Specifics of recombination processes in pyrolytic cadmium sulfide films     

T. L. Maiorova  V. G. Kluev  M. Fam Thi Khai  V. S. Bykovskaya 《High Energy Chemistry》2009,43(7):599-601

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Dr. Shun Nishimura  Dr. Junya Ohyama  Takaaki Kinoshita  Son Dinh Le  Dr. Keisuke Takahashi 《ChemCatChem》2020,12(23):5836-5836

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Janis Jermaks  Phong K. Quach  Zara M. Seibel  Julien Pomarole  Tristan H. Lambert 《Chemical science》2020,11(30):7884

A computational and experimental study of the hydrazine-catalyzed ring-opening carbonyl–olefin metathesis of norbornenes is described. Detailed theoretical investigation of the energetic landscape for the full reaction pathway with six different hydrazines revealed several crucial aspects for the design of next-generation hydrazine catalysts. This study indicated that a [2.2.2]-bicyclic hydrazine should offer substantially increased reactivity versus the previously reported [2.2.1]-hydrazine due to a lowered activation barrier for the rate-determining cycloreversion step, a prediction which was verified experimentally. Optimized conditions for both cycloaddition and cycloreversion steps were identified, and a brief substrate scope study for each was conducted. A complication for catalysis was found to be the slow hydrolysis of the ring-opened hydrazonium intermediates, which were shown to suffer from a competitive and irreversible cycloaddition with a second equivalent of norbornene. This problem was overcome by the strategic incorporation of a bridgehead methyl group on the norbornene ring, leading to the first demonstrated catalytic carbonyl–olefin metathesis of norbornene rings.

A computational and experimental study has uncovered a second generation hydrazine that enables the catalytic ring-opening carbonyl–olefin metathesis of norbornenes.  相似文献   

    

Ngo Thi Chinh  Nguyen Thi Le Anh  Pham Thi Thao  Dao Duy Quang 《Vietnam Journal of Chemistry》2020,58(2):157-161

Antioxidant and photoprotective properties of two natural acridone derivatives namely Paratrimerin C ( 1 ) and Citrusinine‐I ( 2 ) have been studied by DFT and TD‐DFT at the M05‐2X/6‐311++G(3df, 3p)//M05‐2X/6‐31+G(d) level of theory. Three common mechanisms characterized for the antioxidant properties including H‐atom transfer (HAT) and proton transfer (PT) towards HOO^●/HO^● radicals and single electron transfer (SET) were investigated in the gas phase, water and pentyle thanoate. The DFT results revealed that both compounds can efficiently scavenge HOO^● and HO^● radicals via HAT mechanism in all media. Particularly, the HAT reactions of 2 with HO^● radical in water are the most favored reaction (∆H ‐37.7 kcal/mol). In addition, the efficient UV‐absorption ability of the studied compound was elucidated by TD‐DFT. All compounds can absorb UV radiations in the range of 200‐335 nm, for which the easiest excitations are at 334‐332 nm and the strongest absorptions were found at 234‐227 nm, for 1 and 2 , respectively. The HOMO to LUMO and HOMO‐3 to LUMO (π‐π*) transitions are assigned for the corresponding UV‐absorption.  相似文献   

    

Nguyen Thi Lieu  Pham Quoc Trung  Le Tran Thu Trang  Le Truong Giang 《Vietnam Journal of Chemistry》2020,58(3):302-308

In the present study, the glassy carbon electrode (GCE) modified with platinum nanoflowers (PtNFs/GCE) has been developed for copper determination. Differential pulse anodic stripping voltammetry (DPASV) was used to investigate the performance of the modified electrode. The effects of pH, deposition potential, deposition time, and step potential were investigated on the stripping peak current response of copper based on response surface methodology. The results indicated that pH of 5.07, deposition potential (‐0.605 V), deposition time (150.4 s), and step potential (6 mV) results in the maximum current density. Under the optimized conditions, a linear regression was obtained in the range of 0.75‐80 μg.L^‐1 and detection limit also was found to be 0.312 μg.L^‐1 by DPASV on the PtNFs/GCE surface. The fabricated electrode (PtNFs/GCE) showed good reproducibility and repeatability as well as high recovery. The practical application of the PtNFs/GCE was demonstrated by measuring the concentration of copper in real water samples.  相似文献   

    

Nguyen Thi Thu Tram  Dinh Hoang Anh  Huynh Hoang Thuc  Nguyen Trong Tuan 《Vietnam Journal of Chemistry》2020,58(1):63-66

Lichens are a promising source of good anticancer agents. However the study on their bioactivities remains limited, especially in Vietnam. In this study, three extracts of lichen Usnea undulata Stirt. including n‐hexane, acetone and methanol were investigated for their cytotoxic activity on two human cancer cell lines (MCF‐7, NCI‐H460) and normal fibroblasts by sulforhodamine B (SRB) assay. The results showed that the n‐hexane extract exhibited the highest inhibition activity with IC₅₀ 5.26±0.13 μg/mL for MCF‐7 and 6.83±0.64 μg/mL for NCI‐H460, followed by acetone extract with IC₅₀ 66.44±1.37 μg/mL and 92.14±1.49 μg/mL, respectively. The methanol extract possessed weak cytotoxic effect against MCF‐7 and NCI‐H460 (IC₅₀ values more than 100 μg/mL). The n‐hexane extract demonstrated interesting activity particularly on MCF‐7 as good selectivity index was recorded (SI > 3). The phytochemical study on n‐hexane and acetone extracts led to the isolation of four compounds including usnic acid ( 1 ), methyl orsellinate ( 2 ), methyl β‐orsellinate ( 3 ), 7‐hydroxyl‐5‐methoxy‐6‐methylphtalide ( 4) in which compound ( 4 ) was isolated the first time in such species. Their structures were elucidated by NMR analysis and compared with literature data.  相似文献   

    

Nguyen Thi Thu Ha  Pham Van Cuong  Le Thi Tu Anh  Nguyen Thanh Tra  Ba Thi Cham  Ninh The Son 《Vietnam Journal of Chemistry》2020,58(3):343-348

A phytochemical study of the EtOAc extract of Garcinia mackeaniana leaves has resulted in the isolation and determination of five xanthones, consisting of norathyriol ( 1 ), mangiferin ( 2 ), allanxanthone C ( 3 ), garcinone E ( 4 ), and bannanxanthone E ( 5 ). The structures of these xanthones have been determined by NMR‐spectra and MS spectroscopic data. These isolated compounds were separated from G. mackeaniana species for the first time. In the antimicrobacterial assay against the growth of bacterium Staphylococcus aureus, compounds 3‐4 showed the significant IC₅₀ values of 5.41, and 4.29 μM/mL, respectively.  相似文献   

    

Nguyen Thuy Duong  Tran Boi An  Phan Thanh Thao  Vu Ke Oanh  Trinh Anh Truc  Pham Gia Vu  To Thi Xuan Hang 《Vietnam Journal of Chemistry》2020,58(1):108-112

In this work, graphene oxide (GO) was prepared by modified Hummer's method. Polyurethane coatings with different GO concentrations (0.1‐0.5 %) were prepared for corrosion protection of carbon steel. Synthesized GO was characterized by FTIR and XRD. Corrosion resistance of polyurethane coatings containing GO was investigated by electrochemical impedance spectroscopy and salt fog test. The effects of GO on protection performance of polyurethane coatings depended on its dispersion ability. GO at a concentration of 0.1 % significantly improved corrosion resistance of polyurethane coatings.  相似文献   

    

Vu Ngoc Hung  Dao Van‐Duong  Tran Thi Trang 《Vietnam Journal of Chemistry》2020,58(4):488-493

Herein, the sol‐gel method is conducted to synthesize the spinel‐layered Li₂MnTiO_4+z (0.5LiMnTiO₄•0.5Li₂Mn_0.5Ti_0.5O₃) nanoparticles as a cathode material for Li‐ion batteries. The structural and electrochemical properties of the material are investigated by means of X‐ray diffraction, scanning electron microscopy, electrochemical impedance spectroscopy, and charge‐discharge tests. The obtained sample shows a high capacity of 200 mAh g^‐1 with a capacity retention of 90 % after 60 cycles at C/5.  相似文献   

    

Nguyen Hoang Chung  Nguyen Thi Thu Hoai  Le Quang Dien 《Vietnam Journal of Chemistry》2020,58(4):494-499

In this study, the hydrolysate containing ~15 g/L of xylose, which was obtained from Acacia mangium wood sawdust was used for the synthesis of xylose by a continuous distillation method. The synthesis was conducted at 150 °C for 7 h using a carbon‐based sulfonated catalyst (CBSC) from the same biomass source with an acid density of about 4.0 mmol/g. The CBSC showed its efficient catalytic activity in the dehydration of xylose to furfural. Under the optimal catalyst dosage of 20 wt% over xylose, the yield of furfural was 20.4 mol% and 34 wt% of xylose was transformed to furfural. The results presented a successful utilization of a wood‐derived solid acid catalyst for production of furfural from the same biomass source as a sustainable production of furans for biofuel additives.  相似文献