PHOTOCHEMISTRY & MATERIALS

Keywords

Self-assembly; microfluidics; nanostructuring; photochemistry; photoconversion; photolithography; photopolymerization; photostructuring; plasmonics

Recent advances in high-quality laser light sources now offer such a wide range of irradiation wavelengths (from the extreme ultraviolet to the near-infrared) and temporal dynamics (down to the femtosecond or even attosecond range) that their use to drive chemical synthesis and materials fabrication will revolutionize the field. Photons act “untraceable” and “remotely”, giving light-triggered approaches decisive advantages in eco-sustainability and adaptability to any substrate geometry. To achieve advanced exploitation and control of light-mediated chemical and structural transformations, it has become essential to have closely linked expertise between photochemistry, optics, and materials science.

This axis aims to push back the limits of the efficiency of photoreactivity, the spatial resolution of photoproduced structures, and the bottom-up control of the optical and mechanical properties of materials, for example, based on nanometric photostructuring. These interdisciplinary activities will gather French teams with cutting-edge expertise in photopolymerization, photochemical engineering, super-resolution microscopy, plasmonics, and laser-matter interactions. They will require the simultaneous development of photoreactive chemical systems, solution processes, tunable optical tools for rapid phototransformation with high homogeneity or spatial and polarization control, and the implementation of artificial intelligence-based technologies to gain speed and reproducibility in the production of high value-added objects with applications in all industrial sectors. All these questions will be addressed in the following three scientific challenges, which are based on cross-cutting fundamental issues, namely photoactivation with a low energy threshold thanks to high photoreaction quantum yields, control of the diffusion of reactive species concerning the space and time scales of the applied processes, generation of well-defined nanoscale architectures, and design of complex optical structures and metasurfaces from non-equilibrium regimes.

Boosting photoactivity and photoconversion in solution

The advent of compact and emission-tunable LED sources will lead us to generate an unprecedented portfolio of novel families of photoreactive organic compounds serving as photoinitiators and photocatalysts in the booming fields of light-driven radical polymerization, depolymerization, photodepollution, and green chemistry. Since mass and heat transfers are crucial parameters determining the reaction kinetics, the combination of light sources with continuous flow microfluidic technologies (especially micro/nanodroplet reactors) will represent a second buoyant field of investigation aiming at significantly improving photoconversions due to enhanced air/water or oil/water interfaces and extensive light penetration compared to classical batch processes.

Performing photostructuration exploiting light and chemicals’ nanoconfinement

We will demonstrate that compared to e-beam lithography, light-driven processes controlled at the nanometer scale will be attractive alternatives for cost-effective technologies to fabricate innovative 3D nanoconstructs such as optical couplers, (bio)sensors or actuators, among others. Nanometer spatial confinement and strong optical coupling of photoresponsive species (e.g., photopolymerizable ones) with plasmonic structures, optical cavities (giving rise to polaritonic chemistry), or zero-mode waveguides will promote new exciting paradigms of photoreactivity based on nonlinear energy exchange, opening the way to enhanced collective reactivity at lower energy. Their management and study will require local probes and spatially resolved microscopies such as stimulated emission depletion, stochastic optical reconstruction microscopy, and coherent anti-Stokes Raman scattering, intelligently used as both writing and analysis tools to enable operando monitoring of the reactive process.

Ultrafast processes for bottom-up photo-manufacturing of large optically active areas

We will address how to master the fabrication of large areas with complex geometries and in-sight functional structures below 100 nm on meter square domains. Ultrafast pulsed irradiation will thus cleverly exploit the ability of photoresponsive chemicals (metal complexes, organic molecules) to spontaneously self-assemble after photoinduced electron or energy transfer and generate out-of-equilibrium nanostructures from strong chemical gradients with as yet unexplored macroscopic properties. To go one step further, the extension to exotic polarizations, multiphotonic excitation, and XUV or mid-infrared intense ultrashort pulses will open up exciting possibilities as the creation of novel patterns arising from charge-directed reactivity enabled by attosecond lasers and the tailoring of materials down to the atomic/molecular scale.