TY - JOUR
T1 - Real-time detection of per-fluoroalkyl substance (PFAS) self-assembled monolayers in nanoporous interferometers
AU - Law, Cheryl Suwen
AU - Wang, Juan
AU - Gunenthiran, Satyathiran
AU - Lim, Siew Yee
AU - Abell, Andrew D.
AU - Ahrens, Lutz
AU - Kumeria, Tushar
AU - Santos, Abel
AU - Voelcker, Nicolas H.
N1 - Funding Information:
Authors would like to acknowledge and pay their respects to the Kaurna–Adelaide and Wurundjeri–Melbourne peoples, the Traditional Custodians of the lands on which this work was performed. Authors thank the support provided by the Australian Research Council through the Grant DP200102614 , the School of Chemical Engineering and Advanced Materials , the University of Adelaide, the Institute for Photonics and Advanced Sensing ( IPAS ), the Monash Institute of Pharmaceutical Sciences ( MIPS ) and Monash University . This work was performed in part at the Melbourne Centre for Nanofabrication (MCN) in the Victorian Node of the Australian National Fabrication Facility (ANFF).
Publisher Copyright:
© 2022 Elsevier B.V.
PY - 2022/3/15
Y1 - 2022/3/15
N2 - Identification and quantification of per- and polyfluoroalkyl substances (PFASs) remain challenging due to their chemical diversity, and their inert optical and chemical nature. Here, we present an optical system integrating perfluorosilane-functionalized nanoporous anodic alumina (NAA) interferometers with reflectometric interference spectroscopy (RIfS) for real-time, label-free detection of self-assembled monolayers (SAMs) of perfluorooctanoic acid (PFOA) as a model PFAS. Measured changes in the effective optical thickness (ΔOTeff) of NAA interferometers made it possible to study the fluorous interaction-induced self-assembly of PFOA molecules with perfluorosilane functional molecules of varying length, in real time and in situ. Analysis of key sensing parameters—sensitivity, low limit of detection and linearity—allowed us to determine the most optimal molecular length of perfluorosilanes to maximize immobilization of PFOA onto functional surfaces. Freundlich and Langmuir isotherm models were adapted to experimentally acquired values of ΔOTeff to elucidate the mechanism of PFOA–perfluorosilane interactions. Interpretation of these models suggests that PFOA binds to perfluorosilanes functional groups immobilized onto the inner surface of NAA interferometers through a fluorous interaction-induced Freundlich mechanism. The potential real-life applicability of this system was demonstrated by detecting the formation of PFOA-based SAMs in aqueous matrices of varying complexity (i.e. ultrapure, deionized, tap, and river water). This study provides new insights into how functional surface chemistries can be engineered to maximize sensitivity and selectivity to PFAS, harnessing fluorous interactions—with implications for future deployable systems to detect and remove these emerging toxicants.
AB - Identification and quantification of per- and polyfluoroalkyl substances (PFASs) remain challenging due to their chemical diversity, and their inert optical and chemical nature. Here, we present an optical system integrating perfluorosilane-functionalized nanoporous anodic alumina (NAA) interferometers with reflectometric interference spectroscopy (RIfS) for real-time, label-free detection of self-assembled monolayers (SAMs) of perfluorooctanoic acid (PFOA) as a model PFAS. Measured changes in the effective optical thickness (ΔOTeff) of NAA interferometers made it possible to study the fluorous interaction-induced self-assembly of PFOA molecules with perfluorosilane functional molecules of varying length, in real time and in situ. Analysis of key sensing parameters—sensitivity, low limit of detection and linearity—allowed us to determine the most optimal molecular length of perfluorosilanes to maximize immobilization of PFOA onto functional surfaces. Freundlich and Langmuir isotherm models were adapted to experimentally acquired values of ΔOTeff to elucidate the mechanism of PFOA–perfluorosilane interactions. Interpretation of these models suggests that PFOA binds to perfluorosilanes functional groups immobilized onto the inner surface of NAA interferometers through a fluorous interaction-induced Freundlich mechanism. The potential real-life applicability of this system was demonstrated by detecting the formation of PFOA-based SAMs in aqueous matrices of varying complexity (i.e. ultrapure, deionized, tap, and river water). This study provides new insights into how functional surface chemistries can be engineered to maximize sensitivity and selectivity to PFAS, harnessing fluorous interactions—with implications for future deployable systems to detect and remove these emerging toxicants.
KW - Nanoporous anodic alumina
KW - Perfluorooctanoic acid (PFOA)
KW - Perfluorosilanes
KW - Reflectometric interference spectroscopy
KW - Self-assembled monolayers
UR - http://www.scopus.com/inward/record.url?scp=85122189444&partnerID=8YFLogxK
U2 - 10.1016/j.snb.2021.131340
DO - 10.1016/j.snb.2021.131340
M3 - Article
AN - SCOPUS:85122189444
SN - 0925-4005
VL - 355
JO - Sensors and Actuators B: Chemical
JF - Sensors and Actuators B: Chemical
M1 - 131340
ER -