“…A polymeric membrane is used to extract pollutant molecules from water and also to decrease the water amount along the IR beam. Different materials were studied for their ability to extract molecules: Teflon AF2400, Poly(acrylonitrile-co-butadiene) (PAB), Polydimethylsiloxane (PDMS), Ethylene-propylene copolymer (EPco) and Polyisobutylene (PIB) [24,25]. PIB is commonly used for its ability to extract small aromatic hydrocarbons such as BTX (benzene, toluene and xylenes).…”
Section: Chalcogenide Functionalization By a Polymermentioning
The detection of molecules dissolved in liquid medium can be envisaged by means of an optical integrated sensor operating in middle infrared range. The intended sensor is composed of a cladding and a guiding selenide sputtered layers transparent in middle infrared. Hence, Ge-Sb-Se thin films were selected in view of tailored refractive index contrast, successfully deposited by radio frequency magnetron sputtering and characterized. To maximize the evanescent field at a wavelength of 7.7 µm, a suitable selenide waveguide allowing measuring the optical transmitted power was designed by performing computer simulations based on the effective index method enabling single-mode propagation for a waveguide width between 8 and 12 µm. Selenide sputtered films were micro-patterned using reactive ion etching with inductively coupled plasma process. Finally, optical waveguide surface was functionalized by the deposition of a hydrophobic polymer, which will permit detection of organic molecules in water.
“…A polymeric membrane is used to extract pollutant molecules from water and also to decrease the water amount along the IR beam. Different materials were studied for their ability to extract molecules: Teflon AF2400, Poly(acrylonitrile-co-butadiene) (PAB), Polydimethylsiloxane (PDMS), Ethylene-propylene copolymer (EPco) and Polyisobutylene (PIB) [24,25]. PIB is commonly used for its ability to extract small aromatic hydrocarbons such as BTX (benzene, toluene and xylenes).…”
Section: Chalcogenide Functionalization By a Polymermentioning
The detection of molecules dissolved in liquid medium can be envisaged by means of an optical integrated sensor operating in middle infrared range. The intended sensor is composed of a cladding and a guiding selenide sputtered layers transparent in middle infrared. Hence, Ge-Sb-Se thin films were selected in view of tailored refractive index contrast, successfully deposited by radio frequency magnetron sputtering and characterized. To maximize the evanescent field at a wavelength of 7.7 µm, a suitable selenide waveguide allowing measuring the optical transmitted power was designed by performing computer simulations based on the effective index method enabling single-mode propagation for a waveguide width between 8 and 12 µm. Selenide sputtered films were micro-patterned using reactive ion etching with inductively coupled plasma process. Finally, optical waveguide surface was functionalized by the deposition of a hydrophobic polymer, which will permit detection of organic molecules in water.
“…Thereby, detection levels in the parts per billion (i.e., μg/L) concentration range have been realized in a true chemical physico-chemical sensing format (i.e., diffusion of analyte molecules into and out the solid phase membrane in lieu of chemical reactions). Using such membranes, IR-ATR-based chemosensors have been developed serving for environmental contaminant monitoring, 32,56 in pollutant analysis, 11,57,58 and even in microbiological applications, 59 as exemplarily illustrated for detection of volatile organic components (VOCs) towards dissolved oil fingerprinting in aqueous/marine environments (Figure 5). Figure 5.(Top left) Schematic of IR-ATR system comprising a macroscopic ZnSe IRE coated with a polymeric enrichment membrane for detecting organic pollutants in marine environments (i.e., dissolved oil fingerprinting via characteristic VOC patterns dissolved in the aqueous phase).…”
Section: Recent Trends and Selected Applicationsmentioning
Significant advancements in waveguide technology in the mid-infrared (MIR) regime during recent decades have assisted in establishing MIR spectroscopic and sensing technologies as a routine tool among nondestructive analytical methods. In this review, the evolution of MIR waveguides along with state-of-the-art technologies facilitating next-generation MIR chem/bio sensors will be discussed introducing a classification scheme defining three "generations" of MIR waveguides: (1) conventional internal reflection elements as "first generation" waveguides; (2) MIR-transparent optical fibers as "second generation" waveguides; and most recently introduced(3) thin-film structures as "third generation" waveguides. Selected application examples for these each waveguide category along with future trends will highlight utility and perspectives for waveguide-based MIR spectroscopy and sensing systems.
“…Unlike these methods based on univariate calibration, multivariate analysis of MIR spectra allows the use of several solvents for extraction since the contaminant quantification is based on fingerprint analysis. Although sample preparation makes the method laborious and time-consuming, the use of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy provides a fast analysis (less than 1 min per sample) with a small volume of sample (1 mL or less) (Pejcic et al 2013). Thus, the improvement in method accuracy will compensate the sample preparation step if the extraction method is adequate.…”
Environmental contamination caused by leakage of fuels and lubricant oils at gas stations is of great concern due to the presence of carcinogenic compounds in the composition of gasoline, diesel, and mineral lubricant oils. Chromatographic methods or non-selective infrared methods are usually used to assess soil contamination, which makes environmental monitoring costly or not appropriate. In this perspective, the present work proposes a methodology to identify the type of contaminant (gasoline, diesel, or lubricant oil) and, subsequently, to quantify the contaminant concentration using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and multivariate methods. Firstly, gasoline, diesel, and lubricating oil samples were acquired from gas stations and analyzed by gas chromatography to determine the total petroleum hydrocarbon (TPH) fractions (gasoline range organics, diesel range organics, and oil range organics). Then, solutions of these contaminants in hexane were prepared in the concentration range of about 5-10,000 mg kg. The infrared spectra of the solutions were obtained and used for the development of the pattern recognition model and the calibration models. The partial least square discriminant analysis (PLS-DA) model could correctly classify 100% of the samples of each type of contaminant and presented selectivity equal to 1.00, which provides a suitable method for the identification of the source of contamination. The PLS regression models were developed using multivariate filters, such as orthogonal signal correction (OSC) and general least square weighting (GLSW), and selection variable by genetic algorithm (GA). The validation of the models resulted in correlation coefficients above 0.96 and root-mean-square error of prediction values below the maximum permissible contamination limit (1000 mg kg). The methodology was validated through the addition of fuels and lubricating oil in soil samples and quantification of the TPH fractions through the developed models after the extraction of the analytes by the EPA 3550 method adapted by the authors. The recovery percentage of the analytes was within the acceptance limits of ASTM D7678 (70-130%), except for one sample (69% of recovery). Therefore, the methodology proposed here provides faster and less costly analyses than the chromatographic methods and it is adequate for the environmental monitoring of soil contamination by gas stations.
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