PHOTOPHYSICAL PROCESSES ON A LATEX SURFACE - ELECTRONIC-ENERGY TRANSFER FROM RHODAMINE DYES TO MALACHITE GREEN

We bound pairs of donor-acceptor dyes to the surface of polystyrene latex particles and studied the characteristics of the surface as a reaction field for electronic energy transfer. The donors are rhodamine B (RB) and rhodamine 6G (R6G), and the acceptor is malachite green (MG). Steady-state fluorescence measurements revealed that the dyes are highly concentrated on the latex surface; thus, energy transfer occurs up to 100 times more effectively on the surface than in an aqueous solution. Picosecond fluorescence measurements of donor decay in the presence of the acceptor provided us with the fractal dimensions of the systems: 1.75 from RB-MG and 1.82 from R6G-MG. The values suggest that the latex surface is flat and smooth on a molecular scale and that the distribution of the dyes is slightly inhomogeneous. The kinetics of exchange of the dyes between the latex particles were also studied. The rate constants obtained are 6.4 min-I for RB and 2.2 min-1 for R6G. The results seem to be useful for characterizing the latex surface as a reaction field for photophysical processes.