A rapid approach for assessment of arsenic exposure by elemental analysis of single strand of hair using laser ablation-inductively coupled plasma-mass spectrometry

Application of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) as a method for identification of arsenic in a single hair strand was investigated. Using a single point ablation method detectability of ⁷⁵As and other two elements (²⁰⁸Pb and ⁶⁴Zn) were evaluated. Arsenic (⁷⁵As) signal is improved with enhanced laser ablation conditions. For the arsenic determination in hair single spots or single linear scans with enhanced laser ablation conditions described in the paper are satisfactory although  800 μm linear scans may be preferable. Arsenic levels in a single strand of hair from individuals who were chronically exposed to arsenic contaminated drinking water from a village in the Atacama Desert in northern Chile were determined by LA-ICP-MS. These results were satisfactorily correlated with total As concentration previously measured by hydride generation (HG)-ICP-MS. The sample throughput is high and it takes  3 min per each hair sample including mounting, focusing and analysis. LA-ICP-MS method can be used for the rapid identification and screening of toxic and nutritionally important elements in hair.     

Photodegradation of poly(neopentyl isophthalate) part I: Laboratory and outdoor conditions

In this paper the mechanisms of photodegradation of poly(neopentyl isophthalate) (PNI) in laboratory (Suntest XXL+, λ > 300 nm) and outdoor conditions are compared. Changes in the chemical composition were studied with ATR-FTIR, SEC and MALDI-ToF MS. Furthermore, the results were compared with data presented in our previous paper on PNI coatings that were aged in the UVACUBE (λ > 254 nm). Two main aspects of photodegradation of PNI are addressed in the present paper: the influence of different wavelengths and the comparison of laboratory and outdoor exposure regarding the mechanism of degradation. Under short (λ > 254 nm) and long (λ > 300 nm) wavelength irradiation similar products of degradation are formed. However, the presence of short wavelength radiation dramatically accelerates the overall rate of photodegradation of PNI. UV light absorption calculations confirm this experimentally found acceleration. Exposure of PNI in laboratory and outdoor conditions, both with wavelengths λ > 300 nm resulted in similar degradation products in the initial stage of ageing.     

Ground state C2 density measurement in carbon plume using laser-induced fluorescence spectroscopy

The temporal evolution and spatial distribution of C₂ molecules produced by laser ablation of a graphite target is studied using optical emission spectroscopy, dynamic imaging and laser-induced fluorescence (LIF) investigations. We observe peculiar bifurcation of carbon plume into two parts; stationary component close to the target surface and a component moving away from the target surface which splits further in two parts as the plume expands. The two distinct plumes are attributed to recombination of carbon species and formation of nanoparticles. The molecular carbon C₂ moves with a faster velocity and dies out at ~ 800 ns whereas the clusters of nanoparticle move with a slower velocity due to their higher mass and can be observed even after 1600 ns. C₂ molecules in the d³Π_g state were probed for laser-induced fluorescence during ablation of graphite using the Swan (0,0) band at 516.5 nm. The fluorescence spectrum and images of fluorescence d³Π_g − a³Π_u(0,1)(λ = 563.5 nm) are recorded using a spectrograph attached to the ICCD camera. To get absolute ground state C₂ density from fluorescence images, the images are calibrated using complimentary absorption experiment. This study qualitatively helps to get optimum conditions for nanoparticle formation using the laser ablation of graphite target and hence deducing optimum conditions for thin film deposition.     

Charge transport modulation of silicon nanowire by O2 plasma

The modification of the electrical characteristics of field-effect transistors (FETs) with channels composed of n- or p-type silicon nanowires (SiNWs) by oxygen plasma treatment is investigated in this study. The SiNWs obtained from silicon bulk wafers are <111> surface-oriented and their doping concentrations are 10²¹ and 10¹⁷ cm⁻³ for the n- and p-type SiNWs, respectively. After the back-gate SiNWFETs were subjected to oxygen plasma treatment, the magnitude of the drain current of the n-type SiNWs was decreased, whereas that of the p-type SiNWs was increased, while the gate-dependent characteristics of both of types of SiNWs were improved. The changes in the electrical characteristics are due to the adsorption of oxygen ions on the surface of the SiNWs. To verify the effect of the oxygen ions, the SiNWFETs were kept in a vacuum for 24 h whereupon their electrical characteristics tended to revert to their inherent state.     

Reduced N-methyl-pyridylethynyl porphyrins exhibit strong near-IR absorptions

Porphines bearing two N-methyl-4-pyridylethynyl substituent reversibly undergo two one-electron reductions at room temperature. The anion radicals and di-anions show diminished visible bands (450 nm and 600–700 nm) and intense absorptions in the 800-nm and 1100-nm region, respectively. Some of the near-IR bands have extinction coefficients greater than 1.5 × 10⁵ M⁻¹ cm⁻¹.     

Enhanced tungstate electrochromism via formation of transparent conductive networks

Indium tin oxide (ITO) nanopowder was added to a polymer film containing WO₃ · H₂O particles to enhance electron conductivity and complimentary Li ion kinetics in an electrochromic device. Film conductivity increased dramatically with ITO content, suggesting the formation of conductive ITO networks in the film. The improved electron conductivity leads to a substantial increase of the effective Li⁺ ion diffusion coefficient in the composite film, from 10⁻¹¹ to 10⁻⁹ cm²/s. Electrochromic contrast studies revealed that the presence of the ITO networks leads to enhanced blue/green color contrast.     

Existence of clathrate-like structures in supercooled water: X-ray diffraction evidence

X-ray diffraction study of supercooled water has been performed using an imaging-plate X-ray detector down to −15 °C. The peak at 10.8 Å, which grows with decreasing temperature, in the radial distribution function {D(r) − 4πr²ρ₀} indicates the existence of clathrate-like structures in supercooled water. It is suggested that anomalous properties of water, which become more pronounced at low temperatures, are closely linked to the development of clathrate-like structures in water at low temperatures.     

Excited state intramolecular proton transfer in a new o-hydroxy Schiff base in non polar solvents at room temperature and 77 K

A new orthohydroxy Schiff base, 7-ethylsalicylidenebenzylamine (ESBA) has been synthesised. The excited state intramolecular proton transfer (ESIPT) processes have been investigated by means of absorption, emission and nanosecond spectroscopy at room temperature and at 77 K in non polar solvents. The ESIPT is evidenced by a large Stokes shifted emission (11 000 cm⁻¹) only at 77 K. From fluorescence and excitation spectra it is suggested that at least three different species are present in the excited state at room temperature. Our theoretical calculation at AM1 level confirm the cis-isomer to be the only viable form in the ground state.     

Characterization of the aerosol produced by infrared femtosecond laser ablation of polyacrylamide gels for the sensitive inductively coupled plasma mass spectrometry detection of selenoproteins

A 2D high repetition rate femtosecond laser ablation strategy (2-mm wide lane) previously developed for the detection of selenoproteins in gel electrophoresis by inductively coupled plasma mass spectrometry was found to increase signal sensitivity by a factor of 40 compared to conventional nanosecond ablation (0.12-mm wide lane) [G. Ballihaut, F. Claverie, C. Pécheyran, S. Mounicou, R. Grimaud and R. Lobinski, Sensitive Detection of Selenoproteins in Gel Electrophoresis by High Repetition Rate Femtosecond Laser Ablation-Inductively Coupled Plasma Mass Spectrometry, Anal. Chem. 79 (2007) 6874–6880]. Such improvement couldn't be explained solely by the difference of amount of material ablated, and then, was attributed to the aerosol properties. In order to validate this hypothesis, the characterization of the aerosol produced by nanosecond and high repetition rate femtosecond laser ablation of polyacrylamide gels was investigated. Our 2D high repetition rate femtosecond laser ablation strategy of 2-mm wide lane was found to produce aerosols of similar particle size distribution compared to nanosecond laser ablation of 0.12-mm wide lane, with 38% mass of particles < 1 µm. However, at high repetition rate, when the ablated surface was reduced, the particle size distribution was shifted toward thinner particle diameter (up to 77% for a 0.12-mm wide lane at 285 µm depth). Meanwhile, scanning electron microscopy was employed to visualize the morphology of the aerosol. In the case of larger ablation, the fine particles ejected from the sample were found to form agglomerates due to higher ablation rate and then higher collision probability. Additionally, investigations of the plasma temperature changes during the ablation demonstrated that the introduction of such amount of polyacrylamide gel particles had very limited impact on the ICP source (ΔT~ 25 ± 5 K). This suggests that the cohesion forces between the thin particles composing these large aggregates were weak enough to have negligible impact on the ICPMS detection.     

Isoconversional kinetics of degradation of polyvinylpyrrolidone used as a matrix for ammonium nitrate stabilization

Thermogravimetric analyzer (TGA) has been applied to measure the kinetics of the thermal degradation of virgin polyvinylpyrrolidone (PVP) and a phase stabilized PVP–ammonium nitrate (AN) material. The PVP–AN samples have been prepared by using 20 wt.% of AN and PVP of three different molecular weights. Virgin PVP undergoes a major mass loss in the region 380–550 °C leaving a small amount of nonvolatile residue. The application of an advanced isoconversional method to the respective degradation process demonstrates that its effective activation energy increases from 70 kJ mol⁻¹ to a plateau value at 250–300 kJ mol⁻¹, which is independent of the molecular weight. The PVP–AN materials lose spontaneously 20% of their mass on heating above the glass transition temperature of the PVP matrix (160–180 °C). After the escape of AN, the remaining PVP matrix degrades in the same temperature region as virgin PVP, however, the effective activation energy of this degradation is 150–200 kJ mol⁻¹.     

Use of a graphite–polyurethane composite electrode for electroanalytical determination of indole-3-acetic acid in soil samples

A new electroanalytical methodology was developed for the quantification of the phytohormone indole-3-acetic acid (IAA), using a graphite–polyurethane composite electrode (GPU) and the square wave voltammetry (SWV), in 0.1 mol L^− 1 phosphoric acid solution (pH 1.6). Analytical curves were constructed under optimized conditions (f = 100 s^− 1, a = 50 mV, E_i = 5 mV) and the reached detection and quantification limits were 26 μg L^− 1 and 0.2 mg L^− 1, respectively. The developed methodology is simple and accurate for the routine determination of IAA. In order to verify the application of the electroanalytical methodology in fortified soil samples without previous treatment, an IAA assay was performed without serious interferences of the soil constituents.     

Electrochemical properties of polyaniline in p-toluene sulfonic acid solution

Polyaniline was deposited potentiodynamically on a stainless steel substrate in the presence of an inorganic acids (sulfuric acid). The electrochemical characterization of the electrode was carried out by means of cyclic voltammetry and electrochemical impedance spectroscopy in the organic acids (p-toluene sulfonic acid) solution. The results show that polyaniline has a high specific capacitance of 431.8 F g⁻¹ at 1 mV s⁻¹, high coulombic efficiency of 95.6% at 20 mV s⁻¹, and exhibits a high reversibility. This indicates the promising feasibility of the polyaniline used as an electrochemical capacitor material in the electrolyte of p-toluene sulfonic acid solution especially at high charge–discharge process.     

Interaction and photodynamic activity of cationic porphyrin derivatives bearing different patterns of charge distribution with GMP and DNA

The interaction of amphiphilic cationic porphyrins, containing different patterns of meso-substitution by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl (A) and 4-(trifluoromethyl)phenyl (B) groups, with guanosine 5′-monophosphate (GMP) and calf thymus DNA have been studied by optical methods in phosphate buffer solution. The properties of these synthetic porphyrins were compared with those of representative standard of anionic 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS₄⁴⁻) and cationic 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin (TMAP⁴⁺). Stable complexes with GMP were found for cationic porphyrins, except for monocationic AB₃⁺. The binding constant (K_GMP  10⁴ M⁻¹) follows the order: A₃B³⁺  ABAB²⁺ > A₄⁴⁺  TMAP⁴⁺. Also, interaction with DNA was observed for all evaluated cationic porphyrins. For these related cationic porphyrins, the binding constant (K_DNA  10⁵ M⁻¹) increases with the number of cationic charges. On the other hand, the photodynamic activity of porphyrins was analyzed in solution of GMP and DNA. Monocationic AB₃⁺ is a less effective sensitizer to oxidize GMP in comparison with the other cationic porphyrins, in agreement with the lack of detected interaction with this nucleotide. The electrophoretic analysis of DNA indicates that photocleavage takes place when the samples are exposed to photoexcited tricationic and tetracationic porphyrins. In the presence of sodium azide the DNA decomposition was diminished. Also, reduction in the DNA photocleavage was observed under anoxic condition, indicating that oxygen is essential for DNA photocleavage sensitized by these cationic porphyrins. In addition, an increase in DNA degradation was not observed in deuteriated water. Therefore, an important contribution of type I photoreaction processes could be occurring in the DNA photodamage sensitized by these cationic porphyrins. These results provide a better understanding of the characteristics needed for sensitizers to produce efficient DNA photocleavage.     

Electrochemical kinetics and cycling performance of nano Li[Li0.23Co0.3Mn0.47]O2 cathode material for lithium ion batteries

Li[Li_0.23Co_0.3Mn_0.47]O₂ cathode material was prepared by a sol–gel method. The material had a primary particle size of about 100 nm, covered by a 30 Å of Li₂CO₃ layer. The material showed promising electrochemical performance when cycled up to 3C rate. The electrochemical kinetics of the first charge was much slower than that of the second charge, due to the complex electrochemical process which involved not only Li⁺ diffusion but also release of oxygen. By taking account of this, the material was pre-charged very slowly (C/50) in the first cycle. This led to excellent electrochemical performance in the following cycles. For instance, the 1C-rate capacity increased to 168 mA h g⁻¹ after 50 cycles, comparing with the 145 mA h g⁻¹ obtained without pre-charging.     

Effect of small amount of poly(ethylene naphthalate) on isothermal crystallization and spherulitic morphology of poly(trimethylene terephthalate)

The effect of a small amount of poly(ethylene naphthalate) (PEN) in its blends with poly(trimethylene terephthalate) (PTT) on isothermal melt-crystallization kinetics and spherulitic morphology of the blends was thoroughly investigated. The maximum PEN content in the blends was 9 wt%. Due to the single composition-dependent glass transition temperature (T_g) that was observed for each blend, these blends appeared to be miscible in the amorphous state. After isothermal crystallization from the melt state, the neat PTT and its blends with PEN exhibited either double or triple melting endotherms. The triple endothermic peaks were observed in both the neat PTT and the blends when being crystallized at crystallization temperatures (T_c) of less than or equal to 195 °C. The equilibrium melting temperature () for the neat PTT was determined based on the linear Hoffman–Weeks extrapolative method to be 248 °C. Such values for the blends were found to decrease with the addition and increasing amount of PEN. Both the neat PTT and the blends were isothermally crystallized over the T_c range of 190–205 °C. At a given T_c, the 97PTT/3PEN blend exhibited a half-time of crystallization (t_0.5) value that was lower, while it exhibited reciprocal half-time (), Avrami rate constant (K_A), and spherulitic growth rate (G) values that were greater, than those of the neat PTT. With further increase in the PEN content, the t_0.5 value increased, while the , K_A, and G values decreased. Analysis of the G values based on the Lauritzen–Hoffman's (LH) secondary nucleation theory showed that the neat PTT and the 91PTT/9PEN blend exhibited a regime II→III transition at 194 °C (467.2 K), while no regime transition was observed for the other two blends. The lateral and the fold surface free energies (σ and σ_e) and the work of chain folding (q) for the neat PTT and the blends were 19.4, 30.2–46.3 erg cm⁻², and 2.4–3.6 kcal mol⁻¹, respectively. Lastly, the effect of both the T_c and the PEN content on morphology and texture of the PTT spherulites was also investigated and the results showed that the texture of the spherulites became coarser with increasing T_c and PEN content.     

Towards the characterization of metal binding proteins in metal enriched yeast

This paper presents size exclusion chromatography data with on-line coupling to UV and inductively coupled plasma mass spectrometry (ICP-MS) of water soluble metal-binding compounds present in zinc, copper, chromium and iodine enriched yeast nutritional supplements. Molecular weight estimates of the extracted metal-containing compounds are given and are shown to vary substantially from 1.2 kDa to larger than 668 kDa. Seven proteins suspected of containing chromium were identified from one of the chromium-containing fractions. Four of these identified proteins are known to form complexes with other metal ions. The metal chromatographic profiles of zinc, copper and chromium-enriched yeasts were compared to their respective native metal profiles in non-enriched yeast samples. The chromium profiles are shown to be markedly different while those of zinc and copper are qualitatively similar. Only iodide ions or weakly bound, non-aromatic, low molecular weight ( 1.2 kDa) iodine species were observed in the iodine-enriched yeast samples.     

Negatively charged micelles directed synthesis of snow-ball flower like superparamagnetic Ni nanoparticles and investigation of their properties

Snow-ball flower like Ni nanoparticles have been synthesized using negatively charged micelles. Negatively charged micelles incorporate the Ni⁺² onto its head group by electrostatic attraction and again a surfactant layer is arranged on positively charged Ni and thus in a repetitive way layer-by-layer a snow-ball flower like structure is formed. After reduction of Ni⁺² to Ni atom by sodium borohydride and hydrated hydrazine the Ni clusters (3 nm) are formed and confined in micelles in snow-ball flower like pattern. The sizes of these nanoflowers are of 30 nm order. The particles are superparamagnetic in nature with blocking temperature about 117 K.     

Effect of high rates of mass transport on oxygen reduction at copper electrodes: Implications for aluminium corrosion

The reduction of oxygen at copper microelectrodes (25 μm diameter) in aqueous solution (pH 7) has been studied under conditions of high mass transport, similar to those experienced by μm sized copper-containing inclusions in aluminium alloys during corrosion. Contrary to previous studies at copper electrodes operating at lower mass transport rates, oxygen reduction limiting currents show an apparent number of electrons which decrease towards 2 as the mass transport rate increases (mass transfer coefficients up to ca. 0.55 cm s⁻¹), rather than a 4-electron process. These new data suggest that the treatment of oxygen reduction as a 4-electron transfer process at micron and smaller-sized copper intermetallics in aluminium alloys may require revision.     

An octane-fueled low temperature solid oxide fuel cell with Ru-free anodes

A Ru-free anode was developed for the direct utilization of iso-octane in low temperature solid oxide fuel cells (SOFCs). The anode was consisted of a Ni framework and a nano-sized oxygen–ion conductor, samaria-doped ceria (SDC), which was coated onto the inner surface of the framework via an ion impregnation process. Compared with the cells based on conventional Ni–SDC anodes, single cells with the SDC-coated Ni anodes exhibited improved stability and enhanced electrochemical activity. Peak power density of 400 mW cm⁻² was achieved at 600 °C, and power generation was relatively stable over 260 h when iso-octane–air mixture was directly used as the fuel. The performance is comparable with those obtained using ceria-Ru as an internal reforming catalyst.     

Molecular fine structure and transition dipole moment of NO2 using an external cavity quantum cascade laser

Rotational vibrational fine structure and transition dipole moment of NO₂ is measured using Doppler free saturation spectroscopy with an external grating cavity quantum cascade laser (QCL). The QCL wavelength is calibrated using a 310 cm long internally coupled Fabry–Perot interferometer. We obtain a frequency splitting of 139.68 ± 0.06 MHz (0.0047 cm⁻¹) between the spin doublets (17) of 000 → 001 transition of NO₂. The resolution of the QCL based saturation spectrometer is limited by the QCL linewidth of 3.99 MHz ( 0.00013 cm⁻¹) deduced from the half width of the Lamb dips. The Lamb dip spectroscopy is utilized to obtain a vibrational dipole moment of 0.37 Debye for the (17) transitions.