1000 resultados para selective encryption


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We demonstrate the complete, rapid, and reversible switching between the emissions from two electrogenerated chemiluminescence (ECL) systems contained within the same solution, controlled by simple modification of the applied potential. The fundamental bases of the approach are the ability to selectively 'switch on' luminophores at distinct oxidation potentials, and an intriguing observation that the emission from the well-known electrochemiluminescent complex, fac-Ir(ppy)3, (where ppy is 2-phenylpyridinato), can be selectively 'switched-off' at high overpotentials. The dependence of this phenomenon on high concentrations of the co-reactant implicates quenching of the excited [Ir(ppy)3]* state by electron transfer. Rapid spectral scanning during modulation of the applied potential reveals well resolved maxima for mixtures comprising either green and red or green and blue luminophores, illustrating the vast potential of this approach for multiplexed ECL detection.

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The selective increase in the oxidation rate of certain organic compounds with permanganate in the presence of environmental "ligands" and reduced species has been ascribed to the different reactivity of the target compounds toward Mn(III), which bears striking similarities to recent independent investigations into the use of permanganate as a chemiluminescence reagent. In spite of the importance of Mn(III) in the light-producing pathway, the dependence of the oxidation mechanism for any given compound on this intermediate could not be determined solely through the emission intensity. However, target compounds susceptible to single-electron oxidation by Mn(III) (such as bisphenol A and triclosan) can be easily distinguished by the dramatic increase in chemiluminescence intensity when a permanganate reagent containing high, stable concentrations of Mn(III) is used. The differences are accentuated under the low pH conditions that favor the chemiluminescence emission due to the greater reactivity of Mn(III) and the greater influence of complexing agents. This study supports the previously postulated selective role of ligands and reducing agents in permanganate oxidations and demonstrates a new approach to explore the chemistry of environmental manganese redox processes.

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Nanostructured bainitic steels, containing bainitic ferrite laths and retained austenite films, formed at two different isothermal temperatures were compared  for corrosion behavior in chloride-containing solution using electrochemical techniques. The potentiodynamic polarization results suggest that nanostructured bainite formed at 200 °C exhibits marginally higher corrosion resistance compared with that at 350 °C. Post-corrosion analysis of the galvanostatically polarized samples revealed localized corrosion for both the steels, but the degree of attack was higher in the 350 °C steel than in the 200 °C steel. The localized corrosion attack was due to selective dissolution of the retained austenite phase. The higher volume fraction and larger size of retained austenite in the 350 °C steel as compared to that of the 200 °C steel contributed to the pronounced corrosion attack in the 350 °C steel.

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A highly sensitive and selective dopamine sensor was fabricated with the unique 3D carbon nanotube nanoweb (CNT-N) electrode. The as-synthesised CNT-N was modified by oxygen plasma to graft functional groups in order to increase selective electroactive sites at the CNT sidewalls. This electrode was characterized physically and electrochemically using HRSEM, Raman, FT-IR, and cyclic voltammetry (CV). Our investigations indicated that the O2-plasma treated CNT-N electrode could serve as a highly sensitive biosensor for the selective sensing of dopamine (DA, 1 μM to 20 μM) in the presence of ascorbic acid (AA, 1000 μM).