Fluorescence of Paraquat by Immobilization on Clay: Theory and Experiments

BELLETTI, G. D.; SÁNCHEZ, J. P.; ZANINI, G. P.; ETCHEVERRY, M.; QUAINO, P.

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Año: 2025

1932-7447

Paraquat (PQ) is a widely used herbicide known for its environmental persistence and low susceptibility to photochemical degradation. Despite being nonfluorescent by nature, recent studies have discovered that PQ exhibits fluorescence when adsorbed on bentonite-type clays. This phenomenon is highly attractive due to its potential application in environmental monitoring and remediation efforts. In this study, we investigate the fluorescence behavior of PQ on montmorillonite clay (MMT) using a combination of first-principles calculations and experiments. Our results demonstrate that the insertion of PQ into the MMT structure is energetically favorable, causing minimal alteration inthe clay’s interlayer distance. Additionally, our analysis reveals that PQ adopts a planar geometry within the MMT layers, with restricted inter-ring rotation. By examining the electronic structure of PQ in both the basal and excited states, we gain insight into the fluorescence mechanism of the system, which agrees well with experimental results.