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Abstract Azo dyes with electron-donating and neutral substituents in PMMA matrix and solution were prepared and characterized. High optical quality films were made for linear optical characterization of azo dyes. Two-photon absorption spectra, for investigated compounds dissolved in DMF, were obtained by Z-Scan measurements. The π-π* transition of investigated compounds is significantly red-shifted and overlaps with n-π* transition. Accordingly azo dye with electron-donating group is more red-shifted compared to molecule with neutral group. Refractive index and efficiency of two-photon absorption cross-section for azo dye with neutral substituent is lower compared to azo dye with electron-donating substituent. [ABSTRACT FROM AUTHOR]

Abstract: We report on synthesis and optical properties of new organic compounds based on substituted pyrazole ring. The investigated pyrazoline derivatives (PRDs) exhibit efficient broadband photoluminescence which covers nearly whole visible spectrum. The experimental results are compared to quantum chemical calculations. Amplified spontaneous emission and photodegradation measurements were performed for hybrid systems based on selected PRDs doped into poly(methyl methacrylate) matrix proving the potential utility of such systems in lasing applications. Two-photon absorption (TPA) properties were characterized by the femtosecond Z-scan technique. [Copyright &y& Elsevier]

Abstract: Synthesis, crystal structure, morphology and optical properties of three various NaYF4 nanoparticle systems co-doped with Tm3+ and Yb3+ ions have been investigated. Characterization of ultrasmall (size ∼8nm), small (∼25nm) NaYF4:2%Tm3+, 20%Yb3+ nanoparticles and core–shell structures (NaYF4:20%Yb3+–NaGdF4:2%Tm3+) synthesized according to two different protocols is presented. We have found that the up-conversion luminescence is strongly influenced by the nanoparticle size, internal structure and spatial distribution of active Tm3+ ions. Further spectroscopic studies revealed significant fluorescence rise and decay time lengthening of the 1G4 energy level of Tm3+ ions in NaYF4:20%Yb3+–NaGdF4:2%Tm3+ core–shell nanoparticles. The formation of the core–shell structures was proven indirectly through the average crystalline size increase between the bare core and core–shell nanoparticles, the observed changes in EDX composition as well as variation of Tm3+ ions luminescence properties. [Copyright &y& Elsevier]