Within this study, a stable nanosuspension of silver nanoparticles (Ag NPs) was prepared using a two-step synthesis and stabilization approach. The Ag NPs were synthesized from a silver nitrate solution using the Origanum vulgare L. plant extract as the reducing agent. The formation of nanoparticles was finished upon 15 min, and subsequently, stabilization by polyvinylpyrrolidone (PVP) using wet stirred media milling was applied. UV-Vis spectra have shown a maximum at 445 nm, corresponding to the formation of spherical Ag NPs. Infrared spectroscopy was used to examine the interaction between Ag NPs and the capping agents. TEM study has shown the formation of Ag NPs with two different average sizes (38 ± 10 nm and 7 ± 3 nm) after the plant-mediated synthesis, both randomly distributed within the organic matrix. During milling in PVP, the clusters of Ag NPs were destroyed, the Ag NPs were fractionized and embedded in PVP. The nanosuspensions of PVP-capped Ag NPs were stable for more than 26 weeks, whereas for the non-stabilized nanosuspensions, only short-term stability for about 1 week was documented.

Chalcogenide glasses with a nominal composition of Ga₅Ge₂₀Sb₁₀Se_(65-x)Te_x (x = 0, 10, 20, 25, 30, 32.5, 35, 37.5) were synthesized. Their physico-chemical properties, glass network structure and optical properties are clearly modified via the substitution of selenium by tellurium. Based on a detailed study of the Ga₅Ge₂₀Sb₁₀Se_(65-x)Te_x bulk glasses properties, the Ga₅Ge₂₀Sb₁₀Se₄₅Te₂₀ seleno-telluride glass optimal composition has been selected for fiber drawing. The luminescence properties of Tb³⁺(500 ppm) doped Ga₅Ge₂₀Sb₁₀Se₆₅ and Ga₅Ge₂₀Sb₁₀Se₄₅Te₂₀ bulk glasses and fibers were studied. Radiative transitions parameters calculated from the Judd-Ofelt theory are compared to the experimental values. Mid-wavelength infrared emission in the range of 4.3-6.0 µm is attributed to the ⁷F₅→⁷F₆ transition of Tb³⁺ions with a corresponding experimental lifetime of 8.9 and 7.8 ms for the selenide and seleno-telluride matrix, respectively. The ⁷F₄ → ⁷F₆ emission was recorded at 3.1 µm with a good signal-to-noise ratio, evidencing a rather strong emission from the ⁷F₄ manifold. Finally, although it was expected that the phonon energy will be lower for telluride glasses, selenide glasses are still more suitable for mid-wavelength infrared and long wavelength infrared emissions with well-defined emissions from 3.1 to 8 μm.

Fiber Evanescent Wave Spectroscopy (FEWS) is an efficient way to collect optical spectra in situ, in real time and even, hopefully, in vivo. Thanks to selenide glass fibers, it is possible to get such spectra over the whole mid-infrared range from 2 to 12 μm. This working window gives access to the fundamental vibration band of most of biological molecules. Moreover selenide glasses are stable and easy to handle, and it is possible to shape the fiber and create a tapered sensing head to drastically increase the sensitivity. Within the past decades, numerous multi-disciplinary studies have been conducted in collaboration with the City Hospital of Rennes. Clinical trials have provided very promising results in biology and medicine which have led to the creation in 2011 of the DIAFIR Company dedicated to the commercialization of fiber-based infrared biosensors. In addition, new glasses based on tellurium only have been recently developed, initially in the framework of the Darwin mission led by the European Space Agency (ESA). These glasses transmit light further into the far-infrared and could also be very useful for medical applications in the near future. Indeed, they permit to reach the vibrational bands of biomolecules laying from 12 to 16 μm where selenide glasses do not transmit light anymore. However, while Se is a very good glass former, telluride glasses tend to crystallize easily due to the metallic nature of Te bonds. Hence, further work is under way to stabilize the glass composition for fibers drawing and to lower the optical losses for improving their sensitivity as bio-sensors.