Labeling and monitoring the distribution of anchoring sites on functionalized CNTs by atomic layer deposition

The chemical inertness of graphite and, in the case of tubes, of rolled up few layer graphene sheets, requires some degree of “defect engineering” for the fabrication of carbon based heterostructured materials. It is shown that atomic layer deposition provides a means to specifically label anchoring sites and can be used to characterize the surface functionality of differently treated carbon nanotubes. Direct observation of deposited titania by analytical transmission electron microscopy reveals the location and density of anchoring sites as well as structure related concentrations of functional groups on the surface of the tubes. Controlled functionalization of the tubes therefore allows us to tailor the distribution of deposited material and, hence, fabricate complex heterostructures

MOx/CNTs Hetero-Structures for Gas Sensing Applications: Role of CNTs Defects

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MOx/CNTs Hetero-Structures for Gas Sensing Applications: Role of CNTs Defects

AbstractThe preparation, characterization and sensing properties of CNT composites with a thin metal oxide (MOx) surface layer is presented. Atomic layer deposition (ALD) was applied for the coating of the inner and outer CNTs walls with thin films of ZnO and SnO2 of precisely controlled thicknesses. Differently treated CNTs with different degree of surface functionalization were used as support for the oxide films. The sensing properties of the obtained composite materials towards NO2 were investigated and related to the morphological and microstructural characteristics of both the coating and support. SnO2-based composites on CNTs treated at 700°C show enhanced performance as sensors, making them suitable for practical applications

The role of the nebulizer on the sodium interferent effects in inductively coupled plasma atomic emission spectrometry

The role of the nebulizer on the sodium chloride interferent effects in ICP-AES was investigated. Three different pneumatic nebulizers coupled to a cyclonic spray chamber were investigated: a V-groove (VGN) and two new pneumatic concentric nebulizers specifically designed to work with saline solutions (the 'Seaspray' nebulizer, SSN, and experimental nebulizer, EN). The effect of the salt concentration on the characteristics of the aerosols generated by the nebulizers (primary aerosols) and those at the exit of the spray chamber (tertiary aerosols) on the transport parameters and on the analytical figures of merit in ICP-AES were evaluated. The characteristics of the primary aerosols were related to their critical dimensions and were independent of the solution salt concentration. Solvent and analyte transport rates were related to the characteristics of the primary aerosols. Thus, the SSN provided the highest solution transport rates followed by the EN and VGN. The Mn II emission signal correlated quite well with transport parameters. When the salt concentration increased, an interference effect on the ICP-AES emission signal was observed. This effect was related to the nebulizer employed. Thus, for the SSN, the effect of the sodium chloride on the emission signal was different for the ionic and atomic lines. For the remaining nebulizers, a depressive effect of the salt concentration on the emission signal was always observed irrespective of the line considered. The magnitude of the interference was different for each nebulizer and was related to the amount of solvent transported to the plasma. In general terms, by increasing the salt concentration, poorer signal precision and limits of detection were obtained. These results confirm the importance of sustaining robust plasma conditions to reduce the sodium chloride interferences