Atomic force microscopy characterization of an electrochemical DNA-biosensor

Electrode surface characteristics represent an important aspect on the construction of sensitive DNA electrochemical biosensors for rapid detection of DNA interaction and damage. Two different immobilization procedures of double-stranded DNA (dsDNA) at the surface of a HOPG electrode were evaluated by MAC mode AFM performed in air. A thin dsDNA adsorbed film forming a network structure with holes exposing the electrode surface and a thick dsDNA film completely covering the electrode surface, presenting a much rougher structure, were investigated. The DNA surface characteristics and structure are discussed with respect to the degree of surface coverage.     

Investigation of Medium Power Radiofrequency Capacitively Coupled Plasmas and Their Application to Atomic Emission Spectrometry for the Determination of Aluminium in Water Samples

A medium power radiofrequency capacitively coupled plasma (275W, 27.12MHz) with low argon consumption (0.5Lmin^–1) was investigated to be used for the determination of aluminium in water samples pneumatically nebulised by atomic emission spectrometry. The plasma torch was operated in two geometric configurations, coaxial and coaxial-annular with single (SRTr.f.CCP) or double ring electrodes (DRTr.f.CCP), respectively. The optimum experimental parameters (observation height, Ar flow rate, distance between ring electrodes, matrix interference of Na⁺ and Ca²⁺ and anion nature) for Al 396.152nm emission were established. Under optimum operating conditions of the DRTr.f.CCP torch (6cm distance between annular electrodes), a detection limit of 70ngmL^–1 aluminium was found. Both operating parameters and several figures of merit of the investigated plasmas were compared to those of microwave plasmas and inductively coupled plasma used in atomic emission spectrometry. The method was used to control the quality of drinking and industrial water. Samples were mineralised with 2mL of 1+1 HNO₃ and 10mL of 1+1 HCl. In the range of 0.15–3.5mgL^–1 Al³⁺ the relative standard deviation varied between 3.7 and 8.6% (n=3). For two certified drinking water samples containing 0.206 and 0.218mgL^–1 Al³⁺ the recovery (n=5) was 97.6±6.8% and 98.6±7.3%, respectively.     

Methane synthesis from CO/H2O mixture on supported nickel catalysts, I. Influence of the support on the catalytic properties

The behavior of some supported Ni catalysts for methane synthesis from CO and steam in correlation with the specific metal-support interactions is discussed.

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Palladium nanoparticles and nanowires deposited electrochemically: AFM and electrochemical characterization

Palladium nanoparticles and nanowires electrochemically deposited onto a carbon surface were studied using cyclic voltammetry, impedance spectroscopy and atomic force microscopy. The ex situ and in situ atomic force microscopy (AFM) topographic images showed that nanoparticles and nanowires of palladium were preferentially electrodeposited to surface defects on the highly oriented pyrolytic graphite surface and enabled the determination of the Pd nanostructure dimensions on the order of 50–150 nm. The palladium nanoparticles and nanowires electrochemically deposited onto a glassy carbon surface behave differently with respect to the pH of the electrolyte buffer solution. In acid or mild acid solutions under applied negative potential, hydrogen can be adsorbed/absorbed onto/into the palladium lattice. By controlling the applied negative potential, different quantities of hydrogen can be incorporated, and this process was followed, analysing the oxidation peak of hydrogen. It is also shown that the growth of the Pd oxide layer begins at negative potentials with the formation of a pre-monolayer oxide film, at a potential well before the hydrogen evolution region. At positive potentials, Pd(0) nanoparticles undergo oxidation, and the formation of a mixed oxide layer was observed, which can act as nucleation points for Pd metal growth, increasing the metal electrode surface coverage. Depending on thickness and composition, this oxide layer can be reversibly reduced. AFM images confirmed that the PdO and PdO₂ oxides formed on the surface may act as nucleation points for Pd metal growth, increasing the metal electrode surface coverage. Dedicated to Professor Dr. Algirdas Vaskelis on the occasion of his 70th birthday.     

Recycled polypropylene with improved thermal stability and melt processability

Journal of Thermal Analysis and Calorimetry - Polypropylene (PP) is a versatile polymer, with a wide range of applications, from household appliances to packaging and automotive components....     

Optimised in vivo visualisation of cortical structures in the human brain at 3 T using IR-TSE

The primary visual cortex in humans can be identified using magnetic resonance imaging (MRI) in vivo by detection of the stria of Gennari. To fully characterize this area, high spatial resolution is essential, including the use of very thin image slices to avoid loss of definition due to partial volume effects. A three-dimensional magnetization-prepared turbo spin-echo sequence, with appropriate parameter optimization, provided high-resolution imaging (0.4 x 0.4 x 0.5 mm3) on a clinical 3-T scanner with adequate contrast to noise ratio. These images allowed visualisation of the stria of Gennari in every slice of a volume covering most of the occipital cortex, in each of six healthy volunteers. The effective longitudinal relaxation time was measured with the isotropic resolution turbo spin echo sequence and found to be substantially shorter than values measured with a dedicated relaxometric sequence. The shortening was attributed to magnetization transfer effects, as supported by the investigation of its slab and turbo-factor dependence.     

Bioelectrochemistry for sensing amino acids,peptides, proteins and DNA interactions

Oxidative damage to peptides, proteins and DNA is considered to be one of the major causes of cancer and age-related diseases. The interaction of biomolecules, peptides, proteins, nucleic acids and pharmaceuticals with solid electrode surfaces is not only a fundamental phenomenon but also a key to important and novel analytical sensing applications in biosensors, biotechnology, medical devices and drug-delivery schemes. Electrochemical methods can provide insight into the redox mechanisms and the electron-transfer reactions of a variety of fundamental biological processes.     

A novel partial silicon on insulator high voltage LDMOS with low-k dielectric buried layer

A novel partial silicon-on-insulator (PSOI) high voltage device with a low-k (relative permittivity) dielectric buried layer (LK PSOI) and its breakdown mechanism are presented and investigated by MEDICI.At a low k value the electric field strength in the dielectric buried layer (E I) is enhanced and a Si window makes the substrate share the vertical drop,resulting in a high vertical breakdown voltage;in the lateral direction,a high electric field peak is introduced at the Si window,which modulates the electric field distribution in the SOI layer;consequently,a high breakdown voltage (BV) is obtained.The values of EI and BV of LK PSOI with kI=2 on a 2 μm thick SOI layer over 1 μm thick buried layer are enhanced by 74% and 19%,respectively,compared with those of the conventional PSOI.Furthermore,the Si window also alleviates the self-heating effect.     

Thermal stability and biodegradation of novel D-mannose based glycopolymers

This paper presents the thermal stability and biodegradability testing of new glycopolymers obtained by copolymerization of a novel D-mannose based oligomer with 2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate. The thermal analysis of these glycopolymers was investigated by thermogravimetry and the glass transition temperature was determined by DSC. While the acrylate derived glycopolymer has values of the glass transition temperature below 0 °C, the methacrylate derivative has positive values, above 50 °C. The biodegradation studies of the glycopolymers were carried out in a liquid medium, using pure cultures of two microorganisms, Zymomonasmobilis and Trichodermareesei. The weight losses of the new plastic materials were significant (almost 40%) and the best results were assessed for the 2-hydroxypropyl acrylate glycopolymer in the presence of both Z. mobilis and T. reesei. Microscopy showed that both microorganisms were present on the surface of the new glycopolymers and developed small colonies while modifying their surface. The changes inside the morphology of the polymeric materials structure were drastic and were studied via SEM analysis.     

Laser induced breakdown spectroscopy surface analysis correlated with the process of nanoparticle production by laser ablation in liquids

Linkage isomerism is the coexistence of iso-compositional molecules or solids differing by connectivity of the metal to a ligand. In a crystalline solid state, the rotation is possible for asymmetric ligands, e.g., for cyanide ligand. Here we report on our observation of a phase transition in anhydrous RbMn[Fe(CN)₆] (nearly stoichiometric) and on the effect of linkage isomerism ensuing our interpretation of the results of Mössbauer study in which we observe the iron spin state crossover among two phases involved into this transition. The anhydrous RbMn[Fe(CN)₆] can be prepared via prolonged thermal treatment (1 week at at 80 °C) of the as-synthesized hydrated RbMn[Fe(CN)₆]·H₂O. The latter compound famous for its charge-transfer phase transition is a precursor in our case. As the temperature is raising above 80 °C (remaining below 100 °C) we observe RbMn[Fe(CN)₆] that inherited its F-43 m symmetry from RbMn[Fe(CN)₆]·H₂O transforming to a phase of the Fm-3 m symmetry. In the latter, more than half of Fe^3?+? ions are in high-spin state. We suggest a plausible way to explain the spin-crossover that is to allow the linkage isomerism by rotation of the cyanide ligands.