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Open AccessArticle

Epitaxial Graphene Sensors Combined with 3D-Printed Microfluidic Chip for Heavy Metals Detection

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Applied Sensors Science, Department of Physics, Chemistry, and Biology-IFM, Linköping University, S-58183 Linköping, Sweden
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Semiconductor Materials, Department of Physics, Chemistry, and Biology-IFM, Linköping University, S-58183 Linköping, Sweden
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Optical Devices Laboratory, Department of Physics, Chemistry, and Biology-IFM, Linköping University, S-58183 Linköping, Sweden
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Division of Physics and Electronics, Department of Science and Technology, Physics and Electronics-ITN, Linköping University, SE-58183 Linköping, Sweden
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Author to whom correspondence should be addressed.
Sensors 2019, 19(10), 2393; https://doi.org/10.3390/s19102393
Received: 17 April 2019 / Revised: 13 May 2019 / Accepted: 22 May 2019 / Published: 25 May 2019
(This article belongs to the Section Chemical Sensors)
In this work, we investigated the sensing performance of epitaxial graphene on Si-face 4H-SiC (EG/SiC) for liquid-phase detection of heavy metals (e.g., Pb and Cd), showing fast and stable response and low detection limit. The sensing platform proposed includes 3D-printed microfluidic devices, which incorporate all features required to connect and execute lab-on-chip (LOC) functions. The obtained results indicate that EG exhibits excellent sensing activity towards Pb and Cd ions. Several concentrations of Pb2+ solutions, ranging from 125 nM to 500 µM, were analyzed showing Langmuir correlation between signal and Pb2+ concentrations, good stability, and reproducibility over time. Upon the simultaneous presence of both metals, sensor response is dominated by Pb2+ rather than Cd2+ ions. To explain the sensing mechanisms and difference in adsorption behavior of Pb2+ and Cd2+ ions on EG in water-based solutions, we performed van-der-Waals (vdW)-corrected density functional theory (DFT) calculations and non-covalent interaction (NCI) analysis, extended charge decomposition analysis (ECDA), and topological analysis. We demonstrated that Pb2+ and Cd2+ ions act as electron-acceptors, enhancing hole conductivity of EG, due to charge transfer from graphene to metal ions, and Pb2+ ions have preferential ability to binding with graphene over cadmium. Electrochemical measurements confirmed the conductometric results, which additionally indicate that EG is more sensitive to lead than to cadmium. View Full-Text
Keywords: heavy metals detection; epitaxial graphene; high sensitivity; 3D-printed flow cell; reusable lab-on-chip heavy metals detection; epitaxial graphene; high sensitivity; 3D-printed flow cell; reusable lab-on-chip
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Santangelo, M.F.; Shtepliuk, I.; Filippini, D.; Puglisi, D.; Vagin, M.; Yakimova, R.; Eriksson, J. Epitaxial Graphene Sensors Combined with 3D-Printed Microfluidic Chip for Heavy Metals Detection. Sensors 2019, 19, 2393.

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