Sensori Chimici in Fibra Ottica basati su Nanotubi di Carbonio

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

Optoelectronic Division - Engineering Department

University of Sannio, Benevento – Italy

Sensori Chimici in Fibra Sensori Chimici in Fibra OtticaOttica

basati su Nanotubi di basati su Nanotubi di CarbonioCarbonio

M. Consales1, M. Pisco1, S.Campopiano2, A. Cutolo1, M. Penza3, P. Aversa3,

M. Giordano4, A. Cusano1

(1): University of Sannio, Optoelectronic Division -Engineering Department, Benevento - Italy.

(4): Institute for Composite and Biomedical Materials, CNR, Napoli, Italy.

(2): Department for Technologies, University Parthenope, Napoli, Italy

(3): ENEA, Materials and New Technologies, CR Brindisi, Brindisi - Italy.

POSTER # A27POSTER # A27




Silica Optical Fiber (SOF) SensorsFor an important number of environmental monitoring and industrial applications fiber-optic sensor technology offers several advantages for significant metrological improvement through:

The scientific community is interested in:

High sensitivity

Immunity to electromagnetic interference

Safety in the corrosive environments

Fast response

This technology is suitable for distributed measurements and it is, by definition, compatible with the fiber-optic communication networkscompatible with the fiber-optic communication networks

New devices able to provide high performance sensing mechanism and multiplexing capability.




Principle of OperationPrinciple of Operation

ΔΔRRfilmfilm=f (=f ( ΔΔεεFilmFilm , , ΔΔddFilmFilm))

•Rfilm is the fiber-film reflectance

•εSWCNTs= ε1+jε2 is the dielectric constant of

the film

• dSWCNTs is the film thickness

When the optical probe is exposed to a target analyte, its molecules are When the optical probe is exposed to a target analyte, its molecules are adsorbed within the sensitive layer, changing its thickness and adsorbed within the sensitive layer, changing its thickness and

complex dielectric function and thus the optical signal reflected at the complex dielectric function and thus the optical signal reflected at the fiber film interface.fiber film interface.

Pinc

Pref

Single-mode optical fiber SWCNTs sensitive layer

Pinc

Pref

Single-mode optical fiber SWCNTs sensitive layer




Why Single-Walled Carbon Nanotubes (SWCNTs)?Why Single-Walled Carbon Nanotubes (SWCNTs)?

Carbon nanotubes are basically sheets of graphite

rolled up into a tube to form a cylinder.

• Peculiar hollow structure

• Diameters in the range 1-10 nm

• High specific surface area (100-1800 m2/g)

• Particular interactions between carbon atoms and gas molecules




Langmuir-Blodgett (LB) deposition techniqueLangmuir-Blodgett (LB) deposition technique

HiPco SWCNTs (purchased by CNI) films have been deposited

monolayer by monolayer by successively dipping the substrates up and

down through the monolayer




Structural and morphological CNTs characterizationStructural and morphological CNTs characterizationSEM image of SWCNTs bundlesSEM image of SWCNTs bundles XRD from SWCNTs powderXRD from SWCNTs powder

HRTEM image of SWCNTs bundlesHRTEM image of SWCNTs bundles

Low magnificationLow magnification

HRTEM image of SWCNTs bundlesHRTEM image of SWCNTs bundles

High magnificationHigh magnification

•Mean rope diameter: 1-40 nmMean rope diameter: 1-40 nm

• Mean rope length: 2-15 Mean rope length: 2-15 µm µm

• Monolayers spacing ~ 2.0 nmMonolayers spacing ~ 2.0 nm




Volatile Organic Compounds (VOCs) detection Volatile Organic Compounds (VOCs) detection

Standard Silica Optical Fiber coated by 4 monolayers of SWCNTs (approx. 8nm)

120 180 240 300 360

0.76

0.77

0.78

0.79

0.80

Time (min)

54 ppm

64 ppm

73 ppm

Op

to

electro

nic S

ig

na

l

93 ppm TOLUENE

120 180 240 300 360 420 480

0.765

0.770

0.775

0.780

0.785

0.790

0.795

0.800

Time (min)

3 ppm

7 ppm

O

ptoelectron

ic S

ign

al (

A.U

.)

17 ppm

22 ppm

27 ppm

39 ppm XYLENE

Response of a Carbon Nanotubes based SOF sensor to different concentrations of (a) toluene and (b) xylene vapors, at room

temperature.

XYLENE VAPORSXYLENE VAPORS

Resolution of approx. 120 ppb

Response times (10%-90%) of approx. 11 minutes

Recovery times (90%-10%) of approx. 6 minutes

TOLUENE VAPORSTOLUENE VAPORS

Resolution of approx. 290 ppb

Response times (10%-90%) of approx. 9 minutes

Recovery times (90%-10%) of approx. 5 minutes




Hollow-core Optical Fibers (HOFs) based chemical Hollow-core Optical Fibers (HOFs) based chemical sensorssensors

180 240 300 3602.580

2.583

2.586

2.589

Op

toel

ectr

onic

Sig

nal

(A

.U.)

Time (min)

184 ppm

200 ppm

291 ppm

TetraHydroFuran

Response of the photonic band-gap fiber based sensor to three decreasing concentration of THF

vapors, at room temperature.

Images of a photonic band-gap optical Images of a photonic band-gap optical fiber without and with SWCNTsfiber without and with SWCNTs

HOF coated by 20 monolayers of SWCNTs for TetraHydroFuran

(THF) vapors detection




Hydrogen Detection at Criogenic TemperaturesHydrogen Detection at Criogenic Temperatures

120 140 160 180 200 220 240 260

0.485

0.486

0.487

0.488

0.489

0.490

0.491

0.492

0.493

0.494

Hydrogen off

Opt

ical

res

pons

e (A

.U.)

Time (min)

Hydrogen on at lower concentration

Hydrogen off

Hydrogen on

T=-160°C

Response of a Carbon Nanotubes based optical fiber sensor to two different concentration of gaseous

hydrogen, at -160°C.




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Sensori Chimici in Fibra Ottica basati su Nanotubi di Carbonio

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