Coupled chemical reactions in dynamic nanometric confinement: IV. Ion transmission spectrometric analysis of nanofluidic behavior and membrane formation during track etching in polymers

In recent papers, it was shown that coupled chemical-topological reactions (CCRs) with both NaOH etchant and silver salts, performed in thin swift-heavy ion-irradiated polymers under the application of a test voltage across the polymer foils, eventually gave rise to characteristic current/voltage features and Bode plots that were tentatively attributed to the formation of Ag₂O membranes within the etched tracks. The same was also found when replacing the silver ions by lithium ions, and adding fluoride ions to the NaOH etchant, to promote LiF membrane formation. Ion Transmission Spectrometry (ITS) enabled us to reconfirm the existence of these membranes beyond doubt. The membrane thickness was determined to be ～0.2–0.4?µm in the best cases.

ITS also revealed that hitherto membrane formation occurs only in ～1% of all tracks, or even less. The reason for this poor abundance seems to be that the decisive factor for membrane formation, which is the firm anchoring of the emerging solid Ag₂O or LiF reaction products on the etched track walls, was hitherto rarely fulfilled. We attribute this tentatively to the too high test voltage applied for controlling the CCR process that might hinder the product anchoring on the walls by promoting nanofluidic electromigration. Indeed, voltage reduction seems to improve the situation.     

Efficient mid-IR spectral generation via spontaneous fifth-order cascaded-Raman amplification in silica fibers

Spontaneous cascaded Raman amplification is demonstrated as a practical and efficient means of power transfer from telecommunications wavelengths to mid-IR wavelength bands through use of conventional silica fibers and amplifiers. We show that silica fibers possessing normal dispersion over all near-IR and mid-IR wavelengths can facilitate 37% and 16% efficient Raman power conversion from 1.53 microm to 2.15 and 2.41 microm wavelength bands, respectively, using nanosecond pulses from an all-fiber laser source. In contrast to supercontinuum-based techniques for long-wavelength generation, the high levels of Raman gain generated at these wavelength bands could produce useful optical amplification necessary for the development of numerous mid-IR laser sources.     

Ion track etching revisited: II. Electronic properties of aged tracks in polymers

We compile here electronic ion track etching effects, such as capacitive-type currents, current spike emission, phase shift, rectification and background currents that eventually emerge upon application of sinusoidal alternating voltages across thin, aged swift heavy ion-irradiated polymer foils during etching. Both capacitive-type currents and current spike emission occur as long as obstacles still prevent a smooth continuous charge carrier passage across the foils. In the case of sufficiently high applied electric fields, these obstacles are overcome by spike emission. These effects vanish upon etchant breakthrough. Subsequent transmitted currents are usually of Ohmic type, but shortly after breakthrough (during the track’ core etching) often still exhibit deviations such as strong positive phase shifts. They stem from very slow charge carrier mobility across the etched ion tracks due to retarding trapping/detrapping processes. Upon etching the track’s penumbra, one occasionally observes a split-up into two transmitted current components, one with positive and another one with negative phase shifts. Usually, these phase shifts vanish when bulk etching starts. Current rectification upon track etching is a very frequent phenomenon. Rectification uses to inverse when core etching ends and penumbra etching begins. When the latter ends, rectification largely vanishes. Occasionally, some residual rectification remains which we attribute to the aged polymeric bulk itself. Last not least, we still consider background currents which often emerge transiently during track etching. We could assign them clearly to differences in the electrochemical potential of the liquids on both sides of the etched polymer foils. Transient relaxation effects during the track etching cause their eventually chaotic behaviour.     

Arsenvergiftungen

The development of legal verification from torture via post mortem examination to chemical and radiochemical detection methods is shown by means of some spectacular cases of arsenic poisoning from the 17^th to the 20^th century. Because of the omnipresence of arsenic, it was not always possible to resolve all doubts.     

Confirmation of n-Hexane as an Inert Co-Solvent in the Production of Functionalized Silicon Nanoparticles from Reactive High-Energy Ball Milling

Alkanes such as n-hexane have been used as co-solvents in the production of functionalized semiconductor nanoparticles from alkenes and alkynes using Reactive High Energy Ball Milling (RHEBM) under the assumption that they are non-reactive under typical milling conditions. In this paper, a comparative study with two hydrocarbon solvents of comparable chain length, 1-hexyne, and n-hexane, and their milling products using three different commercially available silicon precursors, namely single crystal silicon wafers and polycrystalline particles having a nominal size of 4 µm and 1 mm, is reported. It is found that nanoparticle formation and surface functionalization in all the three silicon systems occurs only with 1-hexyne; n-hexane is non-reactive and does not lead to appreciable functionalized nanoparticle formation under the conditions studied. Nanoparticles (where formed) and microparticle byproducts of appropriate samples are characterized by Transmission electronic microscope (TEM), Fourier transform infrared  (FTIR), Photoluminiscence spectroscopy (PL), Nuclear magnetic resonance ¹H/¹³C NMR, and thermogravimetry TGA to separately confirm nanoparticle formation and surface functionalization.     

Design of a flexible but robust setup for temperature-dependent electrochemistry down to cryogenic temperatures

Electrochemistry and its analytics are essential in a variety of scientific and technological fields where properties related to reduction-oxidation reactions, so-called redox properties, are to be explored. While methodological standards for experiments are well established at room temperature, this is still untrue at sub-zero/cryogenic temperatures, the conditions required for the survey of (ultra−)rapid processes and their intermediates. Problems due to “hand-waving” temperature regulation/conditioning and common usage of pseudo-reference electrodes renders cryo-electrochemistry a great challenge. Herein, we describe a robust setup for performing reliable cryo-electrochemical experiments down to −80 °C. It combines highly stable but flexible temperature conditioning with gas-tight sealing of the electrochemical cell setup. Modification of a commercial palladium hydride reference electrode (PdH RE) allows for rapid temperature cycling under cryogenic conditions in aprotic organic solvents. Validation of the setup with the well-known Ferrocene|Ferrocenium (Fc|Fc⁺) redox couple gave good compliance with literature data at room temperature in a range of organic solvent-based electrolytes. Evaluation of temperature-dependent diffusion kinetic parameters, such as diffusion coefficients (D) and diffusional activation energies (E_a,D) from CVs at multiple potential scan-rates and temperature levels emphasize the reliability of the presented cryo-electrochemical setup.