Polarimetric Detection of Enantioselective Adsorption by Chiral Au Nanoparticles — Effects of Temperature, Wavelength and Size

Abstract

R-and S-propylene oxide (PO) have been shown to interact enantiospecifically with the chiral surfaces of Au nanoparticles (NPs) modified with D-or L-cysteine (cys). This enantiospecific interaction has been detected using optical polarimetry measurements made on solutions of the D-or L-cys modified Au (cys/Au) NPs during addition of racemic PO. The selective adsorption of one enantiomer of the PO onto the cys/Au NP surfaces results in a net rotation of light during addition of the racemic PO to the solution. In order to optimize the conditions used for making these measurements and to quantify enantiospecific adsorption onto chiral NPs, this work has measured the effect of temperature, wavelength and Au NP size on optical rotation by solutions containing D-or L-cys/Au NPs and racemic PO. Increasing temperature, decreasing wavelength and decreasing NP size result in larger optical rotations.

Amplified vibrational circular dichroism as a manifestation of the interaction between a water soluble gold nanocluster and cobalt salt

“…4,5 Chiral metal nanoclusters have properties that make them attractive for applications in different domains like enantiomeric separation, enantioselective detection, asymmetric catalysis, pharmaceutical applications and others. [6][7][8][9][10][11] The chirality of metal nanoclusters can be probed by electronic circular dichroism (CD). 12,13 CD spectra are a sensitive probe of the size and structure of the cluster.…”

Enantiomeric separations of chiral pharmaceuticals using chirally modified tetrahexahedral Au nanoparticles

“…In order to chirally modify the THH-Au NPs, their surfaces were coated with D-or L-Cys by mixing 1 mL of the THH-Au NP solution with 4 mL of 0.050 M D-or L-Cys in deionized water [6][7][8] . The solution was sonicated for approximately 30 minutes and then allowed to sit for approximately one hour before making optical rotation measurements.…”

“…Prior work has shown that simple chiral probe molecules such as R-and S-propylene oxide (PO) can be adsorbed enantioselectively onto the surfaces of Au NPs that have been chirally modified with either D-or L-cysteine (Cys) [6][7][8] . The work herein, advances prior accomplishments by using tetrahexahedral (THH, 24-sided) Au NPs exposing well-defined crystal planes and, more importantly, demonstrating that the methodology works with use of a known pharmaceutical, propranolol (PLL).…”

“…There have been a variety of studies of the chiral structures and enantiospecific properties of chiral NPs [3][4][5]10 . In past work, we have developed the use of polarimetry as a tool for detection of the enantiospecific partitioning of chiral probe compounds such as propylene oxide (PO) between a solution phase and the surfaces of chiral Au NPs [6][7][8] . The key observation is that when a racemic mixture of PO is added to a solution containing D-or L-Cys/Au NPs, one observes an increase in the rotation of polarized light as the concentration of racemic PO is increased.…”

Chiral Separation of rac-Propylene Oxide on Penicillamine Coated Gold NPs

“…In these studies, Au-NPs were either spherical or tetrahexahedral (24-sided) in shape. A systematic study has also been performed to understand the effects of temperature and of Au-NP size on enantiospecific adsorption from racemic PO [ 14 ]. These studies made use of optical polarimetry as a means of detecting enantioselective adsorption and used a model developed by us to analyze optical rotation measurements and quantify enantiospecific adsorption equilibrium constants.…”