The fast electronic nonlinear optical (NLO) properties of a novel synthetic organic dendrimer are reported. The complete synthesis of the organic dendrimer is provided. Both the z-scan and self-phase modulation techniques were used to measure the nonlinear refractive index. The magnitude of the nonlinear refractive index (n 2) was measured to be 1.1 × 10 - 4 cm2/GW. The presence of two-photon absorption was observed and the coefficient (β) was found to be 1.2 × 10-2 cm/GW. The nonlinear figure of merit of the dendrimer system is found to be 0.02 for intensities used in our experiments. The NLO responses of the individual structural components of the dendrimer molecule are provided to probe the structure−function relationships. The presence of a higher order, χ(5), NLO effect was also detected and analyzed. The fast electronic processes of the dendrimer molecule and its components where also investigated by up-conversion luminescence spectroscopy. These studies provide the first probe into the ultrafast electronic NLO effects in organic dendrimers.

The ultrafast intrinsic dynamics of an organic dendrimer in solution and in a thin film is reported using fluorescence upconversion spectroscopy. Femtosecond decay is detected at higher emission energies, while at lower energies a fluorescence rise time (ϳ3 ps͒ was observed that is dependent on the solvent's polarity. A strong excitation energy dependence of the decay pattern was also observed. Different synthetic functional groups that comprise the macromolecular dendrimer structure were investigated. The mechanism, which describes the complex dynamics in the dendrimer system, was found to be associated with the excitation of the attached chromophore nitroaminostilbene. These results indicate the absence of excited-state interactions of functional groups within the dendrimer macromolecule. A model, which includes the existence of an intermediate nonradiative state, is proposed to describe the complex ultrafast fluorescence dynamics in the dendrimer system.

This work developed a simple, rapid approach to controllable and selective decoration of noble metal nanoparticles on atomic layered MoS2via a single-step micro-power laser-induced defect engineering and photo-reduction technique.

Liu, L.; Li, S.; He, X. N.; Huang, X.; Zhang, C. F.; Fan, L. S.; Wang, M. X.; Zhou, Y. S.; Chen, K.; Jiang, L.; Silvain, J. F.; and Lu, Yongfeng, "Flame-enhanced laser-induced breakdown spectroscopy" (2014 Abstract: Flame-enhanced laser-induced breakdown spectroscopy (LIBS) was investigated to improve the sensitivity of LIBS. It was realized by generating laser-induced plasmas in the blue outer envelope of a neutral oxy-acetylene flame. Fast imaging and temporally resolved spectroscopy of the plasmas were carried out. Enhanced intensity of up to 4 times and narrowed full width at half maximum (FWHM) down to 60% for emission lines were observed. Electron temperatures and densities were calculated to investigate the flame effects on plasma evolution. These calculated electron temperatures and densities showed that high-temperature and low-density plasmas were achieved before 4 µs in the flame environment, which has the potential to improve LIBS sensitivity and spectral resolution.