A LabRam Horiba spectrometer, equipped with a CCD multichannel detector and two laser sources: one He-Ne laser with a 633 nm line and an Argon laser giving several excitation lines among them 514, 488 adn 457 nm. The system is also equipped with a heating stage which allows us analysis under controlled atmospheres from sub-ambient temperature up to 1800K.
Nowadays, Raman spectroscopy is widely used to characterize SWNT (position, intensity, and widht of the bands depend on the carbon nature). Indeed, information about tube diameter can be obtained; besides it is possible to distinguish between metallic and semiconducting tubes because of the different Raman spectra for semiconducting and metallic SWNT.
The role of water in carbon feed on the surface-guided growth of horizontally aligned single-walled carbon
nanotubes (HA-SWCNTs) was investigated. It is shown that the amount of water can be optimized to favor HA-SWCNT growth, which is proposed to be due to selective etching of carbon deposits at carbon–metal interface. Without water, nanotube–nanotube interaction and carbon accumulation at the interface are disproportionately large compared to the rate of nanotube growth, leading to catalyst deactivation. With excess water, suppression of nanotube growth occurs, resulting in reduced carbon yield on the surface.
Intermediate carbon/water feed ratios achieve cleaner growth with high efficiency.