First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

The assembling of semiconductorand metal nanocrystals

Nikolai Gaponik, Alexey Shavel, Lehui Lu,Alexander Eychmüller

Institute of Physical Chemistry and Electrochemistry,Technical University of Dresden

01062 Dresden, GERMANYInstitute of Physical Chemistry, University of Hamburg

20146 Hamburg, GERMANY

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Content

Introduction

Synthesis and characterization of nanocrystals

Formation of nanocomposites:•LbL assembly•Chemical conjugation•Solvent controlled precipitation•Electrostatic assembly and chemical plating•1D assemblies

Conclusions

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Why nanocrystals?

•Size-dependent physico-chemical properties

•High photoluminescence quantum yields

•Narrow emission (color purity)

•Broad continous absorption bands

•High stability against photodegradation

•Solution processable photonics and optoelectronics

•Specific: solubility in water and compatibility withcommon buffers at physiological concentrations

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Why assembly, self-assembly, templating?

There is a lack of methods allowing controllableinsertion of nano-objects (particles, molecules,composites, etc.) in photonic and optoelectronicmicro(nano)structures

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

H2Te

Al2Te3

N2

H2SO4

H2Te, N2

Cd(ClO4)2, R-SH

Heating

CdTe S

SS

S S

R

R

R

RR

Main Goals:•stable, soluble, highly luminescent NCs•variable particle size•narrow size distribution•reproducibility•large-scale synthesis

Nanocrystals:CdSe, CdTe, CdHgTe, HgTe, ZnSe, ...

2.5 2.0 1.5 1.0

500 1000 1500 20000.0

0.5

1.0

750

HgTeCdHgTeCdTe

PL

inte

nsity

[a.u

.]

Wavelength [nm]

Photon Energy [eV]

Photoluminescence of NCs:

Aqueous Synthesis of Nanocrystals

J.Phys.Chem.B 2002, 106, 7177

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

NanoLett 2002, 2, 803

CdTe/PLMA composite:

0,0

2,0x107

4,0x107

6,0x107

8,0x107

400 500 600 7000,0

0,1

PL QE = 12%

CdTe in water in toluene

Abs

orba

nce

[a.u

.]

Wavelength [nm]

PL

inte

nsity

[cou

nts]

From water to toluene:

Phase Transfer of Nanocrystals

HgTe NCs in toluene:

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

LPPP/HgTe Infrared LED

800 1000 1200 1400 1600 1800

0,0

0,2

0,4

0,6

0,8

1,0

1,2EL:

0.0 V 10.0 V 12.0 V 15.0 V

PL-red line

PL,

EL

inte

nsity

, a.u

.Wavelength, nm

X = CH3

R = C6H13

R`= C10H21

LPPP:

Chem. Phys. Chem. 2004, 5, 1435

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Layer-by-layer (LbL) assembly ofnanocrystals

PDDA- poly(diallyldimethylammonium) chloride

Assembly of PDDA/ZnSe film:PL and evolution of film absorption

1. Positivepolyelectrolyte

2. Wash

3. Negativenanoparticles

4. Wash

Procedures 1-4 can be repeated n-times

=

J.Phys.Chem.B 2004, 108, 5905

300 400 500 6000,00

0,01

0,02

0,03

0,04

0,05

Abs

orpt

ion

Wavelength [nm]

350 400 450

Wavelength [nm]

PL in

tens

ity [a

.u.]

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Transfer rate: (254ps)-1

Appl. Phys. Lett. 2004, 84, 2904Transfer rate: (71ps)-1

Small 2005, 1, 392

FRET in NC layers

LbL films:Direct electrostaticassemblies:

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Selective LbL modification of photoniccrystal heterolayers

Scheme of LbL assembly and TEMimage of modified polymer beads

Day light

UV light

J.Appl.Phys. 2004, 95, 1029phys.stat.sol. (a) 2003, 197, 662Synth. Metals 2003, 139, 701

300/240 nm hetero-opal. Bottomlayer is modified with CdTe NCs

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

LbL- assembly and solvent controlledprecipitation on colloidal particles

1

2

3

4

5

6

7

1. Polymerbeads in

water

2. Adsorptionof opposite

chargedpolyelectrolyte

molecules

3. Centrifugation

4a, 7a. Removingof supernatant. 4b, 7b. Particlesredispersion inpure solvent

(3 times)

5. Adsorption ofnanocrystals

6. Centrifugation

b

b

a

a

5µmAdv. Mater. 2001, 13, 1684

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Covalent linking of nanocrystals to thesurfaces

400 500 600 700 800 9000.00

0.02

0.04

0.06

0.08

0.10

Abs

orpt

ion

Wavelength [nm]

0.0

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

PL

inte

nsity

[a.u

.]

SEM image of asingle modifiedglass sphere

Optical properties of modified microspheres

ChemPhysChem 2005, 6, 449Eur. J. Inorg. Chem. 2005, 3613

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Confocal image

Modified colloidal particlesTEM and HRTEM images

Semicond. Sci. Technol. 2003, 18, 914Appl. Phys. Lett. 2003, 83, 2539J. Appl. Phys. 2004, 96, 6761.

Coupling of NCs emissionwith the WGM oscillations of

the microsphere:

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Phys. Rev. A 2004, 70, 051801J. Appl. Phys. 2004, 96, 6761

Photonic molecules

D = 1.98 µm

D = 1.99 µm

WGM from single spheres:

Coupled spheres:

Controllable allignment:

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Individual modified colloidal particles -bright subwavelength light sources

Confocal image of a 150 nm latexsphere modified with NIR-emitting

(PL max ca. 1300nm) HgTe NCs

Fluorescence of 468 nm latexbeads modified with red-emitting (PL max 605 nm) CdTeNCs

Adv. Mater. 2001, 13, 1684Appl. Phys. Lett. 2004, 84, 4732

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Beads modified with CdTe NCs forFRET-SNOM application

Schematic of the setup

SEM imagesample labelledwith acceptor

The enhanced acceptor emissionis detected to obtain an imagewith subwavelength resolution

J.Phys.Chem.B 2004, 108, 14527

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Microencapsulation of Nanocrystals

Core particles:MF, MnCO3

Polyelectrolytes:Synthetic: PAH, PSSBiocompatible: Alginic acidsodium salt, Protamine sulfate,Dextrane sulfate, Chitosan.

Nanocrystals:CdTe, CdHgTe, HgTe,emitting from 500 to 1100nm, Fe3O4 magneticparticles

Adv. Mater. 2002, 14, 879Small 2005, 1, 194

Langmuir 2004, 20, 1449 NanoLett. 2003, 3, 369

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

ChemPhysChem 2004, 5, 1600

1D self-assemblies: Nanowires forNanotechnology

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Gold-coated 3D ordered colloidal crystalsSubstrates for SERS

Scheme of the fabricationprocedure:

Opal with assembled Au NCs:Chem. Mater. 2005, in press

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Typical SiO2 template (a)and resulting Au/Pthollow spheres (b,c)

Macroporous Au/Ptstructure:

Disordered hollow Au/Pt spheres(a) and semispheres (b)

Selective Fabrication of Ordered BimetallicNanostructures with Hierarchical Porosity

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

1. Synthesis and post preparative treatment of luminescent NCs :•PL QE in solutions of up to 60%•PL in UV-blue, visible and NIR spectral regions•compatibility with non-polar (toluene, chloroform etc.) and polar organic(DMF, THF, DMSO etc.) solvents

2. Various composite materials with luminescent NCs:•core-shell micro/nano particles (silica, glass) with NC shells•modified planar and 3D structures including layered opal heterostructures•polymers with incorporated NCs•microencapsulated NCs•self-assembled nanowires•3D structures with hierarchical porosity

3. Potential applications in photonics, LED, optical labelling,...

Summary

First annual workshop in “Advances in Nanophotonics”Heraklion, Crete, Greece. 10th-13th October 2005

Acknowledgements

Trinity College DublinYu. RakovichJ. DoneganYu. Volkov S. Mitchell

LMU- MunichA.L.RogachJ. FeldmannD. S. KoktyshA. S. SushaT. Franzl

MPI-GolmG. SukhorukovI. RadtchenkoM. GerstenbergerYu. Fedutik

Financial support:EU NoE PHOREMOSTEU-Project FUNLIGHTDFG SPP 1072DFG SPP 1113NATO CLG

Tyndall Insitute, CorkS. G. RomanovC. M. Sotomayor-Torres

ETH-ZurichV. SandoghdarB. C. BuchlerP. Olk

HU BerlinO.BensonS.GötzingerF.Müller

University ofWuppertal(BUW)U. Scherf

IBM New YorkD. V. Talapin

University of HamburgH. WellerA. Kornowski

University of MunsterL. ChiL. Zhang