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Flexible Nanotube Networks

Using single-wall carbon nanotubes (SWCNTs) that have been purified by length and/or electronic type (metallic or semiconducting), we are assembling thin flexible nanotube films on soft polymer substrates and characterizing the coupling between mechanical flexibility and electronic performance. Metallic SWCNTs are of interest as a potential replacement for ITO in flexible electronics applications, while semiconducting SWCNTs are being explored as scaffolds for flexible photovoltaic devices. Layered SWCNT-polymer nanocomposite films show particular promise as stable transparent conductive coatings. Collaborators on this project include the National Institute of Standards and Technology (NIST) and the University of Minnesota.

Self-Assembly and Photoluminescent Stability of Silicon Nanocrystals

In this work, we are purifying silicon nanocrystals (quantum dots) in an effort to reduce size polydispersity to the point where super-lattice assembly becomes viable over large (macroscopic) length scales. Density-gradient ultracentrifugation in layered organic solvents is used to produce monodisperse nanocrystal fractions, which we then assemble into closed-packed clusters, crystals and films using a variety of fluid-based approaches. The photoluminescent stability of individual dots and clusters of varying size and packing symmetry is then characterized under varied environmental conditions. Applications of interest include non-toxic tagging for biomedical imaging and photostable, environmentally responsive luminescent coatings. Our collaborators are at the University of Minnesota.

Transmembrane Nanoparticle Transport

In collaboration with Andriy Voronov in the Department of Coatings and Polymeric Materials, we are using fluorescent imaging and microscale time-resolved spectroscopy to measure the specific cellular uptake mechanisms of PEGylated nanoparticles, quantum dots, and cargo carrying copolymer micelles. The biological systems we study are as simple as giant unilamellar phospholipid vesicles (GUVs) and as complex as living cells. Applications of interest include drug delivery, nanotoxicity, and fluorescent tagging.

High Performance Polymer Nanocomposites

An area of immediate interest is the engineering of polymer-nanoparticle blends for applications in coatings, sensors and devices. By mixing silicon nanocrystals (SiNCs) with different polymers, for example, we can make photoluminescent coatings with optical sensitivity to changes in temperature, stress or chemical environment. We are also interested in how the phase behavior of these colloid-polymer mixtures ultimately impacts the performance of the final composite materials. Our collaborators on this project are Alan Denton and Alexander Wagner in the Physics Department at NDSU, and semiconductor nanocrystal researchers in the Center for Nanoscale Science and Engineering (CNSE) at NDSU and at the University of Minnesota.

Fluid Processing Routes to Silicon Electronics

In collaboration with the Center for Nanoscale Science and Engineering (CNSE) at NDSU, we are exploring the use of silicon polymer inks (liquid silanes) as a novel way to engineer new electronic devices and materials. Of particular interest is the spray coating and roll-to-roll manufacturing of electronics-grade silicon on flexible substrates such as Kapton, metal foils and PDMS.

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