Exploring A-Site Cation Variations in Dion-Jacobson Two-Dimensional Halide Perovskites for Enhanced Solar Cell Applications : A Density Functional Theory Study

The exceptional photophysical and electronic properties of 2D hybrid perovskites possess potential applications in the field of solar energy harvesting. The present work focuses on the two systems, exhibiting the Dion–Jacobson phase of 2D perovskite consisting of methylammonium (MA) and formamidinium (FA) cations at A-site and 3-(aminomethyl)pyridinium (3AMPY) as ring-shaped organic spacer. Altering A-site cations creates a distortion of inorganic layers and hydrogen bond interactions. It has been noted that the angles of Pb–I–Pb and I–Pb–I are more symmetric (close to 180°) for (3AMPY)(MA)Pb2I7 compared to (3AMPY)(FA)Pb2I7 and result in increase of bandgap from 1.51 to 1.58 eV. This further leads to a significant difference in Rashba splitting energy under the influence of spin-orbit coupling effects, where the highest splitting (36 meV) is calculated for conduction band edge of the (3AMPY)(FA)Pb2I7, suggesting the promising applications toward spintronics. The calculated absorption spectra cover the range from 300 to 450 nm, indicating significant optical activity of 2D (3AMPY)(MA)Pb2I7 and (3AMPY)(FA)Pb2I7 in the visible and ultraviolet regions, which bodes well for their application in advanced optoelectronic devices. The bandgap and high absorption coefficients present more than 30% of theoretical power conversion efficiency for both systems, as calculated from the spectroscopic-limited maximum efficiency

Spectral and DFT studies of anion bound organic receptors: Time dependent studies and logic gate applications

New colorimetric receptors R1 and R2 with varied positional substitution of a cyano and nitro signaling unit having a hydroxy functionality as the hydrogen bond donor site have been designed, synthesized and characterized by FTIR, 1H NMR spectroscopy and mass spectrometry. The receptors R1 and R2 exhibit prominent visual response for F− and AcO– ions allowing the real time analysis of these ions in aqueous media. The formation of the receptor–anion complexes has been supported by UV–vis titration studies and confirmed through binding constant calculations. The anion binding process follows a first order rate equation and the calculated rate constants reveal a higher order of reactivity for AcO− ions. The 1H NMR titration and TDDFT studies provide full support of the binding mechanism. The Hg2+ and F− ion sensing property of receptor R1 has been utilized to arrive at “AND” and “INHIBIT” molecular logic gate applications

Static and Dynamical Properties of heavy actinide Monopnictides of Lutetium

In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal structure. The spin orbit coupling and Hubbard-U corrections are included to correctly predict the essential properties of these compounds. The elastic constants, Young's modulus E, Poisson's ratio v, shear modulus G, anisotropy factor A and Pugh's ratio are computed. We found that all lutetium monopnictides are anisotropic and show brittle character. From the wave velocities along [100], [110] and [111] directions, melting temperature of lutetium monopnictides are predicted. Dynamical stability of these monopnictides has been studied by density functional perturbation theory

Self-Supported Mn-Ni₃Se₂ Electrocatalysts for Water and Urea Electrolysis for Energy-Saving Hydrogen Production

Recently, there has been a huge research interest in developing robust, efficient, low-cost, and earth-abundant materials for water and urea electrolysis for hydrogen (H2) generation. Herein, we demonstrate the facile hydrothermal synthesis of self-supported Mn-Ni3Se2 on Ni foam for overall water splitting under wide pH conditions. With the optimized concentration of Mn in Ni3Se2, the overpotential for hydrogen evolution, oxygen evolution, and urea oxidation is significantly reduced by an enhanced electrochemical active surface area. Different electronic states of metal elements also produce a synergistic effect, which accelerates the rate of electrochemical reaction for water and urea electrolysis. Owing to the chemical robustness, Mn-doped Ni3Se2 shows excellent stability for long time duration, which is important for its practical applications. A two-electrode electrolyzer exhibits low cell voltages of 2.02 and 1.77 V for water and urea electrolysis, respectively, to generate a current density of 100 mA/cm2. Finally, the prepared nanostructured Mn-Ni3Se2@NF acts as an electrocatalyst for overall water splitting under wide pH conditions and urea electrolysis for energy-saving hydrogen production and wastewater treatment