Semiconducting single-walled carbon
nanotubes (s-SWCNTs) with a
diameter of around 1.0–1.5 nm, which present bandgaps comparable
to silicon, are highly desired for electronic applications. Therefore,
the preparation of s-SWCNTs of such diameters has been attracting
great attention. The inner surface of SWCNTs has a suitable curvature
and large contacting area, which is attractive in host–guest
chemistry triggered by electron transfer. Here we reported a strategy
of host–guest molecular interaction between SWCNTs and inner
clusters with designed size, thus selectively separating s-SWCNTs
of expected diameters. When polyoxometalate clusters of ∼1
nm in size were filled in the inner cavities of SWCNTs, s-SWCNTs with
diameters concentrated at ∼1.3–1.4 nm were selectively
extracted with the purity of ∼98% by a commercially available
polyfluorene derivative. The field-effect transistors built from the
sorted s-SWCNTs showed a typical behavior of semiconductors. The sorting
mechanisms associated with size-dependent electron transfer from nanotubes
to inner polyoxometalate were revealed by the spectroscopic and in situ electron microscopic evidence as well as the theoretical
calculation. The polyoxometalates with designable size and redox property
enable the flexible regulation of interaction between the nanotubes
and the clusters, thus tuning the diameter of sorted s-SWCNTs. The
present sorting strategy is simple and should be generally feasible
in other SWCNT sorting techniques, bringing both great easiness in
dispersant design and improved selectivity.