Sol-gel chemistry mediated Zn/Al-based complex dispersant for SWCNT in water without foam formation

We report a bimetallic Zn/Al complex as an efficient inorganic dispersant for SWCNT, synthesized from Zn(CH3COO)(2) and Al(NO3)(3). The Zn/Al complex shows more than four times greater efficiency at dispersing SWCNT than widely used surfactants (CTAB and SDS). Besides remarkable dispersibility, the Zn/Al complex does not foam upon any shaking treatment and it can be used just after quick dissolution of the powdered form, which is a marked advantage over surfactants. The Zn/Al complex, containing amorphous Al(CH3COO)(3) and a complex of Zn2+ and NO3- ions, should have a unique dispersion mechanism, differing from the surfactants. Al(CH3COO)(3) has higher affinity for SWCNT than ions, adsorbing onto its surface in the first layer and attracting Zn2+ and NO3- ions. Charge transfer interactions between the Zn/Al complex and SWCNT, as evidenced by optical absorption spectroscopy, should induce a charge on SWCNT; the zeta potential of such coated SWCNT was +55 mV, indicating a high dispersion stability in aqueous media. Hence, the Zn/Al complex can widen the applications of SWCNT to various technologies such as the transparent and conductive films, as well as high performance composite polymers. (C) 2015 Elsevier Ltd. All rights reserved.ArticleCARBON. 94:518-523 (2015)journal articl

Sol–gel chemistry mediated Zn/Al-based complex dispersant for SWCNT in water without foam formation

We report a bimetallic Zn/Al complex as an efficient inorganic dispersant for SWCNT, synthesized from Zn(CH3COO)(2) and Al(NO3)(3). The Zn/Al complex shows more than four times greater efficiency at dispersing SWCNT than widely used surfactants (CTAB and SDS). Besides remarkable dispersibility, the Zn/Al complex does not foam upon any shaking treatment and it can be used just after quick dissolution of the powdered form, which is a marked advantage over surfactants. The Zn/Al complex, containing amorphous Al(CH3COO)(3) and a complex of Zn2+ and NO3- ions, should have a unique dispersion mechanism, differing from the surfactants. Al(CH3COO)(3) has higher affinity for SWCNT than ions, adsorbing onto its surface in the first layer and attracting Zn2+ and NO3- ions. Charge transfer interactions between the Zn/Al complex and SWCNT, as evidenced by optical absorption spectroscopy, should induce a charge on SWCNT; the zeta potential of such coated SWCNT was +55 mV, indicating a high dispersion stability in aqueous media. Hence, the Zn/Al complex can widen the applications of SWCNT to various technologies such as the transparent and conductive films, as well as high performance composite polymers. (C) 2015 Elsevier Ltd. All rights reserved.ArticleCARBON. 94:518-523 (2015)journal articl

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^–1, respectively, being close to those of water (71.5° and 71 mN m^–1). 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 S₁₁ 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