Filling and capping multiwall carbon nanotubes with silicon nanocrystals dispersed in SiO2-based spin on glass

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Abstract
Silicon nanocrystals (Si-ncs) are particularly interesting not only for their optical properties but also because recent developments have made possible the production of optoelectronic devices. In the present work, an approach is proposed either to introduce Si-ncs at room temperature inside the multiwall carbon nanotubes (MWCNTs) or to cap Si-nc on one open end of MWCNT. The Si-ncs dispersed in SiO2-based spin on glass solution have been preliminary disaggregated in an ammonia solution and contacted with open MWCNTs with different average inner diameters (IDs) within an ID range of 6–40nm. The ends of MWCNTs have been opened by a thermal annealing at appropriate temperatures that are previously evaluated from thermogravimetric investigations. On the tip of MWCNTs of small inner diameters it has been possible to stick a single Si-nc and cap the open end of the tube (Si-nc∕MWCNT), whereas with increasing IDs of MWCNTs, Si-ncs were introduced inside the tubule (Si-ncs-MWCNT). High resolution transmission electron microscopy and diffraction patterns provide evidence for many Si-ncs incorporated inside the MWCNTs. The capillary forces provided by the opening of the MWCNTs are strong enough to attract and even more to carry the Si-ncs within nanotubes far from their mouth. Photoluminescence properties of Si-nc inside the MWCNTs are investigated at room temperature. Implications on the interest of their composite material, Si-ncs-MWCNT, are discussed in terms of chemical and mechanical stabilizations, wiring, and handling single Si-nc.