Ion Selective Electrode Mediated by Transfer Layer of Graphene Oxide for Detection of Ca2+ with Highly Sensitivity and Selectivity

A Ca2+ selective microelectrode was proposed through electrodepositing graphene oxide (GO) on carbon fiber as an efficient ion-electron transfer layer. The gold leaves were further synthesized at GO surface to increase the specific surface area and provide a substrate for assembly of the specific ligands for Ca2+. GO with negative charges greatly facilitated the electron transfer process from the recognition center to electrode surface, resulting in the apparently enhanced sensitivity towards Ca2+. Moreover, the developed ion-selective microelectrode exhibited good selectivity to Ca2+, and a good linear range from 10 μM to 10 mM with a detection limit of 5.91±0.46 μM.

Síntesis, simulación y propiedades ópticas de un resorcinareno portador de quinolinas

El diseño y síntesis de macromoléculas orgánicas conjugadas es de interés en el área de la optoelectrónica, para la fabricación de dispositivos optoelectrónicos, tales como celdas solares orgánicas, celdas solares tipo perovskita, OLEDS, Transistores delgados de efecto de campo orgánicos, sensores, etc. En este trabajo se reporta la simulación molecular mediante DFT de un dendrímero de tipo resorcinareno con segmentos de quinolina y tiofeno en la periferia, designado como D. El dendrímero se sintetizo siguiendo el método convergente de acoplamiento del dendrón quinolínico al centro. El dendrímero D fue caracterizado mediante espectroscopia de 1H-RMN, FT-IR. El estudio de las propiedades ópticas se realizó mediante espectroscopia de UV vis y Fluorescencia estática y dinámica, los resultados indican que el dendrímero presenta una emisión máxima a 574 nm que se ubica en la región verde del espectroelectromagnético. El cálculo del band gap óptico y teórico fue de 2.78 y 3.3 eV respectivamente lo que ubica a este material, dentro de los semiconductores orgánicos. Los valores teóricos de los niveles de energía de los orbitales frontera HOMO y LUMO de 5.52 y 2.18 eV, sugieren su posible aplicación como HTL (hole transfer layer) en la fabricación de una celda solar orgánica de heterounión.

Friction, Scuffing and Transfer Layer Formation in Lubricated Sliding of EN31 Steel and Tungsten Carbide (WC): Surface Topography Effects

Surface topographies play a critical role in controlling friction, surface damage and transfer layer formation in engineering applications; hence understanding this is of great importance. In this work, experimental studies were carried out to understand the influence of surface topography on friction, scuffing and transfer layer formation in completely immersed lubricated sliding interactions. For this, sliding experiments were carried out in sphere on flat configuration using EN31 steel flats and Tungsten Carbide pin countersurface. Perpendicular and parallel surface topographies were induced onto the steel flats. Experiments were conducted at high normal loads of 1000N, 2000N and 3000N. The results show that Surface topography has a significant influence on the frictional response. When the topography directionality was perpendicular to the sliding direction, scuffing was observed only at a high load of 3000N. A ‘peak friction’ was also observed during the occurrence of scuffing. When the directionality in topography was parallel to sliding direction, scuffing and surface damage occurred from 2000N itself, accompanied by a high amount of transfer layer formation. This can be attributed to the directionality of parallel topography, which displaces away the lubricant during sliding interaction, creating metal-to-metal contact and hence leading to scuffing and higher transfer layer formation.

Effect of Transverse Magnetic Field On Microstructure And Mechanical Properties of Ti-6Al-4V Manufactured By Laser-MIG Hybrid Welding

In this paper, the external transverse magnetic field is used to assist the laser-MIG hybrid welding for Ti-6Al-4V (TC4). The microstructure and mechanical properties such as microhardness and tensile properties of the weld joints under 24 mT external magnetic field (EMF) and the referring weld joint without EMF are investigated and discussed. Results show that transfer layer (TL) performs the lowest microhardness in the weld seam and tensile specimens fail in this area for the referring weld joint without EMF, which indicates the TL is the weakest zone in the weld seam. The mechanical properties of weld seam improve significantly under 24 mT EMF, which average microhardness in TL increases 9.3% and failure stress of tensile specimens improve by 16.7%, whilst a mixed fracture mode is operative in the fracture surfaces. The research reveals the elementary microstructure of TC4 laser-MIG hybrid welding is in correlation to welding heat input under the influence of EMF.