6533b830fe1ef96bd1297c76
RESEARCH PRODUCT
Orientation of charged clay nanotubes in evaporating droplet meniscus.
Yuri LvovYuri LvovGiuseppe CavallaroYafei Zhaosubject
Halloysite nanotubes;Alignment;Droplet evaporation;Coffee ring;Liquid crystalMaterials scienceHalloysite nanotubeCoffee ring effectNanotechnologyengineering.materialHalloysiteBiomaterialsDroplet evaporationColloidColloid and Surface ChemistryAdsorptionLiquid crystalSurface chargeAlignmentMicrochannelNanotubesHalloysite nanotubesOsmolar ConcentrationHydrogen-Ion ConcentrationSurfaces Coatings and FilmsElectronic Optical and Magnetic MaterialsChemical engineeringLiquid crystalengineeringCoffee ringMicroscopy Electron ScanningClayNanorodAluminum SilicatesCrystallizationdescription
© 2014 Elsevier Inc. During drying, an aqueous suspension of strongly charged halloysite clay nanotubes concentrates at the edge of the droplet ("coffee-ring" effect) which provides alignment of the tubes along the liquid-substrate contact line. First, the surface charge of the nanotubes was enhanced by polyanion adsorption inside of the lumen to compensate for the internal positive charges. This increased the magnitude of the ξ-potential of the tubes from -36 to -81mV and stabilized the colloids. Then, colloidal halloysite was dropped onto the substrate, dried at 65°C and after a concentration of ~0.05mgmL-1 was reached, the alignment of nanotubes occurred starting from the droplet edges. The process was described with Onsager's theory, in which longer nanorods, which have higher surface charge, give better ordering after a critical concentration is reached. This study indicates a new application of halloysite clay nanotubes in polymeric composites with anisotropic properties, microchannel orientation, and production of coatings with aligned nanotubes.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2015-01-01 | Journal of colloid and interface science |