Rational design and first-principles studies toward the remote substituent effects on a novel tetracyclic proton sponge

According to reliable density functional theory (DFT) calculations, 11,12-dimethyl-11,12-diazatetracyclo[6.2.1.1(3,6).0(2,7)]dodecane derivatives have been predicted as superorganic bases in the gas phase, acetonitrile, and the aqueous phase. The basicities of these tetracyclic proton sponges were modulated through remote substituent effects. Barriers for proton transfer between the N atoms of the diamine cations are also reported.     

Polynomial wavelets on the unit circle

In this paper, we have considered polynomial wavelets on unit circle. The scaling functions are considered to be the fundamental polynomials of the Lagrange interpolants on the equally spaced nodes different from the n roots of unity, which satisfy certain interpolatory conditions.     

Electrochemical Cholesterol Sensor Based on Tin Oxide‐Chitosan Nanobiocomposite Film

A chitosan (CS)‐tin oxide (SnO₂) nanobiocomposite film has been deposited onto an indium‐tin‐oxide glass plate to immobilize cholesterol oxidase (ChOx) for cholesterol detection. The value of the Michaelis–Menten constant (K_m) obtained as 3.8 mM for ChOx/CS‐SnO₂/ITO is lower (8 mM) than that of a ChOx/CS/ITO bioelectrode revealing enhancement in affinity and/or activity of ChOx towards cholesterol and also revealing strong binding of ChOx onto CS‐SnO₂/ITO electrode. This ChOx/CS‐SnO₂/ITO cholesterol sensor retains 95% of enzyme activity after 4–6 weeks at 4 °C with response time of 5 s, sensitivity of 34.7 μA/mg dL^?1 cm² and detection limit of 5 mg/dL.     

MoO3-TiO2纳米晶体复合材料光降解糖蜜（英文）

A MoO3-TiO2 nanocrystalline composite material was prepared by a simple solgel method.The synthesized material was charac-terized by X-ray diffraction,scanning electron microscopy with an electron dispersion spectroscopy,transmission electron microscopy,and Fourier transform infrared spectroscopy.Melanoidin is a dark brown pigment found in wastewater from the sugar industry and it pollutes water.This polluted water is generally referred to as molasses and it undergoes fermentation and is solely responsible for water,soil,and air pollution.The synthesized catalytic material was found to be effective in degrading molasses under UV-visible radiation.Analysis of treated and untreated molasses was carried out by measuring its color,chemical oxygen demand,biological oxygen demand,pH,and total dissolved solid.Results from these analyses indicate the effective photodegradation of the molasses.This methodology has several advantages such as high photocatalytic activity,non-toxicity,cleanliness,and reusability of the catalytic material.     

A Helical Cauchy-Born Rule for Special Cosserat Rod Modeling of Nano and Continuum Rods

We present a novel scheme to derive nonlinearly elastic constitutive laws for special Cosserat rod modeling of nano and continuum rods. We first construct a 6-parameter (corresponding to the six strains in the theory of special Cosserat rods) family of helical rod configurations subjected to uniform strain along their arc-length. The uniformity in strain then enables us to deduce the constitutive laws by just solving the warping of the helical rod’s cross-section (smallest repeating cell for nanorods) but under certain constraints. The constraints are shown to be critical in the absence of which, the 6-parameter family reduces to a well known 2-parameter family of uniform helical equilibria. An explicit formula for the 6-parameter helical map is derived which maps atoms in the repeating cell of a nanorod to their images for the purpose of repeating cell energy minimization. A scheme for the passage from nano to continuum scale is also presented to derive the constitutive laws of a continuum rod via atomistic calculations of nanorods. The bending, twisting, stretching and shearing stiffnesses of diamond nanorods and carbon nanotubes are computed to demonstrate our theory. We show that our scheme is more general and accurate than existing schemes allowing us to deduce shearing stiffness and several coupling stiffnesses of a nanorod for the first time.     

Effect of Material Nonlinearity on Spatial Buckling of Nanorods and Nanotubes

We show the importance of incorporating material nonlinearity for accurate determination of spatial buckling of nanorods and nanotubes. Both the nanorods and nanotubes are modeled as a special Cosserat rod whose nonlinear material laws are obtained using the recently proposed helical Cauchy-Born rule. We first present Euler buckling of solid diamond nanorods whose normalized buckling load, obtained from fully atomistic calculations, exhibits an interesting trend. The buckling load starts from unity at large aspect ratio of the nanorod, then as the aspect ratio is decreased, the buckling load increases slowly and finally decreases rapidly. We attribute this trend to material nonlinearity of the nanorod’s core at large compressive strain. We also discuss how surface stress affects buckling in nanorods. We then present the effect of compression and twist on buckling of single-walled carbon nanotubes. Interestingly, for highly twisted nanotubes, fully atomistic calculations show the first buckled mode to be different from a typical Euler buckling mode. Both the observations about nanorods and nanotubes are accurately replicated in the finite element special Cosserat rod simulation when the material nonlinearity is also incorporated. However, the simulation results exhibit completely different trend when only linear material laws are incorporated.     

Facile synthesis of isatins by direct oxidation of indoles and 3-iodoindoles using NIS/IBX

A facile one-pot access to a broad range of isatins by direct oxidation of indoles using NIS/IBX reagent in DMSO at 25?°C in very good isolated yields is reported. It is shown by mechanistic investigations that a number of substituted indoles react rapidly with NIS in DMSO to produce intermediary 3-iodoindoles, which undergo oxidation subsequently to isatins with IBX.     

Computational Mechanistic Insights on Homogeneous Water Oxidation Versus Catalyst Deactivation: A Case Study with Mononuclear Nickel and Copper Complexes

Water splitting is a potential pathway for hydrogen gas evolution and thereby realization of a carbon-neutral sustainable energy scheme. However, oxidation of water to dioxygen is the major impediment in conversion of solar energy to fuel. Herein, density functional studies are conducted to explore the reactivity conduits of two molecular electro-catalysts consisting of nickel and copper tetra-anionic tetradentate amide ligand complexes of the type [(L1)M^II]²⁻, where L1=o-phenylenebis(oxamidate), and their substitutionally modified analogues. While nickel complexes demonstrate complex borderline chemistry between homogeneous and heterogeneous pathways, showing competition between water oxidation and molecular species degradation, copper complexes display robust and efficient molecular water oxidation behavior. Our analysis predict that this disparity is primarily due to the reversible O−O bond formation in nickel complexes, which provide the platform necessary for a direct attack of OH⁻/H⁺ on the metal and terminally accessible amidate groups of the 2e⁻ oxidized anionic intermediate, [(L1⋅)Ni^III(OH)]¹⁻, respectively. This intermediate streamline ligand deactivation with a comparatively higher driving force for nickel complexes in acidic medium. Contrarily, the copper complexes display radical character on the hydroxyl ligand in the corresponding intermediate, [(L1⋅)Cu^II(OH⋅)]¹⁻, that expedite O−O interaction, leading to predominant homogeneous water oxidation under all conditions.     

Superhydrophobic and low light reflectivity silicon surfaces fabricated by hierarchical etching

Silicon is employed in a variety of electronic and optical devices such as integrated circuits, photovoltaics, sensors, and detectors. In this paper, Au-assisted etching of silicon has been used to prepare superhydrophobic surfaces that may add unique properties to such devices. Surfaces were characterized by contact angle and contact angle hysteresis. Superhydrophobic surfaces with reduced hysteresis were prepared by Au-assisted etching of pyramid-structured silicon surfaces to generate hierarchical surfaces. Consideration of the Laplace pressure on hydrophobized hierarchical surfaces gives insight into the manner by which contact is established at the liquid/composite surface interface. Light reflectivity from the etched surfaces was also investigated to assess application of these structures to photovoltaic devices.