Vaneet Sharma Carbon Nanotubes

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  • Title slide.
  • At this point, let me introduce some fundamentals of SWNTs Resonance Raman Sectra which are important in further characterization of SWNTs separations. This a typical 514 nm laser excited RRS spectra from HipCo processed SWNTs. Eventhough small peak features are heavily under study both in theory and experiments, I would like to point our four important peak regions for SWNTs study. G’…. G….c D…. RBM…. Based on the fact, RBM region is strongly depending on diameter, for example, by the shown equation. By correlating the diameter and resonance condition, we can predict the NT types under irradiation. Also G-bands are known to be sensitive for the type of NTs. This is typical G-band from sem- SWNTs. Mainly lorenzean peaks are observed in this case. However, met- SWNTs provides one more specific broad gaussian feature next to the lorenzeans, which is so called BWF shape. Since the G-bands are known to be sensitive for the bundling and other environments, we are mainly concentrating on RBM modes for the characterization of this separation.
  • Vaneet Sharma Carbon Nanotubes

    1. 1. Carbon Nanotubes: synthesis, acidic oxidation and application as u ltra sharp and high aspect ratio CNT AFM probes Vaneet Kumar Sharma @Vaneet K Sharma
    2. 2. OUTLINE <ul><li>CVD Synthesis of single walled carbon nanotubes </li></ul><ul><li>Acidic oxidation of single walled carbon nanotubes </li></ul><ul><li>Application as u ltra sharp and high aspect ratio carbon nanotube AFM probes </li></ul><ul><li>Introduction to single wall carbon nanotubes (SWNTs) </li></ul>@Vaneet K Sharma
    3. 3. It was in 1991, Sumio Iijima of the NEC Laboratory, Tsukuba used High Resolution Transmission electron microscope to observe Carbon nanotubes, later in 1993 he observed single walled carbon nanotubes. In his own words it was &quot; Serendipity “, discovery by chance @Vaneet K Sharma
    4. 4. Number of different ( n,m ) SWNTs in HiPco C h =na 1 + ma 2 n = m : Metallic (zero band gap) n - m = 3k : Semi-metallic (0.04 eV band gap) n-m ≠ 3k : Semiconducting (0.6~1.2 eV band gap) where k is integer Zigzag Armchair @Vaneet K Sharma
    5. 5. Physico-Chemical Large Surface Area (~1600 m 2 /g) Amenable to electrochemical doping Hollow, molecule storage/nanoreactors Thermal conductivity twice as good as diamond (2000 W/m/K) Good thermal stability (750°C in air,) Electrical Metallic or Semiconducting ( 1-D ) met- SWNTs are ballistic conductors (10 9 A/cm 2 ) Mechanical Strongest known fiber (Young’s modulus, ~1 TPa) Highly flexible, Buckle-prone Large aspect ratio (~10 3 ) SWNT Unique Properties @Vaneet K Sharma
    6. 6. <ul><li>Micro-electronics / semiconductors </li></ul><ul><li>CNTs AFM probe </li></ul><ul><li>Controlled Drug Delivery/release </li></ul><ul><li>Solar storage </li></ul><ul><li>Biosensors </li></ul><ul><li>Field Effect transistors </li></ul><ul><li>Nano lithography </li></ul><ul><li>Single electron transistors </li></ul><ul><li>Batteries </li></ul><ul><li>Field emission flat panel displays </li></ul><ul><li>Nano electronics </li></ul><ul><li>Nano balance </li></ul><ul><li>Nano tweezers </li></ul><ul><li>Data storage </li></ul><ul><li>Magnetic nanotube </li></ul><ul><li>Nanogear </li></ul><ul><li>Nanotube actuator </li></ul><ul><li>Molecular Quantum wires </li></ul><ul><li>Hydrogen Storage </li></ul><ul><li>Noble radioactive gas storage </li></ul><ul><li>Artificial muscles </li></ul><ul><li>Waste recycling </li></ul><ul><li>Electromagnetic shielding </li></ul><ul><li>Dialysis Filters </li></ul><ul><li>Thermal protection </li></ul><ul><li>Nanotube reinforced composites </li></ul><ul><li>Reinforcement of armour and other materials </li></ul><ul><li>Reinforcement of polymer </li></ul><ul><li>Avionics </li></ul><ul><li>Collision-protection materials </li></ul><ul><li>Fly wheels </li></ul>Future Applications @Vaneet K Sharma
    7. 7. Resonance Raman spectroscopy of SWNTs @Vaneet K Sharma Name Position (cm -1 ) Origination (mode) G ’ ~ 2700 Overtone of D-band G 1550-1605 Graphite related mode (A, E 1 , and E 2 ) D ~ 1350 Defect-induced (non-sp 2 ) RBM 400~150 In phase radial displace- ments (A) HiPco SWNTs, E laser = 2.41 eV 500 1000 1500 2000 2500 Wavenumber (cm -1 ) Raman Intensity G (  G + ) D RBM G ’ G (  G - )
    8. 8. OUTLINE <ul><li>Introduction to single wall carbon nanotubes (SWNTs) </li></ul><ul><li>Acidic oxidation of single walled carbon nanotubes </li></ul><ul><li>Application as u ltra sharp and high aspect ratio carbon nanotube AFM probes </li></ul><ul><li>Chemical vapor deposition (CVD) Synthesis of single walled carbon nanotubes </li></ul>@Vaneet K Sharma
    9. 9. Synthesis <ul><li>Arc discharge </li></ul><ul><li>Laser ablation </li></ul><ul><li>Chemical Vapor Deposition (CVD) </li></ul>@Vaneet K Sharma
    10. 10. Chemical Vapor Deposition Apparatus Diagram C 2 H 2 / CH 4 /CO H 2 Ar / He Quartz boat contains catalyst, Fe/ Co/ Ni nanoparticles or Fe-Mo supported Catalyst <ul><li>Pressure: 1atm </li></ul><ul><li>Temperature: 800 ° - 900°C </li></ul><ul><li>CVD advantages </li></ul><ul><li>Potential for a large-scale synthesis of high-quality SWNTs </li></ul><ul><ul><ul><ul><li>Increased Control (in terms of narrow range of diameter) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Lower Temperatures (as compared to the arc discharge or laser ablation where the temperature is as high as 1400°C) </li></ul></ul></ul></ul>@Vaneet K Sharma
    11. 11. <ul><li>Composition and nature of metal </li></ul><ul><ul><li>Fe, Co, Ni nanoparticles etc (~ 10nm) </li></ul></ul><ul><ul><li>Fe-Mo, Co-Mo, Ni-Mo nanoparticles, (10-15nm) etc </li></ul></ul><ul><li>Supported metal nanoparticle catalyst (Al 2 O 3 , MgO, MCM-41, SBA-15) </li></ul><ul><li> The quality and yield of SWNTs are very sensitive to catalyst supports, t o induce uniformity in size for these metal nanoparticles these are well dispersed on these support </li></ul><ul><ul><ul><li>Fe/MgO, Fe/Al 2 O 3 , Fe-Mo/MgO etc ~10nm nanoparticle’s on 25-30nm support </li></ul></ul></ul><ul><ul><ul><li>Fe-MCM-41, Ni-MCM-41, Co-MCM41, Co-SBA-15 etc </li></ul></ul></ul>MCM-41 (Mobile Crystalline Material) Mesoporous materials are those with pores in the range 20-500Å in diameter. They have huge surface areas, providing a vast number of sites where sorption processes can occur. <ul><ul><ul><li>In case of MgO or Al 2 O 3 as support, load 1% catalyst on the support in methanol or butanol as solvent, under vigorous stirring, and then heating at 150 °C, finally calcination at ~ 500 °C </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Fe-MCM-41, Co-MCM-41 is prepared by isomorphously substituting metal ions for Si ions in the silica matrix of the MCM-41, the metal loaded in this case is also ~1% </li></ul></ul></ul></ul></ul>Catalyst @Vaneet K Sharma
    12. 12. <ul><li>Small size of metal nanoparticle. ( α diameter of the nanotube formed ) </li></ul><ul><li>Highly uniform, well dispersed catalyst sample, no aggregation or stacking of particles. ( α narrow range of diameters of SWNTs formed ) </li></ul><ul><li>In Mesoporous materials ( MCM 41, SBA 15 ) as support for catalysts , the catalyst should be isomorphously substituted, that is it should be in the framework of the material and not distributed on the surface. </li></ul>what is good catalyst for SWNT’s synthesis ? <ul><li>Good catalyst </li></ul><ul><li>The carbon feed is 20-40 times lower than the inert gas which is being passed in the reaction, ( 30- 45 minute feed for ~40-50 SCCM (carbon source) + 2000 SCCM inert gas ) </li></ul><ul><li>Reaction temperature is ~800-850 °C, ( below 800°C MWNT’s are formed and at temperature higher than 850-900 ° C higher Amorphous carbon and graphite content reduce the yield of SWNT’s ) </li></ul>What are ideal conditions for the synthesis of SWNT’s by CVD ? @Vaneet K Sharma
    13. 13. OUTLINE <ul><li>Introduction to single wall carbon nanotubes (SWNTs) </li></ul><ul><li>CVD Synthesis of single walled carbon </li></ul><ul><li>Nanotubes </li></ul><ul><li>Application as u ltra sharp and high aspect ratio carbon nanotube AFM probes </li></ul><ul><li>Acidic oxidation of single walled carbon nanotubes </li></ul>@Vaneet K Sharma
    14. 14. Oxidation of single walled carbon nanotubes (SWNTs) SWNTs were sonicated with (sulfuric acid: nitric acid) mixture under Ice bath (0-5 o C), filtered on Buchner funnel and washed with DI water till the pH of Filtered water becomes 7, dried overnight, ~20mg of these oxidised NTs + ~250mg ODA in a vial, were kept at 105C for 5 days, Exfoliation was observed in the oxidized SWNTs, after 5 days, ~20mL THF solvent was aded and sonicated for 1-2 minutes, well dispersed black ink was formed . For Raman studies, sample are drop cast on silicon wafer, annealed at 800 o C (10 o C/min ramp temp.). Resonance Raman characterization was done by using 1.56 ev, 1.96 ev and 2.41ev laser lines HNO 3 +H 2 SO 4 Sonication assisted @Vaneet K Sharma
    15. 15. Resonance R aman studies of effect of acid oxidation on SWNTs <ul><li>Nitric acid </li></ul><ul><li>Sulfuric acid </li></ul><ul><li>1:2(Nitric:Sulfuric acid), 1N2S </li></ul><ul><li>1:3(Nitric:Sulfuric acid), 1N3S </li></ul><ul><li>1:4(Nitric: Sulfuric acid), 1N4S </li></ul>Effect of @Vaneet K Sharma
    16. 16. Resonant Raman Investigation with 514.5 nm (2.41 eV) excitation Raman shift, cm -1 @Vaneet K Sharma
    17. 17. Resonant Raman Investigation with 514.5 nm (2.41 eV) excitation Raman shift, cm -1
    18. 18. Resonant Raman Investigation with 632 nm (1.96 eV) excitation Raman shift, cm -1
    19. 19. Resonant Raman Investigation with 632 nm (1.96 eV) excitation Raman shift, cm -1
    20. 20. Resonant Raman Investigation with 785 nm (1.56 eV) excitation Raman shift, cm -1
    21. 21. Resonant Raman Investigation with 785 nm (1.56 eV) excitation Raman shift, cm -1
    22. 22. Conclusions <ul><li>Resonance R aman characterization indicated that there are more and more defects formed, higher D/G values as we move from 1N2S, 1N3S to 1N 4S, ) 1.56 ev, 1.96 ev and 2.41 ev). </li></ul><ul><li>Resonance R aman characterization indicate d selective destruction of metallic nanotubes in case of 1N2S and 1N3S where as in case of 1N4S metallic nanotubes are still present, there is no effect of nitric and sulfuric acid on the nanotube, ( 2.41 ev) </li></ul><ul><li>Resonance R aman characterization indicate d selective enrichment of semiconductive nanotubes for 1N2S, 1N3S and 1N4S, ( 1.96 ev) </li></ul><ul><li>Resonance R aman characterization indicated loss of small diameter semiconductive SWNTs for 1N3S and 1N4S, ( 1.56ev) </li></ul><ul><li>. </li></ul>@Vaneet K Sharma
    23. 23. OUTLINE <ul><li>Introduction to single wall carbon nanotubes (SWNTs) </li></ul><ul><li>CVD Synthesis of single walled carbon nanotubes </li></ul><ul><li>Acidic oxidation of single walled carbon nanotubes </li></ul><ul><li>Application as u ltra sharp and high aspect ratio carbon nanotube AFM probes </li></ul>@Vaneet K Sharma
    24. 24. U ltra sharp and high aspect ratio CNT AFM probes by Dielectrophoresis (DEP) Owing to their geometric, electronic, chemical, and mechanical properties, CNT tips offer many advantages in nanoscale imaging and fabrication. The U ltra sharp and high aspect ratio CNT AFM probes that results in a small diameter enables high resolution images of rough surfaces with deep trenches to be taken. Oxidized shortened SWNTs (s-SWNTs) were dispersed in water or DMF with sonication and further diluted to make nanotube solutions with different concentration (0.001~0.01 mg/ml) at which the solution become colorless The deionized water and DMF are chosen as the nanotube dispersion medium whose dielectric constants are 80 and 39 respectively. SWNTs solution used is a mixture of metallic (met-) and semiconducting (sem-) nanotubes, Sem- SWNTs have finite dielectric constant with ε sem < 5 while met- SWNTs are expected to have a very large ε met- owing to the mobile carriers, These tips perform well in the scanning of biological molecules @Vaneet K Sharma
    25. 25. U ltra sharp and high aspect ratio CNT AFM probes by Dielectrophoresis (DEP) <ul><li>When a dielectric particle is subjected to an electric field, a dipole moment is induced in the particle. If the electric field is spatially non-uniform, the polarized particle experiences a force imbalance. </li></ul><ul><li>The direction of this force depends on the polarizability of the particle relative to the polarizability of the medium. </li></ul><ul><li>When an electric field is applied to a particle in a medium, the resulting torque aligns the particle parallel to the electric field. </li></ul><ul><li>Positive DEP corresponds to movement of the particle towards the high electric field, ( SWNTs have higher dielectric constant than the medium the tip of AFM probe have the highest electric field area, hence SWNTs are attracted ) </li></ul><ul><li>negative DEP corresponds to movement of the particle toward the low electric field. </li></ul>www.isso.uh.edu/publications/A2006/2006_108_wosik.htm @Vaneet K Sharma
    26. 26. Proposed mechanism (0.001~0.01 mg/ml) <ul><li>In AFM probe the tip of the nanotube solution have the highest electric field area, </li></ul><ul><li>SWNTs solution used is a mixture of metallic (met-) and semiconducting (sem-) nanotubes, </li></ul><ul><li>Sem- SWNTs have finite dielectric constant with ε sem < 5 while met- SWNTs are expected to have a very large ε met- owing to the mobile carriers. </li></ul><ul><li>met- SWNTs are expected to migrate towards the high field region (AFM tip ends) under the electric field gradients,= </li></ul>The deionized water and DMF are chosen as the nanotube dispersion medium whose dielectric constants are 80 and 39 respectively.
    27. 27. 10X optical microscope 100 X optical microscope SWNTs aqueous solution, 6V, 10seconds Immersion time @Vaneet K Sharma
    28. 28. 10V, 20 sec immersion time AFM CNT Tips U ltra sharp and high aspect ratio CNT AFM probes @Vaneet K Sharma
    29. 29. <ul><li>External electric field </li></ul><ul><li>Concentrations of the nanotube dispersion </li></ul><ul><li>Immersion time </li></ul><ul><li>Pulling rate </li></ul><ul><li>Humidity </li></ul><ul><li>AFM tip wetting </li></ul>AC field with 2.1 MHz and 6, 8 or 10 V Concentration ranges between 0.001~0.005 mg/ml immersion time is 10 -15 seconds Pulling rate should be slower than the nanotube deposition rate It was control by sealing the cell which was saturated with water vapor to minimize the solution evaporation Less the wetting, better results, as smaller capillary force, thus minimize the disturbance to the pulling process (1/3 of the tip is immersed in nanotube solution) The dimensions (diameters and length) and morphology (straightness and orientation) of the fabricated CNT tips depends on the several parameters @Vaneet K Sharma
    30. 30. Common defects @Vaneet K Sharma

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