1999-2000 Master Class Playing To Win - Sergiu Schwartz (Violin)

https://spiral.lynn.edu/conservatory_masterclasses/1188/thumbnail.jp

Inverse Solidification Induced by Active Janus Particles

Crystals melt when thermal excitations or the concentration of defects in the lattice is sufficiently high. Upon melting, the crystalline long‐range order vanishes, turning the solid to a fluid. In contrast to this classical scenario of solid melting, here a counter‐intuitive behavior of the occurrence of crystalline long‐range order in an initially disordered matrix is demonstrated. This unusual solidification is demonstrated in a system of passive colloidal particles accommodating chemically active defects—photocatalytic Janus particles. The observed crystallization occurs when the amount of active‐defect‐induced fluctuations (which is the measure of the effective temperature) reaches critical value. The driving mechanism behind this unusual behavior is purely internal and resembles a blast‐induced solidification. Here, the role of “internal micro‐blasts” is played by the photochemical activity of defects residing in the colloidal matrix. The defect‐induced solidification occurs under non‐equilibrium conditions: the resulting solid exists as long as a constant supply of energy in the form of ion flow is provided by the catalytic photochemical reaction at the surface of active Janus particle defects. The findings could be useful for the understanding of the phase transitions of matter under extreme conditions far from thermodynamic equilibrium.Inverse solidification driven by active colloids provides novel insight into the collective effects in mixed colloidal systems. It offers versatile possibilities to address the processes of solidification in various systems out of equilibrium, including the formation of bio‐molecular condensates or biomineralization, transitions from amorphous to polycrystalline state in condensed matter, or synthesis of materials under extreme conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162773/3/adfm202003851.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162773/2/adfm202003851-sup-0001-SuppMat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162773/1/adfm202003851_am.pd

Nitrogen Doping Improves the Immobilization and Catalytic Effects of Co9S8 in Li-S Batteries

Several critical issues, such as the shuttling effect and the sluggish reaction kinetics, exist in the design of high-performance lithium–sulfur (Li-S) batteries. Here, it is reported that nitrogen doping can simultaneously and significantly improve both the immobilization and catalyzation effects of Co9S8 nanoparticles in Li-S batteries. Combining the theoretical calculations with experimental investigations, it is revealed that nitrogen atoms can increase the binding energies between LiPSs and Co9S8, and as well as alleviate the sluggish kinetics of Li-S chemistry in the Li2S6 cathode. The same effects are also observed when adding N-Co9S8 nanoparticles into the commercial Li2S cathode (which has various intrinsic advantages, but unfortunately a high overpotential). A remarkable improvement in the battery performances in both cases is observed. The work brings heteroatom-doped Co9S8 to the attention of designing high-performance Li-S batteries. A fundamental understanding of the inhibition of LiPSs shuttle and the catalytic effect of Li2S in the newly developed system may encourage more effort along this interesting direction. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei