Cryptand-Functionalized Highly Oriented Pyrolytic Graphite Electrodes

Abstract

Reproducible materials that have detection properties towards a certain molecule are very important for applications in the fabrication of devices. Among all the substrates that are used, highly oriented pyrolytic graphite allows to clearly image a monolayer. On the other hand, cryptand molecules are versatile because they can sense certain analytes with high selectivity. The highly oriented pyrolytic graphite electrode was first functionalized with an aryl bearing a bromine or an alkyne group to further attach cryptand molecules to its surface. The functionalization was performed through the electroreduction of aryl diazonium salts. While functionalization with an aryl-bromine produced a 20 nm-thick dendritic layer, functionalization of the surface with an aryl bearing a terminal alkyne produced a 9.7 nm-thick multilayer. However, if the diazonium salt is prepared in situ, a 0.9 nm monolayer with aryl–alkyne groups is formed. The alkyne functionalized electrode reacted with a bromo-cryptand through a Sonogashira C–C coupling reaction yielding electrodes functionalized with cryptands. These were immersed in a solution of a Co(II) salt resulting in Co(II)-cryptate modified electrodes, highlighting the ability of the cryptands’ modified electrode to sense metal ions. The electrode surface was analyzed by X-ray photoelectron spectroscopy after each modification step, which confirmed the successful functionalization of the substrate with both the cryptand and the cryptate. Cyclic voltammetry studies showed stable current response after approximately six cycles. Different reduction processes were detected for both cryptand (−1.40 V vs. SCE) and cryptate (−1.22 V vs. SCE) modified highly oriented pyrolytic graphite.

Molecular dynamics simulation of the amorphous graphite-like membrane deposited on ideal graphite substrate

“…1–3 PyG has good heat resistance, thermal and electrical conductivity and stable chemical properties, and widely used in propellant rocket nozzles, gates of electronic tubes and various protective coatings for electronic devices. 4–6 Microstructural studies of PyG show that PyG graphite layers are stacked often in a non-ideal ABAB stacking manner, i.e. , in a disordered layer stacking in the [001] direction, and thus the general PyG graphite interlayer distance is slightly greater than the layer spacing of 3.4 Å for ideal single-crystal graphite.…”

“…[1][2][3] PyG has good heat resistance, thermal and electrical conductivity and stable chemical properties, and widely used in propellant rocket nozzles, gates of electronic tubes and various protective coatings for electronic devices. [4][5][6] Microstructural studies of PyG show that PyG graphite layers are stacked oen in a non-ideal ABAB stacking manner, i.e., in a disordered layer stacking in the [001] direction, and thus the general PyG graphite interlayer distance is slightly greater than the layer spacing of 3.4 Å for ideal singlecrystal graphite. 7 PyG preparation conditions, such as temperature and pressure of CVD pyrolysis, ow rates of carbon source gas and substrate selection, have a signicant impact on the microstructure and properties of PyG, thus the preparation of high-quality anisotropic pyrolytic graphite and the study of microscopic kinetic processes have always been the focus of attention.…”