special properties of nanomaterials
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Special Properties of Nanomaterials. High surface/bulk ratio. Catalysis Nanoparticle reagents Heat dissipation Laminar flow. Finite size effects. Quantum confinement Interparticle tunneling Proximity effects High probability of defect- free crystals. - PowerPoint PPT PresentationTRANSCRIPT
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Special Properties of Nanomaterials
High surface/bulk ratio• Catalysis• Nanoparticle reagents• Heat dissipation• Laminar flow
Finite size effects• Quantum confinement• Interparticle tunneling• Proximity effects• High probability of defect- free crystals
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Emission spectra of several sizes of (CdSe)ZnS core-shell quantum dots
M. Bawendi, et al., J. Phys. Chem. B 1999, 101, 9463.
Semiconductor Core-Shell Quantum Dots
• Perfect quantum well structure leads to bright luminescence• Nanocrystal size determines band gap
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CdSe/CdS core-shell particles
Excitons confined to core
Defect-free nanocrystalshigh fluorescence quantum yield
A. P. Alivisatos et al., Science 1998, 281, 2013.
Dual fluorescence labeling of actin filaments and fibroblasts
2.1 - 4.6 nm
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Cd
Se
Shape Control of Semiconductor Nanocrystals
L. Manna, E. C. Scher, A. P. Alivisatos, JACS 122, 12700 (2000)
• Nanocrystal habit controlled by surfactant composition
• Multiple injection/growth cycles develop specific crystal faces
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CdSe Tetrapods
L. Manna, E. C. Scher, A. P. Alivisatos, JACS 122, 12700 (2000)
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Conducting Polymer - Nanocrystal Solar Cells
Two-color system - can utilize solar spectrum efficiently
High aspect ratio nanocrystals, organized superstructure should minimize carrier recombination
W. U. Huynh, J. J. Dittme, A. P. Alivisatos, Science 295, 2425 (2002)
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Y. Wu, P. Yang, J. Am. Chem. Soc., 123, 3165, 2001
Vapor-liquid-solid (VLS) growth of semiconductor nanocrystals
Single crystal nanowiresCatalyst nanoparticle controls diameterLength determined by reaction time
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Compositionally Modulated Semiconductor Nanocrystals
Totem pole and core-shell structuresMultiple bandgaps and p-n junctions
Lieber, et al., Nature 415, 617 (2002); Nature 420, 57 (2002).Yang, et al., NanoLett 2, 83 (2002); Buhro et al., J. Am. Chem. Soc. 123, 4502 (2001).