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Aqueous solutions of four cationic poly(propylenimine) low-generation dendrimers of different architecture and hydrophobicity have been examined as media for acid-base reactions of indicator dyes. The cationic dendrimers in solution can be considered as oligomers of cationic polyelectrolytes, or surfactant-like species, able to form micelles through self-association or sometimes even as unimolecular micelles. The dendrimers influence the ionization constants, tautomeric equilibria, and absorption/emission/excitation spectra of indicator dyes. The p K a values of the majority of the indicator dyes decrease in dendrimer solutions, often by 1-2 p K a units, similar to effects registered in micellar solutions of cationic surfactants. Analogously, the shifts of absorption band maxima indicate that the microenvironments of the dyes bound to the dendrimers are less polar than in water. However, some spectral effects denote the specificity of the dendrimers. The greatest difference between the dendrimers and spherical surfactant micelles is revealed by kinetic processes, especially of bromophenol blue alkaline fading in a dendrimer solution but not in a micellar surfactant solution. Within the dendrimer series, the most significant differences were observed for substances possessing n-dodecyl tails on the one hand and those without such hydrophobic portions on the other. For the last-named, the decrease in p K a's of indicators, band shifts of their anions, and in particular displacement of tautomeric equilibria compared with aqueous solutions are much smaller than for more hydrophobic dendrimers.

This paper addresses the carbon co-doping of Ce-doped garnets, an efficient scintillation material and white light phosphor. The composition and the optical and scintillation properties of carbon-co-doped Y3Al5O12 (YAG) are studied at different cerium and carbon concentrations. YAG:Ce,C crystals were grown in the Ar + CO atmosphere from W crucibles. The carbon concentration reaches 0.5 atom %, but it does not affect the Ce distribution coefficient. The appearance and elimination of color centers are discussed in comparison to Ce-free YAG:C crystals. The tuning of cerium and carbon concentrations provides a light yield enhancement of up to 29 600 phot/MeV. The achieved enhancement may extend the application range of garnet-type phosphors and scintillators.

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