High-Efficiency Perovskite Solar Cells Enabled by Anatase TiO2 Nanopyramid Arrays with an Oriented Electric Field

One-dimensional (1D) nanostructured oxides are proposed as excellent electron transport materials (ETMs) for perovskite solar cells (PSCs); however, experimental evidence is lacking. A facile hydrothermal approach was employed to grow highly oriented anatase TiO₂ nanopyramid arrays and demonstrate their application in PSCs. The oriented TiO₂ nanopyramid arrays afford sufficient contact area for electron extraction and increase light transmission. Moreover, the nanopyramid array/perovskite system exhibits an oriented electric field that can increase charge separation and accelerate charge transport, thereby suppressing charge recombination. The anatase TiO₂ nanopyramid array-based PSCs deliver a champion power conversion efficiency of approximately 22.5 %, which is the highest power conversion efficiency reported to date for PSCs consisting of 1D ETMs. This work demonstrates that the rational design of 1D ETMs can achieve PSCs that perform as well as typical mesoscopic and planar PSCs.     

Numerical solution of functional integral equations by the variational iteration method

In the present article, we apply the variational iteration method to obtain the numerical solution of the functional integral equations. This method does not need to be dependent on linearization, weak nonlinearity assumptions or perturbation theory. Application of this method in finding the approximate solution of some examples confirms its validity. The results seem to show that the method is very effective and convenient for solving such equations.     

Influence of acidic ionic liquids as an electrolyte additive on the electrochemical and corrosion behaviors of lead-acid battery

The aim of this study is to introduce the application of some acidic ionic liquids (ILs) as an electrolyte additive in lead-acid batteries. A family of alkylammonium hydrogen sulfate ILs, which are different in the number of alkyl chain, is investigated with the aim to compare their effects on the electrochemical behavior of Pb–Sb–Sn alloy in sulfuric acid solution. The hydrogen and oxygen gas evolution potential and anodic layer characteristics were investigated employing cyclic and linear sweep voltammetric methods. The morphological changes of the PbSO₄ layer that formed on the electrode surface were confirmed using scanning electron microscopy. Also, potentiodynamic polarization curves, electrochemical impedance spectroscopy, and an equivalent circuit analysis were used to evaluate the corrosion behaviors of the Pb–Sb–Sn alloy in the presence of ILs. The obtained results indicate that hydrogen and oxygen evolution overpotential of lead–antimony–tin alloy increases in the solution containing IL and mainly depends on the number of alkyl chain in alkylammonium cation. It is clearly observed that the morphology of PbSO₄ layer changes under the influence of ILs. The corrosion studies show an increase in corrosion resistance of lead alloy in the presence of some ILs. Also, the electrochemical effects of ILs in conversion of PbSO₄ to PbO₂ and vice versa were investigated by carbon-PbO paste electrode. Cyclic voltammogram of carbon-PbO electrode shows that in the presence of ILs, oxidation and reduction peak currents increase, while reversibility decreases.     

Mammalian DNA δ15N exhibits 40‰ intramolecular variation and is unresponsive to dietary protein level

We report the first high‐precision characterization of molecular and intramolecular δ¹⁵N of nucleosides derived from mammalian DNA. The influence of dietary protein level on brain amino acids and deoxyribonucleosides was determined to investigate whether high protein turnover would alter amino acid ¹⁵ N or ¹³ C values. Pregnant guinea pig dams were fed control diets, or high or low levels of dietary protein throughout gestation, and all pups were fed control diets. The cerebellar DNA of offspring was extracted at 2 and 120 days of life, nucleosides isolated and δ¹⁵N and δ¹³C values characterized. Mean diet δ¹⁵N was 0.45 ± 0.33‰, compared with cerebellar whole tissue and DNA δ¹⁵N = +4.1 ± 0.7‰ and ?4.5 ± 0.4‰, respectively. Cerebellar deoxythymidine (dT), deoxycytidine (dC), deoxyadenosine (dA), and deoxyguanosine (dG) δ¹⁵N were +1.4 ± 0.4, –2.1 ± 0.9, –7.2 ± 0.3, and ?10.4 ± 0.5‰, respectively. There were no changes in amino acid or deoxyribonucleoside δ¹⁵N values due to dietary protein level. Using known metabolic relationships, we developed equations to calculate the intramolecular δ¹⁵N values originating from aspartate (asp) in purines (pur) or pyrimidines (pyr), glutamine (glu), and glycine (gly) to be δ¹⁵N_ASP‐PUR, δ¹⁵N_ASP‐PYR, δ¹⁵N_GLN, and δ¹⁵N_GLY +11.9 ± 2.3‰, +7.0 ± 2.0‰, –9.1 ± 2.4‰, and ?31.8 ± 8.9‰, respectively. A subset of twelve amino acids from food and brain had mean δ¹⁵N values of 4.3 ± 3.2‰ and 13.8 ± 3.1‰, respectively, and δ¹⁵N values for gly and asp were 12.6 ± 2.2‰ and 15.2 ± 0.8‰, respectively. A separate isotope tracer study detected no significant turnover of cerebellar DNA in the first six months of life. The large negative δ¹⁵N difference between gly and cerebellar purine N at the gly (7) position implies either that there is a major isotope effect during DNA synthesis, or that in utero gly has a different isotope ratio during rapid growth and metabolism from that in adult life. Our data show that cerebellar nucleoside intramolecular δ¹⁵N values vary over more than 40‰ and are not influenced by dietary protein level or age. Copyright © 2011 John Wiley & Sons, Ltd.     

A manganese oxide with phenol groups as a promising structural model for water oxidizing complex in Photosystem II: a 'golden fish'

We describe here the ability of manganese oxide monosheets to aggregate to form layered structures with 4-aminophenol molecules. These aggregated monosheets could be considered as the first step to synthesize a self-assembled layered hybrid of phenol-manganese ions with phenol and manganese(III) and (IV) as exists in the water oxidizing complex of Photosystem II.     

Electro-optical properties of zigzag and armchair boron nitride nanotubes under a transverse electric field: Tight binding calculations

The electro-optical properties of zigzag and armchair BNNTs in a uniform transverse electric field are investigated within tight binding approximation. It is found that the electric field modifies the band structure and splits band degeneracy where these effects reflect in the DOS and JDOS spectra. A decrease in the band gap, as a function of the electric field, is observed. This gap reduction increases with the diameter and it is independent of chirality. An analytic function to estimate the electric field needed for band gap closing is proposed which is in good agreement with DFT results. In additional, we show that the larger diameter tubes are more sensitive than small ones. Number and position of peaks in DOS and JDOS spectra for armchair and zigzag tubes with similar radius are dependent on electric field strength.     

Green and convenient protocols for the efficient reduction of nitriles and nitro compounds to corresponding amines with NaBH4 in water catalyzed by magnetically retrievable CuFe2O4 nanoparticles

Research on Chemical Intermediates - In this study, firstly, CuFe2O4 nanoparticles were prepared by a simple operation. The structure of the mentioned nanoparticles was characterized by Fourier...     

A Green Protocol for Solvent-Free Conversion of Epoxides to Thiiranes with Dowex-50WX8–Supported Thiourea

Structurally different epoxides were efficiently converted to the corresponding thiiranes by Dowex-50WX8–supported thiourea under solvent-free conditions. The reactions were carried out either in an oil bath or under microwave irradiation to give the thiiranes in 75–98% yields within 30 sec–120 min.     

NaHSO4·H2O as a Heterogeneous Acidic Reagent for Mild and Convenient Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones and Their Sulfur Derivatives

One-pot cyclocondensation reaction of aromatic aldehydes, 1,3-dicarbonyl compounds and urea/thiourea in the presence of NaHSO₄·H₂O produced 4-aryl substituted 3,4-dihydropyrimidin-2(1H)-ones and their sulfur analogs in high to excellent yields. The reactions were carried out in refluxing n-hexane and were completed within 2.5–11 h.     

Nitric acid in the presence of supported P2O5 on silica gel: an efficient and novel reagent for oxidation of sulfides to the corresponding sulfoxides

This paper describes an efficient and easy method for oxidation of sulfides 1 to their corresponding sulfoxides 2 with nitric acid in the presence of supported P₂O₅ on silica gel under solvent-free conditions in high yields.