STUDIES ON THE FLUORESCENCE QUENCHING OF POLYSILANE COPOLYMERS BY CHLOROHYDROCARBONS

The room-temperature solution fluorescence quenching of polysilane cop olymers by chlorohydrocarbons such as CCl4, CHCl3, C2Cl6, and Cl2CHCHC l2 was studied. The existence of dynamic quenching was preliminarily d emonstrated by the experiment of fluorescence lifetime quenching. The fluorescence quenching data were in conformity with the equation: F-0/ F = (1 + K-SV[Q])exp(NV[Q]), where F and F-0 are the fluorescence inte nsity with and without the addition of quencher, K-SV is the Stern-Vol mer constant, [Q] is the quencher concentration, N is the Avogadro con stant, and V is the volume of the active sphere. The fluorescence quen ching by the first three chlorohydrocarbons was attributed to the cont emporaneous effect of dynamic quenching and static quenching. There ex ists, at least mathematically, a critical quencher concentration [Q](c ) When the quencher concentration [Q] < [Q]c, the fluorescence quenchi ng is dominated by the dynamic quenching part; when [Q] > [Q](c), it i s dominated by the static quenching part. However, the fluorescence qu enching by Cl2CHCHCl2 was attributed to only static quenching. Further more, it was proposed that the dynamic quenching may be related with t he electrical positivity of the central carbon nucleus of the quenchin g molecules while the static quenching may be caused by the ''outside heavy atom effect'' of the Cl element. (C) 1996 John Wiley & Sons, Inc .