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By conjugating antibodies on magnetic nanoparticles, target antigens can be quantitatively detected by measuring the magnetic signals of the magnetic nanoparticles due to their association with target antigens. This method of detection is called magnetically labeled immunoassay. The assay characteristics of magnetically labeled immunoassay have been reported widely. However, the immuno-reaction kinetics of magnetically labeled immunoassay has not been studied. In this work, the reaction rates between magnetic nanoparticles and target antigens are measured at various temperatures. It is found that the temperature dependent reaction rate obeys Arrhenius's equation, which shows the collision frequency and activation energy for the immuno-reaction between antibody-functionalized magnetic nanoparticles and target antigens. The carcinoembryonic antigen, which is a regular blood bio-marker for in-vitro diagnosis of colorectal cancer, is used as a target antigen for the example. [ABSTRACT FROM AUTHOR]

Contact effects between solution processed conducting polymer electrodes with semiconducting polymers in field effect transistors are investigated. Limited conductivity of polymer electrodes and interfacial doping of the active semiconducting polymer by the conducting polymer electrode are found to be two important factors in determining the performance of polymer field effect transistors with printed conducting polymer electrodes. [ABSTRACT FROM AUTHOR]

Stimulated emission at bandgap energy of 1.1 eV was observed in a silicon nanostructured pn junction diode using current injection at room temperature. Nonuniform diffusion using spin-on boron dopant mixed with silicon dioxide nanoparticles was used to fabricate the device. The spatial confinement of carriers through such localization structures contributes to the enhancement of the stimulated emission. The experimental results show a drastic increase in the optical power and multiple spectral peaks at wavelengths longer than the main peak of spontaneous emission through various phonon-assisted radiative recombination processes. When the injection current significantly exceeds a threshold, a single peak dominates, exhibiting stimulated emission. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]