Orientation of charged clay nanotubes in evaporating droplet meniscus

Giuseppe Cavallaro, Yafei Zhao, Yuri Lvov

Risultato della ricerca: Article

40 Citazioni (Scopus)

Abstract

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 −81 mV and stabilized the colloids. Then, colloidal halloysite was dropped onto the substrate, dried at 65 °C and after a concentration of ∼0.05 mg mL−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.
Lingua originaleEnglish
pagine (da-a)68-77
Numero di pagine10
RivistaJournal of Colloid and Interface Science
Volume440
Stato di pubblicazionePublished - 2015

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Nanotubes
Clay
Surface charge
Coffee
Colloids
Substrates
Microchannels
Nanorods
Contacts (fluid mechanics)
Suspensions
Drying
clay
Adsorption
Coatings
Composite materials
Liquids

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

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Orientation of charged clay nanotubes in evaporating droplet meniscus. / Cavallaro, Giuseppe; Zhao, Yafei; Lvov, Yuri.

In: Journal of Colloid and Interface Science, Vol. 440, 2015, pag. 68-77.

Risultato della ricerca: Article

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abstract = "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 −81 mV and stabilized the colloids. Then, colloidal halloysite was dropped onto the substrate, dried at 65 °C and after a concentration of ∼0.05 mg mL−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.",
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AU - Zhao, Yafei

AU - Lvov, Yuri

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N2 - 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 −81 mV and stabilized the colloids. Then, colloidal halloysite was dropped onto the substrate, dried at 65 °C and after a concentration of ∼0.05 mg mL−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.

AB - 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 −81 mV and stabilized the colloids. Then, colloidal halloysite was dropped onto the substrate, dried at 65 °C and after a concentration of ∼0.05 mg mL−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.

KW - Alignment

KW - Coffee ring

KW - Droplet evaporation

KW - Halloysite nanotubes

KW - Liquid crystal

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