2 research outputs found
Essential Role of Viscosity of SWCNT Inks in Homogeneous Conducting Film Formation
Newly
developed inorganic single-wall carbon nanotube (SWCNT) inks
of the Zn/Al complex and colloidal silica give a quite homogeneous
SWCNT film on the polyethylene terephthalate (PET) substrate by the
bar-coating method, whereas the surfactant-based SWCNT inks of sodium
dodecyl sulfonate (SDS) and sodium dodecyl benzene sulfonate (SDBS)
cannot give a homogeneous film. The key properties of SWCNT inks were
studied for the production of homogeneous SWCNT films. The contact
angle and surface tension of the inorganic dispersant-based SWCNT
inks were 70° and 72 mN m<sup>–1</sup>, respectively,
being close to those of water (71.5° and 71 mN m<sup>–1</sup>). The viscosity was significantly higher than that of water (0.90
mPa·s), consequently, providing sufficient wettability, spreadability,
and slow drying of the ink on the substrate, leading to homogeneous
film formation. On the other hand, the surfactant dispersant-aided
SWCNT inks have the contact angle and surface tension twice lower
than the inorganic dispersant-based SWCNT inks, guaranteeing better
wettability and spreadability than the inorganic dispersant-based
inks. However, the small viscosity close to that of water induces
a heterogeneous flow of SWCNT ink on rapid drying, leading to inhomogeneous
film formation
Aqueous Nanosilica Dispersants for Carbon Nanotube
Nanosilicas can disperse single-wall
carbon nanotube (SWCNT) in
aqueous solution efficiently; SWCNTs are stably dispersed in aqueous
media for more than 6 months. The SWCNT dispersing solution with nanosilica
can produce highly conductive transparent films which satisfy the
requirements for application to touch panels. Even multiwall carbon
nanotube can be dispersed easily in aqueous solution. The highly stable
dispersion of SWCNTs in the presence of nanosilica is associated with
charge transfer interaction which generates effective charges on the
SWCNT particles, giving rise to electrostatic repulsion between the
SWCNTs in the aqueous solution. Adhesion of charged nanosilicas on
SWCNTs in the aqueous solution and a marked depression of the S<sub>11</sub> peak of optical absorption spectrum of the SWCNT with nanosilicas
suggest charge transfer interaction of nanosilicas with SWCNT. Thus-formed
isolated SWCNTs are fixed on the flexible three-dimensional silica
jelly structure in the aqueous solution, leading to the uniform and
stable dispersion of SWCNTs