Stark-Enhanced Frenkel Exciton Dissociation in Plant-Derived Quercetin-Al- TiO₂ Hybrids Photocatalysts for Enhanced Environmental Remediation

The development of efficient and sustainable photocatalysts is vital for environmental remediation. Plant-derived flavonoids like quercetin show promise, but their tightly bound Frenkel excitons (~0.6 eV binding energy) hinder charge separation. In this study, we present a theoretical framework that demonstrates how electric-field-induced Stark effects overcome this limitation in quercetin-Al-TiO₂ hybrid photocatalysts. Our quantum mechanical modeling and charge transfer kinetics reveal that moderate electric fields (~0.6 V/Å) reduce exciton binding energies by >80%, achieving over 90% dissociation. Our findings further show that the anisotropic polarizability (α ≈ 62 ų) and strong transition dipole moment (μ ≈ 6 D) of quercetin make it particularly responsive to field modulation, with built-in fields from Al-doping in TiO₂ proving sufficient to achieve these effects without external bias. Our unified Hamiltonian model identifies three field-dependent regimes: weak-field dipole alignment, intermediate-field exciton destabilization, and strong-field wavefunction delocalization, leading to ultrafast charge separation (<0.5 ns). These findings, supported by existing Stark spectroscopy data, establish quercetin-based hybrids as viable and sustainable alternatives to synthetic photocatalysts, offering quantitative design rules for large-scale environmental applications.