Hollow Carbon Nanotube Microspheres and Hemimicrospheres

The layer-by-layer (LBL) assembly of multiwalled carbon nanotubes (MWNTs) and diazoresin (DR) is realized via the electrostatic interactions on planar substrates and polystyrene (PS) microsphere templates. The successful planar and spherical growth of DR/MWNT multilayers is monitored by scanning electron microscopy (SEM) and UV−vis spectrophotometry. Upon UV irradiation or heating, the ionic bonds between MWNTs and DR transform into covalent bonds, which significantly improves the stability of the DR/MWNT multilayers. The MWNT shell on PS cores can be cross-linked by the formation of covalent bonds upon heating. Due to the incomplete irradiation, UV fails to cross-link the MWNT shell. The PS cores could be removed by calcination, and hollow MWNT microspheres are produced, which well maintain the morphology of their precursors, while by dissolving the PS cores with organic solvents, novel MWNT hemimicrospheres are obtained. It is proposed that, in the drying process, the evaporation of solvent results in the collapse of MWNT microspheres and the formation of MWNT hemimicrospheres.