Synopsis:

Is it possible to collect an ensemble of nanoparticles and to engender strong enough particle-particle interactions among them to give rise to macroscopic adhesion among the particles?  In other words, can one make a macroscopic, centimeter-sized structure of nanoparticles without the presence of a glue, scaffold, or cross-linker to maintain adhesion among the nano-constituents?  My group addresses this question by fabricating freestanding, self-supporting films of nanoparticles that are comprised solely of colloidally synthesized nanoparticles.  Thus, no binding agents or mediators are present to maintain the integrity or strength of the film.

Major Achievements:

Freestanding, all-nanoparticle films without the use of glues, binding agents, or scaffolds.  This research is the subject of a patent application.

Publicity:

This research was featured in Small Times, Semiconductor International, Science Daily, Nanotechnology Now, The Science Blog, and Vanderbilt Explorations

Detailed Discussion:

One of the challenges to implement nanoparticles (NPs) and nanoparticle films into device applications is incorporating the films into systems (circuitry architectures, substrate configurations, etc.) that exploit their properties.  The term nanoparticle refers collectively to a variety of nanoscale objects, including nanocrystals (NCs) and anisotropic nanoscale objects (such as nanotubes). Our approach is to develop a versatile nanoparticulate casting system, which creates freestanding, macroscopic films comprised exclusively of nanoparticles that are free of an underlying substrate.  Nanoparticulate films can be produced in a rapid, repeatable format for applications like chemical sensors and flexible video displays.  This research may be the first step toward new low-cost processes for the on-demand fabrication of nanoparticle films due to the shorter cycle time of EPD relative to other methods.  We rely on strong particle-particle interactions, primarily from van der Waals, dipole-dipole, steric, and Coulomb forces, because of the small inter-nanoparticle separation engendered by EPD, to maintain the structural integrity of the films before, during, and after liberation from the underlying substrate.

Reference Articles:

a. Jyotishka Biswas, Jaron Rottman-Yang, Isabel Gonzalo-Juan, and James H. Dickerson, Freestanding Carbon Nanotube Films Fabricated By Post-Electrophoretic Deposition Electrochemical Separation,Journal of the Electrochemical Society 159, K103, 2012.

b. S.A. Hasan, D.W. Kavich, and J.H. Dickerson, Sacrificial layer electrophoretic deposition of free-standing multilayered nanoparticle films, Chemical Communications 25, 3723, 2009.

c. S.A. Hasan, S.V. Mahajan, D. W. Kavich, and J. H. Dickerson, Electrophoretic Deposition of CdSe Nanocrystal Films Onto Dielectric Polymer Thin Films, Thin Solid Films, 517, 2665-2669, 2009.