Gallic acid capped Tb³⁺ doped CaF₂ nanoparticles for selective detection of Cr₂O₇²⁻ and MnO₄⁻

Madhukar, Nikita (2018) Gallic acid capped Tb³⁺ doped CaF₂ nanoparticles for selective detection of Cr₂O₇²⁻ and MnO₄⁻. Masters thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

In this work, we have utilizedLn³⁺-doped nanomaterials for the selective detection of both Cr₂O7²⁻ MnO₄⁻ ion in 5uM concentration. This is achievedusinggallic acidcapped Tb³⁺-doped CaF2nanoparticles . These nanoparticles show strong green emission upon UV excitation due to strong energy transfer fromthegallic acid molecules to Tb³⁺. This strong energy transfer is selectively quenched upon the addition of dichromate and permanganate ion leading tothereduction in the green emission intensity. The selective quenching of green emission is attributed to the spectral overlap of the emission of gallic acid with the absorption of the analytes. This limits the overall energy transfer efficiency from gallic acid to Tb³⁺ ions. resulting in the reduction in the intensity of the Tb³⁺ emission. The detection limits (for the 3σ/slope criterion) are 110nM and 35 nM for dichromate and permanganate ions, respectively. The reduction in the emission intensity is found to be very selective which is verified by the addition of other high oxidizing species (I⁻. F⁻, Br⁻, Cl⁻, PO₃²⁻,SO₄²⁻, VO³⁻,WO₄²⁻,IO₃⁻, ClO₄⁻)resulting hardly alters the Tb³⁺ emission intensity. The study clearly implies that the resonance energy transfer (RET) using Tb³⁺-doped nanoparticles can serve as a tool to selectively detect dichromate and permanganate ion simultaneously.

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