Adsorption, Aggregation and Structure Formation in Systems of Charged Particles: From Colloidal to Supracolloidal Assembly

155 Pages·2014·6.992 MB·English

by  Bhuvnesh Bharti (auth.)

Springer Theses
Recognizing Outstanding Ph.D. Research
Bhuvnesh Bharti
Adsorption,
Aggregation and
Structure Formation
in Systems of Charged
Particles
From Colloidal to Supracolloidal
Assembly
Springer Theses
Recognizing Outstanding Ph.D. Research
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Bhuvnesh Bharti
Adsorption, Aggregation
and Structure Formation in
Systems of Charged Particles
From Colloidal to Supracolloidal Assembly
Doctoral Thesis accepted by
Technical University of Berlin, Germany
1 3
Author Supervisor
Dr. Bhuvnesh Bharti Prof. Gerhard H. Findenegg
Department of Chemical and Biomolecular Stranski Laboratorium
Engineering Department of Chemistry
North Carolina State University Technical University of Berlin
Raleigh Berlin
USA Germany
ISSN 2190-5053 ISSN 2190-5061 (electronic)
ISBN 978-3-319-07736-9 ISBN 978-3-319-07737-6 (eBook)
DOI 10.1007/978-3-319-07737-6
Springer Cham Heidelberg New York Dordrecht London
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Parts of this thesis have been published in the following journal articles:
1. B. Bharti; J. Meissner; S. H. L. Klapp; G. H. Findenegg, “Bridging interaction
of protein with silica nanoparticles: Influence of pH, ionic strength and protein
concentration”, Soft Matter, 2014, 10, 718.
2. B. Bharti; G. H. Findenegg; O. D. Velev, “Co-Assembly of Oppositely Charged
Particles into Linear Clusters and Chains of Controllable Length”, Sci. Rep.
(Nature), 2012, 2, 1004.
3. B. Bharti; M. Xue; J. Meissner; V. Cristiglio; G. H. Findenegg, “Assembling
Wormlike Micelles in Tubular Nanopores by Tuning Surfactant-Wall
Interactions”, J. Am. Chem. Soc., 2012, 134, 14756.
4. B. Bharti; G. H. Findenegg, “Protein-specific Effects of Binding to Silica
Nanoparticles”, Chem. Lett., 2012, 41, 1122.
5. B. Bharti; J. Meissner; U. Gasser; G. H. Findenegg, “Surfactant Adsorption
and Aggregate Structure at Silica Nanoparticles: Effects of Particle Size and
Surface Modification”, Soft Matter, 2012, 8, 6573.
6. B. Bharti; J. Meissner; G. H. Findenegg, “Aggregation of Silica Nanoparticles
Directed by Adsorption of Lysozyme”, Langmuir, 2011, 27, 9823.
No problem can stand the assault of
sustained thinking.
C. F. Kettering
Supervisor’s Foreword
Interaction of inorganic colloids with soft matter covers a wide range of phenomena
that play an important role in the natural environment as well as in industrial and
biomedical applications. In his Ph.D. work, Bhuvnesh Bharti addresses fundamen-
tal questions about the interaction of surfactants and proteins with nanoscale silica
materials. Concepts developed from the study of interactions of soft and hard matter
at the nanoscale are then used for assembling permanent linear chain structures of
oppositely charged polystyrene microbeads.
Threadlike molecular assemblies are excluded from narrow pores unless attrac-
tive interactions with the confining pore walls compensate for the loss of con-
figurational entropy. In the thesis it is shown by small-angle neutron scattering
(SANS) that wormlike micelles of the nonionic surfactant C E can be assembled
12 5
in the 8 nm tubular nanopores of SBA-15 ordered mesoporous silica by adjusting
the interaction of the surfactant with the pore walls. In addition, the curvature of
the adsorbing surface also has a significant influence on the morphology of the
surface aggregates. This is indicated by an observed strong decrease in the limiting
adsorption of C E with decreasing diameter of silica nanoparticles. I believe that
12 5
the concept of tuning the surfactant–substrate interactions by changing curvature
or by adding a surface modifier will be applicable to a variety of self-assembling
molecules and nano-curved surfaces. Experimental and theoretical follow-up stud-
ies have confirmed the importance of this work.
pH-induced ionization of weakly acidic or basic surface groups on colloi-
dal particles represents another important route to manipulate interactions at the
nanoscale. Specifically, the interplay between attractive and repulsive interac-
tions of a pair of oppositely charged particles can lead to the formation of unique
supramolecular assemblies. In the thesis, the globular protein lysozyme and sil-
ica nanoparticles (20 nm) have been chosen as a model system which was stud-
ied by a combination of experimental techniques over a wide range of pH and
ionic strength. It was found that the adsorption affinity and binding capacity of
lysozyme on the silica particles increases strongly with increasing pH, indicat-
ing the directing role of electrostatic interactions in the adsorption processes.
Analytical centrifugation and small-angle X-ray scattering studies showed that
the adsorbed protein induces bridging aggregation of the silica particles. Compact
aggregates were formed at pH 4–6, but loose flocculated network at pH 7–9,
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x Supervisor’s Foreword
followed by a sharp decrease in aggregate size near the isoelectric point (IEP) of
lysozyme. The results of silica aggregation in the presence of lysozyme were com-
pared with a similar globular protein (cytochrome C). In this case, a shift in the
aggregating pH regime was observed and attributed to the non-uniform surface
charge distribution of the cytochrome C. These studies have already been widely
appreciated in the scientific community.
As concluded from the protein-particle project, oppositely charged colloidal
particles snap on contact and form permanent, but disordered aggregates. In con-
trast, AC-electric fields can cause a directional assembly of chains from repulsive
particles by dielectrophoresis (DEP), but these structures fall apart once the field
is switched off. In this thesis it has been demonstrated that well-organized, per-
manent clusters and chains of micron-sized particles can be assembled by apply-
ing DEP to mixtures of oppositely charged microspheres. It was found that the
assembly process depends on the size ratio as well as the number ratio of the two
particles, and a set of assembly rules for the structures resulting from the process
could be formulated. This study forms a basis for tailoring new classes of perma-
nent supra-colloidal clusters and gels.
Berlin, Germany, April 2014 Prof. Gerhard H. Findenegg
Acknowledgments
First and foremost I offer my sincere gratitude to my supervisor, Prof. Gerhard H.
Findenegg, who encouraged me throughout the tenure of my thesis. This Ph.D.
work would not have been possible without his constant support and luminous
guidance. In equal measures, I am thankful to my second supervisor, Prof. Orlin
D. Velev for hosting me at NCSU, and guiding me with his patience, knowledge
and innovative ideas during my stay in his group. I would also like to acknowl-
edge the useful discussions and inputs given by Professors R. v Klitzing, S. Klapp,
D. Lerche, S. K. Mehta and M. Gradzielski.
I am grateful to Jens Meissner for his help with the experiments; he has been
a great asset to me not only in my Ph.D. work, but also as a close friend. I am
also thankful to Dr. D. Lugo (TU, Berlin) and Dr. S. Gangwal (NCSU, Raleigh)
for their help in starting up the new projects. In addition, I would like to express
my gratitude to Dr. S. Prévost (TU Berlin) and Dr. S. Smukov (NCSU, Raleigh)
for their useful ideas and advices. I highly appreciate the help of Dr. T. Söbisch
(LUM, Berlin), Dr. U. Gasser (PSI, Zurich), Dr. V. Cristiglio (ILL, Grenoble),
Dr. J. Justin (LLB, Saclay), S. Selve (ZELMI, Berlin), Dr. T. Mielke and J. Bürger
(MPI für Molekulare Genetik, Berlin) for their helps with the various experimental
techniques.
I am indebted to Deutsche Forschungsgemeinschaft (DFG) in the frame work
of IGRTG-1524 for the financial support. I am grateful to all IGRTG members;
specifically, I would like to thank the Chairman, Prof. M. Schön, Managing
Director, Dr. D. Fliegner and Administrative Assistant, Mrs. P. Erdmann for their
friendly support. I am also thankful to secretaries, Christiane, Maria and CTA’s
Ingke, René, Michaela, Gabi and Jana for their help with the bureaucratic and
experimental work.
I consider myself to be lucky to have such awesome colleagues both in TU
Berlin as well as in NCSU Raleigh. Specially, I would like to thank Raphael,
Heiko and Ravneet for their friendly support and motivation.
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