I. Optical Properties of Carbon Nanotubes II. DOVE Four Wave Mixing Spectroscopy III. 2D IR Correlation Spectroscopy IV. Luminescence of Lanthanide-Doped Nanocrystals

I. Optical Nonlinearity and Structure Relationships of Single-Walled Carbon Nanotubes:

We Synthesize and functionalize soluble single-walled carbon nanotubes (SWNTs) and measure nonlinear optical properties of the SWNTs by using multi-resonant four wave mixing spectroscopy for photonic device applications and optical sensors. This program is currently under the support of Army Research Office (ARO) of DoD. The project is in collaboration with Dr. Pehr Pehrsson at Naval Research Laboratory and Prof. Jie Liu at Duke University. We have found a facile chemical oxidative method to synthesize water-soluble SWNTs and observed that the optical absorption of the SWNTs reversibly responds to pH. The results point out the opportunity for using the SWNTs for pH sensors. This work was published in the Journal of American Chemical Society. More recently, we have observed that water-soluble SWNTs reversibly respond to hydrogen peroxide. So we move into a new direction for development of SWNTs-based optical biosensors which may be used for potential optical nanosensors when they are in combination with nanolasers, nano waveguides and nano optical fibers. Based on molecular recognition, enzyme-modified SWNTs for sensing several important metabolic compounds such as glucose, lactate and cholesterol, and three representative biospecific pair systems including single stranded (ss)-DNA hybridization, biotin/streptavidin and calmodulin/Ca²⁺ are investigated by optical measurements.

Organizer of Applications of Nanotubes and Nanowires Symposium at 2007 MRS Spring Meeting

Chair of Carbon Nanotube Separation Symposium at FACSS

Link to our First Symposium of Carbon Nanotube Separation held in 2003 FACSS

Link to our Second Symposium of Carbon Nanotube Separation held in 2004 FACSS

Link to our Third Symposium of Carbon Nanotube Separation held in 2005 FACSS

Link to our Fourth Symposium of Carbon Nanotube Separation to be held in 2006 FACSS

Organizer of Nanoscience and Nanomaterials Symposia at FACSS

Link to our Nanoscience and Nanomaterials Symposia held in 2004 FACSS

Link to our Nanoscience Symposia held in 2005 FACSS

Link to our Nanoscience Symposia to be held in 2006 FACSS

II. Development of Novel Doubly Vibrationally Enhanced (DOVE) Four Wave Mixing Spectroscopy:

We use DOVE four wave mixing spectroscopy as a powerful analytical tool to measure and identify multisites and multicomponents in complex systems. This research relies on a newly developed analytical methodology-Doubly Vibrationally Enhanced (DOVE) Infrared Four Wave Mixing Spectroscopy. This method is based on nuclear polarization and is analogous to two-dimensional NMR which measures the cross peaks induced by intra- and/or intermolecular interactions. The DOVE methods have the unique capabilities: 1) mode selection, 2) line narrowing, 3) isotope selection, 4) suppression of solvent background. This work is collaboration with Prof. John Wright of UW-Madison.

Link to Articles Highlighting the DOVE Research Work

Link to our Symposium of Coherent 2D Vibrational Spectroscopy held in 2004 FACSS

III. Applications of 2D IR Correlation Spectroscopy for Molecular Interaction Study:

We use 2D infrared correlation spectroscopy to study the fundamental of the near infrared combination bands of organic compounds and biological materials, and to probe molecular interactions among glucose, proteins and novel carbon nanotubes. This project is currently under the support of Research Corporation. The study may lead to a new understanding of these combination bands and provide a new analytical tool for materials identification and molecular interaction study. Traditional FT-IR spectroscopy is a research tool in this research that is particularly suitable for undergraduate students. We have made new progress in a representative biological system composed of glucose, bovine serum albumin and triacetin as well as in the new exciting area of the molecular interaction study of glucose with water-soluble SWNTs. We have identified new features of glucose anomers in near IR by using 2D IR correlation spectroscopy and have probed selected interaction of functionalized SWNTs with the glucose anomers.

Link to our First Symposium of 2D Correlation Spectroscopy held in 2002 FACSS

Link to our Second Symposium of 2D Correlation Spectroscopy held in 2004 FACSS

Link to our Third Symposium of 2D Correlation Spectroscopy to be held in 2006 FACSS

Link to International Symposium on Two-Dimensional Correlation Spectroscopy (2DCOS-II) 21st -23rd August, 2003, Nottingham, UK.

Link to International Symposium on Two-Dimensional Correlation Spectroscopy (2DCOS-III) 12 -14 August, 2005, Delavan, Wisconsin, USA.

IV. Synthesis and Study of Novel Nanostructural Lanthanide Ion-Doped Materials for Optical Data Storage, Signal Processing and Optical Sensors:

Recently, we have synthesized new BaFCl:Eu³⁺ and BaFCl:Eu³⁺, Tb³⁺ crystals whose microstructures have been chemically modified by different defects doping. Persistent spectral hole-burning has been observed at temperature as high as 150 K and multi-holes have been burnt in BaFCl:Eu³⁺. It is anticipated that by controlling the particle size in nanoscale, more intriguing properties of this material will be discovered. Further study by exploring the enhanced band gap fluorescence of individual SWNTs sensitized by lanthanide ions such as Gd³⁺ and Tb³⁺ is under way for optical sensors. The research is in collaboration with Dr. Guokui Liu at Argonne National Laboratory.