Electrochemically deposited polyethyleneimine films and their characterization

Polyethyleneimine films have been deposited on platinum electrode surfaces by electrochemical oxidation of ethylenediamine H₂N–CH₂–CH₂–NH₂ (EDA) in acetonitrile solutions. This electrochemical synthesis was realized by cyclic voltammetry and gravimetry techniques. Then, the characterization of the thin solid polyethyleneimine film was performed using X-ray photoelectron spectroscopy and infrared spectroscopy. It was also shown, using atomic force microscopy, that the solid polymeric coating has a granular and homogeneous structure. The influence of EDA concentration on the electropolymerization process was studied leading to the conclusion that the reaction is easier for high EDA concentration. Then, the influence of the nature and concentration of the supporting salt was investigated, showing that its nature is not very important, contrary to its concentration.     

Towards the integration of dark- and photo-fermentative waste treatment. 3. Potato as substrate for sequential dark fermentation and light-driven H2 production

The goal of the study was to characterize H₂ production in an integrated process utilizing potato homogenate (PH) for dark, fermentative H₂ production followed by H₂ photoproduction using purple non-sulfur bacteria. Emphasis was placed on (a) examining potato fermentation effluent (FE) as substrate for H₂ photoproduction, (b) estimating the yield and efficiency of both processes, and (c) elucidating the physiological factors influencing the integrated system as a whole. In the dark stage maximal production of gas (11.5 L L⁻¹ of the culture) and VFA (350 mM) were observed with a PH concentration of 400 g L⁻¹ of medium, but higher yields (0.05 L g⁻¹ PH; 1.9 mmol g⁻¹ PH) were obtained at PH concentrations of 50–100 g L⁻¹. H₂ photoproduction by purple bacteria was inhibited at high FE content. Upon suitable dilution, adequate illumination, and supplementation with Fe/Mg/phosphate nutrients, H₂ photoproduction reached 40 L L⁻¹ of non-diluted FE, with a total H₂ yield of 5.6 mol mol⁻¹ glucose equivalent for the two-stage integrated process.     

Preparing Microcomposite Powders Doped with Antimony Dioxide and Properties of Thick Films Based on Those Powders

The goal of the work reported here was to develop a method of applying glass nanolayers of variable thickness to Sn_0.9Sb_0.1O₂ particles and to investigate how this affects the electrical properties of thick-film resistors. We prepared Sn_0.9Sb_0.1O₂ powders by calcinating coprecipitated tin and antimony hydroxides. Thin layers of aluminum, barium, and boron compounds were then precipitated from aqueous solutions onto powder particles. Nanolayers of glass in the BaO ― Al₂O₃ ― B₂O₃ system were obtained by dissolution followed by heat treatment. Resistive thick films made from such microcomposite powders have a higher resistivity than do those prepared by traditional methods and that resistivity changes little after repeated heat treatments. The thermal coefficient of electrical resistance decreases with increasing thickness of the glassy layer on the surface of the conducting particles.     

Supramolecular Nanofibers Self-Assembled from Foldamers: Structure Control through Preassembly

We used a helical polymer backbone (polyacrylamide) as a scaffold to organize perylene diimide chromophores into well-defined foldamers, which further undergo self-assembly into supramolecular tube-like arrays in aqueous media, as revealed by cryo-TEM imaging. The arrays are supramolecular polymers, whose structure is templated by folded primary building blocks, representing a useful tool for directing self-assembly . Exciton migration in the supramolecular arrays was studied by transient absorption and revealed a moderate exciton diffusion propensity.     

Non‐ionic Dendronized Multiamphiphilic Polymers as Nanocarriers for Biomedical Applications

A new class of non‐ionic dendronized multiamphiphilic polymers is prepared from a biodegradable (AB)_n‐type diblock polymer synthesized from 2‐azido‐1,3‐propanediol (azido glycerol) and polyethylene glycol (PEG)‐600 diethylester using Novozym‐435 (Candida antarctica lipase) as a biocatalyst, following a well‐established biocatalytic route. These polymers are functionalized with dendritic polyglycerols (G1 and G2) and octadecyl chains in different functionalization levels via click chemistry to generate dendronized multiamphiphilic polymers. Surface tension measurements and dynamic light scattering studies reveal that all of the multiamphiphilic polymers spontaneously self‐assemble in aqueous solution. Cryogenic transmission electron microscopy further proves the formation of multiamphiphiles towards monodisperse spherical micelles of about 7–9 nm in diameter. The evidence from UV–vis and fluorescence spectroscopy suggests the effective solubilization of hydrophobic guests like pyrene and 1‐anilinonaphthalene‐8‐sulfonic acid within the hydrophobic core of the micelles. These results demonstrate the potential of these dendronized multiamphiphilic polymers for the development of prospective drug delivery systems for the solubilization of poorly water soluble drugs.     

Towards the integration of dark- and photo-fermentative waste treatment. 4. Repeated batch sequential dark- and photofermentation using starch as substrate

In this study we demonstrated the technical feasibility of a prolonged, sequential two-stage integrated process under a repeated batch mode of starch fermentation. In this durable scheme, the photobioreactor with purple bacteria in the second stage was fed directly with dark culture from the first stage without centrifugation, filtration, or sterilization (not demonstrated previously). After preliminary optimization, both the dark- and the photo-stages were performed under repeated batch modes with different process parameters. Continuous H₂ production in this system was observed at a H₂ yield of up to 1.4 and 3.9 mole mole⁻¹ hexose during the dark- and photo-stage, respectively (for a total of 5.3 mole mole⁻¹ hexose), and rates of 0.9 and 0.5 L L⁻¹ d⁻¹, respectively. Prolonged repeated batch H₂ production was maintained for up to 90 days in each stage and was rather stable under non-aseptic conditions. Potential for improvements in these results are discussed.     

A comparison of bismuth nanoforms obtained in vacuum and air by microwave heating of bismuth powder

The synthesis of bismuth nanotubes in the conditions of microwave (MW) heating is reported as a lower-cost and simple technique in comparison with the traditional methods. The nanotubes were prepared by heating the Bi powder (a) in air for 15, 30, 60, and 90 min and (b) in vacuum for 5, 10, and 15 min in a domestic MW-oven (2.45 GHz, 1300 W). The products were characterized by TEM and AFM. A mechanism of formation for bismuth nanotubes in different conditions (air and vacuum) is presented.