Measurement of Chiral Molecular Parameters Based on a Combination of Surface Plasmon Resonance and Weak Value Amplification

Abstract

A novel combination of surface plasmon resonance (SPR) and weak value amplification (WVA) is employed to measure the optical rotation angle and refractive index of chiral enantiomers such as sugars and amino acids. An extremely low optical rotation change (2.73 × 10 −4 rad) is readily measurable, with a resolution of 6.75 × 10 −7 rad, 1 order of magnitude higher than that obtained using weak value amplification with intensity modulation, and a refractive index change of 1.13 × 10 −6 RIU is also detected, with a resolution of 1.99 × 10 −9 RIU, a nearly 1order-of-magnitude increase in sensitivity over weak measurement based on a Mach−Zehnder interferometer. The optical activity and refractive index changes of chiral molecules are determined in real time by measurements of the output light intensity variation, whereby the absolute configuration of the chiral molecule is identified through the relation between intensity and molecular orientation. The SPR−WVA combination sensing scheme fills the gap of capability for detecting the optical activity of a molecular solution, which has not been possible with conventional SPR alone.

Enantioseparation/Recognition based on nano techniques/materials

“…SPR combined with weak value amplification (WVA) has recently been demonstrated in intensity detection of the refractive index of an optically inactive molecular solution, achieving a resolution several orders of magnitude higher than traditional SPR sensors [313]. The useful signal was amplified by several orders of magnitude by selecting appropriate pre‐selected and post‐selected states in a quantum‐mechanical measurement process, while technical noise was suppressed.…”

“…The useful signal was amplified by several orders of magnitude by selecting appropriate pre-selected and post-selected states in a quantum-mechanical measurement process, while technical noise was suppressed. Xu et al proposed and demonstrated a novel approach for sensing chiral molecular parameters in glucose, fructose, L-proline, and D-proline solutions by combining the SPR sensing principle with WVA and an associated intensity-modulated mechanism [313]. They used (1) a linearly polarized light beam as the light source to distinguish the chiral molecules, with the optical rotation angle corresponding to the concentration of the chiral molecular solution determined; and (2) an elliptically polarized Gaussian beam as the light source to detect the chiral molecules, with the refractive index corresponding to the concentration of the chiral molecular solution.…”

High-Resolution Determination of Kinetic Parameters of Sucrose Hydrolysis Based on Weak Measurement

“…Generally, the kinetic parameters of sucrose hydrolysis are determined by monitoring the optical rotation angle using a polarimeter, with the apparent advantages of real-time and label-free [4]. But the polarimeter requires cumbersome adjustment of polarizers and wave plates during the monitoring process, and its measurement accuracy of the optical rotation angle is less than 10 −3 degree [5], [6]. In order to solve the problem of low measurement accuracy, some methods, such as liquid chromatograph, magnetic resonance imager and Raman spectrometer, have been reported for the determination of kinetic parameters [7]- [10].…”

Polarimetric Measurements of Surface Chirality Based on Linear and Nonlinear Light Scattering

“…From the instrumentation point of view, several efficient methods for the measurement of optical rotatory dispersion spectrum have been reported ( Castiglioni et al, 2011 ; Han et al, 2014 ; Jiang et al, 2017a ; Goldberg and Weissman, 2019 ; Liu et al, 2020 ). Most recently, a novel technique by combining surface plasmon resonance (SPR) and weak value amplification (WVA) was used for high resolution measurements of extremely small optical rotation of chiral molecules in dilute solutions ( Xu et al, 2020 ). In addition to static ORD, several time-resolved ORD experiments have also been demonstrated ( Shapiro et al, 1995 ; Chen et al, 2003 ; Chen et al, 2007 ).…”