Integrated carboxylic carbon nanotube pathways with membranes for voltage-activated humidity detection and microclimate regulation.

This work describes some single walled carboxylic carbon nanotubes with outstanding transport properties when assembled in a 3D microarray working like a humidity membrane-sensor and an adjustable moisture regulator. Combined nano-assembly approaches are used to build up a better quality pathway through which assisted-charge and mass transport synchronically takes place. The structure-electrical response relationship is found, while controllable and tunable donor-acceptor interactions established at material interfaces are regarded as key factors for the accomplishment of charge transportation, enhanced electrical responses and adjustable moisture exchange. Raman and infrared spectroscopy provides indications about the fine structural and chemical features of the hybrid-composite membranes, resulting in perfect agreement with related morphology and electrical properties. Enhanced and modular electrical response to changes in the surrounding atmosphere is concerned with doping events, while assisted moisture regulation is discussed in relation to swelling and hopping actions. The electro-activated hybrid-composite membrane proposed in this work can be regarded as an attractive 'sense-to-act' precursor for smart long-distance monitoring systems with capability to adapt itself and provide local comfortable microenvironments.

Transport properties of alkali-doped multi walled carbon nanotubes.

In this work we propose a study on electrical properties of multiwalled carbon nanotubes (MWCNT) doped with the most commonly used alkali metals. We report resistivity measurements of MWCNT exposed to doping with Li, Na, K and Cs. Our results show that, increasing the alkali exposure, the resistance of the doped sample decreases denoting a progressive sample metallization. The changes in resistivity, contrary to that observed for single walled carbon nanotubes (SWCNT) in our previous work, are independent upon the alkali properties but appear related to alkali intercalation effects in the MWCNT random network. The doping effects have been also controlled by X-ray photo electron spectroscopy (XPS). The spectra confirm the absence of chemical bonds between carbon nanotubes and alkali, validating the hypothesis of intercalation of alkali in the interstitial channels between the tubes. Our results are also confirmed by comparison between SEM images of single walled and multiwalled carbon nanotubes.

Cathode-luminescence from extrinsic impurities in bundles of carbon nanotubes: a possible role.

Luminescence spectra obtained by electron bombardment of carbon nanotubes bundles show an UV signal centered at about 380 nm. We show that these transitions are extrinsic to nanotubes, in the sense that they are not linked to any carbon compound or structure, but are caused by the residual catalyst material used in the growth process. A possible role of such luminescence attributable to impurities is also discussed. In fact our luminescence measurements, in association with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and X-ray photoelectron spectroscopy (XPS), permit us to assign these spectral bands to Zn and Al oxides. Our conclusions, supported by data in literature, and the comparison with the quantitative results obtained by LA-ICP-MS spectrometry (which detects ppm) allows us to define cathode-luminescence analysis as a good technique to control cleanness and purity of carbon nanotube samples.