Nicholas Kotov Ph.D.
||Department / Business Unit
|University of Michigan
||State / Provence
Nanotechnology, composites, thin films, tissue engineering, self organization of nanocolloids, and atomic force microscopy
The primary research objectives of our group are the preparation and functional assessment of nanocomposites with special emphasis on:
- Ultra Strong Materials
- The Layer-By-Layer Assembly
- Self-Organization of Nanocolloids
- Nanostructured Substrates for Stimulating of Neural
- Growth and Coupling
The Layer-By-Layer Assembly
This technique of preparation of thin films is taken advantage of in many projects which are being pursued in our group. The idea of the technique is very simple. A charged substrate, for instance negatively charged glass, is immersed in the solution of positively charged polyelectrolyte. After rinsing with water, the latter forms a submonolayer on the surface of the substrate, which switches the surface charge to positive. When one immerse it in the dispersion of negatively charged nanoparticles or other nanocolloid, a new layer is formed, which also switches the surface charge. This makes possible the adsorption of a new layer of polyelectrolyte. Thus, the whole cycle can be repeated as many times as one wants. Additionally, we chemical nature of the polyelectrolyte and/or the nanocolloid can be varied as films are being assembled. This opens the way of preparation of most diverse and flexible family of nanocomposites with a variety of functionalities. For instance, the nanoparticles can be semiconducting, metallic, or magnetic. We also demonstrated the assembly of clay sheets and carbon nanotubes. To add biological functionality to the multilayer, layers of proteins or other biopolymers can be added. Thus, LBL assembly can be considered as a very convenient tool for making both coatings and free-standing materials for a variety of most challenging applications.
Self-Organization of Nanocolloids
Recently, we learned that nanoparticles have an interesting ability to self-organize in linear structures. It was attributed to the presence of dipole-dipole interactions in the nanocolloids. Similar processes have also been observed in other systems. In the course of this work, we are uncovering fundamental interactions of nanoparticles and very unusual geometries o of self-organized superstructures from semiconductor colloids.
Ultra Strong Materials
The mechanical failure of hybrid materials made from polymers and single wall carbon nanotubes (SWNT) is primarily attributed to poor matrix-SWNT connectivity and severe phase segregation. Both problems can be successfully mitigated when the SWNTcomposite is made following the protocol of layer-by-layer assembly. This deposition technique prevents phase segregation of the polymer/SWNT binary system, and after subsequent cross-linking, the nm-scale-uniform composite with SWNT loading as high as 50 wt% can be obtained. The free-standing SWNT/polyelectrolyte membranes delaminated from the substrate were found to be exceptionally strong with tensile strength approaches that of hard ceramics. Considering the light-weight nature of SWNT composites the prepared free-standing membranes can serve as unique components for a variety of long-life-time devices.
Nanostructured Substrates for Stimulating of Neural Growth and Coupling
SWNT are not only strong but are electrically conductive. LBL assembly of composites from SWNT lends itself for the preparation of biomaterials for neural support that can be used to guide the growth of these cells. The electrical conductivity of the composites can be used to stimulate the neurons or to monitor their activity. The exceptional strength of the free-standing LBL films from SWNT is also very convenient here because it makes possible implantation of these conduits in moving parts body (almost everything).
More information at http://www.engin.umich.edu/dept/che/research/kotov
Ph.D. Moscow State University, Chemistry 1990; M.S. Moscow State University Chemistry 1987
Junior Faculty Award for Scholarly Excellence (Oklahoma State U.), 2001; NSF CAREER, 1998; Humboldt Fellow (Germany), 1997-1999
Zwitterionic Acceptor Moieties: Small Reorganization Energy and Unique Stabilization of Charge Transfer Products, 2003; Luminenscence Nanoparticle Labeled Antibodies And Antigens, 2003; Ordered Layered Assemblies of Nanoparticles, 2001; Nanorainbows: Graded Semiconductor Films From Quantum Dots, 2001