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

No Reducing Agent Needed AND Suspended in Water

"Hole-Doped Single-Walled Carbon Nanotubes: Ornamenting with Gold Nanoparticles in Water"

Kim, D. S.; Lee, T.; Geckeler, K. E. Angew. Chem. Int. Ed. 2006, 45, 104-107.

10.1002/anie.200500234

Points:

Frontier orbital theory - hole doping of SWNTs

Done in surfactant solution, thus with small quantities

Materials: Au-SWNT

Synthesis:

• 1 mg SWNT was suspended in Tween-80 (0.1 wt%, 10mL) with ultrasonication and subject to high-speed centrifugation (80,000 g, 3h). Supernatant conc was determined to be ~48 mg/L. 0.3 mg KAuCl4 was then added to 1.2 mL of the above solution.
• The "optimized procedure" for TEM was 60 C, 1h.

Characterization:

TEM

EDX

Raman:

• Decays in RBM and G-band "is a strong indication ofthe removal of electrons from the conduction band of carbon nanotubes following the reduction of metal ions at the surface of nanotubes"
• "the peak of the tangential G-band shifted to a higher frequency" "as a stiffening of thegraphene mode, caused by the introduction of holes into the conduction band of nanotubes as a result of the charge transfer interaction".

Properties:

• 2.94(+-0.75) nm
• When increasing the salt conc to 3.5 mM, Au particle was found to be ~9 nm.
  

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

Enhancing MWNT Hydrogen Storage via V/Pd Decoration

"Enhancement of hydrogen storage capacity of carbon nanotubesvia spill-over from vanadium and palladium nanoparticles"

Zacharia, R.; Kim, K. Y.; Kibria, A. K. M. F.; Nahm, K. S. Chem. Phys. Lett. 2005, 412, 369-375.
doi:10.1016/j.cplett.2005.07.020

"The increased hydrogen storage capacity of transition metal-doped carbon nanostructures is attributed to the initial hydrogen adsorption by metal nanoparticles which subsequently dissociate the hydrogen molecules and spill them over to carbon nanotubes."

Materials: V-MWNT; Pd-MWNT

Synthesis:
Electroless:
100 mg MWNTs (CVD from acetylene, purified) and 3 mg PdCl2 were sonicated in acetone for 12 h. Pd2+/Pd: +0.951V (vs SHE).
Reduction-H2:
100 mg MWNTs and 5 mg VCl3 were sonicated for 12 h. Reduced by hydrogen at 250C for 2h.

Characterization:
TEM (Likely incorrect assignments)
Raman
Hydrogen adsorption:

• Sieverts volumetric apparatus: 100 mg CNT; 6h 400C 10(-4) degassing; 2MPa H2.



• V-MWNT (0.69wt%) = Pd-MWNT (0.66) > purified MWNT (0.53) > as-produced (0.31)



• More than half of the hydrogen adsorbed might be attributed to carbon phase



• Desorption: more reversible for V-MWNT than Pd-MWNT at r.t.

Applications:
Hydrogen Storage

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

FOREWORD

This site is built for the sole purpose of collecting the up-to-date literature information for metal-decorated carbon nanotubes.

The blog articles not only list published literature information, but also often contain the blogger's own subjective opinions. The reader shall make his/her own judgement.