报告题目：Size effects of Materials Confined to Nanometer Dimensions including 2D Membranes, Metal Clusters, and Vesicles: Nanocalorimetry and NMR Studies
报告人：Prof. Leslie Allen (University of Illinois，Material Science Dept.)
The nature of materials at nanometer size scales is fascinating and ubiquitous. In nanoscience, size-effects occur in 2D-membranes (single/stacked), lipid-like vesicles (bioscience), magic number cluster formation, glass-transition of polymers, melting point depression (Gibbs-Thompson), odd/even chain length artifacts, nucleation controlled phase-transformations (nanoelectronics), etc. This talk discuses experimental small-size material studies using Nanocalorimetry, AFM, XRD, TEM and more recently NMR. The studies follow the progressive and sometime abrupt changes in material properties during systematic incremental increase from 1-nm to bulk in several systems. Finally, I will discuss the future direction of our research, the development of a “Local Atomic-level Thermodynamic Probe for Nanoscience of 2D Membranes” that combining new synthesis, NMR, Nanocalorimetry, and computational DFT Methods. NMR adds new possibilities for research at a very small scale. While Nanocalorimetry yields average thermodynamic values at extremely small scales (one atomic layer of indium melting), it has no depth perception – it can’t reveal the underlying nature of the material at the atomic level. In contrast, the chemical shift from NMR has the ability to distinguish one atom-type from another. However, it does not yield information of the local or composite thermal properties of the material. Combining these two techniques with the modelling constructs made available with DFT computational machinery will potentially develop a new probe for material characterization at the nanometer size domain.
Prof. Leslie Allen received his BS degree in mathematics (University of North Dakota, 1975), MS degree in physics (Clarkson University, New York, 1979), and PhD degree in materials science and engineering (Cornell University, 1990). He worked at University of Illinois. He has authored Over 100 journal papers and 4 patents.
Innovations in Undergraduate and Teaching Teaching: Awarded/rated 10 years - Top 10% Teachersin Engineering (1993-96, 98, 2001, 2003, 2011-2013). Developed undergraduate senior Electronic Materials Laboratory that has been rated in the top 10% of all Engineering classes for 10 years. With over 15 contact-hours a week, the class attracts the best students in the department. Most of them later go to top graduate schools and obtain NSF/DOD scholarships. A new experiment is developed every 2-year, typically coming from a problem in my research that is “simple” enough for them to solve in weeks, but deep enough as to stump us for months.
Development of Instrumentation Infrastructure Research Tools: Nanocalorimetry (NanoDSC) My group developed the most sensitive calorimeter device NanoDSC to date for material science research. In addition to serving on many NSF panel reviews, I have also served NIH review panel specifically to review MEMS based “bio-calorimetry” devices. I have given over 20 invited (National/International) talks on the device and research using NanoDSC for nanoscale materials. My group has been asked (and funded).