No abstract

The effect of chemical-composition modification on the chiroptical property of chiral organic ammonium cation-containing organic inorganic hybrid perovskite (chiral OIHP) is investigated. Varying the mixing ratio of bromide and iodide anions in Sor R-C 6 H 5 CH 2 (CH 3 )NH 3 ) 2 PbI 4(1−x) Br 4x modifies the band gap of chiral OIHP, leading to a shift of the circular dichroism (CD) signal from 495 to 474 nm. However, it is also found that an abrupt crystalline structure transition occurs, and the CD signal is turned off when iodide-determinant phases are transformed into the bromide-determinant phase. To obtain CD in the wavelength range where the bromide-determinant phase is supposed to exhibit chiroptical activity, that is, <474 nm, Sor R-C 12 H 7 CH 2 (CH 3 )NH 3 with a larger spacer group can be adopted; thus, the CD signal can be further blue-shifted to ∼375 nm. Here, we show that chemical-composition modification of chiral OIHP affects the chiroptical properties of chiral OIHP in two ways: (1) tuning the wavelength of CD by modulating the excitonic band structure and (2) switching the CD on and off by inducing a crystalline-structure change. These properties can be utilized for structural engineering of high-performance chiroptical materials for spin-polarized light-emitting devices and polarization-based optoelectronics.

Mesoscale CdTe helices with near-unity enantiomeric excess offer insight into design rules for chiroptical semiconductor materials.

Photon-to-matter chirality transfer offers both simplicity and universality to chiral synthesis but its efficiency is typically low for organic compounds. New pathways for imposing chiral bias during chemical process are essential for a variety of technologies from medicine to informatics as well as for fundamental science. Strong optical activity of inorganic nanoparticles (NPs) afford photosynthetic routes to chiral superstructures using circularly polarized photons. Plasmonic NPs are especially promising candidates for such reactions but realization and adequate interpretation of light-driven synthesis of chiral nanostructures in light-driven processes was more challenging than for semiconductor NPs. The process also requires unconventional approaches for the quantification of chiral products. Here we show that illumination of nanoscale colloidal dispersions with circularly polarized light induces the formation of chiral nanostructures 10-15 nm in diameter. Despite their seemingly irregular shape, the resulting nanocolloids showed circular dichroism (CD) spectra with opposite polarity after exposure to photons with left-and right circular polarization. The sign and spectral position of the experimental CD peaks of