Question

1. The fluorescence intensity Ir of a solution of a plant pigment illuminated by 330 nm radiation was studied as a function of quenching agent concentration (Q): [Q] MLL 0.31 10.18 3.0 10.13 10 10 0.081 5.0 10 In a second series of experiment, the fluorescence lifetimes of the pigment were determined by time-resolved spectroscopy IQ) IMT(ns) 176 45 Using appropriate linear plots and lines of best fit, determine both the quenching rate constant ke and the half-life of the fluorescence.

Answer 1

The plot of ln[Q] versus the fluorescence life-time (t) can be drawn as follows.

Colu 0.24 20 30 40 60 70 80 50 t (ns)

Equation of the line: ln[Q] = -0.02807*t + 2.06893

Compare the above equation with the actual equation, i.e. ln[Q] = -kt + ln[Q]₀

Then The rate constant (k) = 0.02807 (ns)^-1 = 2.807*10⁷ s^-1

Now, the half-life of the fluorescence (t1/2) = ln(2)/k = 24.7 ns