Colloidal and photonic crystals
Prepared by group 4:
Anna Kaczmarczyk
Aleksandra Jayko
Katarzyna Mocniak
Michał Kaczmarek
Paweł Lis
Colloidal and photonic crystals
Outline:
1. Colloidal crystals with tunable colors and their use
as photonic papers
2. Photonic crystals from core-shell colloids with
incorporated highly fluorescent quantum dots
3. Dye-containing polymer beads as photonic
crystals
4. Heterostructures of polymer photonic crystal films
5. Laboratory nanoparticles - report
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.
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.
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.
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.
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.
Photonic crystals from core-shell colloids with
incorporated highly fluorescent quantum dots
Schematic illustraton of QD incorporation into the core of core-shell colloids.
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:
1.
In-situ growth methods (chemical vapor and chemical or
electrochemical bath deposition).
2.
Electrostatic fixation on the surface of the polymer sphres being
subsequently crystalized to artificial opals.
There are several disadvantages of this process:
1.
Incorporation of QDs into the voids of colloidal crystals does not
protect the QDs from oxidation.
2.
In-situ growth methods do not allow the formation of high-quality QDs
known for low polydyspersity and strong photoluminescence (PL).
3.
Requirement of thioglycolic acid that are well-known PL reducing
agents.
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 angulardependent fluorescence
measurements. The
measurements were performed in
reflection and the PL was excited
with an argon ion laser at 457,9
nm.
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.
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 facecentered cubic packages. This method
allows it to cover large films with opaline
structure with can be used as photonic
crystals.
Dye-containing polymer beads as photonic crystals
Advantages of using PMMA are:
1.
2.
3.
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.
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.
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.
Heterostructures of polymer photonic crystal films
Schematic illustration of the crystallization in a moving meniscus:
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.
Heterostructures of polymer photonic crystal films
Generally, the film thickness depends on such parameters as:
 Lifting speed,
 Solution concentration,
 Temperature,
 Air humidity,
Dependence of the film thickness on the suspension
concentration for PMMA latice
40
Profile depth [um]
 Sphere size.
35
30
25
20
15
10
5
0
0
2
4
6
Suspension concentration [%]
8
10
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.
Laboratory nanoparticles - report
Preparation and charakterization of ZnS:Mn nanoparticles
Chemicals which were used in experimental part
Substance
Purity
Zinc acetate
~98 %
Mangan acetate
~98 %
Sodium sulphide
~60 %
Cysteamin
~97 %
Ethanol
Technical
Acetic acid
Technical
Absolute
mass
In 125 ml H2O
2,253 g
Zn(Ac)2
0,478 g
Mn(Ac)2
0,941 g
Cysteamin
0,465 g
Na2S
In 25 ml H2O
Laboratory nanoparticles - report
Laboratory nanoparticles - report
Thank you for your attention !!!
Thank you for your attention !!!