Biomass-derived, activated carbon-sulfur composite cathode with a bifunctional interlayer of functionalized carbon nanotubes for lithium-sulfur cells.

Lithium-sulfur (Li-S) cells are emerging as the dominant constituents of the next generation battery technology, offering high theoretical capacity around 1675 mA h g-1 and the additional advantages of low cost and non-toxic nature. Activated carbon, derived from natural resources is being extensively investigated for applications as electrode materials in high power supercapacitors and for making composite electrodes for designing high energy density electrochemical cells. The present work is aimed at introducing the potential of the composite cathode of sulfur with the biomass-derived, steam activated carbon (AC) along with the free-standing and flexible film of carbon nanotubes as the interlayer for designing efficient Li-S cells. The composite obtained by impregnating sulfur particles into the pores of coconut shell derived and steam activated carbon, subjected to efficient acid washing procedures to attain maximum purity, called as the activated carbon-sulfur (ACS) is used as the composite cathode material. The flexible film of acid-functionalized carbon nanotubes termed as the CNTF placed between the composite cathode and the separator material serves as an active interlayer to boost the performance efficiency of the assembled Li-S cells. The ACS composite is synthesized by the solvothermal method, and the flexible CNTF is obtained by solution casting. The Li-S cells assembled with the ACS composite as the active cathode material and the CNTF as the interlayer are found to exhibit quite impressive discharge capacity and cycling stability. These cells deliver an initial discharge capacity of 1562 mA h g-1 at 0.05 C rate and retain 71% of the initial capacity at 1 C rate after 200 cycles. The conducting and the porous network of the ACS helps to enhance the overall electrical conductivity of the sulfur composite cathode and the highly conducting CNTF interlayer accelerates the electrochemical activity taking place in the cell. The interlayer restricts the polysulfides from migrating to the anode and thereby suppresses the polysulfide shuttle phenomenon. The use of the coconut shell derived, steam activated and acid washed carbon for making the composite cathode with sulfur and the CNTF interlayer, obtained by the acid functionalization of carbon nanotubes is a novel approach to realize Li-S cells with high capacity and excellent cycling stability, which has not yet been pursued in detail.

Does elevating silver content in zinc-based glass polyalkenoate cements increase their antibacterial efficacy against two common bacteria using the agar gel diffusion method?

The authors have previously shown that it is possible to incorporate silver into a soda-zinc-silicate glass and subsequently form a glass polyalkenoate cement from it. The objective of the research described herein is to determine if incremental increases in the silver content of these glass polyalkenoate cements will increase their antibacterial efficacy against gram-positive and gram-negative bacteria using the accepted spread plate method. Four glass polyalkenoate cements were formulated; three contained increasing amounts of silver incorporated into them (cements A, B, and C, containing 0.33 mol%, 0.66 mol%, and 0.99 mol% silver, respectively) and a fourth contained no silver, which acted as a control (control cement). The handling properties of the glass polyalkenoate cements were evaluated, where working times were around 2 min and setting times ranged from 1 h 17 min to 2 h 41 min. Inductively coupled plasma atomic emission spectroscopy was employed to determine silver ion release with cement maturation for up to 14 days. The majority of silver ions were released within the first 24 h, with up to 2 mg/L cumulative ion release recorded up to 14 days. The antibacterial properties of the coatings were evaluated against Staphylococcus aureus and Pseudomonas aeruginosa bacteria. The silver-glass polyalkenoate cements exhibited antibacterial effect against both bacterial strains. The maximum inhibition zones recorded against S. aureus was 14.8 mm (SD ± 1.11) and against P. aeruginosa was 20.6 mm (SD ± 0.81). Cement B had a greater antibacterial effect compared to cement A, however, cements B and C had comparable antibacterial effects after 14 days even though cement C contained 0.33 mol% more silver than B. This indicates that by increasing the silver content in these cements, the antibacterial efficacy increases to a point, but there is a threshold where further silver ion release does not increase the antibacterial effect.

Synthesis, characterization and antibacterial activity of azomethine derivatives derived from 2-formylphenoxyacetic acid.

A series of eight new azomethine derivatives were synthesized by reacting 2-formylphenoxyacetic acid with aromatic amines. The chemical structures of these compounds were confirmed by means of 1H-NMR, 13C-NMR, MS and elemental analysis. The compounds were assayed by the disc diffusion method for antibacterial against Staphylococcus aureus and Escherichia coli. Among the compounds tested, 2a, 2b, 2e, 2g and 2h exhibited good antibacterial activity, almost equal to that of Ciprofloxacin used as standard.

Effects of Olax gambecola methanol extract on smooth muscle and rat blood pressure.

A methanol extract of the roots of Olax gambecola induced a biphasic contractile response consisting of a transitory initial rapid contraction (Phase I), followed by a slowly developing sustained increase in basal tone (Phase II) on rat fundus, antrum, guinea pig taenia coli, rabbit jejunum and aorta. The Phase I contraction was abolished by atropine, attenuated significantly by indomethacin and potentiated by physostigmine while the Phase II response was unaffected. Hexamethonium, morphine, serotonin (5-HT) antagonists or desensitization of 5-HT receptors did not alter either the Phase I or the Phase II contractions. Calcium channel blockers and procedures affecting calcium translocation abolished the Phase I contraction while only reducing the Phase II contractions. Transmural electrical stimulation produced contractions of the fundus which were attenuated by the extract. Single bolus injections of extract produced a rapid fall in blood pressure in both normotensive and spontaneously hypertensive rats but intravenous infusion resulted in a sustained fall in blood pressure which was maintained throughout the infusion period. Chronic i.p. administration of extract to spontaneously hypertensive rats reduced blood pressure markedly but did not alter the blood pressure of normotensive animals. The hypotensive response to single bolus injections was abolished by atropine and potentiated by physostigmine. The activity profile of the extract suggests the presence of at least two active principles in the crude extract of Olax gambecola used in this study.