“Clay nanotube composite assembly: core-shell catalysts and functional biocoatings”

Abstract

We developed self-assembly of halloysite clay nanotubes for producing organized organic / inorganic heterostructures. These 50-nm diameter and 1 mkm length alumosilicate nanotubes allow for 10-20 wt. % loading with metal, dye, drugs or other chemicals and templating mesosilica; these nanoclay may be also assembled in ordered arrays at interfaces and surfaces [1]. Halloysite nanotubes are safe, available in thousand tons natural material, which is not harmful for environment and allows for “green” water-based chemical processing.

Biocoating

Halloysite self-assembly on hair and wool fibers allows for 3-4 mkm clay coating. Encasing of dye or drugs into these nanotubes applied to hair from aqueous dispersions provides stable coloring and antilacing effect. Clay nanotubes were also processed in oriented arrays with brush assistant shear force deposition or using “coffee ring” ensemble formation mechanisms. The synergy of shear forces and the electrostatic Onsager’s ordering interaction of these charged nanotubes defined their alignment. These nanoclay patterns supported the stem cell proliferation with alignment and promoted osteogenesis differentiation without growth factor. This simple method for oriented clay nanotube patterns on glass or plastic is promising for bio-tissue engineering. Mesocatalysts [3]: 2-5 nm metal particles (Au, Ag, Co, Ru, Fe2O3, ZrO2, Cu-Ni and CdS) inside / outside of these aluminosilicate nanotubes were produced. The hydrogenation of benzene, phenol, hydrogen production and impacts of the core-shell architecture, as well as metal particle size and seeding density were optimized for high efficiency catalysis. A new self-assembly strategy for ordered silica arrays onto halloysite clay nanotubes essentially improved mesoporous MCM-41 material. Such MCM-41 / halloysite composite is stable up to 1,100 °C and 500 MPa pressure due to armoring of bulk silica with embedded strong ceramic nanotubes. It demonstrated 25 % sulfur reduction in liquid products of vacuum gas oil catalytic cracking. Metal-ceramic core-shell tubule systems are promising for mesocatalytic systems: metals were placed selectively outside or inside the nanotubes thus providing thermo- and aggregation resistance.

1. Y. Lvov, W. Wang, R. Fakhrullin, Adv. Mater., v.28, 1227–1250, 2016, “Halloysite Clay Nanotubes for Loading and Sustained Release of Functional Compounds
2. A. Panchal, G. Fakhrullin, Y. Lvov, Nanoscale, v.10, 18205 — 18216, 2018, “Clay nanotube hair self-assembly coating for coloring and drug delivery” and X. Zhao, M. Liu, Y. Lvov, et al, Small, v.15, 1900357, 2019, “Clay nanotube aligned with shear forces for stem cells patterning.”
3. V. Vinokurov, Y. Lvov, et al, Chem. Bull. Japan, v.92, 61, 2019, “Core-shell clay nanotubes with inside/outside ruthenium deposition: catalytic activity for aromatics hydrogenation,” and A. Glotov, Y. Lvov, et al Chem. Comm, v.55, 5507, 2019, “Templated self-assembly of ordered mesoporous silica on clay nanotubes.”