Self-Assembled Functionalized Graphene Nanoribbons from Carbon Nanotubes

Graphene nanoribbons (GNR) were generated in ethanol solution by unzipping pyrrolidine-functionalized carbon nanotubes under mild conditions. Evaporation of the solvent resulted in regular few-layer stacks of graphene nanoribbons observed by transmission electron microscopy (TEM) and X-ray diffraction. The experimental interlayer distance (0.49–0.56 nm) was confirmed by computer modelling (0.51 nm). Computer modelling showed that the large interlayer spacing (compared with graphite) is due to the presence of the functional groups and depends on their concentration. Stacked nanoribbons were observed to redissolve upon solvent addition. This preparation method could allow the fine-tuning of the interlayer distances by controlling the number and/or the nature of the chemical groups in between the graphene layers.     

Waveguiding effect in 2D metal–dielectric–metal grating structure

We have studied the waveguiding effect in a 2D metal–dielectric–metal (MDM) grating structure formed on a quartz substrate. The grating was first formed via e-beam lithography and subsequently covered by Ag/MgF₂/Ag MDM films. At a pitch of 300 nm in both x- and y-directions, low reflectance and transmittance were observed in the UV–VIS range, indicating efficient coupling of normal incident light into waveguiding modes. As evidence, we measured the spectrum of the waveguide from the edge, and the bandwidth of the spectrum was as narrow as ∼74 nm. The bandwidth of the waveguide can be further improved by increasing the MDM stack number. In addition, the bandwidth can also be widened by increasing the pitch of the structure. The physical mechanism underlying the phenomena was analyzed and experimentally confirmed. Such effect could be useful in many applications, such as DFB lasers, solar cells, waveguides, and light emitting devices.     

The use of solution microcalorimetry to evaluate chemically modified fish scales as a viable adsorbent for heavy metals

Here, we report for the first time the direct and simultaneous determination of kinetic and energetic parameters of Cr(VI) sorption on chemically modified fish scales (GA-scale) using solution microcalorimetry. Characterization has suggested that electrostatic interactions between scales collagen positive charges and chromate negative charges constitute the majority of the interactions. The microcalorimetric kinetic data of Cr(VI) sorption on GA-scale were successful adjusted to a three-parameter exponential function. The enthalpies of Cr(VI) sorption on GA-scale are highly exothermic (from −226.43 to −183.79 kJ mol⁻¹), and Cr(VI) interaction energies decrease as initial Cr(VI) in solution increases. The kinetic and thermodynamic from solution microcalorimetry results suggest that the interactions GA-scale/Cr(VI) occur mainly by surface reactions. The maximum adsorption capacity of GA-scale for Cr(VI) was found to be comparable with some commercial adsorbent samples.     

Cytotoxic cardenolide and sterols from Calotropis gigantea

The dichloromethane extract from the leaves of Calotropis gigantea Linn. was strongly cytotoxic against non-small cell lung carcinoma (A549), colon carcinoma (HCT 116) and hepatocellular carcinoma (Hep G2), and non toxic to Chinese hamster ovary (AA8). The extract afforded uscharin (1), 3,5,8-trihydroxy-24-methylcholest-6,22-diene (2), a mixture of (24R)-3beta-hydroxy-24-ethylcholest-5-en-7-one (3a) and 6beta-hydroxy-24-ethylcholest-4,22-dien-3-one (3b), and another mixture of (24R)-24-ethylcholest-4-en-3-one (4a) and (24S)-24-ethylcholest-4,22-dien-3-one (4b). Cardenolide 1 exhibited extreme toxicity to A549, HCT 116 and Hep G2 with IC50 values of 0.003 microg/mL, 0.013 microg/mL, and 0.018 microg/mL, respectively, while sample 3 exhibited an IC50 of 1.35 microg/mL, 4.46 microg/mL, and 3.83 microg/mL, respectively.     

Screening of Pectinase-Producing Microorganisms with Polygalacturonase Activity

The aim of this work was to perform the screening of microorganisms, previously isolated from samples of agro-industrial waste and belonging to the culture collection of our laboratory, able to produce polygalacturonases (PG). A total of 107 microorganisms, 92 newly isolated and 15 pre-identified, were selected as potential producers of enzymes with PG activity. From these microorganisms, 20 strains were able to synthesize PG with activities above 3 U mL⁻¹. After the kinetic study, the enzyme activity was increased up to 13 times and the microorganism identified as Aspergillus niger ATCC 9642 and the newly isolated W23, W43, and D2 (Penicillium sp.) after 24 h of fermentation led to PG activities of 30, 41, 43, and 45 U mL⁻¹, respectively. The RAPD analysis demonstrated that the selected strains differs genetically, indicating that no duplication of strains among them in the experiments for polygalacturonases production was verified.     

Palladium-catalyzed direct cross-coupling of potassium styryltrifluoroborates and benzoyl chlorides—a one step method for chalcone synthesis

A direct cross-coupling reaction of benzoyl chlorides and potassium styryltrifluoroborates to the corresponding α,β-unsaturated aromatic ketones in the presence of PdCl₂(d^tbpf) catalyst under microwave heating is developed.     

Kinetics of interaction of hardened oil-well cement slurries with acidic solutions from isothermal heat-conduction calorimetry

The kinetics of interaction of hydrochloric acid with oil-well cement slurries treated with the silane coupling agents, tetraethyl orthosilicate, 3-(trimethoxysilyl)-1-propanethiol and 3-(chloropropyl)-trimethoxysilane have been investigated isothermal heat-conduction calorimetry at 298.15 K. The Avrami kinetic model gives a better fit to the experimental data than the traditional Lagergren kinetics models. A pore diffusion model suggests acid diffusion only for the standard slurry. The results indicate that isothermal heat-conduction calorimetry is suitable to evaluate the protective role of silane coupling agents on hardened oil-well cement slurries.