CNT ApplicationsCNT ApplicationsAli Ahmadpour

Ali Ali AhmadpourAhmadpour

Department of Chemical EngineeringDepartment of Chemical EngineeringFaculty of EngineeringFaculty of Engineering

Ferdowsi University of MashhadFerdowsi University of Mashhad

20142014

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Ali Ahmadpour

contentØ CNT applicationsØ CNT marketsØ Conclusions

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Applications• Diodes and transistors for computing• CNT quantum wire interconnects• Capacitors• Data Storage• Field emitters for instrumentation• Flat panel displays• Oscillators• CNT based microscopy: AFM, STM …• Nanotube sensors: force, pressure, chemical …• Biosensors

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• Molecular gears, motors, actuators• Batteries, Fuel Cells: H2, Li storage• Nanoscale reactors, ion channels• Biomedical• Lab on a chip• Drug delivery• DNA sequencing• Artificial muscles, bone replacement, bionic eye, ear ...• coatings for prosthetics and surgical implants

Cont.

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• Gene therapy• Nano-pipet• Nano-capsule• Nano-tweezer• Use in composite materials• Oil absorbent• Catalyst support• CNT ceramics• CNT based plastic packaging

Cont..

CrIr

TaTi

W

Co Fe Ni Fe/Ni Ni/CoSi wafer

Catalyst Layers

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Light elements

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CNT based Sensor

+ + + + + + + + + +

s Sio2

Nanotube

Pt contactPt contact

Gas molecules

MWNT based chemical sensor

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Gas Sensors• Gas detection instruments are increasingly needed

for industrial health and safety, environmentalmonitoring (detection of NO2 and CO) and processcontrol.

• The worldwide revenue of the gas sensors willexceed $2.5B by 2010.

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Experimental Setup for chemical sensing

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SWNT Sensor Response to NO2 with UV Light Aiding Recovery

Detection limit to NO2 is 44 ppb.

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Single-Walled Carbon NanotubesFor Chemical Sensors

Single Wall Carbon Nanotube

• Every atom in a SWNT is on the surface and exposed to environment.

• Charge transfer or small changes in the charge-environment of a nanotube can cause drastic changes to its electrical properties.

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Schematic of the fabricated conduction based sensor.

CARBON NANOTUBE BASED BIOLOGICAL AND CHEMICAL SENSORS

PBS: Phosphate buffered salineIgG: Immunoglobulin G antibodies are predominately involved in the secondary immune response

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SWNT Sensor Assembly

• Purified SWNTs in DMF (dimethyl formamide) solution• Cast the SWNT/DMF onto IDE

IDE (Integrated Drive Electronics) is a standard electronic interface used between a computer motherboard's data paths or bus

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• Interest is to develop sensors for astrobiology to study origins of life. CNT can be functionalized at the tip with a probe molecule. Current study uses AFM as anexperimental platform.

• High specificity• Direct, fast response• High sensitivity• Single molecule and

cell signal captureand detection

• The technology is to develop sensors for cancer diagnosticsü Identified probe molecule that will serve as signature of

leukemia cells, to be attached to CNTü Current flow due to hybridization will be through CNT

electrode to an IC chip.ü Prototype biosensors development

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BiosensorsCNT, though inert, can be functionalized at the tip with a probe molecule to be used as a sensor for food industry, medical and research purposes.

Schematic diagram of the CNT array biosensor

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Chemical Functionalization

Highly selective reaction of primary amine with surface –COOH group

i-Pr2NEtCO2

-CO2HDMF

N C N CyCy

N

O

O

HO

H2N FcO

HNFc

O

O N

O

O

FeFc =

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Cross-sectional view of Sodium Dodecyl Sulfate (SDS) molecules adsorbing on SWNT side wall.

3-Dimensional view of SDS molecules adsorbing on SWNT side wall

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Functionalization of DNA

CO2H

NC

NCH3

N

CH3

HCl-

O

CH3

HN

H2N ATGCCTTCCy3

ATGCCTTCCy3

CH3

HCl-

TACGGAAGGGGGGGGGGCy5

N

O

O

HOSO3Na

CH3

CO

NHC

N

CH3

N

O

O

O N

O

O

SO3Na

O

HN ATGCC TTCCy3TACGGAAGGGGGGGGGGCy5

+

EDC

+

Sulfo-NHS

DNA probe

Target DNA

Cy3 image

Cy5 image

EDC: (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide

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CNT DNA SensorUsing Electrochemical Detection

3+

2+

e

3+

2+

q MWNT array electrode functionalized with DNA/PNA probe as an ultra-sensitive

sensor for detecting the hybridization of target DNA/RNA from the sample.• Signal from redox bases in the excess DNA single strands

q The signal can be amplified with metal ion mediator oxidation

catalyzed by Guanine.

Ru bPy( )32 +[ ]

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Hydrogen storage

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Fuel Cells2010 global market estimated at $100 billion

•Automotive

•Power Grid

•Battery Replacement

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Fuel Cells

Fuel cells consist of an electrolyte material sandwiched between two electrodes.

The input fuel passes over the anode (and oxygen over the cathode) where it catalytically splits into ions and electrons.

The electrons go through an external circuit to create electricity.

The ions move through the electrolyte toward the oppositely charged electrode where they combine to create by-products, primarily water and CO2.

what is it?

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Fuel Cells

• Proton Exchange Membrane (PEM) • Direct Methanol (DMFC) • Solid Oxide Fuel Cells (SOFC)• Molten Carbonate Fuel Cells (MCFC)• Alkaline Fuel Cells (AFC)• Regenerative Fuel Cells (one unit can run as both a

fuel cell and electrolyzer)• Phosphoric Acid Fuel Cells • Enzymatic Fuel Cell Battery• Zinc-Air Batteries

what kinds are there?

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Fuel CellsWhere does nanotech come in?

Hydrogen atoms are stripped of their electrons at the anode, and the positively charged protons diffuse through one side of the porous membrane and migrate toward the cathode

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Fuel cells

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SWCNTs in H2 fuel cells

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Proton Exchange Membrane

Fuel Cells

• Air efficiency 30-60%• Oxygen efficiency 50-80%• light weight• durable• green

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Fuel Cells - Costs

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Fuel Cells & Nanotech

• More efficient proton exchange

• Higher density hydrogen (fuel) storage

• lower cost ???

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Fuel Cells CompaniesBallard Power Systems

General MotorsHitachi

HoneywellMitsubishiMotorola

NECSeimens AG

Sony

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Hydrogen storage with electrochemical charge-discharge cycles

−− ++ →++ xOH)xHCNT(xeOHCNT eargch2

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Simulated Mars dust

Atomic Force Microscopy is a powerful technique for imaging, nanomanipulation, as platform for sensor work, nanolithography...

Conventional silicon or tungsten tips wear out quickly. CNT tip is robust, offers amazing resolution.

2 nm thick Au on Mica

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Electrical Properties of CNTs

Voltage Bias (mV)-5.0 -2.5 0.0 2.5 5.0

Cur

rent

(nA

)

-10

-5

0

5

10

-5V 0 +5V

+1mA

-1mA

0

HPanalyzer

Current Sensing AFM Four-probe stationAnd HP parameter analyzer

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35Nguyen et al., App. Phys. Lett., 81, 5, p. 901 (2002).

Photoresist Patterns Generated by Interferometric Lithography

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2 nm thick Au on Mica

5 nm thick Ir on Mica

Si3N4 on Silicon substrate

Nguyen et al., Nanotechnology, 12, 363 (2001).

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*First single nanotube logic device – Inverter demonstration (Appl. Phys. Lett., Nov. 2001)by Chongwu Zhou (USC) and Jie Han (NASA Ames)

2.5

2.0

1.5

1.0

0.5

0.0

Vou

t(V)

2.52.01.51.00.50.0Vin(V)

VDD=2.9 V

Vin Vout

0 V

VDD

p

n

100806040200

IDS

(nA

)

-20 -15 -10 -5 0Vg(V)

VDS=10 mV

12

8

4

0D

S(n

A)

-10 -5 0 5 10Vg (V)

VDS=10 mV

V0 VDDCarbon nanotuben-type p-type

Vout

Vinp-MOSFET

n-MOSFET

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MWNT Interconnects ?

CNT advantages:(1) Small diameter(2) High aspect ratio(3) Highly conductive along the axis(4) High mechanical strength

Question: How to do this ?

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Bottom-up Approachfor CNT Interconnects

TEOSCVD

CatalystPatterning

SiO2/Si

Metal Deposition

Plasma CVD CMP

Top Metal Layer Deposition

J. Li, Q. Ye, A. Cassell, H. T. Ng, R. Stevens, J. Han, M. Meyyappan, Appl. Phys. Lett., 82(15), 2491 (2003)

Ti, Mo, Cr, Pt

Ni

At ~ 400 to 800° C

CMP : Chemical Mechanical Polishing slurry for copper interconnectsTEOS: Tetraethyl orthosilicate is a crosslinking agent in silicone polymers

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Nanocomposites

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Nanocomposites• Nanomaterials often have different properties than their bulk-scale

counterparts- nanocrystalline copper is five times harder than ordinary copper

• Nanocomposites are materials where the constituents are mixed on a nanometer scale

- A nanoscale dispersion of sheet-like inorganic silicate particles in a polymer matrix is superior to either constituent in such properties as optical clarity, strength, stiffness, thermal stability, reduced permeability, and flame retardancy.

• Abalone shell has alternating layers of calcium carbonate and a rubbery biopolymer. It is twice as hard and a thousand times tougher than its components.

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Nanocomposites• Multi-constituent materials.

• Superior overall properties compared to constituent properties e.g. optical clarity, strength, stiffness, permeability.

• Ability to tailor properties.

• Constituents have at least one dimension in the nanometer scale.– Nanoparticles (Three nano-scale dimensions)– Nanofibers (Two nano-scale dimensions)– Nanoclays (One nano-scale dimensions)

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NanocompositesTypes

• plastics• foams• aerogels• powders• membranes• coatings• films• catalysts• semiconductors• magnets• etc.

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Nanotube-reinforced Composites

• Nanotubes in metal, metal oxide and ceramic matrix have been fabricated.

• Typical fabrication process is by hot-pressing the powdered matrix with the nanotubes.

• Nanotubes in polymer matrices by mixing, then curing.

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NanocompositesMarket

$1.2 billion in 2009

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Ethanol productioninside CNTs

• CNTs are increasingly recognized as promising materials for catalysis, catalyst additives or supports.

• Researchers in China used CNTs loaded with rhodium (Rh) nanoparticles as reactors to convert a gas mixture of CO and H2 into ethanol (nanosized CNT reaction vessel).

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CNT Applications in Food industries

• Functionalized CNT: When CNT is attached by organic functional groups, it can be dissolved into solution. This will increase processability of CNT for device fabrication.

• Polymer-CNT Gas Sensor: vapor/gas sensor based on carbon nanotube and polymer nanocomposites.

• Biosensors: Novel applications which makes possible the reversibility of some redox-enzymes reactions, which are irreversible at common electrodes.

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Cont.• Biological application: For protein crystallization and

bioreactors.

• Membrane synthesis using CNTs: For detection and separation of enzymes, antibodies, proteins, vitamins, minerals, and DNA.

• Conductive membrane: More separation of aromas and

nutritious from food substances.

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CNTs Find New Applications as Heat Sensors for Hot Chilli Peppers

• HPLC, which is currently used, requires bulky, expensive equipment and detailed analysis of the capsaicinoids.

• In the new method, the capsaicinoids are adsorbed onto MWCNT electrodes. The current change is measured as the capsaicinoids are oxidised by an electrochemical reaction, and this reading can be translated into Scoville units.

• The technique is called adsorptive stripping voltammetry (ASV), and is a relatively simple electrochemical method.

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• CNTs are just the thing for cleaning up poisonouspollutants. These tiny tubes mop up dioxins, thehazardous and persistent by-products of a widerange of industrial processes that contaminatethe air, soil, water and, thence, the food chain.

• CNTs attract much more dioxin than activatedcarbon, currently used to clean up incineratorgases.

Environmental applications of CNTs

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Purification of airand water

• Another environmental catalysis includesphotocatalysis for air and water purificationand for heavy metal removal. The Base is CNTand active material is nanostructured TiO2.Environmentally toxic materials such asvolatile organic compounds and heavy metalcompounds become harmless by oxidation orreduction processes.

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BatteriesCNTs in lithium batteries could improve their capacity for energy.

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Battery from aligned CNTs

A sheet of aligned carbon nanotubes is rolled on a cylinder. Wiley-VCH Verlag GmbH & Co. KGaA.

Vertically grown aligned CNT forests are drawn into aligned CNT sheets and coated with silicon (10 times greater capacity).

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Flexible CNT battery for flexible displays

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Thermoelectric

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MWCNT-based dry adhesive• Vertically aligned MWCNT arrays can mimic

the hairs on a gecko’s foot and act as a dry adhesive.

• In nature, geckos use dry adhesion forces to climb walls. They have inspired researchers to develop synthetic gecko foot hairs to be used in, for example, robot applications.

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Comparisons of adhesive strengths among various natural and synthetic materials

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Application Areas• Dynamics & Vibrations• Sensors• Actuators• Structural Mechanics• MEMS• Feet for wall-climbing robots• Dry, reversible adhesive in electronic devices• Outer space, where most adhesives don’t

work because of the vacuum.

stress in a synthetic Gecko foot's nano-hairs 1/25 as long as the micro-hair

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CNT Muscles Strong as Diamond, Flexible as Rubber

These tiny weight lifters can haul a load 200 times heavier than a human muscle of the same size.

In order to make one pound of the stuff, four billion miles of nanotubes would have to be spun together.

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CNT transistor and computer

CNTs sits on top of features etched in silicon.

This wafer contains tiny computers using CNTs, a material that could lead to smaller, more energy-efficient processors.

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Space Elevator

The Obayashi Corporation (Japanese) has announced plans to build a space elevator by 2050 by a cable (possibly made from CNTs), with the aim of taking tourists 20,000 miles above the planet’s surface. In theory, it could support 30 tons/mm2 needed to construct such an incredible system.

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CNT Market• Global CNT production capacity is ~ 2.5 tons per day.• Bayer is planning to produce about 3,000 tons CNTs by 2012.

• The price of MWCNTs has fallen from tens of thousands of dollars in just few years ago to hundreds of dollars per kg.

• Recent market analyses forecast sales of all nanotubes to reach 1-2 billion dollars annually within the next four to seven years.

• In terms of dollar value, electronics devices will be the largest end-use category, although composite materials may account for greater volumes. These volumes are expected to approach several thousand metric tons per year.

Ali Ahmadpour

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ConclusionsØ CNTs have attracted much attention due totheir remarkable properties.

Ø These materials will have a significantcontribution to the new science fields.

Ø Complete experimental characterization ofCNTs is not an easy task, as there areseveral parameters affecting the type andstructure of CNTs.

Ø Theoretical methods of characterization isnecessary to have better control over theCNT preparation step.

Ø Future advancement of nanotube science and technology requires much research works.

Ali Ahmadpour