Lehigh University
Lehigh University


Liu captures prestigious National Science Foundation award

Tianbo Liu

Tianbo Liu, assistant professor of chemistry and one of the newest members of his department, was recently named the recipient of the National Science Foundation CAREER Award. Liu was awarded $451,157 to fund research for a five-year period through 2011.

The highly competitive Faculty Early Career Development (CAREER) Program is among the National Science Foundation's most prestigious awards, which is given in support of the early career-development activities of teacher-scholars who most effectively integrate research and education. Their accomplishments are recognized to encourage the establishment of a firm foundation for a lifetime of integrated contributions to research and education, according to the NSF.

Robert Flowers, professor and chair of the chemistry department, noted that the conferring of the NSF CAREER award on the first submission of a proposal is “uncommon and is recognition of the major impact of Tianbo’s work.”

Liu’s research proposal will focus on what he describes as “a new type of fascinating solution system,” known as hydrophilic macro-ionic solutions. His proposed work is expected to provide new input to related fields, including catalytic, electronic, magnetic and biomedical materials.

“It is our common sense that soluble ions distribute homogeneously in dilute solution, and anions like cations while repel other anions,” says Liu, who created a Lehigh course titled “Complex Solutions and Self-Assembly” to introduce graduate and undergraduate students to progressions in hydrophilic macro-ionic solutions.

“But such well-accepted ideas seem invalid when the ions become larger, that is, macro-ions. In macro-ionic solutions, anions strongly attract with other anions. They have so different behaviors from well-known conventional solution systems such as small ions, surfactants and colloidal suspensions and represent a transitional stage between simple ions and complex biomacromolecules.”

As principal investigator, Liu proposed to study the phenomena of macro-ionic solutions, in which, he says, soluble macro-ions amazingly come together and form a type of new structure: single-layer, hollow, spherical structures coined by Liu as “blackberries,” or what Liu refers to as the “strange aggregates formed by different types of polyoxometalate macro-ions (POMs).”

“What are the detailed structures and properties of these ‘blackberries,’ their size, charge density, inter-macro-ion distance, mechanical strength and permeability to small ions,” he asks. “How do we effectively characterize the new structure by using various physical and chemical techniques? How do these blackberries form? How do the changes of internal and external conditions affect the blackberry formation and their structures? And, more importantly, why do large anions like each other? Can we use ‘blackberries’ as model systems to explore the properties of polyelectrolyte solutions that remain poorly understood?

“The unique inorganic ‘blackberry’ structure has biomembrane nature—soft, robust and permeable to cationic species, which may also find applications, such as controlled drug carriers, nanocontainers or biomimetric materials,” Liu says.

Born in Beijing, China, Liu came to the United States in 1994 after receiving his B.S. in chemistry from Peking University. He was trained as a polymer physical chemist at the State University of New York at Stony Brook, receiving his Ph.D. in 1999. After a two-year post-doctoral fellowship at Stony Brook, Liu went to Brookhaven National Laboratory as assistant and then associate physicist before joining the Lehigh faculty.

During his graduate work in the fields of complex fluids, particularly block copolymer solutions and colloids, Liu used such major techniques as laser light scattering (LLS) and small-angle X-ray scattering (SAXS) techniques. LLS is suitable for studying solutes and suspensions with the sizes between 1-1000 nm. When he started to work at Brookhaven, he wanted to use LLS to characterize the solutions of giant inorganic ions.

“Traditionally,” Liu says, “inorganic chemists do not care about LLS because inorganic molecules/ions are so small. I realized that the size of the giant POM decided to use LLS to characterize these solutions, and obtained promising results.”

Solving the blue water mystery

What Liu found was the answer to a question that had puzzled chemists for several hundred years—the nature of the particles in solutions of molybdenum blue, the so-called “blue water” mystery. LLS showed that various nanometer-sized, highly soluble inorganic anions tend to self-assemble into 100 nm, single-layer, hollow spherical structures containing more than 1,000 single ions in diluted solution. Liu uses the term “blackberry” to describe these unique structures.

Results of his work were published in a series of papers in Nature and The Journal of the American Chemical Society, and have been introduced to public readers via different magazines such as New Scientist, Scientific American, Materials Today and Popular Mechanics.

Liu is now working with the Journal of Chemical Education on considering how to incorporate the recent research progresses into textbooks. He is proposing that “hydrophilic macro-ionic solutions” should become a separated portion in curriculum additional to traditional topics such as ionic solutions, polymer solutions and colloids.

--Linda Harbrecht

Posted on Thursday, May 04, 2006

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