In the exploration of novel Surface Enhanced Raman (SERS) approaches towards the challenging detection of Per- and polyfluoroalkyl substances (PFAS)

Abstract

<p>Per- and polyfluoroalkyl substances (PFAS) are a group of man-made chemicals used in a variety of industries around the globe since the 1940s due to their water- and oil-repellent properties. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) have been the most extensively produced and studied of these chemicals and their toxicity has been well characterized in humans and animal models. Both chemicals are very persistent in the environment and in the human body – meaning they don’t break down and they can accumulate over time. Currently, environmental and epidemiological PFAS analysis is predominantly based on high-performance liquid chromatography (HPLC) coupled with tandem mass spectrometry (MS/MS). As the conventional analytical methods for the detection of PFASs utilize techniques based on ion-pair extraction of the analytes and quantification by MS, they can detect concentrations as low as ppt. However, they typically require, off-site analyses, are very time consuming, relatively expensive and matrix-matched calibration standards should be routinely employed. Furthermore, although these methods have demonstrated reliable results, substantial challenges still exist in increasing the number of PFASs detected and quantified in a single analytical run, working with varied sample matrices, and developing more efficient sample preparation strategies. The development of sensors to detect contaminants in environmental samples is a growing topic in environmental monitoring and management. Many limitations within existing methods of PFAS determination can be addressed through the development of PFAS-detecting sensors. One promising and sophisticated spectroscopic technique is Surface-Enhanced Raman Spectroscopy (SERS), which combines the detection limits of chromatographic techniques and the versatility and speed of the spectroscopic ones. SERS has great potential as an analytical technique based on the unique molecular signatures presented even by structurally similar analyte species and the minimal interference of scattering from water when sampling in aqueous environments. Since the SERS method can provide information which ascertains chemical and molecular composition of a sample, it is usually regarded as a promising tool suitable for the selective detection of pollutants. In this study, Surface Enhanced Raman Scattering (SERS) is explored towards the fast, accurate and versatile identification and quantification of several PFAS along with their possible degradation and transformation products. To that end, different approaches is followed, based mainly on the designed modification/functionalization of Au and Ag nanoparticles (NPs) in colloidal suspensions and the exploitation of the adsorption selectivity of Metal Organic Frameworks for PFAS in order to develop MOF-based SERS substrates. This novel and challenging task bearing both scientific and technological aspects will potentially lead to the development of a sensitive and robust SERS application for PFAS detection suitable for environmental and/or biomonitoring.</p>