UW MRSEC Highlights

Bridge-Dependent Interfacial Electron Transfer (2011)

Tue, 22 Mar 2011 11:22:29 -0500

Top: The kinetics of charge transfer from a rhenium-bypyridine complex to a TiO2 , measured for several molecular linkers (purple, black, red, and blue traces). Insets show the structure of the molecular systems, and infrared spectroscopy demonstrating the attachment of Re1C to TiO2.

Bottom: Calculated transition densities associated with the 1MLCT excited state (left, shown for the ReEC complex) and biothiophene Ïï®Ï* transition (right, Re2TC complex). The green shows areas of electron density depletion, and the yellow areas of excess density.

[Image461]Charge transfer across interfaces has an important fundamental role in materials with applications ranging from solar energy to photocatalysis. In dye sensitized solar cells, electrons are excited in a dye molecule by the absorption of light and subsequently injected into an inorganic semiconductor. IRG2 has resolved the electron injection kinetics of the dye sensitizer by optically probing the electrons transferred to TiO2 nanocrystal from a rhenium dye by using a mid-infrared....

Mechanisms of Organic/Inorganic Interface Formation (2011)

Tue, 22 Mar 2011 11:17:42 -0500

Left: (a) STM image of the Si(001) 2 x 1 surface prior to exposure to nitrobenzene. (b) STM image after exposure to 30 Langmuir of nitrobenzene. The inset arrow in (b) indicates the direction of the rows of nitrobenzene molecules, which are perpendicular to the substrate dimer rows.

Right: Potential energy surface of the structural evolution of nitrobenzene adsorbed on Si(001) at 1 ML coverage. Numbers in blue give the relative heights of the topmost H of the phenyl ring referenced to the height of that atom in the NO2 configuration. Numbers in black and red give the activation energy barrier in eV for the transformations between configurations shown in the insets.

Advanced organic/inorganic materials for applications including solar energy conversion and optoelectronics require the creation of interfaces with carefully controlled structural and electronic properties. Functional monolayers at these interfaces can have associated electronic states or dipole moments and thus provide a new degree of control over device properties. IRG 2 has already shown how functional interfaces incorporating electron acceptors and reconfigurable molecular dipoles can....

UW MRSEC Hosts Two National Events for NISE Net Museum Educators (2011)

Tue, 22 Mar 2011 11:10:17 -0500

Left:Workshop attendees watch professional actor, Damian Johnson, from the Science Museum of Minnesota present a NISE Net âIntro to Nanotechâ program during an evening reception at the Madison Childrenâs Museum.

Right: Dr Tracy Stefonek-Puccinelli (center) with her hands-on activity, âFrom Nature to Nanotech: Biomimicryâ.

The University of Wisconsin â Madison (UW) Materials Research Science and Engineering Center (MRSEC) on Nanostructured Interfaces hosted two national events for museum educators at the Madison Childrenâs Museum and on the UW campus. The first event, held February 28 â March 2, was a professional development workshop for partners of the Nanoscale Informal Science Education Network (NISE Net). The second event, March 2 â 4, 2011, was a peer critique meeting for....

Phonon Scattering in Intrinsic Graphene using Tight-binding Bloch Waves (2011)

Thu, 17 Mar 2011 11:16:30 -0500

Fig. 1 Probability density for a Bloch wave with wave vector k=(14.5, 7.9) nm-1, calculated using the nearest-neighbor tight-binding technique.

[Image458]The overall interest in graphene as a material for devices has led to tremendous advances in the knowledge of transport in graphene. However, there are still questions about the intrinsic limit to electron mobility. Recent experiments have demonstrated mobility greater than 107 cm2/Vs at 50 K temperature, exceeding previous theoretical predictions of the intrinsic mobility limit. Here, we present a simple model of phonon scattering rates in intrinsic graphene using electronic....

Transport in Ultra-Thin Silicon Membranes (2011)

Thu, 17 Mar 2011 11:13:52 -0500

Fig. A Top: Square symbols are the conductance of a 120 nm thick silicon membrane as a function of a back-gate voltage. The blue line is the simulated conductance without a direct contribution from mobile electrons in the surface pi* band. The blue curve includes such a contribution, and it is a much better fit to the experimental data. The lower panel shows the calculated Fermi level at both the surface and the back interface.

[Image457]Nanostructures are extremely sensitive to their surface properties. In the past year we have made extensive measurements of thin silicon films in ultra-high vacuum. We now have strong evidence that ultra-thin silicon with a 2x1 surface reconstruction is heavily influenced by the surface pi* band. Fig. A shows experimental measurements (black squares) of the conductance as a function of a back gate voltage for a membrane of thickness 120nm. There is a clear minimum in conductance....

Semiconductor Nanomembrane Tubes: Three-Dimensional Confinement for Controlled Neurite Outgrowth (2011)

Thu, 17 Mar 2011 11:09:16 -0500

In many neural culture studies, neurite migration on a flat, open surface does not reflect the three-dimensional (3D) microenvironment in vivo. With that in mind, we fabricated arrays of semiconductor tubes using strained silicon (Si) and germanium (Ge) nanomembranes and employed them as a cell culture substrate for primary cortical neurons. Our experiments show that the SiGe substrate and the tube fabrication process are biologically viable for neuron cells. We also observe that neurons are....

Industrial Consortium Growth and Activities (2010)

Fri, 01 Oct 2010 09:24:09 -0500

Jon McCarthy and Juan de PabloMembership in the Consortium has grown from the initial sponsor (2005: the Semiconductor Research Corporation) to 26 companies in 2010.Collaborative Membership has resulted in great productivity:1. Sigma Aldrich is the first Collaborative Member. (The first commercial project was produced this fall.)2. Business representatives and researchers propose criteria used to define new materials3. New materials are made available....

NanoArt: Reaching Broader Audiences through Art and Alterative Venues (2010)

Fri, 01 Oct 2010 09:24:01 -0500

TOP: Figure 1. Postcard image used to advertise the Sights Unseen: Images of the Nanoscale exhibit at Mother Foolâs Coffee House in Madison, WI.

CENTER: Figure 2. One of the cases at the Dane County Regional Airport highlights four research images from MRSEC scientists.

BOTTOM: Figure 3. Example of NanoArt image and description (for TINY): âTiny nanorods of zinc oxide are being explored for use in experimental solar cells. The diameter of the nanorods can be controlled by the addition of oligomers (short chain polymers) during the growth process. An equipment malfunction limited the oligomer addition during this experiment, resulting in nanorods with an unusual club-like shape. Name of scientist(s): Ryan Franking, Affiliation: MRSEC on Nanostructured Interfaces

Juan J. de Pablo and Greta M. Zenner Petersen[Image424]Toward sharing nanotechnology and materials science with a broader audience, the University of Wisconsin-Madison (UW) MRSEC has created and contributed to several nano-art exhibits that use authentic images from nanoscale research conducted at UW . Evaluation has shown that the breathtaking images draw people in and give a glimpse into the daily lives of nanoscience researchers, while generating awareness, teaching a simple lesson on....

Summer REU Program (2010)

Fri, 01 Oct 2010 09:23:41 -0500

The University of Wisconsin-Madison MRSEC and NSEC again teamed to host its annual REU in Nanotechnology and REU in Chemistry and Chemical and Biological Engineering programs. The two programs combined to offer 10 week summer research experiences to 18 students from around the country and Puerto Rico. The program also played host to two international students from Spain and Germany. The group included seven female researchers and 15 students from underrepresented groups. In addition to....

UW MRSEC and NSF Share Everyday Applications and Cutting-Edge Research with a Broad Audience at the 2010 AAAS Annual Meeting (2010)

Fri, 01 Oct 2010 09:22:49 -0500

LEFT: UW MRSEC graduate students and Education Director, celebrate three successful days of engaging with a wide range of audiences by posing with their giant balloon model of carbon nanotube. Minutes later, the graduate students and several young Family Science Days visitors took down the model and shared in the fun and noise of popping a large number of balloons.

RIGHT: UW MRSEC graduate students (L to R: Jose Sanchez Perez, Samira Azarin, Arrielle Opotowsky, and Josef Spalenka) show off their forms of carbon models as they set up the booth in anticipation of the opening day of the exhibit hall.

Juan J. de Pablo and Greta M. Zenner PetersenThe University of Wisconsin â Madison (UW) Materials Research Science and Engineering Center (MRSEC) on Nanostructured Interfaces partnered with the National Science Foundation (NSF) to lead interactive science and engineering activities for a wide range of audiences in the exhibit hall at the 2010 Annual Meeting of the American Association for the Advancement of Science (AAAS). The meeting was in San Diego, CA, from February 18-2UW....