Mechanism of activation of H2O2 by peroxidases: kinetic studies on a model system

AbstractKinetic studies on the peroxidase activity of microperoxidase-8 at pH 5.5–8.5 show that the rate is increased by raising the pH or by the presence of guanidinium ion. Comparison with published data on the peroxidases provides evidence that the enzyme activates H2O2 through the cooperative binding of H+ + HO−2 and suggests a role for the invariant distal Arg

Definition of the Pnictogen Bond: A Perspective

This article proposes a definition for the term pnictogen bond and lists its donors, acceptors, and characteristic features. These may be invoked to identify this specific subset of the inter- and intra-molecular interactions formed by elements of Group 15 which possess an electrophilic site in a molecular entity.Comment: 15 page

Unravelling the effect of strand orientation on exciton migration in conjugated polymers

The study of the average distance that singlet excitons travel during their lifetime in conjugated polymers has attracted considerable attention during the past decade, because of its importance in the functioning of many polymer-based optoelectronic devices, like solar cells and photodetectors. Intriguingly, different values of exciton diffusion length have been extracted from experiments on seemingly identical conjugated polymers. Here we use computer simulations to show that the observed discrepancies in the reported values of the exciton diffusion length may arise from differences in the orientation of conjugated polymer strands relative to the substrate surface, a factor which has been mostly overlooked. Our results show that, on pristine polymer nanodomains with conjugated strands perpendicular to the substrate surface, exciton migration length is approximately 30% and 40% lower than on those with parallel and random strand orientation relative to that surface, respectively, resulting from the different contents of physical traps present in nanodomains with different strand orientation. This work underlines the importance of molecular arrangement on exciton migration, and provides a novel theoretical framework for estimating the dependence of the exciton diffusion length with the orientation of conjugated polymers strands within the nanodomains, as well as helping the design of more efficient polymer-based optical and optoelectronic devices, such as optical sensors, photodiodes, photovoltaic cells and white light-emitting diodes.This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2011, and under the projects CONC-REEQ/443/EEI/2005 and PEst-C-FIS/UI607/2011-2012. Two of us (H.M.G.C. and H. M. C. B.) are also indebted to FCT and POPH for financial support the post-doctoral grants SFRH/BPD/64554/2009 and SFRH/BPD/80561/2011

Influence of electrode degradation on organic solar cells functioning – a computational study

Recently, organic solar cells (OSC) have reached the efficiency of 10% becoming a reliable alternative to the conventional high cost inorganic solar cells. However, to gain a place in the competitive market of solar cells it is necessary to improve their lifetime. Due to the nature of the materials used, there are several degradation mechanisms [1] that lead to a decrease on device efficiency and thus to its failure, being of upmost importance to understand how they affect organic solar cells functioning. One of these mechanisms consists on electrodes degradation when in contact with air or water, leading to a change on electrode work function and thus of the energy levels at electrode/organic layer interface. As a result, the decrease on OSC efficiency has been attributed to a loss on the electrode´s ability in collecting charges from the active layer [2, 3]. However, it is unclear how a change on electrode’s work function affects the main optoelectronic mechanisms that rule the device performance [4], which can give some guidelines to prevent its failure. In order to clarify this issue we performed computational experiments with our improved mesoscopic model. Our results show that changing electrodes work function affects simultaneously all optoelectronic mechanisms that rule exciton and charges dynamics, and thus the device performance.Fundação para a Ciência e a Tecnologia (FCT

Integration and embedding of vital signs sensors and other devices into textiles

The development of ubiquitous vital sign monitoring has become a very up-to-date research theme for many academics and industrial companies in the last years. With new materials and integration techniques, it is possible to implement vital sign monitoring in an economic manner, directly into textile products. This unobtrusive presence of sensors is especially important for the monitoring of children or elderly people. This paper focuses on two aspects of sensor integration: Integration of off-the-shelf electronic components, and the use of the textile material itself as sensor, or in general as an electrically active element presenting some exploratory work in the integration of electronic devices into textiles. The main objective was to reproduce and improve on previous work presented by other authors, and foster possibilities of developing garments for vital sign monitoring with immediate industrial and economic feasibility. The use of standard production techniques to produce textile-based sensors, easily integrated into garments and with mass-market potential, is one of the important motivations for this work

Theoretical study of the influence of salt doping in the functioning of OLEDs

One of the strategies to improve the efficiency of organic light emitting diodes (OLEDs) is to dope the active organic semiconducting layer with inorganic salts, leading to the development of a hybrid organic/inorganic hetero-structure. However, it is hard to know from the experiments how each one of the electronic processes underlying the functioning of OLEDs are affected by the accumulation of inorganic ions of different sign at both organic/electrode interfaces. In order to assess these effects, we performed computer simulations by using a multi-scale model that combines quantum molecular dynamics calculations at atomistic scale with Monte Carlo calculations at mesoscopic scale. We focus our attention on the main differences obtained between doped and pristine organic layers, when bipolar charge injection occurs. Our results show a significant drop on the turn-on applied electric field while maintaining rapid response to the applied field as well as a clear increase in recombination rate and recombination efficiency far from the electrodes for the doped situation, which are responsible for the dramatic improvement of doped OLED performance found in the experiments.Fundação para a Ciência e a Tecnologia (FCT) – Programa Operacional “Ciência , Tecnologia, Inovação” – CONC-REEQ/443/EEI/2005, SFRH/BD/62536/200

First-principles study of eletronic properties of radical polymers for organic battery applications

Nowadays, there is an increasing demand for suitable energy storage devices to power the electronic devices used in a society continually oriented to technology and mobility. In order to solve this problem, and allied to environmental concerns, organic radical batteries (ORB) have been considered as possible solution by the electronic industry. In these devices, the electrodes consist on a moiety of a radical polymer and a conductive additive, with well defined electrochemically properties, which gives to ORB interesting performances, like short charging times and stable voltages, with the bonus of good device processability using wet techniques, opening the possibility to build thin and flexible batteries. The suitable electrochemical properties of radical polymers for battery applications arises from the fact that they present an organic radical pendant group with a nitroxide radical which may easily undergo reversible oxidation, forming an oxoammonium cation, or reversible reduction, forming an aminoxyl anion [1] . By suitable molecular design of the pendant group it’s possible to optimize the eletrochemical properties of the radical polymer [2], and thus of the electrodes, with the perspective to built an all-ORB. In this communication we will present some of our recent results, obtained by density functional theory (DFT) calculations, in studying the effect of the molecular structure of the pendant group and polymer backbone on the electronic structure and related properties of radical polymers used in ORB. The results obtained can be used as input parameters in mesoscopic models to study the process of charge/discharge of ORB. [1] K. Oyaizu,H. Nishide. Adv. Mater., 21, 2339-2344 (2009). [2] T. Janoschka, M. D. Hager,U. S. Schubert. Adv. Mater., 24, 6397-6409 (2012).Fundação para a Ciência e a Tecnologia (FCT

In situ measurement of hydraulic conductivity of mountain soils: a case study in Serra da Estrela mountain (Central Portugal)

Understanding the role of the vadose zone is essential to accurately assess hydrogeological systems and the respective groundwater resources. The study area (Manteigas – Nave de Santo António – Torre sector, Serra da Estrela Mountain, Central Portugal) presents specific geological, morphotectonical and climatic characteristics with significant influence on the hydrogeologic regime. The vadose zone has particular features that contribute to control both the quantity and the quality of the groundwater resources. In situ hydraulic conductivity tests were carried out in A and H soil horizons, by means of the constant head permeameter (Guelph permeameter) method. The mean value of the field saturated hydraulic conductivity is high (around 6 cm/h) and is typical of coarse textured soils. Unsaturated hydraulic conductivity was estimated using the Gardner mathematical model