1. P ROCESS TO C ONTROL C ARBON NANOTUBES C HIRALITY Edson P. Bellido Sosa

2. I NTRODUCTION CNTs are allotropes of carbon Composed of sp 2 bonds Highest length-to-diameter ratio MWCNTs and SWCNTs Extraordinary mechanical properties  Young modulus 1-5TPa  Tensile strength 11-150GPa Efficient thermal conductors  thermal conductivity 3500 W/(m·K) S. Iijima, "HELICAL MICROTUBULES OF GRAPHITIC CARBON," Nature, vol. 354, pp. 56-58, Nov 1991. S. Iijima and T. Ichihashi, "SINGLE-SHELL CARBON NANOTUBES OF 1-NM DIAMETER (VOL 363, PG 603, 1993)," Nature, vol. 364, pp. 737-737, Aug 1993.

3. I NTRODUCTION Unique electrical properties  Structure dependent (chirality)  Can be semiconductor or metallic  Metallic CNTs can carry 1000 times more current than copper  MWCNTs show superconductivity at relatively high T (12K) Optical properties  Absorption and photoluminescence depends of structure (chirality)  No luminescence can be produced in metallic (exciton)  SWCNTs forest near ideal black body (absorbances of 0.98–0.99) http://en.wikipedia.org/wiki/Optical_properties_of_carbon_nanotubes http://gtresearchnews.gatech.edu/images/gecko-film-side-view.jpg

4. CNT STRUCTURE Describe in terms of graphene lattice vectors CNT=rolled graphene Unit cell spanned by a 1 and a 2 and form and angle of 60°| a 1 |=| a 2 |=2.461Å Circumference of the tube c = n a 1 + m a 2 ; c also called Chiral vector CNTs usually describe by (n,m) http://www.personal.reading.ac.uk/~scsharip/Wedge.jpg

5. CNT STRUCTURE n = m (chiral angle = 0°) tubes are called "armchair" m = 0 (chiral angle = 30°) "zigzag" http://en.wikipedia.org/wiki/Optical_properties_of_carbon_nanotubes

6. CNT STRUCTURE The indexes (n,m) determine if a CNT is metallic or semiconductor |m-n|=3k ; k an integersemi-metallic |m-n|=3k ±1 ; k an integersemiconductor Diameter of the CNT is also related to (n,m) Empiric relation for band gap on semiconducting CNTs E g =0.767/d |m-n|=0metallic

7. M ETHODS TO OBTAIN MONODISPERSE SWCNT S Selective chemistry Selective destruction Dielectrophoretic separation Ultracentrifugation Selective growth M. C. Hersam, "Progress towards monodisperse single-walled carbon nanotubes," Nature Nanotechnology, vol. 3, pp. 387-394, Jul 2008.

8. C LONING C ARBON Baked in air and washed with washed in hydrochloric acid. Fluorination process Hydrazine treatment, and final treatment with H 2 SO 4 -H 2 O 2 Polymer wrapping PEI-Fe(NO 3 ) 3 solution was mixed with 5 mL of aqueous wrapped SWNTs R. E. Smalley, et al., "Single wall carbon nanotube amplification: En route to a type-specific growth mechanism," Journal of the American Chemical Society, vol. 128, pp. 15824-15829, Dec 2006.

9. C LONING C ARBON The solution was deposited on Si and baked at 350 ° C Fe(NO 3 ) 3 converts to iron oxides (FeO) Place the sample in a tube furnace and heated in H 2 at 500 ° C CVD at 750 ° C R. E. Smalley, et al., "Single wall carbon nanotube amplification: En route to a type-specific growth mechanism," Journal of the American Chemical Society, vol. 128, pp. 15824-15829, Dec 2006.

10. C LONING C ARBON R. E. Smalley, et al., "Single wall carbon nanotube amplification: En route to a type-specific growth mechanism," Journal of the American Chemical Society, vol. 128, pp. 15824-15829, Dec 2006.

11. T UNING NANOPARTICLES Nano-catalyst fabricated in a microplasma reactor Plasma of nickelocene (pure Ni particles) Plasma of nickelocene and ferrocene (Ni x Fe 1-x ) CVD process to fabricate SWCNTs 2.0 ppm2.6 ppm 1.3 ppm 2.2 ppm W. H. Chiang and R. M. Sankaran, "Linking catalyst composition to chirality distributions of as-grown single-walled carbon nanotubes by tuning NixFe1-x nanoparticles," Nature Materials, vol. 8, pp. 882-886, Nov 2009.

12. T UNING NANOPARTICLES W. H. Chiang and R. M. Sankaran, "Linking catalyst composition to chirality distributions of as-grown single-walled carbon nanotubes by tuning NixFe1-x nanoparticles," Nature Materials, vol. 8, pp. 882-886, Nov 2009.

13. T UNING NANOPARTICLES W. H. Chiang and R. M. Sankaran, "Linking catalyst composition to chirality distributions of as-grown single-walled carbon nanotubes by tuning NixFe1-x nanoparticles," Nature Materials, vol. 8, pp. 882-886, Nov 2009.

14. T HANK YOU

15. R EFERENCES S. Iijima, "HELICAL MICROTUBULES OF GRAPHITIC CARBON," Nature, vol. 354, pp. 56-58, Nov 1991. S. Iijima and T. Ichihashi, "SINGLE-SHELL CARBON NANOTUBES OF 1-NM DIAMETER (VOL 363, PG 603, 1993)," Nature, vol. 364, pp. 737-737, Aug 1993. "Optical properties of carbon nanotubes -." Wikipedia, the free encyclopedia. Web. 01 Feb. 2010.. M. C. Hersam, "Progress towards monodisperse single-walled carbon nanotubes," Nature Nanotechnology, vol. 3, pp. 387-394, Jul 2008. R. E. Smalley, et al., "Single wall carbon nanotube amplification: En route to a type-specific growth mechanism," Journal of the American Chemical Society, vol. 128, pp. 15824-15829, Dec 2006. W. H. Chiang and R. M. Sankaran, "Linking catalyst composition to chirality distributions of as- grown single-walled carbon nanotubes by tuning NixFe1-x nanoparticles," Nature Materials, vol. 8, pp. 882-886, Nov 2009.

16. G1 Rebuttal: Nanowire photonics Edson P. Bellido Sosa

17. Comment: The introduction part didn’t include basic concepts from spectroscopy, necessary to be able to interpret the results from the presented research work. Yes, I did not considered necessary to mentioned those basic concepts of characterization techniques since I thought the audience had this knowledge. However, during the presentation I have noticed that this was not the case. Comment: It should have been illustrated the design requirements and working principle of at least one potential application such as the procedure to make a logic in a photonic computer or the remote detection of threat agents. I chose to only talk about one application in detail since the time of the presentation was limited.

18. Comment: Hard to understand diagrams without explanation I did not want to include much text on slides. I wanted to include important diagrams in the same slide to compare the different characterization techniques. But I explain the details on the talk. Comment: The presentation was based in only one paper, which refrained the audience from evaluating how the presented research stands on the whole field. I chose to talk about one application in detail since the time of the presentation was limited and photonics is very wide field. Comment: We have talked about toxicity of nanowires for half-semester long but no one yet came to a conclusion. I Agree. However I think the problem is that not much research is being doing in this field in comparison with research doing in applications and basic science of nanowires and other nanostructures.

19. Photonic nanowires – Lecture review The introduction part didn’t include basic concepts from spectroscopy, necessary to be able to interpret the results from the presented research work. It was shown in detail only the procedure to synthesize the nanowires. It should have been illustrated the design requirements and working principle of at least one potential application such as the procedure to make a logic in a photonic computer or the remote detection of threat agents. Elemental devices like‘optical microcavity’ or ‘r ing resonators’ which enable many photonic applications were not mentioned. Limitations on the controlled connection or assembly of nanowires, which is fundamental to enable potential applications, were not illustrated. Alfredo D. Bobadilla

20. By: Mary Coan 3-30-10

21.  Listed applications for Photonics  Gave positive aspects of Nanowires  Discussed Formation of Nanowires  Hard to understand diagrams without explanation  Used graphs and diagrams to convey message  Did not use bulletins so I can not follow

22. Review G1-Photonics Diego A Gomez-Gualdron

23. Photonics Consist in the technical application of light (generally visible) in order to perform a task (e.g. sensing, information processing) A signal transmitted by light traveling through optic fibers www.digitalization.wordpress.com www.wikipedia.com mechanism The decay of an excited electron (with energy E2) to a non-excited state (with energy E1) is accompanied with the emission of a photon with energy hv=E2-E1

24. Nanowires A nanowire emitting lightStructure of a Silica nanowire www.nersc.govwww.fas.harvard.edu * Nanowire are cylindrical structures (typically semiconductors) with a high aspect ration an a diameter in the nano scale. Being semiconductors, the light they emit depends on their band gap (the energetic difference between the valence and conduction band) If one can tune the nanowire band gap, then you can control what light wavelength is emitted ‘ALLOY’ COMPONENTS!!!

25. Tuning the Band Gap A rule of thumb is that if one mixes component A with a band gap E A and component B with a band gap E B, such that the resulting fraction are X A and X B, the resulting band gap is given by: E AB =X A E A +X B E B (1) Let us mix GaN and InN in a nanowire!!! Increase of In molar fraction Nature Mater. 6, 951–956 (2007). Change in the emitted light with composition Equation (1) holds Change in the emitted light with composition Increase of In molar fraction

26. REVIEW The speaker made a good job explaining the material contained in the slides. However, the presentation fell short in its scope. Photonics is a very wide field. Although understandable that it can hardly be covered in 50 min, a greater effort in making the overview should have been made, so the bigger picture of the field could have been captured The presentation was based in only one paper, which refrained the audience from evaluating how the presented research stands on the whole field. Moreover, the paper presented was likely not the latest advance on the field as it was published three years ago.

27. REVIEW The presentation was too short (13 slides), and the speaker missed the opportunity to compensate the use of just one paper, by explaining it thoroughly, more specifically, the experimental procedure. Even when the synthesis of nanowires was covered in the first presentation of the semester, there was more to it. For instance, there are problems specifically related to the alloying of GaN and InN. Also, the speaker misinterpreted the experimental procedure. Particularly, how the control of the concentration was made. The speaker interpreted that this was made by changing the distance of the substrate to the nozzle, when in fact is made by controlling the vapor pressure of the Ga an In precursors (therefore the independent heating sources), as it can be read in the actual paper.

28. Review for G1 Jung Hwan Woo

29. Details on these research fields can really help improve the conclusion of the presentation What are the fields that can take advantage of large scale integration? We have talked about toxicity of nanowires for half-semester long but no one yet came to a conclusion. Maybe it is time for some of the presenters to come up with something remotely close to supporting for or against the usability of nanowires on human body based on the toxicity. Example of photonic computing could help the audience to understand what it is. Same for single photon sources