Physical Sciences Division
Employing Ions Allows Scientists to Precisely Design Innovative Materials
Invited review article covers basic processes and applications of ion soft-landing
By gently dropping selected molecules onto surfaces, the soft landing technique provides outstanding control for building and studying materials, according to Julia Laskin, Grant Johnson, and Qichi Hu in their recent review article. Enlarge Image
Results: By gently dropping selected molecules onto surfaces, the unassumingly named soft landing technique provides exquisite control for those building and studying materials, according to scientists at Pacific Northwest National Laboratory. Dr. Julia Laskin, Dr. Grant Johnson, and Dr. Qichi Hu reviewed ion soft-landing fundamentals and advances in The Annual Review of Analytical Chemistry, the top journal in analytical chemistry. The authors were invited to write this review because of their expertise in soft-landing research and their extensive work in ion-surface interactions.
"With soft-landing techniques, chemists can control—very precisely—the location, the makeup, and the kinetic energy of the molecules that we deposit," said Laskin, the PNNL physical chemist who led the writing of the review article. "This level of control is very difficult to achieve using other techniques."
Why it matters: When it comes to preparing never-before-seen materials to revolutionize the energy landscape, scientists don't want to rely on expensive, laborious trial-and-error processes. They want control. Using soft-landing techniques, researchers can get the molecules they want and deposit only those molecules on a surface. They avoid the undefined mish-mash of molecules common to other preparation techniques. In addition to energy-related applications, the exceptional purity of the peptides and proteins prepared by ion soft landing have potential uses in biological sensors.
Methods: The article covers both soft landing and reactive landing of ions. In reactive landing techniques, the ionized molecules hit the surface with more force than soft landing and react with the surface forming chemical bonds. Further, the article includes studies from universities, national laboratories, and other institutions. For example, the authors discuss the research being done on the size-dependent reactivity of palladium clusters. At the University of Utah, a team of scientists led by Professor Scott Anderson found that the size of the palladium clusters strongly alters their catalytic activity.
Another example is from Purdue University, where researchers led by Professor Graham Cooks deposited biologically active proteins onto different surfaces. "With soft landing, you end up with an array of exceptionally pure bio-active molecules that have a variety of potential applications" said Johnson, a physical chemist and one of PNNL's first Linus Pauling Distinguished Postdoctoral Fellows.
These are just two of the examples packed into the article. "Staying within the page limit on a topic when you really want to elaborate and bring in more examples—and each example is exciting—was difficult," said Laskin.
What's next? The PNNL team continues to work on studies related to soft landing of molecules for fundamental energy sciences and other applications.
Acknowledgments: This review paper was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, U.S. Department of Energy; PNNL's Laboratory Directed Research and Development Program; and EMSL, a national scientific user facility.
Grant Johnson, Qichi Hu, and Julia Laskin of PNNL wrote the review article.
Reference: Johnson GE, Q Hu, and J Laskin. 2011. "Soft Landing of Complex Molecules on Surfaces." Annual Review of Analytical Chemistry. Volume 4. 83-104.