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We have investigated the optical absorption of metallic and semiconducting carbon nanotubes/CH 3 NH 3 PbI 3 micro- and nanowire composites. Upon visible light illumination semiconducting carbon nanotube based samples show a photo-induced doping, originating from the charge carriers created in the perovskite while this kind of change is absent in the composites containing metallic nanotubes, due to their strikingly different electronic structure. The response in the nanotubes shows, beside a fast diffusion of photo-generated charges, a slow component similar to that observed in pristine CH 3 NH 3 PbI 3 attributed to structural rearrangement, and leading to slight, light induced changes of the optical gap of the perovskite. This charge transfer from the illuminated perovskite confirms that carbon nanotubes (especially semiconducting ones) can form efficient charge-transporting layers in the novel organometallic perovskite based optoelectronic devices.

Field-effect phototransistors were fabricated based on individual carbon nanotubes (CNTs) sensitized by CH3NH3PbI3 nanowires (MAPbI3NWs). These devices represent light responsivities of R = 7.7 × 10(5) A W(-1) under low-lighting conditions in the nW mm(-2) range, unprecedented among CNT-based photodetectors. At high incident power (∼1 mW mm(-2)), light soaking results in a negative photocurrent, turning the device insulating. We interpret the phenomenon as a result of efficient free photoexcited charge generation and charge transfer of photoexcited holes from the perovskite to the carbon nanotube. The charge transfer improves conductance by increasing the number of carriers, but leaves electrons behind. At high illumination intensity their random electrostatic potential quenches mobility in the nanotube.

By exposing flat and curved carbon surfaces to coronene, a variety of van der Waals hybrid heterostructures are prepared, including coronene encapsulated in carbon nanotubes, and coronene and dicoronylene adsorbed on nanotubes or graphite via π-π interactions. The structure of the final product is determined by the temperature of the experiment and the curvature of the carbon surface. While at temperatures below and close to the sublimation point of coronene, nanotubes with suitable diameters are filled with single coronene molecules, at higher temperatures additional dimerization and oligomerization of coronene occurs on the surface of carbon nanotubes. The fact that dicoronylene and possible higher oligomers are formed at lower temperatures than expected for vapor-phase polymerization indicates the active role of the carbon surface used primarily as template. Removal of adsorbed species from the nanotube surface is of utmost importance for reliable characterization of encapsulated molecules: it is demonstrated that the green fluorescence attributed previously to encapsulated coronene is instead caused by dicoronylene adsorbed on the surface which can be solubilized and removed using surfactants. After removing most of the adsorbed layer, a combination of Raman spectroscopy and transmission electron microscopy was employed to follow the transformation dynamics of coronene molecules inside nanotubes., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Herein, we report the first example of supramolecular carbon nanotube (CNT)-based ion catchers as simple and effective tools for removing divalent metal ions from organic solvents. In particular, covalently functionalized multi-walled carbon nanotubes (MWCNTs) appended with pyridyl groups self-aggregate in solution into bundles in the presence of divalent metal ions (e.g., Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, Zn²⁺). Such self-aggregation behavior leads to insoluble materials that, upon treatment with weak acids, can be regenerated and reused for further complexation. All materials and complexation/decomplexation steps were thoroughly characterized by using X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and different microscopy-based techniques, namely, transmission electron, scanning electron, and atomic force microscopy (TEM, SEM, and AFM). The supramolecular system engineered in this work is the first example of an easy and fully sustainable material with great potential applications for depolluting liquid waste from metal contamination., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)