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4 November 2002 Long-wavelength-emitting nanocrystals for bioassay applications
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New fluorophores that can be excited using visible or near-infrared radiation are of considerable interest for application in environmental and complex bioassays, where background fluorescence is exacerbated by ultra-violet or blue excitation. Useful labels for biomolecules include infrared emitting semiconductor nanoparticles that can be blue-shifted into the near-infrared and visible through quantum confinement effects, oxides of iron, and rare earth oxides. In this work, the synthesis of 6 nm average diameter lead selenide nanocrystals (well below the Bohr exciton diameter of 92 nm) through a reverse micelle technique; and the synthesis of iron and europium oxides with particles less than 5 nm in diameter by pulsed laser ablation is reported. The europium oxide nanoparticles' emission showed a large Stokes shift (144 nm or 216 nm, depending on excitation wavelength); a narrow, symmetric emission line at 610 nm (FWHM of 8 nm); and long lifetime (300 μs). The Eu2O3 nanoparticles, which were coated with silica for functionalization, displayed a greatly enhanced sensitivity over a conventional ELISA (0.025 ng ml-1 vs. 0.1 ng ml-1) when run in an atrazine immunoassay.
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Valerie J. Leppert, Ashley S. Harvey, Geoff D. McCool, Forest T. Quinlan, Jun Feng, Guomin Shan, Pieter Stroeve, Subhash H. Risbud, Bruce D. Hammock, and Ian M. Kennedy "Long-wavelength-emitting nanocrystals for bioassay applications", Proc. SPIE 4809, Nanoscale Optics and Applications, (4 November 2002);

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