- Jitto Titus

CARBON NANOTUBES

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Carbon Nanotubes • What, Who,

When, How • Physics

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Detectors Sources

Spectroscopic Imaging

Filters and Polarizers

Graphene sheet rolled up to form a closed seamless cylinder

What are Carbon Nanotubes?

Sumio Iijima (1991)

High Aspect Ratio

Length-to-diameter ratio of up to 132,000,000:1

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Types of Carbon Nanotubes

First ever TEM image of CNT (right)

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Physics of Carbon Nanotubes

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Physics of Carbon Nanotubes

a) Energy Band Structure b) Allowed electron states and the K-points in the Brillouin zone (|n-m| is a multiple of 3 for metallic state)

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Physics of Carbon Nanotubes

Energy versus Density of States (DOS)

DOS for SWNTs

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Bolometric Photoresponse

100 nm thick mostly semiconducting SWNT film suspended on a sapphire ring using electrical contacts at 50K

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Itkis, M. et. Al., Science, Vol 312, (2006) 10

Bolometric Photoresponse

A) Schematic of DOS of semiconducting SWNT and the interband transitions B) Spectra of Near IR absorption and the photoresponse

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Itkis, M. et. Al., Science, Vol 312, (2006) 11

Bolometric Photoresponse

A) Temperature dependence of the resistance of SWNTs of varying thicknesses (a-1 µm, b-100nm, c-40nm)

B) Corresponding voltage photoresponses of the SWNTs

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Itkis, M. et. Al., Science, Vol 312, (2006)

• Temperature Coefficient of Resistance (TCR) is comparable or greater that Vanadium Oxide based Si Bolometric detectors

• The absorption co-efficient of SWNTs is at least one order of magnitude higher that Mercury Cadmium Telluride detectors (MCT)

• Wider spectral range than MCT

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Vertically Aligned CNTs

Top – Proposed CNT structure for IR detection Bottom – Inverse dependence of the band gap on the CNT diameter

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Advantages over QWIPs • Normal Incidence • QW stacking vs CNT

Length • CNT band gap as large as

~1 to as small as a semimetal

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Electron Field Emission

Right – Color plot of electron emission from (10,10) CNT tip So

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electron source

The Physics of Carbon Nanotube Devices – Francois Leonard 14

Thermal Light Emission So

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gate voltage of single CNT

b) Dependence of current on drain-source voltage

c) SEM image of device and emission intensity

d) Tungsten light bulb next to a SWNT bulb

The Physics of Carbon Nanotube Devices – Francois Leonard 15

Electroluminescence So

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es Current injection causing electron-hole recombination and polarized photon emission

The Physics of Carbon Nanotube Devices – Francois Leonard 16

Tunable Polarizer Po

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CNT clusters suspended in Liquid Crystal stretches in the direction of an applied field

Kang et. al. Nanotech. 21 (2010) 17

Tunable Polarizer Po

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Top - CNT Cluster stretches in the direction of the applied field Left – Stretched cluster absorbs vertical polarization but is transparent to horizontal

Kang et. al. Nanotech. 21 (2010) 18

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NIR Photoluminescence

(a) An NIR photoluminescence spectrum of SWNT-Rituxan conjugate (b) AFM image of the PEGylated SWNTs (c) Schematic of NIR PL: The conjugate is not recognized by T-cell lymphoma (right) 19

NIR Photoluminescence

NIR PL images of (a) Raji cells (B-cell lymphoma) and (b) CEM cells (T-cell lymphoma) treated with the SWNT-Rituxan conjugate. (c) High-magnification NIR PL image of a single Raji cell treated with SWNT-Rituxan conjugate (d) NIR emission spectrum recorded on a SWNT-Rituxan treated Raji cell.

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Raman Scattering

- Resonance Enhanced Raman Scatter - RBM and G mode indicate the quality of the CNT

Different Isotopes functionalized for five different receptors

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Raman Scattering

Multiplexing of five intense labels in the near infrared region

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CNT based AFM Tips

5 nm radius of curvature cone-shaped tip to a cross section of an individual GroES molecule, which highlights the limitations of such tips in high-resolution imaging.

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CNT based AFM Tips

(a) Schematic illustration of surface growth process, where nanotubes grow on the pyramidal surface, guided along the edges towards the tip apex.

(b) SEM and (c) TEM images of an SWNT surface growth tip consisting of two SWNTs

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Nanotweezers

Electromechanically actuated Nanotweezers – SEM images

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Nanotweezers

(A) Approach of the nanotweezers to polystyrene nanoclusters. (B) Alignment of the tweezer arms on a small cluster. A voltage was applied to nanotweezer arms on the nanocluster, and then the nanotweezers and cluster were moved away from the sample support (C andD)

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