Sharif Digital Repository

The molecular characteristics of Crocin (digentiobiosyl-8,8'-diapocarotene-8,8'-oate; C44H64O24), naturally occurring carotenoid pigment compound, such as: the ionization potential (I), electron affinity (A), electronegativity (χ), electrophicility (ω), and hardness have been calculated using Density Functional Theory (DFT) approach with B3LYP/6-31G(d,p) level of theory. The plots of Frontier Molecular Orbital and molecular electrostatic potential (MEP) for Crocin molecule along with the spin density distribution for its cation radical have been demonstrated. For the first time, we indicated the chemically active sites of the Crocin molecule by Fukui functions. Calculated components of... 

Statistical models for the study of solvent effects on the endo/exo selectivity of Diels-Alder reactions using molecular surface electrostatic potentials was obtained. The models show that hydrogen bond interactions of solvent molecules favor the predominance of the endo isomer for the reaction of methyl acrylate, methyl methacrylate and methyl trans-crotonate with cyclopentadiene whereas the effect of solvophobicity seems to be negligible. © 2003 Published by Elsevier Ltd  

Molecular surface electrostatic potential was used to predict the solvent effect on the reaction rate, endo/exo selectivity and diastereomeric excess of a Diels-Alder reaction. It is shown that these quantities can be expressed in terms of molecular surface electrostatic potentials of solvents which are obtained computationally by the HF/6-31++G* procedure. Regression analyses and an experimental database are used to obtain analytical representation of rate constant, endo/exo selectivity and diastereomeric excess. The models obtained show that the hydrogen bond donor ability of solvents on the above mentioned properties is substantial, whereas solvophobicity only affects the reaction rate... 

Solvatochromic UV-vis shifts of three probes 4-nitroaniline, 4-nitroanisol, and Reichardt's dye in binary mixtures of polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (Triton X-100 or TX-100) with methanol, ethanol, 1-propanol, and water have been investigated at 298 K. Structural and intermolecular interactions of solvatochromic probes were determined in these systems. Solvatochromic parameters, including normalized polarity (ETN), dipolarity-polarizability (π∗), hydrogen-bond donor (α), and hydrogen-bond acceptor (β) abilities, were measured at a wide range of mole fraction (0 ≤ X ≤ 1) with 0.1 increment. Interestingly, a similar behavior of ETN and α is observed in... 

An approach to access azaborininones (carbonyl-containing, boron-based heterocyclic scaffolds) using simple reagents and conditions from both organotrifluoroborates and boronic acids is described. An inexpensive, common reagent, SiO2, was found to serve as both a fluorophile and desiccant to facilitate the annulation process across three different azaborininone platforms. Computational analysis of some of the cores synthesized in this study was undertaken to compare the azaborininones with the analogous carbon-based heterocyclic systems. Computationally derived pKa values, NICS aromaticity calculations, and electrostatic potential surfaces revealed a unique isoelectronic/isostructural... 

The reverse osmosis (RO) desalination capability of hydrogenated and hydroxylated graphene nanomesh membranes (GNMs) inspired by the morphology of carbon nitride (C2N) has been studied by using molecular dynamics simulation. As an advantage, water permeance of the GNMs is found to be several orders of magnitude higher than that of the available RO filters and comparable with highly strained C2N (S-C2N) as follows: 6,6-H,OH > 12-H > S-C2N > 5,5-H,OH > 10-H. The reverse order is found for salt rejection, regardless of S-C2N. The hydrophilic character of the incorporated -OH functional group is believed to be responsible for linking the water molecules in feed and permeate sides via the... 

A series of thiophene-based donor-acceptor-donor (D-A-D) oligomer substituted metalloporphyrins (MPors) with different 3d central metal-ions (M = Co, Ni, Cu, and Zn) were systematically investigated to screen efficient hybrid photocatalysts for CO2 reduction based on density functional theory (DFT) and time-dependent DFT simulations. Compared with base MPors, the newly designed hybrid photocatalysts have a lower bandgap energy, stronger and broader absorption spectra, and enhanced intermolecular charge transfer, exciton lifetime, and light-harvesting efficiency. Then, the introduction of D-A-D electron donor (ED) groups into the meso-positions of MPors is a promising method for the... 

In this paper, the pyrrolic nitrogen functional group's presence is investigated in the selective adsorption of CO2. The grand canonical Monte Carlo (GCMC), molecular dynamics (MD), and density functional theory (DFT) were used for this study's goal. GCMC was used to calculate adsorption isotherms, selectivity, and isosteric heats. MD was used to calculate the radial distribution function (RDF) and diffusion. Reactivity parameters, electrostatic potential (ESP), reduced density gradient (RDG), and independent gradient model (IGM) were calculated using DFT. Adsorption isotherms, selectivity, and isosteric heats demonstrated that the NH group caused the selective adsorption of CO2 among CH4,... 

A novel high selective colorimetric chemosensor was introduced based on a nano diphenyl-based Schiff base (H2L), 2,2′-((1E,1′E)-(((hexylazanediyl)bis(4,1-phenylene))bis(methanylylidene))bis(azanylylidene))bis(4-methylphenol) that synthesized using sonochemical method. H2L was characterized by FT-IR, MS, TGA, 1H NMR, 13C NMR, SEM and elemental analysis techniques, then fabricated as the portable strips for sensing copper (II) ions in aqueous media. The binding interaction between H2L and various metal ions was investigated by UV–Vis spectroscopic that showed favorable coordination toward Cu2+ ion. H2L exhibited binding-induced color changes from yellow to pink and practically no interference... 

Mixing in droplets is an essential task in a variety of microfluidic systems. Inspired by electrokinetic mixing, electric field-induced hydrodynamic flow inside a charged droplet embedded in an unbounded polyelectrolyte hydrogel is investigated theoretically. In this study, the polyelectrolyte hydrogel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which is located at the plane of shear, with the electrostatic potential ζ. The fluid inside the droplet attains a finite velocity owing to hydrodynamic coupling with the... 

In this paper, a three-dimensional (3D) analytical solution of the electrostatic potential is derived for the tri-gate tunneling field-effect transistors (TG TFETs) based on the perimeter-weighted-sum approach. The model is derived by separating the device into a symmetric and an asymmetric double-gate (DG) TFETs and then solving the 2D Poisson’s equation for these structures. The subthreshold tunneling current expression is extracted by numerical integrating the band-to-band tunneling generation rate over the volume of the device. It is shown that the potential distributions, the electric field profile, and the tunneling current predicted by the analytical model are in close agreement with... 

Characterization of droplet-hydrogel interfaces is of crucial importance to engineer droplet-hydrogel composites for a variety of applications. In order to develop electrokinetic diagnostic tools for probing droplet-hydrogel interfaces, the displacement of a charged droplet embedded in a polyelectrolyte hydrogel exposed to an oscillating electric field is determined theoretically. The polyelectrolyte hydrogel is modeled as an incompressible, charged, porous, and elastic solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no charges within the droplet. The droplet-hydrogel interface is modeled as a surface with the thickness of zero... 

Organic-inorganic lead halide perovskites have emerged as very promising semiconductors with efficiencies exceeding 22% making them a serious candidate for next generation solar cells. All current high performance perovskite solar cells (PSCs), including the most recent world records, were achieved using the so-called anti-solvent method. Here, an anti-solvent, typically chlorobenzene (CB), is used to induce rapid crystallisation of a liquid perovskite precursor resulting in highly homogenous, pinhole-free planar perovskite films. While this has yielded very impressive high-performance results, few efforts have been dedicated to the fundamental understanding of the anti-solvent method. In... 

The formation of liquid bridge is pertinent to many fields including seepage into underground fractured rocks as an environmental issue and capillary continuity between matrix blocks which controls oil recovery in fractured reservoirs. Evaporation from the surface of liquid bridge into the surrounding gas could affect the stability of liquid bridge and fracture capillary pressure, which is not well discussed in the available literatures. In this research, by the aid of analogy between the diffusive flux and electrostatic potential, a new model for predicting evaporation rate from a liquid bridge inside a horizontal fracture is presented. The proposed model is then coupled with Young-Laplace... 

Determination of effective transport properties of droplet-hydrogel composites is essential for various applications. The transport of ions through a droplet-hydrogel composite subjected to an electric field is theoretically studied as an initial step toward quantifying the effective transport properties of droplet-hydrogel composites. A three-phase electrokinetic model is used to derive the microscale characteristics of the polyelectrolyte hydrogel, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which encloses the interior fluid. The surface has the thickness of zero and the electrostatic potential ζ. Standard... 

Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generated from other methods such as periodic plasma wave field, spheroidal cavity regime and plasma channel guided acceleration. Trajectory of electron motion is described as hyperbolic, parabolic or elliptic paths. We find that the self-generated electron bunch has a smaller energy width and more effective gain in energy spectrum. Initial condition for the ellipsoidal cavity is determined by laser-plasma parameters. The electron trajectory is influenced by its position, energy and... 

La-MOF-NH2@Fe3O4 (magnetic-MOF) was used as an efficient, ultrafast, and selective adsorbent for the separation of Congo Red (CR) with 92.02% removal after 2 min. The magnetic-MOF was identified by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area, Zeta Potential analysis, analysis of the magnetic hysteresis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). Kinetics, isotherms, the effect of pH, thermodynamic, and selectivity of CR adsorption were investigated. The results confirmed that the adsorption kinetics complied with the pseudo-second-order model. The...