Interdisciplinary
Research

Faculty Spotlights

Jim Adair

Professor of Materials Science and Engineering
Director, NSF Particulate Materials Center (PMC)
http://www.matse.psu.edu/faculty/adair

Jim Adair likes to say that the basic research he does in his lab and for the PMC can be done in any colloidal chemistry lab - a reference to the level of simplicity he likes to maintain when developing materials and processes for science and industry. "My attitude towards research that's relevant on an industrial scale is that if I can't do a particular experiment using standard colloidal chemistry, I really need to think carefully if I really want to do it. My rule of thumb is, if you can do it with simple chemistry tools, then industry won't have many problems translating our technology from our bench top to their industrial scale."

Layers of diamond crystals grown on Si substrate.

It's hard to believe his claim when you tour his labs and see some of the tools he and his staff use on a daily basis, but the installations are clean and safe and his people are only too happy to show you how easy it is to make a 1 nanometer thick coating using a penlight battery. "I've been working with nanoparticles ever since I started working, except we didn't call them that. Nanoparticles were not the focus in the early 1980s - more often than not it was an inconvenience to run across them because we were concerned about making polycrystalline inorganic materials from powders that might have larger grain sizes on the order of 100 nm to maybe 5,000 nm (5 microns). The first patent I ever got was on zirconia, where it's almost impossible not to make nanoparticles. We're making bulk nanocrystalline zirconia (> 2 mm to 2 cm) right now as well as diamond coatings for semiconductors."

A consistent theme in Adair's research group is the use of the principles of colloid and interfacial chemistry. The Adair lab works in a wide variety of materials systems with the goal of being able to assemble particles into components that can be used in devices, whether structural, optical, or electronic. Spherical particles pose problems in that they do not pack well and are difficult to manipulate, so a focus has been on developing other shapes that are easier to work with. The lab has had a lot of success in making anisotropic particles (not the same in all 3 dimensions), or nanoplatelets, such as disk-shaped or tabular particles (2-6 nm thick x 100-200 nm across). Nano-sized, flat platelets make it possible to achieve very thin layers with good surface coverage. For example, nanoplatelets lie flat like a stack of papers when they settle, making them good particles for coating applications. It also makes them ideal for manufacturing items like capacitors or varistors, which require multiple layers.

Sample "designer" particles:
alpha-alumina oxide particles,
macroscopic particles that are
the most widely used ceramic;
silver/palladium nanoplatelets;
and cadmium/sulphur nanoplatelets.

A fascinating thing about anisotropic particles is that they have optical properties that depend on the orientation and shape of the particle - the index of refraction is a function of orientation within the nanoparticle. This makes identification by color possible; semiconductor particles exhibit a blue shift, metals a red shift, and 3 nm silver particles in suspension are yellow or orange, not black as one might expect. The color doesn't depend on whether the nanoparticles are aggregated or dispersed in solution.

One of the real breakthroughs in the last year involved nanoparticle dispersion in liquids (water, ethanol, and others). Usually, particles in liquids clump, or agglomerate - but agglomeration is only useful in a limited number of applications. To make components for devices, greater control of particle attributes for different types of processing (such as electroding) is necessary. Their work in colloidal processing and synthesis is all about avoiding clumping, so that colloids are reduced to their primary particles, which are very well dispersed, usually through combining chemical synthesis with mechanical processing methods. As Jim would say, "its all colloid chemistry."

Projects

One of the Adair group projects is on chemical synthesis to create nanoparticle powders that provide huge surface area per gram of material. They have created special materials with 1,200 square meters of surface area per gram - among the highest ever synthesized (for example, cement has 0.1 square meter of surface area per gram, and many particles have a relatively low surface area of between 1 to 10 square meters of surface area per gram). They've made silica nanoplatelets with a microporosity of about 6 Angstroms (0.6 nm) with 50% porosity - a purely serendipitous discovery! It's a sponge-like, inside-out particle - instead of the surface area being on the outside, a lot of it is on the inside. Because it's also a high-temperature material, it's expected to be useful in applications for fuel cells and catalytic support.

Diamond diode Credit: Adair group.

Another project being developed with a research team composed of Sarah Rouse (graduate assistant in MatSE), Will White (professor in Geosciences and a vibrational spectroscopy expert), and Christopher Siedlecki (a biomedical engineer in the Biomedical Engineering Institute in the College of Medicine) involves a nanocomposite particle drug delivery system. Surface functionalized particles target specific cells in the body and can be customized as harvester (medical diagnostics), seeker (medical imaging), boomer (drug release and therapy), or hunter-killer particles (bacterial, viral, and foreign body binding with cell death). Drugs can be delivered in tablets or suspension and unbound particles are excreted normally. These particles are fluorescent and can be made with controllable timed drug release. All constituent materials are already FDA approved.

Fine particle science is all about organic and inorganic colloids and their characterization, manipulation, and processing. The Adair lab has had to develop special characterization and processing techniques including: measurement using interference patterns, particle charge, and colors of highly refractive materials for determining particle thickness (another simple method for industry); laying down layers of colloidal diamond particles and manipulating the surface so they stick without etching, growing one layer after another; photolithography to create patterns for coatings; evaluation of flow phenomenon of bacterial kidney stones created by aggregate calcium oxalate and calcium phosphate..."Colloids are everywhere," says Jim.

From a poster on the Adair et al Ag/SiO platelet patent, a 20 nm particle with a 3 nm silver core ("tadpole" particles).

Find out more by visiting the Adair Group and PMC poster display on the second floor of the MRL building and check out the varieties of particles his team has created - from macro to nano - for different applications from food to medical to industrial to military.

Favorite Book

Chemistry of Colloids, English translation ca. 1909, by Zsigmondy (a Hungarian who taught at a German university ca. 1908). The book covers many of the materials currently being worked on in the nanoparticulate field, including the Adair labs. Probably half of the book is dedicated to nanoparticles - although they didn't call them that back then - colloidal sulfur, silica, selenium, salicylic acid, and particle shapes found in kaolin, bacilli, etc. Zsigmondy was ahead of his time as there was no known use for nanoparticles. He also didn't have access to the high-purity chemicals, pH electrodes, or characterization schemes we take for granted in the creation and synthesis of customized nanoparticles.

Biography

Professor Adair received his BS (Chemistry 1975), MS (MatSE 1979), and PhD (MatSE 1981) at the University of Florida where he was also a research associate from 1975-1981. He was a J. William Fulbright Postdoctoral Fellow at the University of Western Australia (1981-82) before a stint at Battelle Columbus Laboratories where he was a member of the research staff. From April 1986 to August 1990 he was on the research staff at the Penn State Materials Research Laboratory as Director of the Consortium on Chemically Bonded Ceramics. From there he went back to the University of Florida where he was an Associate Professor of MatSE (1990-1997). Upon his return to Penn State in 1998 as an Associate Professor of MatSE, he assumed the directorship of the PMC. Elected to Sigma Xi, a research honorary, and a fellow of the American Ceramic Society, Jim Adair also actively participates in numerous research and leadership organizations.