Dae Won Cho

Recyclable magnetic CoFe2O4/BiOX (X = Cl, Br and I) microflowers for photocatalytic treatment of water contaminated with methyl orange, rhodamine B, methylene blue, and a mixed dye

The recycling of photocatalysts and improving their activities by hybridizing two materials are important. Herein, nanosize ferromagnetic (Ms = 62.3 emu g−1) CoFe2O4 nanoparticles (NPs) were embedded into nanosize-assembled BiOX (X = Cl, Br and I) microflowers and examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV-visible absorption spectroscopy, Fourier-transform infrared spectroscopy, and photoluminescence spectroscopy. The adsorption and photocatalytic performance of CoFe2O4/BiOX for methyl orange (MO), rhodamine B (RhB), methylene blue (MB), and a mixed dye (MO + RhB + MB) were examined under UV and visible light irradiation. The adsorption capacity of CoFe2O4/BiOI for RhB was 160 mg gcat−1, which is significantly larger than the <5 mg gcat−1 obtained for CoFe2O4/BiOCl and CoFe2O4/BiOBr. The photocatalytic activity was observed in the order of CoFe2O4/BiOBr < CoFe2O4/BiOCl < CoFe2O4/BiOI for RhB. Their adsorption and photocatalytic performances were also investigated with pure MO, pure MB and a mixed dye. MO in the mixed dye was the most easily removed by the catalysts under light exposure. Based on the scavenger tests, h+ and ˙O2− play major and minor roles in the photodegradation of the dyes, respectively. Although the ˙OH radical was formed for CoFe2O4/BiOBr and CoFe2O4/BiOCl, it has a much smaller role than the other active species.

β-Cyclodextrine-SO3H: the most efficient catalyst for one-pot synthesis of 2H-indazolo[2,1-b]phthalazine-triones under solvent-free conditions

An environmentally benign and efficient method has been developed for the synthesis of a series of 2H-indazolo[2,1-b]phthalazine-triones derivatives with β-cyclodextrine-SO3H as a recyclable catalyst by simply combining of various aldehydes with cyclic 1,3-diketones and phthalhydrazide under solvent free condition. The advantageous features of this methodology are high atom-economy, operational simplicity, shorter reaction time, convergence, and facile automation.Graphical AbstractA greener, efficient, and expeditious method has been developed for the synthesis of 2H-indazolo [2,1-b] phthalazine-triones derivatives with β-cyclodextrine-SO3H as a recyclable catalyst for the first time.

Single electron transfer promoted photoaddition reactions of α-trimethylsilyl substituted secondary N-alkylamines with fullerene C60

Single electron transfer (SET) promoted photoaddition reactions of secondary N-α-trimethylsilyl-N-alkylamines to C60 were explored to gain a deeper understanding of the mechanistic pathways followed and to expand the library of novel types of organofullerenes that can be generated using this approach. The results show that photoreactions of 10% EtOH-toluene solutions containing C60 and N-α-trimethylsilyl-N-alkylamines produce either aminomethyl-1,2-dihydrofullerenes or symmetric fulleropyrrolidines as major products depending on the nature of alkyl substituents. In contrast, photoreactions of 10% EtOH-ODCB solutions of these amines with C60 mainly lead to the formation of symmetric fulleropyrrolidines. Based on the analysis of product distributions and the results of earlier studies, two feasible mechanistic pathways are proposed for these processes. One route is initiated by SET from the amine substrates to the triplet-excited state of C60 to form the corresponding aminium radicals and C60 anion radicals. EtOH-promoted desilylation of the aminium radicals then takes place to produce aminomethyl radicals which can either add to C60 or couple with the C60 radical anions to form respective radicals or anion precursors of aminomethyl-1,2-dihydrofullerene products. The competing pathway leading to the generation of symmetric fulleropyrrolidines also involves the formation of aminomethyl radicals by using the sequential SET-desilylation process. In this route, the aminomethyl radicals are oxidized by SET to C60 to form iminium ions, which are then transformed to azomethine ylides by a pathway involving a second molecule of the secondary amine. Dipolar cycloaddition of the azomethine ylides to C60 forms the symmetric fulleropyrrolidine cycloadducts. Importantly, the observation that symmetric fulleropyrrolidines are the sole products formed in photoreactions between N-α-trimethylsilyl-N-alkylamines and C60 in 10% EtOH-ODCB has synthetic significance.