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

Dense Decorate of sub-5nm Au NPs

"Formation of gold nanoparticles supported on carbon nanotubes by using an electroless plating method"

Ma, X.; Lun, N.; Wen, S. Diam. Relat. Mater. 2005, 14, 68-73.
doi:10.1016/j.diamond.2004.07.002

Points:
"Electroless plating with gold on CNTs cannot be succeeded without any activation of the surfaces."


"Pd/Sn catalyticnuclei in a Sn colloidal layer were first introduced onto the surfaces of the oxidized CNTs; after being washed with HCland distilled water, the Sn protective layer was preferentially dissolved and the Pd catalytic nuclei were exposed to agreater extent. In the following step of electroless plating,the individual Pd catalytic centers deposited on the surface of CNTs would reduce gold ions to neutral gold atoms and formed homogeneous dispersed and high-density nucleation centers of gold islands."

Materials: Au-MWNT

Synthesis:
Electroless Plating:

• KBH4 as the active reducing agent.
• MWNT (CVD from acetylene, H2SO4/HNO3, 140 C, 6h) was sonicated in activation solution (SnCl2/PdCl2/HCl, detailed preparation described), washed with 1M HCl/water repeatedly, and stirred in the plating bath for ~15 min at 25C.
• The plating is highly sensitive to the parameters (temp, conc, pH). The reagents should be added in due course.

Characterization:

• TEM
• EDX

Properties:
Size: 3-4 nm (TEM)
Stability: stable against repeated washing and sonication

Speculated Application:
Catalysis