In CH3NH3PbI3 Perovskite Film,the Surface Termination Layer Dominates the Moisture Degradation Pathway

Theoretical studies have shown that surface terminations, such as MAI or PbI layers, greatly affect the environmental stability of organic–inorganic perovskite. However, until now, there has been little effort to experimentally detect the existence of MAI or PbI terminations on MAPbI₃ grains, let alone disclose their effects on the humidity degradation pathway of perovskite solar cell. Here, we successfully modified and detected the surface terminations of MAI and PbI species on polycrystalline MAPbI₃ films. MAI-terminated perovskite film followed the moisture degradation process from MAPbI₃ to hydrate MAPbI₃⋅H₂O and then into PbI₂, with penetration of water molecules being the main driving force leading to the degradation of MAPbI₃ layer by layer. In contrast, for the PbI-terminated perovskite film in a humid atmosphere, a deprotonation degradation pathway was confirmed, in which the film preferentially degraded directly from MAPbI₃ into PbI₂, here the iodine defects played a key role in promoting the dissociation of water molecules into OH⁻ and further catalyzing the decomposition of perovskite.     

Heteropoly acid supported on activated natural clay-catalyzed synthesis of 3,4-dihydropyrimidinones/thiones through Biginelli reaction under solvent-free conditions

Dihydropyrimidinones/thiones (DHPM’s) have been prepared by one-pot condensation of methyl acetoacetate, aldehydes, urea/thiourea in the presence of heteropoly-11-tungsto-1-vanadophosphoric acid, H₄[PVW₁₁O₄₀]?·?32H₂O, (HPV) supported on activated natural clay (HPVAC) under solvent-free reaction condition have been proposed. The DHPM derivatives were identified through elemental analysis and melting point measurements and characterized by FT-IR, ¹H-NMR, ¹³C-NMR spectroscopic methods.     

Carboxyl-functionalized graphene oxide-modified electrode for the electrochemical determination of nonsteroidal anti-inflammatory drug diclofenac

Ionics - A simple and sensitive electrochemical method was proposed for the quantitative determination of nonsteroidal anti-inflammatory drug diclofenac (DCF). For the first time,...     

One-pot three-component synthesis of bis(indolyl)methanes under solvent-free condition using heteropoly-11-tungsto-1-vanadophosphoric acid supported on natural clay as catalyst

One-pot three-component condensation reaction of two moles of indole and one mole of aromatic aldehyde for the synthesis of bis(indolyl)methanes in the presence of new catalytic material, heteropoly-11-tungsto-1-vanadophosphoric acid, H₄[PV^VW₁₁O₄₀] (HPV) supported on activated natural clay under solvent-free reaction condition has been proposed. The catalysts were prepared by incipient wetness impregnation method. The physicochemical characterizations of the HPV (20%) supported on natural clay (HPVAC-20) have also been discussed. Solvent-free heterogeneous reaction condition, simple workup procedure, short reaction time, high yield of products, and reusability of the catalyst are the advantages of the protocol.     

Kinetics of the outer-sphere oxidation of thiourea by heteropoly-α<Subscript>2</Subscript>-17-tungsto-1-vanadodiphosphate anion

Kinetics of the oxidation of thiourea (tu) by heteropoly-α₂-17-tungsto-1-vanadodiphosphate anion, α₂-[P₂V^VW₁₇O₆₂]^7?, have been studied spectrophotometrically in aqueous acidic medium at 25 °C. At low pH (2.4–3.0), the neutral form of tu is the only reactive species. At higher pH (4.2–4.9), both neutral and deprotonated forms of tu participate in the reaction. The observed mixed-order kinetics suggest two parallel reactions: one in which the order in [tu] is unity, and a second in which it is two. In both cases, the order in [α₂-[P₂V^VW₁₇O₆₂]^7?] is unity. Based on the kinetic studies, a mechanism is proposed, in which a second-order proton-coupled electron transfer involving NH₂CSNH₂ and α₂-[P₂V^VW₁₇O₆₂]^7? proceeds through a sequential electron transfer, followed by proton transfer such that the reaction is an “activation-controlled” outer-sphere electron transfer process. By applying the Marcus equation, the self-exchange rate constants for the couples \({\text{NH}}_{2} {\text{CSNH}}_{2}^{ \cdot + }\)/NH₂CSNH₂ and α₂-[P₂V^VW₁₇O₆₂]^7?/α₂-[P₂V^IVW₁₇O₆₂]^8? were evaluated.     

Synthesis and Characterization of Lewis Base Stabilized Gallium–Tellurium Complexes

Abstract

Complexes of gallium bound to chalcogen elements recently have found importance in synthesis and as single molecular precursors for preparing thin films of gallium chalcogenides for their applications as photo-receivers for visible and near IR region. Herein we report the synthesis and characterization of some Lewis base (LB) stabilized gallium-telluride complexes. Gallium tellurolate complexes of formula, [LB] · [Ga(TePh)₃] _x , [x = 1, LB = 4-dimethylaminopyridine; x = 2, LB = 4,4′-methylene bis(N,N′-dimethylaniline] were prepared by reacting the corresponding Lewis base adduct of gallium(III) iodide and phenyllithium tellurolate. The complexes have been characterized by elemental analyses, ICP-MS, multinuclear NMR, and thermal and mass spectrometry. Such complexes may be potential single-molecular precursors for III–VI electronic materials.     

Techniques for the analysis of risks in major projects

Risk management currently has an important bearing on the outcomes of major projects. It usually consists of three core areas: analysis, evaluation and control. One of the vital decisions to be made within the area of risk analysis is the choice of techniques to be used which are broadly classified under qualitative and quantitative methods. Through a questionnaire, this paper identifies the most successful risk analysis techniques within both categories. Over one hundred large companies within the construction industry, and every oil and gas operator in the UK were approached. The areas surveyed on were: risk analysis techniques employed by the companies; the relative success of the techniques; the size and range of activities of the company and the company's policy on identifying and responding to specific risks encountered during any particular project. The main conclusions are that personal and corporate experience, and engineering judgement are the most successful qualitative techniques; scenario analysis, EMV, ENPV, and break-even analysis being the principal quantitative techniques.