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SOO, Han Sen

Nanyang Assistant Professor

Education: S.B., S.M. (Massachusetts Institute of Technology), Ph.D. (University of California, Berkeley),
Postdoc: Lawrence Berkeley National Laboratory

Research Area: Inorganic Chemistry & Organometallics;
Nanomaterials and Material Chemistry

Phone: (65) 6592 3182

E-mail: Hansen@ntu.edu.sg

Webpage: http://www.ntu.edu.sg/home/hansen/Webpage/Public/Main.htm


Research Interest

My research programme will use an inter-disciplinary approach to develop chemistry solutions to reduce atmospheric greenhouse gas concentrations and to remediate the environment. The major components of this programme include (i) the design and synthesis of new nanomaterials with molecular active sites, (ii) spectroscopic characterisation using time-resolved techniques, and (iii) applications in photocatalysis, photosynthesis, and green chemistry.

Innovated Photosynthesis with Sustainable and Earth-Abundant Nanomaterials

A sustainable future requires the invention of a new carbon cycle, which does not rely on non-renewable fuels, to reduce greenhouse gas levels in the atmosphere on a global scale. Earth-abundant, first row transition metal complexes can be ideal catalysts for light-driven CO2 reduction and water oxidation. However, since the organic supporting ligands of such complexes are often vulnerable to oxidative, light, or thermal damage, anchoring functional transition metal complexes to robust, metal oxide (semi-conducting) scaffolds can improve their recyclability. Substrates such as TiO2, Co3O4, and Cu2O with nanopores or advanced nanoarchitectures have high surface areas with exposed –OH groups that can be used as points of attachment for small molecules.
Building on my prior experience in synthesis and physical organometallic chemistry, we will develop novel organic ligands and photosensitisers, and prepare new first-row transition metal complexes, focusing on Fe, Co, Ni, and Cu. These small molecules will be covalently attached to robust metal oxide nanomaterials to produce a new generation of single active-site heterogeneous catalysts

Spectroscopic and Mechanistic Studies of CO2 Reduction and Water Oxidation in Integrated, Innovated Photosynthetic Units

First row transition metal complexes are often high-spin, paramagnetic compounds that can be fully characterised with a suite of techniques including single crystal X-ray diffraction, mass spectrometry, NMR and EPR spectroscopy. Heterogeneous nanomaterials require additional bulk and surface analytical methods such as FT-IR, FT-Raman, diffuse-reflectance UV-vis, and X-ray photoelectron spectroscopy.
Some of the intermediates in innovated photocatalytic and photosynthetic reactions have very short lifetimes and can only be observed at low temperatures or with time-resolved spectroscopic techniques. Special emphasis will be placed on structure-specific probes such as FT-IR, FT-Raman, and NMR spectroscopy to monitor the kinetics and intermediates of CO2 reduction and O-atom transfer from water. The mechanistic insights drawn from these systematic investigations will aid in the iterative improvement of functional and applied nanomaterials.

Degradation of Environmental Pollutants with Hybrid Nanomaterials

The growing human population has led to rising levels of environmental pollutants. We will explore how the robust heterogeneous materials containing molecular active sites can be applied to the photooxidative decomposition of these pollutants, using O2 or H2O2 as the terminal oxidants. Alternatively, we intend to exploit the pollutants as the ultimate electron donors in an integrated, innovated photosynthetic scheme, with the electrons channeled towards the reduction of CO2 into commodity chemicals and solar fuels.


Selected Representative Publications

  1. Soo, H. S.; Agiral, A.; Bachmeier, A.; Frei, H. “Visible Light-Induced Hole Injection into Rectifying Molecular Wires Anchored on Co3O4 and SiO2 Nanoparticles”, J. Am. Chem. Soc. 2012, 134, 17104.

  2. Soo, H. S.; Macnaughtan, M. L.; Weare, W. W.; Yano, J.; Frei, H. “EXAFS Spectroscopic Analysis of Heterobinuclear TiOMn Charge-Transfer Chromophore in Mesoporous Silica”, J. Phys. Chem. C, 2011, 115, 24893.

  3. Soo, H. S.; Komor, A. C.; Iavarone, A. T.; Chang, C. J. “A Hydrogen-Bond Facilitated Cycle for Oxygen Reduction by an Acid- and Base-Compatible Iron Platform”, Inorg. Chem. 2009, 48, 10024.

  4. Soo, H. S.; Figueroa, J. S.; Cummins, C. C. “A Homoleptic Molybdenum(IV) Enolate Complex: Synthesis, Molecular Structure, and NCN Transfer to Form a Terminal Cyanoimide of Molybdenum(VI)”, J. Am. Chem. Soc. 2004, 126, 11370.

  5. .Soo, H. S.; Diaconescu, P. L.; Cummins, C. C. “A Sterically Demanding Enolate Ligand: Tantalum Ligation and Pyridine Coupling”, Organometallics, 2004, 23, 498.