Helical Gold Nanorods as Chiral Recognition Nanostructures: A Relativistic Density Functional Theory Study

Abstract

We establish helical gold nanorods as the first examples of chiral recognition nanostructures by examining the simple chiral molecule CClHDT adsorbed on the helical Au40 nanorod. We calculate the vibrational circular dichroism (VCD) spectra of the R and S enantiomers of CClHDT adsorbed on the R (or S) enantiomer of Au40 using relativistic density functional theory. The highest adsorption energy is found when the Cl atom of CClHDT binds to a low-coordinated Au atom at the edge of Au40. There are three adsorption modes (essentially identical in energy) corresponding to three orientations of the HDT moiety. We show that, for each adsorption mode, the VCD spectra are distinctly different for the Au40(R)-ClHDT(R) and Au40(R)-CClHDT(S) complexes, and we give a qualitative explanation for this based on the principle of chirality transfer. For comparison with the results for Au40, we calculate the VCD spectra of the R and S enantiomers of CClHDT adsorbed on the achiral Au20 tetrahedral cluster. Again, there are three adsorption modes (essentially identical in energy) corresponding to three orientations of the HDT moiety. However, we show that, for each adsorption mode, the VCD spectra are mirror symmetric but otherwise essentially identical for the Au20-CClHDT(R) and Au20-CClHDT(S) complexes. Thus, the inherent chirality of the helical Au40 nanorod is essential for its chiral recognition functionality.

Gold Nanorods as Visual Sensing Platform for Chiral Recognition with Naked Eyes

“…2 ). The absorbance decrease at 620 nm was due to the aggregation of AuNRs 41 . Furthermore, the mixture solution of AuNRs and L- or D-Gln was centrifuged for 5 min at 1145 × g. As shown in Figure S 2 , some gray precipitate could be observed on the side wall of the tube, which contained D-Gln and AuNRs; no obvious change was found in the tube of L-Gln–AuNRs under the same experimental condition.…”

“…We infer that in this work the chiral recognition is the direct consequence of the intrinsical chirality of AuNRs. Metal surface exhibits the inherent chiral structure 50 , and Au nanoparticles or AuNRs can also exhibit intrinsic chirality 26 , 40 , 41 , 51 – 53 . In 2012, Bürgi group first gave the CD spectrum of Au clusters capped with the achiral ligand, which is the spectroscopic evidence for intrinsic chirality of Au cluster 54 .…”

“…AuNRs have been used as signal elements for colorimetric sensing due to their strong distance-dependent optical property and their high absorptivity 38 , 39 . Moreover, recent studies showed that AuNRs exhibited chirality 40 , 41 . Maybe, AuNRs can act as colorimetric probes for chiral recognition.…”

Emergence of a Low-Energy Peak in the Smoothed Absolute Value Circular Dichroism Spectra of Small Helical Gold Nanorods

“…In a density functional theory (DFT) study, we showed that segments of the (7, 3) single-walled nanotube with a central linear strand, Au 24 , Au 32 , and Au 40 , are stable as free-standing structures and represent atomic cluster analogues of the helical gold wires . That is, they are local minima on the potential energy surface which are robust in the sense that they remain stable when a variety of species are adsorbed on them. , However, they have undercoordinated gold atoms at their ends and, at room temperature, ab initio molecular dynamics calculations indicate that they transform to compact core–shell structures . In this study, we extend these nanorods to include Au 48 and Au 56 and focus on their optical properties.…”

Synthesis and characterization of chiral PEDOT enantiomers bearing chiral moieties in side chains: chiral recognition and its mechanism using electrochemical sensing technology

“…Hence, understanding the mechanism of chiral recognition, and then pursuing the larger gap between two enantiomers and more efficient chiral electrode materials to develop the application of chiral PEDOT is valuable and fascinating. On the other hand, to date, the dominant approaches for chiral recognition are chromatographic methods (including high performance liquid chromatography (HPLC), [38][39][40] gas chromatography (GC), [41][42][43] chiral ligand exchange chromatography (CLEC), 44 and supercritical uid chromatography (SFC) 45,46 ), spectroscopic characterizations (including uorescence detection (FL) 47,48 and vibrational circular dichroism (VCD) 49 ), capillary electrophoresis (CE) 50,51 and molecular imprinting polymer techniques (MIP). 52,53 Even if these techniques are fairly efficient, they are usually time consuming, require costly equipment and need sophisticated and extensive analysis procedures.…”