Metal Nanoparticles of Various Shapes. Jie Gao, Min Xu Apr. 1, 2007. Outline. Advantages of metal nanoparticles. Why we need nanorods? Synthesis of metal nanoparticles. Synthesis of gold nanorods. Growth mechanism of gold nanorods. Synthesis of gold nanoparticles of different shapes.
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Jie Gao, Min Xu
Apr. 1, 2007
S. Eustis, M. A. El-Sayed, Chem. Soc. Rev.2006, 35, 209-217
1. Nanosphere lithography.
2. Templating, chemical, electrochemical, sonochemical, thermal and photochemical reduction techniques.
2. Electron beam lithography
W. Huang, W. Qian, M. A. El-Sayed, Proc. SPIT Int. Soc. Opt. Eng.2005, 5927, 592701
Turkevitch in 1951
sodium citrate + HAuCl4
General idea of chemical method: reduction + capping
C. J. Murphy, T. K. Sau, A. M. Gole, C. J. Orendorff. J. L. Gou, S. E. Hunyadi, T. Li, J. Phys. Chem. B2005, 109, 13857-13870
1. Seed size
2. Length of “tails” of CTAB (cetyltrimethylammonium bromide )
dependence of nanorod aspect ratio on seed size
Dependence of aspect ratio on length of tails of CTAB
“Zipping” fashion formation of gold nanorods
Planar density of atoms of FCC structure
crystallography picture of gold nanorods:
ΔG(10)= -29.6 kJ/mol, Δ(12)= -35.8 kJ/mol, Δ(14)= -41.9 kJ/mol,Δ(16)= -48.1 kJ/mol
Growth mechanism of gold nanorods
T. K. Sau, C. J. Murphy, J. Am. Chem. Soc.2004, 126, 8648-8649
[AA] increases from A to C and seed concentration increases from C to D. Scale bar = 100 nm
TEM images showing cubic to rod-shaped gold particles produced with low AA concentration in the presence of small quantity of silver nitrate. [CTAB] is increased (A) to (B, C, D). [Au3+] decreases from B to C, and seed concentration increased form C to D. Scale bar = 100 nm
TEM images of brached Au nanoparticles, varying in the dimension and number of branches
maximum length: ~600nm
maximum aspect ratio: ~25