Mesoscopic level systems are ubiquitous in physical chemistry (micelles, catalytic surfaces), in life processes (membranes, macromolecular assemblies) and in applications in electronic, telecommunication, chemical and pharmaceutical industries. They are characterized by the close intertwining of microscopic dynamics and macroscopic level behavior. Research in the group has helped to clarify the limits of validity of the mean-field description, depending on the degree of nonlinearity of the process and the embedding spatial dimensionality. It has also led to a thermodynamically consistent formulation of mechano-chemical couplings and of coupled reactive and transport processes in the presence of nonideality. From an experimental point of view mesoscopic systemsare addressed by near-field ion microscopy to reveal the fluctuation-mediated coupling of local oscillators.

The following problems are currently being investigated:

• Emergence of nanoscale patterns arising from the interference between nonequilibrium processes and equilibrium critical phenomena.
• Self-organization in gels : mechanical response to autocatalytic chemical reactions.
• Reactive dynamics on low-dimensional supports : mean-field versus master equation descriptions, emergence of anomalous inhomogeneous fluctuations.
• Nanoscale experiments and modelling of the NO/H₂ and CO/O₂ reaction on Pt and Au, respectively.

Selected publications:

• S. Prakash and G. Nicolis, "Dynamics of the Schlögl models on lattices of low spatial dimension", J. Stat. Phys. 86 , 1289-1310 (1997).
• A. Provata, G. Nicolis and F. Baras, "Oscillatory dynamics in low-dimensional supports : a lattice Lotka-Volterra model", J. Chem. Phys. 110 , 8361-8368 (1999).
• C. Nicolis, J.J. Kozak and G. Nicolis, "Encounter-controlled reactions between interacting walkers in finite lattices : complex kinetics and many-body effects", J. Chem. Phys. 115 , 663-670 (2001).
• D. Carati and R. Lefever, "Chemical freezing of phase separation in inniscible binary mixtures", Phys. Rev. E 56 , 3127-3136 (1997).

• N. Kruse, "Dynamics of Surface Reactions Studied by Field Emission Microscopy and Atom-Probe Mass Spectrometry", Ultramicroscopy, 89 p.51-61, 2001.

• T. Visart de Bocarmé and N. Kruse, "Kinetic Instabilities during the NOx Reduction with Hydrogen on Pt Crystals Studied with Field Emission on the Nanoscale", Chaos, 12, p.118, 2002.

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Spatial development of surface chemical explosion as obtained from a minimal model of the NO/H₂ reaction. Black, grey and blank squares stand, respectively, for adsorbed NO, adsorbed H, and empty sites.