Analysis of the Influence of the Molecular Volume to Predict Experimental Pressure-Temperature Behavior in the Isotropic-Nematic Phase Transition of PAP, 5CB, MBBA and EBBA

In this work, we have analyzed the experimental pressure-temperature behavior at the isotropic-nematic phase transition of the liquid crystals PAP, 5CB, MBBA, and EBBA at 1 atm by using the HERSW Convex Peg model in conjunction with the IPCM model. We have calculated the molecular volume values for the hard and attractive cores from theoretical quantum calculations at the PM3, PM6, B3LYP/6-311++G(d,p)//PM6, and M06/6-311++G(d,p)//PM6 levels of theory. The results suggest that the best theoretical prediction of the experimental pressure-temperature behavior is obtained when the molecular volume is evaluated at the DFT level.En este trabajo, nosotros analizamos el comportamiento experimental presión-temperatura pa la fase de transición Isotrópica-nemática de los cristales líquidos PAP, 5CB, MBBA, y EBBA a 1 atm usando el modelo HERSW Convex Peg en conjunto con el modelo IPCM. Nosotros calculamos el valor del volumen molecular y cálculos teóricos para los niveles PM3, PM6, B3LyP/6-311++G(d,p)//PM& y M06/6-311++(d,p)//PM6. Los resultados sugieren que la mejor predicción del comportamiento experimental presión-temperatura es obtenido cuando el volumen molecular es evaluado para el nivel DFT

Influence of Bitartrate Ion Concentration in the Copper Electrodeposition Onto a Polycrystalline Gold Electrode

In the present work, the influence of the concentration of bitartrate ions (HT) on the copper electrodeposition process was analyzed. The study was carried out from an aqueous solution containing 0.001 M of CuX (where X = (NO3–)2 ,(Cl–)2, SO42–) and x M KHT (where x = 0.005 M, 0.01 M, and 0.015 M). From voltammetric and chronoamperometric studies, the results indicate that copper electrodeposition is a diffusion-controlled process. The current density transients were well described through a kinetic mechanism involving capacitive and faradaic contributions. The diffusion coefficient values of Cu1+ and Cu2+ result to be similar at the different concentration values of potassium bitartrate used in this work. This work is licensed under a Creative Commons Attribution 4.0 International License

GLOBAL AND LOCAL REACTIVITY DESCRIPTORS FOR PICLORAM HERBICIDE: A THEORETICAL QUANTUM STUDY

In this work, we studied the reactivity of picloram in the aqueous phase at the B3LYP/6-311++G(2d,2p) and MP2/6-311++G(2d,2p) levels of theory through global and local reactivity descriptors. The results obtained at the MP2 level indicate that the cationic form of picloram exhibits the highest hardness while the anionic form is the most nucleophilic. From the Fukui function values, the most reactive site for electrophilic and free radical attacks are on the nitrogen in the pyridine ring. The more reactive sites for nucleophilic attacks are located on the nitrogen atom of the amide group and on the carbon atoms located at positions 2 and 3 in the pyridine ring

Palladium Electrodeposition Onto a Carbon Fiber Ultramicroelectrode

In the present work, it was conducted an electrochemical and kinetic study of Pd electrodeposition onto a 7 μm diameter CF (carbon fiber) ultramicroelectrode from an aqueous solution containing 1 mM of PdCl2 and 1 M NH4Cl as supporting electrolyte, at 25 °C and pH = 4.5. The voltammetric study suggests that at slow scan rates, radial diffusion is favored. The experimental current density transients obtained from the potentiostatic study were well predicted by an instantaneous nucleation and growth mathematical model, that considers the formation of separated hemispherical nuclei. The number of nuclei formed on the electrode surface is potential dependent, and increases as the applied potential diminishes

A Kinetic Study of Silver Electrodeposition Onto Pt Ultramicroelectrodes From Amoniacal Solutions

A kinetic study of the Ag electrodeposition onto Pt ultramicroelectrodes of 10, 15 and 25 µm of diameter from an aqueous solution containing AgNO3 1 mM + NH4NO3 0.1 M was conducted at overpotential conditions through potentiostatic studies. The analysis of the current density transients indicates the existence of two 2D nucleation and growth processes previous to the 3D nucleation and growth process. This work is licensed under a Creative Commons Attribution 4.0 International License

OPTOELECTRONIC PROPERTIES OF TRIPHENYLAMINE BASED DYES FOR SOLAR CELL APPLICATIONS. A DFT STUDY

Abstract: Dye-sensitized solar cells (DSSCs) based on triphenylamine (TPA) as a donor group linked with the acceptor cyanoacrylic acid electron acceptor by 2,2’-bithiophene as π-bridged (D-π-A) has been investigated by Density Functional Theory (DFT) at the B3LYP/6-311G(d,p) level of theory, to establish the conformational orientation of cyanoacrylic acid group as well as evaluate the effect of planarizing the 2,2’-bithiophene unit in position 3 and 3’ by electron withdrawing or donor groups on the electronic structure properties of ground and doping(n,p) states. Also, the Time Dependent Density Functional Theory (TD-DFT) at the CPCM-TD-CAM-B3LYP//CAM-B3LYP/6-311G(d,p) level of theory were selected to modulate the electronic absorption spectra and charge-transfer capabilities of the molecules analyzed in the present work. The results indicate that adding an auxiliary donor or withdrawing group to the 2,2’-bithiophene in the (D-π-A) arrangement allow to modify the LUMO’s energy of the dyes, while the HOMO's energy is slightly affected