Department of Physics and Astronomy
Condensed Matter and Materials Physics
Alex Shluger's group
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Dr. Maria Sushko

About me

I was born in St. Petersburg, Russia. After graduation from the Department of Physics St. Petersburg State University in 1997 with MSc degree I have joined the Institute of Macromolecular Compounds Russian Academy of Science as a Junior Research Fellow where I have completed my PhD thesis in 2000 in the area of polymer physics. I have joined the group of Prof. J. Seddon and Prof. R. Templer in the Department of Chemistry Imperial College London in 2000, where I was working on the rheology of surfactant ordered phases. From 2003 I am a Research Fellow in the group of Prof. A. Shluger, Department of Physics and Astronomy UCL. My current interests lie in the area of properties of organic - inorganic interfaces in vacuum and in solutions.

Research

My research interests lie in three main directions: NC-AFM imaging and manipulation of organic molecules on oxide surfaces, cantilever based surface stress sensors and interactions of polyelectrolyte with charged surfaces across an electrolyte solution.

1. Organic molecules on oxide surfaces and their NC- AFM imaging

TiO2A Force-field for the interactios of organic molecules with TiO2 (110) surface. We have studied the adsorption of a number of organic molecules consisting of methyl, benzyl and carboxylic groups on the rutile TiO2 (110) surface using both ab initio and atomistic simulation techniques. We have tested the applicability of a simple embedded cluster model to studying the adsorption of small organic molecules on the rutile TiO2 (110) surface, and used this model in order to develop a classical force-field for the interactions of a wide class of organic molecules consisting of these groups with the rutile TiO2 (110) surface. The force-field accounts for physisorption and ionic bonding of organic molecules at TiO2 surface. It allows the reproduction of adsorption energies and of geometries of organic molecules on the rutile surface.

B Is it possible to have simultaneous high resolution of organic molecules and atomic resolution on the surface? NC-AFM manipulation of large organic molecules on insulating surfaces requires the ability to determine the initial orientation of the molecule with respect to the surface features and the direction for manipulation with respect to the surface. We have therefore studied the conditions for obtaining simultaneous high resolution of the molecule and the surface for a C52H72O3 molecule on TiO2 surface, which has been studied experimentally by the group of S. Gauthier (CEMES, Toulouse). Our calculations show that due to weak interactions of SiO2 tips with the organic molecule compared to its interactions with the surface the simultaneous atomic resolution of the surface and the topographic resolution of the molecule can be achieved only with a sharp SiO2 tip terminated by a doubly-coordinated oxygen in a narrow range of normalised frequency shifts. Collaboration: Sebastien Gauthier (CEMES-CNRS, Toulouse), Gerard Dujardin (CNRS, Orsay)

2.Cantilever based stress sensors ? how do they work?

In order to elucidate the nature of interactions responsible for the sensor function of self-assembled monolayers (SAM) we are developing an embedded cluster approach for Au / SAM / solvent system, which will allow considering the properties of the system on quantum mechanical level while taking into account the van der Waals interactions between the organic molecules . Using the embedded cluster approach we are studying the in- and out-of- plane forces in the SAMs terminated with carboxylic group as a function of pH and nature and concentration of electrolyte in the solvent. Collaboration: Rachel McKendry (UCL)

DNA

3.Polyelectrolytes at charged surfaces

Application of AFM to biological systems requires the deposition of aqueous solutions of biomolecules onto surfaces. In most cases the biological molecules as well as the substrates are charged in solutions and it proved to be challenging to find the conditions for polymer adsorption. We propose a mean-field theory for the interactions of like-charged polyelectrolyte and a plane surface in the presence of 1:1 and 2:1 electrolyte, which takes into account long-range van der Waals and double-layer forces. The theoretical predictions were varified against the results of AFM imaging of DNA adsorbed onto a mica surface in NaCl, MgCl2 and NiCl2 solutions as well as the mixtures of NaCl and 2:1 electrolytes. Collaboration: Claudio Rivetti (Parma, Italy)

Selected publications

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