Synthesis of a New Spiro System: 1-Oxa-7-thia-4-azaspiro[4.5]decane 7,7-Dioxide

Dihydro-2H-1λ⁶-thiopyran-1,1,3(4H)-trione reacted with N-substituted 2-aminoethanols to give derivatives of a new spiro system, 1-oxa-7λ⁶-thia-4-azaspiro[4.5]decane-7,7-diones. No spirocyclic product was obtained by the reaction with unsubstituted 2-aminoethanol, but the corresponding enamine was formed as in the reactions with other primary amines.     

Optimisation of laboratory arsenic analysis for groundwaters of West Bengal,India and possible water testing strategy

Regular monitoring of arsenic (As) in groundwater is crucial from public health perspectives as millions of people are suffering due to use of contaminated aquifer water for drinking purposes. The routine analyses, especially in developing nations, are mostly done in localised government/non-government laboratories with limited resources, having the target of analysing large number of samples in each run. Thus apart from analytical sensitivity, cost-effectiveness of the method and eco-friendliness of the experimental operation are key surreptitious factors. This demands optimisation of total As measurement methods and finding a method that gives ‘optimum benefit’ considering all these factors together. The present study therefore evaluates four common As (total) measurement methods [iodometric-colorimetric method, silver diethyl dithiocarbamate method, molybdenum blue method and hydride generation atomic absorption spectrophotometric (HG-AAS) method] practised in the Bengal Delta Plain, in view of their analytical sensitivity, related environmental hazard and experimental costs. It was found that the HG-AAS method is analytically more sensitive, whereas the iodometric-colorimetric method and the molybdenum blue method are better choices in terms of eco-friendliness and cost-effectiveness, respectively. However, when all three factors (analytical reliability, environmental hazard and cost) are considered simultaneously, the molybdenum blue method was found to be placed first in the ‘optimum performance rank’ list. It was also found that both environmental hazard and cost play a more crucial role than analytical reliability, although this is case specific and would differ from place to place around the globe. Finally based on the results, we have hypothesised a water testing strategy for developing countries such as India where the molybdenum blue method can be adapted as a screening method and later the HG-AAS method can be used to precisely identify the groundwater samples with As concentration below the WHO drinking water guideline value of 10 μg/L.     

Hydrophobic thin fluoropolymer coating on cotton surfaces

We report a simple novel procedure to prepare hydrophobic cotton textiles by admicellar polymerization. By in situ introducing fluoropolymer on cotton fibers to generate a dual-size surface roughness, followed by hydrophobization with a little amount of fluoromonomer Octafluoropentamethyl methacrylate (OFPM) with short time, normally hydrophilic cotton has been easily turned into hydrophobic. Hydrophobic cotton textile exhibits a static water contact angle of 124° for a 10?µl droplet. When an octa fluoroalkyl chain is introduced to the cotton surface, the originally smooth surface changed immediately to rough surface which is the key factor for hydrophobicity like lotus leaves.     

Influence of unsaturated aliphatic and aromatic volatile organic compounds on the oxidation of aqueous sulfur dioxide by oxygen in aqueous medium

The trace atmospheric volatile organic compounds(VOCs) are reported to influence the oxidation of dissolved sulfur dioxide, S(IV), by oxygen, which is an important reaction in atmospheric acid formation. In this work, the influence of 15 VOCs on uncatalyzed oxidation of S(IV) by oxygen has been investigated by following the disappearance of [O₂]. The inhibition of oxidation reaction by toluene, aniline, benzene, cinnamic acid, hydroquinone, acrylamide, acrylonitrile and allyl alcohol was defined by the rate law(A):k_VOC = k₀/(1+B [Inh]) (A)where, k_VOC, and k₀ are the first order rate constants in the presence and the absence of VOCs respectively. B is the inhibition parameter and [Inh] is the concentration of inhibitor.On the other hand, fumaric, maleic and crotonic acids, which have conjugated CC bonds, catalyze the reaction defined by the rate law(B):k_VOC = k₀ + k_cat [VOC] (B)where k_cat is catalytic constant and [VOC] is the concentration of catalytic VOC.Interestingly, presence of 1-hexene, cyclohexene, methacrylic acid, methyl acrylate was without any significant effect on the rate of reaction.     

1-Azathioxanthone Appended Lanthanide(III) DO3A Complexes That Luminesce Following Excitation at 405 nm**

Since the pioneering report by Selvin, we have been fascinated by the potential of using lanthanide luminescence in bioimaging. The uniquely narrow emission lines and long luminescence lifetimes both provide the potential for background free images together with full certainty of probe localization. General use of lanthanide based bioimaging was first challenged by low brightness, and later by the need of UV (<405 nm) excitation sources not present in commercial microscopes. Here, we designed three lanthanide-based imaging probes based on a known motif to investigate the limitations of 405 nm excitation. These were synthesized, characterized, investigated on dedicated as well as commercial microscopes, and the photophysics was explored in detail. It was proven without doubt that the lanthanide complexes enter the cells and luminesce internally. Even so, no lanthanide luminescence were recovered on the commercial microscopes. Thus, we returned to the photophysical properties that afforded the conclusion that – despite the advances in light sources and photodetectors – we need new designs that can give us brighter lanthanide complexes before bioimaging with lanthanide luminescence becomes something that is readily done.     

Rearrangement of dicarboranyl methyl cation to icosahedral C3B9H12+: An ab initio dynamics view

Closo-carborane anions are prominent, whereas the cations of the same are less abundant in the literature. As these ions have similar size and are weakly coordinating, the ionic liquids of these two ions could have important applications in many areas of chemistry. In view of limited number of polyhedral carborane cations available, we revisited the rearrangement of dicarboranyl methyl cation (7-CH₂ 7,9-nido-C₂B₉H₁₀⁺) using ab initio molecular dynamics calculations with metadynamics. Our simulations confirmed the concerted mechanism of the rearrangement. We believe this work will resume the interest in its synthesis and carborane cations in general.     

New conducting polymers, 3. Doping,stability, electrical,and optical characteristics of poly-(P-phenylphosphoethynediyl)

Studies on direct-current electrical conductivity and optical properties of a new solution of processable conducting polymer are reported. Electrical conductivity of thin films of the polymer on glass plate at room temperature was 6×10⁻⁶ S/cm. Study of conductivity with variation of temperature does not provide any definite thermal activation energy, which is in accordance with the amorphous nature of polymer. Optical absorption data adopting the Bardeen equation showed that maximum ‘optical gap’ (E _g ) is 3.30 eV. Doping with Br₂-vapor was found to be only partially effective in decreasingE _g by 0.43 eV. The polymer was found to be quite stable under normal atmospheric conditions. Environmental stability of both undoped and doped polymer has been discussed. Part 2: [5]     

Effect of shock-wave compression up to 65 GPa on the crystal structure and superconducting properties of MgB<Subscript>2</Subscript>

The effect of steplike shock-wave compression up to 65 GPa on the crystal structure and super-conducting transition temperature of a polycrystalline MgB₂ sample is studied. X-ray diffraction demonstrates that the shock-wave compression of the MgB₂ sample does not cause any irreversible structural phase transformations in it except for the formation of lattice microstrains. These conclusions agree with the super-conducting transition temperatures of the MgB₂ sample measured before and after shock-wave compression.     

Phytochelatins: Peptides Involved in Heavy Metal Detoxification

Phytochelatins (PCs) are enzymatically synthesized peptides known to involve in heavy metal detoxification and accumulation, which have been measured in plants grown at high heavy metal concentrations, but few studies have examined the response of plants even at lower environmentally relevant metal concentrations. Recently, genes encoding the enzyme PC synthase have been identified in plants and other species enabling molecular biological studies to untangle the mechanisms underlying PC synthesis and its regulation. The present paper embodies review on recent advances in structure of PCs, their biosynthetic regulation, roles in heavy metal detoxification and/or accumulation, and PC synthase gene expression for better understanding of mechanism involved and to improve phytoremediation efficiency of plants for wider application.     

Ultrafast Dynamics of Solvation and Charge Transfer in a DNA‐Based Biomaterial

Charge migration along DNA molecules is a key factor for DNA‐based devices in optoelectronics and biotechnology. The association of a significant amount of water molecules in DNA‐based materials for the intactness of the DNA structure and their dynamic role in the charge‐transfer (CT) dynamics is less documented in contemporary literature. In the present study, we have used a genomic DNA–cetyltrimethyl ammonium chloride (CTMA) complex, a technological important biomaterial, and Hoechest 33258 (H258), a well‐known DNA minor groove binder, as fluorogenic probe for the dynamic solvation studies. The CT dynamics of CdSe/ZnS quantum dots (QDs; 5.2 nm) embedded in the as‐prepared and swollen biomaterial have also been studied and correlated with that of the timescale of solvation. We have extended our studies on the temperature‐dependent CT dynamics of QDs in a nanoenvironment of an anionic, sodium bis(2‐ethylhexyl)sulfosuccinate reverse micelle (AOT RMs), whereby the number of water molecules and their dynamics can be tuned in a controlled manner. A direct correlation of the dynamics of solvation and that of the CT in the nanoenvironments clearly suggests that the hydration barrier within the Arrhenius framework essentially dictates the charge‐transfer dynamics.