Research

We have employed both cw and pulsed EPR techniques to study the structure and dynamics of paramagnetic species: reactive intermediates, such as free radicals, photo-induced paramagnetism, such as photo-excited triplet state, or stable complexes, such as transition metal or rare earth ions. Below are two areas of our current research.

Applications of zero-field (ZF) EPR spectroscopy. Recently, we developed a field and frequency agile pulsed EPR spectrometer to measure the properties and the dynamics of photo-excited triplet states of organic molecules in ZF and low magnetic field. Conventional wisdom predicts the first-order hyperfine interaction (HFI) between electron and nuclear spin is zero in ZF because the magnetic moment is zero in ZF. We have demonstrated that the HFI can be observed in ZF during the pulsed EPR free-induction decay detection period for the photo-excited triplet state of organic molecules after the application of a short microwave pulse. The measurements in ZF and near ZF (0.1 - 1.0 mT) show that organic molecules remember the events that happen shortly before the measurements. The molecular memory and associated selective spin population in the photo-excitation could render organic solids a new class of materials for quantum computing. We have observed drastic changes in spectral profiles when we turn on a magnetic field as small as 0.4 mT by a field jump technique. We believe this is a promising experimental technique to examine a particular interaction, such as hyperfine, quadrupole, or other types of interactions by imposing a selective external field during the free-induction decay.

The free-induction decay experiments can further provide natural line width, spin-spin relaxation, dynamic nuclear polarization, and the phase correlation between triplet sublevels which are not available from other techniques.

Chemistry in the confined space of MCM-41 mesoporous materials (see Fig. 1). We have studied the free radical reactions of C₆₀ (Bucky ball) in aqueous solution by modifying the surface of the mesoporous MCM- 41 solids with a pore diameter of 2 - 3 nm (see Fig. 2). We also studied the catalytic reactions by (VO)²⁺ ions immobilized in the nanochannels of functionalized MCM-41 solids. We could also apply the time resolved EPR techniques to elucidate the reaction pathways of photochemical reactions in nanoreactors. These reactions are isolated in separate channels, which effectively make the concentration much higher and avoid the random attacks between fast-reacting free radical species. Nanoreactors therefore open the possibility of "single molecule chemistry" otherwise accessible only in extreme dilution.

Selected Publications

• T.-S. Lin, "Electron Spin Echo Spectroscopy of Organic Triplets", Chemical Reviews, 84, 1-15 (1984).View pdf.
• R.F. Lin, T.-S. Lin, R. Tilton and A.H. Cross, "Nitric Oxide Localized to Spinal Cords of Mice with Experimental Allergic Encephalomyelitis: An Electron Paramagnetic Resonance Study", J. Experimental Medicine, 178, 643 (1993).View pdf.
• V. Kouskov, D.J. Sloop, S. I. Weissman and T.-S. Lin, "Adiabatic Passage Through an Avoided Crossing", Chem. Phys. Letters, 232, 165-168 (1995).View pdf.
• M. P. Egorov, O. M. Nefedov, T.-S. Lin and P. P. Gaspar, " Germylene and Stannylene Anion-Radicals: Generation and Electronic Structure", Organometallics 14, 1539-1542 (1995).View pdf.
• L. L. Dugan, S. L. Sensi, L. M. T. Canzoniero, S. D. Handran, S. M. Rothman, T.-S. Lin, M. P. Goldberg and D. W. Choi, "Mitochondrial Production of Reactive Oxygen species in Cortical Neurons following Exposure to N-Methyle-D-Aspartate", J. Neuroscience, 15, 6377 - 6388 (1995).View pdf.
• L. L. Dugan, D. M. Turetsky, C. Du, D. Lobner, M. Wheeler, R. Almli, C. K.-F.Shen, T.-Y. Luh, D. W. Choi, and T.-S. Lin, "Carboxyfullernes as Neuroprotective Agents", Proc. Natl. Acad. Sci., 94, 9434 -9439 (1997).View pdf.
• D.J. Sloop, T.-S. Lin, and J.J.H. Ackerman, "Transient Magnetic Resonance without RF Pulses: Fast Field Switching" J. Magnetic Resonance, 139, 60-66 (1999).View pdf.
• J. Woodward, T.-S. Lin, Y. Sakaguchi, and H. Hayashi, "Detection of Transient Intremediates in the Photochemical Reaction of Hydrogen Peroxide with Dimethylsulfoxides by Time-Resolved EPR Techniques", J. Phys. Chem. A 104, 557-561 (2000).View pdf.
• T.C. Yang, D.J. Sloop, S.I. Weissman, and T.-S. Lin, "Zero-Field Magnetic Resonance of the Photo-excited Triplet State of Pentacene at Room Temperature", J. Chem. Phys 113, 11194-11201 (2000).View pdf.
• C.-H. Lee, T.-S. Lin, and C.-Y. Mou, "(VO)2+ Ions Immobilized on Functionalized Surface of Mesoporous Silica and Their Activity Toward the Hydroxylation of Benzene" J. Phys. Chem. B 107, 2543-2551 (2003).View pdf.
• Chia-Hung Lee, She-Tin Wong, Tien-Sung Lin, and Chung-Yuan Mou, "Characterization and Biomimetic Activity of a Hydroxo-Bridged Binuclear Phenanthroline–Cupric Complexes Encapsulated in Mesoporous Silica: Models for Catechol Oxidases" J. Phys. Chem. B. 109, 775-784 (2005).View pdf.
• Aiqin Wang, Jun-Hong Liu, S.D. Lin, Tien-Sung Lin, Chung-Yuan Mou, "A Novel Efficient Au-Ag Alloy Catalyst System: Preparation, Activity and Characterization" J. of Catalysis 233, 186 – 197 (2005).View pdf.
• Chia-Hung Lee, Jun Lang, Chun-Wan Yen, Pei-Chun Shih, Tien-Sung Lin, and Chung-Yuan Mou, "Enhancing Stability and Oxidation Activity of Cytochrome c by Immobilization in the Nanochannels of Mesoporous Aluminosilicates" J. Phys. Chem. B. 109, 12277 -12286 (2005).View pdf.
• Chia-Hung Lee, Tien-Sung Lin, and Chung-Yuan Mou, "Synthesis and Characterization of a Highly Reactive Vanadium Oxide Species Supported on Mesoporous Silica for the Hydroxylation of Benzene", J. Phys. Chem. – C , 111, 3873-3882 (2007). View pdf.
• Tomoaki Yago,Jörg-Ulrich Weidner, Gerhard Link, Tien-Sung Lin, Gerd Kothe, "Quantum oscillations in photo-excited triplet states in an external magnetic field", Chemical Physics Letters, 438, 351- 357 (2007). View pdf.
• Jun Lang, David J. Sloop, and Tien-Sung Lin, "Dynamics of p-terphenyl crystals at the phase transition temperature: A zero-field EPR study of the photo-excited triplet state of pentacene in p-terphenyl crystals", J. Phys. Chem. – A , 111, 4731- 4736 (2007). View pdf.
• Tomoaki Yago, Tien-Sung Lin, Gerhard Link, and Gerd Kothe, "Pulsed Electron Nuclear Double Resonance Studies of the Photo-excited Triplet State of Pentacene in p-Terphenyl Crystals at Room Temperature", J. Chem. Phys., 127, 114503 ( 2007). View pdf.