Synthesis and Mechanism of Composition and Size Dependent Morphology Selection in Nanoparticles of Ag-Cu Alloys Processed by Laser Ablation Under Liquid Medium

We have synthesized Ag-Cu alloy nanoparticles of four different compositions by using the laser ablation technique with the target under aqueous medium. Following this, we report a morphological transition in the nanoparticles from a normal two-phase microstructure to a structure with random segregation and finally a core shell structure at small sizes as a function of Cu concentration. To illustrate the composition dependence of morphology, we report observations carried out on nanoparticles of two different sizes: similar to 5 and similar to 20 nm. The results could be rationalized through the thermodynamic modeling of free energy of phase mixing and wettability of the alloying phases.

Study of liquid fuel transport in a small carburetted engine in the context of cold-start HC emission control

In the present study, a detailed visualization of the transport of fuel film has been performed in a small carburetted engine with a transparent manifold at the exit of the carburettor. The presence of fuel film is observed significantly on the lower half of the manifold at idling, while at load conditions, the film is found to be distributed all throughout the manifold walls. Quantitative measurement of the fuel film in a specially-designed manifold of square cross section has also been performed using the planar laser-induced fluorescence (PLIF) technique. The measured fuel film thickness is observed to be of the order of 1 nun at idling, and in the range of 0.1 to 0.4 mm over the range of load and speed studied. These engine studies are complemented by experiments conducted in a carburettor rig to study the state of the fuel exiting the carburettor. Laser-based Particle/Droplet Image Analysis (PDIA) technique is used to identify fuel droplets and ligaments and estimate droplet diameters. At a throttle position corresponding to idling, the fuel exiting the carburettor is found to consist of very fine droplets of size less than 15 mu m and large fuel ligaments associated with length scales of the order of 500 mu m and higher. For a constant pressure difference across the carburettor, the fuel consists of droplets with an SMD of the order of 30 mu m. Also, the effect of liquid fuel film on the cold start HC emissions is studied. Based on the understanding obtained from these studies, strategies such as manifold heating and varying carburettor main jet nozzle diameter are implemented. These are observed to reduce emissions under both idling and varying load conditions.

Studying electrons on curved surfaces by trapping and manipulating multielectron bubbles in liquid helium

Investigations of two-dimensional electron systems (2DES) have been achieved with two model experimental systems, covering two distinct, non-overlapping regimes of the 2DES phase diagram, namely the quantum liquid phase in semiconducting heterostructures and the classical phases observed in electrons confined above the surface of liquid helium. Multielectron bubbles in liquid helium offer an exciting possibility to bridge this gap in the phase diagram, as well as to study the properties of electrons on curved flexible surfaces. However, this approach has been limited because all experimental studies have so far been transient in nature. Here we demonstrate that it is possible to trap and manipulate multielectron bubbles in a conventional Paul trap for several hundreds of milliseconds, enabling reliable measurements of their physical properties and thereby gaining valuable insight to various aspects of curved 2DES that were previously unexplored.

Numerical modeling of the non-isothermal liquid droplet impact on a hot solid substrate

The heat transfer from a solid phase to an impinging non-isothermal liquid droplet is studied numerically. A new approach based on an arbitrary Lagrangian-Eulerian (ALE) finite element method for solving the incompressible Navier Stokes equations in the liquid and the energy equation within the solid and the liquid is presented. The novelty of the method consists in using the ALE-formulation also in the solid phase to guarantee matching grids along the liquid solid interface. Moreover, a new technique is developed to compute the heat flux without differentiating the numerical solution. The free surface and the liquid solid interface of the droplet are represented by a moving mesh which can handle jumps in the material parameter and a temperature dependent surface tension. Further, the application of the Laplace-Beltrami operator technique for the curvature approximation allows a natural inclusion of the contact angle. Numerical simulation for varying Reynold, Weber, Peclet and Biot numbers are performed to demonstrate the capabilities of the new approach. (C) 2014 Elsevier Ltd. All rights reserved.

Stable Crystalline Salts of Haloperidol: A Highly Water-Soluble Mesylate Salt

Haloperidol, an antipsychotic drug, was screened for new solid crystalline phases using high throughput crystallization in pursuit of solubility improvement. Due to the highly basic nature of the API, all the solid forms with acids were obtained in the form of salts. Eleven crystalline salts in the form of oxalate (1:1), benzoate (1:1), salicylate (1:1 and 1:2), 4-hydroxybenzoate (1:1), 4-hydroxybenzoate ethyl acetate solvate (1:1:1), 3,4-dihydroxybenzoate (1:1), 3,5-dihydroxybenzoate (1:1), mesylate (1:1), besylate (1:1), and tosylate (1:1) salt were achieved. There is an insertion of carboxylate or sulfonate anion into the hydrogen bonding pattern of haloperidol. The salts with the aliphatic carboxylic acids were found to be more prone to form salt hydrates compared with aromatic carboxylate salts. All the salts were subjected to solubility measurement in water at neutral pH. There was no direct correlation observed between the solubility of the salt and its coformer. All the salts are stable at room temperature as well as after 24 h slurry experiment except the oxalate salt, which showed an unusual phase transformation from its hydrated form to the anhydrous form. A structureproperty relationship was examined to analyze the solubility behavior of the solid forms.

Computational Study of the Formation of Short Centrosymmetric N-center dot center dot center dot S Supramolecular Synthon and Related Weak Interactions in Crystalline 1,2,4-Triazoles

A comprehensive analysis of the crystal packing and the energetic features of a series of four biologically active molecules belonging to the family of substituted 4-(benzylideneamino)-3-(4-fluoro-3-phenoxyphenyl)-1H-1,2,4-triazole-5-(4 H)-thione derivatives have been performed based on the molecular conformation and the supramolecular packing. This involves the formation of a short centrosymmetric R-2(2)(8) NH...S supramolecular synthon in the solid state, including the presence of CH...S, CH...O, CH...N, CH...F, CH...Cl, CF...FC, CCl...ClC, and CH...pi intermolecular interactions along with pp stacking to evaluate the role of noncovalent interactions in the crystal. The presence of such synthons has a substantial contribution toward the interaction energy (-18 to -20 kcal/mol) as obtained from the PIXEL calculation, wherein the Coulombic and polarization contribution are more significant than the dispersion contribution. The geometrical characteristics of such synthons favor short distance, and the population of related molecules having these geometries is rare as has been obtained from the Cambridge Structural Database (CSD). Furthermore, their interaction energies have been compared with those present in our molecules in the solid state. The topological characteristics of the NH...S supramolecular synthon, in addition to related weak interactions, CH...N, CH...Cl, CF...FC, and CCl...ClC, have been estimated using the quantum theory of atoms in molecules (QTAIM). In addition, an analysis of the Hirshfeld surface and associated fingerprint plots of these four molecules also have provided a platform for the evaluation of the contribution of different atom...atom contacts, which contribute toward the packing of the molecules in solids.

ZnO/ITO core/shell nanostructure electrodes for future prototype solar cell devices

The impact of indium tin oxide (ITO) layers over vertically aligned zinc oxide nanorods (ZnO NRs) has been investigated to consider ITO nanolayers as transparent conducting oxide electrodes (TCOE) for hierarchical heteronanostructure solar cell devices that have ZnO nanostructures as branches. ZnO/ITO core/shell nanostructures were prepared in two- steps using vapor-liquid-solid and evaporation processes, and further the structures were annealed at various temperatures. Transmission electron microscopic studies show that the as-grown ZnO/ITO structures consist of an amorphous ITO shell on single crystalline ZnO cores, whereas the structures annealed above 300 degrees C consist of a single crystalline ITO shell. ITO layer deposited ZnO NRs exhibit a small red-shift in ZnO near-band-edge emission as well as optical band gap. The electrical measurements carried out on single ZnO/ITO core/shell NR under dark and UV light showed excellent thermionic transport properties. From these investigations it is emphasized that ITO nanolayers could be used as TCO electrodes for prototype ZnO based hierarchical solar cell devices.

Simple three parameter equations for correlating liquid phase compositions in subcritical and supercritical systems

Two Chrastil type expressions have been developed to model the solubility of supercritical fluids/gases in liquids. The three parameter expressions proposed correlates the solubility as a function of temperature, pressure and density. The equation can also be used to check the self-consistency of the experimental data of liquid phase compositions for supercritical fluid-liquid equilibria. Fifty three different binary systems (carbon-dioxide + liquid) with around 2700 data points encompassing a wide range of compounds like esters, alcohols, carboxylic acids and ionic liquids were successfully modeled for a wide range of temperatures and pressures. Besides the test for self-consistency, based on the data at one temperature, the model can be used to predict the solubility of supercritical fluids in liquids at different temperatures. (C) 2014 Elsevier B.V. All rights reserved.

NUMERICAL SIMULATIONS OF LIQUID JET BREAK UP IN A CROSSFLOW

Atomization is the process of disintegration of a liquid jet into ligaments and subsequently into smaller droplets. A liquid jet injected from a circular orifice into cross flow of air undergoes atomization primarily due to the interaction of the two phases rather than an intrinsic break up. Direct numerical simulation of this process resolving the finest droplets is computationally very expensive and impractical. In the present study, we resort to multiscale modelling to reduce the computational cost. The primary break up of the liquid jet is simulated using Gerris, an open source code, which employs Volume-of-Fluid (VOF) algorithm. The smallest droplets formed during primary atomization are modeled as Lagrangian particles. This one-way coupling approach is validated with the help of the simple test case of tracking a particle in a Taylor-Green vortex. The temporal evolution of the liquid jet forming the spray is captured and the flattening of the cylindrical liquid column prior to breakup is observed. The size distribution of the resultant droplets is presented at different distances downstream from the location of injection and their spatial evolution is analyzed.

Electrospun SnSb Crystalline Nanoparticles inside Porous Carbon Fibers as a High Stability and Rate Capability Anode for Rechargeable Batteries

In an electrochemical alloying reaction, the electroactive particles become mechanically unstable owing to large volume changes occurring as a result of high amounts of lithium intake. This is detrimental for long-term battery performance. Herein, a novel synthesis approach to minimize such mechanical instabilities in tin particles is presented. An optimal one-dimensional assembly of crystalline single-phase tin-antimony (SnSb) alloy nanoparticles inside porous carbon fibers (abbreviated SnSb-C) is synthesized for the first time by using the electrospinning technique (employing non-oxide precursors) in combination with a sintering protocol. The ability of antimony to alloy independently with lithium is beneficial as it buffers the unfavorable volume changes occurring during successive alloying/dealloying cycles in Sn. The SnSb-C assembly provides nontortuous (tortuosity coefficient, =1) fast conducting pathways for both electrons and ions. The presence of carbon in SnSb-C completely nullifies the conventional requirement of other carbon forms during cell electrode assembly. The SnSb-C exhibited remarkably high electrochemical lithium stability and high specific capacities over a wide range of currents (0.2-5Ag(-1)). In addition to lithium-ion batteries, it is envisaged that SnSb-C also has potential as a noncarbonaceous anode for other battery chemistries, such as sodium-ion batteries.

Combined toxicity of two crystalline phases (anatase and rutile) of Titania nanoparticles towards freshwater microalgae: Chlorella sp

In view of the increasing usage of anatase and rutile crystalline phases of titania NPs in the consumer products, their entry into the aquatic environment may pose a serious risk to the ecosystem. In the present study, the possible toxic impact of anatase and rutile nanoparticles (individually and in binary mixture) was investigated using freshwater microalgae, Chlorella sp. at low exposure concentrations (0.25, 0.5 and 1 mg/L) in freshwater medium under UV irradiation. Reduction of cell viability as well as a reduction in chlorophyll content were observed due to the presence of NPs. An antagonistic effect was noted at certain concentrations of binary mixture such as (0.25, 0.25), (0.25, 0.5), and (0.5, 0.5) mg/L, and an additive effect for the other combinations, (0.25, 1), (0.5, 0.25), (0.5, 1), (1, 0.25), (1, 0.5), and (1, 1) mg/L. The hydrodynamic size analyses in the test medium revealed that rutile NPs were more stable in lake water than the anatase and binary mixtures at 6 h, the sizes of anatase (1 mg/L), rutile NPs (1 mg/L), and binary mixture (1, 1 mg/L) were 948.83 +/- 35.01 nm, 555.74 +/- 19.93 nm, and 1620.24 +/- 237.87 nm, respectively]. The generation of oxidative stress was found to be strongly dependent on the crystallinity of the nanoparticles. The transmission electron microscopic images revealed damages in the nucleus and cell membrane of algal cells due to the interaction of anatase NPs, whereas rutile NPs were found to cause chloroplast and internal organelle damages. Mis-shaped chloroplasts, lack of nucleus, and starch-pyrenoid complex were noted in binary-treated cells. The findings from the current study may facilitate the environmental risk assessment of titania NPs in an aquatic ecosystem. (C) 2015 Elsevier B.V. All rights reserved.

Gray to transmissive electrochromic switching based on electropolymerized PEDOT-ionic liquid functionalized graphene films

A supporting electrolyte based on lithium perchlorate has been functionalized with graphene (ionic liquid functionalized graphene (IFGR)) by facile electrochemical exfoliation of graphite rods in aq. LiClO4 solution. Poly(3,4-ethylenedioxythiophene) (PEDOT)-IFGR films were prepared by electropolymerization of EDOT monomer with IFGR as supporting electrolyte in ethanol at static potential of 1.5 V. The Raman, SEM, and XPS analysis of PEDOT-IFGR film confirmed the presence of functionalized graphene in the film. The PEDOT-IFGR films showed good electrochemical properties, better ionic and electrical conductivity, significant band gap, and excellent spectroelectrochemical and electrochromic properties. The electrical conductivity of PEDOT-IFGR film was measured as about 3968 S cm(-1). PEDOT-IFGR films at reduced state showed strong and broad absorption in the whole visible region and remarkable absorption at near-IR region. PEDOT-IFGR film showed electrochromic response between transmissive blue and darkish gray at redox potential. The color contrast (%T) between fully reduced and oxidized states of PEDOT-IFGR film is 25 % at lambda (max) of 485 nm. The optical switching stability of PEDOT-IFGR film has retained 80 % of its electroactivity even after 500 cycles.

A Na/MnO2 Primary Cell Employing Poorly Crystalline MnO2

Presently Li/MnO2 is one of the widely used primary battery for a variety of applications. As the global resources for Na are plentiful in relation to those for Li, Na/MnO2 primary battery is expected to be an economical, viable alternate to Li/MnO2 system. But marginal inferior properties of Na/MnO2, which arise due to the differences in properties between Li and Na, are inevitable. In the present work, Na/MnO2 and Li/MnO2 laboratory scale primary cells in non-aquebus electrolytes are assembled and their electrochemical properties are studied in similar experimental conditions. The MnO2 used for these studies is prepared from KMnO4 and it is in amorphous state. The discharge behavior of Na/MnO2 cell is similar to that of Li/MnO2 cell, but with nominal voltage less by about 0.35 V, as expected. The specific capacity of amorphous MnO2 is 300 mAh g(-1) in both Na/MnO2 and Li/MnO2 cells. On heating the as prepared amorphous MnO2 at temperature range 300-800 degrees C, it converts to crystalline ct-MnO2. The capacity of crystalline MnO2 is significantly less than the amorphous MnO2. The results suggest that Na/MnO2 is a viable, economical alternate to Li/MnO2 primary cell. (C) The Author(s) 2015. Published by ECS. All rights reserved.

A predictive approach to CVD of crystalline layers of TMDs: the case of MoS2

Layered transition metal dichalcogenides (TMDs), such as MoS2, are candidate materials for next generation 2-D electronic and optoelectronic devices. The ability to grow uniform, crystalline, atomic layers over large areas is the key to developing such technology. We report a chemical vapor deposition (CVD) technique which yields n-layered MoS2 on a variety of substrates. A generic approach suitable to all TMDs, involving thermodynamic modeling to identify the appropriate CVD process window, and quantitative control of the vapor phase supersaturation, is demonstrated. All reactant sources in our method are outside the growth chamber, a significant improvement over vapor-based methods for atomic layers reported to date. The as-deposited layers are p-type, due to Mo deficiency, with field effect and Hall hole mobilities of up to 2.4 cm(2) V-1 s(-1) and 44 cm(2) V-1 s(-1) respectively. These are among the best reported yet for CVD MoS2.

Unusual Fragility and Cooperativity in Glass-Forming and Crystalline PVDF/PMMA Blends in the Presence of Multiwall Carbon Nanotubes

Poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) are completely miscible below 50 wt % PVDF in the blends. In this work, an attempt was made to understand the fragility/cooperativity relation in glass-forming and crystalline blends of PVDF/PMMA and in the presence of a heteronucleating agent, multiwall carbon nanotubes (CNTs). Hence, three representative blends were chosen: a completely amorphous (10/90 by wt, PVDF/PMMA), on the verge of amorphous miscibility (50/50 by wt, PVDF/PMMA), and crystalline (60/40 by wt, PVDF/PMMA) blends. The intermolecular cooperativity/coupling, fragility, and configurational entropy near the glass transition temperature (T-g) were studied using differential scanning calorimetry (DSC) and broadband dielectric relaxation spectroscopy (DRS). It was observed that the blends with higher concentration of PMMA were more fragile (fragility index m = 141) and those with higher concentration of PVDF were more strong (m = 78). Interestingly, the coupling was less in the glass-forming blends (10/90 by wt, PVDF/PMMA) than the crystalline blends as manifested from DRS. This observation was also supported by DSC measurements which reflected that the cooperative rearranging region (CRR) existed over a smaller length scales in fragile blends as compared to strong blends, possibly due to restricted amorphous mobility. This effect was more prominent in the presence of CNTs, in particular for 50/50 (by wt) and 60/40 (by wt) PVDF/PMMA blends. Further, the configurational entropy, as manifested from DRS, decreased significantly in the strong blends in striking contrast to the fragile blends, supported by DSC, which manifested in an increase in the volume of cooperativity in the strong blends. The higher coupling in the crystalline blends can be attributed to good packing of the amorphous regions. While this is understood for crystalline blends (60/40 by wt, PVDF/PMMA), it is envisaged that enhanced dynamic heterogeneity is accountable for increased coupling in the case of blends which are on the verge of amorphous miscibility (50/50 by wt, PVDF/PMMA). The latter is also supported by broad relaxations near the T-g in DRS. Interestingly, the intermolecular coupling in the blends in the presence of CNTs has reduced, though the potential energy barrier hindering the rearrangement of CRR is lower than the blends without CNTs. In addition, the amorphous packing is not as effective as the blends without CNTs. This is manifested from reduced volume of cooperativity in particular, for 50/50 (by wt) and 60/40 (by wt) blends.