Authors:

Julia Ku

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About Paper:

A theoretical foundation and experimental apparatus is described for a new interface-specific chiral spectroscopy based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG). More than half of the medical drugs that are manufactured and sold today are chiral molecules. Understanding and analyzing the chemical behaviors of enantiomers can help predict how pharmaceutical compounds will affect and interact with molecules in our body. Although they have similar chemical properties, chiral molecules have the inherent property of non-superimposability, which is when the mirror image of a molecule is not identical to its original image. Optical activity in chiral molecules has been studied for decades in isotropic systems. This study analyzes and develops a mathematical framework of naproxen's chirality using circular dichroism (CD) spectroscopy performed for the nonlinear optical processes TPEF and SHG. A sample of naproxen microcrystals is prepared on silica microscope slides by solvent evaporation from a saturated methanol solution. In addition to measuring the difference in right-handed and left-handed circularly polarized light by CD, predicted chiral-specific results from SHG and the intensities emitted from two-photon fluorescence are also recorded. This work builds on previous theoretical and experimental work with a prior SURF student (Camila Strachan) using linear spectroscopy for interface-specific absorbance circular dichroism (in press in J. Phys. Chem). Further research will be on fluorescence optical rotary dispersion (F-ORD), in which a chiral sample is illuminated by an ultraviolet light source to selectively probe and interpret orientated chiral molecules at interfaces.

Source:

Purdue University / 2023

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Co-authors:

Julia Ku