Coupling between transport and reactivity in micro- and nano-confined systems. Applications to electrochemistry, catalysis and life sciences – MicroNanoChem

The main aim of this project is the creation of a new research group in the UMR 8640 CNRS unit of the Chemistry Department of Ecole Normale Supérieure, whose researches will be focused on theoretical aspects of the coupling between transport and reactivity in micro- or nanoconfined systems. The originality of the created team and of its researches consists in the treatment of the whole multi-scale mechanistic chain which links reactivity and transport in such systems and not only of the local reactivity as it is usually considered in micro- and nanochemistry or in biochemistry.
This type of approaches imposes severe theoretical burdens due to (i) the necessity of considering the systems over their whole multiscale aspects (i.e., over a bidimensional continuum ranging from several hundreds of micrometers down to nanometric dimensions), (ii) the geometry and heterogeneous reactivity of the chemically or biologically micro- or nano-objects (i.e., 2D-discontinuous boundary conditions), and (iii) the possible presence of acute reaction fronts (i.e., local infinite second order partial derivatives). This conjunction of difficulties forbids the use of classical analytical or numerical methods. Instead, it requires the original development of innovative applied mathematical methods and their integration into real physico-(bio)chemical frameworks. These will be mostly relying on conformal or quasi-conformal transforms since the past works of the applicant (more than 30 research articles in collaboration with C. Amatore from the host laboratory) have established the great usefulness and validity of such approaches.
The tasks investigated during the time course of this project have been selected for their relevance to important real problems raised in rationalizing and optimizing experiments and observations made in different fields of nanosciences thanks to the implementation of new physicochemical methods with near-field resolution (STM, SECM/Scanning ElectroChemical Microscopy). They pertain to four virtually independent tasks:
- Task 1: Micro- and nanoelectrochemistry, kinetics and analytical characterization. The recent applicant’s works performed in collaboration with C. Amatore’s team have validated the principles of the mathematical and numerical methods for basic electrochemical mechanisms. The challenge then consists in generalizing these methods to any system involving arbitrary mechanism and in particular those generating acute reactivity fronts propagating in solution. The project consists in developing a “user-friendly” program aimed to the community. This will perform in conformal spaces on any reaction scheme defined by the user in a transparent way for him/her.
- Task 2: Devising exact modeling of SECM and molecular break junctions in STM. This deals on the one hand with the development of more realistic theoretical models for SECM investigation of electrochemical or conductive properties of active materials. On the other hand, this concerns several important problems in molecular break junctions or in nano-electrochemical cells, both related to single molecule measurements.
- Task 3 concerns the precise modeling of physicochemical processes involved in living cells during vesicular exocytosis with relevance to neurotransmitters release or in oxidative stress.
- Task 4 will investigate a series of topical situations related to the coupling between transport and reactivity in biphasic systems involving dispersion of micro/nano droplets in a fluid. These systems are representative of conditions encountered in phase-transfer catalysis, green chemistry (micro/nano emulsions) or in extraction/remediation, for example of used civil nuclear fuels.