Crystalline 4.6 nm HgTe quantum dots, stabilized by 1-thioglycerol ligands, were synthesized by wet chemical methods. Room-temperature photoluminescencespectra of the dots, both in solution and as solid arrays, exhibited near-infrared emission. Light-emitting devices were fabricated by deposition of quantum dot layers onto glass∕indium tin oxide (ITO)∕3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates followed by top contacting with evaporated aluminum. Room-temperature near-infraredelectroluminescence from 1mm2 ITO∕PEDOT∕HgTe∕Al devices, centered at ∼1600nm, with an external quantum efficiency of 0.02% and brightness of 150nW/mm2 at 50 mA and 2.5 V was achieved

One-dimensional (1D) nanostructures based on organic materials are attracting significant research interest owing to the many novel chemical, physical, and electronic properties that may arise in such systems and the possibility of exploiting these properties in a variety of applications. [1,2] In particular, the potential of semiconducting polymer nanowires has already been explored for initial demonstration of nanoscale electronic and photonic devices such as field-effect transistors, [3] field emitters, [4] and sub-wavelength active waveguides, [5] optically pumped lasers, [6] photodetectors [7] and electroluminescent diodes. [8] However, for 1D nanostructures in general, a key challenge is the development of new approaches that will permit controlled anisotropic alignment of nanowires and nanotubes and, preferably, also enable dynamic manipulation of their orientation in real time.In this regard, nematic liquid crystal (LC) materials have long been employed as anisotropic solvents for orientation of non-spherical guests. They are excellent hosts for spectroscopic studies both of the anisotropy of the optical and electronic properties of aligned guest molecules, [9] and of the nature of energy and charge-transfer processes occurring within guests.[10] The anisotropic optical properties of oriented guests may also be combined with the dynamic switchabilty of LCs to realize reconfigurable photonic devices. Electric field switching of the alignment of small organic molecules in LC hosts was proposed as far back as 1968 and 1973 for realization of single layer pleochroic colored [11] and fluorescent [12] displays, respectively. More recently, nematic LCs have been employed to demonstrate optical absorption and photoluminescence (PL) dichroism in oligothiophene [13,14] and poly(phenylene vinylene)-type [15,16] guests. By electric field assisted reorientation of the oligothiophenes in particular, a switchable polarized PL contrast was achieved. [13,14] Alignment of carbon nanotubes in nematic LC hosts has also permitted optical transmission modulation by electric field switching [17] and electrical conductance modulation by either electric [18] or magnetic [19] field switching.In this Communication, we demonstrate the alignment and dynamic manipulation of novel conjugated polymer nanowires in a nematic LC host. A low-molecular-weight, room temperature nematic LC material, E7, is employed as the host matrix. The guest nanowires are composed of poly(9,9-dioctylfluorenyl-2,7-diyl), PFO, a highly efficient blueemitting, semiconducting polymer with good thermal and oxidative stability, and are synthesized using a template method.[20] Initial single wire optical spectroscopic studies yield well-resolved PL spectra characteristic of PFO b-phase, in which polymer chain segments adopt a planarized and extended conformation. Importantly, nanowire PL emission is also found to be axially polarized, consistent with internal alignment of b-phase strands during synthesis. Incorporation of nanowires into the E7 host results in stro...

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Polyfluorene nanotubes are synthesized by solution assisted wetting of porous anodic alumina membranes. Well aligned arrays of close packed (∼109 tubes/cm−2) discrete nanotubes are obtained. Individual tubes have diameters of ∼260 nm and wall thicknesses of ∼50 nm. X-ray diffraction measurements carried out on nanotube arrays embedded in host templates indicate a polymer chain alignment along the long axes of the template pores and, as a result, along the long axes of the nanotubes themselves. Optical spectroscopic studies of mats of nanotubes on glass substrates yield well resolved emission spectra reflecting a narrowed distribution of emitting chain segments with increased effective conjugation lengths. The data indicate intrachain reorientation of the amorphous random poly(9,9-dioctylfluorene-2,7-diyl) molecular conformation to the more planar (low energy) extended 21 helical β-phase conformation within the tubes. Raman spectra acquired for template embedded tubes are also consistent with β-phase formation. Finally, polarization resolved photoluminescence data demonstrate a pronounced axial orientation of the emissive β-phase chains within the tubes.

Narrow bandwidth red electroluminescence from OLED devices fabricated using a simple solution-based approach is demonstrated. A spin-casting method is employed to fabricate organic light emitting diode (OLED) devices comprising a poly(N-vinylcarbazole) (PVK) host matrix doped with a europium h-diketonate complex, Eu(dbm) 3 (Phen) (dibenzoylmethanate, dbm; 1,10-phenanthroline, Phen) on glass/ indium tin oxide (ITO)/3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates. Saturated red europium ion emission, based on the 5 D 0 Y 7 F 2 transition, is centered at a wavelength of 612 nm with a full width at half maximum of 3.5 nm. A maximum external quantum efficiency of 6.3 Â 10 À 2 cd/A (3.1 Â10 À 2 %) and a maximum luminance of 130 cd/m 2 at 400 mA/cm 2 and 25 V is measured for ITO/PEDOT/PVK:Eu(dbm) 3 (Phen)/Ca/Al devices. This measured output luminance is comparable to that of devices fabricated using more sophisticated small molecule evaporation techniques.