Immobilisation of redox active molecules as precursors for nanowire self-assembly

Spontaneously adsorbed monolayers of [Co(ttp-CH2-SH)2](PF6)2 have been formed on platinum microelectrodes by exposure to micromolar solutions of the complex in 0.1 M TBABF4 in acetonitrile, ttp-CH2-SH is 4'-(p-(thiolmethyl)-phenyl)-2,2':6',2''- terpyridine. Resonance Raman spectroscopy on roughened polycrystalline platinum macro electrodes show that the molecule undergoes adsorption by sulphur atom onto the platinum surface. The monolayers show reversible and well defined cyclic voltammetry when switched between Co2+ and Co3+ forms, with a peak to peak splitting of 0.040±0.005 V up to 200Vs'' and an FWHM of 0.138±0.010 V. Adsorption is irreversible leadi* ng to the maximum surface coverage, 6.3±0.3xl0‘ 1 m1 olc2m' for 2.5<[Co(ttp-Ctf2-SH)2]<10 (o,M. The rate of monolayer formation appears to be controlled not by mass transport or interfacial binding but by surface diffusion of the complex. The surface diffusion coefficient is 5 .5± l.lx l0 '7 cm V indicating that prior to formation of an equilibrated monolayer, the adsorbates have significant mobility on the surface. The electron transfer process across the monolayer-electrode interface has been probed by high speed chronoamperometry and the standard heterogeneous electron transfer rate constant, k°, is approximately 3.06±0.03xl04 s '1. The reorganization energy is. 18.5 kJmol'1. Self-assembled monolayers of pentanethiol-beta-cyclodextrins have been immobilised on gold polycrystalline macroelectrodes and electrochemically and spectroscopically characterised. The adsorption dynamics was followed by monitoring the change in capacitance during time and a surface diffusion process was found to be the rate determining step. The layers appear to have a mixed structure most likely between a hexagonal close-packed monolayer and a brick configuration. Blocking behaviour depends on the hydrophobicity of the solution phase redox active probe. Scan rate dependent cyclic voltammetry has been used to characterise the defect density within the assemblies. In general, the layers are stable enough in time and potential window to probe the host-guest properties of the immobilized cyclodextrin cavities. The modified gold electrodes were exposed to micromolar solutions of cobalt biphenylterpyridine, in order to electrochemically and spectroscopically characterise the inclusion process. The host-guest reaction occurred for the in-situ experiments and it was characterised in terms of equilibrium constant, 2.78±0.7><104 M'1, and free Gibbs energy of inclusion, 25 kJ m ol1. Finally, control experiments of the adsorption of the redox active probe onto the bare gold electrodes further confirmed the occurring of the inclusion

El feminismo en cueros

Fil: Campagnoli, Mabel Alicia. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina

Experimental Investigation on Thermal Conductivity and Thermal Diffusivity of Water-Agar Gel from Room Temperature to –60℃

From a thermal point of view, water-agar gel can reproduce the behavior of human soft tissues with a good approximation. For this reason, agar gel is widely used to mimic the thermal diffusion inside the latter, in order to study the effect on human tissues of new techniques and probes used to solve various health diseases. Cryoablation is part of these techniques and its effectiveness strongly depends on the biological response of the tissues to the freezing action and heat diffusion and therefore on their thermo-physical properties. This study presents the values of thermal conductivity and thermal diffusivity, measured on water-agar gel samples, using the transient plane source method, forward and backward from room temperature down to −60℃. The freezing transient and the temperature at which the phase transition begins are highlighted, as well as the temperature dependence of both thermal conductivity and diffusivity

The elusive thomson effect in thermoelectric devices. Experimental investigation from 363 k to 213 k on various peltier modules

At steady state, in the governing equation of one-stage thermoelectric cooler, the heat resulting from Fourier conduction is balanced by heat generation due to the Joule and Thomson effects inside semiconductors. Since the heat flux observed at the junction of a semiconductor, r pair includes the Peltier effect and the Fourier heat flux caused by both the aforementioned contributions, the Thomson effect is easily masked by the Joule heat, which makes it elusive. With the aim of highlighting the contribution of the Thomson effect, measurements were carried out in the temperature range from 363 K to 213 K on different Peltier modules. The temperature dependence of the Seebeck and Thomson coefficients was evaluated as well as the electrical resistivity, and thermal conductivity of the Peltier modules examined. The results obtained show that the temperature dependence of the thermoelectric properties can reduce the cooling capacity of the Peltier module compared to what is declared in the technical datasheets of the commercial devices. The analyses allow us to conclude that an increase in the Thomson effect could have a positive effect on the performance of the Peltier only if it were possible to reduce the Joule contribution simultaneously

Preliminary investigation on thermal behavior of vehicles in different climate conditions

The objective of this paper is to provide an initial estimate, albeit rough, about the possible energy savings that can be achieved by reducing the use of the air condition system in cars. A simplified numerical model of the car has been created to predict the cabin temperature in different climatic conditions. In order to reduce the thermal load and so the temperature inside the cabin several different types of glazing have been considered, characterized by different absorbance coefficients and solar factors. Furthermore, two types of coatings with different absorbance coefficients were examined for the envelope. The paper describe

Surface plasmon enhanced absorption and suppressed transmission in periodic arrays of graphene ribbons

Resonance diffraction in the periodic array of graphene micro-ribbons is theoretically studied following a recent experiment [L. Ju et al, Nature Nanotech. 6, 630 (2011)]. Systematic studies over a wide range of parameters are presented. It is shown that a much richer resonant picture would be observable for higher relaxation times of charge carriers: more resonances appear and transmission can be totally suppressed. The comparison with the absorption cross-section of a single ribbon shows that the resonant features of the periodic array are associated with leaky plasmonic modes. The longest-wavelength resonance provides the highest visibility of the transmission dip and has the strongest spectral shift and broadening with respect to the single-ribbon resonance, due to collective effects.Comment: 5 pages, 3 figure