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Solid-state light-emitting devices (LEDs) were fabricated based on an amorphous film of Ru(bpy) 3 (ClO 4 ) 2 (bpy ) 2,2′-bipyridine) about 100 nm thick on indium-tin oxide (ITO) with printed low melting point alloys, such as Ga:In, Ga:Sn, and Bi:In:Pb:Sn, as cathodic contacts. A device with the structure of ITO (e10 Ω/square)/Ru(bpy) 3 (ClO 4 ) 2 /Ga:Sn produces a bright red emission (3500 cd/m 2 at 4.0 V) centered at 660 nm. This new method of making contacts significantly simplifies the fabrication of an electroluminescence cell and has potential application in the production of LEDs by inkjet or microcontact printing. LEDs based on C 12 -Ru(bpy) 3 (ClO 4 ) 2 , Ru(phenanthroline) 3 (ClO 4 ) 2 , and Os(bpy) 3 (PF 6 ) 2 were also studied. Low melting point alloy contacts were also used with cells based on tris(8-hydroxyquinoline)aluminum.Organic solid-state light-emitting devices (OLEDs) may eventually offer an alternative to inorganic semiconductor (e.g., GaAs) light-emitting diodes and liquid crystal displays, perhaps affording flatter, brighter, and more flexible displays at lower cost. [1][2][3][4][5] There has been a great deal of research aimed at the development of new light-emitting materials. [6][7][8][9][10][11][12][13][14][15][16][17][18][19] Among the materials that have been studied, polymers based on trischelated ruthenium(II) complexes have recently attracted considerable attention. [20][21][22][23][24][25][26] Attempts have been made to increase the duration of operation and to improve the performance of light-emitting materials with dopant in the emitters, [27][28][29][30] dopant in the hole-transport materials, [31][32][33][34] electron-transport materials, 35,36 transparent

For long-term growth of mammalian cells in perfused bioreactors, it is essential to monitor the concentration of dissolved oxygen (DO) present in the culture medium to ascertain the health of the cells. An optical oxygen sensor based on dynamic fluorescent quenching was developed for long-term continuous measurement of DO for NASA-designed rotating perfused bioreactors. Tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) chloride is employed as the fluorescent dye indicator. A pulsed, blue LED was chosen as the excitation light source. The sensor can be sterilized using an autoclave. The sensors were tested in a perfused rotating bioreactor supporting a BHK-21 (baby hamster kidney) cell culture over one 28-day, one 43-day, and one 180-day cell runs. The sensors were initially calibrated in sterile phosphate-buffered saline (PBS) against a blood-gas analyzer (BGA), and then used continuously during the entire cell culture without recalibration. In the 180-day cell run, two oxygen sensors were employed; one interfaced at the outlet of the bioreactor and the other at the inlet of the bioreactor. The DO concentrations determined by both sensors were compared with those sampled and measured regularly with the BGA reference. The sensor outputs were found to correlate well with the BGA data throughout the experiment using a single calibration, where the DO of the culture medium varied between 25 and 60 mm Hg at the bioreactor outlet and 80-116 mm Hg at the bioreactor inlet. During all 180 days of culture, the precision and the bias were +/-5.1 mm Hg and -3.8 mm Hg at the bioreactor outlet, and +/- 19 mm Hg and -18 mm Hg at inlet. The sensor dynamic range is between 0 and 200 mm Hg and the response time is less than 1 minute. The resolution of the sensor is 0.1 mm Hg at 50 mm Hg, and 0.25 mm Hg at 130 mm Hg.