Small-Angle Neutron Scattering from Labeled Single-Wall Carbon Nanotubes

Small-angle neutron scattering (SANS) is used with the “high-concentration” method to extract single-particle scattering from single-wall carbon nanotubes (SWNTs). The SWNT material was labeled by covalently attaching −C 4 H 9 or −C 4 D 9 groups by use of free radical chemistry. Mixtures of SWNT-C 4 H 9 and SWNT-C 4 D 9 were dispersed in D 2 O containing 1% sodium lauryl sulfate- d 23 (SLS) by use of sonication. SLS matches the neutron contrast of D 2 O so that all of the SANS is due to the labeled SWNT. Thermogravimetric analysis shows that mass fractions of butyl groups attached to the SWNT-C 4 H 9 and the SWNT-C 4 D 9 were well matched. The scattering had a power law of −2.5, which is characteristic of a “particle” made of clustered SWNTs. The clustering seen in SWNT scattering is due to collections of SWNTs that do not exchange in a dynamic equilibrium with other nanotubes.