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New Photonic Band Gap Materials via the Synthesis and Assembly of

Dielectric-Metal-Dielectric Particles

Bartosz IżowskiAdvanced Materials & Surfaces Group

Warsaw University of TechnologyPoland

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“ If only were possible to make materials in which electromagnetically waves cannot propagate at certain frequencies, all kinds of almost-magical things would happen”

Sir John Maddox, Nature (1990)

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Outline

1. Introduction

• Photonic crystals

• Opals in nature

2. My project

• Synthesis

• Research

3. Results

4. Conclusions

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Introduction

Photonic Crystals – semiconductors of lightSemiconductors

Atomic length scalesNatural structuresControl electron flow

Photonic Crystals

Length scale ~ Artificial structuresControl e.m. wave propagation

Photonic Crystals periodic dielectric structures• interact resonantly with radiation with wavelengths comparable to the periodicity

length of the dielectric lattice• dispersion relation strongly depends on frequency and propagation direction

Periodic array of atoms

Periodic variation of dielectric constant

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Introduction

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22)(max sin2

effnd hklBragg-Snell’s law :

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My project

1. Synthesis

• Silica particles – Stöber method

• Silica @ silver

• Silica @ silver @ silica

2. Manufacturing of Photonic Crystals – controlled evaporation self-assembly

3. Reflectance / Transmittance results

4. Conclusions

GOALStudies of the photonic crystal properties (band gap properties)

in dielectric-metal photonic crystal systems

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Synthesis

Face-Centered Cubic Lattice

Controlled Evaporation self-assembly method

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Synthesis

• Silica colloids were prepared using the Stöber synthesis

Si(OC2H5)4 + 4 H2O Si(OH)4 + 4 C2H5OH

Si(OH)4 → SiO2↓ + 2 H2O

In ethanol, in presence of NH3

• These colloids are charged, stabilised in water and in alcohols by electrostatic interactions•Zeta potential = - 55.3 mV

EtOHNH4OH

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Synthesis

[NH4OH] ml

Stirring time [hrs]

Particle size [nm]

Standard deviation [%]

1.75 2 108 12.92.5 3 151 135 1 290 6.55 2 272 7.95 3 297 6.36 2 411 7.2

100 150 200 250 300 350 400 4501

2

3

4

5

6411,4

272,2

289,8

297,8

151,2

108,3

[ NH 4O

H ]

mL

Particle size [nm]

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Results

Size = 411 nmStd.dev = 7.2%

Size 108 nmStd.dev = 12%

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Silver shell preparation

core @ shell preparation

Preparation of silver nanoparticles decorating of silica surface

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SampleZeta

potential [mV]

pH

Silica - 55.3 9.98

silica@PEI 35.7 8.8

Silver NP. - 50.4 7.84

silica@silver 26.3 9.58

0

100000

200000

300000

400000

500000

600000

700000

-200 -100 0 100 200

Tota

l Cou

nts

Zeta Potential (mV)

Zeta Potential Distribution

Record 75: BI4 1 Record 76: BI4 2 Record 77: BI4 3

0

100000

200000

300000

400000

-200 -100 0 100 200

Tota

l Cou

nts

Zeta Potential (mV)

Zeta Potential Distribution

Record 95: BI39+PEI 1 Record 96: BI39+PEI 2 Record 97: BI39+PEI 3

0

100000

200000

300000

400000

500000

600000

700000

-200 -100 0 100 200

Tota

l Cou

nts

Zeta Potential (mV)

Zeta Potential Distribution

Record 99: BI41-DAP 1 Record 100: BI41-DAP 2 Record 101: BI41-DAP 3

silica

silica@PEI

silica@silver

Zeta potential

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Formaldehyd reduction of silver-amine complex into the existing silver nanoparticles

Silver shell growth

Electroless plating

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Silica outer shell preparation

core @ shell @ shell preparation

1,3 – Diaminopropane (DAP)N,N-Dimethyldodecylamine (DMDDA)H2O / EtOH (1:4)TEOS Silica @ silver @ silica particles

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Zeta potential

sampleZeta

potential [mV]

pH

silica@silver 26.3 9.58

silica@silverDAP

9.01 7.93

silica@silverDAP - DMDDA

8.13 7.7

silica@silver@silica 19.5 9.05

0

100000

200000

300000

400000

500000

600000

700000

-200 -100 0 100 200

Tota

l Cou

nts

Zeta Potential (mV)

Zeta Potential Distribution

Record 99: BI41-DAP 1 Record 100: BI41-DAP 2 Record 101: BI41-DAP 3

0

100000

200000

300000

400000

-200 -100 0 100 200

Tota

l Cou

nts

Zeta Potential (mV)

Zeta Potential Distribution

Record 103: BI41-DAP-DMDDA 1 Record 104: BI41-DAP-DMDDA 2Record 105: BI41-DAP-DMDDA 3

0

100000

200000

300000

400000

500000

600000

700000

-200 -100 0 100 200

Tota

l Cou

nts

Zeta Potential (mV)

Zeta Potential Distribution

Record 91: BI44 CSS 1 Record 92: BI44 CSS 2 Record 93: BI44 CSS 3

silica@silver - DAP

silica@silver@silica

silica@silver – DAP - DMDDA

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Crystallization by controlled evaporation self-assembly method

H2O / EtOH 60°C

silica@silver film

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Arrangement

bare silica opal silica@silver opal

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Optical properties

300 400 500 600 700 8000.0

0.2

0.4

0.6

0.8

1.0

Abs

orba

nce

Wavelength (nm)

Silver NP Silica@silver Silica@silver shell Silica@silver@silica

UV-vis absorption spectra of nanoparticles.

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Optical properties

Reflectance and Transmittance spectra of bare silica opal measured at 10 ° incidence to the normal

600 8000

20

40

60

80

100

% T

% R

Wavelength (nm)

T R

10 ° to the normal

732

nm

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Optical properties

Reflectance spectra of bare silica opal (10 to 60 are the angle of incidence of light to the normal)

500 600 700 800 9000

20

40

60

80

100

120

% R

(A. U

.)

Wavelength (nm)

10 20 30 40 50 60

Bragg-Snell’s Law λmax = 2d111 (neff – sin2θ)1/2

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Optical properties

Reflectance spectra of silica@silver opal measured at incident angles from 10 to 60 degrees to the normal

600 8000

20

40

60

80

% T

% R

Wavelength (nm)

R T

10 ° incidence to the normal

805

nm

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Reflectance spectra of silica@silver opal measured at incident angles from 10 to 60 degrees to the normal

600 8000

10

20

30

% R

(A. U

.)

Wavelength (nm)

10 20 30 40 50 60

Optical properties

Bragg-Snell’s Law λmax = 2d111 (neff – sin2θ)1/2

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Conclusions

• Prepared monodispersed silica nanoparticles

• Prepared silver decorated silica nanoparticles

• Attempted silica@silver@silica CSS particles

• Characterized different steps of the CSS particle formation by ZP

measurements, UV-vis absorption spectroscopy and TEM analysis

• Photonic crystals of these materials are prepared and photonic band gap

properties are compared.

• Photonic band gap of silica@silver particles show a red shift from that of

bare opal.

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Acknowledgements

Supervisor: Prof. Martyn Pemble

Co-supervisor: Dr. Sibu C. Padmanabhan