Synthesis of multilayered structure of nano-dimensional silica glass/reduced graphene oxide for advanced electrochemical applications.

During the past few years, intensive research has been carried out to design new functional materials for superior electrochemical applications. Due to low storage capacity and low charge transport, silica based glasses have not yet been investigated for their supercapacitive behavior. Therefore, in the present study, a multilayered structure of silica-based nanoglass and reduced graphene oxide has been designed to remarkably enhance the specific capacitance by exploiting the porosity, large surface area, sufficient dangling bonds in the nanoglass and high electrical conductivity of rGO. The charge transport in the composite structure is also investigated to understand the electrochemical properties. It is found that Simmons tunneling or direct tunneling is the dominant mechanism of charge conduction between the graphene layers via the potential barrier of silica nanoglass phase. We believe that this study will open up a new area in the design of glass-based two-dimensional nanocomposites for superior supercapacitor applications.

NiO Nanoparticle Synthesis Using a Triblock Copolymer: Enhanced Magnetization and High Specific Capacitance of Electrodes Prepared from the Powder.

Nickel oxide nanoparticles of diameter ∼21 nm were prepared by a sol-gel method using the triblock copolymer poly(ethylene glycol)-b-(propylene glycol)-b-(ethylene glycol). X-ray photoelectron spectroscopy analysis showed the presence of Ni2+ and Ni3+ ions in the material. The electrical conductivity of this material was due to small polaron hopping between Ni2+ and Ni3+ sites. The magnetization shown by these nanoparticles was much higher than that reported in the literature. This is ascribed to the presence of Ni3+ ions with uncompensated spin moments. Spin-glass behavior was exhibited by the material at 10.7 K. The electrochemical characterization of electrodes comprising of these NiO nanoparticles using cyclic voltammetric measurements showed a specific capacitance value of 810 F/g, the highest reported for this material. These materials will thus form one of the useful multifunctional systems.

Unique trapping of paddlewheel copper(ii) carboxylate by ligand-bound {Cu2} fragments for [Cu6] assembly.

The bridging nature of in situ generated hydroxide ions and carboxylates (RCOO(-); R = CH3, C2H5, CH2Ph) has been utilized to design a new family of [Cu6] coordination complexes: [Cu6(µ3-OH)2(µ-H2L)2(µ1,1,3-O2CCH3)2(µ1,3-O2CCH3)2(µ-ClO4)2](ClO4)2·H2O (), [Cu6(µ3-OH)2(µ-H2L)2(µ1,1,3-O2CC2H5)4(µ-ClO4)2](ClO4)2·2H2O () and [Cu6(µ3-OH)2(µ-H2L)2(µ1,3-O2CCH2Ph)4(ClO4)2](ClO4)2·2H2O (). Tetracarboxylate bridged {Cu2} core units are trapped between two ligand-bound {Cu2(µ-H2L)(µ-OH)}(2+) subunits forming the [Cu6] complexes. The hexanuclear {Cu6(µ3-OH)2(H2L)2(µ-O2CR)4}(4+) cores having six interconnected Cu(II) ions assume a hitherto unknown dumbbell-shaped topology. Detailed characterizations have been done using X-ray crystallography and variable temperature magnetic measurements. For complexes , the dominant coupling constant (J') values between carboxylate bridged copper centers are -36.2 to -45.2 cm(-1) for short CuCu separations of 2.540-2.578 Å. In MeCN solutions all three complexes showed catalytic oxidation of 3,5-di-tert-butyl catechol (3,5-DTBCH2) in air.

Charge Transport in Polypyrrole Nanotubes.

True metallic conductivity in conjugated polymers has been major challenge for the last few years. Heeger and co-workers have reported metallic conductivity in bulk polyaniline film, but the problem of metallic transport in their nanophase still remains unexplored. In the recent past, our group had observed metallic conductivity in single nanotube by studying I-V characteristics using Atomic Force Microscopy. In the present work, Polypyrrole (PPy) nanotubes with variable wall thickness have been synthesized by chemical route. Electrical measurements--current-voltage characteristics as well as variation of resistance over the temperature range from 12 K to 300 K for these nanotubes with variable wall thickness, have also been carried out. The conductivity varies widely from semiconductor to metallic as the wall thickness decreases. Transmission Electron Microscopic study, further, confirms that very aligned and ordered polymer chains are formed due to directional growth in thin walled polypyrrole nanotubes, results in true metallic conductivity with a positive temperature coefficient of resistance over the whole temperature range. To the best of our knowledge, there is no such systematic study reported so far which embraces variation of charge transport characteristics with varying wall thickness of conjugated polymer nanotubes involving both I-V and R-T measurements supplementing each other, which being the main focus of this communication.

Thymine Functionalized Graphene Oxide for Fluorescence "Turn-off-on" Sensing of Hg2+ and I- in Aqueous Medium.

Selective detection of either mercury (Hg2+) or iodide (I-) ion using fluorescence turn-on or turn-off processes is an important area of research. In spite of intensive research, simultaneous detection of both mercury and iodide using fluorescence turn-off-on processes, high sensitivity and theoretical support concerning the mechanisms are still lacking. In the present work, graphene oxide is functionalized by thymine to realize simultaneous detection of both Hg2+ and I- selectively using fluorescence turn-off-on mechanism. Ultra high sensitivity to the extent of ppb level exploiting large surface area of graphene is achieved. DFT calculations also assist to realize the detailed mechanisms involving this PL quenching and also its regain during sensing of these ions in aqueous solution.

Field-induced ferromagnetism and multiferroic behavior in end-on pseudohalide-bridged dinuclear copper(II) complexes with tridentate Schiff base blocking ligands.

Four new end-on pseudohalide-bridged dinuclear copper(II) complexes, [Cu2(L(1))2(N3)2]·DMF (1), [Cu2(L(2))2(N3)2] (2), [Cu2(L(3))2(NCS)2] (3), and [Cu2(L(4))2(N3)2] (4) {where HL(1), HL(2), HL(3), and HL(4) are tridentate N2O donor Schiff bases}, are synthesized and characterized. Complexes 1, 2, and 3 possess π···π stacking interactions, while in addition hydrogen-bonding interactions are present in 1 and 3. However, by contrast, complex 4 contains neither type of interaction. Field-induced long-range ferromagnetic ordering beyond 0.9 T is observed in complexes 1 and 2 due to π···π stacking interactions, while ferroelectric ordering is observed in complexes 1 and 3 due to hydrogen-bonding interactions. Most interestingly, complex 1, which contains both π···π stacking and hydrogen-bonding interactions, shows multiferroic behavior as a result of coupling between the dielectric and magnetic fields with 8% change in the magneto-dielectric effect at room temperature. We believe that from this study will emerge a new class of multiferroic materials.

Highly selective detection of trinitrophenol by luminescent functionalized reduced graphene oxide through FRET mechanism.

Among different nitro compounds, trinitrophenol (TNP) is the most common constituent to prepare powerful explosives all over the world. A few works on the detection of nitro explosives have already been reported in the past few years; however, selectivity is still in its infant stage. As all the nitroexplosives are highly electron deficient in nature, it is very difficult to separate one from a mixture of different nitro compounds by the usual photoinduced electron transfer (PET) mechanism. In the present work, we have used a bright luminescent, 2,6-diamino pyridine functionalized graphene oxide (DAP-RGO) for selective detection of TNP in the presence of other nitro compounds. The major advantage of using this material over other reported materials is not only to achieve very high fluorescence quenching of ∼96% but also superior selectivity >80% in the detection of TNP in aqueous medium via both fluorescence resonance energy transfer and PET mechanisms. Density functional theory calculations also suggest the occurrence of an effective proton transfer mechanism from TNP to DAP-RGO, resulting in this tremendous fluorescence quenching compared to other nitro compounds. We believe this graphene based composite will emerge a new class of materials that could be potentially useful for selective detection, even for trace amounts of nitro explosives in water.

Green banana and pectin improve small intestinal permeability and reduce fluid loss in Bangladeshi children with persistent diarrhea.

To evaluate the effects of green banana and pectin (nondigestible, dietary sources of colonic shortchain fatty acids [SCFA]) on intestinal permeability, 57 boys (5-12 months) with persistent diarrhea (> or = 14 days) were given a week's treatment with a rice-based diet containing either cooked green banana (n = 19), pectin (n = 17), or rice diet alone (n = 21). Intestinal permeability was assessed before and after treatment by giving a lactulose-mannitol (LM) drink and measuring urinary recovery after 5 hr. Treatment with banana significantly (P < 0.05) reduced lactulose recovery, increased mannitol recovery, and decreased the LM ratio, indicating improvement of permeability. Pectin produced similar results. Permeability changes were associated with a 50% reduction in stool weights which correlated strongly (green banana, r2 = 0.84, pectin, r2 = 0.86) with the LM ratio. Green banana-derived and SCFA-mediated stimulation of colonic as well as small bowel absorption is responsible for their antidiarrheal effects. The antidiarrheal effects of green banana and pectin are mediated by improvement of small intestinal permeability in addition to their known colonotrophic effects.

Antioxidants in detoxification of arsenic-induced oxidative injury in rabbits: preliminary results.

To assess the oxidative injuries caused by arsenic toxicity in rabbits and evaluate the detoxifying effects of exogenous antioxidants, we administered arsenic trioxide (3-5 mg/kg/day) in rabbits through a feeding tube for seven days. These rabbits were then treated with a recipe of vitamins, zinc, selenium (VZS) or a plant polyphenol or a placebo for the next seven days. Blood samples were collected from ear vein for spectrophotometric assay of reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARS), and nitrite/nitrate (NOx; index of nitric oxide formation) before arsenic administration, seven days after arsenic administration, and seven days after antioxidant treatment. The total arsenic concentrations in hair and spot urine samples of rabbits before arsenic administration were 0.6 +/- 0.21 microg/g and 34.0 +/- 5.9 microg/L, respectively. Administration of arsenic trioxide significantly increased arsenic concentrations in hair and in urine to 2.8 +/- 0.40 microg/g (p<0.001) and 7372 +/- 1392.0 microg/L (p<0.001), respectively. Arsenic administration to rabbits significantly reduced GSH concentration (post-arsenic, 17.5 +/- 0.81 mg/dL vs. pre-arsenic, 32.0 +/- 0.76 mg/dL, p<0.001), increased TBARS concentration (post-arsenic, 8 +/- 1.1 microM vs. pre-arsenic, 5 +/- 0.7 microM, p<0.05), and NOx concentration (post-arsenic, 465 +/- 38.5 microM vs. pre-arsenic, 320 +/- 24.7 microM, p<0.001) as compared to the pre-arsenic levels. There was a negative correlation between TBARS and GSH concentrations (r=-0.464, p<0.01) and between NOx and GSH concentrations (r=-0.381, p<0.05) of intoxicated rabbits. The recovery of the depleted GSH was significantly greater in the polyphenols (77.0 +/- 12.0%) or VZS (67.0 +/- 17.0%) treatment groups compared with the placebo group (36.0 +/- 7.0%). The decrease in NOx level of arsenic-treated rabbits was significantly greater in polyphenols treatment group than the placebo group (60.0 +/- 9.0% vs. 17.0 +/- 6.0%, p<0.001). These results indicate that arsenic induces toxicity in rabbits associated with an increase in lipid peroxidation. Arsenic toxicity increases nitric oxide production in the body. Exogenous antioxidants such as polyphenols and recipe of vitamins, zinc, and selenium are useful for arsenic detoxification.