A compact sensor, capable of detecting PFOS in drinking water at 250 parts per quadrillion, has been developed by scientists at the University of Chicago and Argonne National Laboratory. The method, published in Nature Water, uses a remote gate field-effect transistor (RG-FET) functionalized with β-cyclodextrin–modified reduced graphene oxide to selectively bind PFOS molecules and report changes in electrical conductivity, delivering results in under two minutes.
“Existing methods to measure levels of these contaminants can take weeks, and require state-of-the-art equipment and expertise,” said Junhong Chen, corresponding author and Crown Family Professor at the UChicago Pritzker School of Molecular Engineering. “Our new sensor device can measure these contaminants in just minutes.”
To design probes with sufficient specificity for PFOS over structurally similar compounds, the team used machine learning to screen chemical candidates. “In this context, machine learning is a tool that can quickly sort through countless chemical probes and predict which ones are the top candidates for binding to each PFAS,” Chen explained.
The probes are designed to discriminate PFAS from other waterborne species based on molecular interaction. “Even though they are typically present at miniscule concentrations, PFAS do have certain molecular characteristics that differentiate them from other things dissolved in water, and our probes are designed to recognize those features,” said co-corresponding author Seth Darling.
To confirm real-world accuracy, the team cross-validated sensor measurements with EPA-approved liquid chromatography–tandem mass spectrometry (LC-MS/MS) methods, showing strong agreement across concentrations. Mechanistic studies using quartz crystal microbalance and molecular dynamics simulations revealed that hydrophobic interactions and charge complementarity govern PFOS binding to the sensor’s probe layer.
The team is now extending the approach to other PFAS compounds. “Our next step is to predict and synthesize new probes for other, different PFAS chemicals and show how this can be scaled up,” said Chen. “From there, there are many possibilities about what else we can sense with this same approach – everything from chemicals in drinking water to antibiotics and viruses in wastewater.”
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