Modified graphitized carbon black as transducing material for reagentless H2O2 and enzyme sensors

Direct electron transfer between redox enzymes and electrodes is the basis for the third generation biosensors. We established direct electron transfer between quinohemoprotein alcohol dehydrogenase (PQQ-ADH) and modified carbon black (CBs) electrodes. Furthermore, for the first time, this phenomenon was observed for pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase (PQQ-GDH). Reagentless enzyme biosensors suitable for the determination of ethanol, glucose and sensors for hydrogen peroxide were designed using CB electrodes and screen-printing technique. Aiming to create an optimal transducing material for biosensors, a set of CB batches was synthesized using the matrix of Plackett-Burman experimental design. Depending on the obtained surface functional groups as well as the nano-scale carbon structures in CBs batches, the maximal direct electron transfer current of glucose and ethanol biosensors can vary from 20 to 300 nA and from 30 to 6300 nA for glucose and ethanol, respectively. Using modified CB electrodes, an electrocatalytic oxidation of H₂O₂ takes place at more negative potentials (0.1-0.4 V versus Ag/AgCl). Moreover, H₂O₂ oxidation efficiency depends on the amount and morphology of fine fraction in the modified CBs.     

Synthesis of bromocyclopropylpyridines via the Sandmeyer reaction

The reactions of 2-amino-5-cyclopropylpyridine with organic nitrites in the presence of copper(II) halides in various organic solvents were investigated. Optimal reaction conditions for the Sandmeyer reaction were developed and successfully applied to the synthesis of useful building blocks, bromo and chlorocyclopropylpyridines. Aminocyclopropylpyridines were synthesized in high yields from the corresponding aminobromopyridines under standard Suzuki coupling conditions.     

Biofuel Cell Based on Anode and Cathode Modified by Glucose Oxidase

A single compartment biofuel cell (BFC) based on an anode and a cathode powered by the same fuel glucose is reported. Glucose oxidase (GOx) from Aspergillus niger was applied as a glucose consuming biocatalyst for both anode and cathode of the BFC. The 5‐amino‐1,10‐phenanthroline modified graphite rod electrode (GRE) with cross‐linked GOx was used as the bioanode, and the GRE with co‐immobilised horseradish peroxidase and GOx was exploited as the biocathode of the BFC. The open‐circuit voltage of the designed BFC exceeded 450 mV and a maximal power density of 3.5 µW/cm² was registered at a cell voltage of 300 mV.     

Theoretical investigation of the electronic structure of a ferroelectric SbSI cluster at a phase transition

This paper presents the theoretical investigation of energy levels of valence bands (VB) and core levels (CL) of the ferroelectric SbSl single crystals in antiferroelectric and ferroelectric phases. Since the best approximation for the deep VB levels is a calculation by the Hartree-Fock method, the molecular model of a SbSI crystal was used for calculations. This model of the crystal was also used for calculations of the total density of states. It was found that the VB and CL of this ferroelectric semiconductor are sensitive to the small lattice distortion at the phase transition, and that an average of the total density of states, when all atoms participate in oscillations of all normal modes, are more similar to the experimental X-ray photoelectron spectra (XPS). The experimental splitting of CL obtained by XPS was compared with the theoretically calculated one by two different methods. The cluster model calculations showed that the splitting of the CL in SbSI might be caused by photoelectron emission from the atoms, which have different valence state, at the surface.     

Class-reconstruction of total graphs

It is shown that given any vertex-deleted total graph, every reconstruction into a total graph by the addition of a vertex yields the original total graph. The proof indicates how the reconstruction can be done.     

Aqueous sol-gel synthesis route for the preparation of YAG: Evaluation of sol-gel process by mathematical regression model

Yttrium aluminium garnet (Y₃Al₅O₁₂, YAG) polycrystalline samples have been prepared by a simple aqueous sol-gel methodology. The influence of nineteen sol-gel processing variables on the formation of YAG has been investigated. Effects of different fabrication parameters on the phase purity and morphological properties of the compounds were studied by energy-dispersive spectrometry (EDS), X-ray powder diffraction (XRD) analysis and scanning electron microscopy (SEM). The parameters of the sol-gel processing such as pH of starting solution, concentration and nature of complexing ligand, temperature and duration of gelation, powder rehomogenization during annealing, duration and temperature of the final heat treatment were found to be the most significant. For the evaluation and verification of the experimental results the Brandon's model of a multiple regression was successfully used.     

Sound reduction in samples of environmentally friendly building materials and their compositions

In order to reduce the negative effect on the environment, environmentally friendly materials are being chosen for the construction of buildings more and more frequently. The building materials that are now used more commonly are clay, straw and reeds. The sound insulation properties of these environmentally friendly materials have not yet been examined thoroughly. This paper presents most commonly used sound reduction indexes R_W that have been measured in the semi-anechoic chamber and determined during the simulation. It has been found that adobe, pressed straw and reeds (oriented parallel to the sound transmission) are suitable for low-frequency sound insulation. The material with the best sound reduction index was adobe. The sound reduction index R_W of a 200 mm thick adobe wall reached up to 43 dB.     

In-Groove Carbon Nanotubes Device for SPME of Aromatic Hydrocarbons

A new solid phase microextraction (SPME) fibre using carbon nanotubes as fibre coating incorporated into a groove of a stainless steel rod is suggested. It is mechanically stable and exhibits relatively high thermal stability (up to 280 °C). The coating showed especially good extraction efficiency for aromatic hydrocarbons. The extraction properties of the fibre to benzene, toluene, ethylbenzene and o-xylene were examined using both direct and headspace SPME modes coupled to gas chromatography-flame ionization detection. The parameters affecting the extraction efficiency (extraction temperature and time, salt addition, desorption temperature and time) were investigated and quality parameters were measured under the optimized conditions. For both headspace and direct SPME the calibration graphs were linear up to 100 mg L⁻¹ (R ² > 0.996) and detection limits ranged from 0.09 to 0.39 μg L⁻¹. The repeatabilities were 5.9–13.3%. The proposed coating was applied for aromatic hydrocarbons determination in petrol station waste waters.     

WO3 coatings for photoelectrochemical synthesis of persulfate: efficiency,stability and applicability

Journal of Solid State Electrochemistry - Light-assisted electrochemical processes have the potential to replace energy-intensive electrosynthesis technologies, especially in the area of strong...