World Journal Of Engineering
Flow induced surface attachment of gold nanoparticles – an in situ x-ray
investigation with micro-fluidic cell
Volker Körstgens, Monika Rawolle, Adeline Buffet1, Gunthard Bennecke1, Gerd
Herzog1, Jan Perlich1, Matthias Schwartzkopf1, Martin Trebbin2, Julian Thiele2,
Sebastian With2, Frans J. de Jong3, Michael Schlüter3, Stephan V. Roth1, Stefan Förster2,
Peter Müller-Buschbaum
Lehrstuhl für Funktionelle Materialien, Physik-Department E13, TU München, James-FranckStr. 1, 85747 Garching, Germany
1) Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, 22607 Hamburg, Germany
2) Physikalische Chemie 1, Universität Bayreuth, Universitätsstr. 30, 95447 Bayreuth,
Germany
3) Institut für Mehrphasenströmungen, TU Hamburg-Harburg, Eißendorfer Str. 38, 21073
Hamburg, Germany
Introduction
The deposition of metallic nano-particles onto
solid surfaces is of interest in a wide range of
topics from nanoelectronics and nanosensors
to nanocatalysts. One way to achieve patterns
of ordered nanoparticles is to apply a
continuous flow over a substrate surface via a
micro-fluidic channel [1, 2]. X-rays are a
powerful probe for the investigation of flow
and processes in micro-fluidic systems. In
transmission geometry, e.g. with SAXS
(small angle x-ray scattering) growth
processes of nanoparticles can be followed. In
reflection geometry using GISAXS (grazing
incidence small angle x-ray scattering),
together with a special designed micro-fluidic
cell also surface sensitive investigations are
possible [1]. With this method the selective
immobilization of gold nanoparticles on one
block of a micro-phase separated blockcopolymer surface was investigated in-situ
leading to the growth of gold nanowires [2].
Experimental
In figure 1 the set-up of the micro-fluidic cell
used at the micro- and nanofocus x-ray
scattering beamline (MiNaXS/P03) at the
third generation synchrotron source PETRA
III at DESY in Hamburg is shown. The x-ray
beam was focused to a size of 35 μm  22 μm
by beryllium compound refractive lenses. The
arrow in figure 1 depicts the x-ray beam from
the position of guard slits to the position
hitting the micro-fluidic cell. The microfluidic cell for GISAXS investigations
comprises a top part made of a copolymer
based on cyclic olefines as shown in figure 2.
Fig. 2: Part of the fluidic cell [1].
The material is transparent to visible light and
has a relative low absorption in the x-ray
range used in the experiments. The top part is
connected to the surface to be investigated (e.
g. a thin polymer film on a glass slide with a
metallic clamp as shown in figure 1). The
channel geometry (1 mm wide and 1.3 mm
deep) enables the study of the solid-liquid
interface during the continuous flow stream of
Fig. 1: Micro-fluidic cell for GISAXS
experiments, installed at the beamline P03.
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World Journal Of Engineering
a solution with a broad range of flow rates.
There are two inlets allowing for mixing
experiments and chemical reactions.
A scan of the micro-fluidic channel (along ydirection in figure 2) is carried out, collecting
scattering data at 70 different positions. The
flow experiment is run for 1 h with
subsequent scans along the channel. This
procedure offers a time resolved as well as a
position resolved investigation of the
attachment of nanoparticles at the same time.
In figure 3 the 2d GISAXS detector patterns
are shown for one of the positions on the
channel for three different times during the
flow experiment. The top image shows the
GISAXS pattern of the dry alginate film. The
characteristic features arising with flow of the
nanoparticle dispersion are Bragg reflections
(figure 3 denoted with “start flow”). The
Bragg reflections are accompanied by a ring
shaped intensity centered by the direct beam.
With ongoing flow experiment the Bragg
reflections as well as the ring shaped intensity
are more pronounced and observed at smaller
q-values (figure 3 denoted with “1h flow”).
The scattering patterns with Bragg reflections
indicate domains of 2d cylindrical hexagonal
structures oriented parallel to the surface.
Investigated system
In this study the attachment of high aspect
ratio gold nanorods to surfaces of calciumalginate is investigated. Spin-coating of thin
films of sodium-alginate and subsequent
cross-linking with divalent calcium ions leads
to water insoluble films. The high aspect ratio
gold nanorods with a size of 25 nm x 256 nm
are stabilized with cetyltrimethylammoniumbromide (CTAB). Gold nanorods with CTAB
layers show interesting self-assembling
properties [3, 4]. In the investigation
presented here the polyanion alginate serves
as a counterpart to the nanoparticles with netpositive charge.
-1
qz [nm ]
2.0
dry
1.5
1.0
Conclusion
The surface sensitive micro-fluidic GISAXS
experiment offers a time as well as a position
resolved investigation of the attachment of
nanoparticles. With the additional use of real
space imaging techniques for the nanoparticle
covered alginate surface after the flow
experiment the description of the attachment
of gold nanorods dependent on time and
position on the fluidic channel during the flow
experiment is possible.
0.5
-1
qz [nm ]
2.0
start flow
1.5
1.0
0.5
-1
qz [nm ]
2.0
1h flow
This work has been financially supported by
the BMBF (grant number 05K10WOA).
1.5
References
1.0
0.5
-2.0
-1.5
-1.0
-0.5
-1
qy [nm ]
[1] J.-F. Moulin, S. V. Roth, P. Müller-Buschbaum,
Rev. Sci. Instrum. 2008, 79, 015109.
[2] E. Metwalli, J.-F. Moulin, J. Perlich, W. Wang,
A. Diethert, S. V. Roth, P. Müller-Buschbaum,
Langmuir 2009, 25, 11815-11821.
[3] W. Cheng, S. Dong, E. Wang, Langmuir 2003, 19,
9434-9439.
[4] T. K. Sau, C. J. Murphy, Langmuir 2005, 21, 29232929.
0.0
Fig. 3: Example of 2d GISAXS patterns
recorded in a micro-fluidic experiment at the
MINAXS instrument.
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