1

A. Chiappini, M. Ferrari

CNR-IFN, CSMFO Lab., Via alla Cascata 56/c, Povo, 38123 Trento, Italy.

Cristalli fotonici colloidali 3D e loro applicazioni

nel campo della sensoristica.

CNR - Istituto di

Fotonica e

Nanotecnologie

CHARACTERIZATION and DEVELOPMENT of

MATERIALS for PHOTONICS and OPTOELECTRONICS

Laboratory

CSMFO Lab. www.science.unitn.it/~gcsmfo/

Società Italiana di Fisica, XCVII Congresso Nazionale, L’Aquila, 26 - 30 Settembre, 2011

2

OUTLINE

Introduction

Fabrication methods

Applications:

Strain sensor

SERS substrate

Conclusions

3

All-Optical Micropolis

Introduction

“Joannopoulos’ vision”

Why Photonic Crystals?

Reduce the dimension of optical functions,

increasing the density of the functions in the integrated circuits

“comunication of the data occurs using just all-optical device. “

4

Introduction

3D Photonic Crystals

√ S. Y. Lin Nature 394, 251, (1998);

Nanolitography

√ M. Campbell Nature 404, 53, (2000);

Holography

√ M. Deubel, Nature Materials 3, 444, (2004)

Direct Laser Writing

These techniques are based on highly expensive and sophisticated equipment

5

What are colloidal crystals?

3D Photonic Crystals

Low cost

“Easy”

Self-Assembling

colloidal nano-microspheres

relative easiness of preparation

associated with their manufacture

6

Silica Spheres

The reaction takes place at room temperature and we can control the particle size

through the concentration of a single reactive.

o [TEOS] = 0.22 M

o [NH3] = 1.0 M

o [H20] = 15.0 M

Molar Concentrations

high uniformity of silica spheres(less than 5% of dispersion in diameter)

the dimension of :~255nm

Stober Methods

OHHCOHSiOHHOCSi 5242452 44

OHSiOOHSi 224 2

7

PS monosize spheres

Single-stage

polymerization processbased on formation and

growth of polymeric nuclei

dispersed in an emulsion

constituted by water, styrene,

potassium persulfate (KPS)

and sodium docecyl sulfate

(SdS).

Microemulsion

Control the particle size through the concentration of

sodium docecyl sulfate.

Range 150 ÷ ~ 1000 nm

8

Techniques

Self Assembly techniques

Vertical Deposition

A. Chiappini, C. Armellini, A. Chiasera, M. Ferrari, Y. Jestin, M. Mattarelli, M. Montagna, E. Moser, G. Nunzi Conti, S. Pelli, G.C.

Righini, M. Clara Gonçalves, Rui M. Almeida, "Design of photonic structures by sol–gel-derived silica nanospheres" Journal of

Non-Crystalline Solids 353 (2007) pp. 674–678.

9

hexagonal alignment which

corrisponds the to <111> planes

square packing associated with <100> planes

Properties of colloidal crystals

Exploit the property of NPs to self-assemble in ordered structure

A. Chiappini, C. Armellini, A. Chiasera, M. Ferrari, Y. Jestin, M. Mattarelli, M. Montagna, E. Moser, G. Nunzi Conti, S. Pelli, G.C.

Righini, M. Clara Gonçalves, Rui M. Almeida, "Design of photonic structures by sol–gel-derived silica nanospheres" Journal of Non-

Crystalline Solids 353 (2007) pp. 674–678.

10

Pseudo Band Gap

Properties of colloidal crystals

Γ – L space

Direct colloidal crystals

It’s possible tune the position of the Stop bandvarying the dimension of the NPs

The arrangement in a fcc structure produces a periodic variation in refractive index

D = 236 nm

D = 225 nm

Stop-band

11

Properties of colloidal crystals

460 480 500 520 540 560 580 600 620 6400.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d R

efle

cta

nce

Wavelength (nm)

20 degree

25 degree

30 degree

35 degree

40 degree

2/122 sin816.02 effnD

Direct opal structures

0,3 0,4 0,5 0,6 0,7 0,8 0,9

0

10

20

30

40

50

60

a/

L

a)

Tra

sm

itta

nce

%

b)

Experimental

Simulation

Modified Bragg’s Law

Dd 3

2111

)1(222 fnfnn mediumNPseff

Diffraction peak

12

These heterostructures are created by using multilayer deposition

Properties of the Heterostructures

depositing on the SiO2 NPs colloidal film opal structures of PS that present different dimension in size

systems suitable for wide applications in manufacturing integrated photonic crystal chips,

such as broadband reflective mirrors and/or multi-frequency optical Bragg filters

“Exploiting”

A. Chiappini, C. Armellini, N. Bazzanella, A. Carpentiero, G.C. Righini, M. Ferrari, “Hybrid Colloidal Crystal for Photonic

Application” Proc. of SPIE Vol. 8069 80690I-1 (2011)

13

PS

SiO2

500 600 700 800 900 1000

0

10

20

30

40

50

60

70

Re

fle

cta

nce

(a

.u.)

Tra

nsm

itta

nce

%

Wavelength (nm)

C

HT

/1000

###

###

###

Optical Properties of HTs

presence of a double peak centered at about 800 and 700 nm,.

effnD 816.02

• the position of the stop bands of HT match the position of the stop band of single layers.

• this behaviour can be seen as just a superposition of the properties of each individual layer

Formation of two photonic layersoccurs and a good ordering of the structures realized is evident.

14

Direct opal used as a scaffold for formation of Inverse structure

Direct Opal as template

Infiltration

Removal of beads

Photonic Band gap

Bragg’s Law

Inverse colloidal crystal

1)

2)

3)

Scheme

15

Properties of inverse structure

Large surface area

Silica inverse structure

A. Chiappini, C. Armellini, A. Chiasera, Y. Jestin, M. Ferrari, E. Moser, G. Nunzi Conti, S. Pelli, R. Retoux, G.C. Righini,

"Er3+-activated sol–gel silica confined structures for photonic applications", Optical Materials 31 (2009) pp. 1275–1279.

Negative replica

Porous material

16

Strain sensor

SERS substrate

Possible applications

17

Strain Sensor

effnd 1112

d0

light source light detector

d()

axial elongation

tra

nsve

rsa

l

co

ntr

actio

n

Initial configuration:

Strained configuration:

polystyrene

sphere

elastometer

l

support

l

=l

l=

l

l

Material: Changing the structural color under an external stimulus

Blue shift of the wavelenght of the diffraction peak as a function of the applied strain

Recognize this by naked eyes

How it works?

18

Strain SensorExperimental validation

D. Zonta, A. Chiappini, A. Chiasera, M. Ferrari, M. Pozzi, L. Battisti, M. Benedetti, Proc. of SPIE 7292 (2009) pp. 729215-1 -

729215-10.

Initial

Applied strain

Experimental set-up

L + ΔL

L

19

Strain Sensor

Response Characterisation

D. Zonta, A. Chiappini, A. Chiasera, M. Ferrari, M. Pozzi, L. Battisti, M. Benedetti, Proc. of SPIE 7292 (2009) pp. 729215-1 -

729215-10.

450 500 550 600 650 7000

10

20

30

40

50

60

70 initial

0.5 mm elongation

1.0 mm elongation

1.5 mm elongation

2.0 mm elongation

2.5 mm elongation

3.0 mm elongation

Inte

nsity (

a.u

.)

Wavelength (nm)0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

550

555

560

565

570

575

580

585

Wa

ve

len

gth

po

stio

n (

nm

)Elongation (mm)

d111, decreases linearly

the position of the peak does not change significantly,

Inter lanar distance remains constant for the applied strain,

since the PS spheres are in contact with each other

Peak position blue shifts from 583 to 550 nm

Linear response

20

Strain sensor

SERS substrate

Metallo – dielectric structures

Possible applications

21

Idea

Unique optical properties that combine:the localized surface plasmon resonance

of Au NPs with the PBG features ofc o l l o i d a l c r y s t a l s t r u c t u r e

Chemical Sensor and SERS substrate

22

Fabrication of metallo-dielectric structures

Schematic diagram:

a) using polystyrene and silica solution, an infiltrated opal structure is obtained;

b) annealing and sintering processes form an inverse silica opal (ISO) structure;

c) functionalization of the ISO structure with 3-aminopropyltriethoxysilane

(APTES);

d) immobilization of Au Nps on silica network.

based on the realization of an inverse silica opal and immobilization of gold nanoparticles on the silica network

23

Gold nanoparticles

How to prepare?

Turkevich Method (1951)Turkevich, J.; Stevenson, P. C.; Hillier, J. Nucleation and Growth Process in the

Synthesis of Colloidal Gold. Discuss. Faraday Soc. 1951, 11, 55-75.

Reduction of Gold ion by citrate ions

+

400 450 500 550 600 650 700 750

0.0

0.2

0.4

0.6

0.8

1.0

(e)

Abso

rba

nce

Wavelenght (nm)

LSPR = 520 nm

chloroauric acid chloroauric acid

chloroauric acid

24

Structural Properties

Inverse ordered structure is still present after immersion process

hollow regions of the air spheres

(well ordered in a triangular lattice corresponding

to the (111) planes of a fcc crystalline structure)

inner dark holes

(representing the point of contact between each

templating sphere and its 12 nearest neighbors)

After 2 h immersion time

Au Nps are attached/immobilized on the network of the ISO system

After 10 h immersion time

25

Optical Properties of MDCS

Unique optical properties that combine:the localized surface plasmon resonance of Au NPs with the PBG features of colloidal crystal structure

400 500 600 700 800 900 1000 1100 1200

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

(d)

(c)

(b)

(a)

Ab

so

rba

nce

Wavelength (nm)

Au Nps Colloidal

solution

400 450 500 550 600 650 700 750

0.0

0.2

0.4

0.6

0.8

1.0

(e)

Abso

rba

nce

Wavelenght (nm)

520 nm

a) inverse silica opal

b) MDCS_1h

c) MDCS_2h

d) MDCS_4h

diffraction peakPlasmon peak

26

Raman Signal Enhancement

benzenethiol (BT) as a probe molecule 1x10-3M

MDCS systems have been tested as SERS substrate

to evaluate the efficiency of the MDCSwe have compared the Raman signal obtained for these structures with those collected :

b) on a gold film (GF) deposited by sputtering

c) on ISO spotted with a 5 µl drop of pure BT and left to dry out (ISO_BT).

using a 10 s accumulation time, incidence power 100 µW.

27

Raman Signal Enhancement

28

Conclusions

• Fabrication and Properties of opal structures

• Strain Sensor

460 480 500 520 540 560 580 600 620 6400.0

0.2

0.4

0.6

0.8

1.0

No

rma

lize

d R

efle

cta

nce

Wavelength (nm)

20 degree

25 degree

30 degree

35 degree

40 degree

• SERS Substrate450 500 550 600 650 7000

10

20

30

40

50

60

70 initial

0.5 mm elongation

1.0 mm elongation

1.5 mm elongation

2.0 mm elongation

2.5 mm elongation

3.0 mm elongation

Inte

nsity (

a.u

.)

Wavelength (nm)

400 500 600 700 800 900 1000 1100 1200

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

(d)

(c)

(b)

(a)

Ab

so

rba

nce

Wavelength (nm)

29

Acknowledgments

COST MP0702: Towards Functional Sub-Wavelength

Photonic Structures

NAOMI project “NAno on MIcro approach to a

multispectral analytical system for protein essays”

ITPAR phase II: India – Trento project for advanced

research (2008-2011).

30