Fabrication of smallest single-walled carbon nanotubes in molecular sieves: A comparison between SAPO-11 and AlPO4-11

Decomposition mechanism of dipropylamine (DPA) molecules in the channels of AlPO4-11 and Si-incorporated AlPO4-11 (SAPO-11) zeolite crystals was investigated by mass spectrometry, with the aim to fabricate high-density 0.3-nm single-walled carbon nanotubes (SWNTs). In comparison with neutral AlPO4-11, the organic template DPA is bonded to SAPO-11 framework by strong chemical interaction. As a result, a significant amount of hydrocarbon molecules are trapped in the channels during carbonization process. In addition, the SAPO-11 framework plays an important catalytic role in the pyrolysis and conversion of the organic molecules to SWNTs within the crystal channels, owing to the Bønsted acid sites. The resulting SWNTs have higher density than those fabricated without Si doping, evidenced by the clear and strong radial-breathing modes in Raman spectra.