Composite films of nanoparticles by layer-by-layer deposition

1
Composite films of nanoparticles by
layer-by-layer deposition
Oxana Tchoul Department of Chemistry, Oklahoma
State University
2
Abstract

• Layer-by-layer assembly technique was performed
  to construct composite films of semiconductor
  nanoparticles.
• A film of CdTe nanoparticles with size gradient
  was produced by LBL assembly. Size-dependent
  fluorescence allowed layers of the film
  illuminate in different colors.
• The use of semiconductor nanoparticles for
  light-induced patterning is shown. A light
  irradiation is used to create luminescence
  pattern in the nanoparticles film.
• An LBL technique is applied to build a film of
  infrared emitting HgTe nanocrystals. The film has
  shown fluorescence in near-infrared region.

3
Introduction

• Layer-by-layer deposition is a simple method
  of building nanomaterials with a designed
  architecture. The method does not require
  specific conditions such as high vacuum, use of
  irradiation etc. Different compounds can be put
  in contact in one structure, facilitating a
  required interaction and tailoring physical
  properties of the material.
• The current presentation demonstrates
  techniques of assembling semiconductor
  nanoparticles into thin films. Fluorescence of Cd
  Te and CdS nanoparticles makes them possible to
  use in light-emitting, optical and high-speed
  devices.1 Infrared luminescence of HgTe
  nanoparticles can find applications in
  fiber-optical network.2 Luminescent properties
  of nanoparticles have great prospectives in
  construction optical memory and information
  devices.3

4
Layer by layer deposition
Layer-by-layer process
Schematic representation of a multilayer composite

1. Positively charged compound
2. Water rinse
3. Negatively charged compound
4. Water rinse

Observation of the film growth by UV-VIS
spectroscopy. 1
1) Rogach, A.L. Koktysh, D.S. Harrison, M.
Kotov, N.A. Chem. Mater., 2000, 12 , 1526 -1528.
5
Semiconductor nanoparticles quantum dots
2.3 nm 5.5 nm
a particle size
Size-depended fluorescence of CdSe nanoparticles.
(www.wikipedia.org)
6
NanorainbowsGraded semiconductor films from
Quantum dots.
Transmission electron microscopy
Luminescence spectra (a) exemplary CdTe NPs used
in this work and (b) thin films obtained after
the sequential deposition of five bilayers of (1)
"green", (2) "yellow" (3) "orange", and (4) "red"
CdT
Confocal microscopy 10 bilayers of "green",
"yellow", "orange", and "red" NPs (total 40)

• Mamedov, A.A. Belov, A. Giersig, M. Mamedova,
  N.N. Kotov, N.A. J. Am. Chem. Soc., 2001, 123,
  7738-7739.

7
Multicolor luminescence patterning by
photoactivation of LBL films
Photoetching Emission spectra of CdSe/CdS
core/shell particles, as prepared (1) and exposed
to ambient light for 15 days (2) and 25 days (3)
Light source 60W
72 hours
Mask (copper grid)
Film
Fluorescence and confocal microscopy (a-c)
Topography image (d). Scale bar 200 µm
Wang, Y. Tang, Z. Correa-Duarte, M.A.
Liz-Marzan, L. M. Kotov, N.A. J. Am. Chem.
Soc., 2003, 125, 2830-2831
8
LBL films of HgTe nanocrystals with strong
infrared emission
Positively charged layer PDDA Mn450000
Negatively charged layer HgTe(CH2OHCHOHS-)H part
icle size 3.5 nm
Photoluminescence of HgTe nanoparticles in the
multilayer (PDDA/HgTe)20 LBL film.
STM image of the PDDA-HgTe monolayer
Rogach, A.L. Koktysh, D.S. Harrison, M.
Kotov, N.A. Chem. Mater., 2000, 12 , 1526 -1528.
9
Conclusions

• Layer-by-layer method is a versatile technique
  that provides opportunities to create novel
  materials with designed properties
• Bulk materials constructed by such a method
  retain the unique properties of the nanoparticles
• The described materials will have various
  applications in electronics and medicine

10
References

1. Mamedov, A.A. Belov, A. Giersig, M. Mamedova,
   N.N. Kotov, N.A. Nanorainbows Graded
   Semiconductor Films from Quantum Dots, J. Am.
   Chem. Soc., 2001, 123, 7738-7739.
2. Rogach, A. L. Koktysh, D. S. Harrison, M.
   Kotov, N. A. Layer by Layer Assembled Films of
   HgTe Nanocrystals with Strong Infrared Emission,
   Chem. Mater., 2000, 12 , 1526 -1528.
3. Wang, Y. Tang, Z. Correa-Duarte, M.A.
   Liz-Marzan, L. M. Kotov, N.A. Multicolor
   Luminiscence Patterning by Photoactivation of
   Semiconductor Nanoparticle Films, J. Am. Chem.
   Soc., 2003, 125, 2830-2831.