Epitaxial growth of DNA-assembled nanoparticle superlattices on patterned substrates.

DNA-functionalized nanoparticles, including plasmonic nanoparticles, can be assembled into a wide range of crystalline arrays via synthetically programmable DNA hybridization interactions. Here we demonstrate that such assemblies can be grown epitaxially on lithographically patterned templates, eliminating grain boundaries and enabling fine control over orientation and size of assemblies up to thousands of square micrometers. We also demonstrate that this epitaxial growth allows for orientational control, systematic introduction of strain, and designed defects, which extend the range of structures that can be made using superlattice assembly. Ultimately, this will open the door to integrating self-assembled plasmonic nanoparticle materials into on-chip optical or optoelectronic platforms.

Strong and stable doping of carbon nanotubes and graphene by MoOx for transparent electrodes.

MoO(x) has been used for organic semiconductor doping, but it had been considered an inefficient and/or unstable dopant. We report that MoO(x) can strongly and stably dope carbon nanotubes and graphene. Thermally annealed MoO(x)-CNT composites can form durable thin film electrodes with sheet resistances of 100 Ω/sq at 85% transmittance plain and 85 Ω/sq at 83% transmittance with a PEDOT:PSS adlayer. Sheet resistances change less than 10% over 20 days in ambient and less than 2% with overnight heating to 300 °C in air. The MoO(x) can be easily deposited either by thermal evaporation or from solution-based precursors. Excellent stability coupled with high conductivity makes MoO(x)-CNT composites extremely attractive candidates for practical transparent electrodes.

Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes.

Transparent, elastic conductors are essential components of electronic and optoelectronic devices that facilitate human interaction and biofeedback, such as interactive electronics, implantable medical devices and robotic systems with human-like sensing capabilities. The availability of conducting thin films with these properties could lead to the development of skin-like sensors that stretch reversibly, sense pressure (not just touch), bend into hairpin turns, integrate with collapsible, stretchable and mechanically robust displays and solar cells, and also wrap around non-planar and biological surfaces such as skin and organs, without wrinkling. We report transparent, conducting spray-deposited films of single-walled carbon nanotubes that can be rendered stretchable by applying strain along each axis, and then releasing this strain. This process produces spring-like structures in the nanotubes that accommodate strains of up to 150% and demonstrate conductivities as high as 2,200 S cm(-1) in the stretched state. We also use the nanotube films as electrodes in arrays of transparent, stretchable capacitors, which behave as pressure and strain sensors.

Driving high-performance n- and p-type organic transistors with carbon nanotube/conjugated polymer composite electrodes patterned directly from solution.

We report patterned deposition of carbon nanotube/conjugated polymer composites from solution with high nanotube densities and excellent feature resolution. Such composites are suited for use as electrodes in high-performance transistors of pentacene and C(60), with bottom-contact mobilities of > 0.5 and > 1 cm(2) V(−1) s(−1), respectively. This represents a clear step towards development of inexpensive, high-performance all-organic circuits.

Polymer-assisted direct deposition of uniform carbon nanotube bundle networks for high performance transparent electrodes.

Flexible transparent electrodes are crucial for touch screen, flat panel display, and solar cell technologies. While carbon nanotube network electrodes show promise, characteristically poor dispersion properties have limited their practicality. We report that addition of small amounts of conjugated polymer to nanotube dispersions enables straightforward fabrication of uniform network electrodes by spin-coating and simultaneous tuning of parameters such as bundle size and density. After treatment in thionyl chloride, electrodes have sheet resistances competitive with other reported carbon nanotube based transparent electrodes to date.