Determination of low concentrations by spectrophotometry: Uranium-thiocyanate system

Errors in the determination of low concentrations by spectrophotometry are investigated with the uranium-thiocyanate system as an example. The reagent blank has significant absorption and measurements are made at 375 nm instead of the λ_max. The error in the intercept of the calibration curve is an important factor in such measurements and the errors involved in the estimation of 1 μg/ml (normal working range 4–40μg/ml) are studied. It is shown that both random and systematic errors associated with the intercept are responsible for observed errors. The two types of errors are resolved by ANOVA (analysis of variance). The error in the measurement of a single value is estimated and compared with measured values for different calibration ranges. It is seen that two factors predominantly influence the error in the measured concentration — the variance from regression and the closeness of the measured value to the mean of the calibration range.     

S-, N- and C-doped titanium dioxide nanoparticles: Synthesis, characterization and redox charge transfer study

Herein we report on the synthesis and characterization of TiO₂ nanomaterials doped with anions like sulfur, carbon and nitrogen. Upon doping, the absorption extends well into the visible region. This shift in the absorption edge is accompanied by a concomitant narrowing of band gap. The resulting anion-doped TiO₂ nanomaterials were characterized by XRD, XPS, elemental analysis, EDAX, TEM, UV-DRS, DC conductivity, AC impedance and cyclic voltammetric studies. XPS confirms the presence of the dopants and the elemental analysis determined the amount of dopants in TiO₂. Electrochemical characterization was carried out by cyclic voltammetry at pHs 2, 6.5 and 10. As against the response of undoped TiO₂, the doped samples show an active electrochemical response indicating an induced charge transfer across the titania/solution interface, thus forming two anodic peaks and a cathodic peak. This interesting and significant observation was understood in terms of band bending due to anion doping as well as to the pH changes in the experimental solutions.     

Efficient total synthesis of naturally occurring anti-TMV compound gramniphenol G

An efficient synthesis of Gramniphenol G identified as 2-(4′-Methoxyphenyl)-7,7-dimethyl-7H-furo[3,2-g]chromene and originally isolated from the plant Arundina gramnifolia belonging to orchidaceae family was accomplished starting from resorcinol. The key step involves the oxidative cyclization of o-vinyl phenol to provide benzofuran moiety.     

Oxo transfer reaction: Dioxido and monooxidovanadium(V) complexes

A dioxidovanadium(V) complex of type [(L_ONOH^?)(VO₂)] (1) was isolated where L_ONOH₂ is a tridentate ONO donor benzhydrazide ligand. 1 undergoes an oxo transfer reaction with triphenylphosphine in presence of 8-hydroxyquinoline (HQ) and affords a monooxidovanadium(V) complex of type [(L_ONO^2?)(VO)(Q^?)] (2). 1 and 2 were substantiated by elemental analyses, ESI-mass, IR, ¹H NMR, ⁵¹V NMR and UV–vis spectra. The molecular geometries of 1 and 2 were authenticated by single crystal X?ray crystallography. UV–vis absorption spectra of 1 and 2 display bands respectively at 325 and 320 nm due to oxido → vanadium(V) charge transfer transitions. 1 exhibit an irreversible cathodic peak at ?0.44 V whereas 2 displays a reversible cathodic wave at ?0.60 V in cyclic voltammogram due to the VO³⁺/VO²⁺ redox couple.     

Diverse Reactivity of bis(Silylene) and bis(Germylene) [LE−EL (E=Si and Ge: L=PhC(NtBu)2)] in the Oxidative Activation of C−F Bond: Si−Si Bond is Retained While the Ge−Ge Bond Is Cleaved

Herein we report the reactions of 3,4,5,6-tetrafluoroterephthalonitrile ( 1 ) with bis(silylene) and bis(germylene) LE−EL [E=Si ( 2 ) and Ge( 3 ): L=PhC(N^tBu)₂)]. The reaction of LSi−SiL (L=PhC(N^tBu)₂) ( 2 ) with two equivalents of 1 resulted in an unprecedented oxidative addition of a C−F bond of 1 leading to disilicon(III) fluoride {L(4-C₈F₃N)FSi−SiF(4-C₈F₃N)L}( 4 ), wherein the Si−Si single bond was retained. In contrast, the reaction of LGe−GeL (L=PhC(N^tBu)₂) ( 3 ) with one equivalent of 1 resulted in the oxidative cleavage of Ge−Ge bond leading to L(4-C₈F₃N₂)Ge ( 5 ) and LGeF ( 6 ). All three compounds ( 4 – 6 ) were characterized by NMR spectroscopy, EI-MS spectrometry, and elemental analysis. X-ray single-crystal structure determination of compound 4 unequivocally established that the Si^III−Si^III bond remains uncleaved.     

Low temperature microwave sintering of yttrium and samarium co-doped ceria solid electrolytes for IT-SOFCs

Nanocrystalline co-doped ceria Ce_0.8Sm_0.2?xY_xO_2?δ solid electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) were synthesized through sol–gel auto-combustion method. The prepared samples were sintered via microwave sintering at 1200 °C for 1 h. The X-ray diffraction analysis of co-doped ceria system reveals formation of the samples with a single-phase cubic fluorite structure. The lattice parameter values were calculated from X-ray diffraction patterns. The calculated crystallite sizes of all the samples were found to be in the range of 17 and 28 nm. Surface morphologies and elemental analysis of all the samples were carried out by using SEM and EDS analysis. The existence of chemical bonding in the samples was studied by FTIR spectroscopy. The presence of oxygen vacancies and evaluation of their concentration in the material was carried out using Raman spectroscopy analysis. Electrical properties of all the samples were analyzed by impedance spectroscopy. It was found that microwave sintered co-doped ceria sample Ce_0.8Sm_0.1Y_0.1O_2?δ exhibits the highest total ionic conductivity with minimum activation energy among all the compositions and conventional sintered sample. Therefore, it can be concluded that the microwave sintered Ce_0.8Sm_0.1Y_0.1O_2?δ sample may be useful as a promising electrolyte material for the IT-SOFCs.     

Ligand directed synthesis of a unprecedented tetragonalbipyramidal copper (II) complex and its antibacterial activity and catalytic role in oxidative dimerisation of 2-aminophenol

In pursuit of the significant contribution of copper ion in different biological processes, this research work describes the synthesis, X-ray structure, Hirshfeld surface analysis, oxidative dimerization of 2-aminophenol and antibacterial activity of a newly designed copper (II)-Schiff base complex, [Cu( L )₂] (1), [Schiff base (H L ) = 2-(2-methoxybenzylideneamino)phenol]. X- ray structural analysis of 1 reveals that the Cu (II) complex crystallizes in a cubic crystal system with Ia-3d space group. The Cu (II) centre adopts an unprecedented tetragonal bipyramidal geometry in its crystalline phase. The Schiff base behaves as a tridentate chelator and forms an innermetallic chelate of first order with Cu (II) ion. The copper (II) complex has been tested in the bio-mimics of phenaxozinone synthase activity in acetonitrile and exhibits good catalytic activity as evident from high turnover number, 536.4 h⁻¹. Electrochemical analysis exhibits the appearance of two additional peaks at −0.15 and 0.46 V for Cu (II) complex in presence of 2-AP and suggests the development of AP⁻/AP^•− and AP^•−/IQ redox couples in solution, respectively. The presence of iminobenzosemiquinone radical at g = 2.057 in the reaction mixture was confirmed by electron paramagnetic resonance and may be considered the driving force for the oxidative dimerisation of 2-AP. The existence of a peak at m/z 624.81 for Cu (II) complex in presence of 2-AP in electrospray ionization mass spectrum ensures that the catalytic oxidation proceeds through enzyme-substrate adduct formation. The copper (II) complex exhibits potential antibacterial properties against few pathogenic bacterial species like Staphylococcus aureus, Enterococcus and Klebsiella pneumonia and scanning electron microscope studies consolidates that destruction of bacterial cell membrane accounts on the development of antibacterial activity.     

Synthesis,characterization and anticorrosive effect of 2-(phenoxy methyl)-5-phenyl-1, 3, 4-oxadiazole for mild steel in 1 M HCl: A combined experimental and computational demonstrations

Synthesis of 2-(phenoxymethyl)-5-phenyl-1, 3, 4-oxadiazole (2POM5PO) and corrosive inhibitive properties studied via weight loss (W.L.) measurement, electrochemical impedance spectroscopy, potentiodynamic polarisation measurements. Scanning Electron Microscope attached with Energy-dispersive X-ray spectroscopic methods were performed to notice morphological changes. These data were observed at a diversified dosage and temperatures the compound for 12 h s immersion of M.S. sheets in 1 M HCl electrolyte through W.L. measurements, furthermore inferred that the inhibition efficiency expanded with slow augmentations in the dosage of each moiety. The maximum inhibitory efficiency was determined which is 88.41% at 300 ppm and 298 K. E.I.S. studies demonstrated that charge transfer resistance increased on concentration increment, confirming each molecule's prohibitive attitude. Potentiodynamic polarisation plots revealed that the compounds displayed mixed type behavior. The Langmuir adsorption model was suited best, proving moiety act as a good corrosion controlling compound in 1 M Hydrochloric acid media. Computational study shows a good correlation with experimental results.     

Universal dynamical onset in water at distinct material interfaces

Interfacial water remains liquid and mobile much below 0 °C, imparting flexibility to the encapsulated materials to ensure their diverse functions at subzero temperatures. However, a united picture that can describe the dynamical differences of interfacial water on different materials and its role in imparting system-specific flexibility to distinct materials is lacking. By combining neutron spectroscopy and isotope labeling, we explored the dynamics of water and the underlying substrates independently below 0 °C across a broad range of materials. Surprisingly, while the function-related anharmonic dynamical onset in the materials exhibits diverse activation temperatures, the surface water presents a universal onset at a common temperature. Further analysis of the neutron experiment and simulation results revealed that the universal onset of water results from an intrinsic surface-independent relaxation: switching of hydrogen bonds between neighboring water molecules with a common energy barrier of ∼35 kJ mol⁻¹.

We demonstrated that the dynamical onset of interfacial water is an intrinsic property of water itself, resulting from a surface independent relaxation process in water with an approximately universal energy barrier of ∼35 kJ mol⁻¹.