Supercapacitor with superior electrochemical properties derived from symmetrical manganese oxide-carbon fiber coated with polypyrrole

A supercapacitor electrode comprising conducting polypyrrole (PPy) coated on manganese oxide-carbon fiber (CNFMnO₂) was successfully synthesized using electrospinning, followed by carbonization and in-situ polymerization. A non-uniform distribution of PPy on the surface of CNFMnO₂ was observed via FESEM analysis. The chemical bonding of CNFMnO₂/PPy and the valence state of manganese were revealed via FTIR, Raman spectroscopy, XRD and XPS measurements. CNFMnO₂/PPy composite possessed high specific capacitance and specific energy of 315.80 Fg^?1 and 13.68 Wh/kg, respectively. In addition, good electrochemical reversibility was proven upon CNFMnO₂/PPy even at higher sweep rate (5–200 mV/s). Moreover, this one-dimensional electrode achieved an excellent long-term cycling stability (82.46%) over 2000 CV cycles with low charge transfer resistance (4.61 Ω). The modification of CNFMnO₂/PPy contributes to good synergistic effects among the material which improve the electrochemical behavior of manganese oxide-based fiber composite for future supercapacitor.     

Functional and antioxidant activity of <Emphasis Type="Italic">Ziziphus jujube</Emphasis> seed protein hydrolysates

Ziziphus jujuba is a medicinal plant with well demonstrated biological functions for which various bioactive compounds except antioxidants peptides from seeds have been reported. Therefore, the aim of this study was to determine antioxidant activity, metal ion chelation and reducing power of Z. jujuba seeds-derived protein hydrolysate. The concentration of protein was 5.72 mg/g in 50 mM Tris-HCl buffer pH 7.5. The solubility of protein was above 90 % at pH 2 and 3, decreased at pH 4 and subsequently increased further with an increase in pH. The seed derived protein showed an excellent solubility and possessed interfacial properties, which were governed by their concentrations. The antioxidant activities of protein hydrolysate were evaluated using various in vitro antioxidant assays. Alcalase, papain and protease hydrolysate shows (8.09, 9.14 and 8.92 µM of TE/g) antioxidant capacity by ABTS and radical scavenging activity (7.21, 17.54 and 8.36) by DPPH. From this study, it was observed that the papain hydrolysate of Ziziphus jujube is a good source of natural antioxidants and peptides with interesting functionalities.     

Antibiotic resistance in food lactic acid bacteria--a review

Antibiotics are a major tool utilized by the health care industry to fight bacterial infections; however, bacteria are highly adaptable creatures and are capable of developing resistance to antibiotics. Consequently, decades of antibiotic use, or rather misuse, have resulted in bacterial resistance to many modern antibiotics. This antibiotic resistance can cause significant danger and suffering for many people with common bacterial infections, those once easily treated with antibiotics. For several decades studies on selection and dissemination of antibiotic resistance have focused mainly on clinically relevant species. However, recently many investigators have speculated that commensal bacteria including lactic acid bacteria (LAB) may act as reservoirs of antibiotic resistance genes similar to those found in human pathogens. The main threat associated with these bacteria is that they can transfer resistance genes to pathogenic bacteria. Genes conferring resistance to tetracycline, erythromycin and vancomycin have been detected and characterized in Lactococcus lactis, Enterococci and, recently, in Lactobacillus species isolated from fermented meat and milk products. A number of initiatives have been recently launched by various organizations across the globe to address the biosafety concerns of starter cultures and probiotic microorganisms. The studies can lead to better understanding of the role played by the dairy starter microorganisms in horizontal transfer of antibiotic resistance genes to intestinal microorganisms and food-associated pathogenic bacteria.     

Simultaneous Determination of Alkaloids in Green Coffee Beans from Ethiopia: Chemometric Evaluation of Geographical Origin

The alkaloid compositions of 99 green coffee (Coffea arabica L.) bean samples comprising eight varieties (Harar, Jimma, Kaffa, Wollega, Sidama, Yirgachefe, Benishangul and Finoteselam) from the major production regions of Ethiopia were investigated. High performance liquid chromatography was applied for the simultaneous determination of four coffee alkaloids in the aqueous extracts of the beans. The limits of detection for the method were established as 13 mg kg^?1 for trigonelline, 7 mg kg^?1 for theobromine, 8.5 mg kg^?1 for caffeine and 4 mg kg^?1 for theophylline in the dry coffee beans. Theophylline was not detected in any of the samples. The determined concentrations (% w/w dry coffee beans) ranged from 0.98 to 1.32 % for trigonelline, 0.0048 to 0.0094 % for theobromine and 0.87 to 1.38 % for caffeine. The concentrations of the alkaloids varied significantly, depending on the geographical origin of the beans. Theobromine was not detected in coffee beans from the East (Harar coffees), and its absence in samples can be used to ascertain whether the coffee originates from this region. Coffee beans from the Northwest were characterized by higher concentrations of caffeine. Application of linear discriminant analysis provided 75 % correct classification of samples into the respective production regions, with a 74 % prediction success rate. The moderate classification efficiency obtained when using alkaloid data demonstrates the potential of using this class of compounds in discriminant models for determination of the geographical origin of green coffee beans from Ethiopia.     

Adsorption behavior of dyes from aqueous solution using agricultural waste: modeling approach

The development of efficient and ecofriendly biosorbent for the removal of dyes is a priority in regions where human health is directly affected by elevated dye concentrations. Biosorption of dyes on shelled Moringa oleifera seed powder (SMOS) was investigated for the removal of methylene blue and Congo red from aqueous solution. Sorption studies led to the standardization of the optimum conditions: dye concentration (25 mg/l), contact time (40 min), particle size (105 μM), and volume (200 ml) at pH 6.5 and 2.5 for the removal of methylene blue (90.27 %) and Congo red (98.52 %). A single layer artificial neural network (ANN) model was developed to simulate the process and predict the removal efficiency of SMOS for the removal of dyes. Different ANN architectures were tested by varying network topology, resulting into an excellent agreement between the experimental data and the predicted values. The Levenberg–Marquardt algorithm was found best of BP algorithms with a minimum mean squared error for training and cross validation as 1.89951E?09 and 0.145001313, respectively.     

Facile synthesis of the porous MnMo6S8 for highly stable pseudocapacitor

Transition metal sulfides are the prominent and leading materials for high-performance energy storage applications. Manganese molybdenum sulfide (MMS) is synthesized using facile hydrothermal method. The electrochemical active sites of the electrode material were enhanced by making the bi-metal sulfides with nanoporous diffusion channels in their crystal structure. The crystalline structure and morphology of the material were studied using X-ray diffraction pattern and high resolution-scanning electron microscope image, respectively. The functional groups present in the material were characterized using Fourier transform infrared spectrometer. MMS-coated nickel foam shows an excellent cycle stability. In 2 M KOH electrolyte, its specific capacity raised to 160% after 10,000 galvanostatic charge discharge (GCD) cycles at the current density of 10 A g^??1 and exhibited a higher specific capacity of 101.3 C g^??1 at 1 A g^??1. After 12,000 GCD cycles, the as-fabricated MMS//MMS symmetric device offers an elevated specific capacity of 228% from its initial value at the current density of 5 A g^??1.

     

Anomalous high pressure behaviour in nanosized rare earth sesquioxides

We report Raman spectroscopic studies of the nanosized rare earth sesquioxides, namely yttrium sesquioxide (Y(2)O(3)), gadolinium sesquioxide (Gd(2)O(3)) and samarium sesquioxide (Sm(2)O(3)), under high pressure. The samples were characterized using x-ray diffraction, Raman spectroscopy and atomic force microscopy at atmospheric pressures. Y(2)O(3) and Gd(2)O(3) were found to be cubic at ambient, while Sm(2)O(3) was found to be predominantly cubic with a small fraction of monoclinic phase. The strongest Raman peaks are observed at 379, 344 and 363?cm(-1), respectively, for Y(2)O(3), Sm(2)O(3) and Gd(2)O(3). All the samples were found to be nanosized with 50-90?nm particle sizes. The high pressures were generated using a Mao-Bell type diamond anvil cell and a conventional laser Raman spectrometer is used to monitor the pressure-induced changes. Y(2)O(3) seems to undergo a crystalline to partial amorphous transition when pressurized up to about 19?GPa, with traces of hexagonal phase. However, on release of pressure, the hexagonal phase develops into the dominant phase. Gd(2)O(3) is also seen to develop into a mixture of amorphous and hexagonal phases on pressurizing. However, on release of pressure Gd(2)O(3) does not show any change and the transformation is found to be irreversible. On the other hand, Sm(2)O(3) shows a weakening of cubic phase peaks while monoclinic phase peaks gain intensity up to about a pressure of 6.79?GPa. However, thereafter the monoclinic phase peaks also reduce in intensity and mostly disordering sets in which does not show significant reversal as the pressure is released. The results obtained are discussed in detail.