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meso-Tetraphenylporphyrin (TPP) and its two substituted derivatives (meso-tetrakis(4-cyanophenyl)porphyrin [TPP(CN)4] and meso-tetrakis(4-methoxyphenyl)porphyrin [TPP(OMe)4]) were synthesized. Their nonlinear absorption and refraction properties were studied using the Z-scan technique in the picosecond (ps) and nanosecond (ns) regimes. The open aperture Z-scan results reveal that TPP and TPP(CN)4 display an identical reverse saturable absorption (RSA) character in the ps and ns regimes. While TPP(OMe)4 exhibits a transition from saturable absorption (SA) to RSA in the ps regime and a typical RSA character in the ns regime. The closed aperture Z-scan results show that TPP(CN)4 and TPP(OMe)4 have regular enhancement of the magnitude of nonlinear refraction as compared to their parent TPP in both the ps and ns regimes. In addition, the second-order molecular hyperpolarizabilities (γ) of these three porphyrins are calculated, and the γ values of TPP(CN)4 and TPP(OMe)4 are remarkable larger than that of TPP. The introduction of the electron-withdrawing group CN and the electron-donating group OMe into TPP has enhanced its nonlinear refraction and γ value, and tuned its nonlinear absorption (TPP(OMe)4), which could be useful for porphyrin-related applications based on the desired NLO properties.

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Improving the emission from rare earth ions doped materials is of great importance to broaden their application in bio-imaging, photovoltaics and temperature sensing. The green emissions of , the enhancement mechanism was discussed. Moreover, the result of temperature-dependent enhancement revealed that the enhancement factor reached its maximum (2.5) as the sample heated to 120°C, which is due to the competition of two major thermal effects acting in the co-excited up-conversion processes.In addition, the same enhancement of green emissions was also observed in [4] and in vitro/in vivo biological application. [5][6][7] However, because of their small absorption cross-section, the up-converting luminescence is not strong enough in many practical applications. To overcome this drawback, Yb 3+, acted as sensitizer, has been co-doped into the materials to transfer 980 nm energy to Ln 3+ . [8,9] Intriguingly, the luminescence can also be enhanced through the core-shell structure, which can eliminate energy dissipation to nanoparticle' surface. [10][11][12] Surface plasmon resonance of noble metals has been used to overcome this drawback. [13][14][15] Moreover, the up-converting luminescence can also be improved under co-excited condition with two different wavelength lasers. [16][17][18][19] Several groups have analyzed the luminescent behaviors of Er 3+ / Yb 3+ co-doped materials for they show strong green emissions. [20][21][22] Besides the sensitizer and activator, the host matrix also plays an important role in up-conversion luminescence. Because of its low toxicity, thermal stability and high photo-chemical stability, [23][24][25][26] Gd 2 (MoO 4 ) 3 was chosen as the host matrix in our work.In this work, we greatly increase the green emissions of Abbreviations used: I 980 , the integral intensity of green emissions under excitation with a 980 nm; I 808 , the integral intensity of green emissions under excitation with a 808 nm laser; I 980+808 , integral intensity of green emissions under co-excitation with both the 980 and 808 nm lasers; TEM, transmission electron microscopy; XRD, X-ray diffraction.