Ziling (Ben) Xue
Knoxville, TN 37996-1600
Ph.D., University of California, Los Angeles (1989)
Our research program is centered on three areas: (1) novel reactivities of metal complexes and chemistry in the formation of advanced materials; (2) development of new chemical analyses; (3) neutron scattering to probe magnetic properties of biomimetic complexes. Both fundamental chemistry and applications are studied. These research projects have been funded by the National Science Foundation, National Institutes of Health, Department of Energy, and NASA.
(1) Probing Novel Reactivities of Metal Complexes and Pathways in the Formation of Advanced Materials
Advanced materials are at the heart of the current very-large-scale-integration (VLSI) devices. Recent developments to make metal oxide gate materials have been called "the most significant change...since Intel pioneered the modern...transistor in 1960s." These metal oxide gate materials are prepared by, e.g., reactions of d0 metal amides M(NR2)n with O2.
We have investigated the mechanistic pathways in the formation of the metal oxide thin films and other microelectronic materials. Reactions of d0 metal complexes with O2 are a new area in inorganic chemistry. Intermediate compounds from the reactions of d0 M(NR2)n with O2 have been isolated and characterized.
In collaboration with scientists at Oak Ridge National Laboratory, we have been developing new routes for the preparation of rare-earth aluminates as buffer layers for high-temperature superconductors and layered ferroelectrics of the general formula (Sr,Ba)Bi2(Nb,Ta)2O9. These sol-gel routes have produced epitaxial aluminates on SrTiO3 (100) single crystals and highly oriented thin-films over silver and single-crystal SrTiO3 substrates.
(2) Development of New Chemical Analyses
We are developing new methods to analyze chemical and biological species. Novel methods for the analysis of trace chromium in blood and urine have been a focus of our recent work. Chromium, an essential trace element for mammals, has been used as low-cost dietary supplements and in the treatment of diabetes and its complications. Reliable measures for assessing Cr status in humans are limited, largely because levels of biological chromium are very low (e.g., ca. 3-10 ppb Cr in the blood of mammals) and it is bound to peptides. We have developed a novel approach to analyze low-ppb level Cr in blood. It combines a new pretreatment of biological samples with electrochemical measurements. We are conducting studies to optimize the method and to develop methods to analyze chromium in urine.
We have also been developing optical sensors. These sensors are based on spectroscopic changes of indicators immobilized in sol-gel thin films. Unique techniques for making stable thin film coatings have been developed in our laboratory. Sensors for gaseous species are currently being developed in our lab.
(3) Neutron Scattering to Probe Magnetic Properties of Biomimetic Compounds
Neutron scattering, as X-ray scattering, has been widely used to probe properties of solid. One property of neutrons (that photons do not have) is that they have a spin (1/2). Thus, during neutron diffraction, the spin of the neutrons interacts with the spin of unpaired electrons in the solid, providing a unique tool to probe electron spin density and magnetic properties of the solid. We have used polarized neutron diffraction to study spin density in Fe porphyrin complexes.
Metals such as Fe play important roles in biological systems. Fe-containing hemes that containing unpaired electrons are involved, e.g., in O2 transport (respiration) and catalytic reactions. O2 is paramagnetic, and it is of interest to probe how magnetic interaction between Fe porphyrins and O2 affects their binding. Electron spin distribution in Fe porphyrins has been probed by EPR and NMR. One technique that has not been used in studying magnetic properties of the biological systems is polarized neutron diffraction. This is, however, the only known technique that gives the distribution of spin density in compounds. Polarized neutron diffraction has recently emerged as a powerful tool to probe spin density. In collaboration with scientists with scientists at Institut Laue-Langevin (France), Oak Ridge National Laboratory, and Argonne National laboratory, we have studied low-spin [Fe(TPP)(ImH)2]Cl (TPP = tetraphenylporphyrin) and high-spin [Fe(TPP)(Cl)].
Another method we use is inelastic neutron scattering (INS). It gives energies of the split components of the ground states of the complexes.
Dr. Xue received his B.S. in chemistry from Nanjing University of Pharmacy-Nanjing University in 1982 and his Ph.D. in chemistry from the University of California at Los Angeles in 1989. Following postdoctoral research at Indiana University, he joined the faculty of the University of Tennessee in 1992. He has served on the executive committee of the ACS Division of Inorganic Chemistry.
Preparation of Tungsten Alkyl Alkylidene Alkylidyne Complexes and Kinetic Studies of Their Formation.Morton, L. A.; Chen, S.-J.; Qiu, H.; Xue, Z.-L. J. Am. Chem. Soc. 2007, 129, 7277-7283.
Reaction of Ta(NMe2)5 with O2. Formation of Aminoxy and Unusual (Aminomethyl)-amide Oxo Complexes and Theoretical Studies of the Mechanistic Pathways. Chen, S.-J.; Zhang, X.-H.; Yu, X.; Qiu, H.; Yap, G. P. A.; Guzei, I. A.; Lin, Z.; Wu, Y. D.; Xue, Z.-L. J. Am. Chem. Soc. 2007, 129, 14408-14421.
Preparation and Use of Ta(CD2But)5 to Probe the Formation of (ButCD2)3Ta=CDBut. Kinetic and Mechanistic Studies of the Conversion of Pentaneopentyltantalum to the Archetypical Alkylidene Complex. Abbott, J. K. C.; Li, L. Xue, Z.-L. J. Am. Chem. Soc. 2009, 131, 8246–8251.
Chemical & Engineering News reported this paper in the article “Formation of Famous Tantalum Complex Is Nailed Down,” June 15, 2009, vol. 87, No. 24, p. 28.
Polarized Neutron Diffraction and Its Application to Spin Density Studies. Dougan, B. A.; Xue, Z.-L. Sci. China Chem. 2009, 52, 2083-2095.
Reactivities of d0 Transition Metal Complexes toward Oxygen. Synthetic and Mechanistic Studies. Chen, S.-J.; Zhang, X.-H.; Lin, Z.; Wu, Y.-D.; Xue, Z.-L. Sci. China Chem. 2009, 52, 1723-1733.
Fluorescent Dye-doped Sol-gel Sensor for Highly Sensitive Carbon Dioxide Gas Detection below Atmospheric Concentrations. Dansby-Sparks, R. N.; Jin, J.; Mechery, S. J.; Sampathkumaran, U.; Owen, T. W.; Yu, B. D.; Goswami, K.; Hong, K.; Grant, J.; Xue, Z.-L. Anal. Chem. 2010, 82, 593–600.
Formation of Aminoxy and Oxo Complexes from the Reaction of Nb(NMe2)5 with O2 and the Crystal Structure of Nb(NEt2)5.Chen, S.-J.; Zhang, J.; Yu, X.; Bu, X.; Chen, X.-T.; Xue, Z.-L. Inorg. Chem. 2010, 49, 4017-4022.
Preparation of the Alkyl Complex Ta(=NSiMe3)[N(SiMe3)2](CH2But)2. Preferential Oxygen Insertion in Its Reaction with O2 and a Ligand Exchange in the Alkoxide Ta(=NSiMe3)[N(SiMe3)2](OCH2But)2. Chen, S.-J.; Xue, Z.-L. Organometallics 2010, 29, 5579–5584.
Unexpected Formation of a Trinuclear Complex Containing a Ta(IV)-Ta(IV) Bond in the Reactions of ButN=Ta(NMe2)3 with Silanes. Chen, S.-J.; Li, J.; Dougan, B. A.; Steren, C. A.; Wang, X.; Chen, X.-T.; Lin, Z.; Xue, Z.-L. Chem. Comm. 2011, 47, 8685-8687.
Transition Metal Alkylidene Complexes. Pathways in Their Formation and Tautomerization between Bis-Alkylidenes and Alkyl alkylidynes. Xue, Z.-L.; Morton, L. A. J. Organomet. Chem. 2011, 696, 3924-3934.
Unusual Reaction of a Tungsten Alkylidyne Complex with Water. Formation, Characterization, and Crystal Structures of Oxo Trimers. Dougan, B. A.; Xue, Z.-L. Sci. China Chem. 2011, 54, 1903-1908.
Formation of the Imide [Ta(NMe2)3(μ-NSiMe3)]2 through an Unprecedented α-SiMe3 Abstraction by an Amide Ligand. Sharma, B.; Chen, S.-J.; Abbott, J. K. C.; Chen, X.-T.; Xue, Z.-L. Inorg. Chem. 2012, 51, 25-27.
Flower-like Self-assembly of Gold Nanoparticles for Highly Sensitive Electrochemical Detection of Chromium(VI). Ouyang, R.; Bragg, S. A.; Chambers, J. Q.; Xue, Z.-L. Anal. Chim. Acta 2012, 722, 1–7. The article was chosen as a “Featured Article” on the cover of the journal.
Pretreatment of Whole Blood Using Hydrogen Peroxide and UV Irradiation. Design of the Advanced Oxidation Process. Bragg, S. A.; Armstrong, K. C. Xue, Z.-L. Talanta 2012, 97, 118–123.