The transfer of structural mirror asymmetry from chiral molecules to the inorganic phase at solid‐liquid interfaces enabled rapid development of biomimetic chiral nanoparticles. They can be synthesized and assembled following a variety of chemical methods resulting in the broad family of chiral inorganic nanostructures (CNs). Their chemistry attracted large attention due to marked enhancement of circular dichroism and polarization rotation compared to organic molecules and particles, which opened application prospects in sensing, imaging, catalysis, nonlinear optics, electronics, and medicine. New physical, chemical and biological effects involving CNs such as giant optical activity, mechanical force‐assisted modulation of optical activity, photon‐to‐particle chirality transfer and suppression of amyloid toxicity have been observed. Marked strides toward enhancement of optical asymmetry (
Enhancing circular dichroism by chiral hotspots in silicon nanocube dimers
Circular dichroism (CD) spectroscopy, which measures the differential absorption of circularly polarized light with opposite handedness, is an important technique to detect and identify chiral molecules in chemistry, biology and life sciences. However, CD signals are normally very small due to the intrinsically weak chirality of molecules. Here we theoretically investigate the generation of chiral hotspots in silicon nanocube dimers for CD enhancement. Up to 15-fold enhancement of the global optical chirality is obtained in the dimer gap, which boosts the CD signal by one order of magnitude without reducing the dissymmetry factor. This chiral hotspot originates from the simultaneous enhancement of magnetic and electric fields and their proper spatial overlap. Our findings could lead to integrated devices for CD spectroscopy, enantioselective sensing, sorting and synthesis.
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- Award ID(s):
- 1654192
- NSF-PAR ID:
- 10058263
- Date Published:
- Journal Name:
- Nanoscale
- Volume:
- 10
- Issue:
- 18
- ISSN:
- 2040-3364
- Page Range / eLocation ID:
- 8779 to 8786
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Core-resonant circular dichroism (CD) signals are induced by molecular chirality and vanish for achiral molecules and racemic mixtures. The highly localized nature of core excitations makes them ideal probes of local chirality within molecules. Simulations of the circular dichroism spectra of several molecular families illustrate how these signals vary with the electronic coupling to substitution groups, the distance between the X-ray chromophore and the chiral center, geometry, and chemical structure. Clear insight into the molecular structure is obtained through analysis of the X-ray CD spectra.more » « less
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Chiral transition-metal complexes are of interest in many fields ranging from asymmetric catalysis and molecular materials science to optoelectronic applications or fundamental physics including parity violation effects. We present here a combined theoretical and experimental investigation of gas-phase valence-shell photoelectron circular dichroism (PECD) on the challenging open-shell ruthenium( iii )-tris-(acetylacetonato) complex, Ru(acac) 3 . Enantiomerically pure Δ- or Λ-Ru(acac) 3 , characterized by electronic circular dichroism (ECD), were vaporized and adiabatically expanded to produce a supersonic beam and photoionized by circularly-polarized VUV light from the DESIRS beamline at Synchrotron SOLEIL. Photoelectron spectroscopy (PES) and PECD experiments were conducted using a double imaging electron/ion coincidence spectrometer, and compared to density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. The open-shell character of Ru(acac) 3 , which is not taken into account in our DFT approach, is expected to give rise to a wide multiplet structure, which is not resolved in our PES signals but whose presence might be inferred from the additional striking features observed in the PECD curves. Nevertheless, the DFT-based assignment of the electronic bands leads to the characterisation of the ionized orbitals. In line with other recent works, the results confirm that PECD persists independently on the localization and/or on the achiral or chiral nature of the initial orbital, but is rather a probe of the molecular potential as a whole. Overall, the measured PECD signals on Ru(acac) 3 , a system exhibiting D 3 propeller-type chirality, are of similar magnitude compared to those on asymmetric-carbon-based chiral organic molecules which constitute the vast majority of species investigated so far, thus suggesting that PECD is a universal mechanism, inherent to any type of chirality.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c8nr00902c
