1. Basic Science of Nanomaterials (Ch. 11)
High surface/bulk ratio
Catalysis
Reactivity
Melting point
Vapor pressure
Ostwald ripening
Finite size effects
Quantum confinement
High probability of defect-
free crystals
Mesoscopic phenomena

2. Semiconductor nanocrystal synthesis
High temperature, non-aqueous solvents
Separate nucleation and growth steps
Size focusing during crystal growth
Capped nanocrystals have few or no defects

3. Semiconductor Core-Shell Quantum Dots
Perfect quantum well structure leads to bright luminescence
Nanocrystal size determines band gap
Emission spectra of several sizes of
(CdSe)ZnS core-shell quantum dots
M. Bawendi, et al., J. Phys. Chem. B 1999, 101, 9463.

4. CdSe/CdS core-shell particles Excitons confined to corenm
CdSe/CdS core-shell particles
Excitons confined to core
Defect-free nanocrystals
high fluorescence quantum yield
Dual fluorescence labeling of actin filaments and fibroblasts
A. P. Alivisatos et al., Science 1998, 281, 2013.

5. Shape Control of Semiconductor Nanocrystals
Nanocrystal habit controlled
by surfactant composition
Multiple injection/growth cycles
develop specific crystal faces Cd Se
L. Manna, E. C. Scher, A. P. Alivisatos, JACS 122, (2000)

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

7. Vapor-liquid-solid (VLS) growth of semiconductor nanocrystals
Single crystal nanowires
Catalyst nanoparticle controls diameter
Length determined by reaction time
Y. Wu, P. Yang, J. Am. Chem. Soc., 123, 3165, 2001

8. Compositionally Modulated Semiconductor Nanocrystals
Totem pole and core-shell structures
Multiple 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).

9. Surface energy and physical/chemical properties
Surface atoms have
higher energy than bulk atoms
(dangling bonds)
How does nanocrystal size affect:
Melting point ?
Vapor pressure ?
Chemical reactivity ?

10. Ag nanocrystal melting point
Nanoparticle melting
Ag nanocrystal melting point
S. A. Little et al., Appl. Phys. Lett , 100,