Prezentacja programu PowerPoint

1
Colloidal and photonic crystals
Prepared by group 4 Anna Kaczmarczyk
Aleksandra Jayko Katarzyna Mocniak Michal
Kaczmarek Pawel Lis
2
Colloidal and photonic crystals

• Outline
• Colloidal crystals with tunable colors and their
  use as photonic papers
• Photonic crystals from core-shell colloids with
  incorporated highly fluorescent quantum dots
• Dye-containing polymer beads as photonic crystals
• Heterostructures of polymer photonic crystal
  films
• Laboratory nanoparticles - report

3
Colloidal crystals with tunable colors and their
use as photonic papers
What are the colloidal crystals?
They are long-ranged ordered lattice assembled
from spherical colloids such as polymer latexes
and silica spheres.
By organizing such colloids into crystalline
lattice it is possible to obtain interesting
functionality. This beautiful indescent color of
an opal orginates from Bragg diffraction of a
crystalline lattice assembled from silica
colloids that display no color by themselves.
The similar mechanism has also been used by a
variety of insects butterflies, bees to
decorate their skins with shiny colors without
involving the use of any conventional pigments.
4
Colloidal crystals with tunable colors and their
use as photonic papers
Bragg equation

• Where
• m diffraction order
• - wavelength of the diffracted light
• na- a mean refractive index of the crystalline
  lattice
• dhkl the interplanar spacing along the hkl
  direction
• ? - the angle between the incident light and the
  normal to the hkl planes

This equation suggests that ? of light diffracted
from a colloidal crystal is directly proportional
to the lattice constant.
5
Colloidal crystals with tunable colors and their
use as photonic papers
Printing colorful patterns without using
convetional pigments
The concept of this new paper ink system has
already been reported in communication
Basically the paper is a colloidal crystal of
polymer beads embedded in an elastomer matrix
made of PDMS, whereas the ink is a liquid
capable of swelling the elastomeric matrix.
As the elastomer is swollen by the ink molecules,
the lattice constants are changed.
6
Colloidal crystals with tunable colors and their
use as photonic papers
If the colors of these states are sufficiently
different to be distinguished by the naked eye,
the contrast can be exploited to write and
display color letters and patterns with certain
spacial resolutions.
As the ink molecules are evaporating the PDMS
matrix will gradually shrink back to its
orginated state and the color patterns will be
automatically erased.
7
Photonic crystals from core-shell colloids with
incorporated highly fluorescent quantum dots
We are presenting the synthesis of composite
Photonic Crystals (PCs) from polymer core-shell
spheres with incorporated highly fluorescent
monodisperse CdSe QDs in the core. The steps how
to prepare are listed below

1. Synthesis of CdS/ZnS Coated CdSe Quantum Dots
   using succesive ion layer adsorptions reaction
   (SILAR), keeping up the light-emitting properties
   of the PC on the Photoluminescens.
2. Synthesis of PS Core Colloids with incorporated
   CdS/ZnS QDs with modyfied miniemulsion
   polymerization.
3. Synthesis of PS/PMMA Core-Shell Colloids with
   incorporated CdS/ZnS Coated CdSe QDs in the Core
   prepared by a core-shell polymeryzation.
4. Crystalization of the Core-Shell Spheres to
   Colloidal Crystals.

8
Photonic crystals from core-shell colloids with
incorporated highly fluorescent quantum dots
Schematic illustraton of QD incorporation into
the core of core-shell colloids.
9
Photonic crystals from core-shell colloids with
incorporated highly fluorescent quantum dots

• Up to now semiconductors QDs have been
  incorporated into the voids of colloidal crystals
  by
• In-situ growth methods (chemical vapor and
  chemical or electrochemical bath deposition).
• Electrostatic fixation on the surface of the
  polymer sphres being subsequently crystalized to
  artificial opals.

• There are several disadvantages of this process
• Incorporation of QDs into the voids of colloidal
  crystals does not protect the QDs from oxidation.
• In-situ growth methods do not allow the formation
  of high-quality QDs known for low polydyspersity
  and strong photoluminescence (PL).
• Requirement of thioglycolic acid that are
  well-known PL reducing agents.

10
Photonic crystals from core-shell colloids with
incorporated highly fluorescent quantum dots
The effect of the colloidal crystal photonic stop
band on the PL of the integrated QDs was
investigated by angular-dependent fluorescence
measurements. The measurements were performed in
reflection and the PL was excited with an argon
ion laser at 457,9 nm.
11
Photonic crystals from core-shell colloids with
incorporated highly fluorescent quantum dots
By doping PCs with fluorescent QDs, discrete
electronic and photonic states can be combined as
well as separately engineered within a single
structure. This presents a powerful platform for
the creation of novel nanoscaled light sources
its controllable spontanous emission.
12
Dye-containing polymer beads as photonic crystals
Photonic crystals are periodic dielectric
structures that are designed to control the
propagation of electromagnetic waves by defining
allowed and forbidden energy bands in the phonon
dispersion spectrum. Photonic crystals are
prepared from PMMA Monodisperse PMMA beads of a
size varying between 200-400 nm have been
prepared by a modified emulsion polimerization
sediment well on hydrophilic substraces to form
3- dimentional face-centered cubic packages. This
method allows it to cover large films with
opaline structure with can be used as photonic
crystals.
13
Dye-containing polymer beads as photonic crystals

• Advantages of using PMMA are
• PMMA photonic film can be precisely patterned by
  e-beam lithography with the feature resolution
  down to one bead in width and various fluorescent
  dyes can be incorporated in PMMA balls.
• Dye-impregnated PMMA opaline photonic films
  demonstrate the incomplete photonic band gap
  structure and related modification of dye
  photoluminescence spectrum.
• PMMA is more polar as compared with polystyrene
  and thus a better sovent for the fluorescent
  dyes.Incorporation of dye molecules in PMMA balls
  can be performed much easier as compared with the
  similar procedure used in the case of silica
  balls.

14
Dye-containing polymer beads as photonic crystals

• Preparation of the PMMA Beads
• preparation of films
• determination of the size of the beads
• patterning by electron beam writing

Conclusion PMMA beads are ideal candidates for
the preparation of thin film photonic structures
with optical properties comparable to the best
bulk opals. They have the advantage that they can
be patterned as e-beam resists. In addition they
are more polar than polystrene and thus a better
matrix for various fluorescent laser dyes.
15
Heterostructures of polymer photonic crystal films
Photonic crystals are attracting a lot of
attention as materials for optical switches, data
storage, chemical sensors and lasers with low
threshold.
We describes multilayer opaline films composed
from functional opal layers of spheres with
different lattice constants.
Various monodisperse colloids can be crystallized
into large, well oriented opaline films by the
method of crystallization in a moving meniscus.
After annealing, a second opaline film can be
crystallized on top of these films and so on.
16
Heterostructures of polymer photonic crystal films
Schematic illustration of the crystallization in
a moving meniscus
17
Heterostructures of polymer photonic crystal films
Electron microscopy inspection shows a sharp
borderline between the sublayers and no disorder
on both sides athough the lattice constants in
both films can be incommensurable.
18
Heterostructures of polymer photonic crystal films

• Generally, the film thickness depends on such
  parameters as
• Lifting speed,
• Solution concentration,
• Temperature,
• Air humidity,
• Sphere size.

19
Heterostructures of polymer photonic crystal films
Transmission and reflection measurements prove
the high quality of the films.
The use of a combination of thermolabile and
thermostable colloids opens the possibilty to
prepare functional opaline heterostructures.
20
Laboratory nanoparticles - report
Preparation and charakterization of ZnSMn
nanoparticles
Chemicals which were used in experimental part
Absolute mass
2,253 g Zn(Ac)2
0,478 g Mn(Ac)2
0,941 g Cysteamin
0,465 g Na2S
Substance Purity
Zinc acetate 98
Mangan acetate 98
Sodium sulphide 60
Cysteamin 97
Ethanol Technical
Acetic acid Technical
In 125 ml H2O
In 25 ml H2O
21
Laboratory nanoparticles - report
22
Laboratory nanoparticles - report
23
Thank you for your attention !!!
24
Thank you for your attention !!!