EP Thesis Defence 2016

Study of the Size-Reduction Effect on the Photophysical Properties of [Ru(bpy)3][NaCr(ox)3]

Nano-Crystals and Functionalization of their Surface

Elia Previtera

November 24, 2016

Département de Chimie Physique, Université de GenèveHauser Group

Nano-Size Materials

Applications: Medicine, Bio-imaging, IT, Solar-Energy Harvesting and Conversion, Lasers, Catalysis, Displays …..

Quantum Dots: tunable emission wavelength…...

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Size

1

SIZE DEPENDENT PROPERTIES

5 nm

10 nm

15 nm

20nm

80nm

90nm

100nm

Nano Today 2011.

Nano-Size Materials

2The New York Times article of February 22, 2005.

Nano-Size Materials

At least one dimensions between 1 and 100 nmXAt least one physical or chemical size-dependent property

M.L. Grieneisen, M. Zhang, Small 2011, 7, No. 20, 2836-2839.

What is What in the Nanoworld: A Handbook on Nanoscience and Nanotechnology 2012.

3

Energy Transfer and Migration

..

... .. .

Homo-Energy Transfer or Energy Migration

Hetero-Energy Transfer..

..

. .. .

..

. ..

. ..

..

... .. .

4

Radiative Energy Transfer and Migration

Acceptor or DonorDonor*

S0

S1

S0

S1

hν hν’

5

Non-radiative Energy Transfer and Migration

HOMO

LUMO

Förster

AcceptorDonor*

Dexter

AcceptorDonor*

kEETF ∝

1RDA

⎛

⎝⎜⎜

⎞

⎠⎟⎟

6

kEETEx ∝exp −

2RDARDA0

⎛

⎝⎜⎜

⎞

⎠⎟⎟

HOMO

LUMO

10 Å < RcF < 80 Å 1 Å < Rc

Ex < 10 Å 6

Non-radiative Energy Transfer and Migration

ΩDA= gD(E)gA(E)dE∫

Spectral overlap integral

ΩDA

λ

Emi(A)Emi(D)Abs(D) Abs(A)IgD gA

7

Energy Transfer and Migration in Natural Antennae

6 CO2 + 6 H2O C6H12O6 + 6 O2Respiration

Photosynthesis

Sunlight Energy stored

Energy storedEnergy released

Nature, 1995, 374, 517. 8

Energy Transfer and Migration in Natural Antennae

Photosynthetic unit of Rhodopseudomonas acidophila

Nature, 1995, 374, 517. 9

Reference System: Microcrystals of [Ru(bpy)3][NaCr(ox)3]

Anionic Chiral 3D Polymeric Oxalate Networks

[NaCr(ox)3][Ru(bpy)3]

Na++

D3

[Cr(ox)3]3-

Crystal system

Cubic

Z = 4

Chiral Spacegroup

P213

Site symmetry ofall metal ions

C3 S. Decurtins et al., J. Amer. Chem. Soc. 116 (1994) 9521. 10




Na++

D3

[Cr(ox)3]3-

Crystal system

Cubic

Z = 4

Chiral Spacegroup

P213



3D oxalate network: [Ru(bpy)3][NaCr(ox)3]

[Ru(bpy)3]2+: antenna

Oxalate Networks to Study Photo-Induced Energy Transfer

Bulk: efficient energy migration in the 2E state of Cr(III)

[NaCr(ox)3]2- network: energy migration

Is there any influence of the crystal size on the energy migration within the 2E state of the [Cr(ox)3]3- chromophores?

hν

Energy Transfer

Milos. M. et al., Coor. Chem. Rev., 252, 2000, 2540 13


Tetrahedral microcrystalline particles with side length 4 µm

S. Decurtins et al., J. Amer. Chem. Soc. 116 (1994) 9521.

5 µm

14

How to Synthesize Nanocrystals?Ø  Synthesis by the Reverse Micelles technique

Aqueous phase: Solubilization of [Ru(bpy)3]Cl2.6H2O and K3[Cr(ox)3].3H2O

Surfactant: Sodium bis(2-ethylhexyl) Sulfosuccinate (AOT)

Solvent: n-Heptane

TEM à Tetrahedral Shape of Nanocrystals

Centrifugation and washing in EtOH

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Size Controlled Micro- and Nanocrystals

Tetrahedral Shape of NanoparticlesImageJ

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Large Size Distribution

16

1000 nm

Size & Volume Weighted Distribution

Iluminescence ≈ a3a

17Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979

< Size > = ΣaNumber of NPs < Size Signal > = Σ(a x a3)

Total a3

Size Controlled Micro- and Nano-crystals


Ø  Modification of the water-to-surfactant ratio (Wo)

Wo =[H2O]

[Surfactant]Size Control of final product!

Wo= 2 Wo= 5 Wo= 8

2.5 µm MPs changing Wo and lowering the concentration of reactants inside micelles (Wo= 8 and 0.025 M)

Previtera E. et al., Adv. Mater. 2015, 27, 1832. 18

Size Controlled Micro- and Nanocrystals


2θ = 5.8°

140 nm

220 nm

360 nm

450 nm

670 nm

2.5 µm

4 µm

Previtera E. et al., Adv. Mater. 2015, 27, 1832.

19

Chromium (III): d3 in C3 Symmetry

Ligand field states

4A2(t2g3)

4T2(t2g2eg

1)

4A2

2E

Oh C3 + Hso

R1 R2

D (2E) = 13.7 cm-1

D (4A2) = 1.3 cm-1

hν hν

Spin-flip Δr ≈ 0

t2g → eg Δr ≈ 0.1 Å2E(t2g

3)

ISC

t2g

eg

t2g

egt2g

eg

E

RCr-O

Ms = ± 3/2

Ms = ± 1/2

20

Solid State Spectroscopy Background Homogeneous line width and inhomogeneous band broadening

Lorentz ian w i th the homogeneous linewidth

Γhom2E

4A2

R1

D

A perfect crystal

Electronic origin of Chromium (III) Andreas Hauser, Lecture Notes. 21

Solid State Spectroscopy Background Homogeneous line width and inhomogeneous band broadening

Lorentz ian w i th the homogeneous linewidth

Γhom2E

4A2

R1

D

A perfect crystal A real crystal

Electronic origin of Chromium (III)

Gaussian profile with the i n h o m o g e n e o u s b a n d broadening

Γinh

Andreas Hauser, Lecture Notes. 22

Excitation Spectra of Cr3+ R-Lines


Luminescence Spectra


Solid State Spectroscopy Background

Laser selective excitation

non-resonant fluorescence

2E

4A2

R1

D

resonant fluorescence

In the absence of any other processes only the excited subset emits.

The principle of Fluorescence Line Narrowing Spectroscopy (FLN)

Andreas Hauser, Lecture Notes. 26

Solid State Spectroscopy Background Fluorescence Line Narrowing Spectroscopy Setup

27

FLN Spectra

Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979

Ø Energy Transfer Core à Surface

28

FLN Spectra across the R1 Absorption


Size: 140 nm

Ø Smaller numbers of members in the FLN multiline pattern at lower energy29

FLN Spectra across the R1 Absorption


Size: 670 nm Size: 2.5 µm

Ø Smaller numbers of members in the FLN multiline pattern at lower energy

30

ZFS as Function of FLN Excitation Wavelength


Ø Crystalline environment of the [Cr(ox)3]3- chromophores at the surface is slightly different to that of the complexes in the bulk

31

Time Resolved FLN Spectra


hν’

Energy migration inside 2E of Cr(III)

Cr3+

2E

4A2

hν

4A2

2E

Cr3+ Cr3+ Cr3+

4T2

Core Surface

32

Luminescence Decay Kinetics

Ø  Directional Energy Transfer from the Core to the Surface

Previtera E. et al., Adv. Mater. 2015, 27, 1832.Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979

Multi line pattern decay

(at 14394 cm-1)

τ4 µm = 1.3 msτ2.5 µm = 155 µsτ670 nm = 132 µsτ140 nm = 57 µs

Broad band rise to maximum intensity

(at 14371 cm-1)

220 µs for 2.5 mm 180 µs for 670 nm 60 µs for 140 nm

Broad band rise to maximum intensity

(at 14351 cm-1)

400 µs for 2.5 mm 360 µs for 670 nm 180 µs for 140 nm

33

l

How far does the energy travel?

Ø  Average distance travelled by the energy is of the order of a few hundreds nm

RC resonant process à up to 30 Å

Ø  l = 140 nm à d = 30 nm 10 steps for energy migration Core à Surface

Ø  l = 670 nm à d = 138 nm 46 steps for energy migration Core à Surface

Ø  l = 2.5 µm à d = 510 nm 170 steps for energy migration Core à Surface

Previtera E. et al., Adv. Mater. 2015, 27, 1832.Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979 34

Energy Transfer Mechanism


1A1[Ru(bpy)3]2+

35

<< 1 µs

< 1 ns

Conclusions

•  Size-controlled micro- and nano-crystals of [Ru(bpy)3][NaCr(ox)3] •  Directional Energy Transfer from the Core to the Surface•  Average distance travelled by the energy is of the order of few hundreds nm

Previtera E. et al., Adv. Mater. 2015, 27, 1832.Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979 36

l

Control of the surface state

●  Growth of oxalate network shell with cavities filled with energy acceptor [Cr(bpy)3]3+

●  Direct chemical grafting of Ln3+ complexes (Ln3+ = Er3+, Eu3+, Yb3+)

37

Growing an Oxalate network shell

•  Core: 670 nm NPs [Ru(bpy)3][NaCr(ox)3] and[Ru(bpy)3][NaAl(ox)3] = RuCr, RuAl

•  Core-Shell: [Ru(bpy)3][NaAl(ox)3]@[Ru(bpy)3][NaCr(ox)3] =RuAl@RuCr [Ru(bpy)3][NaCr(ox)3]@[NaCr(ox)3][Cr(bpy)3]ClO4 =RuCr@CrCr [Ru(bpy)3][NaAl(ox)3]@[NaCr(ox)3][Cr(bpy)3]ClO4 =RuAl@CrCr

38


PUMP

Reactants Sizenm

[Ru(bpy)3][NaMIII(ox)3]MIII = Cr3+, Al3+

670

(NH4)3[Cr(ox)3] -

[Ru(bpy)3]Cl2.6H2O -

[Cr(bpy)3]ClO4 -

NaCl -39


Surface change•  Roughness•  Round corners

Bigger average size

RuAl RuAl@RuCr

RuCr RuCr@CrCr

RuAl RuAl@CrCr

40


41


Ø Energy Transfer Core à Shell?

42


43


44

Conclusions •  It is possible to grow an Oxalate network shell of good crystalline quality

containing in its cavities the energy acceptor [Cr(bpy)3]3+.

•  No evidence of energy transfer towards the shell in RuCr@CrCr was found.

45

Direct chemical grafting of Ln3+ complexes

Up-Conversion NanoparticlesNature Materials 2011. 46


365 nm

a) b)

[Rh(bpy)3][NaAl(ox)3]ClO4 + [Eu(hfac)3dig] [Rh(bpy)3][NaAl(ox)3]ClO4@[Eu(hfac)3] + dig

Preliminary Test

47

hfac = hexafluoroacetylacetonate dig = diglyme or bis(2-methoxyethyl)ether


[Rh(bpy)3][NaAl(ox)3]ClO4 + [Eu(hfac)3dig] [Rh(bpy)3][NaAl(ox)3]ClO4@[Eu(hfac)3] + dig

48


Reactants Sizenm

[Ru(bpy)3][NaCr(ox)3]RuCr

220

[Eu(hfac)3dig]Eu

-

[Er(hfac)3dig]Er

-

[Yb(hfac)3dig]Yb

-

RuCr + [Ln(hfac)3dig] RuCr@[Ln(hfac)3] + dig

49

hfac = hexafluoroacetylacetonate dig = diglyme or bis(2-methoxyethyl)ether


50

ZFS as Function of FLN Excitation Wavelength

51


Ø Energy Transfer Core à [Ln(hfac)3]

52

Down-Converted Luminescence

53


54


55


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•  Improving of the NPs’ surface.

•  Quenching of the broad band luminescence.

•  Efficient excitation energy transfer from the 2E excited states of the [Cr(ox)3]3- ions located at the surface towards the lanthanides complexes grafted at the NPs’ surface.

•  Good indication of down conversion luminescence related to the lanthanides transitions 4I9/2à4I15/2 and 2F5/2à2F7/2 for Erbium and Ytterbium.

•  No up-conversion luminescence.

Conclusions

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Outlook•  Direct chemical grafting of [Gd(hfac)3dig]

6P3/25/27/2

8S7/2

3220

0 cm

-1

•  Enhancing of the lifetime of the surface [Cr(ox)3]3- chromophores?•  Would direct excitation of [Gd(hfac)3] complexes grafted at the surface give

directional energy transfer towards the chromophores located at the surface or further into the core? 58

•  This work contributes to the expansion of the basic knowledge about nano-size materials.

•  The energy can travel few hundreds of nanometers in NCs. This important basic knowledge can be useful for future applications in solar energy harvesting and conversion.

•  This work demonstrates that also particles with sizes bigger than 100 nm can show size-dependent properties.

General Conclusions

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Acknowledgements Prof. HauserDr. Lawson DakuDr. ChakrabortyDr. SuffrenDr. SunTeresa Delgado PerezAndrea MissanaCatherine LudyNahid JeddiPatrick BarmanDominique LovyLaurent Devenoge

Hauser’ Group:

Prof. DecurtinsProf. HagemannDr. Tissot

Jury members:

Dr. MouryDr. OlchowkaDr. BierwagenManish SharmaDaniel SethioAngelina Gigante

Hagemann’ Group:

Prof. Piguet Dr. Nozary

Piguet’ Group:

Dr. Varnholt Dr. Lawson DakuDr. ChakrabortyDr. MouryAndrea MissanaManish Sharma

Corrections:

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Thank you for your attention!

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EP Thesis Defence 2016

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