In the research group of Prof Sophie Hermans, we develop expertise in inorganic chemistry, heterogeneous catalysis and functional nanomaterials for specific applications.
Two common themes underlie our current research:
- Molecular approaches for nanostructured solids elaboration
- Decoration of surfaces with functional groups or nanoparticles.
The common methodology is depicted below. Most of our studies start by a solid surface functionalization step (a). This is usually followed by anchoring of metallic complexes (b). The last step is controlled transformation of complex precursors into supported nanoparticles of desired size and composition (c). Each step has demonstrated its usefulness in a range of applications.
Our research concentrates on 3 main axis:
1. Chemical functionalization of nano-carbon surfaces
Nano-carbons of different types (carbon nanofibers, carbon nanotubes, graphene) were functionalized by covalent (starting by oxidation or radicalar attack) or non-covalent methods. Two innovative methods were found, the first one involving xanthates as radicals and the second one implying nucleophilic addition followed by propargylic capture. In both cases, a wide range of organic moieties are covalently attached at the nano-carbon surface and available for further modification.
Chemical methods were developed to functionalize directly nano-carbonaceous materials immobilized between electrodes for application in sensing devices for example.
Principle of chemical functionalization of nano-carbon (nanotubes, graphene) embedded in devices, for local probe measurements, electrical characterization and sensors.
2. Preparation of supported nanoparticles
The main goal of this second axis is to prepare supported heterogeneous catalysts with tight control over nanoparticles size, composition and shape. We have mainly worked on carbon-supported noble metals active phase for carbohydrate transformations, but recently opened new doors by using boron nitride as support. The carbohydrate transformations studied are relevant to biomass valorization strategies, and in this context bifunctional and/or protected catalysts are currently being elaborated, in addition to non-noble metals formulations.
TEM image of Pd nanoparticles deposited on multi-walled carbon nanotubes, prepared using a molecular complex grafted onto surface functions.
TEM images of BN-supported Pd catalysts with triangular shapes of nanoparticles: these materials were found to be more performant for the hydrogenation of lactose than spherical nanoparticles.
We also develop supported magnetic nanoparticles based on Fe, Co, Ni metals or their oxides, or combination of those. These find application in metamaterials elaboration by inclusion in a polymer matrix or as magnetically-recoverable nanostructured catalytic supports.
3. Oxide functionalization
This third axis focuses on the development of oxide supports (SiO2, TiO2, and hydroxyapatite) with a specific architecture, such as spherical nanoparticles, urchins, or mesoporous capsules. Their surfaces are modified with complex catalysts or specific chemical groups. These materials are then used in various processes relevant to photocatalytic, optical or medical applications. Indeed, we developed for example hydroxyapatite and SiO2 scaffolds modified with Fe and Cu catalysts for the production of OH and NO radicals. We work also on amine-modified TiO2 and SiO2 nanoparticles to be blended with stimuli-responsive polymers in order to produce nanostructured composites used as air pollution detectors. Another application is the immobilization of organophotocatalysts and copper complexes on nanostructured silica supports for photocatalytic organic synthesis.
TEM images of Fe/SiO2 (MCM48) mesoporous catalyst for OH radical production (left) and SEM images of spherical SiO2 particles used for low refractive index coating (right).