Emmanuel Scolan

Quantum size effect in TiO2 nanoparticles : does it exist?

Abstract We have examined the quantum size effect in anatase TiO2 nanoparticles. No shift of the band gap energy has been observed for sizes 2R≥1.5 nm. On the other hand, we have found unusual variation of the oscillator strength of the first allowed direct transition. The results indicate considerable structural size effect, which disables the effective mass approximation (EMA) in these nanocrystallites.

Self-Patterned Nanoparticle Layers for Vertical Interconnects: Application in Tandem Solar Cells

We demonstrate self-patterned insulating nanoparticle layers to define local electrical interconnects in thin-film electronic devices. We show this with thin-film silicon tandem solar cells, where we introduce between the two component cells a solution-processed SiO2 nanoparticle layer with local openings to allow for charge transport. Because of its low refractive index, high transparency, and smooth surface, the SiO2 nanoparticle layer acts as an excellent intermediate reflector allowing for efficient light management.

Smart Textiles with Biosensing Capabilities

Real-time, on-body measurement using minimally invasive biosensors opens up new perspectives for diagnosis and disease monitoring. Wearable sensors are placed in close contact with the body, performing analyses in accessible biological fluids (wound exudates, sweat). In this context, a network of biosensing optical fibers woven in textile enables the fabric to measure biological parameters in the surrounding medium. Optical fibers are attractive in view of their flexibility and easy integration for on-body monitoring. Biosensing fibers are obtained by modifying standard optical fibers with a sensitive layer specific to biomarkers. Detection is based on light absorption of the sensing fiber, placing a light source and a detector at both extremities of the fiber. Biosensing optical fibers have been developed for the in situ monitoring of wound healing, measuring pH and the activity of proteases in exudates. Other developments aim at the design of sensing patches based on functionalized, porous sol-gel layers, which can be deposited onto textiles and show optical changes in response to biomarkers. Biosensing textiles present interesting perspectives for innovative healthcare monitoring. Wearable sensors will provide access to new information from the body in real time, to support diagnosis and therapy.

Controlling Mesopore Size and Processability of Transparent Enzyme-Loaded Silica Films for Biosensing Applications

Silica-based nanoporous thin films including large mesopores are relevant as enzyme supports for applications in biosensing. The diffusion and immobilization of large biomolecules such as enzymes in such porous films require the presence of large mesopores. Creating such morphologies based on a bottom-up synthesis using colloidal templates is a challenge in view of the combination of desired material properties and the robustness of the casting process for the fabrication of thin films. Here a strategy to reproducibly synthesize transparent porous silica thin films with submicrometer thickness and homogeneously distributed porosity is presented. For this purpose, polystyrene-poly-2-vinylpyridine (PS-P2VP) amphiphilic block copolymers are used as porogenic templates. Low-chain alcohols are employed as both selective solvents for the P2VP blocks and reaction media for silica synthesis. Rheology measurements reveal a strong influence of the block copolymer length on the behavior of PS-P2VP micelles in suspension. The pore distribution and accessibility into the film are controlled by adjusting the silica to block copolymer weight ratio. The solvent choice is shown to control not only the micelle size and the generated pore morphology but also the structural homogeneity of the films. Finally, the suitability of the synthesized films as supports for enzymes is tested using a model enzyme, horseradish peroxidase EC 1.11.1.7. Our approach is innovative, robust, and reproducible and provides a convenient alternative to synthesize large mesopores up to small macropores (20-100 nm) in nanostructured thin films with applications in biosensing and functional coatings.

Manufacturing of superhydrophobic surfaces combining nanosphere lithography with replication techniques

We report on the manufactruring of plastic parts with tailored wettabilities by means of replication techniques. Nanostructured molds have been fabricated by combining nanosphere lithography with standard microfabrication processes. All processes were upscale to produce homogeneous structures over large areas (hundreds of mm2). The replication masters have then been used for the production of nanostructrued plastic parts using UV nanoimprint, hot embossing and injection molding. An approriate design of the nanostructures leads to plastic parts having superhydrophobic/philic surfaces.

Design of nanostructured sol-gel coatings for (bio)sensing applications

Functionalized nanoporous coatings prepared by sol-gel processes are excellent sensing interfaces. Indeed, the high surface area combined with the specific functionalization using organic dyes and biologic entities has led to highly sensitive and selective optical (bio)sensors for gaseous or diluted species. Thus, biochips and optical fibers modified with functionalized nanoporous sensitive layers have been developed for environmental (e.g. gas detection, selective recognition of pesticides) and healthcare applications (e.g. wound monitoring).