Study of efficiency enhancement in layered geometry of excitonic-plasmonic solar cell

The nano-plasmonic effect on the organic solar cell (OSC) considering different materials, thickness, configurations and geometry has been considered. A theoretical modelling based on exciton-plasmon coupling using first principle approach was done to see the effect of incident photon to current collection efficiency of OSC in the direction to achieve efficient light trapping. For the present numerical model, uniform sized silver Nanoparticle were considered to be embedded in the active layer poly-(4’-(1”, 4”, 7”-trioaoctyl) phenyl) thiophanyl (PEOPT) of OSC. The coupling of local electromagnetic field due to metallic nano-plasmonic antenna resulted in the enhanced overall performance of the OSC. Optimized efficiency calculations suggested that there is nearly 1.6 % of enhancement in the efficiency (IPCE) due to plasmonic coupling to excitonic cell.     

Magical properties of a 2540 km baseline superbeam experiment

Lack of any information on the CP violating phase δCP${\delta }_{\mathit{CP}}$ weakens our ability to determine neutrino mass hierarchy. Magic baseline of 7500 km was proposed to overcome this problem. However, to obtain large enough fluxes, at this very long baseline, one needs new techniques of generating high intensity neutrino beams. In this Letter, we highlight the magical properties of a 2540 km baseline. At such a baseline, using a narrow band neutrino superbeam whose no oscillation event rate peaks around the energy 3.5 GeV, we can determine neutrino mass hierarchy independently of the CP phase. For sin²2θ₁₃?0.05${\sin }^{2}2{\theta }_{13}?0.05$, a very modest exposure of 10 Kiloton-years is sufficient to determine the hierarchy. For 0.02?sin²2θ₁₃?0.05$0.02?{\sin }^{2}2{\theta }_{13}?0.05$, an exposure of about 100 Kiloton-years is needed.     

High pressure effect on structural and mechanical properties of some LnO (Ln=Sm, Eu, Yb) compounds

The structural and mechanical properties of LnO (Ln=Sm, Eu, Yb) compounds have been investigated using a modified interionic potential theory, which includes the effect of Coulomb screening. We predicted a structural phase transition from NaCl (B₁)- to CsCl (B₂)-type structure and elastic properties in LnO compounds at very high pressure. The anomalous properties of these compounds have been correlated in terms of the hybridisation of f-electrons of the rare earth ion with conduction band and strong mixing of f-states of lanthanides with the p-orbital of neighbouring chalcogen ion. For EuO, the calculated transition pressure, bulk modulus and lattice parameter are close to the experimental data. The nature of bonds between the ions is predicted by simulating the ion-ion (Ln-Ln and Ln-O) distances at high pressure. The second order elastic constants along with shear modulus and Young's modulus, elastic anisotropy and Poisson's ratio are also presented for these oxides.     

Applications of ortho-quinone methide intermediates in catalysis and asymmetric synthesis

Ortho-quinone methides are important synthetic intermediates and widely implicated in biological processes. In this Synopsis, recent advances concerning the synthesis and utility of these intermediates are discussed with a particular emphasis on metal-catalyzed formation of quinone methide intermediates. Additionally, applications of these intermediates as partners in asymmetric synthesis will be discussed including methods we have developed that involve the enantioselective Pd-catalyzed formation of ortho-quinone methides and the trapping of aforementioned intermediates with diverse nucleophiles.     

Sorption of Am(III) on natural sediment: experiment and modeling

Release of long-lived radioactivity to the aquatic bodies from various nuclear fuel cycle related operations is of great environmental concern in view of their possible migration into biosphere. This migration is significantly influenced by various factors such as pH, complexing ions present in aquatic environment and sorption of species involving radionuclides on the sediments around the water bodies. ^241/243Am are two major radionuclides which can contribute a great deal to radioactivity for several thousand years. In the present study, ²⁴¹Am sorption on natural sediment collected from site near a nuclear installation in India, has been investigated under the varying conditions of pH (3–10) and ionic strength [I = 0.01–1 M (NaClO₄)]. The sorption of Am increased with pH of the aqueous medium [10% (pH 2) to ~100% (pH 10)], which was explained in terms of the increased negative surface charge on the sediment particles. There was marginal variation in Am(III) sorption with increased ionic strength (within error limits) of the aqueous medium suggesting inner-sphere complexation/sorption process. Sediment was characterized for its elemental composition and structural phases using Energy Dispersive X-Ray (SEM-EDX) and X-Ray Diffraction (XRD) techniques. Zeta-potential measurement at I = 0.1 M (NaClO₄) suggested that Point of Zero Charge (pH_PZC) was ~2, indicating the presence of silica as major component in the sediment. Kurabtov plot using sorption data as a function of pH at fixed I = 0.1 M (NaClO₄) indicated the presence of multiple Am(III) species present on the surface. Potentiometric titration of the suspension indicated the presence of mineral oxide like behavior and assuming a generic nature (≡XOH) for all types of surface sites, protonation–deprotonation constants and total number of sites have been obtained. The sorption data has been modeled using 2-pK Diffuse Double Layer Surface Complexation Model (DDL-SCM). ≡XOAm²⁺ has been identified as the main species responsible for the sorption profile.     

Optically definable reaction-diffusion-driven pattern generation of Ag-Au nanoparticles on templated surfaces

We introduce a new lithographic method for the generation of 2D patterns of composite nanoparticles (NPs) of Ag and Au by taking recourse to combine top-down and bottom-up approaches. Micrometer-scale and submicrometer-scale patterned Ag foils of commercially available compact disks (CDs) and digital versatile disks (DVDs), respectively, were used as templates. The galvanic replacement reaction of Ag by HAuCl(4) in the presence of the dye coatings on the foils led to the formation of patterned NP composites of Ag and Au, in addition to the formation of AgCl. The resultant structures appeared in the form of cross patterns of particles with micrometer and submicrometer dimensions. The AgCl crystals thus formed could be removed by using either a saturated NaCl solution or aqueous ammonia. In addition, AgCl could be converted to Ag by electrochemical reduction, thus generating Ag-coated Au NPs. Interestingly, the digital writing on CDs led to the formation of tertiary imprints on the patterns, based on the original writing patterns. This provided an additional handle in generating hierarchical patterns using light in combination with a chemical reaction diffusion process and the nearly parallel line patterns originally present in commercial CDs. The reactions could be carried out in aqueous solution, and the method does not require any additional curing. Also, the density of patterned particles is scalable on the basis of the choice of the original line patterns as present in CDs and DVDs.     

Analysis of personal care products on model skin surfaces using DESI and PADI ambient mass spectrometry

Two ambient ionisation techniques, desorption electrospray ionisation (DESI) and plasma assisted desorption ionisation (PADI), have been used to analyse personal care products (PCPs) on fixed fibroblast cell surfaces. The similarities and differences between the two techniques for this type of analysis have been explored in various ways. Here, we show the results of DESI and PADI analysis of individual PCP ingredients as well as the analysis of these as complex creams on model skin surfaces, with minimal sample preparation. Typically, organosiloxanes and small molecules were detected from the creams. A study of the morphological damage of the fibroblast cells by the two ionisation techniques showed that for a less than 10% reduction in cell number, acquisition times should be limited to 5 s for PADI, which gives good signal levels; with DESI, the morphological damage was negligible. The operating parameters for the plasma source were optimised, and it was also found that the parameters could be modified to vary the relative intensity of different ions in the mass spectrum.     

Osmotic ensemble methods for predicting adsorption-induced structural transitions in nanoporous materials using molecular simulations

Osmotic framework adsorbed solution theory is a useful molecular simulation method to predict the evolution of structural transitions upon adsorption of guest molecules in flexible nanoporous solids. One challenge with previous uses of this approach has been the estimation of free energy differences between the solid phases of interest in the absence of adsorbed molecules. Here we demonstrate that these free energy differences can be calculated without reference to experimental data via the vibrational density of states of each phase, a quantity that can be obtained from molecular dynamics simulations. We show the applicability of this method through case studies of the swelling behaviors of two representative systems in which swelling upon adsorption of water is of importance: single-walled aluminosilicate nanotube bundles and cesium montmorillonite. The resulting predictions show that the aluminosilicate nanotube bundles swell significantly with increasing interstitial adsorption and that the layer spacing of cesium montmorillonite expands up to about 12.5 A?, giving good agreement with experiments. The method is applicable to a wide range of flexible nanoporous materials, such as zeolites, metal-organic frameworks, and layered oxide materials, when candidate structures can be defined and a force field to describe the material is available.     

Synthesis of Linoleic Acid Capped Copper Nanoparticles and Their Fluorescence Study

Copper nanoparticles have been prepared through the reduction of cupric ions by ethanol with linoleic acid as a capping agent. The morphology and structure of these nanoparticles have been investigated using transmission electron microscopy. The X-diffraction study shows that the nanoparticles are crystalline and mainly composed of face-centered cubic (fcc) copper with a narrow size distribution having an average size of 5 nm. Fluorescence spectra of these copper nanoparticles have been analysed which show two emission peak at 450 nm and 625 nm corresponding to the large energy band and small energy band respectively, when illuminated at 250 nm of an optical source.     

Formation of Mg(OH)<Subscript>2</Subscript> nanowhiskers on LTA zeolite surfaces using a sol–gel method

A facile three step sol–gel-precipitation process is used to synthesize Mg(OH)₂ nanowhiskers on micron-sized zeolite 5A particle surfaces at room temperature. The putative amorphous gelation product, Mg(OH)_n(OR)_2−n, forms first by a controlled hydrolysis and condensation reaction involving magnesium isopropoxide and water, ultimately leading to precipitation to form Mg(OH)₂ structures on the zeolite surface. The optimum conditions for one dimensional Mg(OH)₂ whisker formation are found to be six times the stoichiometric amount of water using 1 M HCl as the catalyst for the sol–gel reaction. The one-dimensional Mg(OH)₂ whiskers have an average diameter of 5–10 nm and length of 50–100 nm. The zeolite micropores are not affected by the Mg(OH)₂ whiskers formed on the surface. The surface roughened zeolite 5A, with a Mg(OH)₂ content of about 9 wt%, showed improved adhesion between the zeolite and the polymer in a mixed-matrix composite membrane.