Chirality and chiroptical effects in inorganic nanocrystal systems with plasmon and exciton resonances

Abstract

This paper reviews the recent advances in experiment and theory of the induction of chiroptical effects, primarily circular dichroism (CD), at the plasmonic and excitonic resonances of achiral inorganic nanocrystals (NCs) capped and/or formed with chiral molecules. It also addresses stronger chiroptical effects obtained in intrinsically chiral inorganic nanostructures obtained from growing enantiomeric excess of intrinsically chiral NCs or arranging achiral plasmonic particles in chiral configurations. The accumulated experimental data and theory on various CD induction mechanisms provide an extended set of tools to properly analyze and understand the electromagnetic influence of chiral molecules on inorganic particles and obtain new general insights into the interaction of capping molecules with inorganic NCs. Among the field-induced CD mechanisms developed recently one can name the Coulomb (near-field, dipolar) mechanism for nanostructures much smaller than the wavelength, and for larger nanostructures, the electromagnetic (effective chiral medium), and intrinsically chiral plasmonic mechanisms.

Enantioselective control of lattice and shape chirality in inorganic nanostructures using chiral biomolecules

“…10). This mechanism is somewhat different from the mechanisms leading to CD in molecules 38,39 and also different from the case of metal nanostructures [5][6][7][8] . In metal nanostructures the CD has a plasmonic origin, whereas in Te nanocrystals the CD originates from inter-band exciton transitions as well as scattering of the large dielectric nanonanostructures with chiral shapes.…”

“…Te nanocrystals (5). The following reagents were added in this order: 1 ml TeO 2 solution, followed by 5.5 ml water and dropwise addition of 2.5 ml hydrazine solution.…”

“…The effect commonly measured is circular dichroism (CD), the differential absorption of left and right circularly polarized light by chiral molecules and materials 3 . Unlike organic molecules, where the chiroptical effects are typically small at visible wavelengths, larger inorganic systems (roughly over ten nanometres to several hundreds of nanometres) may show stronger chiroptical effects [4][5][6] . Several mechanisms were suggested for induction of chiroptical phenomena in such systems (both metallic and semiconducting).…”

Aluminum Nanoparticles with Hot Spots for Plasmon‐Induced Circular Dichroism of Chiral Molecules in the UV Spectral Interval

“…To date, such hybrids have been reported by many groups. [3,6] The focus of this paper was the possibility of using aluminum as an UV-plasmonic element. Indeed, we see that Al-NCs can be advantageous for the amplification of CD signals of biomolecules for two reasons: (1) the plasmon resonances in the Al-NCs are close to the UV bands of typical biomolecules and (2) the Al material system can provide us with much larger enhancement factors.…”

“…In the biomolecule-NC assembly, CD spectra typically show modified molecular lines, in addition to including new lines coming from plasmon excitations in the NCs. It was demonstrated in a large number of experiments [3,6,7] that it is possible to observe plasmon-induced CD in the visible spectral interval using NCs made of gold and silver. It is a very interesting possibility, since the original CD signals of important biomolecules (such as proteins and DNA) are typically in the UV spectral region.…”