UV/Visible Diffusion-Ordered Spectroscopy: A Simultaneous Probe of Molecular Size and Electronic Absorption

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Physical Chemistry

Background:

• Characterizing complex mixtures requires separating components by size and spectral properties.
• Traditional methods often lack the ability to simultaneously probe both size and electronic absorption spectra.

Purpose of the Study:

• To develop a novel spectroscopic technique, UV/vis diffusion-ordered spectroscopy (DOS), for simultaneous size and UV-Vis spectral analysis.
• To enable separation and characterization of individual components within complex mixtures based on diffusion coefficients and absorption spectra.

Main Methods:

• Utilized flow technology to create a concentration step-function in an optical cell.
• Measured time-dependent absorption spectra to determine diffusion coefficients and UV-Vis spectra.
• Constructed a 2D spectrum correlating absorption wavelength with diffusion coefficient (size).

Main Results:

• Successfully demonstrated UV/vis DOS on mixtures of fluorescent dyes, biomolecules, and coffee components (caffeine, chlorogenic acid).
• Achieved separation of UV-Vis spectra for individual species within mixtures, sorted by molecular size.
• Quantified diffusion coefficients and UV-Vis spectra for components at micromolar concentrations.

Conclusions:

• UV/vis DOS is a powerful tool for simultaneous size and spectral characterization of molecules and particles.
• The technique effectively deconvolutes complex mixtures, providing size-resolved UV-Vis spectra.
• Applicable to diverse samples including biomolecules and natural product mixtures.