Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA.
Science. 2018 Jan 19;359(6373):309-314. doi: 10.1126/science.aao7172.
Chiral inorganic nanostructures have high circular dichroism, but real-time control of their optical activity has so far been achieved only by irreversible chemical changes. Field modulation is a far more desirable path to chiroptical devices. We hypothesized that magnetic field modulation can be attained for chiral nanostructures with large contributions of the magnetic transition dipole moments to polarization rotation. We found that dispersions and gels of paramagnetic CoO nanoparticles with chiral distortions of the crystal lattices exhibited chiroptical activity in the visible range that was 10 times as strong as that of nonparamagnetic nanoparticles of comparable size. Transparency of the nanoparticle gels to circularly polarized light beams in the ultraviolet range was reversibly modulated by magnetic fields. These phenomena were also observed for other nanoscale metal oxides with lattice distortions from imprinted amino acids and other chiral ligands. The large family of chiral ceramic nanostructures and gels can be pivotal for new technologies and knowledge at the nexus of chirality and magnetism.
手性无机纳米结构具有高圆二色性，但迄今为止，其光学活性只能通过不可逆的化学变化来实现。场调制是手性器件更理想的途径。我们假设，对于磁跃迁偶极子对极化旋转有较大贡献的手性纳米结构，可以实现磁场调制。我们发现，具有手性晶格畸变的顺磁 CoO 纳米颗粒的分散体和凝胶在可见光范围内表现出的圆二色活性比具有相同尺寸的非顺磁纳米颗粒强 10 倍。纳米颗粒凝胶对紫外圆偏振光束的透明度可以通过磁场可逆地调节。这些现象也在其他具有由印迹氨基酸和其他手性配体引起的晶格畸变的纳米尺度金属氧化物中观察到。由手性陶瓷纳米结构和凝胶组成的大型家族在手性和磁性的交叉点上为新技术和知识提供了关键支持。
