Nanoscale Structure Formation

Summary

Many processes in nanoscale structure formation are difficult to characterize in-siture. Simulation can help to correlate experimental observation with structure and ultimately function. Since many of these processes occur on timescales that are difficult to sample with standard present-day time-resolved methods, we develop efficient methods to simulate nanoscale structture formation and function on slow timescales.

Branched DNA that forms as solid at 95 C Branched DNA with exceptionally short sticky ends assembles into a new material at temperatures where genomic DNA is fully denatured, if branching geometry and linker rigidity favor crystallization. This was shown on a modeling level and on the level of synthetic material, assembling from dilute aqueous buffer. Singh, A., Tolev, M., Meng, M., Klenin, K., Plietzsch, O., Schilling, C.I., Muller, T., Nieger, M., Bräse, S., Wenzel, W. and Richert, C. (2010) Branched DNA that Forms a Solid at 95 °C, Angewandte Chemie (International ed, (in press). Meng, M., Ahlborn, C., Bauer, M., Plietzsch, O., Soomro, S.A., Singh, A., Muller, T., Wenzel, W., Brase, S. and Richert, C. (2009) Two Base Pair Duplexes Suffice to Build a Novel Material, ChemBioChem, 10, 1335-1339.
Nanotube Sorting We have developed physico-chemical methods to sort single-wall carbon nanotubes (SWNTs) by chiral index using poly(N-decyl-2,7-carbazole) to almost exclusively disperse semiconducting SWNTs with differences of their chiral indices (n-m) > 2 in toluene. The observed selectivity complements perfectly the dispersing features of the fluorene analogue poly(9,9-dialkyl-2,7-fluorene) which disperses semiconducting SWNTs with (n-m) ≤ 2 in toluene. Lemasson, F.A., Strunk, T., Gerstel, P., Hennrich, F., Lebedkin, S., Barner-Kowollik, C., Wenzel, W., Kappes, M.M. and Mayor, M. (2010) Selective dispersion of single walled carbon nanotubes with specific chiral indices by poly(N-decyl-2,7-carbazole) Journal of the American Chemical Society, (in press).
Nanoparticle Catalysis Novel geometrical architectures of hybrid nanoparticle / protein complexes can be generated by chemically synthesizing monodisperse metal nanoparticles in situ in the presence of a stable, stress-related protein. Using a Monte Carlo method we investigate the growth process of the protein embedded nanopartical and its influence on the protein conformation. This work was performed in collaboration with the group of Dr. S. Behrens (ITC, Forschungszentrum Karlsruhe). S. Behrens, A. Heyman, R. Maul, S Essig, S. Steigerwald, A. Quintilla, W. Wenzel, J. Bürck, O. Dgany, O. Shoseyov, "Constrained Synthesis and Organization of Catalytically Active Metal Nanoparticles by Self-Assembled Protein Templates" Adv. Mater. 21, 3515 (2009)
Separation of single-walled carbon nanotubes Quintillá A, Hennrich F, Lebedkin S, Kappes MM, Wenzel W, "Influence of endohedral water on diameter sorting of single-walled carbon nanotubes by density gradient centrifugation." Phys. Chem. Chem. Phys. 12, 902 (2010)