In this report, a reversible control of Fe3O4 saturated magnetization by Li ions is demonstrated. A miniature Li ion battery (LIB) was assembled using a Fe3O4 nanoparticle layer as the active cathode. A stable magnetism modulation is realized by a nondestructive electrochemical process in which the lithium insertion results in a valence change and partial redistribution of Fe cations in the crystal structure. The relation between the discharge voltage and the chemical phases were studied by ex situ X-ray diffraction and magnetic measurement. In a suitable discharge potential range, a reversible control of Fe3O4 saturated magnetization was obtained without structural damage to the magnetic electrode. The experimental results indicate by further optimizing the LIB's performance, a large reversible change in magnetization could be realized at room temperature, suggesting the potential for future practical applications.
Song Zhang,Changping Wang,Hong Chang,Qiang Zhang,Yiyun Cheng
The off-on manipulation of enzyme activity is a challenging task. We report a new strategy for reversible off-on control of enzyme activity by near-infrared light. Enzymes acting on macromolecular substrates are embedded with an ultrasmall platinum nanoparticle and decorated with thermoresponsive copolymers, which exhibit upper critical solution temperature (UCST) behavior. The polymer-enzyme nanohybrids form microscale aggregates in solution below the UCST to prevent macromolecular substrates from approaching the enzymes and thus inhibit the enzyme activity, and they disassemble above the UCST to reactivate the enzyme. Upon near-infrared irradiation, platinum nanoparticles inside the enzymes generate heat through a photothermal effect to cause phase transition of the copolymers. Therefore, we can reversibly switch off and on the activities of three enzymes acting on polysaccharide, protein, and plasmid. The enzyme activities are increased by up to 61-fold after laser irradiation. This study provides a facile and efficient method for off-on control of enzyme activity.
危险品化学品经营许可证（带存储）