Large Optical Activity of Gold Nanocluster Enantiomers Induced by a Pair of Optically Active Penicillamines

Abstract

We have succeeded for the first time in preparing a pair of gold nanocluster enantiomers protected by optically active thiols: D- and L-penicillamine (D-Pen and L-Pen). Circular dichroism (CD) spectroscopy confirmed the mirror image relationship between the D-Pen-capped and the L-Pen-capped gold nanoclusters, suggesting that the surface modifier acts as a chiral selector, and that the nanoclusters have well-defined stereostructures as common chiral molecules do. No CD signals could be obtained when the gold nanoclusters were synthesized by using a racemic mixture (rac-Pen). These chiroptical properties were investigated for the three separated fractions of each of the gold nanoclusters (D-Pen-capped, L-Pen-capped, or rac-Pen-capped clusters) by polyacrylamide gel electrophoresis (PAGE). Each fractioned component has the mean diameter of 0.57, 1.18, or 1.75 nm that was determined by a solution-phase small-angle X-ray scattering. With a decrease in the mean cluster diameter, optical activity or anisotropy factors gradually increased. On the basis of the kinetic and the structural considerations, the origins of large optical activity of the gold nanocluster enantiomers are discussed.

Quantifying thiol–gold interactions towards the efficient strength control

“…SAMs that are based on thiol-gold chemistry have been widely employed in the fields of chemistry, physics, molecular biology, pharmaceutical engineering and materials science [1][2][3] . Considerable interests in such systems have increased, owing to their versatile applications, including the fabrication of nanopatterning 4,5 , molecular-scale devices 6,7 , optical materials 8,9 , formulation of biosurfaces 10 and support for cell culture 2,11 . The strength of the gold-sulphur (Au-S) interaction formed between thiols and gold surfaces provides the basis to fabricate robust SAMs for diverse applications.…”

Asymmetric Synthesis of Chiral Bimetallic [Ag28Cu12(SR)24]4– Nanoclusters via Ion Pairing

“…The majority of chiral metal nanoclusters known to date are of types (a) [27][28][29][30][31][32][33][34][35][36] and (b) 16,17,[37][38][39] , with a few belonging to types (c) and (d). [40][41][42] As prepared, many of these chiral metal nanoclusters (types b-d) are racemic mixtures that require separation and purification by various optical resolution methods.…”

Gold Nanoparticles: Synthesis and Applications

“…This finding will be important for various spectroscopic diagnostics and for chiral detection or molecular interaction analysis in biochemistry. 15 ( …”