Polar fractions of crude oil play an important role in the state and structure of the oil/water interface, and understanding their behavior is crucially important in oil recovery. In studying different properties of oil/water interface, there are issues to be resolved and understood on the basis of molecular structure. A synthetic oil/water system is usually used to model and to simulate molecular-based behavior of the interface involving a polar surfactant. This paper is devoted to modeling the behavior of pyridine and its alkyl derivative at the interface of synthetic oil/water by molecular dynamics simulation. Solutions of pyridine and 4-ethylpyridine in octane/water system were studied for the density distribution and the structure in bulk phases as well as their molecular orientation at the interface. The interface of the octane/water system was first studied by simulation of density profile and interfacial properties to validate the force field applied. The distribution of pyridine and 4-ethylpyridine in and at the interface was studied, and the orientation of these molecules was determined accordingly. The results of simulation indicate that pyridine dissolves in water and avoids the interface leaving no residue in the octane phase, while 4-ethylpyridine mainly occupies the interface and dissolves partly in water. The bivariat maps gives molecular orientations in terms of spherical polar angles and indicate that the pyridine ring plane takes a parallel position with respect to interfacial plane surface; the nitrogen atom in pyridine takes any direction toward water and octane equally, but in 4-ethylpyridine preferentially is oriented toward water.

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For the first time, bulk and surface properties of hexanoic acid was simulated by classical molecular dynamics and compared with corresponding values we measured in the range of T = 298.15–373.15 K at ambient pressure. AMBER and optimized potential for liquid substance all atom (OPLS-AA) force fields plus our calculations for atoms charges enable simulating density, surface tension, and viscosity, as well as the bulk structural and orientational profile of molecules at the hexanoic acid/vapor interface. The simulated densities are in good agreement within 2.9%, and the simulated surface tension within 2% over the whole range of experimental measurement. On the basis of structural studies, the carboxylic headgroups form tight hydrogen bonding, whereas the alkyl chains loosely interact indication of a high electrostatic to van der Waals interaction ratio prevailing the liquid system. The simulated viscosities agree well at high temperatures with experiment, though the agreement is reduced at low temperatures. This can be attributed to describing hexanoic acid system with strong Coulombic interaction, H-bonding, and weak van der Waals interaction all by the same force field. Quite interestingly, the simulated density profile shows an enhancement at the interface characteristic of liquids of high anisotropic molecules and the ionic liquids.

The ZnO nanoparticles were synthesized using marine brown algae (Cystoseira) extract and calcination. For comparison, combustion, and sol–gel methods were employed to synthesize nanoparticles to use as material in dye-sensitized solar cells (DSSCs) photoanode. The produced nanoparticles were characterized using structural and morphological studies by FTIR, SEM, and XRD experiments, respectively. The results revealed that the net hexagonal crystal structure was achieved with a crystal size of less than 100 nm, good purity, spherical shape, and a suitable dimension for fabricating DSSCs. They exhibit enhanced properties due to the variation in their characteristics such as average size, size distribution, and morphology. The ZnO nanoparticles were used to fabricate the DSSCs by the doctor blade method, and the efficacy of each cell was evaluated using voltage–current measurement. The results were in good agreement with the characteristic curve of the commercialized DSSC. The best performance for the fabricated DSSCs was achieved using green synthesized ZnO nanoparticles, because of the influence of their morphology such as smaller crystal size, more grain boundaries, and bigger surface area. The cell’s solar-to-electricity conversion efficiency, short-circuit current, open-circuit voltage, and fill factor were measured as [Formula: see text]1.13%, 3.8[Formula: see text]mA/cm2, 620[Formula: see text]mV, and 54.3%, respectively. The enhanced photovoltaic properties were ascribed to the flower-like morphological structures of the ZnO nanoparticles prepared using the green synthesis method.

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