ep thesis defence 2016
TRANSCRIPT
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…...
Gold Nanoparticles: tunable absorption wavelength…..
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
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. 11
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. 12
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
Reference System: Microcrystals of [Ru(bpy)3][NaCr(ox)3]
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
15
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
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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
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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
Previtera E. et al., Adv. Mater. 2015, 27, 1832. 23
Excitation Spectra of Cr3+ R-Lines
Previtera E. et al., Adv. Mater. 2015, 27, 1832. 24
Luminescence Spectra
Previtera E. et al., Adv. Mater. 2015, 27, 1832. 25
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
Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979
Size: 140 nm
Ø Smaller numbers of members in the FLN multiline pattern at lower energy29
FLN Spectra across the R1 Absorption
Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979
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
Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979
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
Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979
hν’
Energy migration inside 2E of Cr(III)
Cr3+
2E
4A2
hν
4A2
2E
Cr3+ Cr3+ Cr3+
4T2
Core Surface
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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
Previtera E. et al., Eur. J. Inorg. Chem. 2016, 1972-1979
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
Growing an Oxalate network shell
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
Growing an Oxalate network shell
Surface change• Roughness• Round corners
Bigger average size
RuAl RuAl@RuCr
RuCr RuCr@CrCr
RuAl RuAl@CrCr
40
Growing an Oxalate network shell
41
Growing an Oxalate network shell
Ø Energy Transfer Core à Shell?
42
Growing an Oxalate network shell
43
Growing an Oxalate network shell
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
Direct chemical grafting of Ln3+ complexes
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
Direct chemical grafting of Ln3+ complexes
[Rh(bpy)3][NaAl(ox)3]ClO4 + [Eu(hfac)3dig] [Rh(bpy)3][NaAl(ox)3]ClO4@[Eu(hfac)3] + dig
48
Direct chemical grafting of Ln3+ complexes
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
Excitation Spectra of Cr3+ R-Lines
50
ZFS as Function of FLN Excitation Wavelength
51
Direct chemical grafting of Ln3+ complexes
Ø Energy Transfer Core à [Ln(hfac)3]
52
Down-Converted Luminescence
53
Down-Converted Luminescence
54
Down-Converted Luminescence
55
Down-Converted Luminescence
56
• 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
57
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
59
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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