Nano-enabled sensing of per-/poly-fluoroalkyl substances (PFAS) from aqueous systems - A review

Fundamental investigation on fluorous nanoemulsion optodes: effect of matrix fluorination on selectivity

As fundamental investigation on fluorous nanoemulsion (NE) optodes for highly selective perfluorooctanesulfonate (PFOS-) sensing, the effect of matrix fluorination on selectivity was investigated. Due to the high hydrophobicity of PFOS- itself, it responded in exhaustive mode regardless of the fluorination ratio of the matrix, and the lowest detectable PFOS- concentration was on the order of 10-7 to 10-6 M. On the other hand, the response of non-fluorous interfering anions was suppressed as the fluorination ratio of the matrix increased. It was revealed that the relative selectivity of PFOS- for hydrophobic anions, ClO4-, SCN-, and 1-octanesulfonate (OS-) was improved by more than one order of magnitude, up to nearly two orders of magnitude, and that it was also improved by less than one order of magnitude for hydrophilic anions, Br-, Cl-, and SO4-, in logarithmic selectivity coefficient (log K PFOS - , j opt ).

Recent advances in the application of magnetic materials for the management of perfluoroalkyl substances in aqueous phases

Perfluoroalkyl substances (PFASs) are a class of artificially synthesised organic compounds extensively used in both industrial and consumer products owing to their unique characteristics. However, their persistence in the environment and potential risk to health have raised serious global concerns. Therefore, developing effective techniques to identify, eliminate, and degrade these pollutants in water are crucial. Owing to their high surface area, magnetic responsiveness, redox sensitivity, and ease of separation, magnetic materials have been considered for the treatment of PFASs from water in recent years. This review provides a comprehensive overview of the recent use of magnetic materials for the detection, removal, and degradation of PFASs in aqueous solutions. First, the use of magnetic materials for sensitive and precise detection of PFASs is addressed. Second, the adsorption of PFASs using magnetic materials is discussed. Several magnetic materials, including iron oxides, ferrites, and magnetic carbon composites, have been explored as efficient adsorbents for PFASs removal from water. Surface modification, functionalization, and composite fabrication have been employed to improve the adsorption effectiveness and selectivity of magnetic materials for PFASs. The final section of this review focuses on the advanced oxidation for PFASs using magnetic materials. This review suggests that magnetic materials have demonstrated considerable potential for use in various environmental remediation applications, as well as in the treatment of PFASs-contaminated water.

A Non-Bonding Interaction-Based Fluorescent Probe for Detection of Halogenated Carbonyl Compounds

The fluorescent detection of neutral and volatile carbonyl halogenated compounds had not been studied before. We describe here a simple and sensitive turn-on rhodamin fluorescent probe for the selective detection of fluorinated/brominated/chlorinated/iodinated carbonyl compounds. A wide range of linear or cyclic volatile organic halides was detected with a limit of detection as low as 45.6 nM within 1 min. Mechanistic experiments and DFT calculations indicate the reversible formation of a 1:1 complex of sensor and analyst through non-bonding interaction.

The Latest Sensor Detection Methods for per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFASs) have emerged as a prominent environmental pollutant in recent years, primarily due to their tendency to accumulate and magnify in both the environment and living organisms. The entry of PFASs into the environment can have detrimental effects on human health. Hence, it is crucial to actively monitor and detect the presence of PFASs. The current standard detection method of PFAS is the combination of chromatography and mass spectrometry. However, this requires expensive instruments, extra sample pretreatment steps, complicated operation and long analysis time. As a result, new methods that do not rely on chromatography and mass spectrometry have been developed and applied. These alternative methods mainly include optical and electrochemical sensor methods, which offer great potential in terms of real-time field detection, instrument miniaturization, shorter analysis time, and reduced detection cost. This review provides a summary of recent advancements in PFAS detection sensors. We categorize and explain the principles and mechanisms of these sensors, and compare their limits of detection and sensitivity. Finally, we discuss the future challenges and improvements needed for PFAS sensors, such as field application, commercialization, and other related issues.

Detection of Per- and Polyfluoroalkyl Substances (PFAS) by Interrupted Energy Transfer

The ubiquitous presence of per- and polyfluoroalkyl substances (PFAS) in aqueous environments has aroused societal concern. Nonetheless, effective sensing technologies for continuous monitoring of PFAS within water distribution infrastructures currently do not exist. Herein, we describe a ratiometric sensing approach to selectively detect aqueous perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentrations of μg ⋅ L-1 . Our method relies on the excitonic transport in a highly fluorinated poly(p-phenylene ethynylene) to amplify a ratiometric emission signal modulated by an embedded fluorinated squaraine dye. The electronic coupling between the polymer and dye occurs through overlap of π-orbitals and is designed such that energy transfer is dominated by an electron-exchange (Dexter) mechanism. Exposure to aqueous solutions of PFAS perturbs the orbital interactions between the squaraine dye and the polymer backbone, thereby diminishing the efficiency of the energy transfer and producing a "polymer-ON/dye-OFF" response. These polymer/dye combinations were evaluated in spin-coated films and polymer nanoparticles and were able to selectively detect PFAS at concentrations of ca. 150 ppb and ca. 50 ppb, respectively. Both polymer films and nanoparticles are not affected by the type of water, and similar responses to PFAS were found in milliQ and well water.

The colorimetry and smartphone determination of perfluorooctane sulfonate based on cytidine 5'-monophosphate-capped gold nanoclusters with peroxidase-like activity

Besides being a luminescent material, cytidine 5'-monophosphate-capped gold nanoclusters (AuNCs@CMP) also show superior peroxidase-like activity which can promote TMB oxidation in the presence of H₂O₂, causing the solution to turn efficiently from pale to blue. However, the presence of perfluorooctane sulfonate (PFOS) in the above system inhibited TMB oxidation and bluing of the solution, consequently establishing a colorimetric platform of AuNCs/H₂O₂/TMB for PFOS determination. The results showed that it responded to PFOS over a wide range of 2.0-50 μM, with a limit of detection (LOD) as low as 150 nM. Furthermore, in-depth mechanism investigation revealed that, rather than the active site of the catalyst being occupied by PFOS, such a hypochromatic effect originated from depletion of the reactive oxygen species (ROS) by PFOS degradation, thereby also offering a unique strategy to scavenge the lethal toxicity of PFOS. In addition, the colorimetric response of AuNCs/H₂O₂/TMB to PFOS was extended to smartphone determination conveniently based on RGB values. Finally, the established platform was applied to PFOS determination both in soil extracts and in tap water with good recovery, which supplies a novel colorimetric platform for visual determination of PFOS in practice. The method has the advantages of being rapid, sensitive and highly selective, which highlight the design and construction of more systems for determination and elimination of lethal pollutants in environmental water.

Environmental and health impacts of PFAS: Sources, distribution and sustainable management in North Carolina (USA)

Poly- and perfluoroalkyl substances (PFAS) are a class of manufactured chemicals that have recently attracted a great deal of attention from environmental regulators and the general public because of their high prevalence, resistance to degradation, and potential toxicity. This review summarizes the current state of PFAS and its effects on the environment of North Carolina, USA. Specific emphasis has been placed to identify i) the sources of PFAS in North Carolina ii) distribution of PFAS in different environmental segments of North Carolina, including surface water, groundwater, air, and sediment iii) drinking water contamination iv) impact of PFAS on human health v) PFAS accumulation in fish and other biota vi) status of PFAS removal from drinking water and finally vi) socioeconomic impact of PFAS uncertainties. Continuous discharges of PFAS occur in the North Carolina environment from direct and indirect sources, including manufacturing sites, firefighting foam, waste disposal and treatment plants, landfill leachate, and industrial emissions. PFAS are widespread in many environmental segments of North Carolina. They are more likely to be detected in surface and groundwater sediments and can enter aquatic bodies through direct discharge and wet and dry deposition of emissions. Eventually, some adverse effects of PFAS have already been reported in North Carolina residents who could have been exposed to the chemicals through contaminated drinking water. Furthermore, PFAS were also found in blood samples from fish and alligators. PFAS were confirmed to be present in water, sediment, organic compounds, and aquatic species at all levels of the food web. However, there is still a substantial amount of work to be done to understand the actual contamination by PFAS in North Carolina comprehensively.

Ultratrace PFAS Detection Using Amplifying Fluorescent Polymers

Per- and poly(fluoroalkyl) substances (PFAS) are environmentally persistent pollutants that are of growing concern due to their detrimental effects at ultratrace concentrations (ng·L^-1) in human and environmental health. Suitable technologies for on-site ultratrace detection of PFAS do not exist and current methods require complex and specialized equipment, making the monitoring of PFAS in distributed water infrastructures extremely challenging. Herein, we describe amplifying fluorescent polymers (AFPs) that can selectively detect perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentrations of ng·L^-1. The AFPs are highly fluorinated and have poly(p-phenylene ethynylene) and polyfluorene backbones bearing pyridine-based selectors that react with acidic PFAS via a proton-transfer reaction. The fluorinated regions within the polymers partition PFAS into polymers, whereas the protonated pyridine units create lower-energy traps for the excitons, and emission from these pyridinium sites results in red-shifting of the fluorescence spectra. The AFPs are evaluated in thin-film and nanoparticle forms and can selectively detect PFAS concentrations of ∼1 ppb and ∼100 ppt, respectively. Both polymer films and nanoparticles are not affected by the type of water, and similar responses to PFAS were found in milliQ water, DI water, and well water. These results demonstrate a promising sensing approach for on-site detection of aqueous PFAS in the ng·L^-1 range.