Electroluminescence from organic materials has the potential to enable low-cost, full-color flat-panel displays, as well as other emissive products. Some materials have now demonstrated adequate efficiencies (1 to 15 lumens/watt) and lifetimes (>5000 hours) for practical use; however, the factors that govern lifetime remain poorly understood. This article provides a brief review of device principles and applications requirements and focuses on the understanding of reliability issues.

Optical nanostructures have enabled the creation of subdiffraction detection volumes for single-molecule fluorescence microscopy. Their applicability is extended by the ability to place molecules in the confined observation volume without interfering with their biological function. Here, we demonstrate that processive DNA synthesis thousands of bases in length was carried out by individual DNA polymerase molecules immobilized in the observation volumes of zero-mode waveguides (ZMWs) in high-density arrays. Selective immobilization of polymerase to the fused silica floor of the ZMW was achieved by passivation of the metal cladding surface using polyphosphonate chemistry, producing enzyme density contrasts of glass over aluminum in excess of 400:1. Yields of single-molecule occupancies of Ϸ30% were obtained for a range of ZMW diameters (70 -100 nm). Results presented here support the application of immobilized single DNA polymerases in ZMW arrays for long-read-length DNA sequencing.fluorescence ͉ metal passivation ͉ microscopy ͉ polyvinyl phosphonic acid ͉ single molecule N anofabrication techniques have enabled new approaches to interrogate individual biomolecules by fluorescence techniques (reviewed in refs. 1 and 2). The extremely small size scale of the associated devices results in a drastic illumination volume reduction, allowing single-molecule investigations to take place at fluorophore concentrations increased to biologically relevant levels. In addition to higher temporal resolution and higher signal-to-noise ratios, they also provide spatial resolution beyond diffraction-limited optics.The zero-mode waveguide (ZMW) is one such nanophotonic confinement structure often consisting of a circular hole in a metal cladding film on a solid transparent substrate (3). In conjunction with laser-excited fluorescence, they provide observation volumes on the order of zeptoliters (10 Ϫ21 l), three to four orders of magnitude smaller than far-field excitation volumes. Applications of circular ZMWs have included the detection of single-molecule DNA polymerase activity by using labeled nucleotides at micromolar concentrations (3), the study of -repressor oligomerization dynamics (4), two-color crosscorrelation to rapidly screen for DNA restriction enzyme activity (5), and diffusion analysis of labeled membrane proteins in lipid bilayers of model membranes and living cells (6-11). C-shaped apertures have been described to study DNA hybridization interactions (12).ZMW technology applications have been limited by the unavailability of selective immobilization methods to position molecules exclusively in the observation volume, immediately above the transparent ZMW floor. One approach to selective immobilization exploits a feature inherent in the ZMW architecture. The transparent substrate and metal cladding are made of different materials, opening the possibility for a selective derivatization that will direct protein adsorption to the floor and not to the nearby metal walls. The nanometer size scale and three-dimensional n...

A theory is presented for the lateral surface free energy parameter a in the nucleation constant Kt in the relation G exp[~KtIT(AT)f] that describes the growth rate of polymer crystals from the melt at low-to-moderate undercoolings AT. The theory forms a connection between nucleation theory and the statistics of polymer chain dimensions and provides a new approach to the determination of the characteristic ratio C". It is predicted that varies as const x C.*1, where the constant involves known quantities. The effect of chain structure resides principally in C". The theory was tested for polyethylene, isotactic polystyrene, and poly(L-lactic acid) by employing known values of obtained from melt crystallization studies to calculate C. and then comparing these with the C" values cited in the literature as determined from chain dimensions in dilute solvents. The agreement is satisfactory, showing the theory for to be valid in these cases, with the further implication that these polymers possessed a close approximation to unperturbed chain dimensions in the melt. Support was provided by data for isotactic polypropylene, poly(pivalolactone), and polyO caprolactone), some of this deriving from a method of finding C" for the melt state without direct reference to a. The CVdependent "segmental" character induced by the crystal surface in the section of chain comprising the activated complex is discussed. The theory for provides strong support for polymer nucleation theory as there is now a predictive molecular picture for all the nucleation parameters in Ke. The treatment casts new light on the empirical formulas commonly employed to estimate .

Carbon nanotubes (CNTs), with their exceptional electrical properties, chemical stability, and mechanical strength, have attracted a great deal of attention. This makes the material attractive for a wide range of applications, including composite materials, 1 battery electrode materials, 2 nanoelectronics, 3,4 and nanoscale sensors. 5 However, the properties of CNTs are highly dependent on their structure and size. Such sensitivity to size and structure imposes a potential barrier to the realization of the novel properties of CNTs in many applications. In the growth of CNTs by chemical vapor deposition (CVD), the diameters of CNTs are determined by the sizes of catalysts. 6 One way to obtain CNTs with fewer chiral arrangements is to use smaller catalyst particles. Thus, CNTs with smaller diameters, for example less than 2 nm, are most likely to be single-walled with fewer geometrical arrangements. This should limit the band gap range and allow the possibility of having all metallic or all semiconducting CNTs from a given growth. Moreover, such small-diameter nanotubes have larger band gaps, which minimize off-state leakage, thereby increasing the transistor on/off current ratio in transistor applications. 7 Significant progress has been made in driving catalyst size, and thus nanotube diameters, down