Investigation on surface interaction between graphene nanobuds and cerium(III) via fluorescence excimer, theoretical, real water sample, and bioimaging studies

Graphene nanobud (GNBs) with an average size of ca. 35–40 nm was utilized to determine the micromolar concentration of Ce³⁺ via chelation-induced fluorescence excimer formation (CHEF) at 475 nm (λ_ex: 328 nm). UV–visible and fluorescence spectroscopy findings on the interaction of GNB with Ce³⁺ confirm the binding stoichiometry as 1:1 (K_a = 4.85 × 10⁻³ and 2.22 × 10⁻² M, respectively) with a LoD ca. 35.0 μM (S/N = 3). The fluorescence decay profile experiment reveals the formation of a ground-state complex, GNB∙Ce³⁺, with an increase in lifetime (τ 7.02 → 27.01 ns), and fluorescence quantum yield (Ф_F 53.6 → 85.0%). Interference of other metal ions (M^1+/2+/3+), the effect of solvent polarity, and the effect of time on the selective determination of Ce³⁺, and reversibility and the stability of GNB∙Ce³⁺ complex were examined. Theoretical calculation (TD-DFT) on the effect of molecular orbital energy levels of GNBs upon interaction with Ce³⁺ was investigated. Detection of Ce³⁺ in relevant water samples enriches the real-world application of GNBs which brings the futuristic application to sense Ce³⁺ in living cell lines. To accentuate, bioimaging of Ce³⁺ in living human breast cancer and human epithelial cells, and cytotoxicity test was successfully demonstrated. Confocal Raman microscopy images and corresponding spectrum articulated the practicability of GNBs in biological systems.