Preferred formation of coplanar inclined fluorescent J-dimers in rhodamine101 doped silica gels

Rhodamine 101 (R101) doped silica gels were prepared through the sol-gel pr ocess with dye concentrations ranging from 4.0 x 10(-6) to 6.4 x 10(-4) M. Excitation and emission fluorescence spectra and lifetime measurements were recorded for R101 doped silica gels in the whole range of concentrations. The photophysical behavior of the gel-glasses doped with high concentration s of R101 resembles that of fluorescent J-dimers in a coplanar inclined con figuration. The formation of fluorescent J-dimers in a coplanar inclined ra ther than in an oblique configuration is discussed in terms of the molecula r structure of R101.