In the fabrication of polymeric electroluminescent devices with indium-tin oxide (ITO) as anode, indium contamination of the polymers can greatly degrade the device performance. In the present study, we have used x-ray photoelectron spectroscopy to measure indium incorporation in poly(3,4-ethylene dioxythiophene):poly(styrene sulphonate), referred to as PEDOT:PSS, which were spincast on bare ITO and encapsulated ITO. We found that the deposition of a self-assembled monolayer of alkylsiloxanes on ITO prior to spincasting PEDOT:PSS was effective and practical in blocking the reactions between ITO and PEDOT:PSS.

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By blending poly(ethylene glycol) (PEG) into an electroluminescence (EL) polymer, significantly enhanced EL efficiency in a polymer light-emitting diode (PLED) with aluminum electrode was achieved. An orange-color-emitting PLED with 10 wt % PEG blending achieved device efficiencies exceeding 2.6 cd/A for a wide range of bias voltage, which is more than two orders of magnitude higher than that of a similar PLED without the PEG blending. The enhanced efficiency was a result of the reduction of electron injection barrier height at the cathode–polymer interface. It is believed that interfacial interaction that is specific to Al plays an important role in the enhancement mechanism.

Using an iodinated bile-acid analog with hepatic uptake and transport characteristics similar to conventional bile acids, the hepatic lobular gradient concept of Goresky was studied utilizing autoradiography. 125I-labeled cholylglycylhistamine (125I-CGH) was infused into the portal veins of male Sprague-Dawley rats and the livers were fixed for light microscopic autoradiography at 1 and 5 min after infusion. In two animals, sequential samples of bile were collected to assess the transport characteristics of 125I-CGH. By 1 min, virtually all (98%) of the injected 125I-CGH was taken up and retained by hepatocytes after perfusion fixation. Less than 15% of the label was lost during subsequent tissue processing. 125I-CGH appeared in bile within minutes, reaching maximum levels at 7 min. Quantitative autoradiography demonstrated that the first six to nine periportal hepatocytes were, by far, the most active (P less than 0.0005) in sequestering the bile-acid analog than were the remaining cells in the lobule. This study, therefore, provides the first autoradiographic evidence of a hepatic lobular concentration gradient for the uptake of a bile-acid analog.

Reduced dimensionality and quantum confinement in conjugated organic and polymer structures enhance the effects of electron correlation on virtual electronic excitation processes and nonlinear-optical responses. A microscopic many-electron description of the third-order susceptibilities Yijkl(-W4; w1, 2, c3) of conjugated structures is reviewed for one-dimensional chains and extended to two-dimensional conjugated cyclic structures. Electron correlation effects in effectively reduced dimensions result in highly correlated 7-electron virtual excitations that lead to large, ultrafast nonresonant nonlinear-optical responses. The increase of dimensionality from linear to cyclic chains is found to reduce the nonresonant isotropic third-order susceptibility yg. Resonant experimental studies of saturable absorption and optical bistability in ultrathin films of quasi-two-dimensional naphthalocyanine oligomers are also presented. In the saturable-absorption studies, the resonant nonlinear refractive index n was measured to be 1 X 10-4 cm2/kW in the wavelength range of operating laser diodes. Based on this result, electronic absorptive optical bistability is observed on a nanosecond time scale in a nonlinear Fabry-Perot interferometer employing the saturably absorbing naphthalocyanine film as the nonlinear-optical medium.