gold surface plasmon resonance fiber optic sensor

GOLD SURFACE PLASMON RESONANCE FIBER OPTIC SENSOR Paula M. P. Gouvêa1, Michael Fokine2, Isabel C. S. Carvalho3, Marco Cremona3 and Arthur M. B. Braga1 1. Laboratório de Sensores a Fibra Óptica (LSFO), Dep. de Engenharia Mecânica, PUC-Rio, Brasil [email protected] 2. Dip. di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, Itália, [email protected] 3. Dep. de Física, PUC-Rio, [email protected]

PRESENTATION OUTLINE

Introduction ¾ Bulk glass ¾ Optical fiber ¾ Optical fiber – transmission setup ¾ Optical fiber – reflection setup ¾ Conclusions and current issues being addressed ¾


Introduction ¾ Bulk glass ¾ Optical fiber ¾ Optical fiber – transmission setup ¾ Optical fiber – reflection setup ¾ Conclusions and what’s next ¾

Surface Plasmon Resonance ¾

Surface Plasmon Resonance (SPR) - thin metal film deposited on dielectric produces a propagating surface plasmon wave with optical properties that can be used for sensing: ¾ Most available SPR sensors are of this type ¾ Complex detection scheme (angle-dependence)

Example: Kretschmann geometry (attenuated total internal reflection)

http://www.inano.dk/sw2565.asp

Localized Surface Plasmon Resonance ¾

Localized Surface Plasmon Resonance (LSPR) nanoparticles in dielectric produce a localized SPR ¾ Localized surface plasmons are excited by light absorption in the nanoparticles (no angle-dependence); absorptions bands called plasmon bands. ¾ Dependent on: metal, particle geometry (size, shape) and surrounding medium. ¾ Changes in surrounding medium lead to shifts in absorption band ⇒ sensing applications.

K. Lance Kelly et al., J. Phys. Chem. B 2003, 107, 668-677

Fiber Optic LSPR Sensing ¾

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Optical fiber - several advantages as the dielectric in the metal-dielectric boundary: ¾ Ease of handling ¾ Remote sensing ¾ Distributed and multiplexed configurations ¾ Large-scale, low cost production Fiber optic sensing based on LSPR has been demonstrated: Au thin film deposition and annealing

Au solgel

Meriaudeau, F., Wig et al, Sensors and Actuators B, 69 (2000)

Tsao-Jen Lin and Cheng-Tai Lou, J. of Supercritical Fluids 41 (2007) 317–325


Examples of detection setups for fiber optic LSPR sensing: Meriaudeau, F., Wig et al, Sensors and Actuators B, 69 (2000)

Transmission

Tsao-Jen Lin and Cheng-Tai Lou, J. of Supercritical Fluids 41 (2007) 317–325

Reflection


4-nm Au nanoparticles: absorption peak at about 530 nm.

Meriaudeau, F., Wig, A., Passian, A., Downey, T., Buncick, M., Ferrell, T.L., Gold island fiber optic sensor for refractive index sensing, Sensors and Actuators B, 69 (2000) p 51 – 57


Typical red-shift absorption peak as refractive index increases.

Meriaudeau, F., Wig, A., Passian, A., Downey, T., Buncick, M., Ferrell, T.L., Gold island fiber optic sensor for refractive index sensing, Sensors and Actuators B, 69 (2000) p 51 – 57



Nanoparticles on bulk glass 1) Deposition of Au thin film on bulk silica (infrasil 301): 150 nm (1500 Ǻ) - annealing of 80 min at 650 oC – 700 oC 2) Deposition of Au thin film on soda-lime glass: 3.5 nm (35 Ǻ) - annealing of 5 min at 650 oC before

after before

after

2 1 bulk glass

pink color typical of Au nanoparticles (LSPR)

SEM image after annealing ¾ An EDS analysis performed at Inmetro´s Scanning Electron Microscope (SEM) showed that, even though most Au particles are of the order of microns, there are a few nanometer-size particles (possible to have LSPR). Note: Inmetro's SEM does not require prior Au deposition for analysis (low vacuum).

150 nm Au film on infrasil annealed for 80 min at 650 oC – 700 oC

Courtesy of Lídia Ágata de Sena (INMETRO) bulk glass

Transmission spectrum after annealing ¾ The transmission spectrum shows an absorption peak near the expected wavelength (approximately 540 nm) – evidence of LSPR. ¾ The wide absorption peak indicates a large size distribution of Au nanoparticles, as seen with SEM.

Currently: adherence and signal intensity experiments in bulk glass

bulk glass

150 nm Au film on infrasil annealed for 80 min at 650 oC – 700 oC



Nanoparticles on optical fiber ¾

Deposition of Au thin film on surface of one endface of a singlemode optical fiber (Corning's SMF-28e): 15 nm (150 Ǻ)

optical fiber

Annealing of optical fiber tip ¾ The tip of the fiber was inserted into the oven after it reached the desired temperature (600 oC – 790 oC). ¾ Annealing for 4 min to 5 min.

optical fiber

thermocouple

oven

optical fiber

SEM image before annealing

15 nm Au film on optical fiber endface

Courtesy of Lídia Ágata de Sena (INMETRO)

optical fiber

SEM image after annealing

Courtesy of Lídia Ágata de Sena (INMETRO) optical fiber

Au nanoparticles on the annealed fiber surface can be seen as white spots randomly distributed 15 nm Au film on optical fiber endface annealed for 5 min at 700 oC



Setup for spectrum acquisition (transmission) 2

1 white light source

photomultiplier with monochromator

3 computer

2 1

optical fiber (transmission)

3

Optical Transmission Spectrums (transmission setup) ¾

The absorption peak at ~ 535 nm is evidence of LSPR on the annealed fiber. Au not annealed Au annealed

Optical Transmission (A.U.)

1,6 1,4

15 nm Au film on optical fiber endface annealed for 5 min at 700 oC

1,2 1,0 0,8 0,6 0,4 400

450

500

550

600

Wavelength (nm)

optical fiber (transmission)

650

700



Sensor: reflection setup 1 white light source

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A reflection setup is more practical for sensing.

2 x 1 coupler

nanoparticles

2 photomultiplier with monochromator

optical fiber (reflection)

3 computer

Optical Transmission Spectrums (reflection setup) ¾

The absorption peak at ~ 516 nm is evidence of LSPR on the annealed fiber 6 nm; 4 min @ 720 oC). Au not Annealed Au annealed


1,2 1,0 0,8

6 nm Au film on optical fiber endface annealed for 4 min at 720 oC

0,6 0,4 0,2 400

450

500

550

600

Wavelength (nm)


650

700

Optical Transmission Spectrums (reflection setup)

Optical transmission (A.U.)

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Reflection setup allows for spectrum acquisition during the annealing. Spectrums during 2nd and 4th minute seem alike. Au not annealed During annealing 2nd minute During annealing 4th minute Au annealed

1,2 1,0 0,8

Absorption peak at ~ 516 nm (6 nm; 5 min @ 675 oC)

0,6 0,4 0,2 400

450

500

550

600

Wavelength (nm)


650

700

Optical Transmission Spectrums (reflection setup) Spectrum acquired during 1st minute indicates that nanoparticles are formed when the fiber is inserted into oven. 1,1

Absorption peak at ~ 520 nm (6 nm; 4 min @ 790 oC)


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1,0 0,9

Au not annealed 1st minute annealing 3rd minute Au annealed

0,8 0,7 0,6 0,5 0,4 0,3 0,2

Fiber inserted into oven


400

450

500 Wavelength (nm)

550

600

Temperature dependence (reflection setup) Normalized optical transmission decreases with temperature.


0,95

Decrease in temperature

o 660 C o 570 C o 450 C o 385 C o 235 C o 175 C o 100 C

0,90 0,85

Measurements taken as oven temperature decreased

0,80 1,00

0,75 0,70 500

520

540

Wavelength (nm)



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o 160 C o 240 C o 350 C o 415 C o 530 C o 680 C

Increase in temperature

0,95 0,90

560

0,85 0,80

Measurements taken as oven temperature increased

0,75 0,70 0,65 500

520

540

Wavelength (nm)

560

Temperature dependence (reflection setup) Normalized optical transmission at the absorption wavelength (520 nm). Optical Transmission @ 520 nm

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0,85

0,80

T increase T decrease

0,75

0,70 100

200

300

400

500

Temperature (oC)


600

700

Surrounding n dependence (reflection setup) ¾

Blue-shift absorption peak as refractive index increases? Why is it not red-shifted? Normalized Optical Transmission (A.U.)

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1,10

RI water = 1.33 RI 30% sugar solution = 1.38

1,05 Curves seem to shift to the left as n increases

H2O 10% sugar in H2O

1,00

17% sugar in H2O 23% sugar in H2O

0,95

28% sugar in H2O 33% sugar in H2O

0,90

460

480

500

Wavelength (nm)


520



Conclusions ¾

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To the best of our knowledge, this is the first reflectionbased LSPR fiber optic sensor with this configuration (coupler; Au evaporated and annealed). Nanoparticles were formed during the first few seconds of annealing (no need to anneal for 4 or 5 min). Absorption peak did not shift with different annealing temperatures (600 oC – 790 oC). Optical transmission decreases with temperature ⇒ temperature sensor or temperature compensation necessary. Blue-shift absorption peak as refractive index of surrounding medium increases (multimode fiber)?

What's next: transmission setup ¾

Temperature stability has been improved ⇒ more accurate temperature dependence can be acquired.

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Need to better understand LSPR absorption behavior when refractive index of surrounding medium increases. Is it blue-shifted? If so, why is it not red-shifted?

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Tests with different gases (Co2).

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Improve Au adherence to fiber tip (bulk glass).

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Increase LSPR signal ⇒ less sensitive detection system; higher sensing resolution.

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Nanoparticles: try other metals.

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Functionalizing of sensor to detect specific analytes.

THANK YOU FOR YOUR ATTENTION! ¾ Acknowledgements: ¾Lídia Ágata de Sena (INMETRO) ¾ Francisco Smolka (Optolink) ¾Rede de nanofotônica (Nanofoton)