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Synthesis of hcp-Co nanodisks

Description: hcp Co disk-shaped nanocrystals were obtained by rapid decomposition of cobalt carbonyl in presence of linear amines. Other surfactants, in addition to the amines, like phosphine oxides and oleic acid were used to improve size dispersion, shape control and nanocrystal stability. Co disks are ferromagnetic in character and they spontaneously self-assemble into long ribbons. X-ray and electron diffraction, electron microscopy and SQUID magnetometry have been employed to characterize this material.
Date: June 11, 2002
Creator: Puntes, Victor F.; Zanchet, Daniela; Erdonmez, Can K. & Alivisatos, A.P.
Partner: UNT Libraries Government Documents Department

Sorting fluorescent nanocrystals with DNA

Description: Semiconductor nanocrystals with narrow and tunable fluorescence are covalently linked to oligonucleotides. These biocompounds retain the properties of both nanocrystals and DNA. Therefore, different sequences of DNA can be coded with nanocrystals and still preserve their ability to hybridize to their complements. We report the case where four different sequences of DNA are linked to four nanocrystal samples having different colors of emission in the range of 530-640 nm. When the DNA-nanocrystal conjugates are mixed together, it is possible to sort each type of nanoparticle using hybridization on a defined micrometer -size surface containing the complementary oligonucleotide. Detection of sorting requires only a single excitation source and an epifluorescence microscope. The possibility of directing fluorescent nanocrystals towards specific biological targets and detecting them, combined with their superior photo-stability compared to organic dyes, opens the way to improved biolabeling experiments, such as gene mapping on a nanometer scale or multicolor microarray analysis.
Date: December 10, 2001
Creator: Gerion, Daniele; Parak, Wolfgang J.; Williams, Shara C.; Zanchet, Daniela; Micheel, Christine M. & Alivisatos, A. Paul
Partner: UNT Libraries Government Documents Department

Conjugation of DNA to Silanized Colloidal Semiconductor Nanocrystalline Quantum Dots

Description: Water-soluble, highly fluorescent, silanized semiconductor nanocrystals with different surface charges were synthesized. To covalently attach the nanocrystals to biological macromolecules with a variety of mild coupling chemistries, the outermost siloxane shells were derivatized with thiol, amino, or carboxyl functional groups. Single- or double-stranded DNA was coupled to the nanocrystal surfaces by using commercially available bifunctional cross-linker. Conjugation had little effect on the optical properties of the nanocrystals, and the resulting conjugates were more stable than previously reported systems. By using the strategies developed in this study, most biomolecules can be covalently coupled to semiconductor nanocrystals. These nanocrystal-DNA conjugates promise to be a versatile tool for fluorescence imaging and probing of biological systems.
Date: September 10, 2001
Creator: Parak, Wolfgang J.; Gerion, Daniele; Zanchet, Daniela; Waerz, Anke S.; Micheel, Christine; Williams, Shara C. et al.
Partner: UNT Libraries Government Documents Department