Lanthanide based resonance energy transfer (LRET) between Ce-doped LaPO₄ nanorods and coumarin 440 dye

Abstract

Here, we demonstrate an efficient lanthanide based resonance energy transfer (LRET) between Ce-doped LaPO₄ nanorods and coumarin 440 dye using steady state and time resolved spectroscopy. Water dispersible stable colloidal Ce-doped LaPO₄ nanorods are synthesized via a facile aqueous route using a capping reagent 6-amino hexanoic acid (AHA). XRD and TEM analysis confirm the formation of uniform and discrete Ce-doped LaPO₄ nanorods, having a tetragonal phase. FTIR analysis confirms that the surfaces of Ce-doped LaPO₄ nanorods are functionalized with AHA. From zeta potential analysis, it is confirmed that the positively charged nanorods are attached to the negatively charged dye molecules electrostatically. Analysis suggests that both dynamic (1.04 × 10⁴ M^-1) and static quenching (3.3 × 10² M^-1) processes occur in this assembled system. The prepared nanorods show an emission quantum yield of 10.2% and a long fluorescence lifetime (24.9 ns). The spectral overlap of the Ce³⁺ emission with the absorption of coumarin 440 dye molecules enables an efficient energy transfer from Ce-doped LaPO₄ nanorods to coumarin 440 dye. The values of the overlap integral and Förster radius are found to be 2.028 × 10¹⁴ M^-1 cm^-1 nm⁴ and 27.02 Å, respectively. The PL quenching and the shortening of the decay time of the donor (Ce-doped LaPO₄ nanorods) confirm the energy transfer (24%) from the nanorods to the dye. Such energy transfer between LaPO₄:Ce nanorods and C-440 dye could pave the way for designing new optical materials for potential applications.