Epoxy composites containing cobalt(II)-porphine anchored multiwalled carbon nanotubes as thin electromagnetic interference shields, adhesives and coatings

Herein a facile strategy has been adopted to design epoxy based adhesive/coating materials that can shield electromagnetic radiation. Multiwalled carbon nanotubes (MWNTs) were non-covalently modified with an ionic liquid and 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine cobalt(II) (Co-TPP). The dispersion state of modified MWNTs in the composites was assessed using a scanning electron microscope. The electrical conductivity of the composites was improved with the addition of IL and Co-TPP. The shielding effectiveness was studied as a function of thickness and intriguingly, composites with as thin as 0.5 mm thickness were observed to reflect 497% of the incoming radiation. Carbon fibre reinforced polymer substrates were used to demonstrate the adhesive properties of the designed epoxy composites. Although, the shielding effectiveness of epoxy/MWNT composites with or without IL and Co-TPP is nearly the same for 0.5 mm thick samples, the lap shear test under tensile loading revealed an extraordinary adhesive bond strength for the epoxy/IL-MWNT/Co-TPP composites in contrast to neat epoxy. For instance, the lap shear strength of epoxy/IL-MWNT/Co-TPP composites was enhanced by 100% as compared to neat epoxy. Furthermore, the composites were thermally stable for practical utility in electronic applications as inferred from thermogravimetric analysis.

Investigations of aerosol black carbon from a semi-urban site in the Indo-Gangetic Plain region

Long-term (2009-2012) data from ground-based measurements of aerosol black carbon (BC) from a semi-urban site, Pantnagar (29.0 degrees N, 79.5 degrees E, 231 m amsl), in the Indo-Gangetic Plain (IGP) near the Himalayan foothills are analyzed to study the regional characterization. Large variations are seen in BC at both diurnal and seasonal scales, associated with the mesoscale and synoptic meteorological processes, and local/regional anthropogenic activities. BC diurnal variations show two peaks (morning and evening) arising from the combined effects of the atmospheric boundary layer (ABL) dynamics and local emissions. The diurnal amplitudes as well as the rates of diurnal evolution are the highest in winter season, followed by autumn, and the lowest in summer-monsoon. BC exhibits nearly an inverse relation with mixing layer depth in all seasons; being strongest in winter (R-2 = 0.89) and weakest (R-2 = 0.33) in monsoon (July-August). Unlike BC, co-located aerosol optical depths (AOD) and aerosol absorption are highest in spring over IGP, probably due to the presence of higher abundances of aerosols (including dust) above the ABL (in the free troposphere). AOD (500 nm) showed annual peak (>0.6) in May-June, dominated by coarse mode, while fine mode aerosols dominated in late autumn and early winter. Aerosols profiles from CALIPSO show highest values close to the surface in winter/autumn, similar to the feature seen in surface BC, whereas at altitudes > 2 km, the extinction is maximum in spring/summer. WRF-Chem model is used to simulate BC temporal variations and then compared with observed BC. The model captures most of the important features of the diurnal and seasonal variations but significantly underestimated the observed BC levels, suggesting improvements in diurnal and seasonal varying BC emissions apart from the boundary layer processes. (C) 2015 Elsevier Ltd. All rights reserved.

Outstanding dielectric constant and piezoelectric coefficient in electrospun nanofiber mats of PVDF containing silver decorated multiwall carbon nanotubes: assessing through piezoresponse force microscopy

In order to enhance the piezoelectric b-phase, PVDF was electrospun from DMF solution. The enhanced b-phase was discerned by comparing the electrospun fibers against the melt mixed samples. While both the processes resulted in phase transformation of a-to electroactive b-polymorph in PVDF, the fraction of b-phase was strongly dependent on the adopted process. Two different nanoscopic particles: carboxyl functionalized multiwall carbon nanotubes (CNTs) and silver (Ag) decorated CNTs were used to further enhance the piezoelectric coefficient in the electrospun fibers. Fourier transform infrared spectroscopy (FTIR) and wide-angle X-ray diffraction (XRD) supports the development of piezoelectric b-phase in PVDF. It was concluded that electrospinning was the best technique for inducing the b-polymorph in PVDF. This was attributed to the high voltage electrostatic field that generates extensional forces on the polymer chains that aligns the dipoles in one direction. The ferroelectric and piezoelectric measurement on electrospun fibers were studied using piezo-response force microscope (PFM). The Ag-CNTs filled PVDF electrospun fibers showed the highest piezoelectric coefficient (d(33) = 54 pm V-1) in contrast to PVDF/CNT fibers (35 pm V-1) and neat PVDF (30 pm V-1). This study demonstrates that the piezoelectric coefficient can be enhanced significantly by electrospinning PVDF containing Ag decorated nanoparticles.

No More HF: Teflon-Assisted Ultrafast Removal of Silica to Generate High-Surface-Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance

An innovative technique to obtain high-surface-area mesostructured carbon (2545m(2)g(-1)) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10min) with complete elimination of toxic HF usage. The obtained carbon material (JNC-1) displays excellent CO2 capture ability (ca. 26.2wt% at 0 degrees C under 0.88bar CO2 pressure), which is twice that of CMK-3 obtained by the HF etching method (13.0wt%). JNC-1 demonstrated higher H-2 adsorption capacity (2.8wt%) compared to CMK-3 (1.2wt%) at -196 degrees C under 1.0bar H-2 pressure. The bimodal pore architecture of JNC-1 led to superior supercapacitor performance, with a specific capacitance of 292Fg(-1) and 182Fg(-1) at a drain rate of 1Ag(-1) and 50Ag(-1), respectively, in 1m H2SO4 compared to CMK-3 and activated carbon.

Non-covalent C-Cl center dot center dot center dot pi interaction in acetylene-carbon tetrachloride adducts: Matrix isolation infrared and ab initio computational studies

Non-covalent halogen-bonding interactions between n cloud of acetylene (C2H2) and chlorine atom of carbon tetrachloride (CCl4) have been investigated using matrix isolation infrared spectroscopy and quantum chemical computations. The structure and the energies of the 1:1 C2H2-CCl4 adducts were computed at the B3LYP, MP2 and M05-2X levels of theory using 6-311++G(d,p) basis set. The computations indicated two minima for the 1:1 C2H2-CCl4 adducts; with the C-Cl center dot center dot center dot pi adduct being the global minimum, where pi cloud of C2H2 is the electron donor. The second minimum corresponded to a C-H...Cl adduct, in which C2H2 is the proton donor. The interaction energies for the adducts A and B were found to be nearly identical. Experimentally, both C-Cl center dot center dot center dot pi and C-H center dot center dot center dot Cl adducts were generated in Ar and N2 matrixes and characterized using infrared spectroscopy. This is the first report on halogen bonded adduct, stabilized through C-Cl center dot center dot center dot pi interaction being identified at low temperatures using matrix isolation infrared spectroscopy. Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) analyses were performed to support the experimental results. The structures of 2:1 ((C2H2)(2)-CCl4) and 1:2 (C2H2-(CCl4)(2)) multimers and their identification in the low temperature matrixes were also discussed. (C) 2015 Elsevier B.V. All rights reserved.

Isotopic disequilibrium in Globigerina bulloides and carbon isotope response to productivity increase in Southern Ocean

Oxygen and carbon isotope ratios in planktonic foraminifera Globigerina bulloides collected from tow samples along a transect from the equatorial Indian ocean to the Southern Ocean (45 degrees E and 80 degrees E and 10 degrees N to 53 degrees S) were analysed and compared with the equilibrium delta O-18 and delta C-13 values of calcite calculated using the temperature and isotopic composition of the water column. The results agree within similar to 0.25% for the region between 10 degrees N and 40 degrees S and 75-200 m water depth which is considered to be the habitat of Globigerina bulloides. Further south (from 40 degrees S to 55 degrees S), however, the measured delta O-18 and delta C-13 values are higher than the expected values by similar to 2% and similar to 1% respectively. These enrichments can be attributed to either a `vital effect' or a higher calcification rate. An interesting pattern of increase in the delta C-13(DIC) value of the surface water with latitude is observed between 35 degrees S and similar to 60 degrees S, with a peak at similar to 42 degrees S. This can be caused by increased organic matter production and associated removal. A simple model accounting for the increase in the delta C-13(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude.

No More HF: Teflon-Assisted Ultrafast Removal of Silica to Generate High-Surface-Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance

An innovative technique to obtain high-surface-area mesostructured carbon (2545m(2)g(-1)) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10min) with complete elimination of toxic HF usage. The obtained carbon material (JNC-1) displays excellent CO2 capture ability (ca. 26.2wt% at 0 degrees C under 0.88bar CO2 pressure), which is twice that of CMK-3 obtained by the HF etching method (13.0wt%). JNC-1 demonstrated higher H-2 adsorption capacity (2.8wt%) compared to CMK-3 (1.2wt%) at -196 degrees C under 1.0bar H-2 pressure. The bimodal pore architecture of JNC-1 led to superior supercapacitor performance, with a specific capacitance of 292Fg(-1) and 182Fg(-1) at a drain rate of 1Ag(-1) and 50Ag(-1), respectively, in 1m H2SO4 compared to CMK-3 and activated carbon.

Peptide-utilizing carbon starvation gene yjiY is required for flagella-mediated infection caused by Salmonella

Peptide metabolism forms an important part of the metabolic network of Salmonella and to acquire these peptides the pathogen possesses a number of peptide transporters. Whilst various peptide transporters known in Salmonella are well studied, very little is known about the carbon starvation (cst) genes cstA and yjiY, which are also predicted to be involved in peptide metabolism. We investigated the role of these genes in the metabolism and pathogenesis of Salmonella, and demonstrated for the first time, to the best of our knowledge, that cst genes actually participate in transport of specific peptides in Salmonella. Furthermore, we established that the carbon starvation gene yjiY affects the expression of flagella, leading to poor adhesion of the bacterium to host cells. In contrast to the previously reported role of cstA in virulence of Salmonella in Caenorhabditis elegans, we showed that yjiY is required for successful colonization of Salmonella in the mouse gut. Thus, cst genes not only contribute to the metabolism of Salmonella, but also influence its virulence.

Experimental solubilities of two lipid derivatives in supercritical carbon dioxide and new correlations based on activity coefficient models

The solubilities of two lipid derivatives, geranyl butyrate and 10-undecen-1-ol, in SCCO2 (supercritical carbon dioxide) were measured at different operating conditions of temperature (308.15 to 333.15 K) and pressure (10 to 18 MPa). The solubilities (in mole fraction) ranged from 2.1 x 10(-3) to 23.2 x 10(-3) for geranyl butyrate and 2.2 x 10(-3) to 25.0 x 10(-3) for 10-undecen-1-ol, respectively. The solubility data showed a retrograde behavior in the pressure and temperature range investigated. Various combinations of association and solution theory along with different activity coefficient models were developed. The experimental data for the solubilities of 21 liquid solutes along with geranyl butyrate and 10-undecen-1-ol were correlated using both the newly derived models and the existing models. The average deviation of the correlation of the new models was below 15%.

Studies on Carbon Mediated Paste Screen Printed Sensors for Blood Glucose Sensing Application

Ready-to-use screen printed glucose sensors are fabricated using Prussian Blue (PB) and Cobalt Phthalocyanine (CoPC) mediated carbon inks as working electrodes. The reference and counter electrodes are screen printed using silver/silver chloride and graphitic carbon paste respectively. The screen printed reference electrodes (internal reference electrode (IRE)) are found to be stable for more than 60 minutes when examined with saturated calomel electrode. Optimal operating voltage for PB and CoPC screen printed sensors are determined by hydrodynamic voltammetric technique. Glucose oxidase is immobilized on the working electrodes by cross-linking method. PB mediated glucose sensor exhibits a sensitivity of 5.60 mA cm(-2)/mM for the range, 10 to 1000 mu M. Sensitivity of CoPC mediated glucose sensor is found to be 5.224 mu A cm(-2)/mM and amperometeric response is linear for the range, 100 to 1500 mu M. Interference studies on the fabricated glucose sensors are conducted with species like uric acid and ascorbic acid. PB mediated sensors showed a completely interference-free behavior. The sensing characteristics of PB mediated glucose sensors are also studied in diluted human serum samples and the results are compared with the values obtained through standard clinical method. The co-efficient of variation is found to be less than 5%. (C) 2015 The Electrochemical Society. All rights reserved.

Peptide-utilizing carbon starvation gene yjiY is required for flagella-mediated infection caused by Salmonella

Peptide metabolism forms an important part of the metabolic network of Salmonella and to acquire these peptides the pathogen possesses a number of peptide transporters. Whilst various peptide transporters known in Salmonella are well studied, very little is known about the carbon starvation (cst) genes cstA and yjiY, which are also predicted to be involved in peptide metabolism. We investigated the role of these genes in the metabolism and pathogenesis of Salmonella, and demonstrated for the first time, to the best of our knowledge, that cst genes actually participate in transport of specific peptides in Salmonella. Furthermore, we established that the carbon starvation gene yjiY affects the expression of flagella, leading to poor adhesion of the bacterium to host cells. In contrast to the previously reported role of cstA in virulence of Salmonella in Caenorhabditis elegans, we showed that yjiY is required for successful colonization of Salmonella in the mouse gut. Thus, cst genes not only contribute to the metabolism of Salmonella, but also influence its virulence.

Voltammetric determination of paracetamol, tramadol and caffeine using poly(Nile blue) modified glassy carbon electrode

A poly(Nile blue) modified glassy carbon electrode (PNBMGCE) was fabricated by electropolymerisation of Nile blue (NB) monomer using cyclic voltammetry (CV) and was used for the determination of paracetamol (ACOP), tramadol (TRA) and caffeine (CAF). The electrochemical investigations showed that PNB - film formed on the surface of glassy carbon electrode (GCE) improved the electroactive surface area and displayed a remarkable increase in the peak current and a substantial decrease in over potential of ACOP, TRA and CAF when compared to bare GCE. The dependence of peak current and potential on pH, sweep rate and concentration were also investigated at the surface of PNBMGCE. It showed good sensitivity and selectivity in a wide linear range from 2.0 x 10(-7) to 1.62 x 10(-5) M, 1.0 x 10(-6) to 3.1 x 10(-4) M and 8.0 x 10(-7) to 2.0 x 10(-5) M, with detection limits of 0.08, 0.5 and 0.1 mu M, for ACOP, TRA and CAF, respectively. The PNBMGCE was also successfully applied for the determination of ACOP, TRA and CAF in pharmaceutical dosage forms. (C) 2016 Elsevier B.V. All rights reserved.

A strategy to achieve enhanced electromagnetic interference shielding at ultra-low concentration of multiwall carbon nanotubes in P alpha MSAN/PMMA blends in the presence of a random copolymer PS-r-PMMA

A unique strategy was adopted to achieve an ultra-low electrical percolation threshold of multiwall carbon nanotubes (MWNTs) (0.25 wt%) in a classical partially miscible blend of poly-alpha-methylstyrene-co-acrylonitrile and poly(methyl methacrylate) (P alpha MSAN/PMMA), with a lower critical solution temperature. The polymer blend nanocomposite was prepared by standard melt-mixing followed by annealing above the phase separation temperature. In a two-step mixing protocol, MWNTs were initially melt-mixed with a random PS-r-PMMA copolymer and subsequently diluted with 85/15 P alpha MSAN/PMMA blends in the next mixing step. Mediated by the PS-r-PMMA, the MWNTs were mostly localized at the interface and bridged the PMMA droplets. This strategy led to enhanced electromagnetic interference (EMI) shielding effectiveness at 0.25 wt% MWNTs through multiple scattering from MWNT-covered droplets, as compared to the blends without the copolymer, which were transparent to electromagnetic radiation.

Nitrogen-assisted electroless assembling of 3D nanodendrites consisting of Pd and N-doped carbon nanoparticles as bifunctional catalysts

We report a facile synthesis of three-dimensional (3D) nanodendrites of Pd nanoparticles (NPs) and nitrogen-doped carbon NPs (N-CNPs) by electroless deposition of Pd2+ ions. N-CNPs being an electron-enriched material act as a reducing agent. Moreover, the availability of a variety of nitrogen species in N-CNPs promotes the open arm structure as well as stabilizes the oriented 3D assembly of primary Pd NPs. The dendrites exhibit superior catalytic activity for methanol (0.5 M) oxidation in alkaline media (1 M NaOH) which is ascribed to the large electrochemical active surface area and the enhanced mass activity with repeated use. Further mass activity improvement has been realized after acid-treatment of dendrites which is attributed to the increment in the -OH group. The dendrites show higher mass activity (J(f) similar to 653 A g(-1)) in comparison with a commercial Pt-carbon/Pd-carbon (Pt-C/Pd-C) catalyst (J(f) similar to 46 and 163 A g(-1), respectively), better operational stability, superior CO tolerance with I-f/I-b (similar to 3.7) over a commercial Pt-C/Pd-C catalyst (I-f/I-b similar to 1.6 and 1.75, respectively) and may serve as a promising alternative to commercial Pt-C catalysts for anode application in alkaline fuel cells. To ensure the adaptability of our 3D-nanodendrites for other catalytic activities, we studied 4-nitrophenol reduction at room temperature. The 3D-nanodendrites show excellent catalytic activity toward 4-nitrophenol reduction, as well.

A noble and single source precursor for the synthesis of metal-rich sulphides embedded in an N-doped carbon framework for highly active OER electrocatalysts

Here, we demonstrate a green and environment-friendly pyrolysis route for the synthesis of metal-rich sulphide embedded in an N-doped carbon (NC) framework in the absence of sulphide ions (S2-). The metal-chelate complex (tris(ethylenediamine) metal(II) sulfate) serves as a new and single source precursor for the synthesis of earth abundant and non-precious hybrid structures such as metal-rich sulphides Co9S8@NC and Ni3S2@ NC when M-II = Co2+ and Ni2+ and counter sulphate (SO42-) ions are the source of S. Both the hybrids show superior OER activity as compared to commercial RuO2.