No Reducing Agent Needed

"Spontaneous Reduction of Metal Ions on the Sidewalls of Carbon Nanotubes"
Choi, H. C.; Shim, M.; Bansaruntip, S.; Dai, H. J. Am. Chem. Soc. 2002, 124, 9058-9059.
10.1021/ja026824t

Point:
Direct redox reactions between metal ions and nanotubes.

Materials: Au-SWNT, Pt-SWNT

Synthesis:
SWNT grown on SiO2 substrates (from CVD) was immersed in 5mM salt solutions (in 1:1 water:ethanol) for "varying periods of time".

Characterization:

AFM:

• Au particles from HAuCl4
• formed "selectively" on SWNTs, not on SiO2 substrates
• formed within 30 s of immersion (7 nm)
• increased in sizes (up to 16 nm) when increasing immersion time, but did not increase coverage density, indicating fast (<30s)>
• similar for in the dark, under room light, halogen lamp and UV light
• same for Pd particles from Na2PtCl4
• deposition from Ag+, Ni2+, Cu2+ were not "selective" - found particles on substrates.

Device-level conductance monitoring:

• hole injection from metal ions to SWNTs should induce the increase of conductance
• huge conductance improvement (from 100 nA to 700 nA) upon the immersion of device in the metal ion solution, and reach plateau in ~40 s

Speculated Applications:

• Sensors
• Catalysts
• Forming metal wires by removing carbon template