TITLE:

NONLINEAR LASER WAVE-MIXING SPECRTOSCOPY FOR PARTS-PER-QUADRILLION-LEVEL DETECTION OF ISOTOPES AND CHEM/BIO AGENTS

DATE:

Friday, February 18th, 2011

TIME:

3:30 PM

LOCATION:

GMCS 214

SPEAKER:

William Tong, Distinguished Professor of Chemistry and Biochemistry, william.tong@sdsu.edu, www.billtong.us

ABSTRACT:

Bill Tong has developed novel nonlinear laser methods for chemical analysis with zeptomole-level (10^-21 mole) or sub-parts-per-quadrillion-level detection sensitivity. These patented laser wave-mixing methods can distinguish not only large biomolecules but also isotopes. His nonlinear laser-based detectors are more compact and less expensive than currently available isotope-capable mass spectrometers. Wave-mixing laser methods yield hyperfine profiles, i.e., atomic fingerprints, and hence, unambiguous isotope information from both stable and radioisotopes. Hence, one could use stable isotopes as biotracers instead of radioactive biotracers. Laser wave mixing offers comparable or better detection sensitivity levels as compared to laser-based fluorescence methods and yet wave mixing can detect fluorescing and non-fluorescing molecules. Hence, biomolecules could be detected in their native form without using tags or labels.

In a typical setup, multiple laser beams are focused and mixed inside a small volume (e.g., a trillionth of a liter) of the chemical of interest to create dynamic laser gratings at the atomic or molecular scale. The resulting nonlinear optical effect produces a strong signal beam that shoots out of the sample. Unlike currently available techniques such as fluorescence methods, these novel laser methods produce a strong coherent laser-like signal beam, and hence, it is easy to detect. Picoliter-level probe volumes allow detection of small samples such as single bio cells and convenient interfacing to chip-based electrophoresis systems, compact sensors, microarrays and microfluidic devices that are suitable for studying mechanisms and dynamics of important chemical and biological processes. These novel laser methods offer improvements in sensitivity and selectivity to levels previously thought impractical. Potential applications include earlier detection of diseases, better design of cleaner drugs, more sensitive detection of pollutants and chemicals both inside the human body and in the environment, remote standoff detection of chem/bio agents, and even authentication of paintings and art objects.

HOST:

Andy Cooksy

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