ChBE Seminar Series: Yuri Lvov, Louisiana Tech University
Halloysite clay nanotubes for functional composites
Halloysite alumosilicate tubes with a 15 nm lumen, 50 nm external diameter, and length of ca. 1 µm have been developed as an entrapment system for loading, storage, and controlled release of chemical agents (anticorrosion, flame-retardancy, biocides, drugs, proteins and DNA). Studies to enable the nanotube control of release rates from hours to days and months are being undertaken. By the formation of nanoshells or by creation of caps at the tube ends it is possible to extend release rate. Halloysite forms stable aqueous colloids and is well admixable with polar, low polar plastics and biopolymes. Protective halloysite coatings and a self-healing approach have been tested for repair mechanisms through response activation by external impacts. Catalytic nanoparticle formation inside/outside of the tubes allowed for efficient catalysis at 300-400 °C for auto exhausting systems.
TEM images of halloysite nanotubes dispersed in water (a-b), SEM image of layer-by-layer nanocoating with halloysite multilayer (c), and halloysite nanotube coated with polyelectrolyte + 7 nm diameter silica
Doping loaded clay nanotubes into polymeric matrix (polyurethane, polypropylene, siloxane, epoxy, PMMA) provides sustained inhibitors’ release and this ceramic “skeleton” is enhancing the composite strength. Doping clay nanotubes into paint at 3-5 wt. % provides sustained release of anticorrosion and antibacterial agents resulting in 2-times longer metal protection as well as in 50-100 % increase in the coating strength and adhesivity.
Biocompatible halloysite nanotubes allow for 10 wt. % loading with drugs and proteins preserving their activity and providing 10-50 hrs release time. Applications of halloysite as nano-scale containers include the use of the clay tubes for sustained drug delivery in bone implants and dental fillings allowing for 14-20 days release time. Loading halloysite with enzymes and DNA represents a new nano-encapsulation system for cellular delivery.
Halloysite nanotubes are available in thousands of tons, and remain sophisticated and novel nanomaterials which can be used as smart nano-containers. Halloysite is also a "green" material and will not add risk to the environment.
Dr. Yuri M. Lvov is a Professor of Chemistry, T. Pipes Eminent Endowed Chair on Micro and Nanosystems at the Institute for Micromanufacturing, Louisiana Tech University. He earned his Ph.D. in Physical Chemistry (protein crystallography) from #1 Russian university, M. Lomonosov’s Moscow State University in 1979, then worked at the Institute of Crystallography, Russian Academy of Sciences where got Doctor of Science in physics in 1991. After Soviet Union collapsed, he worked in the world famous research centers in Germany (Max Planck Institute for Colloids), Japan (National Institute of Materials Science, Tsukuba), and USA (Naval Research Laboratory, Washington DC).
His area of specialization is micro/nano technology including assembly of ultrathin organized films, bio/composites, ordered shells on tiny templates (drug capsules, shells on microbes), clay nanotubes for controlled release of anticorrosion, bioactive agents and drugs. Y. Lvov has 14 US, Australian and Japanese patents on nanoassembly. He was among pioneers of the polyelectrolyte layer-by-layer (LbL) assembly, - a method which, after his first papers in 1993, followed by many thousands publications. He also pioneered halloysite clay nanotubes for functional polymeric composites (flame-retardant, anticorrosion, antimicrobials). Y. Lvov edited 4 books, published 27 book chapters, and 235 peer reviewed papers. Lvov’s total citation index is above 17,000 which is an outstanding result, and his h-index is 70. Y. Lvov was named the Louisiana State’s Top Researcher (2007), and in 2008 he got Best of Small Tech National Innovator Award in nanotechnology. In 2015, Yuri Lvov was awarded with prestigious international Alexander von Humboldt Prize for lifetime achievements in nanochemistry. Y. Lvov is an honorable professor of Beijing University of Chemical Technology, China and Kazan Federal University, Russia.