■ Venue : Applied Engineering Buliding (W1) 1st Floor, Multimedia Seminar Room
■ Host : Prof. Seung-Beom Hong
■ Abstract : Small angle x-ray scattering (SAXS) is an x-ray scattering technique that measures x-ray diffraction or scattering from nanostructured samples without altering samples for enhancing the signal. While it has been considered as a low resolution technique for certain research fields, for example protein shape analysis in solution, it used to provide reliable and conclusive evidence in self-assembly studies although may not be as effective as in molecular crystallography. Like other scattering techniques, its accuracy and applicability are highly depending on quality of samples and performance of instruments. Advanced control over nanoscale chemistries coupled with powerful synchrotron x-ray source provides new opportunities for SAXS, and researchers are taking a full advantage of its power.[1-4] In the first part of my presentation, I will briefly introduce SAXS of the Advanced Photon Source, which is one of the brightest x-ray source, for materials research.
In the second part, I will present some recent understandings of DNA engineered nanoparticle assembly. In the project, we have used DNA as a ligand and grafted the molecules on nanoparticles of which kinds could be geometrically and chemically diverse. The DNA molecules on the particles hybridize with ones on other particles according to the programmed base-paring code, resulting in unique self-assembled structures. We recently proved that the polyelectrolytes can provide not only attractive hybridization interaction but also repulsive interaction that had often been neglected.  It, however, turns out that understanding the repulsive interaction is crucial to rationalize detailed structural features of the DNA-nanoparticle assemblies. Theoretical studies on the interaction potentials will enable us better understanding the phase behaviors of DNA grafted nanoparticles that might be analogous to those of metal alloys or ionic salts.
1. H. Zhang, B. Lee, D. V. Talapin et al., Nature, 542, 328-331.
2. T. Li, A. J. Senesi, and B. Lee et al., Chem. Rev., 2016, 116 (18), pp 11128–11180.
3. M. N. O'Brien, M. R. Jones, B. Lee, C. A. Mirkin, Nature Materials, 2015, 14, 833.
4. S. G. Kwon, B. Lee, E. V. Shevchenko et al., Nature Materials, 2015, 14, 215–223.
5. R. J. Macfarlane, B. Lee, C. A. Mirkin et al., Science, 2011, 334, 6053, 204-208