Chemistry and Biochemistry

Zhi Xu

 

Zhi Xu

Professor Xu received his B.S. degree in Chemistry, an M.S. degree in Electrical Engineering from Tsinghua University, Beijing, China, and his Ph.D. in Chemistry from the University of Pittsburgh. He held a postdoctoral position at the University of Illinois, Urbana, prior to joining the UM-St. Louis faculty in 1994.

zhixu@umsl.edu
Office: N206
Phone: (314) 516-5328
Fax: (314) 526-5342

Research Interests

Development of new optical analytical instrumentation, investigation of new photonic materials, and study of solid-liquid interfacial chemistry are three major research areas in our group.

Development of New Optical Analytical Instrumentation. Our basic research in optical spectroscopy has led to the invention of a new spectroscopic technology. The new technology has the potential to increase the sensitivity of most commonly used optical analytical instruments 100 to 1000 fold over that of state-of-the-art commercial instruments. Our current research is focused on the implementation of the new technology to a wide range of instrumentations including UV-Vis Spectrophotometry, Infrared (IR) Spectrophotometry, High Performance Liquid Chromatography (HPLC), Atomic Absorption (AA), Inductively Coupled Plasma Atomic Emission (ICP-AE), and Circular Dichroism (CD). This research could dramatically improve both qualitative and quantitative analytical capability in a broad range of chemical, biological, medical and other applications. Analyses from life science research to clinical diagnoses and from environmental analyses to forensic investigations will be favorably impacted. In healthcare, for example, the amount of blood or body fluid need for clinic analyses could be reduced to less than 1% of what is need today, and diseases could be diagnosed much earlier and with better accuracy. In drug discovery, the time needed for identifying an efficient synthetic route could be significantly reduced. This could lead to the development of better and more economic medicine for decease treatment and prevention. In environmental protection, most chemical analyses can be carried out with unprecedented speed and accuracy, which could help to create a clearer living environment.

New Photonic Materials. The research is aimed at developing new photonic materials that have applications in optical data storage, nonlinear optical conversion, and two-photon absorption. In particular, we are interested in the information storage by individual molecules and the structure-function relationship that governs the two-photon absorption (TPA) behavior of organic molecules. Our earlier study has demonstrated the feasibility of information storage by individual molecules in liquid phase based on intermolecular charge transfer. Our current investigation in this direction is to translate our successful model system from liquid phase into solid phase. In the research front of two-photon absorption, we have developed new transition theory based on quantum mechanics. A series of new molecular structures have been developed according to the prediction of the new theory. These new molecules have increased the TPA cross-section over 2000 times in comparison to traditional organic molecules with long electron conjugations. The extremely large TPA cross-sections of these new molecules make it possible to develop new optical media/devices for three-dimension optical storage, up-conversion of light to create blue and UV lasers, and the protection of human eyes and optical sensors from the permanent damage by lasers.

Chemistry at Solid-Liquid Interfaces. The goal is to achieve molecular level understanding of phenomena such as adsorption, molecular interaction, and chemical reactions occurring in solid-liquid interfacial systems of fundamental and industrial importance. Some of the industrial application areas for such studies are separation science, surfactants, electrochemistry, catalysis, and corrosion inhibition. By using a novel technique - nonlinear optical molecular probing (NOMP) method, we are able to extract the information of chemical interactions and chemical reactions in an interfacial region within 20 - 50 Å from the solid surface. This has created new research opportunities to understand the actual separation processes in HPLC and electrophoresis, and to develop new stationary phases that are highly selective for the separation of large organic and bio-molecules.

Students interested in these research areas will have the opportunity to learn several exciting spectroscopic techniques including second-harmonic generation (SHG), sum-frequency generation (SFG), optical parametric oscillator (OPO), time-gating detection, UV-Vis, FTIR, fluorescent emission, single molecule detection, multi-photon absorption and emission.

Selected Publications

Z.  Xu, “Optical Device Components,” 200880116752.7, Chinese Patent issued to The Curators of The University of Missouri, May 23, 2012.

 D. W. Larsen and Z. Xu, "Light Scattering Detector," U.S. 8,040,509, U.S. Patent issued to The Curators of the University of Missouri, October 18, 2011.

"Optical Device Components"' Z. Xu and R. Rosenthal, US 7,961,305 US Patent issued to the Curators of the University of Missouri, June 14, 2011.

"Optical Device Components"' Z. Xu, US 7,961,304 US Patent issued to the Curators of the University of Missouri, June 14, 2011.

"Noise Cancellation in Fourier Transfrom Spectophotometry", D. W. Larsen and Z. Xu, US 7,903,252, US Patent issued to the Curators of the University of Missouri, Mar 8 , 2011.

"Optical Device Components"' Z. Xu, US 7,809,418 US Patent issued to the Curators of the University of Missouri, Oct 2, 2010.

"Focused droplet nebulizer for evaporative light scattering detector," D.W. Larsen and Z. Xu, U.S. 7,760,355 US patent issued to the Curators of the University of Missouri, July 20, 2010.

"Ultrasensitive Spectrophotometer", D. W. Larsen and Z. Xu, ZL03815363.7, Chinese Patent isued to the Curators of the University of Missouri, Feb. 18, 2009

"Light Scattering Detector," D.W. Larsen and Z. Xu, U.S. 7,460,234, patent issued to the Curators of the University of Missouri, Dec. 2, 2008.

"Ultrasensitive Spectrophotometer", D. W. Larsen and Z. Xu, US 7,262,844, US Patent isued to the Curators of the University of Missouri, Aug 28, 2007.

"Facile synthesis of two-photon absorbing polymers through radical copolymerization," X. Bi, Z. Wu, and Z. Xu, eXPRESS Polymer Letters, 2007, 1, 482-487.

"Light Scattering Detector", D. W. Larsen and Z. Xu, US 7,268,881, patent issued to The Curators of The University of Missouri, September 11, 2007.

"Development of Ultra-Low-Noise Spectrophotometry for Analytical Applications", Z. Xu and D. W. Larsen, Analytical Chemistry, 2005, 77, 6463.

"Synthesis of Triphenylamine-Cored Dendritic Two-Photon Absorbing Chromophores", P. Wei, X. Bi, Z. Wu, and Z. Xu, Organic Letters, 2005, 7, 3199-3202.

"Optical and Chemical Properties of Polythiophene Films Produced via Surface Polymerization by Ion -Assisted Deposition", Y. Choi, S. Tepavcevic, Z. Xu, and L. Hanley, Chemistry of Materials, 2004, 16, 1924-1931.