Photochemically Induced Circular Dichroism of Semiconductor Nanocrystals
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ANOPHOTONICS
Photochemically Induced Circular Dichroism of Semiconductor Nanocrystals1 F. M. Safina, *, V. G. Maslova, A. Y. Dubavika, E. P. Kolesovaa, A. V. Baranova, and A. V. Fedorova a ITMO
University, St. Petersburg, 197101 Russia * e-mail: [email protected]
Received January 18, 2020; revised January 18, 2020; accepted April 20, 2020
Abstract—Here, we report an investigation of optical activity which was photochemically induced by illumination of QRs and DiRs with circularly polarized light; the photo-induced circular dichroism was quantitatively estimated, and it was shown that the photo-induced chemical reaction proceeds selectively, depending on the handedness of circularly polarized light. Keywords: chirality, optical activity, circular dichroism, photoinduced circular dichroism, semiconductor nanocrystals, quantum rods, quantum dot-in-rods DOI: 10.1134/S0030400X20080317
INTRODUCTION Chirality is a fundamental property of the natural world. “Chiral” refers to those objects that cannot be superimposed on their mirror image. Chiral objects exist not only among molecular objects but also among nanocrystals. Chiral nanocrystals are currently being intensively investigated [1–13] and are presumed to have a significant effect on the development of nanotoxicology and nano-bio-technology [1, 2]. In particular, it is expected that chiral nanocrystals will have different biocompatibility compared to their achiral analogs, which will allow such nanocrystals to interact with biosystems using the chiral molecular recognition mechanism. We have reported an investigation of optical activity which was photochemically induced by illumination of quantum dots with circularly polarized light; the photoinduced circular dichroism was quantitatively estimated, and it was shown that the photoinduced chemical reaction proceeds selectively, depending on the handedness of circularly polarized light. We showed that an optically active ensemble of initially non-chiral CdSe/ZnS quantum dots can be obtained as a result of a photochemical reaction caused by circularly polarized light. That work was based on a concept developed by our laboratory which suggests that some nanostructures can be intrinsically chiral due to the presence of chiral defects on its surface or volume. The reason that the initial ensemble of nanocrystals is not chiral is that the 1 The 2nd International School-Conference for young researchers
“Smart Nanosystems for Life,” St. Petersburg, Russia, December 10–13, 2019.
mixture contains an equal amount of L and D enantiomers. In our opinion, the appearance of the CD signal in those experiments is explained by the fact that in the sample different enantiomers of nanocrystals absorb circularly polarized light differently. When the sample is irradiated with left-handed circularly polarized light (L-CPL), the light is absorbed predominantly by one enantiomer present in the ensemble of nanocrystals, and, conversely, it is absorbed by another enantiomer when the sample is illuminated with right-handed circularly pol
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