FRET enhanced CeO2:3Tb3+ nanocomposites: A dual approach for photocatalytic dye degradation and agricultural safety

Abstract

This study focuses on synthesizing carbon dots (CDs) integrated CeO₂:3Tb³⁺ nanocomposites (CDs@CeO₂:3Tb³⁺ NCs) for the photocatalytic degradation of MB dye. The NCs are synthesized via a hydrothermal method using coffee grounds as the CD source and characterized using XRD, FTIR, Raman, TEM, XPS, UV-Vis, and photoluminescence (PL) spectroscopy. The CDs@CeO₂:3Tb³⁺ NCs exhibited a dramatic 29.2-fold enhancement in PL intensity compared to the CeO₂:Tb³⁺ nanoparticles alone, attributed to the Förster Resonance Energy Transfer (FRET) mechanism with 75 % efficiency. With an emission peak at 543 nm, the NCs achieved excellent color purity (98 %) and a correlated color temperature (CCT) of 4937 K, making them suitable for cool LED applications. In photocatalytic testing, CDs@CeO₂:3Tb³⁺ NCs demonstrated superior degradation efficiency, achieving 98 % removal of MB dye, outperforming individual CeO₂ and CeO₂:Tb³⁺ components. To assess environmental safety, the treated water is used in a seed germination test with chickpea seeds (Cicer arietinum). The CTC-4 treated groups significantly enhanced seedling growth, with shoot and root lengths of 4.13 ± 1.21 cm and 2.82 ± 1.08 cm, and diameters of 2.72 ± 1.04 mm and 1.67 ± 0.52 mm by Day 7. Root branching reached 20 compared to 17 in the control. Phytotoxicity assessments showed MB dye inhibited germination (PIG 100), while CDs(4 wt%)@CeO₂:3Tb³⁺ showed negligible toxicity (PIG −0.2). The CTC-4 group achieved the highest Vigor Index I (695) and germination index (129.9), with a shorter germination time of 24.0 days. These results demonstrate the potential of CDs(4 wt%)@CeO₂:3Tb³⁺ NCs for mitigating MB dye toxicity and promoting healthy seed growth in dye-contaminated environments. These findings indicate that the CDs@CeO₂:3Tb³⁺ NCs are highly effective, eco-friendly photocatalysts for dye detoxification in wastewater treatment, with potential applications in sustainable agriculture and environmental management. This study establishes the CDs@CeO₂:3Tb³⁺ NCs as a promising solution for industrial dye pollution, offering both environmental and agricultural benefits.