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Soil pollution is one of the serious global threats causing risk to environment and humans. The major cause of accumulation of pollutants in soil are anthropogenic activities and some natural processes. There are several types of soil pollutants which deteriorate the quality of human life and animal health. They are recalcitrant hydrocarbon compounds, metals, antibiotics, persistent organic compounds, pesticides and different kinds of plastics. Due to the detrimental properties of pollutants present in soil on human life and ecosystem such as carcinogenic, genotoxic and mutagenic effects, alternate and effective methods to degrade the pollutants are recommended. Bioremediation is an effective and inexpensive method of biological degradation of pollutants using plants, microorganisms and fungi. With the advent of new detection methods, the identification and degradation of soil pollutants in different ecosystems were made easy. Metagenomic approaches are a boon for the identification of unculturable microorganisms and to explore the vast bioremediation potential for different pollutants. Metagenomics is a power tool to study the microbial load in polluted or contaminated land and its role in bioremediation. In addition, the negative ecosystem and health effect of pathogens, antibiotic and metal resistant genes found in the polluted area can be studied. Also, the identification of novel compounds/genes/proteins involved in the biotechnology and sustainable agriculture practices can be performed with the integration of metagenomics. Highlights: Soil carries diverse microorganisms which maintain plant and soil health. The different types of recalcitrant soil pollutants affect the ecosystem and human health. Complex pollutants can be degraded through bioremediation using microorganisms/plants Metagenomic approaches help to explore novel organisms and enzymes involved in bioremediation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Lightweight, flexible and foldable films of polyvinyl alcohol and polyaniline modified carbon nanofibers were prepared by solvent casting method. • The reported film exhibits high shielding efficiency in both S and X-band frequencies at a thickness of 0.11 mm thickness. • High specific EMI SE of -177 dB cm3/g was obtained for PANI/CNF/PVA composite which is more than the values reported for carbon-based composites. • The flexible composite films of carbon nanofibers exhibited a dielectric constant of 62 and very shallow skin depth of 0.05 at 10.97 GHz. • Easily foldable polymer composite film with excellent absorption dominated electromagnetic interference shielding can be an excellent EMI shielding material. Abstract Here we report the microwave characterization and electromagnetic interference (EMI) shielding property of polyvinyl alcohol (PVA) based thin and flexible composite films containing carbon nanofibers (CNF) and nanofibrillated cellulose (NFC). Microwave properties of the composites were analyzed in terms of permittivity, loss tangent, skin depth and absorption coefficient. High permittivity, absorption coefficient and low skin depth were obtained for carbon nanofiber-based composites owing to its good electrical conductivity. The shielding effectiveness (SE) of two composites was measured in the 2–4 GHz (S- band) and 8–12 GHz (X-band) frequency range. Abrupt increase of SE with increasing fiber concentration was observed for CNF based composite. An electromagnetic shielding effectiveness of about −31.5 dB in the S band and of -33.6 dB in the X band was achieved at 0.11 mm thickness. The SE due to absorption (SE A) and reflection (SE R) were increased with increase of PANI/CNF content. Additionally, CNF based composite film had a very low density of 0.11 g/cm3. Compared to metals and other carbonaceous materials, this composite film exhibited a high specific EMI shielding efficiency of −177 dB cm3/g. [ABSTRACT FROM AUTHOR]

Cost effective, high performance dielectric composites based on polyvinyl alcohol, cellulose fibers and polyaniline were prepared and the dielectric properties were studied as a function of fiber content, fiber dimensions and polyaniline content over a frequency range of 40 Hz to 30 MHz. The short cellulose fibers were size-reduced to micro and nano levels prior to coating with polyaniline. Fiber surface was coated with Polyaniline (PANI) by an in situ polymerization technique in aqueous medium. The composites were then prepared by solution casting method. Short cellulose fiber composites showed a dielectric constant (DEC) of 2.3 × 105 at 40 Hz. For the micro- and nano- cellulose fiber composites the DEC was increased to 4.5 × 105 and 1.3 × 108, respectively. To gain insight into the inflection point of the dielectric data polynomial regression analysis was carried out. The loss tangent of all the composites remained at less than 1.5. Further, AC conductivity, real and imaginary electric moduli of all the composites were evaluated. PVA nanocomposite attained an AC conductivity of 3 S/m. These showed that by controlling the size of the fiber used, it was possible to tune the permittivity and dielectric loss to desired values over a wide range. These novel nanocomposites, combining high dielectric constant and low dielectric loss, can be effectively used in applications such as high-charge storage capacitors. [ABSTRACT FROM AUTHOR]

The reaction of metal carbonyl compounds with group 6 and 8 metallaboranes led us to report the synthesis and structural characterization of several novel mixed-metal chalcogenide tetrahedral clusters. Thermolysis of arachno-[(Cp*RuCO)2B2H6], 1, and [Os3(CO)12] in the presence of 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Os3(CO)9}S], 3, and [Cp*Ru(μ-H){Os3(CO)11}], 4. In a similar fashion, the reaction of [(Cp*Mo)2B5H9], 2, with [Ru3(CO)12] and 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Ru3(CO)9}S], 5, and conjuncto-[(Cp*Mo)2B5H8(μ-H){Ru3(CO)9}S], 6. Both compounds 3 and 5 can be described as 50-cve (cluster valence electron) mixed-metal chalcogenide clusters, in which a sulfur atom replaces one of the vertices of the tetrahedral core. Compounds 3 and 5 possess a [M3S] tetrahedral core, in which the sulfur is attached to an exo-metal fragment, unique in the [M3S] metal chalcogenide tetrahedral arrangements. All the compounds have been characterized by mass spectrometry, IR, and 1H, 11B and 13C NMR spectroscopy in solution, and the solid state structures were unequivocally established by crystallographic analysis of compounds 3, 5 and 6. [ABSTRACT FROM AUTHOR]

The photolysis of [M2(CO)10] (M=Re or Mn) with BH3⋅thf at room temperature yields arachno -1 and 2, [(CO)8M2B2H6] ( 1: M =Re, 2: M =Mn). Both the compounds show a butterfly structure with seven skeletal electron pairs and 42 valence electrons. This result presents a new method for general access to low-boron-content metal-boron compounds without the cyclopentadienyl ligand at the metal centers. This new synthetic route is superior to the existing procedures because it avoids the use of [LiBH4] and metal polychlorides, for which the synthesis is very tedious. Compound 1 catalyzes the cyclotrimerization of a series of internal and terminal alkynes to yield mixtures of 1,3,5- and 1,2,4-substituted benzenes. The reactivity of 1 with alkynes demonstrates for the first time that the introduction of the [B2H6] moiety into the [Re2(CO)10] framework significantly enhances the catalytic activity. Note that [Re2(CO)10] catalyzes the same set of alkynes under harsh conditions over a prolonged period of time. Quantum-chemical calculations using DFT methods are applied to afford further insight into the electronic structure, stability, and bonding of 1 and 2. All the compounds are characterized by IR and 1H, 11B, and 13C NMR spectroscopy, and the geometry of 1 is established unambiguously through crystallographic analysis. [ABSTRACT FROM AUTHOR]