Determination of perfluorooctanoate and perfluorooctanesulfonate in water matrices by inline matrix elimination liquid chromatography with reversed phase separation and suppressed conductivity detection

This work describes a new method for the determination of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in water matrices by suppressed conductivity detection. Separation was achieved by isocratic elution on a reversed-phase column thermostated at 45°C using an aqueous mobile phase containing boric acid and acetonitrile. The PFOA and PFOS content in the water matrix were quantified by a pre-concentration technique. For the concentration range of 1 to 15 ng/mL and 2 to 30 ng/mL, the linear calibration curve for PFOA and PFOS yielded coefficients of determination (R(2)) of 0.9995 and 0.9985, respectively. The relative standard deviations were smaller than 1.5% for PFOA and PFOS. The retention-time precision of four consecutive 12 h injections was smaller than 0.641% and 0.818%, respectively. The presence of common divalent cations, such as calcium, magnesium, and iron in water matrices impairs PFOS recovery. This drawback was overcome by applying inline matrix elimination method. The optimized method was successfully applied for drinking water, ground water, and seawater samples.     

Quasi-static deformation and final fracture behaviour of aluminium alloy 5083: influence of cryomilling

The commercial aluminium alloy 5083 was processed via cryomilling to produce nanocrystalline (NC) powders with an average grain size of ～25–50?nm. The powders were subsequently degassed at 723 K (450°C), pre-heated and immediately quasi-isostatic (QI)-forged to produce a thermally stable bulk ultrafine grain (UFG) material having average grain size values ranging from 190 to 350?nm, depending on the processing conditions used. In this paper, the tensile properties and fracture behaviour of the bulk UFG material are presented and compared with the tensile properties of its conventionally processed counterpart. The specific influence of preheat temperature on strength and ductility of the alloy is briefly discussed. Three different pre-heat temperatures of 523, 623 and 723?K (250, 350 and 450°C) were chosen and used with the primary objective of controlling grain growth during forging. The influence of preheat temperature on tensile deformation and final fracture behaviour is highlighted. The macroscopic fracture modes of the bulk nanostructured material (BNM) prepared following three pre-heat temperatures are investigated. The microscopic mechanisms controlling tensile deformation and final fracture behaviour are discussed with regards to the intrinsic microstructural effects in the UFG alloy, nature of loading, and the kinetics and mechanisms of deformation.     

Assessment of natural radiation hazards and function of heat production rate in lake sediments of Puliyanthangal Lake surrounding the Ranipet industrial area,Tamil Nadu

Journal of Radioanalytical and Nuclear Chemistry - In this work, 238U, 232Th and 40K activity concentration and the associated radiological implications are determined in the lake sediments at...     

Preparation of nitrogen-doped reduced graphene oxide and its use in a glassy carbon electrode for sensing 4-nitrophenol at nanomolar levels

We describe a novel procedure for the synthesis of nitrogen-doped reduced graphene oxide (N-rGO). It is based on the thermal reduction of GO (dispersed in water) with sodium diethyldithiocarbamate that acts as both the reducing agent and the source for nitrogen. The surface morphology of the N-rGO is characterized using high resolution transmission electron microscopy. X-ray photoelectron spectroscopy was carried out to study the composition of their surface, and Raman spectroscopy was performed to study the level of doping with nitrogen and the structural order. The N-rGO was deposited on a glassy carbon electrode (GCE), and the resulting electrode utilized as a sensing platform for 4-nitrophenol (4-NP). The modified GCE exhibits a well-defined oxidation peak current that is about ten times larger when compared to that of a bare GCE. The electron transfer number, proton transfer number and electron transfer rate constant (k_s 1.046 s^?1) were determined. At optimized conditions, the oxidation peak current is linearly related to the concentration of 4-NP in the 20–500 nM range, with a correlation coefficient of 0.9917. The detection limit (at an SNR of 3) is 7 nM. The method was successfully applied to the analysis of waters spiked with 4-NP. Recoveries range from 97.8 to 102.6 %, and no interferences are found for common inorganic cations and anions. Figure

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Cadmium oxide nanoplatelets: synthesis, characterization and their electrochemical sensing property of catechol

Cadmium oxide (CdO) nanoplatelets were synthesized by thermal decomposition of cadmium malonate. The synthesized CdO nanoplatelets were characterized by X-ray diffraction (XRD); from the XRD analysis, it is clear that the phase structure of CdO nanoplatelets was found to be face-centered cubic with the average crystalline size of 40–50 nm. FT-IR analysis shows the presence of surface carboxyl and hydroxyl groups on to the CdO nanoplatelets. From DRS-UV–Vis analysis, both the direct and indirect band gaps of the CdO nanoplatelets were found to be 2.0 and 1.67 eV, respectively. From the FE-SEM analysis, the morphology of the synthesized CdO was found to be nanoplatelets, which were randomly agglomerated. Further, HR-TEM was used to confirm the formation of nanoplatelets. The electrochemical sensing property of CdO nanoplatelets was carried out by cyclic voltammetry (CV) by coating CdO nanoplatelets on Glassy carbon electrode (GCE) and using it as working electrode for sensing of catechol. The enhanced electrochemical behaviour is mainly attributed to the nanometer dimensions and surface hydroxyl groups on the CdO nanoplatelets. Chronoamperometry (CA) was used to determine the sensitivity and repeatability of the modified electrode. The modified electrode shows linear range of catechol concentration between 7.5 × 10^?6 and 1.5 × 10^?4 M with sensitivity of 9.8 nA μM^?1.     

Electrical and magnetic properties of Nd3+-substituted GdBaSrCu3O7 superconductor

The compounds GdBaSr_1?xNd_xCu₃O_y (where x = 0, 0.1, 0.2 and 0.3) were prepared using the solid-state reaction technique. The single phase and microrange crystalline nature of the compounds were studied by powder X-ray diffraction and SEM analysis. The electrical resistivity and magnetic properties of the compounds were studied as a function of temperature. A decrease in superconducting transition temperature for an increase in Nd substitution was observed. A decreasing trend of diamagnetic strength and an increasing trend of magnetic moment of the samples with Nd substitution were observed from magnetization measurement. The optimal sintering temperature of the compounds was found to be 950 °C.     

Preparation of nitrogen-doped reduced graphene oxide and its use in a glassy carbon electrode for sensing 4-nitrophenol at nanomolar levels

We describe a novel procedure for the synthesis of nitrogen-doped reduced graphene oxide (N-rGO). It is based on the thermal reduction of GO (dispersed in water) with sodium diethyldithiocarbamate that acts as both the reducing agent and the source for nitrogen. The surface morphology of the N-rGO is characterized using high resolution transmission electron microscopy. X-ray photoelectron spectroscopy was carried out to study the composition of their surface, and Raman spectroscopy was performed to study the level of doping with nitrogen and the structural order. The N-rGO was deposited on a glassy carbon electrode (GCE), and the resulting electrode utilized as a sensing platform for 4-nitrophenol (4-NP). The modified GCE exhibits a well-defined oxidation peak current that is about ten times larger when compared to that of a bare GCE. The electron transfer number, proton transfer number and electron transfer rate constant (k_s 1.046 s⁻¹) were determined. At optimized conditions, the oxidation peak current is linearly related to the concentration of 4-NP in the 20–500 nM range, with a correlation coefficient of 0.9917. The detection limit (at an SNR of 3) is 7 nM. The method was successfully applied to the analysis of waters spiked with 4-NP. Recoveries range from 97.8 to 102.6 %, and no interferences are found for common inorganic cations and anions.

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α-Fe2O3 nanoflowers: synthesis,characterization, electrochemical sensing and photocatalytic property

Nanoflower structured α-Fe₂O₃ was synthesized by adding hexamine to an aqueous solution of ferrous sulphate followed by drying and annealing at 600 °C for 6 h. X-ray diffraction analysis, Fourier-transformed infrared spectroscopy, Raman and DRS UV–visible absorption spectroscopy showed the formation of α-Fe₂O₃ with good crystalline nature. Field emission-scanning electron microscopy investigation revealed that the α-Fe₂O₃ has flower-like morphology, which is composed of nanorods. Cyclic voltammetry and chronoamperometry were used to investigate their electrochemical sensing property towards uric acid (UA). α-Fe₂O₃ exhibited enhanced sensing behavior with respect to that of bare GCE. Additionally, the α-Fe₂O₃ nanoflowers exhibit better photocatalytic activity of up to 71.7 % against rhodamine B (RhB) in short time of 60 min under visible light irradiation. It is found that the smaller crystallite size and flower-like morphology play a vital role in allowing an interaction between α-Fe₂O₃ and UA or RhB dye which enhances both the electrochemical sensing and photocatalytic activity.     

Sensing of picric acid with a glassy carbon electrode modified with CuS nanoparticles deposited on nitrogen-doped reduced graphene oxide

We describe the preparation of a nanohybrid consisting of nitrogen doped reduced graphene oxide and CuS nanoparticles (N-rGO/CuS) by in-situ microwave irradiation at weight ratios of 25/75, 50/50, and 75/25. The resulting nanohybrids were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, FTIR, spectroscopy, scanning electron and transmission electron microscopy, electrochemically by cyclic voltammetry and electrochemical impedance analysis. It is shown that the CuS nanoparticles are evenly decorated onto the N-rGO surface. The nanohybrids was placed on glassy carbon electrode (GCE) where they showed electro-reductive activity towards picric acid, typically at working voltages between ?0.2 and ?0.8 V (vs. SCE). Effects of pH value and scan rate were evaluated, and it is shown that two electrons are involved in electro-reduction. The detection limits of the GCE modified with various N-rGO/CuS hybrids (with 25/75, 50/50, and 75/25 wt%) are 6.2, 3.2, and 0.069 μM respectively. The method demonstrates its applicability in sensing of picric acid with good reproducibility.

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Graphical abstract Nitrogen doped reduced graphene oxide nanohybrids was synthesized for the detection of picric acid. A straightforward and preconcentration free analysis of picric acid was successfully demonstrated at nanomolar levels using the nanohybrids.