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RISS 인기검색어
- 검색키워드
- 저자 : Wim M. De Borggraeve (검색결과 2 건)
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Photophysics and stability of cyano-substituted boradiazaindacene dyes
Cieslik-Boczula, Katarzyna,Burgess, Kevin,Li, Lingling,Nguyen, Binh,Pandey, Lesley,De Borggraeve, Wim M.,Van der Auweraerc, Mark,Boens, Noel Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.7
The solvatochromic photophysical properties of two fluorescent, cyano-substituted BODIPY dyes-8-(4-bromophenyl)-3,4,4,5-tetracyano-4-bora-3a,4a-diaza-s-indacene (4CN) and 8-(4-bromophenyl)-3,5-dicyano-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (2CN)-have been studied in various solvents by UV-vis spectrophotometry and steady-state and time-resolved fluorometry. These two BODIPY analogues have comparable photophysical properties, implying that displacement of F by CN at boron has a negligible effect. Both compounds have high fluorescence quantum yields $\Phi_f$ (0.65-0.90 for 4CN and 0.63.0.88 for 2CN) in the solvents studied and display mono-exponential fluorescence decay profiles in nonprotic solvents. A new, generalized treatment of the solvent effect based on four mutually independent, empirical solvent scales (dipolarity, polarizability, acidity, and basicity of the medium) indicates that solvent polarizability and, to a lesser degree, solvent (di)polarity are crucial factors causing the solvent-dependent shifts of the UV-vis absorption and fluorescence emission. The rate constants of radiative deactivation ($k_f$) are nearly independent of the nonprotic solvent [$k_f=(1.4{\pm}0.1){\times}10^8s^{-1}$ for 4CN and ($1.5{\pm}0.2){\times}10^8s^{-1}$ for 2CN]. Both compounds undergo a color change in polar aprotic solvents (acetone, acetonitrile, and N,N-dimethylformamide), which can be stopped by addition of $HClO_4$. The kinetics of this color change indicates that the decomposition of these cyano-substituted BODIPY compounds is complex.
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Facile Method to Obtain Low DS β-ketoesters and Esters of Microfibrillated Cellulose
Carmen C. Piras,Scott A. Jamieson,Emiliano Fratini,Susana Fernández-Prieto,Johan Smets,Wim M. De Borggraeve 한국섬유공학회 2020 Fibers and polymers Vol.21 No.10
Herein we report a facile approach to prepare low DS microfibrillated cellulose acetoacetates and esters. All thereactions were performed directly in cellulose slurries without the need of solvent evaporation, which can cause hornification,and without damaging the fibres. The products obtained display the inserted functionalities while retaining the main featuresand morphology of the unmodified cellulose fibres. In comparison to previously reported synthetic routes, this method iscost-effective, more environmentally friendly through omission of extra solvents and the possibility of reusing the dispersingagents, which can be recovered by distillation.
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