Electroless Decoration in Single Step

"Electroless Plating of Metals onto Carbon Nanotubes Activated by a Single-Step Activation Method"

Ang, L.-M.; Hor, T. S. A.; Xu, G.-Q.; Tung, C.-h.; Zhao, S.; Wang, J. L. S. Chem. Mater. 1999, 11, 2115-2118.

doi:10.1021/cm990078i

Points:

One of the earliest work. The results were not necessarily "pretty".

Materials: Ni-MWNT, Pd-MWNT

Synthesis: MWNTs (arc-discharge, mixed-acid treated) (50 mg) were sonicated in the activation solution (25 mg PdCl2, 100 mg SnCl2.2H2O, 7.5 mL 37% HCl in 15 mL H2O) for 2 min, stirred for another 3 min, and centrifuged to collect solid, followed by washing with 1M HCl ("accelerator"). The solid was suspended and stirred in either Ni bath (containing NiCl2/NiSO4, Na3C6H5O7/NaH2PO2/NH4Cl and trace of Pb(NO3)2, at pH - 8.25) or Pd bath (PdCl2/HCl/NH4Cl/NaH2PO2) to obtain the respective products.

Characterization: TEM, EDX

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

Electroless Plating Assisted by Sn Species

"Coating of Carbon Nanotubes with Nickel by Electroless Plating Method"

Li, Q.; Fan, S.; Han, W.; Sun, C.; Liang, W. Jpn. J. Appl. Phys. 1997, 36, L501-L503.

One of the first papers on the subject.

The idea comes from the knowledge of electroless plating on various substrates. See, for example:

Menon and Martin, Anal. Chem. 1995, 67, 1920.

Material: Ni-MWNT

Synthesis:
Disperse MWNTs (from ethylene CVD, as-produced) in 0.1M SnCl2/0.1M HCl by 30 min sonication; the "pre-activated" tubes were "further activated" in 0.0014M PdCl2/0.25M HCl for another 30 min; they were then placed in an electroless plating bath, consisting of a wealth of components including Ni source (See Table).

This method is very sensitive to pH (8.25, 8.5, and 8.75 were exercised): Reaction rate increases with pH value. Thus, low pH might be desirable for less particle aggregation.

Characterization:
TEM: Low-mag.

EDAX

Magnetization

• Vibrating sample magnetometer


• Found enhanced magnetic coercivity (1550 Oe) compared to bulk Ni.

Speculated Applications:

• Microscopic magnetism


• High-density magnetic recording