Rongchao Jin
Assistant Professor of Chemistry
Research Interests
Jin is developing new methods to synthesize clusters of metal atoms 1–2 nanometers in size. These tiny nanoclusters exhibit fundamentally different properties from their bulkier counterparts, called nanocrystals, which can be up to 100 nanometers in size. The smaller nanoclusters are ideal for use in developing a new generation of catalysts that have extraordinary activity and selectivity.
Jin is also developing complex nanocrystal structures for devices used in electronics and other fields. These hybrid structures, only 10 nanometers in size, contain a mixture of metal and semiconductor nanocrystals such as gold and cadmium selenide.
The Jin group is also using nanocrystals as probes in a new, high-resolution imaging technique to study the nanoscale structure and dynamics of living cell membranes.Professional Background
Ph.D. Chemistry, Northwestern University, Illinois, 2003.
M.S. Catalysis, Chinese Academy of Sciences/Dalian Institute of Chemical Physics, China, 1998.
B.S. Chemical Physics, University of Science and Technology of China, China, 1995.
After earning his doctorate from Northwestern University, where he developed approaches for synthesizing new types of silver/gold nanoparticles and methodologies for detecting DNA using such nanoparticles, Jin was a research associate at the James Franck Institute at the University of Chicago. There he focused on studying the optical properties of silver nanocrystals by “exciting” their structure with very quick laser pulses. Such “ultrafast spectroscopy” uses laser pulses in the femtosecond range, or one laser pulse every quadrillionth of a second. Jin also investigated new methods to study the nanocrystals’ linear and nonlinear optical properties.
What are metal nanoclusters, nanocrystals and hybrid nanocrystals? How do they differ from one another?
Nanoparticles come in many shapes and sizes. Nanocrystals are made of thousands of atoms, but are still less than 100 nanometers in size. Metal nanoclusters, in contrast, are comprised of an exact number of atoms, from several to dozens. Nanoclusters constitute an “embryonic state” of nanocrystals. Nanoclusters can be assembled to form nanocrystals, which in turn can be chemically connected to form hybrid nanocrystal structures. These larger particles are made up of different types of metal and semiconductor nanocrystals. The combined properties of each nanocrystal building block determines the overall properties of the entire structure.
What are the potential applications of these nanoparticles?
Because of their small size, nanoclusters possess a well-defined structure and molecular-like properties. By synthesizing clusters of metal atoms at the atomic scale, we can precisely control their size, shape and composition. We can tailor the nanoclusters at an unprecedented level, imbuing them with unique electronic and surface properties that make them very promising in developing a new generation of catalysts that have extraordinary activity and selectivity for a wide range of industrially important chemistry.
Nanocrystals can be used to construct electronic and optoelectronic devices, optical switches, sensors and photovoltaic devices. By varying the chemical composition of their subunits, researchers can “tune” the properties of nanocrystals to create a range of applications.
How can metal nanocrystals be used to study a living cell membrane?
My research group is using nanocrystals as probes to image, in real time and with high resolution, living cell membranes. Current imaging tools have limited spatial resolution, and spectroscopy techniques have limited temporal resolution when it comes to studying a living, dynamic cell membrane. I’m particularly interested in using nanocrystals as probes to image the distribution and motion of biomolecules in living cell membranes at high-resolution.
High-resolution optical imaging techniques are particularly appealing because they can reveal the nanoscale structure and dynamics of important cell membrane components, such as lipid rafts and membrane proteins. These structures regulate a variety of cell behaviors involved in everyday cellular activity and in human diseases, including bacterial and viral infections, diabetes, Alzheimer’s disease and cancer.
What methods are you using to advance the use of nanoclusters and nanocrystals?
One of our research goals is to develop catalytic applications of metal nanoclusters. We aim to develop catalysts with high selectivity and activity for specific chemical reactions. The traditional method of catalyst preparation typically results in a mixture of differently sized nanoparticles, which does not allow us to correlate a specific nanoparticle’s structure and electronic properties with its catalytic performance. My group is devising new methods to synthesize nanoclusters and nanocrystals with discrete, uniform properties for detailed study. Our new approach for preparing metal nanoparticle catalysts will allow us to achieve a deeper understanding of the mechanism underlying metal nanoparticle catalysis. Using time-dependent spectroscopy, scanning transmission electron microscopy and scanning tunneling microscopy, we will systemically study the cluster growth process to map out which factors regulate cluster size and stability. In addition, we will investigate how the molecular-like electronic properties of metal nanoclusters transition to the collective behaviors of metal nanocrystals and how these changes affect surface chemistry and catalytic properties.
We are also developing new methods to synthesize metal-semiconductor nanocrystals. We will study their properties using ultrafast spectroscopy, which allows us to investigate the behavior of charge carriers in the nanocrystal structures. Ultrafast spectroscopy makes use of femtosecond laser pulses, which will allow us to discover potentially new optical properties of nanocrystals.
Do you plan to collaborate?
Surely I will be seeking collaborators from multiple disciplines. My research program is highly interdisciplinary, and collaboration is a great way to further expand and complement the many things that my group will do. I am truly looking forward to working with all of the highly skilled scientists here at Carnegie Mellon.
Amy Pavlak
September 6, 2006
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