Investigations of thermal,optical and electrical properties of Se85In15−xBix glasses and thin films

Journal of Thermal Analysis and Calorimetry - In our present research work, we have investigated the different thermal, optical and electrical properties of Se85In15?xBix alloys in bulk and...     

Enantiopure Calcium Iminophosphonamide Complexes: Synthesis,Photoluminescence, and Catalysis

The synthesis of calcium complexes ligated by three different chiral iminophosphonamide ligands, L- H ( L =[Ph₂P{N(R)CH(CH₃)Ph}₂]), L′ -H ( L′ =[Ph₂P{NDipp}{N(R)CH(CH₃)Ph}]), (Dipp=2,6-ⁱPr₂C₆H₃), and L′′ -H ( L′′ =[Ph₂P{N(R)CH(CH₃)naph}₂]), (naph=naphthyl) is presented. The resulting structures [ L ₂Ca], [ L′ ₂Ca], and [ L′′ ₂Ca] represent the first examples of enantiopure homoleptic calcium complexes based on this type of ligands. The calcium complexes show blue–green photoluminescence (PL) in the solid state, which is especially bright at low temperatures. Whereas the emission of [ L′′ ₂Ca] is assigned to the fluorescence of naphthyl groups, the PL of [ L ₂Ca] and [ L′ ₂Ca] is contributed by long-lived phosphorescence and thermally activated delayed fluorescence (TADF), with a strong variation of the PL lifetimes over the temperature range of 5–295 K. Furthermore, an excellent catalytic activity was found for these complexes in hydroboration of ketones at room temperature, although no enantioselectivity was achieved.     

Application of the Redox-Transmetalation Procedure to Access Divalent Lanthanide and Alkaline-Earth NHC Complexes**

Divalent lanthanide and alkaline-earth complexes supported by N-heterocyclic carbene (NHC) ligands have been accessed by redox-transmetalation between air-stable NHC-AgI complexes and the corresponding metals. By using the small ligand 1,3-dimethylimidazol-2-ylidene (IMe), two series of isostructural complexes were obtained: the tetra-NHC complexes [LnI₂(IMe)₄] (Ln=Eu and Sm) and the bis-NHC complexes [MI₂(IMe)₂(THF)₂] (M=Yb, Ca and Sr). In the former, distortions in the NHC coordination were found to originate from intermolecular repulsions in the solid state. Application of the redox-transmetalation strategy with the bulkier 1,3-dimesitylimidazol-2-ylidene (IMes) ligand yielded [SrI₂(IMes)(THF)₃], while using a similar procedure with Ca metal led to [CaI₂(THF)₄] and uncoordinated IMes. DFT calculations were performed to rationalise the selective formation of the bis-NHC adduct in [SrI₂(IMe)₂(THF)₂] and the tetra-NHC adduct in [SmI₂(IMe)₄]. Since the results in the gas phase point towards preferential formation of the tetra-NHC complexes for both metal centres, the differences between both arrangements are a result of solid-state effects such as slightly different packing forces.     

On exponential stability of second order delay differential equations

We propose a new method for studying stability of second order delay differential equations. Results we obtained are of the form: the exponential stability of ordinary differential equation implies the exponential stability of the corresponding delay differential equation if the delays are small enough. We estimate this smallness through the coefficients of this delay equation. Examples demonstrate that our tests of the exponential stability are essentially better than the known ones. This method works not only for autonomous equations but also for equations with variable coefficients and delays.     

Pullulan Encapsulation of Labile Biomolecules to Give Stable Bioassay Tablets

A simple and inexpensive method is reported for the long‐term stabilization of enzymes and other unstable reagents in premeasured quantities in water‐soluble tablets (cast, not compressed) made with pullulan, a nonionic polysaccharide that forms an oxygen impermeable solid upon drying. The pullulan tablets dissolve in aqueous solutions in seconds, thereby facilitating the easy execution of bioassays at remote sites with no need for special reagent handling and liquid pipetting. This approach is modular in nature, thus allowing the creation of individual tablets for enzymes and their substrates. Proof‐of‐principle demonstrations include a Taq polymerase tablet for DNA amplification through PCR and a pesticide assay kit consisting of separate tablets for acetylcholinesterase and its chromogenic substrate, indoxyl acetate, both of which are highly unstable. The encapsulated reagents remain stable at room temperature for months, thus enabling the room‐temperature shipping and storage of bioassay components.     

Enhancement of Stress Tolerance in the Polyhydroxyalkanoate Producers without Mobilization of the Accumulated Granules

Poly(3-hydroxybutyrate) [P(3HB)], a polymer belonging to the polyhydroxyalkanoate (PHA) family, is accumulated by numerous bacteria as carbon and energy storage material. The mobilization of accumulated P(3HB) is associated with increased stress and starvation tolerance. However, the potential function of accumulated copolymer such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] remained unknown. In this study, Delftia acidovorans DS 17 was used to evaluate the contributions of P(3HB) and P(3HB-co-3HV) granules during simulated exogenous carbon deprivation on cell survival by transferring cells with PHAs to carbon-free mineral salt medium supplemented with 1 % (w/v) nitrogen source. By mobilizing the intracellular P(3HB) and P(3HB-co-3HV) at 11 and 40 mol% 3HV compositions, the cells survived starvation. Surprisingly, D. acidovorans containing P(3HB-co-94 mol% 3HV) also survived although the mobilization was not as effective. Similarly, recombinant Escherichia coli pGEM-T::phbCAB _Cn (harboring the PHA biosynthesis genes of Cupriavidus necator) containing P(3HB) granules had a higher viable cell counts compared to those without P(3HB) granules but without any P(3HB) mobilization when exposed to oxidative stress by photoactivated titanium dioxide. This study provided strong evidence that enhancement of stress tolerance in PHA producers can be achieved without mobilization of the previously accumulated granules. Instead, PHA biosynthesis may improve bacterial survival via multiple mechanisms.     

Dye sensitization of a large band gap semiconductor by an iron(III) complex

The Fe(III) complex, [Fe^III(HQS)₃] (HQS = 8-hydroxyquinoline-5-sulfonic acid), is found to effect sensitization of the large band gap semiconductor, TiO₂. The role of interfacial electron transfer in sensitization of TiO₂ nanoparticles by surface adsorbed [Fe^III(HQS)₃] was studied using femtosecond time scale transient absorption spectroscopy. Electron injection has been confirmed by direct detection of the electron in the conduction band. A TiO₂-based dye-sensitized solar cell (DSSC) was fabricated using [Fe^III(HQS)₃] as a sensitizer, and the resulting DSSC exhibited an open-circuit voltage value of 425 mV. The value of the short-circuit photocurrent was found to be 2.5 mA/cm². The solar to electric power conversion efficiency of the [Fe^III(HQS)₃] sensitized TiO₂-based DSSC device was 0.75 %. The results are discussed in the context of sensitization of TiO₂ by other Fe(II)-dye complexes.     

Kinetics and thermoluminescence glow curve study of Ba2MgSi2O7:Eu3+, Dy3+

This paper reports thermoluminescence glow curves of Eu³⁺, Dy³⁺-doped Ba₂MgSi₂O₇ phosphor for different UV exposure times. Kinetic data were evaluated by the peak-shape method. The glow curves shift toward higher intensity with increasing exposure time to UV at 365 nm. When the heating rate was 5 °C s^?1, peaks were observed at 101.76, 109.69, 102.67, and 104.05 °C, respectively, after UV exposure for 5, 10, 15, and 20 min. The glow peaks are indicative of second-order kinetics. Different kinetic data, i.e. trap depth, order of kinetics, activation energy, and frequency factor were also calculated. To evaluate the persistence characteristics of the luminescence of the phosphor, the lifetime of the charge in the trap was calculated; it was 348, 660, 368, and 428 s for UV exposure of 5, 10, 15, and 20 min, which indicates the luminescence of the phosphor is persistent.     

Correction to: Tissue free water tritium (TFWT) and organically bound tritium (OBT) in marine eco system at Tarapur on the west coast of India

Journal of Radioanalytical and Nuclear Chemistry - The original publication of the article contains errors in the text and Tables 3, 4 and 5. The corrected text and tables are provided in...