Anthocyanic pigments from elicited in vitro grown shoot cultures of Vaccinium corymbosum L., cv. Brigitta Blue, as photosensitizer in natural dye-sensitized solar cells (NDSSC).

We investigated the effect on anthocyanins and total phenols content and antioxidant capacity of in vitro shoot cultures of Vaccinium corymbosum L., cv. Brigitta Blue, grown on an eliciting medium supplied with 10 µM naphthalene acetic acid, in combination with reduced content of salts and organics in respect to the basal medium. After 45 days, higher content of total phenols and anthocyanins was obtained from extracts of shoots grown on the elicitation medium. Anthocyanin molecules, absent in control shoots, were identified by HPLC-MS as delphinidine-glycoside, cyanidine-glycoside, delphinidine-arabinoside, cyanidine- arabinoside and cyanidine-acetylglycoside. Chlorogenic acid, present in control shoots, was nearly absent in elicited shoots. We exploited the anthocyanin - based raw extracts of "Brigitta Blue" shoots grown on the elicitation medium as a source of natural dye photosensitizers for Dye Sensitized Solar Cells, taking into account that such raw extracts showed antioxidant properties and photostability features. A purified dye was also prepared and the comparison of the latter with the raw one has been analysed by spectrophotometric, chromatographic and power conversion efficiency determination. The power conversion efficiencies from the raw and the purified dye were not different and they were comparable to the data obtained by other authors with anthocyanin-based dyes from in vivo grown plants.

Halides inhibition of multicopper oxidases studied by FTIR spectroelectrochemistry using azide as an active infrared probe.

An infrared spectroelectrochemical study of Trametes hirsuta laccase and Magnaporthe oryzae bilirubin oxidase has been performed using azide, an inhibitor of multicopper oxidases, as an active infrared probe incorporated into the T2/T3 copper cluster of the enzymes. The redox potential-controlled measurements indicate that N3- stretching IR bands of azide ion bound to the T2/T3 cluster are only detected for the oxidized enzymes, confirming that azide only binds to Cu2+. Moreover, the process of binding/dissociation of azide ion is shown to be reversible. The interaction of halide anions, which also inhibit multicopper oxidases, with the active site of the enzymes was studied by measuring the changes in the azide FTIR bands. Enzymes inhibited by azide respond differently upon addition of fluoride or chloride ions to the sample solution inhibited by azide. Fluoride ions compete with azide for binding at one of the T2/T3 Cu ions, whereas competition from chloride ions is much less evident.

Transparent, mediator- and membrane-free enzymatic fuel cell based on nanostructured chemically modified indium tin oxide electrodes.

We detail a mediator- and membrane-free enzymatic glucose/oxygen biofuel cell based on transparent and nanostructured conducting supports. Chemically modified indium tin oxide nanoparticle modified electrodes were used to substantially increase the active surface area without significantly compromising transparency. Two different procedures for surface nanostructuring were employed, viz. spray-coating and drop-coating. The spray-coated biodevice showed superior characteristics as compared to the drop-coated enzymatic fuel cell, as a result of the higher nanostructured surface area as confirmed by electrochemical characterisation, as well as scanning electron and atomic force microscopy. Subsequent chemical modification with silanes, followed by the immobilisation of either cellobiose dehydrogenase from Corynascus thermophiles or bilirubin oxidase from Myrothecium verrucaria, were performed to obtain the bioanodes and biocathodes, respectively. The optimised biodevice exhibited an OCV of 0.67V and power output of up to 1.4µW/cm2 at an operating voltage of 0.35V. This is considered a significant step forward in the field of glucose/oxygen membrane- and mediator-free, transparent enzymatic fuel cells.

Laccase-modified gold nanorods for electrocatalytic reduction of oxygen.

cathodes. Nanostructuring was provided by gold nanorods (AuNRs), which were characterized and covalently attached to electrodes made of low-density graphite. The nanostructured electrode was the scaffold for covalent and oriented attachment of ThLc. The bioelectrocatalytic currents measured for oxygen reduction were as high as 0.5 mA/cm(2 and 0.7 mA/cm(2), which were recorded under direct and mediated electron transfer regimes, respectively. )The experimental data were fitted to mathematical models showing that when the O2 is bioelectroreduced at high rotation speed of the electrode the heterogeneous electron transfer step is the rate-liming stage. The electrochemical measurement hints a wider population of non-optimally wired laccases than previously reported for 5­8 nm size Au nanoparticle-modified electrode, which could be due to a larger size of the AuNRs when compared to the laccases as well as their different crystal facets.

The Influence of Carbonaceous Matrices and Electrocatalytic MnO2 Nanopowders on Lithium-Air Battery Performances.

Here, we report new gas diffusion electrodes (GDEs) prepared by mixing two different pore size carbonaceous matrices and pure and silver-doped manganese dioxide nanopowders, used as electrode supports and electrocatalytic materials, respectively. MnO2 nanoparticles are finely characterized in terms of structural (X-ray powder diffraction (XRPD), energy dispersive X-ray (EDX)), morphological (SEM, high-angle annular dark field (HAADF)-scanning transmission electron microscopy (STEM)/TEM), surface (Brunauer Emmet Teller (BET)-Barrett Joyner Halenda (BJH) method) and electrochemical properties. Two mesoporous carbons, showing diverse surface areas and pore volume distributions, have been employed. The GDE performances are evaluated by chronopotentiometric measurements to highlight the effects induced by the adopted materials. The best combination, hollow core mesoporous shell carbon (HCMSC) with 1.0% Ag-doped hydrothermal MnO2 (M_hydro_1.0%Ag) allows reaching very high specific capacity close to 1400 mAh·g-1. Considerably high charge retention through cycles is also observed, due to the presence of silver as a dopant for the electrocatalytic MnO2 nanoparticles.