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Research Interests

Research Areas: Materials Physics/Biophysics/Optical Spectroscopy

The research in our group mainly focuses on understanding of the Structure-Dynamics-Function relationship in low-dimensional materials, biological materials as well as fundamental chemical processes, using optical spectroscopy and imaging techniques. Current research interests include conjugated polymers and oligomers, nanocrystalline materials, and DNA. Various state-of-the-art temporally (fs) and spatially resolved spectroscopic methods (inclding single nanoparticle spectroscopy and imaging) are being used or under development for these studies.

i). Nanocomposites with enhanced optical properties

We are preparing various nanocompositites containning noble metals and organic materials to study the interactions between metallic nanoparticles and organic molecules. The optical properties of these nanocomposites, such as enhanced fluorescence, two-photon absorption and Raman scattering, are being investigated using various optical spectroscopy and imaging techniques.

ii). Photophysics of conjugated polymers and their applications in biosensing and phototherapy

iii) DNA: DNA-drug interactions and charge transfer processes in DNA

Representative Publications

Representative Publications (click here for a complete list of publications)

1. Ning Tian and Qing-Hua Xu, "Enhanced Two-Photon Excitation Fluorescence by Fluorescence Resonance Energy Transfer Using Conjugated Polymers", Adv. Mater., 2007, DOI: 10.1002/adma.200700654 (Featured in "Advances in Advance").

2. Ning Tian, Yanli Tang, Qing-Hua Xu and Shu Wang, "Single Base Pair Mismatch Detection Using Cationic Conjugated Polymers through Fluorescence Resonance Energy Transfer", Macromol. Rapid Commun., 2007, 28 (6), 729-732.

3. Daming Cheng and Qing-Hua Xu, "Separation Distance Dependent Fluorescence Enhancement of Fluorescein Isothiocyanate by Silver Nanoparticles", Chem. Commun, 2007, No.3, 248-250.

4. Hwang IW, Xu QH, Soci C, Chen BQ, Jen AKY, Moses D, Heeger AJ, "Ultrafast spectroscopic study of photoinduced electron transfer in an oligo(thienylenevinylene): Fullerene composite" Adv. Funct. Mater. 2007, 17 (4), 563-568.

5. Qing-Hua Xu, Shu Wang, A. Mikhailovsky, Guillermo C. Bazan, Daniel Moses and Alan J. Heeger, "Fluorescence Resonance Energy Transfer Gate in DNA Sequence Detection: a Time-Resolved Study", PNAS, 2005(3), 530.

6. Qing-Hua Xu, Brent S. Gaylord, Shu Wang, Guillermo C. Bazan, Daniel Moses and Alan J. Heeger, "Time-resolved energy transfer in DNA sequence detection using water-soluble conjugated polymers: the role of electrostatic and hydrophobic interactions", PNAS, 2004, 101(32), 11634.

7. K. A. Merchant,* Qing-Hua Xu,* David E. Thompson*, and M. D. Fayer, "Frequency Selected Ultrafast Infrared Vibrational Echo Studies of Liquids, Glasses and Proteins," J. Phys. Chem. A 2002, 106(38), 8839.

8. Xu, Q.-H., Ma, Y.-Z. and Fleming, G.R. "Different Real and Imaginary Components of Third-Order Polarization Revealed by Optical Heterodyne Detected Tranient Grating Spectroscopic Studies in Crystal Violet: Model and Experiments." J. Phys. Chem. A. 2002,106(45),10755.