-
See discussions, stats, and author profiles for this publication
at: https://www.researchgate.net/publication/265476039
Formation of spherical aggregate from micodroplet containing
submicron
inclusions
Conference Paper · August 2014
DOI: 10.13140/2.1.2338.2405
CITATIONS
0READS
97
7 authors, including:
Some of the authors of this publication are also working on
these related projects:
Spectral modification of absorption in photovoltaic thin
composite films containing plasmonic nanospheres of divers sizes:
assessment of possible photocurrent and
hot-carriers production in perovskite composite. View
project
Drying kinetics of micro-composite droplets and their final
product analysis View project
Mariusz Woźniak
PIT-RADWAR S.A.
48 PUBLICATIONS 251
CITATIONS
SEE PROFILE
Justice Archer
University of Bristol
17 PUBLICATIONS 43
CITATIONS
SEE PROFILE
G. Derkachov
Institute of Physics of the Polish Academy of Sciences
36 PUBLICATIONS 268
CITATIONS
SEE PROFILE
Daniel Jakubczyk
Institute of Physics of the Polish Academy of Sciences
68 PUBLICATIONS 677
CITATIONS
SEE PROFILE
All content following this page was uploaded by Krystyna Kolwas
on 10 September 2014.
The user has requested enhancement of the downloaded file.
https://www.researchgate.net/publication/265476039_Formation_of_spherical_aggregate_from_micodroplet_containing_submicron_inclusions?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_2&_esc=publicationCoverPdfhttps://www.researchgate.net/publication/265476039_Formation_of_spherical_aggregate_from_micodroplet_containing_submicron_inclusions?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_3&_esc=publicationCoverPdfhttps://www.researchgate.net/project/Spectral-modification-of-absorption-in-photovoltaic-thin-composite-films-containing-plasmonic-nanospheres-of-divers-sizes-assessment-of-possible-photocurrent-and-hot-carriers-production-in-perovskite?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_9&_esc=publicationCoverPdfhttps://www.researchgate.net/project/Drying-kinetics-of-micro-composite-droplets-and-their-final-product-analysis?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_9&_esc=publicationCoverPdfhttps://www.researchgate.net/?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_1&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Mariusz_Wozniak4?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_4&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Mariusz_Wozniak4?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_5&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Mariusz_Wozniak4?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_7&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Justice_Archer?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_4&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Justice_Archer?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_5&_esc=publicationCoverPdfhttps://www.researchgate.net/institution/University_of_Bristol?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_6&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Justice_Archer?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_7&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/G_Derkachov?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_4&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/G_Derkachov?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_5&_esc=publicationCoverPdfhttps://www.researchgate.net/institution/Institute_of_Physics_of_the_Polish_Academy_of_Sciences?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_6&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/G_Derkachov?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_7&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Daniel_Jakubczyk?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_4&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Daniel_Jakubczyk?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_5&_esc=publicationCoverPdfhttps://www.researchgate.net/institution/Institute_of_Physics_of_the_Polish_Academy_of_Sciences?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_6&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Daniel_Jakubczyk?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_7&_esc=publicationCoverPdfhttps://www.researchgate.net/profile/Krystyna_Kolwas?enrichId=rgreq-e484ba86c10c76ba0b879c6b3126d85a-XXX&enrichSource=Y292ZXJQYWdlOzI2NTQ3NjAzOTtBUzoxMzk4MDE1Mjk0MjU5MjJAMTQxMDM0MjY5MDU3NA%3D%3D&el=1_x_10&_esc=publicationCoverPdf
-
FORMATION OF SPHERICAL AGGREGATE FROM MICODROPLET
CONTAININGSUBMICRON INCLUSIONS
Mariusz WOŹNIAK*, Justice ARCHER, Gennadiy DERKACHOV, Daniel
JAKUBCZYK,Tomasz WOJCIECHOWSKI, Krystyna KOLWAS, Maciej KOLWAS
Institute of Physics, Polish Academy of Sciences, Al. Lotników
32/46, 02-668 Warsaw, Poland
*Corresponding author: [email protected]
AbstractWe have investigated formation of ordered aggregates
of spherical nanosilica particles in evaporating droplets
ofaqueous colloidal suspension. Droplets have been freelysuspended
in the electrodynamic quadrupole trap. Slowdrying process and the
successive states of the aggregateformation have been investigated
using static light scatter-ing method. Modification made to the
typical configura-tion of the electrodynamic quadrupole trap
enables us todeposit the final (and the semi-final) structures and
toinvestigate them with SEM methods.
1 IntroductionEvaporation process on a flat surface leading to
forma-
tion of drop-deposited nanoparticle films and self-assembled
monolayers of nano-crystals have been recentlywidely observed and
discussed in the literature [1]. Bymeans of the aggregation
phenomenon it is possible tocreate composites whose physical
properties are deter-mined not only by their chemical composition
but also bythe specific morphology. This new kind of
structures,known as metamaterials, exhibit unique (optical)
proper-ties not present in conventional materials.
However, much less is known about aggregation proc-ess in
systems with spherical geometry such as dryingmicrodroplets of
suspension (e.g. [2]). Few studies con-cerning shell-structured or
densely-packed aggregates ofspheres appear in the literature (e.g.
[3]) and even fewerhave reported as regular, as dense or as large
aggregatesthat we can observe and model [4,5]. Similar
self-assembled structures, but generated by means of a fastspray
drying method, were investigated in our formercollaborative work
[6].
In contrast to evaporation of a film of suspension lead-ing to
nanoparticle films, evaporation process of levitatedmicrodroplets
is unaffected by flat bulk surface. This par-ticular geometry
enables production of truly 3D photonicmetamaterials and
quasi-photonic crystals with sphericalor quasi-spherical symmetry.
In order to produce anddiagnose this kind of objects it is
necessary to build highlyspecialized equipment. These requirements
are satisfied byelectrodynamic traps with climatic chambers and
addi-tional control instruments built in our laboratory. To
ana-lyse and measure liquid microdroplets and particles
ag-gregating within them we use static light scattering meth-
ods. Our modifications and improvements made to thetypically
used geometry of the electrodynamic quadrupoletrap gives us a
possibility to deposit aggregates one-by-one on a flat silicon
substrate and to investigate them addi-tionally with SEM.
2 Evaporation process and surface phenomenaAggregation in a
micodroplet of suspension is caused
by evaporation process of liquid phase. The droplet evapo-ration
process is driven by mass and heat transportthrough the droplet
surface. A convenient expressions ofthe evaporation dynamics of a
spherical droplet of pureliquid can be found [5,7]:
( ) ( )cc cc a acc a
da p T p Ta aa Ddt T T
(1)
where a is a droplet radius, pa and pcc are the vapourpressure
near the droplet surface and far from the dropletrespectively, Ta
and Tcc are the temperatures of the dropletsurface and the
reservoir. D is the diffusion constant ofvapour in the ambient gas
and /M R , where Mand are the molecular weight and density
respectively, Ris the universal gas constant.
The surface activity Δσ, describing the change of sur-face
tension with respect to the surface tension of a pureliquid σw can
be expressed as:
0ln 12a
w as a
aa aa taT TDp T
(2)
It is worth noticing that using Eq. (2) we can find thetemporal
evolution of the surface pressure Δσ(t) from thetemporal evolution
of the droplet radius a(t).
3 ExperimentOur experimental setup consists of a quadrupole
elec-
trodynamic trap with 4 linear electrodes in a verticalalignment.
The electrodes provide alternating (AC) electricfield in quadruple
configuration. Separate annular elec-trodes around the vertical
ones provide static (DC) fieldbalancing the particles weight. The
trap is kept in a smallthermostatic chamber, which allows us to
control parame-ters of the internal atmosphere by choosing ambient
gasand adjusting temperature (from -40 up to +50°C). Figure 1shows
schematic drawing of the experimental setup. Forgraphic purposes
climatic chamber is not shown.
CP-10.1
-
LASER-LIGHT AND INTERACTIONS WITH PARTICLES AUGUST 25-29TH,
2014, MARSEILLE, FRANCE
Figure 1. Schematic drawing of the experimental setup.
Droplets are injected by on-demand injector andcharged by charge
separation in the external field. Twocoaxial, counter propagating
lasers are used simultane-ously for droplet illumination: green
(532 nm) p-polarizedand red (654 nm). The entirely defocused image
is used forscatterometry. The focused image is used for droplet
posi-tion stabilization with a PID type loop. The temporal
evo-lution of the droplets is obtained with the Mie
ScatteringLookup Table Method [8]. It is based on the fitting of
thecomplete Mie theory predictions (stored in the lookuptable) to
the experimentally obtained scattering patterns.Our method provides
accuracy of ±10 nm [8].
Additionally, it is worth noticing that vertical alignmentof the
quadrupole trap allows us to progressively reduceDC field without
changes of the AC field constrainingdroplet (aggregate) horizontal
position and thus soft-landing of the aggregating structure on the
silicon sub-strate at the bottom part of the trap. It is also
possible toshift the substrate inside the trap up to the
stabilizationpoint. Deposition allows us to further analyse
aggregateswith microscopic methods (SEM, TEM, AFM).
4 Results and discussionThe experiment was conducted at the
temperature of
288.2 K, the initial humidity of 94% and the atmosphericpressure
of 1006 hPa. We used aqueous suspension of SiO2spheres with
diameter of 450 nm (MP-4540, Nissan Chemi-cal Industries). The
suspension obtained from the manu-facturers was diluted with
ultrapure water (Milli-Q Plus,Millipore) in 250:1 proportion
resulting in the initial vol-ume concentration of nanoparticles
∼0.1%. Stabilizingagent introduced by the manufacturer was not
removed.
Figure 2 shows experimental evolution of the dropletradius a t
obtained with the Mie Scattering Lookup TableMethod as well as the
numerical results of our evaporationmodel for pure water and water
with solid inclusions(fraction of ∼0.1%).
0 2 4 6 8 10 12 14 16 18 200
2
4
6
8
10
12
Rad
ius
[m
]
Time [s]
Droplet evolution: Experimental results
Numerical model of: pure water water with solid inclusions
Figure 2. Evolution of the droplet of aqueous suspension of
450nm silica spheres (experimental and numerical results)
andnumerical results for droplet containing pure water.
Using Eq. (2) we can express the surface pressure as afunction
of the droplet radius .a Figure 3 shows a together with
visualisation of the selected stages of
our simulation of the evolution of an evaporating dropletof
nanosilica suspension (droplet size scaled for clarity) [4].
Figure 3. Surface pressure isotherm together with
visualisationsof the selected stages of our simulations [4] of the
evolution of adroplet of suspension (droplet size scaled freely for
clarity).
We have observed and also modelled different thermo-dynamic
states of the surface layer of inclusions, occurringduring
evaporation of liquid with silica inclusions. Theyhave been
separated in Figure 3 with vertical, doted lines.
For relatively large droplet (a > 7.9 μm) when the frac-tion
of inclusions is smaller than ~3%, there is a surface gasof
inclusions on the droplet surface (Figure 3 (a)). Subse-quently gas
of inclusions is becoming denser (Figure 3 (b)).For 4.25 > a
> 5.75 μm we observe the liquid-expandedphase (Figure 3 (c)).
The surface is covered with large butdilute aggregates. Further
evaporation of water com-presses the surface structures while the
number of inclu-
CP-10.2
-
LASER-LIGHT AND INTERACTIONS WITH PARTICLES AUGUST 25-29TH,
2014, MARSEILLE, FRANCE
sions on the surface is further increasing. Additionally,
thisstage was investigated with SEM after deposition of thedroplet
with aggregating structure on the silicon surface(Figure 4 (a)).
Due to the significant fraction of water de-posited structure was
not stable and disintegrated formingthin layer of silica
nanoparticles.
Figure 4. SEM images of the deposited structures: (a)
middlestage of the formation, (b) semi-final and (c) final (totally
dried)stage of the aggregation/evaporation
For a = ~4.25 μm a phase transition to liquid-condensed is
possibly observed. Further compressionleads to the surface
liquid-solid transition for a = ~3.55 μm(Figure 3 (e)). This state
can be possibly seen in Figure 4(b). It can be inferred from
careful observation of the SEMimage that at the time of the
deposition this structure wasstill containing a significant
fraction of water, which totally
dried out after landing. Therefore, we can see circulartraces
around the solid aggregate left by evaporating liq-uid. It can be
noticed, that at this stage of aggregation, awell-organized
structure, foreseen by our numericalmodel, appears on the aggregate
surface. Subsequently,when the evaporation of the droplet
continues, after therapid growth of the surface pressure, a
collapse of thesurface layer takes place for a = ~3.45 μm (Figure 3
(f)). It isfollowed by the formation of a multilayered surface
solidassociated with the significant decrease in the
surfacepressure. The SEM image of the final structure observedafter
the deposition can be seen in Figure 4 (c). A transitionfrom
spherical symmetry to less regular structure can beidentified by
comparing Figure 4 (b) with Figure 4 (c).
5 ConclusionWe have shown that analysing the evolution of
the
droplet radius only, it is possible to derive enough
infor-mation to determine surface states of inclusions of
evapo-rating droplet of colloidal suspension. Our unique
experi-mental setup gives us a possibility to deposit the
aggregat-ing structure at the selected stage of the evolution
andanalyse it with microscopic methods. Therefore, we wereable to
compare our numerical models of evaporation andaggregation with
experimental results obtained with staticlight scattering method
and SEM analysis. We found verygood consistency between them.
However, application of SEM to the analysis of dy-namic
processes is limited. Hence, we were able to observeonly to the
final and the semi-final structures of dryingaggregates because the
previous stages were not stableenough and they disintegrated after
deposition. Moreover,further evaporation on the surface of the
substrate alteredthe evolution path.
Future perspectives for our research includes
detailedconsideration of the successive aggregation stages,
utiliza-tion of various nanoparticles, as well as application
ofadditional methods to “freeze” the evolution of the dropletat the
earlier stages (e.g. by adding UV-active polymers).
6 References[1] Rabani E., Reichman D. R., Geissler P. L., Brus
L. E., Drying-mediated self-assembly of nanoparticles, Nature, 426:
271-274 (2003).
[2] Lee S. Y., Gradon L., Janeczko S., Iskandar F., Okuyama K.,
Forma-tion of highly ordered nanostructures by drying micrometer
colloidaldroplets, ACS Nano, 4 (8): 4717–4724 (2010).
[3] Lauga E.. Brenner M. P., Evaporation-driven assembly of
colloidalparticles, Phys. Rev. Lett., 93: 238301 (2004).
[4] Derkachov G., Kolwas K., Jakubczyk D., Zientara M., Kolwas
M.,Drying of a Microdroplet of Water Suspension of Nanoparticles:
fromSurface Aggregates to Microcrystal, J. Phys. Chem. C, 112:
16919-16923(2008).
CP-10.3
-
LASER-LIGHT AND INTERACTIONS WITH PARTICLES AUGUST 25-29TH,
2014, MARSEILLE, FRANCE
[5] Jakubczyk D., Kolwas M., Derkachov G., Kolwas K., Surface
statesof micro-droplet of suspension, J. Phys. Chem. C, 113 (24):
10598-10602(2009).
[6] Onofri F.R.A., Barbosa S., Toure O., Woźniak M., Grisolia
C., Sizinghighly-ordered buckyball-shaped aggregates of colloidal
nano-particlesby light extinction spectroscopy, J. Quant.
Spectrosc. Radiat. Transfer,126: 160–168 (2013).
[7] Pruppacher H., Klett J., Microphysics of Clouds and
Precipitation(Kluwer, The Netherlands, 1997).
[8] Jakubczyk D., Derkachov G., Kolwas M., Kolwas K.,
Combiningweighting and scatterometry: application to a levitated
droplet ofsuspension. J. Quant. Spectrosc. Radiat. Transfer, 126:
99-104 (2013).
CP-10.4
View publication statsView publication stats
https://www.researchgate.net/publication/265476039