Polymers of intrinsic microporosity as high temperature templates for the formation of nanofibrous oxides

The highly rigid molecular structure of Polymers of Intrinsic Microporosity (PIM) – associated with a high thermolysis threshold – combined with the possibility to fill intrinsic micropores allows the direct “one-step” templated conversion of metal nitrates into nano-structured metal oxides. This is demonstrated here with PIM-EA-TB and with PIM-1 for the conversion of Pr(NO3)3 to Pr6O1

Microfluidic microneedle or micropipet comprising a nanogap sensor for analytical applications

The invention provides asensor device comprising a substrate, especially a needle with a needle tip, wherein the substrate, especially the needle, even more especially the needle tip, comprises a sensor unit, wherein the sensor unit includes a stacked layer structure including an electrode layer, wherein the stacked layer structure further includes a nanogap dividing the electrode layer in a first electrode and a second electrode with the nanogap in between, wherein the nanogap has a width (w) selected from the range of 10-500 nm, such as from the range of 20-200 nm, and wherein in a specific embodiment the needle further comprises a microfluidic channel structure with an orifice, wherein the orifice is especially arranged at the needle tip, for delivery or extraction of a fluid.ChemE/Chemical EngineeringApplied Science

Microwave-Enhanced Electrochemistry in Locally Superheated Aqueous-Glycerol Electrolyte Media

Microwave activation, when applied to metal disk electrodes immersed in aqueous electrolyte media, causes highly localized heating of the liquid dielectric at the tip of the electrode. This is usually resulting in vapor bubble nucleation, cavitation, liquid jet formation, and boiling close to the electrode surface. However, when conducted in the presence of glycerol, boiling and vapor bubble formation appear to be suppressed and considerable superheating effects can be observed locally at the electrode surface. At a 50 μ m diameter platinum disk electrode immersed in aqueous solution containing 0.1 M KCl supporting electrolyte, 5 mM Fe(CN)63-, and 5 mM Fe(CN)64- as a temperature-sensitive redox probe, and a 40 vol % glycerol content, apparent electrode temperature of up to ca. 480 K (estimated) can be reached under conditions of continuous microwave irradiation (in steady state mode). The effects of viscosity and temperature on the mass transport controlled limiting current are investigated. The use of glycerol-aqueous media (or other similar boiling suppressing mixtures) makes feasible the study of chemical and electrochemical processes under hydrothermal and superheating conditions. © 2009 American Chemical Society

Microwave-enhanced electroanalytical processes: generator-collector voltammetry at paired gold electrode junctions.

Generator-collector electrode systems allow redox processes and reaction intermediates from multi-step electrode reactions to be monitored. Analytically, collector electrode current responses are insightful and highly sensitive due to (i) the absence of capacitive current components and (ii) an enhanced current response due to 'feedback' between generator and collector electrode. Here, a symmetric gold-gold junction grown by controlled electro-deposition is employed for generator-collector voltammetry in conjunction with microwave activation. Three redox systems are investigated in aqueous 0.1 M KOH: (i) the reduction of Fe(CN)(6)(3)(-), (ii) the reduction of chloramphenicol, and (iii) the reduction of oxygen. Microwave radiation, when focused into the electrode-solution interfacial zone, causes locally enhanced temperatures with electrode surface temperatures reaching up to typically 380 K (estimated from the shift in the Fe(CN)(6)(3)(-/4)(-) equilibrium potential, at both gold electrodes). The resulting increase in the rate of diffusion and the onset of convection result in non-linear Arrhenius limiting current characteristics and in an increase in collection efficiency with microwave power. The gold electrode junction geometry allows diffusion effects (which increase the feedback current within the gap) to dominate over convection effects (which suppress the feedback current)

Challenges of Biomolecular Detection at the Nanoscale: Nanopores and Microelectrodes

The interest in analytical devices, which typically rely on the reactivity of a biological component for specificity, is growing rapidly. In this Perspective, we highlight current challenges in all-electrical biosensing as these systems shrink toward the nanoscale and enable the detection of analytes at the single-molecule level. We focus on two sensing principles: nanopores and amperometric microelectrode devices

Arsenite determination in phosphate media at electroaggregated gold nanoparticle deposits

Compared to bulk gold, highly reactive mesoporous gold film deposits are prepared on a boron-doped diamond electrode surface. An electroaggregation process causing 5 nm diameter gold nanoparticles to deposit cathodically from aqueous solution is implemented to control the amount of mesoporous gold at the electrode surface. The resulting electrode surface is characterized by electron microscopy and by cyclic voltammetry. The reactivity of the electroaggregated gold deposit towards arsenite is investigated in nitric acid media and in neutral phosphate buffer media. Three processes consistent with (i) cathodic deposition of arsenic metal (As(III) → As(0)), (ii) anodic stripping (As(0) → As(III)), and oxidation of arsenite (As(III) → As(V)) are observed and shown to shift in potential with approximately 58 mV per pH unit (Nernstian at 20°C). Improved anodic stripping voltammetry responses for solutions of arsenite(III) in 0.1 M HNO3 and in 0.1 Mphosphate buffer solution are observed as the gold nanoparticle deposition time is increased. Typical detection limits of LOD(3σ) = 30 ppb in nitric acid and LOD(3σ) = 1 ppb in phosphate buffer (pH 7) are observed. © 2008 Wiley-VCH Verlag GmbH and Co. KGaA