Summary: The electrochemical polymerization of diphenylamine (DPA) onto electrodes of Pt coated with highly separated metallic (98%) or semiconducting (99%) single-walled carbon nanotubes (SWCNTs) in the presence of H3PW12O40 was performed by cyclic voltammetry in order to obtain composite materials based on polydiphenylamine (PDPA) doped with heteropolyanions of H3PW12O40 and carbon nanotubes. Our data demonstrate that the photoluminescence quenching effect of the PDPA doped with H3PW12O40 heteropolyanions in the presence of SWCNTs is due to the metallic component. Under UV irradiation of SWCNTs highly separated in metallic and semiconducting tubes functionalized with PDPA doped with heteropolyanions of H3PW12O40 new photochemical reactions are evidenced by photoluminescence studies. These reactions lead to a shortening of the macromolecular chain of PDPA. The photochemical process is more intense in the case semiconducting SWCNTs functionalized with PDPA doped with heteropolyanions in comparison to metallic SWCNTs functionalized with PDPA in doped state, it being a consequence of an additional chemical interaction between the DPA dimer doped with H3PW12O40 heteropolyanions and semiconducting SWCNTs.
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Summary: Arc discharge single-walled carbon nanotubes (SWCNTs) possess superlative optical and electronic properties that are of high interest for technologically important applications including fiber optic communications, biomedical imaging, and field-effect transistors. However, as-grown arc discharge SWCNTs possess a mixture of metallic and semiconducting species in addition to a wide diameter distribution (1.2 to 1.7 nm) that limit their performance in devices. While previous postsynthetic sorting efforts have achieved separation by electronic type and diameter refinement for metallic arc discharge SWCNTs, tight diameter distributions of semiconducting arc discharge SWCNTs have not yet been realized. Herein, we present two advances in density gradient ultracentrifugation that enable the isolation of high purity (>99%) semiconducting arc discharge SWCNTs with narrow diameter distributions centered at 1.6 and 1.4 nm. The resulting diameter-refined populations of semiconducting arc discharge SWCNTs possess monodisperse characteristics that are well-suited for high-performance optical and electronic technologies.
Summary: We report visible light and X-ray imagers on lightweight and mechanically flexible plastic substrates. The process involves solution processing of organic photodetectors on top of an active-matrix backplane consisting of carbon nanotube thin-film transistors. The system takes advantage of the high mobility of nanotube transistors for low operating voltages and efficient light absorption of organic bulk-heterojunctions for high imaging sensitivity. With this highly scalable process scheme, 18 × 18 pixel-array flexible imagers (physical size of 2 cm × 1.5 cm) with high performance are successfully demonstrated. In addition, as the absorption peak of the adopted organic photodiodes covers the green band of the light spectrum, X-ray imaging is readily demonstrated by placing a scintillator film on top of the flexible imagers.
Citation: G. Dinesha M. R. Dabera, K. D. G. Imalka Jayawardena, M. R. Ranga Prabhath, Iskandar Yahya, Y. Yuan Tan, N. Aamina Nismy, Hidetsugu Shiozawa, Markus Sauer, G. Ruiz-Soria, Paola Ayala, Vlad Stolojan, A. A. Damitha T. Adikaari, Peter D. Jarowski, Thomas Pichler, and S. Ravi P. Silva , ACSNano 2013, 7 (1), pp. 556-565.
Summary: Transparent, highly percolated networks of regioregular poly(3-hexylthiophene) (rr-P3HT)-wrapped semiconducting single-walled carbon nanotubes (s-SWNTs) are deposited, and the charge transfer processes of these nanohybrids are studied using spectroscopic and electrical measurements. The data disclose hole doping of s-SWNTs by the polymer, challenging the prevalent electron-doping hypothesis. Through controlled fabrication, high- to low-density nanohybrid networks are achieved, with low-density hybrid carbon nanotube networks tested as hole transport layers (HTLs) for bulk heterojunction (BHJ) organic photovoltaics (OPV). OPVs incorporating these rr-P3HT/s-SWNT networks as the HTL demonstrate the best large area (70 mm2) carbon nanotube incorporated organic solar cells to date with a power conversion efficiency of 7.6%. This signifies the strong capability of nanohybrids as an efficient hole extraction layer, and we believe that dense nanohybrid networks have the potential to replace expensive and material scarce inorganic transparent electrodes in large area electronics toward the realization of low-cost flexible electronics.
Citation: Megumi Kinoshita, Mathias Steiner, Michael Engel, Joshua P. Small, Alexander A. Green, Mark C. Hersam, Ralph Krupke, Emilio E. Mendez, Phaedon Avouris, Opt. Express (2010), 18, 25, 25738-25745.
Summary: We demonstrate a light emitting p-i-n diode made of a highly aligned film of separated (99%) semiconducting carbon nanotubes, self- assembled from solution. By using a split gate technique, we create p- and n-doped regions in the nanotube film that are separated by a micron-wide gap. We inject p- and n-type charge carriers into the device channel from opposite contacts and investigate the radiative recombination using optical micro-spectroscopy. We find that the threshold-less light generation efficiency in the intrinsic carbon nanotube film segment can be enhanced by increasing the potential drop across the junction, demonstrating the LED- principle in a carbon nanotube film for the first time. The device emits infrared light that is polarized along the long axes of the carbon nanotubes that form the aligned film.
Summary: We report photodetection in a very large spectral bandwidth, which encompasses ultraviolet, visible and near infrared, using graphene inks or graphene inks functionalized with either gold or silver nanoparticles, or gold nanoparticles further encapsulated with bovine serum albumin deposited on interdigitated electrodes fabricated on a silicon dioxide/silicon substrate. In contrast to gold-functionalized graphene inks, which have responsivities better than 1 mA W-1 at a 0.1 V bias over the huge bandwidth extending from 215 to 2500 nm, Ag-functionalized inks show at least a four-fold increased responsivity, with a record value of 13.7 mA W-1 in near infrared.
Summary: We report a comprehensive study of the gate-induced electromodulated transmittance of infrared light by single-walled carbon nanotube (SWNT) thin films. The observed electromodulation is significantly enhanced by utilizing large diameter SWNTs, increasing the ratio of semiconducting to metal SWNTs, and by decreasing the SWNT film thickness. The amplitude of the effect reported herein (∼7%) is more than an order of magnitude larger than in previous SWNT thin film solid state devices.