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April 2012

Next-Gen Tools for Smart, Designer Materials

Scientists explore state-of-the-art tools for synthesis and characterization of novel materials for alternative energy

Sanchita Biswas

New tools for synthesis and characterizations of materials to solve the energy problem are shown. Synthesis of metal-nanoclusters inside a millifluidic reactor (inset: schematic design) and growth is investigated by synchrotron-based x-ray absorption (inset: graph).

Atomic layer deposition technique and transmission electron microscopy images showing the formation of lead sulfide quantum dots on nanowire surfaces.

To meet the increasing demand for energy, the Energy Frontier Research Centers are developing powerful tools and techniques for synthesis of materials. Scientific tools are being investigated in all of the EFRCs to save time, labor, energy and other resources. A combination of computational, synthesis and characterization techniques are being developed to design and generate novel materials for sustainable and clean-energy applications including fuel cells, batteries, solar cells, biomimetics and catalysts.

Making high-quality materials with precise atomic control is the key to achieving these energy applications. The next generation of tools and techniques, including the novel use of tiny amounts of liquids and tiny islands of lead sulfide along with a fast approach to avoiding dead ends, are highlighted here.

A Smart Play: Lab-on-a-Chip and Millifluidics

Lab-on-a-chip with dimensions similar to a thick line doodled on a notebook is gaining attention as a way to synthesize nanomaterials, clusters measured in atoms. The lab-on-a-chip is of interest because of its inherently efficient mixing, minimal consumption of feedstocks and ease of tuning the reaction conditions. However, expensive fabrication cost and intricate designs have limited their widespread application.

Hence, combining lab-on-a-chip with the novel concept of millifluidics, a bridge between bulk and microfluidic synthesis that uses very small amounts of liquids, is under development by a research group from the Center for Atomic Level Catalyst Design. This is an inexpensive, versatile and easy-to-use way to prepare metal clusters consisting of as few as 100 atoms or less.

“Millifluidics is a user-friendly and sensitive tool for time-resolved kinetic studies due to its higher signal-to-noise ratio and ease of handling,” said Challa Kumar, the leading scientist in the group.

Applying the millifluidic concept, copper nanocluster catalysts were prepared and tested on a reaction that adds oxygen to hydrocarbons, as a model reaction. Together with Jeffrey Miller from the Institute for Atom-Efficient Chemical Transformations, the team is focusing on forming atomically precise metal clusters within millifluidics using synchrotron radiation-based x-ray absorption spectroscopy. Results from the study recently appeared in Small.

Building Atom by Atom

Using atomic layer desorption, a team of researchers led by Fritz B. Prinz from the Center on Nanostructuring for Efficient Energy Conversion has developed a new way of making 3D nanostructures, called quantum dots, which have the potential to exceed traditional limits on solar cell efficiency. Atomic layer deposition, or ALD, is a thin-film fabrication technique capable of depositing materials with atomic-scale control of thickness and composition. Compared to earlier prevalent techniques for fabrication, ALD provides better control with subnanometer precision in film thickness and a special coating of high-aspect ratio surfaces, without the need for a hard-to-remove chemical typically used to stabilize the nanomaterials.

The team is exploiting ALD growth conditions to form clusters that are randomly distributed on the curved silicon nanowire surface.  These clusters become more pronounced with annealing. A highly accurate microscopy method, high-resolution transmission electron microscopy, reveals the fundamental growth mechanism of the quantum dots as a function of time (see the article in Nano Letters to learn more). This new material and technique combination, by tailoring the optical properties of 3D nanostructured materials, could find applications in solar cells, sensors and photocatalysts.

A New Way: Identifying the Winner

Sometimes it is frustrating in a synthetic research laboratory dealing with a “no-use” end product after time-consuming, tedious multistep materials synthesis and testing. Fast systematic screening of many candidate materials at the early stage could be a very attractive strategy to save time and effort later in the game.

Researchers at the Center for Inverse Design apply an innovative combinatorial and high-throughput, or CHT, experimentation approach for rapid screening of energy materials. CHT synthesis and characterization quickly identifies the best-of-class material that will subsequently become the subject of in-depth research. The CHT method relies on spatially resolved measurements of large arrays of materials on one chip obtained by intentional manipulation of synthesis parameters. The method allows for a 10- to 1000-fold increase in rate of experimentation with materials. This approach can be applied to materials with nearly any functionality, including thermoelectric, organic polymers, metal alloys and battery materials.

Progress in developing new ways to create materials and study the molecular or atomic-level growth facilitates materials synthesis tremendously.

More Information

Biswas S, JT Miller, Y Li, K Nandakumar and CSSR Kumar. 2012. “Developing Millifluidic Platform for Ultra-small Nanoclusters (UNCs): Ultra-small Copper Nanoclusters (UCNCs) as a Case StudySmall 8(5):688-698. DOI: 10.1002/smll.201102100

Dasgupta NP, HJ Jung, O Trejo, MT McDowell, A Hryciw, M Brongersma, R Sinclair and FB Prinz. 2011. “Atomic Layer Deposition of Lead Sulfide Quantum Dots on Nanowire Surfaces.” Nano Letters 11(3): 934-940. DOI: 10.1021/nl103001h

Zakutayev A, JD Perkins, PA Parilla, NE Widjonarko, AK Sigdel, JJ Berry and DS Ginley. 2011. “Zn–Ni–Co–O Wide-Band-Gap P-Type Conductive Oxides with High Work Functions.” MRS Communications 1(1):23-26. DOI: 10.1557/mrc.2011.9

About the author(s):

  • Sanchita Biswas is a postdoctoral researcher at Louisiana State University and a member of the Center for Atomic-Level Catalyst Design, an Energy Frontier Research Center. She received her Ph.D. in chemistry from the University of Central Florida in 2010. Her research interests are in the design, synthesis and evaluation of nanomaterials, based on organic polymers and atomically precise inorganic metal nanoclusters using “lab-on-a-chip” devices, for potential biomedical, catalysis and energy applications.

More Information

Biswas S, JT Miller, Y Li, K Nandakumar and CSSR Kumar. 2012. “Developing Millifluidic Platform for Ultra-small Nanoclusters (UNCs): Ultra-small Copper Nanoclusters (UCNCs) as a Case StudySmall 8(5):688-698. DOI: 10.1002/smll.201102100

Dasgupta NP, HJ Jung, O Trejo, MT McDowell, A Hryciw, M Brongersma, R Sinclair and FB Prinz. 2011. “Atomic Layer Deposition of Lead Sulfide Quantum Dots on Nanowire Surfaces.” Nano Letters 11(3): 934-940. DOI: 10.1021/nl103001h

Zakutayev A, JD Perkins, PA Parilla, NE Widjonarko, AK Sigdel, JJ Berry and DS Ginley. 2011. “Zn–Ni–Co–O Wide-Band-Gap P-Type Conductive Oxides with High Work Functions.” MRS Communications 1(1):23-26. DOI: 10.1557/mrc.2011.9

Disclaimer: The opinions in this newsletter are those of the individual authors and do not represent the views or position of the Department of Energy.