Nano Focus: IR lasers enable direct patterning on conjugated polymers
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ocus IR lasers enable direct patterning on conjugated polymers
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versatile and simple new technique for patterning submicrometer features in a conjugated polymer using an infrared laser is described in the August 10 issue of Nano Letters (DOI: 10.1021/ nl2011593; p. 3128). While the potential for low-cost processing is a key advantage of using organic semiconductor materials in the place of conventional silicon electronics, many patterning techniques used at present such as contact printing and dip-pen lithography are either timeconsuming or expensive. In their recent article, R. Kaner from the University of California–Los Angeles, G. Wallace of the University of Wollongong, Australia, and co-workers demonstrate how a laser in a commercial disk drive can be used to write features with tunable conductivity onto polyaniline-coated discs. The team made use of a commercially available program normally used to create images on a compact disc, by activating a dye coating with a 788 nm laser. By replacing this coating with the well-known conductive polymer polyaniline, features could instead be written
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VOLUME 36 • OCTOBER 2011
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ferent positions to a sample macromolecule, such as a strand of DNA or RNA, or a protein or peptide. The sample macromolecule would then be exposed to light and the optical responses of the 3D plasmon rulers would be measured through dark-field microspectroscopy. “The realization of 3D plasmon rulers using nanoparticles and biochemical linkers is challenging, but 3D nanoparticle assemblies with the requisite symmetries and configurations have already been demonstrated,” Liu said. “We believe that these exciting experimental achievements and the introduction of our new concept will pave the road toward the realization of 3D plasmon rulers in biological and other soft-matter systems.”
into the polymer by thermally inducing cross-linking at the irradiated regions. The high photothermal conversion efficiency and poor thermal conductivity of polyaniline allows the laser to induce highly localized melting of the polymer fibers into visibly welded regions as thin as A scanning electron micrograph of a polyaniline film with lines of 1 μm. Chemical cross-linked polymer formed by an infrared laser. Reproduced with cross-linking bepermission from Nano Lett. (DOI: 10.1021/nl2011593; p. 3128). © 2011 American Chemical Society. tween neighboring fibers is proposed to occur through the formation of heterocycles containwere rendered electrically insulating by ing two nitrogen atoms from adjacent the cross-linking, but as the intensity was chains, and the accompanying rearlowered, a range of intermediate resisrangement of carbon double bonds can tances from insulating to metallic could be clearly observed by the change in be achieved. Corresponding changes in infrared spectra. the emission spectrum and reflectivity The program’s facility for creating of the polymer film also allowed the grayscale images by varying the intensiteam to create high-resolution color imty of the laser could als
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