Controllable assembly of zeolite beta monolayers and bilayers on various substrates using the Langmuir-Blodgett technique
Contributors: Honghong Xu, Baoquan Zhang, Jian Li, Xiufeng Liu
... The Langmuir-Blodgett (L-B) technique was employed to fabricate the monolayers and bilayers of nano-sized beta (nano-beta) crystals, and the monolayers of micrometer-sized beta (micro-beta) crystals on various substrates including glass plate, α-Al2O3 disk, glass capillary tube, copper wire, stainless-steel tube and γ-Al2O3 tube. With respect to the methanol suspension of 1 wt.% Nano-beta modified with cetyltrimethylammonium bromide (CTAB), a two-region surface pressure-area isotherm was obtained, leading to the formation of both Nano-beta monolayers and bilayers with satisfactory degree of coverage (DOC) and close packing (DCP) under each transfer surface pressure. When nano-beta crystals were dealuminated, the surface pressure-area relation was reduced to the one-region isotherm, and the resulting L-B film contained aggregated areas. As for the assembly of micro-beta crystals, both methanol and sec-butanol were used as the dispersant. The resulting micro-beta monolayer was randomly oriented with the sedimentation of large truncated-square-bipyramid crystals on compression by using the methanol suspension. The use of sec-butanol as the dispersant resulted in the enhanced hydrophobicity of micro-beta crystals due to the chemical reaction of sec-butanol molecules with surface silanols, leading to the formation of c-oriented micro-beta monolayers over various substrates, and simultaneously the sedimentation of large truncated-square-bipyramid crystals did not occur. Under the structure direction of the c-oriented micro-beta monolayer in the seeded growth, the dense and preferentially c-oriented zeolite beta film could be fabricated, which could not be formed on either the Nano-beta monolayer or the micro-beta monolayer with random orientation. Therefore, it would be concluded that the growth of beta crystals over the seed layer could be followed by the epitaxial growth mechanism.
Preparation of mesoporous Al-MCM-41 from natural palygorskite and its adsorption performance for hazardous aniline dye-basic fuchsin
Contributors: Yuan Guan, Shaomang Wang, Xin Wang, Cheng Sun, Yongbo Wang, Lingjie Hu
... A promising mesoporous SiAl material, Al-MCM-41 was successfully prepared by alkali calcination leaching of natural palygorskite, and sequent hydrothermal synthesis coupled with calcination. The morphology, structure, surface area and pore-size distribution of the material were characterized by scanning electron microscopy, small-angle X-ray diffraction and N2 adsorption–desorption isotherms. The Al-MCM-41 possessed better crystallinity and larger specific surface area with CTAB/SiO2 mass ratio of 0.1:1, pH of 5, crystallization temperature of 110 °C, crystallization time of 12 h and calcination of 550 °C for 5 h. The Al-MCM-41 was used as an adsorbent for the removal of hazardous aniline dye-basic fuchsin from water. Adsorption kinetics and isotherms analysis indicated that adsorption of basic fuchsin onto Al-MCM-41 followed pseudo-first-order model and Langmuir adsorption isotherm. In addition, intra-particle diffusion was rate determining step of the adsorption process. The results demonstrated that the as-synthesized Al-MCM-41 had potential applications in the treatment of waste water.
Contributors: Walter Finsinger, Jordan Fevre, Ildikó Orbán, Ilona Pál, Ildikó Vincze, Katalin Hubay, Hilary H. Birks, Mihály Braun, Mónika Tóth, Enikő K. Magyari
... To investigate Holocene vegetation and fire-disturbance histories in the treeline ecotone, macroscopic charcoal, plant-macrofossil, and pollen records from two lacustrine sediment records were used. Lake Lia is on the southern slope and Lake Brazi is on the northern slope of the west-east-oriented Retezat Mountain range in the Romanian Carpathians. The records were used to reconstruct Holocene fire-return intervals (FRIs) and biomass burning changes. Biomass burning was highest at both study sites during the drier and warmer early Holocene, suggesting that climate largely controlled fire occurrence. Fuel load also influenced the fire regime as shown by the rapid biomass-burning changes in relation to timberline shifts. Overall, the number of inferred fire episodes was smaller on the northern than on the southern slope. FRIs were also comparatively longer (1000–4000 years) on the northern slope where Picea abies-dominated woodlands persisted around Lake Brazi throughout the Holocene. On the southern slope, where Pinus mugo was more abundant around Lake Lia, FRIs were significantly shorter (80–1650 years). A period of frequent fire episodes occurred around 1900–1300 cal yr BP on the southern slope, when chironomid-inferred summer temperatures increased and the pollen record documents increased anthropogenic activity near the treeline. However, the forest clearance by burning to increase grazing land was subdued in comparison to other European regions.
Original Article - Microwave-assisted intermolecular aldol condensation: Efficient one-step synthesis of 3-acetyl isocoumarin and optimization of different reaction conditions
Contributors: Murat Koca, Ali S. Ertürk, Adil Umaz
... This paper describes the optimization and comparison of conventional and microwave-assisted methods for efficient, cheap, one-pot, and straightforward synthesis of isocoumarins under mild reaction conditions. On this basis of this aim, synthesis of 3-acetyl isocoumarin from 2-formylbenzoic acid with mono-chloroacetone was chosen as a model reaction. Afterward, four different methods conventional (Method A), microwave open vessel (Method B), microwave sealed vessel (Method C), and microwave closed system (Method D) were used methodologically to determine best experimental conditions for each of these methods in this model reaction. The results revealed that developed Methods A, C and D could be used successfully under solvent-free conditions with good yields (84–87%) for the future efficient, one-pot synthesis of isocoumarins. This paper is also a first for characterizing 3-acetyl isocoumarin by using ATR, 1H NMR, 13C NMR and GC–MS.
Original Article - A facile designed highly moderate craspedia flowerlike sulphated Bi2O3-fly ash catalyst: Green synthetic strategy for (6H-pyrido[3,2-b]carbazol-4-yl)aniline derivatives in water
Contributors: Kannan Thirumurthy, Ganesamoorthy Thirunarayanan
... The air pollutant fly ash was facile designed as a green catalyst and practical to organic synthesis. We have designed sulfated Bi2O3-fly ash catalyst (12wt%) and it was characterized by Fourier transform infrared (FT-IR), confocal Raman, Powder X-ray diffraction (XRD), Field emission electron microscopy (FE-SEM), elemental color mapping, energy-dispersive X-ray spectroscopy (EDS), Transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) techniques. The sulfated Bi2O3-fly ash was found an excellent catalytic application for the synthesis of (6H-pyrido[3,2-b]carbazol-4-yl)aniline derivatives in water has been described. The synthesized (6H-pyrido[3,2-b]carbazol-4-yl)aniline derivatives were confirmed by spectral techniques Fourier transform infrared (FT-IR), Nuclear magnetic resonance (NMR) and Liquid chromatography–mass spectrometry (LC–MS). The significant catalytic role of Bi–N interaction was readily form adduct, moreover Bi–O bond was favorable for hydrogen abstraction, dehydration and aromatization. Due to the strong potential, the precise reaction time and high yield have been achieved, which is realized from hot filtration test. The sulfated Bi2O3-fly ash catalyst could be reused for five successive run, the resulting in no appreciable change in the catalytic activity. The crystal phase and surface morphology of fifth run catalyst were examined by powder XRD, FE-SEM, EDS and TEM techniques, and the results revealed no changes in catalyst nature. The sulfated Bi2O3-fly ash catalyst has high efficiency, reusability, good catalytic activity, environmentally harmless and notable potential in industrial applications.
El Castillo (Cantabria, northern Iberia) and the Transitional Aurignacian: Using radiocarbon dating to assess site taphonomy
Contributors: Rachel Wood, Federico Bernaldo de Quirós, José-Manuel Maíllo-Fernández, José-Miguel Tejero, Ana Neira, Thomas Higham
... The majority of archaeological remains found at El Castillo in northern Iberia were excavated between 1910 and 1914 by Hugo Obermaier. Since the 1980s El Castillo has been studied through a detailed analysis of Obermaier's original excavation notes, the cleaning and study of the extant section, and the excavation of material in the shelter entrance. Radiocarbon dating of charcoal from the modern (1980s onwards) excavation suggested that unit 18, corresponding to Aurignacian Delta of the 1910s excavation, was significantly earlier than other Aurignacian assemblages in western Europe. Combined with a reanalysis of the lithic and osseous industry, these dates led to the suggestion that material in unit 18 and Aurignacian Delta was a transitional industry, showing a gradual transformation of the Mousterian into the Upper Palaeolithic. The conclusion has profound implications for understanding the appearance of the Upper Palaeolithic in western Europe. However, the theory has been heavily debated, with criticism focusing on the analysis of the lithic and bone assemblage as well as the chronology. We focus on the latter, and assess whether the original dates were accurate, whether they were well associated with the archaeology, and whether there was vertical and lateral variation in the age of the assemblages within unit 18 and Aurignacian Delta. New radiocarbon dates on humanly modified bone suggest that in the new area of excavation, unit 18 is found to be earlier than 42 cal kBP, with no evidence of material of a younger age. In contrast, in the old excavation area, Aurignacian Delta does include material of a younger age. This suggests that discussion of the Transitional Aurignacian can only include material from unit 18, in the new area of excavation.
Contributors: Chao-rui Li, Si-liang Li, Guan-qun Wang, Zheng-yin Yang
... In this study, a novel fluorescein-derived Schiff-base ligand bearing a chromone moiety which was called 6-Hydroxy-3-formylchromone fluorescein hydrazone (1) has been designed, synthesized and evaluated as a Mg2+ “turn on” fluorescent probe. This probe 1 exhibited high selectivity and sensitivity towards Mg2+ over other important metal ions investigated, and the remarkable enhancement in fluorescence emission centered at 504nm was observed in the presence of Mg2+, which was attributed to the ring-opening process of the fluorescein fluorophore in probe 1 upon complexation of 1 with Mg2+. Furthermore, the “turn on” response of this probe 1 to Mg2+ was nearly completed within 3min, which indicated that this probe 1 could be utilized to sense and monitor Mg2+ for real-time detection.
Contributors: Filip Spaniel, Eduard Bakstein, Jiri Anyz, Jaroslav Hlinka, Tomas Sieger, Jan Hrdlicka, Natálie Görnerová, Cyril Höschl
... Detailed study of the period before schizophrenic relapse when early warning signs (EWS) are present is crucial to effective pre-emptive strategies.
Original article - Biogenic silver nanoparticles synthesized with rhamnogalacturonan gum: Antibacterial activity, cytotoxicity and its mode of action
Contributors: Aruna Jyothi Kora, R.B. Sashidhar
... Silver nanoparticles synthesized from gum kondagogu (5nm) were used to evaluate the antibacterial activity against Gram-positive and Gram-negative bacteria. To decipher the mode of antibacterial action of nanoparticles, a comprehensive study was carried out employing a variety of susceptibility assays: micro-broth dilution, antibiofilm activity, growth kinetics, cytoplasmic content leakage, membrane permeabilization, etc. The production of reactive oxygen species (ROS) and cell surface damage during bacterial nanoparticle interaction were also demonstrated using dichlorodihydrofluorescein diacetate, N-acetylcysteine; and scanning electron microscopy and energy dispersive X-ray spectra. Further, the biocompatibility with HeLa cell line was also evaluated. Compared to earlier reports, the minimum inhibitory concentration values were lower by 3.2- and 16-folds for Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli strains, respectively. The minimum bactericidal concentration values were lower by 4 and 50-folds. Thus, the biogenic silver nanoparticles were found to be more potent bactericidal agents in terms of concentration. The nanoparticles exhibited significant antibiofilm activity against test strains at 2μgmL−1, which can have implications in the treatment of drug resistant bacterial infections caused by biofilms. Growth curve in nanoparticle supplemented indicated a faster inhibition in Gram-negative bacteria as compared to Gram-positive. Treatment with nanoparticles caused cytoplasmic content leakage and membrane permeabilization in a dose dependent manner, an evidence for membrane damage. The observations noted in our study substantiated the association of ROS and membrane damage in the antibacterial action of silver nanoparticles. The promising antibacterial activity enables these nanoparticles as potential bactericidal material for various environmental and biomedical applications.
Original article - HPTLC-profiling of eleutherosides, mechanism of antioxidative action of eleutheroside E1, the PAMPA test with LC/MS detection and the structure–activity relationship
Contributors: Daniel Załuski, Rafał Kuźniewski, Zbigniew Janeczko
... Human body is constantly generating free radicals, which causes oxidative stress. Despite naturally occurring antioxidant systems in human body, free radicals cause lipid, proteins and DNA oxidation. New antioxidants are still urgent as well as their mechanisms of action should be explained. In this study, we investigated the mechanism by which eleutherosides B, E and E1 may act as antioxidants, identified eleutherosides in Eleutherococcus lasiogyne and Eleutherococcus giraldii, and explained in vitro the absorption of eleutheroside E1 based on passive transport. The DPPH∗ and DB-HPTLC tests were used to assess the antioxidant activity. Of the three eleutherosides, only eleutheroside E1 exhibited a strong anti-DPPH∗ activity (EC50 37.03μg/mL; 63mMol) compared to the raw extracts (EC50 170 and 180μg/mL for E. lasiogyne and E. giraldii). This activity was also confirmed by the DB-HPTLC autography technique. According to Załuski’s hypothesis, the antioxidant mechanism of eleutheroside E1 is based on the complexation of DPPH∗ molecule with its aryl radical. During this reaction, the aryl radical of eleutheroside E1 (E1∗) and DPPHH are created. Next, the aryl radical (E1∗) is complexed with another DPPH∗ molecule. Additionally, the aryl radical can be stabilized by the presence of the methoxy groups in the aromatic ring, which increases its antioxidative action. The HPTLC-identification of extracts showed the presence of eleutherosides B, E and E1 in both species. The PAMPA test coupled with LC/MS detection showed a low permeability of eleutheroside E1 across artificial membrane. Because eleutherosides belong to the polyphenols, the TPC and TFC were quantified. The TPC and TFC varied from 51.4 to 49.3mg/g dry extract for TPC, and from 5.73 to 4.91mg/g dry extract for TFC, for E. giraldii and E. lasiogyne, respectively. In conclusion, eleutheroside E1 in its pure form could be a chemopreventive ingredient of new pharmacological or dietary products, stimulating the GALT. These findings can explain partially the adaptogenic activity of eleutheroside E1 on the GALT, which has been still unknown.