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Dr. Kimani A. Stancil
Lawrence Berkeley National Laboratory
Wednesday April 9, noon
Thirkield Hall (Physics), room 103
ASSEMBLING SOFT MATTER - SMART MATERIALS AND PHOTONIC POTENTIAL
In examining heteropolymer gels, we are reminded that entropy is reflected by the Gaussian elasticity of an ideal polymer chain. My work highlights that multi-contact adsorption by gels (a viscoelastic
material) combined with a gel's volume phase transition can reveal information about microstructure [1], [2]. Additionally, by using microfabrication techniques, chemistry, and controlled assembly by evaporation, I have made progress in assembling nanorods on 'large' (urn) scales. For dilute concentrations, my colleagues, and I were able to show that a combination of slow solvent evaporation and electric field results in long range ordered vertically aligned cadmium sulfide (CdS) nanorod superlattices [3]. In my study of cadmium selenide
(CdSe) nanorod solutions, I have found that by steadily evaporating dilute solutions, a lyotropic liquid crystalline phase transition can be obtained. I also show using Small Angle X-Ray Scattering (at the Advanced Light Source, LBNL), that patterned substrates order nanorods by flow alignment during evaporation [4].
[1] T. Tanaka et al. Ber Busenges. Phys. Chern., 102 (11), 1998 [2] K. A Stancil, M. S. Feld, M. Kardar, J. Phys. Chern. B; 109(14); 6636 (2005) [3] K. M. Ryan, A Mastroianni, K. A Stancil, H. Liu, A P. Alivisatos Nano Letters 6(7), 1479(2006) [ 4] K. A Stancil, A P. Alivisatos (2007) {in preparation}
Other useful references below. Topics include: 1) CdSe nanorod assembly on a substrate, and 2) biphasic isotropic-nematic phases of CdSe nanorods. L.S. Li, 1. Walda, L. Manna, A Paul Alivisatos Nano Letters
2(6),557 (2002).
L. S. Li, M. Marjanska, G. H.J. Park, A Pines, AP.
Alivisatos 1. Chern. Phys 120(3), 1149 (2004)
Refreshments will be served