Dual H-O Bond Relaxation Reveals Hydration-Aggregation Dynamics of PFAS at Aqueous Interfaces: Many-Body...

Area of Science:

• Environmental Chemistry
• Physical Chemistry
• Materials Science

Background:

• Understanding per- and polyfluoroalkyl substances (PFAS) interactions with water is vital for effective removal strategies.
• The dynamic evolution of interfacial states during PFAS hydration and aggregation is not well understood.

Purpose of the Study:

• Investigate how varying concentrations of specific PFAS modulate H─O bond relaxation.
• Establish a quantitative descriptor for differentiating PFAS hydration and clustering.

Main Methods:

• Utilized perturbative resolved spectrometric refinements to analyze H─O bond relaxation.
• Employed molecular dynamics simulations to complement spectral data.
• Quantified the elongated-to-contracted bond ratio (R_e/c) as a descriptor.

Main Results:

• Identified two distinct modes of H─O bond relaxation: contraction via dipolar polarization and elongation via fluoroalkyl-water repulsion (F:⇔:O).
• Demonstrated that the populations of these two modes vary with PFAS species and concentrations.
• Showed that solute clustering enhances polarization and diminishes F:⇔:O interaction, reducing the R_e/c ratio.

Conclusions:

• The R_e/c ratio serves as a quantitative descriptor for differentiating PFAS hydration and clustering.
• Findings advance the understanding of PFAS-water interactions at the molecular level.
• Established a spectroscopic framework for resolving the structural dynamics of fluorinated compounds.