Stabilization of Highly Efficient and Stable Phase-Pure FAPbI3 Perovskite Solar Cells by Molecularly Tailored 2D-Overlayers

As a result of their attractive optoelectronic properties, metal halide APbI₃ perovskites employing formamidinium (FA⁺) as the A cation are the focus of research. The superior chemical and thermal stability of FA⁺ cations makes α-FAPbI₃ more suitable for solar-cell applications than methylammonium lead iodide (MAPbI₃). However, its spontaneous conversion into the yellow non-perovskite phase (δ-FAPbI₃) under ambient conditions poses a serious challenge for practical applications. Herein, we report on the stabilization of the desired α-FAPbI₃ perovskite phase by protecting it with a two-dimensional (2D) IBA₂FAPb₂I₇ (IBA=iso-butylammonium overlayer, formed via stepwise annealing. The α-FAPbI₃/IBA₂FAPb₂I₇ based perovskite solar cell (PSC) reached a high power conversion efficiency (PCE) of close to 23 %. In addition, it showed excellent operational stability, retaining around 85 % of its initial efficiency under severe combined heat and light stress, that is, simultaneous exposure with maximum power tracking to full simulated sunlight at 80 °C over 500 h.     

Scheduling to minimize maximum earliness and number of tardy jobs where machine idle time is allowed

We address the bicriteria problem of minimizing the number of tardy jobs and maximum earliness on a single machine where machine idle time is allowed. We show that the problem of minimizing the number of tardy jobs while maximum earliness is kept at its minimum value of zero is polynomially solvable. We present polynomial time algorithms for the maximum earliness problem subject to no tardy jobs and the maximum earliness problem for a given set of tardy jobs. Finally, we discuss the use of the latter algorithm in generating all efficient schedules.     

Terahertz current oscillations in single-walled zigzag carbon nanotubes

We report time-dependent terahertz current oscillations on an n=10 single-walled zigzag carbon nanotube (CNT) that is 100 nm long. To obtain transport characteristics in this CNT, we developed an ensemble Monte Carlo (MC) simulator, which self-consistently calculates the electron transport and electrical potential. The ensemble MC simulations indicate that, under certain dc bias and doping conditions, the average electron velocity and concentration oscillate. This leads to current oscillations in space and time, on the tube, and at the contacts. We attribute this to accumulation and depletion of the CNT electrons at different locations on the tube, giving rise to low and high density electron regions. These local dipoles are a result of intra- and intersubband scatterings and different subband dispersion relations. This in turn forms propagating dipoles and current oscillations.     

High image-density particle image velocimetry using laser scanning techniques

Laser scanning, corresponding to time-dependent deflections of laser beam across a field of interest, can provide relatively high illumination intensity of small particles, thereby allowing implementation of high image-density particle image velocimetry (PIV). Scanning techniques employing a rotating (multi-faceted) mirror, an oscillating mirror, and an acousto-optic deflector are addressed. Issues of illumination intensity and exposure, rate of scan of the laser beam, and retrace time of the scanning beam are assessed. Representative classes of unsteady separated flows investigated with laser-scanning PIV are described.     

Lattice Boltzmann Simulation of Fluid Flow in Synthetic Fractures

Fractures play an important role in reservoir engineering as they dominate the fluid flow in the reservoir. All evidence suggests that rarely can one model flow and transport in a fractured rock consistently by treating it as a uniform or mildly nonuniform isotropic continuum. Instead, one must generally account for the highly erratic heterogeneity, directional dependence, dual or multicomponent nature and multiscale behavior of fractured rocks. As experimental methods are expensive and time consuming most of the time numerical methods are used to study flow and transport in a fractured rock. In this work, we present results of the numerical computations for single phase flow simulations through two-dimensional synthetically created fracture apertures. These synthetic rock fractures are created using different fractal dimensions, anisotropy factors, and mismatch lengths. Lattice Boltzmann method (LBM), which is a new computational approach suitable to simulate fluid flow especially in complex geometries, was then used to determine the permeability for different fractures. Regions of high velocity and low velocity flow were identified. The resulting permeability values were less than the ones obtained with the cubic law estimates. It has been found that as the mean aperture–fractal dimension ratio increased permeability increased. Moreover as the anisotropy factor increased permeability decreased. Neural network simulations were used to generalize the results.     

Oxidation of thiols to disulfides with monochloro poly(styrenehydantoin) beads

Various thiols were converted to symmetrical disulfides. This facile and reproducible method uses water as a solvent, and monochloro poly(styrenehydantoin) beads as an oxidizing agent.     

Experimental and Computational Studies on the 1:1 Complex of Anthranilic Acid with P-Toluenesulfonic Acid

Abstract

The proton-transfer compound (3) was synthesized in good yields by the reaction of anthranilic acid with p-toluenesulfonic acid. It was characterized by elemental analysis, infrared spectroscopy, and X-ray single-crystal determination. The crystal structure analysis of 2-carboxyanilinium p-toulenesulfonate (3) has revealed a one-dimensional hydrogen-bonded network structure, involving the tosylate anion, the carboxyl group, and the ammonium group. The H(N)···O distances range from 1.97 to 2.23 Å. The molecular geometry and vibrational frequencies of 3 were calculated using the ab-initio method (HF) with the 6–31G(d) and 6–31+G(d,p) basis sets. The computed results indicate that the optimized geometry reproduces the crystal structure well, and the assignments of fundamental vibrations also agree well with the theoretical frequencies. The intermolecular proton transfer process between the ionic (3) and nonionic (4) structures was also investigated with the theoretical computations. The nonionic form (4) is energetically more stable than the ionic form (3) and TS(3→4) by 9.76 and 7.01 kcal/mol, respectively, including the zero-point vibrational energy correction at the HF/6–31+G(d,p) level. In addition, the atomic charges, the molecular electrostatic potentials, the nucleus-independent chemical shifts, and the frontier molecular orbitals of 3 were carried out at the HF/6–31+G(d,p) level of theory.

Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional figures and tables     

Maximizing the Potency of siRNA Lipid Nanoparticles for Hepatic Gene Silencing In Vivo

Special (lipid) delivery: The role of the ionizable lipid pK(a) in the in?vivo delivery of siRNA by lipid nanoparticles has been studied with a large number of head group modifications to the lipids. A tight correlation between the lipid pK(a) value and silencing of the mouse FVII gene (FVII ED(50) ) was found, with an optimal pK(a) range of 6.2-6.5. The most potent cationic lipid from this study has ED(50) levels around 0.005?mg?kg(-1) in mice and less than 0.03?mg?kg(-1) in non-human primates.     

Evaluation of oil content and fatty acid composition of five endemic Bupleurum species growing in the Central Anatolia region of Turkey

The fatty acid composition of five endemic Bupleurum (Apiaceae) species was analysed by GC technique for their nutritional value. The amount of oil content of the species varied from 3.77% to 7.03%. Twenty-one fatty acids were identified in the oils. The fatty acid composition of the studied species contained oleic, palmitic and linoleic acids as the major components. Oleic acid ranged from 8.81% to 68.30%, while the levels of palmitic acid were found to be between 12.47% and 47.85%. Bupleurum lycaonicum, Bupleurum sulphureum and Bupleurum heldreichii are very good sources of oleic acid. The remaining species were characterised as containing the highest level of palmitic acid. In this study, the total saturated fatty acids ranged between 15.02 and 65.20%, while total monounsaturated fatty acids were between 18.10 and 70.65%. The total polyunsaturated fatty acid accounted for 13.47-35.20% of the studied fatty acids. Therefore, we can conclude that Bupleurum oils have a significant nutritional value.