Rice scientists, engineers gain new analysis tool

National Science Foundation grant will bring powerful mass spectrometer to university 

The National Science Foundation has awarded $1.7 million to Rice University to acquire an instrument that can see into and analyze materials of any type, from squishy cells to solid rock and everything in between.

The time-of-flight secondary ion mass spectrometer (TOF-SIMS) will be the only one of its kind on the Gulf Coast and will allow scientists and engineers from Rice and other institutions to study the precise chemical compositions and molecular structures of materials in three dimensions.

Rafael Verduzco

“That’s what drove me to apply for this grant,” said Rice chemical engineer Rafael Verduzco, who said the new tool will greatly benefit his own research into sophisticated polymers and their uses. “I wanted to use this technique and I couldn’t find anywhere to do it. So I said, Why don’t we get one in Houston? We should have one here.”

Verduzco, an associate professor of chemical and biomolecular engineering and of materials science and nanoengineering, is the principal investigator on the grant. Co-investigators are Cin-Ty Lee, a professor and chair of the Department of Earth Science; Caroline Masiello, an associate professor of Earth science; and Jun Lou, a professor of materials science and nanoengineering.

The TOF-SIMS, which will reside in the Keith-Wiess Geological Laboratories, uses a pulsed ion beam to remove molecules from the surface of a sample. The molecules are fed through a “flight tube” that determines their mass. The Rice tool will have the capability to separate species that differ in mass by as little as 1/1,000th of an atomic mass unit.

The Rice scientists expect the new tool will provide clues to the history of the Earth, the complex chemistry of the environment and the structure and function of biological systems and will help develop technologies for energy storage. The spectrometer can analyze organic materials and allows researchers to study things like nanoparticle transport and toxicity in biological systems. It will be able to resolve materials less than 50 nanometers wide and profile them to a depth of 10 nanometers.

“What’s unique about this instrument is that it does three things at once,” Verduzco said. “One is mass spectroscopy. It can tell you exactly what elements are in a sample, across the periodic table and even picking up molecular fragments.

“Second, it has high sensitivity, down to parts per billion. If you have a sample with just trace amounts of uranium or some metal, it will be able to pick that out.

“Third, it uses a focused ion beam, so it can look at a 100-nanometer section and tell you what’s in it, rather than having to take a bulk sample and analyze it all at once,” he said. “Now you can map out the composition of your material with nanometer-scale resolution, which is really powerful.”

Verduzco said he is most looking forward to analyzing the thin films made in his Rice lab for solar and other applications.

“The major advantage of photovoltaics is that you just need a thin film to get them to function, but analyzing the composition of that film isn’t easy,” he said. “Microscopy only gives you a vertical average of what’s there. But TOF-SIMS allows us to do really fine depth profiling and get a 3-D map of the material.”

TOF-SIMS works with organic as well as inorganic materials. Because materials are analyzed in a vacuum, live organisms are out, but frozen or freeze-dried cells can be studied, Verduzco said.

He said the instrument should be installed by next summer. It will be managed by Rice’s Shared Equipment Authority and open to researchers across and outside the university, he said.

Verduzco said Rice will host an annual TOF-SIMS user meeting to exchange techniques and results and to draw participants, and will establish a hands-on graduate-level course on using the tool to analyze materials.