Enhanced LWIR response of InP/InAsP quantum discs-in-nanowire array photodetectors by photogating and ultra-thin ITO contacts

Here we report on an experimental and theoretical investigation of the long-wavelength infrared (LWIR) photoresponse of photodetectors based on arrays of three million InP nanowires with axially embedded InAsP quantum discs. An ultra-thin top indium tin oxide contact combined with a novel photogating mechanism facilitates an improved LWIR normal incidence sensitivity in contrast to traditional planar quantum well photodetectors. The electronic structure of the quantum discs, including strain and defect-induced photogating effects, and optical transition matrix elements were calculated by an 8-bandk·psimulation along with solving drift-diffusion equations to unravel the physics behind the generation of narrow linewidth intersubband signals observed from the quantum discs.

The preparation of a new 57cobalt-labelled thyroxine for use in single/dual radioimmunoassay techniques

The preparation of L-thyroxine labelled with 57cobalt for use as a second tracer in dual radioimmunoassay techniques for different biological molecules is described. The labelling procedure was monitored by paper chromatography and polyacrylamide gel electrophoresis; a yield of 42 +/- 10% (mean +/- 1 SD) was achieved in a total of 39 conjugation reactions. The method was optimized in terms of pH, reaction completion time, reactant concentration, and solubility of the tracer. A radioimmunoassay for thyroxine in human serum was developed utilizing this tracer, and this compared favorably with an established technique in which 125iodine was used as the tracer (n = 71, r = 0.91, y = 0.988 x - 1.93).