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02월 19일 10시 이후 : 초록수정 불가능, 일정확인 및 검색만 가능
제121회 대한화학회 학술발표회, 총회 및 기기전시회 안내
Metal–Organic Framework “Swimmers” with Energy-Efficient Autonomous Motility
2018년 2월 12일 17시 22분 15초
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4월 19일 (목요일) 11:00~12:30
, Bartosz Grzybowski
Department of Chemistry, Ulsan National Institute of Science and Technology, Korea
IBS Center for Soft and Living Matter / Department, Ulsan National Institute of Science and Technology, Korea
Self-motility so called as self-propel-seen in animals, individual cells, and micro-organisms-has inspired the design of various artificial autonomous locomotion systems. General examples are tactic droplets and segmented nanorods powered by photocatalytic decomposition of H2O2. In these days, there are significant research fueled by catalytic reactions, light, electric, and magnetic fields, polymer capsules, exfoliating particles, as well as numerous forms of the so-called camphor boats based on gel, polymer. Camphor boats as a representative example can spread surface-active chemicals onto the interface and moves following surface tension gradients, which, in turn, set up convective Marangoni flows. It can power the boats to perform different types of motion (continuous, oscillatory, or intermittent) and, if many boats are present, can drive formation of dynamic structures, including open-lattice arrays or swarms in which smaller particles assemble behind and follow larger “leaders”. Recent progress in the synthesis of metal–organic framework, MOF, crystals and films of appreciable dimensions (i.e., larger than microscopic crystallites) has prompted interest in these materials also acting as autonomous movers—this idea rests on the assumption that MOFs’ highly ordered porous structures could regulate release of surface-active molecules and thus control the ensuing motion. Pioneering examples of self-propelled MOFs come from the Matsui group, but the diphenylalanine “fuel” used is costly (ca. $500/g from Sigma-Aldrich), and the particle shape is not controlled. Here, we describe a different self-propelled MOF—based on freestanding films of the porphyrin-based porous coordination network PCN-222—that not only uses much less expensive fuels (e.g., benzoic acid, dimethylformamide, diethylformamide, dibutylformamide) but also combines several other interesting attributes: (i) The moving particles cut from large MOF films can have arbitrary shapes, including those that ensure directionality of motion. (ii) The efficiency of motion (in terms of achievable velocities over 200 mm·s–1 and kinetic energies over 50 μJ·g–1) is significantly higher than that in the majority of previously reported gel or MOF motors. (iii) The velocities of the MOF swimmers depend on the microstructure of the film which differs between its two sides. (iv) In later stages of their motion, the MOFs exhibit and can switch between two distinct patterns of motion (continuous vs intermittent). (v) The MOFs can be refueled multiple times. (vi) When multiple particles are present at the interface, they organize into “open” structures that can move collectively and in a time-periodic manner.
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