Within the Molecular Spectroscopy Group of the Institute of Molecular Sciences, the theme 'Functional materials and surfaces' has been established for more than ten years and is based on national and international multidisciplinary collaboration networks. The research work is done on both fundamental and applied themes and concerns scales ranging from the molecule to materials, including nano systems and the micrometric structuring of surface properties. The functionalities studied are also plural, including optical, magnetic, electrical and chemical properties, but also aim at their combination for the development of multifunctional materials or surfaces.

Photonic materials

In the field of photonic materials, the basis of our activity concerns the structural analysis of inorganic glassy materials and the link to their physical properties especially in nonlinear optics (NLO). This structure/properties approach concerns new compositions of glasses, glass-ceramics and glassy thin films. In parallel, a research direction concerns the development of processes by thermos electrical polarization and laser irradiation for the multi-scale structuring of optical properties. These treatments have been optimized for different families of glasses adapted to wavelength ranges from UV to mid-infrared. An important result of this activity concerns the development of an electric field imprinting process allowing the control of the refractive index gradient for the fabrication of micro-structured optics as well as the geometrical and spatial control of an electro-optical anisotropy for second order non-linear optical properties. This research activity is based on an important international network (USA, Canada, Brazil, Greece, Russia).

Molecular switches and phase transition materials

In the field of molecular switches several studies have concerned systems switchable under the action of optical, electrical and/or chemical stimuli. These works are based on a methodology combining spectroscopic studies and theoretical calculation via DFT methods. For example, we can cite the work on electro- / acid- / photo- switchable oxazolidine derivatives studied via their nonlinear optical responses by ex situ and in situ hyper-Rayleigh experiments in solution.

Concerning phase transition materials, we can highlight the study of transitional mechanisms in aperiodic organic crystals like urea inclusion compounds for which structural changes and dynamic phenomena between the different phases were analyzed by neutron spectroscopy. For the first time an interpretation based on host/guest dynamical couplings was proposed.

Functional surfaces

The main challenge of surface functionalization techniques is to obtain a robust attachment of molecules with a specific functionality for the application envisaged later (biosensors, for example). In collaboration with L.Vellutini's team of the C2M group of the ISM, we are developing coupling agents that meet this constraint (covalent anchoring by siloxane groups, presence of a urea group in the middle of the molecule to improve the hydrogen bonding interactions between adjacent molecules and a terminal function with an azide group to bring the desired terminal function by "click chemistry"). Another very important issue in this field is to spatially control the grafting of coupling agents (high throughput screening). Several approaches have been conducted to control the surface reactivity of inorganic glasses by controlling their structure at the micrometer scale and/or by using charge injection processes to promote surface electrostatic interactions.

Atoms being attracted to a poled region on a glass rather than on its unpoled region.

Chiral nanomaterials

In collaboration with the groups of Dr Oda (CBMN) and Pr. Ihara (Kumamoto University, Japan), we are developing chiral nanomaterials (nano-helices or twisted nanoribbons) with novel chiroptical properties in the framework of the LIA NCAP "Chiral Nanostructures for Photonic Applications". These chiral nanomaterials are built from a gemini-tartrate organic base (amphiphilic dimers with tartrate counter anions) on which a silica layer is formed by sol-gel reaction with tetraethoxysilane. We observed for the first time, by vibrational circular dichroism (VCD), the transfer of chirality onto the siloxane groups of silica. These silica nano-helices have been used as chiral nanosupports to self-organize gold nanoparticles or catalysts to develop respectively nanomaterials with interesting properties in photonics (chiral metamaterials, circular polarizers), chiral biosensing and catalysis (enantioselective catalysis). We also used the chiral environment of these silica nano-helices to induce circular dichroism on halide ions by exchange with tartrate anions.