Aza crown ether appended hetarylazo dye-single molecular dual analyte chemosensor for Hg2+ and Pb2+

A hetarylazo dye appended with an aza crown ether detects and discriminates Hg(2+) and Pb(2+) from each other by immediate visual observation, significant from an 'on-site' evaluation point of view. It is accompanied by absorption based changes and is convincingly established from (1)H NMR, TD-DFT and electrochemical studies.     

Detection of pathogenic gram negative bacteria using infrared thermography

Detection of viable bacteria is of prime importance in all fields of microbiology and biotechnology. Conventional methods of enumerating bacteria are often time consuming and labor-intensive. All living organisms generate heat due to metabolic activities and hence, measurement of heat energy is a viable tool for detection and quantification of bacteria. In this article, we employ a non-contact and real time method – infrared thermography (IRT) for measurement of temperature variations in four clinically significant gram negative pathogenic bacteria, viz. Vibrio cholerae, Vibrio mimicus, Proteus mirabilis and Pseudomonas aeruginosa. We observe that, the energy content, defined as the ratio of heat generated by bacterial metabolic activities to the heat lost from the liquid medium to the surrounding, vary linearly with the bacterial concentration in all the four pathogenic bacteria. The amount of energy content observed in different species is attributed to their metabolisms and morphologies that affect the convection velocity and hence heat transport in the medium.     

Chain Folding Controlled by an Isomeric Repeat Unit: Helix Formation versus Random Aggregation in Acetylene‐Bridged Carbazole–Bipyridine Co‐Oligomers

An unprecedented, positional effect of the isomeric repeat unit on chain folding in donor–acceptor‐linked oligomers, which contain alternating bipyridine and carbazole moieties that are connected through an acetylinic linkage, is reported. 4,4′‐Linked oligomer 1 adopts an intrachain helical conformation (CD‐active) in CHCl₃/MeCN (20:80 v/v), whereas oligomer 2 , which contains an isomeric 6,6′‐linkage, forms interchain randomly coiled aggregates (CD‐inactive). The substitution position plays a significant role in controlling the variations in electronic effects and dipole moments around the bipyridyl moiety, which are responsible for this observed phenomenon. Two model compounds of oligomers 1 and 2 ( 3 and 4 , respectively) were prepared and their properties were compared. A systematic investigation of the photophysical and CD properties of these structures, as well as theoretical studies, support our conclusions.     

Determination of 3-hydroxy pterocarpan, a novel osteogenic compound in rat plasma by liquid chromatography-tandem mass spectrometry: application to pharmacokinetics study

A rapid, sensitive and selective LC‐MS/MS method for the quantitative analysis of 3‐hydroxy pterocarpan (S006‐1709) in female rat plasma has been developed and validated. A Discovery RP₁₈ column was used for the chromatographic elution using acetonitrile and 0.1% acetic acid in water as mobile phase (80:20 v/v) at the flow rate of 0.5 mL/min. MS/MS analysis was performed using a triple quadrupole mass spectrometer with electrospray ionization in negative ion mode using biochanin as an internal standard (IS). Extraction of S006‐1709 and IS from rat plasma was done by liquid–liquid extraction method using diethyl ether. The LC‐MS/MS method was sensitive with 1.95 ng/mL as the limit of detection and 3.9 ng/mL as the lower limit of quantification. The method was linear in the concentration range of 3.9–1000 ng/mL. The percentage bias for intraday and interday accuracy was not greater than 4.2 and the %RSD for intraday and interday precision was not greater than 13.2. The recoveries of S006‐1709 and IS were 73.9–79.3 and 85.7%, respectively. S006‐1709 was found to be stable in various stability studies. The validated LC‐MS/MS method was successfully applied for the oral pharmacokinetics study of S006‐1709 at 10 mg/kg in female Sprague–Dawley rats. Copyright © 2010 John Wiley & Sons, Ltd.     

Interdiffusion and solid solution strengthening in Ni–Co–Pt and Ni–Co–Fe ternary systems

Diffusion couple experiments are conducted in Co–Ni–Pt system at 1200?°C and in Co–Ni–Fe system at 1150?°C, by coupling binary alloys with the third element. Uphill diffusion is observed for both Co and Ni in Pt rich corner of the Co–Ni–Pt system, whereas in the Co–Ni–Fe system, it is observed for Co. Main and cross interdiffusion coefficients are calculated at the composition of intersection of two independent diffusion profiles. In both the systems, the main interdiffusion coefficients are positive over the whole composition range and the cross interdiffusion coefficients show both positive and negative values at different regions. Hardness measured by performing the nanoindentations on diffusion couples of both the systems shows the higher values at intermediate compositions.     

Quantum Dots (QDs) Based Fluorescent Sensor for the Selective Determination of Nimesulide

Fluorescent PET (Photoinduced Electron Transfer) has been of particular growth in recent times. A novel PET based fluorescent sensor using unmodified CdSe quantum dots (QDs) has been developed for the trace determination of Nimesulide (NIM). The sensor is based on the selective fluorescence quenching of quantum dots by NIM in presence of other NSAIDs and is found that intensity of quenching is linearly related to NIM concentration in the range 8.2?×?10^?7 – 4.01?×?10^?5?M. The mechanism of interaction is discussed. Finally, the potential application of the proposed method for the trace determination of NIM in pharmaceutical formulation is demonstrated.     

Structural and optical characterization of ZnS nanoparticles co-doped with Mn and Te

Nanoparticles of Zinc sulfide co-doped with equal atomic percentages of Mn and Te (5, 10 and 15 at%) were synthesized for the first time by chemical co-precipitation method. Thiophenol was used to passivate the surface of the particles. The as-prepared samples were amorphous in nature and nano-crystallinity was induced after calcining at 300 °C/2 h. The nanoparticles were characterized by EDAX, XRD, TEM, optical absorption and PL studies. EDAX spectra revealed only minor deviations of the dopant concentrations from the target compositions. The nanoparticles showed cubic structure. The particle size estimated from XRD/TEM was in the range 3–5 nm. Optical absorption studies showed a blue-shift of the fundamental absorption edge with respect to that of bulk ZnS. PL spectra showed emission in the red region with composition dependent emission wavelength. ZnS nanoparticles doped with Mn (5 and 10 at%) were also synthesized and characterized for comparison.     

Anomalous Stretching Dynamics of Tagged Monomer of Branched Polymer in Layered Random Flows

Journal of Statistical Physics - We extend our formalism to theoretically understand the stretch dynamics of single tagged monomer of flexible branched polymer with arbitrary topology in the...     

Self-Assembled Helical Arrays for the Stabilization of the Triplet State

Room-temperature phosphorescence of metal and heavy atom-free organic molecules has emerged as an area of great potential in recent years. A rational design played a critical role in controlling the molecular ordering to impart efficient intersystem crossing and stabilize the triplet state to achieve room-temperature ultralong phosphorescence. However, in most cases, the strategies to strengthen phosphorescence efficiency have resulted in a reduced lifetime, and the available nearly degenerate singlet-triplet energy levels impart a natural competition between delayed fluorescence and phosphorescence, with the former one having the advantage. Herein, an organic helical assembly supports the exhibition of an ultralong phosphorescence lifetime. In contrary to other molecules, 3,6-phenylmethanone functionalized 9-hexylcarbazole exhibits a remarkable improvement in phosphorescence lifetime (>4.1 s) and quantum yield (11 %) owing to an efficient molecular packing in the crystal state. A right-handed helical molecular array act as a trap and exhibits triplet exciton migration to support the exceptionally longer phosphorescence lifetime.