Special Chemical Engineering Seminar
Introduction to Small Angle X-ray Scattering at APS and Its Application for Studies of DNA Colloidal Particle Assembly
X-ray scattering has been a key characterization tool in materials science, especially soft materials that form nanoscale structures. Small angle x-ray scattering (SAXS) is an x-ray scattering technique that measures x-ray diffraction or scattering from the nanostructured samples. While it has been considered as low resolution technique for certain research fields, for example protein shape analysis in solution, it has also provided as conclusive evidences in self-assemblies as in molecular crystallography. Like other scattering techniques, its accuracy and applicability are highly depending on quality of samples, for example whether the nano-structures are homogeneous or not. Advanced control over nanoscale chemistries provides new opportunities in using SAXS in this regard, and researchers are taking a full advantage of its power.[1-3]
For a decade or so, I have been developing SAXS methods and computational tools for studies of colloids and polymers. [1,4,5] They include calculations of scattering from polyhedral particles and development of a powder diffraction theory for colloidal particle assemblies. Using the tools, I have been studying how soft molecules in soft-hard hybrid materials affects the structure formation and thereby properties. In this talk, first, modern development of SAXS techniques including GISAXS, high-energy SAXS, and XPCS available at the Advanced Photon Source (APS) will be introduced with some examples on polymer and colloidal systems. Next, I will discuss about the role of DNAs that are grafted on nanoparticles in determining assembly structures. The polyelectrolytes can provide both attractive and repulsive potentials, where the latter 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 potentials will enable us better understanding the phase behaviors of DNA grafted nanoparticles and analogy with 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