On the thermal and thermodynamic (In)stability of methylammonium lead halide perovskites

The interest of the scientific community on methylammonium lead halide perovskites (MAPbX3, X = Cl, Br, I) for hybrid organic-inorganic solar cells has grown exponentially since the first report in 2009. This fact is clearly justified by the very high efficiencies attainable (reaching 20% in lab scale devices) at a fraction of the cost of conventional photovoltaics. However, many problems must be solved before a market introduction of these devices can be envisaged. Perhaps the most important to be addressed is the lack of information regarding the thermal and thermodynamic stability of the materials towards decomposition, which are intrinsic properties of them and which can seriously limit or even exclude their use in real devices. In this work we present and discuss the results we obtained using non-ambient X-ray diffraction, Knudsen effusion-mass spectrometry (KEMS) and Knudsen effusion mass loss (KEML) techniques on MAPbCl3, MAPbBr3 and MAPbI3. The measurements demonstrate that all the materials decompose to the corresponding solid lead (II) halide and gaseous methylamine and hydrogen halide, and the decomposition is well detectable even at moderate temperatures (~60 °C). Our results suggest that these materials may be problematic for long term operation of solar devices

Nanostructured semiconductor materials for dye-sensitized solar cells

Since O'Regan and Grätzel's first report in 1991, dye-sensitized solar cells (DSSCs) appeared immediately as a promising low-cost photovoltaic technology. In fact, though being far less efficient than conventional silicon-based photovoltaics (being the maximum, lab scale prototype reported efficiency around 13%), the simple design of the device and the absence of the strict and expensive manufacturing processes needed for conventional photovoltaics make them attractive in small-power applications especially in low-light conditions, where they outperform their silicon counterparts. Nanomaterials are at the very heart of DSSC, as the success of its design is due to the use of nanostructures at both the anode and the cathode. In this review, we present the state of the art for both n-type and p-type semiconductors used in the photoelectrodes of DSSCs, showing the evolution of the materials during the 25 years of history of this kind of devices. In the case of p-type semiconductors, also some other energy conversion applications are touched upon. © 2017 Carmen Cavallo et al

Solid solutions of rare earth cations in mesoporous anatase beads and their performances in dye-sensitized solar cells

Solid solutions of the rare earth (RE) cations Pr3+, Nd3+, Sm3+, Gd3+, Er3+ and Yb3+ in anatase TiO2 have been synthesized as mesoporous beads in the concentration range 0.1-0.3% of metal atoms. The solid solutions were have been characterized by XRD, SEM, diffuse reflectance UV-Vis spectroscopy, BET and BJH surface analysis. All the solid solutions possess high specific surface areas, up to more than 100 m2/g. The amount of adsorbed dye in each photoanode has been determined spectrophotometrically. All the samples were tested as photoanodes in dye-sensitized solar cells (DSSCs) using N719 as dye and a nonvolatile, benzonitrile based electrolyte. All the cells were have been tested by conversion efficiency (J-V), quantum efficiency (IPCE), electrochemical impedance spectroscopy (EIS) and dark current measurements. While lighter RE cations (Pr3+, Nd3+) limit the performance of DSSCs compared to pure anatase mesoporous beads, cations from Sm3+ onwards enhance the performance of the devices. A maximum conversion efficiency of 8.7% for Er3+ at a concentration of 0.2% has been achieved. This is a remarkable efficiency value for a DSSC employing N719 dye without co-adsorbents and a nonvolatile electrolyte. For each RE cation the maximum performances are obtained for a concentration of 0.2% metal atoms. © 2015, Nature Publishing Group. All rights reserved

Procedencia del principio de irretroactividad en los crimenes internacionales

48 p.La Irretroactividad, es un principio esencial en el Derecho Penal Interno. Sin embargo, su existencia y aplicación en el ámbito internacional es discutida, principalmente, a partir de las serias violaciones del Derecho Internacional de los Derechos Humanos y del Derecho Internacional Humanitario ocurridas durante la Segunda Guerra Mundial. La óptica que adopta el Derecho Internacional Penal tiene como eje rector evitar la impunidad y sancionar a los autores de tales brutalidades. El presente trabajo pretende efectuar un análisis doctrinal acerca de la procedencia de la Irretroactividad en materia de crímenes internacionales a la luz del Derecho Internacional Penal contemporáneo. Este análisis comparará las visiones provenientes tanto del ámbito penal interno como del ámbito internacional. Al concluir, nosotros pretendemos proponer una solución acorde con la evolución actual del Derecho Internacional

Corrigendum: On the thermal and thermodynamic (in)stability of methylammonium lead halide perovskites

NO ABSTRAC

Maternal cancer and perception of child psychological adjustment: The role of mother’s anxiety, depression, and parenting stress

A mother’s cancer diagnosis may have consequences for all family members, particularly for children, since it makes a parent less physically and emotionally available, with effects on the relationship with the child and his/her development. The main aim of this study was to analyze children’s psychological adjustment in the context of maternal cancer by considering factors related to the child (i.e., age and sex), the mother (psychological adjustment), and cancer (i.e., time elapsed from the diagnosis and current oncological treatment). Self-report questionnaires investigating mothers’ parenting stress, depression, anxiety, and children’s emotional and behavioral problems were administered to 124 mothers (mean age = 44.52 years; SD = 7.22) diagnosed with cancer. A hierarchical regression analysis highlighted that time since diagnosis and mothers’ anxiety and parenting stress accounted for almost 44% of the variance of the children’s difficulties. Maternal depression, current oncological treatment, and the child’s age and sex were not statistically significant. Higher mothers’ parenting stress and anxiety and a longer time elapsed since the first diagnosis predicted higher levels of children’s emotional and behavioral problems. These findings highlight the need to identify precursors of childhood distress in the context of maternal cancer and to develop structured programs to support both mothers and children.info:eu-repo/semantics/publishedVersio

Effect of Nitrogen Doping on the Performance of Mesoporous CMK-8 Carbon Anodes for Li-Ion Batteries

Designing carbonaceous materials with heightened attention to the structural properties such as porosity, and to the functionalization of the surface, is a growing topic in the lithium-ion batteries (LIBs) field. Using a mesoporous silica KIT-6 hard template, mesoporous carbons belonging to the OMCs (ordered mesoporous carbons) family, namely 3D cubic CMK-8 and N-CMK-8 were synthesized and thoroughly structurally characterized. XPS analysis confirmed the successful introduction of nitrogen, highlighting the nature of the different nitrogen atoms incorporated in the structure. The work aims at evaluating the electrochemical performance of N-doped ordered mesoporous carbons as an anode in LIBs, underlining the effect of the nitrogen functionalization. The N-CMK-8 electrode reveals higher reversible capacity, better cycling stability, and rate capability, as compared to the CMK-8 electrode. Coupling the 3D channel network with the functional N-doping increased the reversible capacity to similar to 1000 mAh center dot g(-1) for the N-CMK-8 from similar to 450 mAh center dot g(-1) for the undoped CMK-8 electrode. A full Li-ion cell was built using N-CMK-8 as an anode, commercial LiFePO4, a cathode, and LP30 commercial electrolyte, showing stable performance for 100 cycles. The combination of nitrogen functionalization and ordered porosity is promising for the development of high performing functional anodes

Electrochemical Behaviour of Nb-Doped Anatase TiO2 Microbeads in an Ionic Liquid Electrolyte

TiO(2)is a promising material for high-power battery and supercapacitor applications. However, in general TiO(2)suffers from an initial irreversible capacity that limits its use in different applications. A combination of a microbead morphology, Nb-doping, and the use of an ionic liquid electrolyte is shown to significantly decrease the irreversible capacity loss. A change in the electrochemical response in the first cycles indicates formation of a solid-electrolyte interphase (SEI) or a modification of the structure of the surface layer of the TiO2/Nb microbeads, which apparently stabilises the performance. The change in the response is manifested in an increased charge transfer resistance and the presence of two charge transfer contributions. During prolonged cycling the TiO2/Nb electrode shows an excellent stability over 5000 cycles. Ex situ analysis after cycling shows that the overall microbead morphology is intact and that there are no changes in the crystal structure. However, a decrease in the intensity of the XRD pattern can point to a decrease in size of the nanocrystals building up the microbeads or the formation of amorphous phases

A free-standing reduced graphene oxide aerogel as supporting electrode in a fluorine-free Li2S8 catholyte Li-S battery

We report on a novel, simple, and environmentally benign synthesis route for a free-standing reduced graphene oxide (r-GO) aerogel and its application as supporting electrode for the electrochemical redox reaction of sulphur in a catholyte-based lithium-sulphur battery. A mesoporous matrix is formed by a layers of r-GO, providing sites for electrochemical reactions and a highly conducting pathway for electrons. The highly porous structure is easily infiltrated by a catholyte solution providing a homogeneous distribution of the sulphur active material in the conductive graphene matrix and ensuring efficient electrochemical reactions. This is demonstrated by a high capacity, 3.4 mAh cm−2, at high mass loading, 3.2 mg cm−2 of sulphur in the cathode and in total the sulphur loading in the Li-S cell is even double (6.4 mg cm−2). Additionally, the presence of oxygen groups in the r-GO aerogel structure stabilizes the cycling performance and the Li-S cell with the fluorine free catholyte shows a capacity retention of 85% after 350 cycles

Nueva política europea en productos químicos. REACH

In February 2001 the European Commission issued a White Paper on a “Strategy for a future Chemicals Policy” based on a review of the current European Union system for regulating the dangerous substances and preparations. As a result, on 29 October 2003, the Commission endorsed a Proposal for a Regulation concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). This proposal creates a European Chemicals Agency and establishes the REACH system with the following elements:Registration requires industry to obtain relevant information on their substances and to use data to manage them safely.Evaluation provides confidence that industry is meeting its obligations and prevents unnecessary testing.Authorisation of substances with properties of very high concern (CMRs, PBTs, endocrine disrupters) for particular uses.Restriction as a safety net to manage risks that have not been addressed previously in the system.This system will provide information in several phases in order to know and reduce the risks derived from use of around 30,000 chemical substances that are manufactured/imported in the European Union in quantities over one ton per year. The information will be saved in a database after validation and may be used to establish a causal relationship between the environmental factors and the negative effects on health associated to the production and use of chemical products.En febrero de 2001, la Comisión Europea publicó el Libro Blanco relativo a la estrategia para la futura política en materia de sustancias y preparados químicos, que se fundamenta en una revisión del sistema comunitario actual de regulación de las sustancias y preparados químicos. Como consecuencia, el 29 de octubre de 2003, la Comisión adoptó la propuesta de Reglamento sobre registro, evaluación, autorización y restricción de las sustancias químicas (REACH). Mediante esta propuesta, además de crearse la Agencia Europea de Sustancias Químicas, se establece el sistema REACH que consta de los siguientes elementos:Registro, que exige a la industria que facilite información sobre sus sustancias con el objeto de conseguir una utilización segura de las mismas.Evaluación, que garantiza que la industria cumple sus obligaciones y evita que se realicen ensayos innecesarios.Autorización de sustancias con propiedades extremadamente preocupantes (CMR, PBT, disruptores endocrinos, etc.) para unos usos particulares.Restricción, como red de seguridad para la reducción de riesgos que no hayan sido abordados en las etapas anteriores.Este sistema de recogida de información en varias fases permitirá conocer y reducir los riesgos derivados del uso de unas 30.000 sustancias químicas que se producen/importan en la Unión Europea en cantidad superior a una tonelada/año. La información, una vez validada, se almacenará en una base de datos y podrá utilizarse para el establecimiento de un vínculo causal entre los factores medioambientales y los efectos negativos sobre la salud derivados de la producción y utilización de los productos químicos