Argonne National Laboratory Center for Nanoscale Materials U.S. Department of Energy

Amanda Petford-LongI am writing to you following a very busy period at CNM. The Argonne Users Meeting was held at the start of May, and the CNM played a very active role in the organization and running of the meeting, hosting joint symposia with APS and EMC. In addition, we hosted our own symposium and a number of very successful short courses, including one on scanning probe microscopy that attracted five vendors who brought instruments to the CNM.

During the last week in May, we completed our second planned maintenance period, which allowed us to carry out a number of essential maintenance activities. The CNM was closed to users for the duration, but by planning ahead in this way, we are able to make much more effective use of the time during these three yearly one-week closures. During the May period, CNM staff worked with the Argonne facilities staff to carry out preventive maintenance on the solvent exhaust system, installed a process cooling water manifold in one of the laser labs, upgraded the warm water system for the building heat supply, and upgraded the fire alarm system software, in addition to a number of other smaller but important activities. The third maintenance period will occur in the first week of September, following the Labor Day Holiday, so please plan your visits accordingly.

On the staffing front, I am delighted to announce that Maria Chan has joined the Theory & Modeling group as a staff scientist. Maria joins us following a postdoctoral fellowship appointment at CNM. Additionally, Volker Rose, who has a joint appointment between CNM and the Advanced Photon Source, received a DOE Early Career Research Award to develop a novel STM at the Nanoprobe beamline; we wish him all the best with this project. CNM also recently appointed two new CNM Distinguished Postdoctoral Fellows. The first to join CNM is Ji Sun Moon who will work with Seth Darling beginning this month.

In the past few months, the CNM held two internal equipment competitions, one for lower-value items and one for larger-value items. I am very grateful to the CNM Users' Executive Committee for assisting with the review of the latter proposals. As these items are added as user capabilities, we will update the facility web pages; in addition some of them may be featured in future editions of this newsletter.

I hope that you all have a pleasant and successful summer, and I look forward to welcoming you to CNM.

Amanda Petford-Long, CNM Director

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Call for Proposals Deadline: July 13, 2012

The system is now open for submissions. We look forward to the possibility of hosting your exciting and innovative nanoscience and nanotechnology projects. (More >>)

APS/CNM/EMC Users Meeting May 7-10, 2012

The Argonne APS/CNM/EMC Users Meeting took place on May 7-10, 2012. Over 500 registrants, including 100 vendors from 48 exhibitor booths, participated in a wide array of events. Thematic workshops on energy systems, imaging, and interfacial biological/environmental systems highlighted, promoted, and stimulated user science from the CNM, the Advanced Photon Source and Electron Microscopy Center. In addition, there were keynote and plenary science lectures, a CNM facility-specific workshop on "NanoBio Interfaces: From Materials Design to Complex Systems," poster sessions, a vendor expo, short courses, and social events. The CNM Best Student Poster Prize winners were Raman Shah (University of Chicago) and Poh-Keong Ng (University of Illinois at Chicago). Meeting details and photos are available online.

Users' Executive Committee Updates

CNM is pleased to announce that the two newly elected CNM Users' Executive Committee members are Dr. Seungbum Hong of Argonne's Materials Science Division and Prof. Carmen Lilley of the University of Illinois at Chicago. Completing their terms were Prof. Yi Ji of the University of Delaware and Dr. Gregory Wurtz, King's College London. Dr. Wurtz, as past Chair, remains as an ex officio member. The current Chair is Dr. John Freeland of the APS and the Vice-Chair is Prof. Steven May of Drexel University.

Summer Lab Attire

Now that the summer months are upon us, it's a good time to remind everyone of appropriate lab attire. Recall that, in the laboratory wing, sandals, shorts, and sleeveless tops are not allowed. Please plan accordingly, email any questions to the CNM User Office, and have a safe and successful laboratory experience.

CNM Closed to Users September 3-9, 2012

From September 3-9, 2012, no users are allowed to work in CNM laboratories in Buildings 440 and 441, nor will they able to access the Carbon high-performance computing cluster. The closure dates are inclusive and include the Labor Day holiday and the following weekend. The CNM will re-open for users on Monday, September 10. Please plan your work visits and schedules accordingly.

To better ensure reliable instrument availability at CNM, defined maintenance periods occur three times per calendar year. During these times the CNM is not available for user activities. The maintenance periods, lasting one week each, are used to perform preventive maintenance on the scientific instruments and their support equipment. In addition, the facility's operating infrastructure systems will undergo preventive maintenance that will help avoid unplanned shutdowns. The maintenance periods occur at these times:

  • First week in January following the December holiday break
  • Last week in May before the Memorial Day holiday break
  • First week in September following the Labor Day holiday break

User Notes

Acknowledgment of the use of DOE user facilities in scientific publications and technical presentations is vital for their future sustainability. An acknowledgment statement must be included in all published reports of work conducted at CNM. (Review the guidance.)

We are excited to chronicle the scientific advancements of CNM's users by your user activity reports. Since time is becoming more competitive, completion of reports on past projects is now required for consideration of new proposals.

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Computational Catalyst Design of Subnanometer Clusters

A review of computational catalyst design methods, many of which were performed using the CNM's high-performance computing cluster, Carbon, for the construction and optimization of subnanometer clusters, was undertaken recently by a team of users from Argonne's Materials Science Division and the Air Force Research Lab at WPAFB working with the Theory & Modeling Group. Computational catalyst design has predominately focused on solid heterogeneous catalysts, but clusters of atoms at the nanoscale comprise an emerging class of interesting industrial catalysts. The origins of activity and selectivity for supported metal clusters that catalyze the production of propene and propylene oxide are identified, along with the implications for implementing a descriptor-based catalyst optimization. The ideas were then applied towards designing an optimized methanol decomposition catalyst comprised of subnanometer clusters. In the volcano plot shown, the predicted maximum for methanol decomposition was found for clusters such as PdCu3, Pd3Co, and Pd2Co2; the least active clusters are PdAu3, Ag4, and Au4. Elucidating structure-activity relationships is challenging, but these results demonstrate that tailoring catalysts at the nanoscale using the defined relationships is viable.

Ferguson et al., "Exploring computational design of size-specific subnanometer cluster catalysis," Topics in Catalysis, 55, 353 (2012).

Mehmood et al., "Trends in methanol decomposition on transition metal alloy clusters from scaling and Bronsted-Evans-Polanyi relationships," Phys. Chem. Chem. Phys., 14, 8644 (2012).

Volcano plot of change in adsorption energy

A volcano plot relating the change in adsorption energy of CO molecules vs. O atoms binding against the reactivity to methanol decomposition for various bimetallic clusters. Cluster activity increases from blue (least) to red (most). 

Hollow Iron Oxide Nanoparticles for Battery Applications

A team of users from Argonne's Chemical Science & Engineering and X-Ray Science divisions as well as the University of Chicago, working with the NanoBio Interfaces Group, examined the electrochemical performance of hollow nanoparticles for lithium ion battery applications, as both cathode and anode materials. Hollow γ-Fe2O3 nanoparticles were obtained by annealing of the core/shell nanoparticles. The hollow γ-Fe2O3 nanoparticles display excellent capacity retention and superior rate performance, unlike solid iron oxide cathodes. Synchrotron X-ray diffraction and absorption spectroscopic techniques examined structural changes occurring during the lithiation process. Also a new electrode design using chemically synthesized nanoparticles was developed that demonstrates significantly improved capacity retention. Thin free-standing electrodes without binders not only decreases the weight of the batteries but also enhances connectivity between nanoparticles and current collectors, which is an issue for conventional nanoparticle-based electrodes.

Koo et al., "Hollow iron oxide nanoparticles for application in lithium ion batteries," Nano Letters, 12, 2429 (2012).

TEM of hollow iron oxide nanoparticles

Transmission electron microscopy of hollow iron oxide nanoparticles showing lattice fringes.

Shedding Light on Nature's Nanoscale Control of Solar Energy

Nature's process for storing solar energy occurs in light-absorbing protein complexes called photosynthetic reaction centers (RCs). A common light-absorbing hexameric cofactor core carries out the first chemical reaction of photosynthesis, a light-induced electron transfer across approximately 3 nm. This process has direct analogies to light-driven charge separation in photovoltaic devices. A team of users from the Notre Dame Radiation Laboratory and Argonne's Chemical Sciences & Engineering Division working with the Nanophotonics Group have carried out experiments that shed new light on how this process occurs. Using the CNM's ultrafast transient absorption spectrometers, individual cofactors in RCs were monitored through careful orientation of the polarizations of the pump and probe pulses relative to the crystallographic axes of the single crystals. This work provides a clearer, more detailed picture of the first steps in photosynthetic energy conversion, identifies a role for delocalized excited-states, and provides new experimental and data analysis approaches for studying the unusual efficiency of light harvesting and charge separation processes in natural photosystems.

L. Huang et al., "Cofactor-specific photochemical function resolved by ultrafast spectroscopy in photosynthetic reaction center crystals," Proc. Nat. Acad. Sci., 109 (13), 4851 (2012).

Scanning tunneling microscopy tips

A RC hexameric core, featuring a pair (P) of bacteriochlorophyll (BChl) molecules, and the (a) active and (b) inactive arms of BChl and bacteriopheo-phytin (BPh) molecules. The transient absorption (ΔA) spectra acquired following selective excitation of P are shown.

Ultrananocrystalline Diamond-Coated Membranes Show Promise for Medical Implant Applications

Ultrananocrystalline diamond (UNCD) displays biological and mechanical properties that make it a promising choice for promoting epidermal cell migration on percutaneous implant surfaces. A team of CNM users from the University of North Carolina and North Carolina State University, working with the Nanofabrication & Devices Group, coated silicon nitride microporous membranes with ultrathin (~150 nm) ultrananocrystalline diamond films. Scanning electron microscopy (SEM) and Raman spectroscopy were used to examine the pore structure and chemical bonding of the resulting membrane, which displays pore diameters in the 30- to 50-nm range. Growth of human epidermal keratinocytes on uncoated and UNCD-coated silicon nitride membranes was compared by using the 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay. Both membranes displayed increased cell growth due to their porosity, and the UNCD coating did not alter the viability of human epidermal keratinocytes. The team demonstrated that their method also works on nanoporous anodized aluminum oxide (AAO) membranes that are coated with UNCD to reduce the pore size down to 30-50 nm. Because of the exceptional chemical and mechanical properties of UNCD, it is expected that UNCD will provide a more stable implant-tissue interface than silicon nitride.

Skoog et al., "Ultrananocrystalline Diamond-Coated Microporous Silicon Nitride Membranes for Medical Implant Applications," JOM, 64, 520-525 (2012)

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SEM image of AAO membrance coated with UNCD

SEM image of AAO membrane coated with tungsten followed by UNCD exhibits 30- to 50-nm pore diameter.

Xactic X4 Xenon Difluoride Vapor Etching System

The Xactic X4 system is a relatively new instrument housed in the clean room facility of the CNM's Nanofabrication & Devices Group. It is a dry isotropic etching tool that is extremely useful for patterning and creating free-standing nanostructures. Xenon difluoride (XeF2), which is used as the etching gas, exhibits the highest etching selectivity for silicon versus many materials. For example, the selectivity to silicon nitride is better than 100:1, and the selectivity to silicon dioxide is reported to be better than 10,000:1. As a consequence, this system is very popular in the nanoelectromechanical systems (NEMS) community and is used to etch silicon in the presence of photoresists, silicon dioxide, silicon nitride, and aluminum. The Xactic can also be used for etching backside silicon, polysilicon, molybdenum, titanium, and tungsten. The sizes of materials that can be accommodated range from small pieces up to a 6-inch substrate. The types of etching include pulsed etching, pulsing with N2, and continuous XeF2 flow. Fast etching times are possible because of two expansion chambers. Controls include a touch screen and data logging capability. An attached microscope for real time monitoring of the beam release process is also included. Because the process is dry, there are no stiction problems when releasing a beam, thus no need to do a critical point drying step. Finally, the Xactic X4 system also has high selectivity with thermal oxide and photoresists. Contact Suzanne Miller of the Nanofabrication & Devices Group for more information.

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Xaxtic X4 vapor etching system

CNM's Xactic X4 xenon difluoride vapor etching system

Microchannel etched with xenon difluoride

A microchannel etched with XeF2 on a silicon substrate (image is approximately 50x50 micron in scale)

Volker Rose

Volker Rose, of Argonne's X-Ray Science Division and the CNM X-Ray Microscopy Group, received a 2012 DOE Early Career Research Program award. Volker's award allows him to develop a novel high-resolution microscopy technique for imaging nanoscale materials with chemical, electronic, and magnetic contrast. These five-year awards are designed to bolster the nation's scientific workforce by providing support to outstanding researchers during the crucial early years of their careers and to provide incentives for scientists to focus on mission research areas that are a high priority for the DOE and the nation. (More>>)

Maria Chan

Maria Chan joined the CNM in March as an assistant scientist in the Theory & Modeling Group. Maria completed her PhD in physics at MIT in 2009 and, after a brief postdoctoral fellowship there, came to Argonne as a postdoctoral associate in the Theory & Modeling Group and the Center for Electrical Energy Storage. Maria's research is in the computational prediction of materials properties, using first principles, atomistic, and data mining methods, particularly in applications towards materials relevant to energy technologies. Her goals include building effective physical models for computationally efficient predictions and optimization.

Ji Sun Moon

This month, Ji Sun Moon joins the Electronic & Magnetic Materials & Devices Group as a CNM Distinguished Postdoctoral Fellow. Ji Sun obtained her PhD in 2011 from UC-Santa Barbara's Dept. of Materials under Prof. Alan Heeger and will work at CNM with Seth Darling on nanomorphology control for high-efficiency organic photovoltaics.

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