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
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
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
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
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
CdSe Tetrapods
L. Manna, E. C. Scher, A. P. Alivisatos, JACS 122, 12700 (2000)
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)
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
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).