Tailoring Optical Characteristics of MoS 2 Nanosheets Exfoliated via Sodium Cholate and Green Tea Extract for Highly Efficient Forster Resonance Energy Transfer

Efficient and green exfoliation of bulk MoS 2 into few-layer nanosheets remains challenging due to its intrinsic hydrophobicity and van der Waals interlayer forces. Although pure water is an ideal solvent for sustainable processing, solubility theory and experiments show that MoS 2 nanostructures rapidly aggregate in aqueous dispersions. To address this issue, surfactants are commonly used during liquid-phase exfoliation (LPE) to stabilize nanosheets, prevent restacking, and im prove colloidal stability. However, many conventional surfactants are toxic and environmentally harmful, limiting their sustainable application. Plant extract based surfactants provide greener alternatives, but their use in LPE is still limited. In this study, MoS 2 nanosheets were exfoliated using sodium cholate (SC) and green tea (GT) extract, and their morphological and optical prop erties were compared to evaluate their potential for Forster resonance energy transfer (FRET) applications. Morphological analysis shows that SC assisted exfoliation produces thinner and smaller nanosheets than those obtained using GT extract. Optical spectra reveal the charac teristic A- and B- excitonic peaks, with a slight blue shift of the A-exciton in SC exfoliated nanosheets. FRET studies with Rhodamine 6G (R6G), Rhodamine B(RhB), and DCM dyes demonstrate efficient energy transfer, with the highest efficiency observed for Rhodamine B due to greater spectral overlap. Time-resolved fluorescence measurements (TRFS) further confirm the FRET process through a significant reduction in the fluorescence lifetime of the donor MoS 2 in the presence of RhB. These results highlight the potential of both SC- and GT-exfoliated MoS 2 nanosheets for sustainable FRET-based photonic and optoelectronic applications.