Water‐Soluble Triazabutadienes that Release Diazonium Species upon Protonation under Physiologically Relevant Conditions

Triazabutadienes are an understudied structural motif that have remarkable reactivity once rendered water‐soluble. It is shown that these molecules readily release diazonium species in a pH‐dependent manner in a series of buffer solutions with pH ranges similar to those found in cells. Upon further development, we expect that this process will be well suited to cargo‐release strategies and organelle‐specific bioconjugation reactions. These compounds offer one of the mildest ways of generating diazonium species in aqueous solutions.     

Quenching Action of Monofunctional Sulfur Mustard on Chlorophyll Fluorescence: Towards an Ultrasensitive Biosensor

An ultrasensitive fluorimetric biosensor for the detection of chemical warfare agent sulfur mustard (SM) was developed using its monofunctional analogue. SM is a vesicant and a potent chemical threat owing to its direct toxic effects on eyes, lungs, skin and DNA. This work investigates the quenching action of the analyte on chlorophyll fluorescence as elucidated by nuclear magnetic resonance, Fourier transform infrared spectroscopy and mass spectrometry studies suggesting the electrophilic attack of carbonium ion on nitrogens of the porphyrin moiety of chlorophyll. The properties of immobilisation matrix were optimised and scanning electron microscope observations confirmed improvement in pore size of sol–gels by addition of 32 % (v/v) glycerol, a feature enabling enhanced sensitivity towards the analyte. Chlorophyll embedded sol–gel was treated with increasing concentrations of monofunctional SM and the corresponding drop in maximum fluorescence intensity as measured by emission at 673 nm was observed, which varied linearly and had a detection limit of 7.68?×?10^?16 M. The biosensor was found to be 6 orders of magnitude more sensitive than the glass microfibre-based disc biosensor previously reported by us.     

Mercury determination in sediments by CVAAS after on line preconcentration by solid phase extraction with a sol-gel sorbent containing CYANEX 471X®

The development of a preconcentration method for the measurement of trace levels of mercury in digested sediments is described. Solid phase extraction (SPE) was used for the preconcentration of mercury coupled on-line by means of a flow injection (FI) system followed by cold vapour atomic absorption spectrometry (CVAAS) detection. The SPE was carried out through a column packed with a sorbent material containing triisobutylphosphine sulfide (CYANEX 471X®) as mercury extractant and prepared by the sol-gel process. The effects of FI variables (argon, eluent, and reductant flow rates, loading and elution times) as well as the eluent concentration on the analytical performance of the method were evaluated. The proposed method was validated under the optimum conditions. The calibration graph was linear from 0.05?µg?L^?1 to 3.0 µg?L^?1 of Hg. The detection limit (DL), based on three times the standard deviation of the blank measurement criterion, was 24?ng^?L^?1. The repeatability was 1.5% and 1.8% RSD (n?=?10) at concentrations of 0.5 and 1 µg?L^?1 of Hg, respectively. Method enrichment factors of 16 with a productivity of 30 samples h^?1 or 32 with a productivity of 17 samples h^?1 were achieved under selected conditions. Certified reference materials, inductively coupled plasma mass spectroscopy (ICP-MS) and cold vapour atomic fluorescence spectrometry (CVAFS), were used to evaluate the accuracy of the proposed method.     

NMR spectra of seleninium and 1- and 2-benzoseleninium cations

The analysis of the NMR spectra of seleninium and 1-and 2-benzoseleninium cations, recorded in deuterotrifluoroacetic acid, is reported. The effects of condensation on the spectral parameters of the protons of the seleninium ring were examined with particular reference to the shift to higher values of δ: this was consistent with the q values calculated by the HMO method. The ³J(HH) and ⁴J(HH) variations, including an interesting variation regarding the through-selenium ⁴J coupling, are also discussed.     

The acid dissolution of sulfide mineral samples under pressure in a microwave oven

A system for the rapid dissolution of sulfide samples from mines, mills and smelters is described. The samples and an acid mixture are placed in sealed teflon-PFA vessels, which are then heated in a microwave oven for 3 min. Following the dissolution, metals of interest (copper and nickel) are quantified by atomic absorption spectrometry. The system described produces significant savings in time and materials and increased output and efficiency in comparison with traditional methods; it is also much cleaner. Results are similar to those obtained with a more conventional dissolution method     

Identification of bubble evolution mechanisms during AC electrograining

Bubble evolution during AC-graining is analysed in combination with the variation of the anodic peaks of the potential and the electrode surface morphology. Aluminium samples are grained in hydrochloric acid in an Inverted Rotating Disk Electrode. A roughness tester is used to characterise the electrode surface, while shadow imaging is applied to determine the bubble size distribution. An interpretation of the correlation existing among bubble size, potential peaks evolution, surface properties and smut layer formation is proposed, which provides insights into the mechanisms involved in bubble formation.     

CO adsorption on gold clusters stabilized on ceria-titania mixed oxides: comparison with reference catalysts

Fourier transform infrared spectra of CO adsorption from 120 K up to room temperature on two gold catalysts supported on different mixed ceria-titania oxides are discussed in comparison with those obtained on Au/TiO(2) and Au/Fe(2)O(3) reference catalysts provided by the World Gold Council. The spectra of adsorbed CO, run on the different samples before preliminary treatment, are shown and compared with those of the untreated catalysts and of the samples reduced either in CO or in hydrogen. Big differences have been found between the ceria-titania supported samples and the reference ones: unusual absorption bands, irreversible to outgassing, have been detected after CO interaction on the untreated and oxidized ceria containing samples. These absorptions are assigned to CO on Au(n)(+) small clusters stabilized at the ceria defects. By reduction in hydrogen, negatively charged Au(n)(-) species are produced on the same sample. Oxidized small particles are present on the reference catalysts, but only on the untreated samples; after treatment, only metallic step sites are evident.     

Investigation of a highly saturated soft X-ray amplification in a capillary discharge plasma waveguide

The characterization of the laser beam intensity distribution of a highly saturated 46.9-nm soft X-ray laser excited by capillary discharges is reported. The laser produces a total output energy of 300 J/pulse by amplification in plasma channels having lengths up to 0.45 m. A regime of laser amplification, which is almost free from the effect of the refraction defocusing, is experimentally determined. This regime produces a soft X-ray laser beam with an intense sub-milliradiant component. In the longer active medium the laser intensity distribution reaches the divergence of 0.6 mrad, which approaches the limit of diffraction. A comparison of the experimental results with the simulations performed with a ray-tracing code shows that the small divergence of the beam could be attributed to the effect of a weak index waveguiding of the laser beam through the long plasma channels. PACS 42.55.Vc; 42.60.Jf     

Mapping of the metal intake in plants by large-field X-ray microradiography and preliminary feasibility studies in microtomography

This paper reports on dual energy micro-radiography and tomography techniques applied both to thin plant leaves treated with copper or lead solutions and on Cu-treated small roots and stem sections, performed at the SYRMEP X-ray beamline of ELETTRA synchrotron facility in Trieste (Italy). The features of the source allowed us to apply different imaging techniques with an extremely vast field of view, up to 160 ×6 mm2 and 28×6 mm2 for micro-radiography and tomography experiments, respectively. The feasibility of getting positive indications on metal accumulation in leaves, sections of roots and stems, stem and root whole cylindrical pieces has been checked.     

Dendritic incorporation of quinacridone: solubility, aggregation, electrochemistry, and solid-state luminescence

The first incorporation of quinacridone, a technologically important organic electroluminescent emitter, into dendrimers increases solubility, decreases aggregation, retards heterogeneous electron transfer, and enhances luminescence in condensed phases (powders and thin films).