The main focus area of the research in our laboratory is (i) chemical synthesis of nanoscale hetero-structures of semiconducting and magnetic materials and (ii) real-time laser spectroscopic investigation of the dynamic electronic and magnetic properties of the nanostructures prepared from (i). Ultimately, we would like to obtain fundamental understanding of how the dynamic optical, electronic and magnetic properties in structurally complex nanoscale materials can be controlled by tuning their chemical and structural parameters. The knowledge obtained from these researches lays fundamental background essential in many practical applications, such as designing nanoscale electronic devices and light energy-harvesting materials.
Our research effort on synthetic project is centered on developing simple chemical methods of making complex nanoscale hetero-structures of semiconductors and magnetic materials. In the case of semiconductor materials, we are focusing on applying simple chemical transformation technique utilizing ion exchange in crystalline solid to prepare increasingly more complex hetero-structured nanocrystals. We have recently prepared platinum and palladium chalcogenide nanocrystals of various morphology and hetero-interfaces via controlled cation exchange using cadmium chalcogenide nanocrystals as the starting structure. Such chemical transformation can introduce photocatalytic activity to the original structure or tune the optical bandgap of the material for solar cell applications.
The second area of research we are focusing on is the real-time investigation of dynamic magnetic properties of the magnetic nanostructures using fast time-resolve technique. The ultimate goal of this research is to obtain quantitative understanding of how the energy transfer and dissipation in spin (magnetic) degrees of freedom is correlated with chemical and structural parameters of the magnetic materials in nanometer length scale. This research has a technological relevance in the development of new types of electronic and memory devices based on the control of spins rather than charge of the electrons exploited in conventional electronics.
J. Chen, W.-S. Liao, X. Chen, T. Yang, S. E. Wark, D. H. Son, J. D. Batteas, and P. S. Cremer "Evaporation-Induced Assembly of Quantum dots into nanorings", ACS Nano (2009)
C.-H. Hsia, T.-Y. Chen, D. H. Son, "Size-Dependent Ultrafast Magnetization Dynamics in Iron Oxide (Fe3O4) Nanocrystals". Nano Letters, 2008, 8, 571
T.-Y. Chen, C.-H. Hsia, D. H. Son, "Time-Dependent Elastic Property and lattice Temperature of the Photoexcited Iron Oxide Nanocrystals" J. Phys. Chem. C, 2008, 112, 10125
S. E. Wark, C.-H. Hsia, D. H. Son, "Effects of Ion Solvation and Volume Change of Reaction on the Equilibrium and Morphology in Cation Exchange Reaction of Nanocrystals" J. Am. Chem. Soc., 2008, 130, 9550
T.-Y. Chen, C.-H. Hsia, H. S. Son, D. H. Son, "Non-Condon effect on ligand field transitions by coherent phonon in γ-Fe2O3 nanocrystals" J. Am. Chem. Soc., 2007, 129, 10829