of the fifteenth century to the end of the eighteenth, navigators lost track of their longitude almost the moment they lost sight of land. Although they understood, in theory, how to assess their progress east or west, they owned no practical method for determining a ship's position at sea. Warfare and commerce were hamstrung by that lack, and governments offered princely sums to spur invention. Some of the greatest names in the history of science, including Galileo, Huygens, and Newton, worked on the longitude problem without success--until an unknown, self-educated clockmaker from the north of England offered his singularly accurate timekeeper as the unlikely solution. Dava Sobel is an award winning author. Her best-selling books, Longitude and Galileo's Daughter, will be available for review and purchase before and after the lecture.
Dava Sobel , Science Journalist and Author.
Administration Building, Green Auditorium. (NIST Contact: Kum Ham, 301-975-4203, kham@nist.gov)
Special Assistance Available

2:00 PM - CNST ELECTRON PHYSICS GROUP SEMINAR: ELECTRONIC STRUCTURE AND TRANSPORT OF DISORDERED GRAPHENE
The unusual transport properties of graphene arise mostly from its Dirac spectrum. Close to the Dirac point the average carrier density vanishes and the density fluctuations are expected to dominate the physics of graphene. In this talk I will present a Thomas-Fermi-Dirac (TFD) theory to calculate the carrier density of graphene in presence of disorder. The approach is independent of the disorder source. I will present the results for the case when random charged impurities are the main source of disorder, the relevant situation for current experiments on exfoliated graphene. The TFD approach is able to quantitatively characterize the graphene density fluctuations at, and away from, the Dirac point, in good agreement with recent imaging experiments. In the second part of the talk I will discuss a transport theory for graphene, graphene Effective Medium Theory, that properly takes into account the strong density fluctuations close to the Dirac point and is able to answer semi-quantitatively some of the most puzzling questions that have been posed by transport experiments on graphene since its experimental realization.
Enrico Rossi , Physicist, Condensed Matter Theory Center, University of Maryland.
Bldg. 220, Rm. B165. (NIST Contact: Joseph Stroscio, 301-975-3716, joseph.stroscio@nist.gov)


ADVANCE NOTICE

11/17/08 10:00 AM - PHYSICS LABORATORY COLLOQUIUM: Multimodal, Dynamic, Intraoperative Imaging of Cancer
Accurate recognition of occult disease and appropriate assessment of surgical margins are important oncologic principles for reduced recurrence rate and improved long-term survival. However, many existing cancer imaging tools use single static modality to target a small piece of the complex puzzle, with very limited synergy available between individual modalities. We are developing an integrated cancer imaging platform for intraoperative dynamic imaging of tumor structural, functional and molecular characteristics. Such a cancer imaging platform seamlessly integrates multimodal imaging hardware, multimodal contrast agent, and multi-physics imaging algorithm.
Ronald Xu , Biomedical Engineering Department, The Ohio State University.
221 Bldg, Rm. B145. (NIST Contact: Kum Ham, 301-975-4203, kham@nist.gov)

11/24/08 10:30 AM - CNST NANOFABRICATION RESEARCH GROUP SEMINAR: Titania nanofibers as oxygen sensors
Transition metal oxides are widely used as catalysts in oxidation reactions and possess properties which are amicable for gas sensing. Among these materials, titania is attractive for gas sensing applications due to its n-semiconducting electrical character at moderate temperatures. Gas species interact with titania surface through charge transfer that can be monitored by changes in electrical conductivity. An improved surface reactivity and an increased concentration of electronic defects occur in nanostructured titanium oxides. Nanofibers arrangements prepared by annealing titania nanotubes have shown enhanced oxygen sensing capablities, e.g., their high electrical response is about two orders of magnitude higher than the values reported for coarse grained titanium dioxide. In addition to high oxygen sensitivity, these materials also have an extraordinarily fast (few ms) response time. The improved oxygen sensitivity of titania nanofibers is believed to arise from their enhanced electrical conductance controlled by surface defects states. Subsurface Ti interstitials and oxygen vacancies result from the surface dehydroxylation of titania nanotubes upon annealing. This seminar will discuss how titania structures with enhanced surface-to-bulk ratio, such as nanotubes and nanofibers arrangements, can be used for oxygen sensing devices with optimized characteristics (high sensitivity, short response time).
Daniela Dumitriu-LaGrange , Research Assistant, University of California,.
Bldg. 217, Rm. H107. (NIST Contact: James Liddle, 301-975-6050, james.liddle@nist.gov)

11/25/08 10:30 AM - CNST NANOFABRICATION RESEARCH GROUP SEMINAR: Broadband Optoelectronic Characterization of Individual Semiconducting Single-Walled Carbon Nanotubes
While single-walled carbon nanotubes (SWNTs) have shown tremendous potential for electronic and energy applications, a comprehensive understanding of their electronic structure is still lacking. One crucial limitation has been the availability of broadband optical data on structurally characterized SWNTs, due in large part to the specificity of experimental techniques to a limited spectral range and subset of diameters as well as the inaccessibility of the lowest energy optical transitions (spanning the near and mid infrared) in large diameter semiconducting SWNTs. In order to address this challenge, we have developed rapid, broadband, and high-resolution spectroscopic techniques for studying both the visible and infrared electronic states on an individual SWNT. We have accomplished this using a process which combines observation of resonant enhancement in the spectra of elastic scattered supercontinuum laser light with an infrared Fourier transform photoconductivity methodology. We present our determination of the optical response over the range of 0.3 to 2.7 eV from a set of SWNTs and examine the scaling of the optical features as a function of diameter and subband index. In contrast to traditional bulk inorganic materials, we find that optical excitation in these 1D nanostructures results in moderately bound excitons under ambient conditions. As a result, the ultimate utility of these materials in energy applications, either directly or as composite materials, depends on the rapid and efficient dissociation of the excitonic state. Using results from our infrared photoconductivity measurement, we will discuss the challenges in determining the mechanisms and potential efficiencies for exciton dissociation and collection in these and other 1D materials.
Matthew Sfeir , Brookhaven National Lab.
Bldg. 217, Rm. H107. (NIST Contact: Nikolai Zhitenev, 301-975-6039, nikolai.zhitenev@nist.gov)

---

MEETINGS ELSEWHERE


11/10 -- MONDAY

11:00 AM - CARNEGIE INSTITUTION OF WASHINGTON/GEOPHYSICAL LAB. SEMINAR: HYDROGEN IN HYDROGEN DOMINANT MATERIALS AT MEGABAR PRESSURES
M Eremets , Max Planck Institute for Chemistry, Mainz.
Bldg, Rm..
Greenewalt Bldg., GL-DTM Grounds, Carnegie Institution of Washington, DC. (NIST Contact: R. Hemley, 202-478-8900, seminar@lists.ciw.edu)



11/11 -- TUESDAY

No Scheduled Events

11/12 -- WEDNESDAY

No Scheduled Events

11/13 -- THURSDAY

No Scheduled Events

11/14 -- FRIDAY

No Scheduled Events

ADVANCE NOTICE

No Scheduled Events

---

TALKS BY NIST PERSONNEL

RITCHIE, N. : WHAT SPECTRUM SIMULATION CAN TEACH YOU ABOUT X-RAY MICROANALYSIS.
Carnegie Mellon University, Pittsburgh, PA, 11/10.

SOLES, C. : CRITICAL MEASUREMENTS TO FACILITATE THE DIRECT PATTERNING OF ORGANOSILICATE MATERIALS BY NANOIMPRINT LITHOGRAPHY.
Third International Symposium on Polymer Materials, Nagoya, Japan, 11/10.

KARIM, A. : STRUCTURE OF TEMPLATED ASSEMBLY OF BLOCK COPOLYMER FILMS BY ROTATIONAL SANS AND NR.
Third International Symposium on Polymer Materials Science, Nagoya, Japan, 11/10.

BOSSE, A. : FIELD-THEORETIC SIMULATIONS OF INTERFACIAL FLUCTUATIONS IN A NANO-CONFINED BLOCK COPOLYMER MELT.
Third International Symposium on Polymer Materials Science, Nagoya, Japan, 11/10.

PRABHU, V. : NEUTRON REFLECTIVITY MEASUREMENTS OF THE DISSOLUTION PROCESS IN CHEMICALLY AMPLIFIED PHOTORESISTS: CHARGED POLYMERS AT INTERFACES.
Third International Symposium on Polymer Materials, Nagoya, Japan, 11/11.

KARIM, A. : GUIDED SELF-ASSEMBLY OF BLOCK COPOLYMER FILMS ON TEMPLATES.
Kyoto Institute of Technology, Kyoto,Japan, 11/12.

DONAHUE, M. : EXPLOITING EFFECTIVE FIELD TIME DERIVATIVE INFORMATION TO IMPROVE ACCURACY OF A NORM-PRESERVING LANDAU-LIFSHITZ SOLVER.
53rd Magnetism and Magnetic Materials Conference (MMM 2008), Austin, TX, 11/12.

---

ANNOUNCEMENTS

WANTED: MUSEUM TOUR GUIDES
Calling All History Buffs! Do you have knowledge of, and interest in, NIST history? Would you like to learn more and share that knowledge with others? The NIST Museum is seeking volunteer museum tour guides. Guides are needed to provide museum tours, on an as-needed basis, to international visitors, conference attendees, student groups, and others who visit the museum. A training session for guides will be held in November. Please contact Keith Martin (x2789, keith.martin@nist.gov) if you are interested.
NIST Contact: Keith Martin, 301-975-2789, kmartin@nist.gov

INTERACTIVE LIBRARY AND PUBLISHING NEWS
We've revamped our library and publishing newsletter to include *your thoughts, *your ideas. We're taking our news and your comments to a new interactive level where we'll be conversing and exchanging information. ISD NewsCenter will release new articles or announcements twice a week. We hope you'll bookmark the site and return to it frequently or sign up to receive alerts. http://nvl-i.nist.gov/index.cfm?isdnewscenter/
NIST Contact: Nancy Allmang, 301-975-4189, nancy.allmang@nist.gov

HOW CAN YOUR LAB LIAISON HELP YOU?
Watch this new video podcast and learn what NIST Labs are saying about ISD's Lab Liaisons. (4+ minutes) http://nvl-i.nist.gov/index.cfm?videos/ISD_liaisons/
NIST Contact: Information Desk, 301-975-3052, library@nist.gov

VISITOR REGISTRATION FOR NIST EVENTS
Because of heightened security at the NIST Gaithersburg site, members of the public who wish to attend meetings, seminars, lectures, etc. must first register in advance. For more information please call or e-mail the "NIST Contact" for the particular event you would like to attend.
NIST Contact: . ., ., .

---

NIST WEB SITE ANNOUNCEMENTS

No Web Site announcements this week.

---

For more information, contact Ms. Sharon Hallman, Editor, Stop 2500, National Institute of Standards and Technology, Gaithersburg MD 20899-2500; Telephone: 301-975-TCAL (3570); Fax: 301-926-4431; or Email: tcal@nist.gov.

All lectures and meetings are open unless otherwise stated.

---

NVL Webmaster