Robust, metallic Pd17Se15 and Pd7Se4 phases from a single source precursor and their use as counter electrodes in dye sensitized solar cells

Thin films of conducting palladium selenide phases (Pd17Se15 and Pd7Se4) are prepared using a single source molecular precursor by thermolysis. Varying the mole ratios of palladium and selenium precursors results in palladium organo-selenolate complexes which on thermolysis at different temperatures yield Pd17Se15 and Pd7Se4 phases that are very stable and adherent to the substrate. The organo-selenolate complexes are characterized using small angle XRD, Se-77 NMR and thermogravimetric analysis (TGA). The palladium selenide films are characterized by various techniques such as XRD, XPS, TEM and SEM. Electrical conductivities of the films are determined using the four probe method. The strong adherence of the films to glass substrates coupled with high corrosion resistant behavior towards strong acid and alkaline environments render them to be very effective as electrocatalysts. The catalytic activity towards the I-3(-)/I- redox couple, which is an important reaction in the regeneration of the dye in a dye-sensitized solar cell, is studied. Between the two phases, the Pd17Se15 film shows superior activity as the counter electrode for dye sensitized solar cells with a photocurrent conversion efficiency of 7.45%.

Ag-doped hydroxyapatite as efficient adsorbent for removal of Congo red dye from aqueous solution: Synthesis, kinetic and equilibrium adsorption isotherm analysis

In the present study a versatile and efficient adsorbent with high adsorption capacity for adsorption of Congo red dye in aqueous solution at ambient temperature without adjusting any pH is presented over the Ag modified calcium hydroxyapatite (CaHAp). CaHAp and Ag-doped CaHAp materials were synthesized using facile aqueous precipitation method. The physico-chemical properties of the materials were determined by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Transmission electron microscopy (TEM), UV-Visible spectroscopy, N-2 physisorption and acidity was determined by n-butylamine titration and pyridine adsorption methods. XRD analysis confirmed all adsorbents exhibit hexagonal CaHAp structure with P6(3)/m space group. TEM analysis confirms the rod like morphology of the adsorbents and the average length of the rods were in the range of 40-45 nm. Pyridine adsorption results indicate increase in number of Lewis acid sites with Ag doping in CaHAp. Adsorption capacity of CaHAp was found increased with Ag content in the adsorbents. Ag (10): CaHAp adsorbent showed superior adsorption performance among all the adsorbents for various concentrations of Congo red (CR) dye in aqueous solutions. The amount of CR dye adsorbed on Ag (10): CaHAp was found to be 49.89-267.81 mg g(-1) for 50-300 ppm in aqueous solution. A good correlation between adsorption capacity and acidity of the adsorbents was observed. The adsorption kinetic data of adsorbents fitted well with pseudo second-order kinetic model with correlation coefficients ranged from 0.998 to 0.999. The equilibrium adsorption data was found to best fit to the Langmuir adsorption isotherm model. (C) 2015 Elsevier Inc. All rights reserved.

Primates, Provisioning and Plants: Impacts of Human Cultural Behaviours on Primate Ecological Functions

Human provisioning of wildlife with food is a widespread global practice that occurs in multiple socio-cultural circumstances. Provisioning may indirectly alter ecosystem functioning through changes in the eco-ethology of animals, but few studies have quantified this aspect. Provisioning of primates by humans is known to impact their activity budgets, diets and ranging patterns. Primates are also keystone species in tropical forests through their role as seed dispersers; yet there is no information on how provisioning might affect primate ecological functions. The rhesus macaque is a major human-commensal species but is also an important seed disperser in the wild. In this study, we investigated the potential impacts of provisioning on the role of rhesus macaques as seed dispersers in the Buxa Tiger Reserve, India. We studied a troop of macaques which were provisioned for a part of the year and were dependent on natural resources for the rest. We observed feeding behaviour, seed handling techniques and ranging patterns of the macaques and monitored availability of wild fruits. Irrespective of fruit availability, frugivory and seed dispersal activities decreased when the macaques were provisioned. Provisioned macaques also had shortened daily ranges implying shorter dispersal distances. Finally, during provisioning periods, seeds were deposited on tarmac roads that were unconducive for germination. Provisioning promotes human-primate conflict, as commensal primates are often involved in aggressive encounters with humans over resources, leading to negative consequences for both parties involved. Preventing or curbing provisioning is not an easy task as feeding wild animals is a socio-cultural tradition across much of South and South-East Asia, including India. We recommend the initiation of literacy programmes that educate lay citizens about the ill-effects of provisioning and strongly caution them against the practice.

Surface modification of titania aerogel films by oxygen plasma treatment for enhanced dye adsorption

Titania aerogels were synthesized by sol-gel route followed by ambient pressure subcritical drying technique. The aerogels synthesized in the present work possess a maximum surface area of 252 m(2)/g. The pore size distribution is between 2 and 30 nm which confirms their mesoporosity. The oxygen plasma treatment on titania aerogel thin films improved the surface area up to 273 m(2)/g and produced additional hydrophilic groups on the surface. It is confirmed by BET surface area, XPS and thermal analysis in conjunction with dye adsorption studies. After plasma treatment the dye adsorption capacity was increased 2.5 times higher than that of untreated aerogel film. The increased surface area and the hydrophilic groups generated on the titania aerogel surface during plasma treatment are responsible for enhanced dye adsorption. The overall nanoporous morphology of titania aerogel is preserved after plasma treatment. (C) 2015 Elsevier B.V. All rights reserved.

Hetero-atom Doped Carbon Nanotubes for Dye Degradation and Oxygen Reduction Reaction

We report the synthesis of nitrogen doped vertically aligned multi-walled (MWNCNTs) carbon nanotubes by pyrolysis and its catalytic performance for degradation of methylene blue (MB) dye & oxygen reduction reaction (ORR). The degradation of MB was monitored spectrophotometrically with time. Kinetic studies show the degradation of MB follows a first order kinetic with rate constant k=0.0178 min(-1). The present rate constant is better than that reported for various supported/non-supported semiconducting nanomaterials. Further ORR performance in alkaline media makes MWNCNTs a promising cost-effective, fuel crossover tolerance, metal-free, eco-friendly cathode catalyst for direct alcohol fuel cell.

Photoelectrochemical degradation of eosin yellowish dye on exfoliated graphite-ZnO nanocomposite electrode

In the quest for harnessing more power from the sun for water treatment by photoelectrochemical degradation, we prepared a novel photoanode of exfoliated graphite (EG)-ZnO nanocomposite. The nanocomposite was characterised by X-ray diffractometry, energy dispersive spectroscopy, Brunauer-Emmett-Teller surface area analyser, thermal gravimetric analyser, and X-ray photoelectron spectroscopy. The EG-ZnO nanocomposite was fabricated into a photoanode and applied for the photoelectrochemical degradation of 0.1 x 10(-4) M eosin yellowish dye in 0.1 M Na2SO4 under visible light irradiation. The degradation was monitored with a visible spectrophotometer. The photoelectrochemical degradation process resulted in enhanced degradation efficiency of ca. 93 % with kinetic rate of 11.0 x 10(-3) min(-1) over photolysis and electrochemical oxidation processes which exhibited lower degradation efficiencies of 35 and 40 % respectively.

Macroporous three-dimensional graphene oxide foams for dye adsorption and antibacterial applications

Several reports illustrate the wide range applicability of graphene oxide (GO) in water remediation. However, a few layers of graphene oxide tend to aggregate under saline conditions thereby reducing its activity. The effects of aggregation can be minimized by having a random arrangement of GO layers in a three dimensional architecture. The current study emphasizes the potential benefits of highly porous, ultralight graphene oxide foams in environmental applications. These foams were prepared by a facile and cost effective lyophilization technique. The 3D architecture allowed the direct use of these foams in the removal of aqueous pollutants without any pretreatment such as ultrasonication. Due to its macroporous nature, the foams exhibited excellent adsorption abilities towards carcinogenic dyes such as rhodamine B (RB), malachite green (MG) and acriflavine (AF) with respective sorption capacities of 446, 321 and 228 mg g(-1) of foam. These foams were also further investigated for antibacterial activities against E. coli bacteria in aqueous and nutrient growth media. The random arrangement of GO layers in the porous foam architecture allowed it to exhibit excellent antibacterial activity even under physiological conditions by following the classical wrapping-perturbation mechanism. These results demonstrate the vast scope of GO foam in water remediation for both dye removal and antibacterial activity.

Of plants and pikas: evidence for a climate-mediated decline in forage and cache quality

Background: Animals that hoard food to mediate seasonal deficits in resource availability might be particularly vulnerable to climate-mediated reductions in the quality and accessibility of food during the caching season. Central-place foragers might be additionally impacted by climatic constraints on their already restricted foraging range. Aims: We sought evidence for these patterns in a study of the American pika (Ochotona princeps), a territorial, central-place forager sensitive to climate. Methods: Pika food caches and available forage were re-sampled using historical methods at two long-term study sites, to quantify changes over two decades. Taxa that changed in availability or use were analysed for primary and secondary metabolites. Results: Both sites trended towards warmer summers, and snowmelt trended earlier at the lower latitude site. Graminoid cover increased at each site, and caching trends appeared to reflect available forage rather than primary metabolites. Pikas at the lower latitude site preferred species higher in secondary metabolites, known to provide higher-nutrient winter forage. However, caching of lower-nutrient graminoids increased in proportion with graminoid availability at that site. Conclusions: If our results represent trends in climate, cache quality and available forage, we predict that pikas at the lower latitude site will soon face nutritional deficiencies.

Accurate sodium bisulfite sequencing in plants.

DNA cytosine methylation is a conserved epigenetic modification frequently correlating with transcriptional silencing in a wide variety of eukaryotic organisms. Sodium bisulfite treatment of DNA converts unmethylated cytosine to uracil, while 5-methylated cytosine is protected. We describe techniques that ensure reliable sequencing data following sodium bisulfite conversion and to avoid common pitfalls such as amplification of unconverted DNA and inclusion of sibling clones.

Meiosis in flowering plants and other green organisms.

Sexual eukaryotes generate gametes using a specialized cell division called meiosis that serves both to halve the number of chromosomes and to reshuffle genetic variation present in the parent. The nature and mechanism of the meiotic cell division in plants and its effect on genetic variation are reviewed here. As flowers are the site of meiosis and fertilization in angiosperms, meiotic control will be considered within this developmental context. Finally, we review what is known about the control of meiosis in green algae and non-flowering land plants and discuss evolutionary transitions relating to meiosis that have occurred in the lineages giving rise to the angiosperms.

High-resolution TEM characterization of ZnO core-shell nanowires for dye-sensitized solar cells

Recently ZnO nanowire films have been used in very promising and inexpensive dye-sensitized solar cells (DSSC). It was found that the performance of the devices can be enhanced by functionalising the nanowires with a thin metal oxide coating. This nm-scale shell is believed to tailor the electronic structure of the nanowire, and help the absorption of the dye. Core-shell ZnO nanowire structures are synthesised at low temperature (below 120°C) by consecutive hydrothermal growth steps. Different materials are investigated for the coating, including Mg, Al, Cs and Zr oxides. High resolution TEM is used to characterise the quality of both the nanowire core and the shell, and to monitor the thickness and the degree of crystallisation of the oxide coating. The interface between the nanowire core and the outer shell is investigated in order to understand the adhesion of the coating, and give valuable feedback for the synthesis process. Nanowire films are packaged into dye-sensitised solar cell prototypes; samples coated with ZrO2 and MgO show the largest enhancement in the photocurrent and open-circuit voltage and look very promising for further improvement. © 2010 IOP Publishing Ltd.