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

PROCESS TO CONTROL CARBON NANOTUBES CHIRALITY

Edson P. Bellido Sosa

INTRODUCTION• CNTs are allotropes of carbon

•Composed of sp2 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.

INTRODUCTION

•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

CNT STRUCTURE •Describe in terms of graphene lattice vectors•CNT=rolled graphene •Unit cell spanned by a1 and a2 and form and angle of 60°|a1|=|a2|=2.461Å•Circumference of the tube c = na1 + ma2; c also called Chiral vector•CNTs usually describe by (n,m)

http://www.personal.reading.ac.uk/~scsharip/Wedge.jpg

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

CNT STRUCTURE

•The indexes (n,m) determine if a CNT is metallic or semiconductor

|m-n|=3k ; k an integer semi-metallic

|m-n|=3k ±1 ; k an integer semiconductor

•Diameter of the CNT is also related to (n,m)

•Empiric relation for band gap on semiconducting CNTs

Eg=0.767/d

|m-n|=0 metallic

METHODS TO OBTAIN MONODISPERSE SWCNTS

•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.

CLONING CARBON

•Baked in air and washed with washed in hydrochloric acid.•Fluorination process•Hydrazine treatment, and final treatment with H2SO4-H2O2

•Polymer wrappingPEI-Fe(NO3)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.

CLONING CARBON•The solution was deposited on Si and baked at 350°C•Fe(NO3)3 converts to iron oxides (FeO)•Place the sample in a tube furnace and heated in H2 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.

CLONING CARBON

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.

TUNING NANOPARTICLES

•Nano-catalyst fabricated in a microplasma reactor•Plasma of nickelocene (pure Ni particles)•Plasma of nickelocene and ferrocene (NixFe1-x)•CVD process to fabricate SWCNTs

2.0 ppm 2.6 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.

TUNING 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.

TUNING 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.

THANK YOU

REFERENCES

•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. <http://en.wikipedia.org/wiki/Optical_properties_of_carbon_nanotubes>.•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.

G1Rebuttal: Nanowire photonics

Edson P. Bellido Sosa

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.

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.

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 ‘ring resonators’ which enable many photonic applications were not mentioned.

Limitations on the controlled connection or assembly of nanowires, which isfundamental to enable potential applications, were not illustrated.

Alfredo D. Bobadilla

G3 REVIEW:NANOWIRE PHOTONICS

By: Mary Coan3-30-10

Review

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

Review G1-Photonics

Diego A Gomez-Gualdron

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

Nanowires

A nanowire emitting light Structure 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!!!

Tuning the Band GapA rule of thumb is that if one mixes component A with a band gap EA and component B with a band gap EB, such that the resulting fraction are XA and XB, the resulting band gap is given by:

EAB=XAEA+XBEB (1)

Let us mix GaN and InN in a nanowire!!!

Increase of In molar fractionNature Mater. 6, 951–956 (2007).

•Change in the emitted light with composition

•Equation (1) holds•Change in the emitted light with composition

Incr

ease

of I

n m

olar

frac

tion

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.

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.

Review for G1

Jung Hwan Woo

• 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