PARAFAC Analysis of the Quenching of EEM of Fluorescence of Glutathione Capped CdTe Quantum Dots by Pb(II)

Glutathione capped CdTe quantum dots (QD) were synthesised using a simple experimental procedure and two samples were subjected of study (QD(550) and QD(600)). The maximum of the excitation and emission spectra and the emission full width of half maximum of these two QD were: QD(550), 307, 550 and 37 nm; QD(600), 307, 600 and 39 nm. The steady state fluorescence properties of the two QD undergo variation when the pH of the aqueous solution is varied and are characterised by different apparent pKa: QD(550), 5.2 +/- 0.1; QD(600), 6.3 +/- 0.3. The fluorescence intensity of the QD(550) is markedly quenched by the presence of micromolar quantities of Pb(II) ion (Stern-Volmer constant of about 7 x 10(5) M-1). PARAFAC analysis of the excitation emission matrices (EEM) of QD(550) acquired as function of the Pb(II) ion showed that only one linearly independent component describes the quenching of the QD(550) by the Pb(II) ion allowing robust estimation of the excitation and emission spectra and of the quenching profiles.