surface forces; particle aggregation; atomic force microscopy; light scattering; particle deposition; multivalent ions; adsorption
Szilagyi I., Sadeghpour A., Borkovec M. (2012), Destabilization of colloidal suspensions by multivalent ions and polyelectrolytes: From screening to overcharging, in Langmuir
, 28, 6211-6215.
Porus M., Maroni P., Borkovec M. (2012), Structure of adsorbed polyelectrolyte monolayers investigated by combining optical reflectometry and piezoelectric techniques, in Langmuir
, 28, 5642-5651.
Porus M., Labbez C., Maroni P., Borkovec M. (2011), Adsorption of monovalent and divalent cations on planar water-silica interfaces studied by optical reflectivity and Monte Carlo simulations, in J. Chemical Physics
, 135, 064701-064701.
Finessi M., Sinha P., Szilagyi I., Popa I., Maroni P., Borkovec M. (2011), Charge reversal of sulfate latex particles by adsorbed linear poly(ethylene imine) probed by multiparticle colloidal probe technique, in Journal of Physical Chemistry B
, 115, 9098-9105.
Szilagyi I., Rosicka D., Hierrezuelo J., Borkovec M. (2011), Charging and stability of anionic latex particles in the presence of linear poly(ethylene imine), in Journal Colloid and Interface Science
, 360, 580-585.
Sadeghpour A., Seyrek E., Szilagyi I., Hierrezuelo J., Borkovec M. (2011), Influence of the ionization degree and molecular mass of weak polyelectrolytes on charging and stability behavior of oppositely charged colloidal particles, in Langmuir
, 27, 9270-9276.
Seyrek E., Hierrezuelo J., Sadeghpour A., Szilagyi I., Borkovec M. (2011), Molecular mass dependence of adsorbed amount and hydrodynamic thickness of polyelectrolyte layers, in Physical Chemistry Chemical Physics
, 13, 12716-12719.
Muresan L., Maroni P., Popa I., Porus M., Longtin R., Papastavrou G., Borkovec M. (2011), Probing conformational changes of polyamidoamine (PAMAM) dendrimers adsorbed on silica substrates, in Macromolecules
, 44, 5069-5071.
Porus M., Maroni P., Bhosale R., Sakai N., Matile S., Borkovec M. (2011), Zipper and layer-by-layer assemblies of artificial photosystems analyzed by combining optical and piezoelectric surface techniques, in Langmuir
, 27, 7213-7221.
Popa I., Gillies G., Papastavrou G., Borkovec M. (2010), Attractive and repulsive electrostatic forces between positively charged latex particles in the presence of anionic linear polyelectrolytes, in Journal of Physical Chemistry B
, 114, 3170-3177.
Popa I., Papastavrou G., Borkovec M. (2010), Charge regulation effects on electrostatic patch-charge attraction induced by adsorbed dendrimers, in Physical Chemistry Chemical Physics
, 12, 4863-4871.
Popa I., Papastavrou G., Borkovec M. (2010), Effective charge of adsorbed poly(amido amine) dendrimers: Transition from heterogeneous to homogeneous charge distribution, in Macromolecules
, 43, 1129-1136.
Hierrezuelo J., Sadeghpour A., Szilagyi I., Vaccaro A., Borkovec M. (2010), Electrostatic stabilization of charged colloidal particles with adsorbed polyelectrolytes of opposite charge, in Langmuir
, 26, 15109-15111.
Porus M., Maroni P., Borkovec M. (2010), Highly-sensitive reflectometry setup capable of probing the electrical double layer on silica, in Sensors Actuators B
, 151, 250-255.
Popa I., Finessi M., Sinha P., Maroni P., Papastavrou G., Borkovec M. (2010), Importance of charge regulation in attractive double-layer forces between dissimilar surfaces, in Phys. Rev. Lett.
, 104, 228301-228301.
Hierrezuelo J., Szilagyi I., Vaccaro A., Borkovec M. (2010), Probing nanometer-thick polyelectrolyte layers adsorbed on oppositely charged particles by dynamic light scattering, in Macromolecules
, 43, 9108-9116.
Hierrezuelo J., Vaccaro A., Borkovec M. (2010), Stability of negatively charged latex particles in the presence of a strong cationic polyelectrolyte at elevated ionic strengths, in J. Colloid Interf. Sci.
, 347, 202-208.
Popa I., Gillies G., Papastavrou G., Borkovec M. (2009), Attractive electrostatic forces between identical colloidal particles induced by adsorbed polyelectrolytes, in Journal of Physical Chemistry B
, 113, 8458-8461.
Popa I., Papastavrou G., Borkovec M., Trulsson M., Jonsson B. (2009), Long-ranged attractive forces induced by adsorbed dendrimers: Direct force measurements and computer simulations, in Langmuir
, 25, 12435-12438.
Porus M., Clerc F., Maroni P., Borkovec M., Ion-specific responsiveness of polyamidoamine (PAMAM) dendrimers adsorbed on silica substrates, in Macromolecules
Multivalent ions strongly modify interactions between charged interfaces, and therefore such ions represent important additives to control aggregation or deposition of colloidal particles. For example, multivalent metal ions are used in waste water treatment to accelerate particle aggregation, or they play an essential role in cement hardening. While multivalent ions were already addressed in the classical theory of colloidal aggregation by Derjaguin, Landau, Verwey, and Overbeek (DLVO), this topic is receiving renewed attention due to two recent developments. The first development relates to new theories of the electrical double layer. It is now firmly established that the classical Poisson-Boltzmann (PB) may fail for multivalent ions, and that such ions can adsorb on oppositely charged surfaces due to electrostatic interactions so strongly that the surface may reverse its charge. In the past, it was thought that such a charge reversal is only possible if the adsorption of the ions is controlled by ion-specific forces. Moreover, these theories show that in the presence of multivalent ions, additional non-DLVO attractive forces become relevant and these forces are likely to be important in colloidal aggregation and deposition.The second development concerns important advances in experimental techniques able to probe interaction forces between colloidal particles or between such particles and surfaces. One of these techniques is the colloidal probe method based on the atomic force microscope (AFM). Moreover, one can reliably measure aggregation rate constants with scattering techniques, while particle deposition can be studied by surface sensitive methods. With these techniques at hand, such processes can be investigated experimentally with confidence.The present project builds on these developments, and addresses adsorption of multivalent ions on water-solid interfaces, resulting interactions forces, and consequences for aggregation and deposition phenomena. Adsorption of multivalent ions will be studied on well-defined colloidal latex particles with electrophoresis, cross-flow filtration, and potentiometry. Forces between these particles will be directly measured with the AFM, while their aggregation rates will be probed with light scattering. Situations involving asymmetric particle systems will be studied similarly. Interaction forces between particles and planar substrates will be also assessed with AFM, while the corresponding deposition processes will be followed with optical reflectivity and quartz crystal microbalance. These processes will be modeled with classical surface complexation models and DLVO theory. Comparison with modern theories of the electrical double layer will be achieved through collaborations with groups from other universities.The main goal of the project is to elucidate whether interactions in the presence of multivalent ions are principally governed by generic electrostatic interactions or by ion-specific forces. Furthermore, the origin of additional non-DLVO attractive forces will be clarified, and it will be assessed whether these forces may explain the known discrepancies of DLVO theory in aggregation and deposition processes.