Re-evaluation of the steady-state self-quenching constant of quinine bisulfate from fluorescence measurements in transmission geometry

KRIMER, NICOLAS; MIRENDA, MARTIN

Methods and Applications in Fluorescence

IOP Publishing

Año: 2017

In the present work we show that a recent methodologydeveloped by us to acquire emission spectra and fluorescence quantum yields ofhighly absorbing samples in transmission configuration, constitutes a verysimple and robust alternative to determine self-quenching constants, KSQ.We measured the absorption and the steady-state emission spectra of quininebisulphate, QBS, solutions ranging between 1.5 × 10-5 and 1.5 × 10-1 M. From these data, we calculated the expectedemission spectra, affected by re-absorption, for all QBS concentrations. Forhigher concentrations, the re-absorption in the excitation/detection directionreaches values up to 6% of the total emitted intensity. The KSQof the dye was re-evaluated from the concentration dependence of the quotientsbetween the calculated and the experimental integrated emission spectra. Theobtained value, KSQ = 18.4 ± 0.1 M-1, shows nosignificant differences with those obtained from steady-state and averagelifetimes by another authors, pointing out the diffusional nature of the self-quenchingphenomenon. The present work help clarify some ambiguous aspects concerning thephotophysics of QBS, stressing that re-absorption phenomena must be consideredin QBS concentrated solutions for accuracy measurements.