engleski

Large-scale transfer and characterization of macroscopic periodically nano-rippled graphene

Nano-rippled graphene, a structurally modified graphene, presents a novel material with a large range of possible applications including sensors, electrodes, coatings, optoelectronics, spintronics and straintronics. In this work we have synthesized macroscopic single layer graphene with well- defined uniaxial periodic modulation on a stepped Ir(332) substrate and transferred it to a dielectric support. The applied fast transfer process does not damage the Ir crystal which can be repeatedly used for graphene synthesis. Upon transfer, a millimeter sized graphene flake with a uniform periodic nano- ripple structure is obtained, which exhibits a macroscopically measurable uniaxial strain. The periodic one dimensional arrangement of graphene ripples was confirmed by atomic force microscopy and polarized Raman measurements. An important feature of this system is that the graphene lattice is rotated in several different, well-defined orientations with respect to the direction of the ripple induced uniaxial strain. Moreover, geometry of the ripples can be modified by changing the graphene synthesis parameters.properties of the synthesized TiO2 nanomaterials were investigated with high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), high- resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD) and X- ray photoelectron spectroscopy (XPS). The NWs and NTs were characterized using Raman and Fourier transform infrared (FT- IR) spectroscopy as well as Brunauer-Emmett-Teller (BET) measurements. Surface properties, i.e. pHiep and pHpzc of NWs and NTs were determined from electrokinetic measurements, potentiometric mass and electrolyte titrations. The relative acidity for the NWs is found to be in the interval 3 < pHiep < 4 in comparison with the NTs, with 4 < pHiep < 6. The observed differences in the relative acidity are correlated with differences in crystal structure of the studied nanomaterials and their resulting morphology. In addition, our results reveal a strong electrolyte effect on the characteristic points, pHiep and pHpzc, especially the higher cation affinity for both TiO2 nanomaterials surfaces that has a significant effect on the pH of the system. Application of the multisite complexation (MUSIC) model yields a satisfactory description of the electrokinetic data and can explain observed salt effect.

chemical-vapor-deposition ; atomic-force microscopy ; raman-spectroscopy ; suspended graphene ; strain ; sheets ; growth ; carbon ; membrane ; graphite

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