The photoluminescence response of Rhodamine 6G (R6G) laser dye intercalated into solid thin films of Laponite (Lap) clay is studied as a function of dye loading. Fluorescence spectroscopy (steady-state and time-resolved techniques) was used to characterize the R6G species adsorbed into the solid films. For very diluted R6G loadings (40% CEC), with a reminiscent fluorescence band at around 600 nm.

We report on the photophysical properties and laser action of five newly synthesized dipyrromethene‚BF 2 complexes that are analogues of the laser dye PM567 dissolved in apolar, polar nonprotic, and polar protic solvents, paying attention to the effect of the dye concentration. All of these dyes have a common chromophore core and differ in the length of 8-(ω-acetoxy)polymethylene substituent. When pumped transversely at 534 nm, laser efficiencies up to 59% were obtained, which were found to be nearly independent of the nature of the solvent and the length of the polymethylene chain. Good correlations between the photophysical properties in diluted solutions and the lasing characteristics in moderately concentrated solutions have been observed. The presence of the 8-substituent does not modify significantly the photophysics of the chromophore, if the polymethylene chain has five or more methylene groups. Theoretical calculations were performed to rationalize this behavior.

Absorption and fluorescence (steady-state and time-correlated) techniques are used to study the photophysical characteristics of the pyrromethene 650 (PM650) dye. The presence of the cyano group at the 8 position considerably shifts the absorption and fluorescence bands to lower energies with respect to other related pyrromethene dyes; this is attributed to the strong electron-acceptor character of the cyano group, as is theoretically confirmed by quantum mechanical methods. The fluorescence properties of PM650 are intensively solvent-dependent. The fluorescence band is shifted to lower energies in polar/protic solutions, and the evolution of the corresponding wavelength with the solvent is analysed by a multicomponent linear regression. The fluorescence quantum yield and the lifetime strongly decrease in polar/protic solvents, which can be ascribed to an extra nonradiative deactivation, via an intramolecular charge-transfer state (ICT state), favoured in polar media.

X-ray diffraction and Vis-absorption spectroscopy with linearly polarized light are used to determine the orientation of rhodamine 6G (R6G) dye in the interlayer space of supported films of Laponite B (Lap) clay with different dye loadings. XRD profiles suggest that the d 001 interlayer space increases with the relative amount of dye in the clay surface, probably due to a more perpendicular disposition of the adsorbed molecules with respect to the clay layers in high dye content films. This orientation reduces the covering area per adsorbed molecule, providing a more compact and packed arrangement of the dye molecules. This is confirmed by linearly polarized absorption spectra, from which the orientation angle of the adsorbed molecules with respect to the clay layer can be evaluated. Indeed, R6G/Lap supported films present an anisotropy effect and, depending on the dye loadings, different evolutions of the dichroic ratio with the twisted δ angle between the normal to the film and the incident beam are observed. For very diluted R6G/Lap films, the R6G monomers adopt an inclined disposition of around 62° with respect to the film normal. Increasing the loadings, dimer, and higher-order aggregates of R6G can be disposed in two preferential orientations:  an inclined angle of around 60°, common in all loading samples, favors long-displaced coplanar aggregates, characterized by an absorption J-band, and a second more perpendicular disposition of the monomer units as the dye content is increased leading to short-displaced coplanar aggregates, identified by an absorption H-band.

The photophysical, lasing and thermostability properties of newly synthesized analogs of the commercial dye pyrromethene 567 (PM567) have been measured in polymeric matrices of poly(methyl methacrylate) both when used as a dopant and when covalently bounded to the polymeric chain. These analogs have an acetoxy or a polymerizable methacryloyloxy group at the end of a polymethylene chain at Position 8 of the PM567 chromophore core. Clear correlations between photophysical and lasing characteristics are observed. Linking chain lengths with three or more methylene units give the highest fluorescence quantum yields (as high as 0.89) and lasing efficiencies (as high as 41%). The covalent linkage of the chromophore to the polymeric chain via the methacryloyloxy group improves the photostability of the PM567 chromophore.