TSL and EPR studies of SrBPO5 doped with CeO2and co-doped with CeO2 and Sm2O3

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) investigations were carried out on gamma irradiated SrBPO₅ samples doped with CeO₂ and co-doped with CeO₂ and Sm₂O₃. On gamma-irradiation at room temperature, BO₃ ^2–, O₂ ^– and O^– radicals were produced. It was seen that the O^– radical ion disappeared in the sample annealed at 500 K. It is proposed that the recombination between trapped electrons and O^– radical ions results in transfer of recombination energy to the impurity centre Ce³⁺ resulting in TSL glow peak at 485 K. In the case of co-doped samples energy transfer occurs between Ce³⁺ to Sm³⁺ resulting in increase in the intensity of glow peak at 485 K.The authors are grateful to Dr. V. K. Manchanda, Head, Radiochemistry Division, BARC for his keen interest and encouragement during the course of this work.     

Acyl vs sulfonyl transfer in N-acyl beta-sultams and 3-oxo-beta-sultams

[reaction: see text] N-Acylsulfonamides usually react with nucleophiles by acyl transfer and C-N bond fission. However, the hydrolysis of N-acyl beta-sultams is a sulfonyl transfer reaction that occurs with S-N fission and opening of the four-membered ring. Similar to other beta-sultams, the N-acyl derivatives are at least 10(6)-fold more reactive than N-acyl sulfonamides. 3-Oxo-beta-sultams are both beta-lactams and beta-sultams but also hydrolyze with preferential S-N bond fission.     

Tuning the energy gap of conjugated polymer zwitterions for efficient interlayers and solar cells

Narrow band gap conjugated polymer zwitterions (CPZs) were synthesized by Suzuki polymerization and characterized to understand their electronic properties and utility as cathode modification layers in solar cells. The polymers were prepared from diketopyrrolopyrrole (DPP) and iso-indigo monomers containing sulfobetaine (SB) pendant groups, benefiting from an ion-rich aqueous phase in the polymerizations. UV–vis absorption spectroscopy revealed the optical energy gap value for the CPZs, ranging from 1.7 to 1.2 eV. Ultraviolet photoelectron spectroscopy of the CPZs as thin layers on Ag metal showed that the pendent zwitterions impart an interfacial dipole (Δ) to the metal and a work function reduction of ∼0.9 eV. OPVs fabricated using a conventional bulk heterojunction (BHJ) device architecture of ITO/PEDOT:PSS/(PTB7:PC₇₁BM)/CPZ/Ag led to dramatic improvements in power conversion efficiency (PCE) values relative to devices having bare Ag cathodes (PCE < 2% for bare Ag vs. 6.7–7.7% for CPZ/Ag). The benzothiadiazole (BT)/DPP polymer denoted as PT₂BTDPPSB gave an optimal PCE of 7.7% in a conventional BHJ OPV device architecture fabricated on a Ag cathode. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 327–336     

Synthesis of the methanesulfonates of α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)emenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol,alpha styryl carbinol antifungal agents

The methanesulfonates of (α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)ethenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol ( 1a, b ) are orally effective α-styryl carbinol derivatives developed for the treatment and prevention of systemic fungal infections. Practical new processes amenable for the large-scale production of these compounds are described. Of note is the selection of dichlorostyrene as a convenient precursor of the styryl portion, modification of a sensitive Grignard addition into a realistic preparative reaction and the use of 1,2,4-triazole simultaneously as a base transfer agent and nucleophile.     

Formation and reactivity of the cyclometallated N-heterocyclic carbene complexes [Ru(NHC)'(dppe)(CO)H

Thermolysis of [Ru(PPh(3))(dppe)(CO)HCl] (dppe = 1,2-bis(diphenylphosphino)ethane) with the N-heterocyclic carbenes I(i)Pr(2)Me(2) (1,3-diisopropyl-4,5-dimethyl-imidazol-2-ylidene), IEt(2)Me(2) (1,3-diethyl-4,5-dimethyl-imidazol-2-ylidene) or ICy (1,3-dicyclohexylimidazol-2-ylidene) gave the cyclometallated carbene complexes [Ru(NHC)'(dppe)(CO)H] (NHC = I(i)Pr(2)Me(2), 4; IEt(2)Me(2), 5; ICy, 6). Dissolution of 4 in CH(2)Cl(2) or CHCl(3) gave the trans-Cl-Ru-P complex [Ru(I(i)Pr(2)Me(2))'(dppe)(CO)Cl] (7), which converted over hours at room temperature to the trans-Cl-Ru-CO isomer 7'. Chloride abstraction from 7 by NaBPh(4) under an atmosphere of H(2) produced the cationic mono-hydride complex [Ru(I(i)Pr(2)Me(2))(dppe)(CO)H][BPh(4)] (9), which could also be formed by protonating 4 with 1 eq HBF(4)·OEt(2). Treatment of 4 with excess HBF(4)·OEt(2) followed by extraction into MeCN produced the dicationic acetonitrile complex [Ru(I(i)Pr(2)Me(2))(dppe)(CO)(NCMe)(2)][BF(4)](2) (10). The structures of 6, 7, 7' and 10 have been determined by X-ray crystallography.     

Raman spectra of biomarkers of relevance to analytical astrobiological exploration: hopanoids, sterols and steranes

The aim of this work is to investigate the viability and potential of three groups of organic compounds as biomarkers in a future robotic analytical exploration of Mars. The three compounds have been identified as suitable candidates for potential biomarkers for extant or extinct life from the terrestrial fossil record. The three groups of compound were all similar in structure, being either tetra- or penta-cyclic compounds. The limits of detection for a sample were also tested to estimate what concentrations it would still be amenable to Raman spectroscopic investigation. This was investigated using both solid mixtures and liquid solutions. The spectra of these compounds are characterised so that they can be added to the Raman database for future Mars missions. This involved identifying functional group characteristics, assigning peaks for each individual sample and characteristic features which would categorise the samples.     

Comparison of Planar and 3‐D Interdigitated Electrodes as Electrochemical Impedance Biosensors

It has been reported that the introduction of a dielectric barrier between adjacent digits of an interdigitated electrode array can improve the sensitivity of the array as an electrochemical impedance biosensor. Here we present an in‐depth analysis of the impedance in planar interdigitated electrodes and 3‐D interdigitated electrodes (with dielectric barriers). The analysis indicates that the planar geometry not only provides lower impedance but also a higher change impedance as a result of molecular immobilization on the electrode array surface.     

Role of radical ions in the thermally stimulated luminescence of uranium doped BaCO3 system

Electron paramagnetic resonance (EPR) studies of -irradiated uranium doped BaCO₃ have shown the formation of CO₃ ^–, CO₂ ^–, O₃ ^– and O₂ ^– ions. Thermally stimulated luminescence (TSL) glow curves of the -irradiated samples in the 300–600 K range have exhibited an intense peak around 360 K and a weak one around 440 K. The trap parameters for these peaks have been determined from TSL data. Spectral studies of the glow have revealed emission around 566, 583 and 590 nm characteristic of the uranate ion. From studies on the thermal stabilities of the radical ions, it has been inferred that the glow peak around 360 K is associated with the thermal destruction of O₂ ^– ion and the peak around 440 K is associated with the thermal destruction of CO₃ ^– ion.     

Analytical discrimination between sources of ginseng using Raman spectroscopy

Ginseng is a widely used medicinal product that grows mainly in Korea, China and America. American ginseng is classified as an endangered species, and so the import and export of this type of ginseng is illegal in certain countries. Due to this restriction it is becoming increasingly important to be able to distinguish between different types of ginseng. FT-Raman spectroscopy has the ability to discriminate between ginseng specimens according to the country of origin and the effects of processing on the ginseng material. The ginsenoside content of ginseng differs in both conformation and concentration depending on the source of the ginseng, which means that ginseng grown in different countries should express unique spectral features. The presence or absence of these features, therefore, could indicate the geographical origin of the sample. Several spectral features were identified for a range of ginsengs, such as a peak at 980 cm(-1) that was only found in Chinese ginseng, and the different wavenumber positions of characteristic ginseng bands near 1600 cm(-1). This indicates that Raman spectroscopy can be used to pinpoint the origin of an unknown ginseng sample and that it would provide a rapid nondestructive analytical technique for formally discriminating between restricted and permitted imports.     

Analysis of testosterone and dihydrotestosterone from biological fluids as the oxime derivatives using high-performance liquid chromatography/tandem mass spectrometry

A sensitive liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method for the simultaneous quantitative analysis of dihydrotestosterone (DHT) and testosterone (T) from biological fluids has been developed. Commercially available deuterated analogues were used as internal standards. Steroids were extracted from serum or testicular fluid with hexane/ethyl acetate, evaporated to dryness, and treated with hydroxylamine to form their oxime derivatives. Upon chromatographic separation, the compounds were quantified using selected reaction monitoring (SRM). For T, the [M+H](+) ion at m/z 304 and the fragment ion at m/z 124 were used as the precursor and product ions. For DHT the ion cluster [M+H+ACN](+) at m/z 347 and the dissociated ion [M+H](+) at m/z 306 were used as the precursor and product ions, respectively. The limits of detectability on-column were in the sub-femtomole range for both compounds and the intra-day coefficient of variation (CV) for analysis from serum was less than 7% for both compounds. Given its high reproducibility, sensitivity, and relative simplicity, this assay should be of use in determining androgen levels in biospecimens, particularly in settings where sample quantity or steroid concentration are low.