Four workshop participants, Jennifer Sinclair Curtis of the University of Florida, Michael Postek of the National Institute of Standards and Technology (NIST), Pierre Ricou of Arkema, and Richard Conroy of the National Institute for Biomedical Imaging and Bioengineering (NIBIB) at the National Institutes of Health (NIH), were asked to provide closing comments. Chosen for their diverse perspectives, each panelist discussed what he or she heard during the workshop and what some next steps might be. The panel comments were followed by an open discussion period when all workshop participants were given the opportunity to respond to the panelists and raise additional issues.
Jennifer Curtis heard three main topics discussed during the workshop: implications, understanding complex processes, and new characterization techniques for small particles. She said that health and environmental implications seem to motivate much of the work in characterizing and modeling small particles. Given that motivation, there is a need for greater understanding of fine particles and the dynamics of their behavior. There is another need to define the methods that are capable of distinguishing between single nanoparticles and agglomerates.
A key takeaway message for Curtis was that the modeling community faces some validation challenges related to the lack of detailed experimental data. She believed it would be useful to the field to compile a database of the available characterization techniques and their key features in terms of the type of material they can handle and the characteristics and properties that they measure. Such a database may increase the use of these powerful techniques in areas beyond those for which they were developed.
Mike Postek was struck by the obvious need to make multiple measurements on the types of complex that represent nanomaterials found in the real world. He noted the development of a wide range of new tools for nanomaterial characterization and the continuing advances being made with instrumentation, such as the applications of the soft x-ray tomography, the cryogenic light aberration-corrected transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and in situ TEM. He also raised the need for a database of available technologies.
Postek expressed a worry that cuts to research and development budgets, particularly in industry, are hampering technology development at a time when need in the nanocharacterization field is growing. However, he also noted that a great deal of advanced characterization technology is available at the national laboratories and at NIST, along with investigators who are more than willing to collaborate and cooperate in this area.
Modeling also touches on complexity, Postek said. Industry needs tools to model complex composites for use in high-performance applications. The potential cost savings from having models capable of predicting material performance would be huge, as it would be if models were available to predict the effect that process variables have on the properties of materials with complex surfaces and surface chemistries.
Pierre Ricou’s impression was that small-scale characterization is a focal point for many different parts of the nanotechnology world. From industry’s perspective, there is a need to characterize and understand the properties of materials to cre-
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6 Workshop Wrap-up Session ADDRESSING COMPLEXITY Four workshop participants, Jennifer Sinclair Curtis of the University of Florida, Michael Postek of the National Mike Postek was struck by the obvious need to make Institute of Standards and Technology (NIST), Pierre Ricou multiple measurements on the types of complex materials of Arkema, and Richard Conroy of the National Institute that represent nanomaterials found in the real world. He for Biomedical Imaging and Bioengineering (NIBIB) at the noted the development of a wide range of new tools for National Institutes of Health (NIH), were asked to provide nanomaterial characterization and the continuing advances closing comments. Chosen for their diverse perspectives, being made with instrumentation, such as the applications of each panelist discussed what he or she heard during the the soft x-ray tomography, the cryogenic light microscopy, workshop and what some next steps might be. The panel aberration-corrected transmission electron microscopy (TEM) comments were followed by an open discussion period when and scanning electron microscopy (SEM), and in situ TEM. He all workshop participants were given the opportunity to also raised the need for a database of available technologies. respond to the panelists and raise additional issues. Postek expressed a worry that cuts to research and devel- opment budgets, particularly in industry, are hampering PATH FORWARD technology development at a time when need in the nano- characterization field is growing. However, he also noted Jennifer Curtis heard three main topics discussed dur- that a great deal of advanced characterization technology is ing the workshop: implications, understanding complex available at the national laboratories and at NIST, along with processes, and new characterization techniques for small investigators who are more than willing to collaborate and particles. She said that health and environmental implica- cooperate in this area. tions seem to motivate much of the work in characterizing M odeling also touches on complexity, Postek said. and modeling small particles. Given that motivation, there Industry needs tools to model complex composites for use is a need for greater understanding of fine particles and the in high-performance applications. The potential cost sav- dynamics of their behavior. There is another need to define ings from having models capable of predicting material the methods that are capable of distinguishing between single performance would be huge, as it would be if models were nanoparticles and agglomerates. available to predict the effect that process variables have on A key takeaway message for Curtis was that the modeling the properties of materials with complex surfaces and surface community faces some validation challenges related to the chemistries. lack of detailed experimental data. She believed it would be useful to the field to compile a database of the available char- COMMON GROUND acterization techniques and their key features in terms of the type of material they can handle and the characteristics and Pierre Ricou’s impression was that small-scale character- properties that they measure. Such a database may increase ization is a focal point for many different parts of the nanotech- the use of these powerful techniques in areas beyond those nology world. From industry’s perspective, there is a need to for which they were developed. characterize and understand the properties of materials to cre- 53
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54 CHALLENGES IN CHARACTERIZING SMALL PARTICLES ate complex materials that can meet a wide range of demands. tion to the biomedical application phase. NIBIB also offers From an environmental scientist’s perspective, there is a need fellowships that are designed to create time for mid-career to characterize materials to understand what happens to those researchers in the physical or quantitative sciences to develop materials when they enter the world outside of the laboratory projects in the life sciences. or factory. Although each group is tackling different issues, Conroy said that all of the other NIH institutes have simi- they are united by a need to characterize the properties and lar initiatives, and NIBIB also supports Small Business Inno- behaviors of complex materials in complex environments. vation Research (SBIR) grants in the area of bioengineering Ricou was also impressed by the wide range of tech- in nanotechnology. nologies that are now available for characterizing nanoscale materials. He reiterated the importance of creating a data- OPEN DISCUSSION base of technologies, and he stated that instrument vendors should hear more about the challenges facing those who Characterizing Aggregates—Trading Detail for Utility need to better characterize nanomaterials. He would like to see development of the ability to perform spectroscopy on Jim Litster said he was amazed by what he heard during dynamic systems at the nanoscale to better understand how the workshop about the ability to measure individual small the chemistry of a nanomaterial changes over time, which particles. He added, however, that because the functionality would benefit many aspects of nanocharacterization. of the nanoparticles in use depends very much on the struc- tures in which they are embedded, there is still a need for techniques that are just as powerful at characterizing the state FUNDING OPPORTUNITIES of dispersion or aggregation. Developing the techniques and Richard Conroy said that he came away from the presenta- instrumentation to attack that problem is the logical next step tions with two questions: for the field. Doug Ray agreed that there is not as much capability in • Should we study function first or structure first? the area of concentrated liquids and solids. He asked, “Is it • Should we measure something just because we can? because it is just really hard and the community is not there yet, or is it because we have elected somehow to not focus This second question is particularly important from the in that arena?” He does not know the answer but thinks it is NIH perspective, because many measurements correlate an interesting question to consider. weakly with outcomes, and thus it is not always clear that Mark Barteau added that work in this area might focus on the measurements are useful when considering the research “diagnostic,” meaning that it may not be necessary to know that has gone into them. He added that consideration of the all the details of how nanoparticles behave in a matrix. It question of safety and efficacy is also important, in terms of might be enough now to characterize these complex materials the comparative effectiveness and safety of nanotechnology- according to a certain number of reduced parameters or based products versus bulk materials. “lumped” parameters. He is aware of some movement in Conroy provided a quick overview of some of the fund- that direction, but the emphasis on incredible levels of detail ing opportunities at NIH. Part of NIH’s current mission is and expensive instruments does not match the degree found to bridge the life and physical sciences, and, in that regard, in nanoscale imaging. He wondered, however, if looking at he thought the nanomaterial characterization community more complex systems at lower levels of detail that are still would be interested in a number of initiatives. Most of the diagnostic might be where the field makes the biggest impact. initiatives are funded by NIBIB or the National Institute of Ray added that the atmospheric sciences are starting to move General Medical Sciences (NIGMS), with NIBIB focusing from a more detailed view to one that reduces the amount of more on the clinical side and NIGMS focusing more on basic information and creates useable models. research. One new initiative is aimed at applying technolo- Conroy noted that NIH is interested in where the field gies from the physical sciences to life sciences problems. A is going on this matter. He believes that the relevant ques- significant feature of this initiative, the grant review panel tion relates to how much detail on specific characteristics is includes experts from both NIH and the National Science needed to predict biological outcomes. Ricou agreed with Foundation (NSF), with the latter providing a physical this idea but stressed the importance of understanding these science perspective to the NIH review process. A partner systems in fine detail to know what is important when trying initiative aims to translate ideas from the physical sciences to predict relevant behavior. into the clinical arena. Another NIBIB initiative is the bioengineering research Chemistry and Stability partnership program that encourages investigators to form a partnership between the life and physical sciences to Levi Thompson pointed out that many of the particles translate a concept, technique, or tool from the demonstra- that were discussed at the workshop are semiconductors and
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55 WORKSHOP WRAP-UP SESSION wondered if the properties of those particles are influenced build the measurement tools that the industry has needed by exposure to light. He asked if anybody had performed as it meets its technology goals. Nothing like that exists the requisite studies to determine whether photocatalytic for nanotechnology. He acknowledged that creating such a or photolytic processes are important to particle reactivity. consortium to define what is happening in nanotechnology Satya Kuchibhatia from the Pacific Northwest National would be difficult given the disparate nature of this commu- Laboratory answered that his group has looked at cerium nity. “Perhaps several of these kinds of consortia are needed oxide nanoparticles and found that exposure to light defi- to help shape this field and get people together to talk about nitely influences the transformations happening on the nano- what their needs happen to be,” he suggested. particles. He also explained that how a nanoparticle responds Rhonda Stroud believes that having a focus is great, but to light changes over time and that his group has noticed it does not necessarily have to be on commercial applica- changes between the times when a particle is received from tions alone. As a civil servant, her customer is the American a vendor and when it is studied. Where the particles are public, and she asks herself, “Can I justify working on space manufactured also makes a difference, which is likely due particles to the taxpayer?” She believes that the common to the humidity of the manufacturing location. issue is really quality of life. Everyone is producing infor- Finlayson-Pitts said that the field of atmospheric chemis- mation and products that improve the quality of life. This is try is starting to pay attention to the photochemical properties what air quality, new drug treatments, and astronomy have of nanoparticles. The photochemistry of small particles can in common. They may not all have immediate commercial be quite different from the photochemistry of larger particles, applications, but they can be important to the American primarily because of differences in surface-to-volume ratios. people nonetheless. Therefore, a roadmap should look at As an example, she described differences in the photolysis what the impact of knowledge as well as products will be of nitrate ion that occurs when it is surrounded by a solvent on the average person. shell on a bulk surface compared to when it is at an interface. A participant agreed that the ultimate goal is to serve the “The whole issue of photochemistry at interfaces is certainly people, but, at the end of the day, the commercial aspect is one that is getting increasing attention in the atmospheric important because it is the means to get to that goal. For community,” she said. Thomson added that researchers who example, catalysis is very important for many applications. study catalysis, photocatalysis, and electrocatalysis have Researchers will make useful and environmentally benign been considering these issues for many years, and it might c atalysts from ruthenium or rhodium. However, those be an intersection that can be probed more. materials are expensive, so in poorer countries that same reaction will be carried out without the catalyst and will use excess reagent that gets dumped into waterways because What’s the Focus? pollution control standards are lax. Ultimately, if knowledge One participant commented that while the presentations does not make money or save money, no matter how useful were very informative, there was a lack of focus in terms of it is, people will not use it. an industrial driver, that is, how at the end of the day will Ray replied that while certain sectors, such as energy or this research help to develop new products. pharmaceuticals, are driven by commercial interests, other Kuchibhatia and his colleagues at the Pacific Northwest sectors such as the defense industry are not. He believes that National Laboratory are encouraged that the field is mov- there are sectors where commercial drivers are in place and ing beyond the excitement of getting a good TEM image are appropriate, and there are other sectors where they are to search for details about surface chemistry with an eye not. The nation supports research in areas such as astronomy, on developing nanoparticles with specific properties. The not for an immediate commercial benefit but for quality-of- goal, he said, has gone from seeing structure to combining life issues and the long-term benefits that the research might structure with a desired chemical property. “At the end of the produce. Stroud pointed out that the Department of Defense day, it is the chemistry that is going to make the magic, not does a significant amount of work on the development or the just the structure,” he said. advancement of catalysts and energetic materials where Postek added that a roadmap created by the semi- the driving force is not the immediate bottom line, but the conductor industry years ago has guided the industry since need to protect the American people. the 1980s and has allowed instrument manufacturers to
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