Toward Chalcogenide Platform Infrared Sensor Dedicated to the In Situ Detection of Aromatic Hydrocarbons in Natural Waters via an Attenuated Total Reflection Spectroscopy Study

Abstract

The objective of this study is to demonstrate the successful functionalization of the surface of a chalcogenide infrared waveguide with the ultimate goal of developing an infrared micro-sensor device. First, a polyisobutylene coating was selected by testing its physico-chemical compatibility with a Ge-Sb-Se selenide surface. To simulate the chalcogenide platform infrared sensor, the detection of benzene, toluene, and ortho-, meta- and para-xylenes was efficaciously performed using a polyisobutylene layer spin-coated on 1 and 2.5 µm co-sputtered selenide films of Ge28Sb12Se60 composition deposited on a zinc selenide prism used for attenuated total reflection spectroscopy. The thickness of the polymer coating was optimized by attenuated total reflection spectroscopy to achieve the highest possible attenuation of water absorption while maintaining the diffusion rate of the pollutant through the polymer film compatible with the targeted in situ analysis. Then, natural water, i.e., groundwater, wastewater, and seawater, was sampled for detection measurement by means of attenuated total reflection spectroscopy. This study is a valuable contribution concerning the functionalization by a hydrophobic polymer compatible with a chalcogenide optical sensor designed to operate in the mid-infrared spectral range to detect in situ organic molecules in natural water.

Surface Functionalization with Polymer Membrane or SEIRA Interface to Improve the Sensitivity of Chalcogenide-Based Infrared Sensors Dedicated to the Detection of Organic Molecules

“…The second way of improving the sensitivity is studied by considering the presence of a gold nanostructure for IR absorption enhancement. The possibility of depositing a hydrophobic film on a chalcogenide waveguide has been previously demonstrated . However, it remains to optimize the nature of the polymer envisaged as well as its deposition to determine the limit of detection of individual BTXs, to discuss the competitivity of different polluting molecules and to confirm its regeneration in an easy way.…”

“…ATR measurements were carried out with a 5 ppm solution of BTX in seawater followed by a rinse with a distilled water (Figure ). The results are in agreement with a previous study performed in complex matrices such as seawater and groundwater …”

“…The results are in agreement with a previous study performed in complex matrices such as seawater and groundwater. 21 Although rarely studied, a major aspect enabling selenide sensor development is the possibility of regenerating the polymer for such complex matrices. The PIB polymer regeneration after immersion in complex natural matrices is achieved without particular difficulty in about 30 min.…”

“…If the thickness of the waveguide used is of the same order as the infrared wavelength, then the individual reflections allowed in the ATR prism are no longer distinguishable from each other and the evanescent field appears continuously along the surface of the waveguide during the propagation of the infrared light within it (Figure ). − Due to their wide transparency in the infrared range and their tailored refractive index, chalcogenide glasses are attractive materials for mid-infrared (MIR) sensing applications. , The feasibility of fabricating chalcogenide waveguides for MIR detection of organic molecules in water has been reported previously. − The surface of the chalcogenide waveguide needs to be coated with a hydrophobic film to avoid the large absorption bands of water present in the MIR range, which interfere with the specific absorption features of the analyzed molecules. Although different materials can be used to functionalize a surface, it has been shown that polymers are the most suitable for the detection of hydrocarbons .…”

Insight into the photoinduced phenomena in ternary Ge-Sb-Se sputtered thin films

“…The aim of this paper is to provide a study of photoinduced changes in Ge-Sb-Se chalcogenide thin films which are of particular interest in the field of photonic integrated circuits for their potential application in non-linear optics [12] and optical sensors in midinfrared domain [13,14]. The nominal composition of Ge 25 Sb 10 Se 65 was chosen based on our previous work related to photosensitivity study on this system [15].…”