Purification of Single-Walled Carbon Nanotubes and the Production of Nanotube/Elastin composite B. Zhao , A. A. Puretzky, D. Styers-Barnett, H. Hu, I. Ivanov, C. M. Rouleau, and D. B. Geohegan the Center for Nanophase Materials Sciences and Material Science & Technology Division Oak Ridge National Laboratory, Oak Ridge, TN Abstract Single-walled carbon nanotubes (SWNTs) have great potentials in many applications because of their unique structure and properties. We report a scalable purification of SWNTs synthesized by high-power laser vaporization, and the production of SWNT/elastin composites. Such material would be promise for new generalization of biocomposites. SWNTs were synthesized by high-power (600 W) laser ablation facility of carbon targets with Ni and Co as catalysts at 20 gram scale. The purification carries out at 10 gram per run by using nitric acid refluxing, controlled-pH water-extraction, and hydrogen peroxide treatment. The purification efficiency of each step was monitored by SEM, TEM, TGA, and solution phase NIR spectroscopy. The purified SWNTs contain metal residue less than 1% and carbonaceous purity among the highest ever reported. Purified SWNTs are used to make nanotube/elastin composites. SWNT/elastin composite is produced at controlled temperature and pH conditions. The electrical and mechanical properties of SWNT/elastin composite thin film are studied. Conclusion SWNTs can be synthesized by high power laser ablation at 20 gram scale. A multi-step purification method, including nitric acid oxidation, thermal annealing, H 2 O 2 oxidation, and surfactant washing, have applied to purify SWNTs. The highest purity of purified SWNTs reaches 232% against reference sample. SWNT/elastin composite material is produced at controlled pH and temp. conditions, which is a potential material in biological application. Future Work Continue on optimizing purification method of SWNTs. Study the biocompatibility and conductivity of SWNT/elastin composite material. Application of SWNT/elastin composite material in artificial skin. Acknowledgement This research was conducted in the Functional Nanomaterials Theme at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy. Collaboration: please visit http://www.cnms.ornl.gov for user project information. Synthesis of Single-Wall Carbon Nanotubes by Laser Ablation Method Co-Ni/Dylon target Furnace: 1150 o C Ar 1000 sccm laser carbon nanotube deposition quartz tube Pressure: 500 Torr Characterization of as-prepared SWNTs and Purified SWNTs TGA data Purity Evaluation of SWNTs Tools to assess SWNT purity: SEM and TEM – amorphous carbon and defect sites TGA – metal content NIR spectroscopy – interband transition Raman spectroscopy – D/G ratio Production of SWNT/Elastin Composite Material Raman Spectroscopy 100J/5Hz/20ms 1J/500Hz/1ms 10 gram scale production carbon materials with different forms catalyst free carbon nanotubes carbon nanohorns Carbon Nanotube Purification Method 1) HNO 3 12M/4h 2) centrifuge/decantation Acid treated SWNTs 30% H 2 O 2 treatment Raw SWNTs Purified SWNTs ultra-Purified SWNTs 500 o C, air, 30min wash with 6M HCl dry under vacuum • remove metal catalyst • remove amorphous carbon • exfoliate SWNT bundle • introduce functionalities Purity: 30~50% Metal: 10~15wt% Purity: 160~200% Metal: 3~5wt% Yield: 8~10% Purity: 210~230% Metal: ~1wt% Yield: 4~5% • remove amorphous carbon • remove amorphous carbon • remove metal catalyst Purity: 80~120% Metal: 2~3wt% Yield: 40~60% Purity evaluation by solution phase NIR method 8000 10000 12000 0.0 0.2 0.4 REFERENCE (R) AA(T,R) Absorbance Wavenumber (cm -1 ) 0.0 0.1 AA(S,R) R 8000 10000 12000 AA(T,X) SWNTs: 67% CARBONACEOUS IMPURITIES: 33% X AA(S,X) AA(S, R) AA(T, R) = 0.141 AA(S, X) AA(T, X) = 0.095 Purity of X against R = (0.095/0.141)*100% =67% M. E. Itkis, et. al. Nano Lett. 2003, 3, 309. Amphiphilic fibrous proteins (contains proline, glycine, lycine, etc.). Cross-linked polypeptide chains to form rubberlike, elastic fibers. Reversible uncoiling/recoiling forms based on pH and temperature. relax stretch elastin molecule cross-link controlled by pH and temperature 400 600 800 1000 1200 1400 0.0 0.2 0.4 0.6 0.8 1.0 Frequency (cm -1 ) Absorption Intensity (a.u.) raw SWNTs purity: 30% acid treated SWNTs 40% washed SWNTs 112% purified SWNTs 214% ultra-purified SWNTs 232% Results: • NIR: very high purity 232%! • Raman: D/G ratio decreased from 0.11 to 0.03 • TGA: metal residue decreased to 1% • Dispersible by DMF, SDS/H 2 O, etc. 100 200 300 400 500 600 700 800 900 1000 0 20 40 60 80 100 655 residue: 1% Purified SWNT Weight (%) Temperature ( o C) 0 20 40 60 80 100 586 residue: 10% AP-SWNT 0 1 2 0.0 0.5 1.0 500 1000 1500 2000 0 20000 40000 Ultra-purified SWNTs D/G = 0.03 Raman Intensity (a.u.) Frequency (cm -1 ) 0 10000 20000 As-prepared SWNTs D/G = 0.11 SEM and TEM images of Raw SWNTs Synthesized with Different Amount of Catalysts 0.5% Ni-Co 1.0% Ni-Co 1.5% Ni-Co Images of Purified SWNTs Solution Phase NIR Spectroscopy soluble insoluble Elastin - elastic fiber 100 nm Method SWNTs sonication elastin solution SWNT/elastin solution SWNT/elastin composite TEM image of SWNT/elastin thin film 20 nm SWNT network embedded in elastin 500 1000 1500 2000 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Absorption Intensity (a.u.) Wavelength (nm) SWNT/elastin elastin 0.26 0.37 0.39 0.58 0.58 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 12M/4h 7M / 18h 3M/48h 3M/18h 7M/6h Nitric Acid Effects to SWNTs Condition Purity (%) Yield (%) Met. Residue (wt%) Purification Effect* 12M/4h 51 52 1.7 0.26 7M/18h 88 42 2 0.37 3M/48h 74 53 2 0.39 3M/18h 83 70 2.2 0.58 7M/6h 80 73 2.4 0.58 * Purification Effect = Purity X Yield