Two organolead halide perovskite nanocrystals, CH3NH3PbBr3 and CH3NH3PbI3, were found to efficiently sensitize TiO2 for visible-light conversion in photoelectrochemical cells. When self-assembled on mesoporous TiO2 films, the nanocrystalline perovskites exhibit strong band-gap absorptions as semiconductors. The CH3NH3PbI3-based photocell with spectral sensitivity of up to 800 nm yielded a solar energy conversion efficiency of 3.8%. The CH3NH3PbBr3-based cell showed a high photovoltage of 0.96 V with an external quantum conversion efficiency of 65%.

Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells

Highly efficient quantum-dot-sensitized solar cell is fabricated using ca. 2–3 nm sized perovskite (CH3NH3)PbI3 nanocrystal. Spin-coating of the equimolar mixture of CH3NH3I and PbI2 in γ-butyrolactone solution (perovskite precursor solution) leads to (CH3NH3)PbI3 quantum dots (QDs) on nanocrystalline TiO2 surface. By electrochemical junction with iodide/iodine based redox electrolyte, perovskite QD-sensitized 3.6 μm-thick TiO2 film shows maximum external quantum efficiency (EQE) of 78.6% at 530 nm and solar-to-electrical conversion efficiency of 6.54% at AM 1.5G 1 sun intensity (100 mW cm−2), which is by far the highest efficiency among the reported inorganic quantum dot sensitizers.

6.5% efficient perovskite quantum-dot-sensitized solar cell

Somatic cell nuclear transfer and transcription-factor-based reprogramming revert adult cells to an embryonic state, and yield pluripotent stem cells that can generate all tissues. Through different mechanisms and kinetics, these two reprogramming methods reset genomic methylation, an epigenetic modification of DNA that influences gene expression, leading us to hypothesize that the resulting pluripotent stem cells might have different properties. Here we observe that low-passage induced pluripotent stem cells (iPSCs) derived by factor-based reprogramming of adult murine tissues harbour residual DNA methylation signatures characteristic of their somatic tissue of origin, which favours their differentiation along lineages related to the donor cell, while restricting alternative cell fates. Such an 'epigenetic memory' of the donor tissue could be reset by differentiation and serial reprogramming, or by treatment of iPSCs with chromatin-modifying drugs. In contrast, the differentiation and methylation of nuclear-transfer-derived pluripotent stem cells were more similar to classical embryonic stem cells than were iPSCs. Our data indicate that nuclear transfer is more effective at establishing the ground state of pluripotency than factor-based reprogramming, which can leave an epigenetic memory of the tissue of origin that may influence efforts at directed differentiation for applications in disease modelling or treatment.

/pdf/epigenetic-memory-in-induced-pluripotent-stem-cells-f2sbtru12x.pdf

Epigenetic memory in induced pluripotent stem cells

Although known since the late 19th century, organic–inorganic perovskites have recently received extraordinary research community attention because of their unique physical properties, which make them promising candidates for application in photovoltaic (PV) and related optoelectronic devices. This review will explore beyond the current focus on three-dimensional (3-D) lead(II) halide perovskites, to highlight the great chemical flexibility and outstanding potential of the broader class of 3-D and lower dimensional organic-based perovskite family for electronic, optical, and energy-based applications as well as fundamental research. The concept of a multifunctional organic–inorganic hybrid, in which the organic and inorganic structural components provide intentional, unique, and hopefully synergistic features to the compound, represents an important contemporary target.

Organic–Inorganic Perovskites: Structural Versatility for Functional Materials Design

Multielement preconcentration of trace heavy metals in water by coprecipitation and flotation with indium hydroxide for inductively coupled plasma-atomic emission spectrometry

Microwave excitation emission spectrometry. Determination of picogram quantities of metals in metalloenzymes

In spite of the existence of powerful instrumental determination methods, most trace metal analyses performed to date have required some pretreatment of samples, not only to concentrate the desired trace metals but also to avoid the interferences provided by coexisting elements. 1 3 Ionic or nonionic surfactant molecules form selfaggregates called \"micelles\" above a certain concentration, known as the critical micelle concentration (CMC). The hydrocarbon cores of the micelles give them the unique ability to solubilize many hydrophobic compounds which are otherwise only slightly soluble or insoluble in water. Surfactants can also form aggregates on solid surfaces, which are known as \"hemimicelles\" or \"ad-micelles\" and have solubilization capacities similar to the micelles. For example, surfactant-coated hydrated iron(III) oxide4 or alumina5 have been used for removal of sparingly soluble chemicals (e.g., toluene, p-xylene, trichloroethylene and pentachlorophenol) from aqueous solutions. The literature survey, however, shows that there is no study on the use of these hemi-micelles or ad-micelles for the preconcentration of traces of metal ions. In the present work, a new type of chelate-forming sorbent has been prepared in an aqueous media, based on immobilization of dithizone on surfactant-coated alumina. The sorption and desorption properties were examined to evaluate the sorbent. Copper(II) ions are taken for an example.

Immobilization of Dithizone on Surfactant-Coated Alumina for Preconcentration of Metal Ions.

A series of solid solutions, CH3NH3Sn1−xPbxBr3 (x=0–1), having cubic perovskite structures was obtained by solid-state reactions. The 119Sn Mossbauer spectra for x 0.7, suggesting the presence of a regular SnBr6 octahedra in the perovskite CH3NH3PbBr3 matrix. The high electrical conductivity of the perovskite CsSnBr3 drastically decreased upon the replacement of the cation by CH3NH3 and the central metal by Pb. This behavior suggests that both the infinite linear chain (–Br–Sn(Pb)–Br–) and its bond length have significant importance regarding electrical conductivity.

Structural phase transition and electrical conductivity of the perovskite CH3NH3Sn1−xPbxBr3 and CsSnBr3

To 1.5g of γ-alumina particles in40ml of water was added 10ml of ammoniacal solution containing 1.5mg of dithizone and 100mg of sodium dodecyl sulfate. The solution was acidified to pH 2 to form the surfactant aggregates on the alumina surfaces, into which dithizone was trapped. Traces of copper(II) and silver(I) in water were completely collected on the dithizone-coated alumina over a wide range of pH 1-7; cadmium(II), cobalt(II), nickel(II), lead(II) and zinc(II) were simultaneously recovered at pH 3-7. The chelating sorbent functioned well even in aqueous solutions containing a large amount of matrix element. The proposed sorption method has been successfully applied to the determination of traces of copper in lead metal.

Hiroshi Kawaguchi

Papers

Multielement preconcentration of trace heavy metals in water by coprecipitation and flotation with indium hydroxide for inductively coupled plasma-atomic emission spectrometry

Microwave excitation emission spectrometry. Determination of picogram quantities of metals in metalloenzymes

Immobilization of Dithizone on Surfactant-Coated Alumina for Preconcentration of Metal Ions.

Structural phase transition and electrical conductivity of the perovskite CH3NH3Sn1−xPbxBr3 and CsSnBr3

Use of Surfactant Aggregates Formed on Alumina for the Preparation of Chelating Sorbents.