Question

Quetiapine fumarate (QTF) is an antipsychotic often used to treat both chronic and intermittent psychotic disorders. 1(a) QTF has been proposed to act as a fluorescence quencher for certain materials. 1(a) Show, by graphical means, that the data for the fluorescence quenching of a semiconductor nanoparticle with a fluorescence lifetime of 35.6 ns) by QTF are consistent with the Stern-Volmer equation. Also determine the rate constant for fluorescence quenching by QTE. [QTF] /uM Fluorescence intensity (arb. units) 3312 3154 3087 2880 2697 2240 1504 50 100 200 500

Answer 1

Fluorescence Quenching Experiments: The rates of quenching (kq) can be determined by using Stern-Volmer kinetics by the equation: 10/1 = 1+ kato[quencher] .......................) Where, Io = the fluorescence intensity without the quencher. I = the intensity with the quencher. To is the lifetime of the semiconductor nanoparticle. To = 35.6 ns = 35.6 x 10's quencher = QTF The data given is as under; lo/1 - 1 conc intensity 3312 lo/1 1 o 3154 1.050095 0.050095 (lo/l - 1) Slope = 0.00241 100 200 500 3087 2880 2697 2240 1504 1.072886 1.15 1.228031 1.478571 2.202128 0.072886 0.15 0.228031 0.478571 1.202128 o 500 100 200 300 400 Concentration of Quencher (UM) The linear correlation is obtained by plotting of (10/ -1) vs concentration of QTF. This indicates that the given data are consistent with the Stern-Volmer equation. Slope = kato..............................ii) kq = slope / To ............ iii) = 0.00241/35.6 x 10-9 = 6.76 x 104 um sol Thus, the rate constant for fluorescence quenching by QTF is 6.76 x 104 uM's-1