Oxygen sensing is important in biological studies of many systems. The variation in oxygen content of sapwood trees was measured by del Hierro and coworkers [J. Experimental Biology 53 (2002): 559] by monitoring the luminescence intensity of [Ru(dpp)3] 2 immobilized in a sol-gel that coats the end of an optical fiber implanted into the tree. As the oxygen content of the tree increases, the luminescence from the ruthenium complex is quenched. The quenching of [Ru(dpp)3] 2 by O2 was measured by Bright and coworkers [Applied Spectroscopy 52 (1998): 750] and the following data were obtained:

I0/I 3.6 4.8 7.8 12.2
% O2 12 20 47 100

Construct a Stern-Volmer plot, 4 = a + TokQ(O2), using the data supplied in the table. For (Ru(dpp)3)2+, kF =1.77 * 105 s-1

What is kQ?