System Zn–Rh–O: heat capacity and Gibbs free energy of formation using differential scanning calorimeter and electrochemical cell

The standard molar Gibbs free energy of formation of ZnRh₂O₄(s) has been determined using an oxide solid-state electrochemical cell wherein calcia-stabilized zirconia (CSZ) was used as an electrolyte. The oxide cell can be represented by: . The electromotive force was measured in the temperature range from 943.9 to 1,114.2 K. The standard molar Gibbs energy of formation of ZnRh₂O₄(s) from elements in their standard state using the oxide electrochemical cell has been calculated and can be represented by: . Standard molar heat capacity C ^o _p,m(T) of ZnRh₂O₄(s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges, from 127 to 299 and 307 to 845 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can be represented by: . The heat capacity of ZnRh₂O₄(s), was used along with the data obtained from the oxide electrochemical cell to calculate the standard enthalpy and entropy of formation of the compound at 298.15 K.     

Spectral and X-ray Diffraction Studies of <Emphasis Type="Italic">N</Emphasis>-(2-Nitrophenyl)-5-Phenyl-1,3,4-Oxadiazole-2-Amine

Abstract  

Thiosemicarbazides and their derivatives are well known for their use in biological activity and many applications in pharmaceutical and industrial fields. The cyclization of 1-benzoyl-4-(2-nitrophenyl)-3-thiosemicarbazide (BNPTSC) in dimethylformamide (DMF) medium furnished N-(2-nitrophenyl)-5-phenyl-1,3,4-oxadiazole-2-amine (NPPOA). The chemical structure of the above substituted 1,3,4-oxadiazole has been assigned by IR, mass and X-ray diffraction studies. The XRD studies reveal the presence of four types of hydrogen bonds (N–H···O, N–H···N, C–H···O, C–H···N) in the crystal packing. The crystal system was found to be orthorhombic with a space group Pca2(1) and the unit cell dimensions are: a = 26.873(3) ?, b = 6.0827(7) ?, c = 7.8502(10) ?, α = 90°, β = 90°, γ = 90° and Z = 4.     

Use of laterite for the removal of fluoride from contaminated drinking water

The effects of different operational variables on the mechanistic function of laterite in removal of fluoride have been investigated. Thermodynamic parameters such as free energy change, enthalpy, and entropy of the process, as well as the sorption isotherm, were evaluated. The extent of solute removal is determined by initial solute concentration, operational conditions, laterite dose, and solution pH. For a fixed set of experimental conditions, a model equation is developed from which the percent removal corresponding to each load of fluoride is determined. The mechanism of fluoride adsorption is governed by the zero point charge of laterite and follows a first-order rate equation. pH has a vital role influencing the surface characteristics of laterite. To simulate the flow dynamics, fluoride solution was run through a fixed bed column. The pattern of breakthrough curves for different influent fluoride concentration, pH, and column bed height was characterized. The column efficiency was tested from the bed depth-service time model. The elution of the retained fluoride was studied and the effectiveness of column operation was determined by the retention-elution cycles.     

Synthesis of (−)-lentiginosine, its 8a-epimer and dihydroxylated pyrrolizidine alkaloid from d-glucose

The d-glucose derived α,β-unsaturated ester 5 on 1,2-acetonide deprotection, oxidative diol cleavage followed by treatment with N-benzylamine in the presence of NaBH₃CN undergoes reductive amination and a concomitant intramolecular conjugate addition reaction leading to the formation of dihydroxypyrrolidine-ester 6a and monohydroxypyrrolidine-γ-lactone 6b. Intermediates 6a and 6b were efficiently converted to (−)-lentiginosine 3a, its 8a-epimer 3b, and pyrrolizidine azasugar 4 in good overall yield.     

Multiple layer formation of bovine serum albumin on silver nanoparticles revealed by dynamic light scattering and spectroscopic techniques

It is well known that when nanoparticles (NPs) are exposed to biological fluid, it results into formation of nanoparticle protein corona, which has been the subject of extensive studies for the development of targeted drug delivery. In this work, we demonstrated the dynamic light scattering, fluorescence, and UV-visible spectroscopy as quantitative and qualitative tools to monitor adsorption of BSA protein onto silver nanoparticles (AgNPs). The adsorption resulted in significant gradual increase in average hydrodynamic radius of BSA-AgNP corona from 24 to 35 nm and its attainment of equilibrium point (saturation) that correlated with albumin concentration enables condition for bound and unbound protein adsorption to be interpreted. Using DLS, the dissociation constant (K_D) was obtained for soft corona to be 2.09?±?0.30 μM. The UV-visible and fluorescence spectroscopy results were correlated with DLS. Loss of percent helicity in secondary structure of adsorbed BSA was monitored in both coronas as compared to native protein. Both coronas were found to be biocompatible with RBC membrane. Further, the results of adsorption isotherm model were used to validate the multilayer formation of albumin protein on silver nanoparticles. The obtained results would be relevant in the drug design development for tumor-targeted therapy.

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Coherent crosstalk in passive microring based Optical Networks-on-Chip

Optical Networks-on-Chip (ONoC) is emerging technology for future optical interconnects used in all optical networks. The electrical interconnects face lot of problems due to their inability to support higher data rates used in the System-on-Chip (SoC) technologies. Integrated optical interconnects based on SoC avoid this bottleneck with their support to higher data rates. In this paper for the first time we have studied and analyzed ONoC at physical level for the system performance based on crosstalk, BER, throughput, system frequency, and other related parameters. The investigation of ONoC performance is carried out for the multistage microring optical crossconnect on SoC for coherent WDM signals. The analysis can be used in the design of ultra-high speed photonic routers for reliable data communication and processing. The results show the dependency of a coherent crosstalk on the system frequency of SoC and also illustrate the reduction in throughput with increase in number of WDM signals due to higher probability of packet transmission. Minimum 2 dB signal to noise ratio can be obtained when crosstalk is ?25 dB with 60 wavelengths for probability of packet transmission is 0.5.     

In-situ surface-sensitive X-ray diffraction study on the influence of iodide over the selective electrochemical etching of Cu3Au (111)

During selective etching (dealloying) surface-sensitive X-ray diffraction employing Synchrotron light has been used to in-situ monitor the potential-controlled formation of Au-rich films on the surface of Cu₃Au (111) in iodide-containing electrolytes. Similar to the case in pure sulfuric acid we observed a sequence of structural transformations starting from a well-prepared pristine surface to a porous film consisting of substrate-oriented Au ligaments. Also stacking-reversed ultrathin Au-rich films and Au islands form as intermediate steps but no passive-like behavior was observed in iodide-containing electrolytes, i.e. the surface quickly developed Au ligaments after reaching the Cu dissolution potential. At low overpotentials comparatively coarse Au islands point to a higher mobility of Au/electrolyte interfaces in iodide-containing solutions. At higher overpotentials and also with higher iodide concentrations an epitaxial Cu-iodide precipitate film showed an orientation relation of CuI (111) || CuAu (111) and two azimuthal domains of < ? 2, 2, 0 > || < ? 2, 2, 0 > and < ? 2, 2, 0 > || < 2, ? 2, 0>. This partially dissolution-inhibiting bulk CuI layer is observed to produce a bimodal pore size instead of usually obtained homogeneous porosity. The X-ray data and supporting ex-situ AFM and SEM images show marked differences in the morphology and connectivity of the forming nanoporous Au layer. Precipitation layers are thus suggested to provide means for controlling the nanoporosity for applications of dealloyed films and surfaces.     

Interesting periodic variations in physical and chemical properties of homonuclear diatomic molecules

We carry out a systematic study of various ground state and response properties of homonuclear diatomic molecules (from hydrogen to rubidium, including transition metals) as a function of atomic number of constituent atoms. We perform the ground state and response property calculations by using state of the art density functional theory/time dependent density functional theory. We observe that several properties of homonuclear diatomic molecules show periodic variations along rows and columns of the periodic table. The periodic variations in the ground state properties of diatomic molecules may be explained by the nature and type of the bond that exists between the constituent atoms. Similarly, the periodic variations in the response properties such as static dipole polarizability and strength of the van der Waals interaction between diatomic molecules have been correlated with the variations in metallic/nonmetallic character of the elements along the periodic table. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Light-assisted synthesis of metal oxide hierarchical structures and their catalytic applications

Short reaction times and morphology control in the synthesis of inorganic materials under nonthermal conditions remain a challenge. Herein we report a rapid, self-templating, and nonthermal method based on ultraviolet light to prepare metal oxide hierarchical structures. With this method, the morphology of the metal oxides was controlled readily without using templates.     

Investigation of annealing effects on the structural, magnetic and transport properties of Co/GaAs(0 0 1) thin films

Present paper deals with the structural, magnetic and transport studies of as-deposited as well as annealed Co/GaAs(0 0 1) thin film at different temperatures. The X-ray diffraction measurements show oriented growth of as-deposited Co film in the hcp (0 0 2) direction. However, the sample annealed at higher temperatures shows formation of ternary Co₂GaAs phase at the interface. Corresponding magnetic and transport measurements show decrement in magnetization and resistivity with annealing temperatures. The observed reductions in magnetization and resistivity values are mainly attributed to the formation of ternary Co₂GaAs phase at the interface.