Article Cite This: ACS Sens. 2017, 2, 1653-1661
pubs.acs.org/acssensors
Pulse-Driven Capacitive Lead Ion Detection with Reduced Graphene Oxide Field-Effect Transistor Integrated with an Analyzing Device for Rapid Water Quality Monitoring Arnab Maity,†,# Xiaoyu Sui,†,# Chad R. Tarman,† Haihui Pu,† Jingbo Chang,† Guihua Zhou,† Ren Ren,† Shun Mao,‡ and Junhong Chen*,† †
Department of Mechanical Engineering, University of Wisconsin-Milwaukee, 3200 North Cramer Street, Milwaukee, Wisconsin 53211, United States ‡ State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China S Supporting Information *
ABSTRACT: Rapid and real-time detection of heavy metals in water with a portable microsystem is a growing demand in the field of environmental monitoring, food safety, and future cyberphysical infrastructure. Here, we report a novel ultrasensitive pulse-driven capacitance-based lead ion sensor using selfassembled graphene oxide (GO) monolayer deposition strategy to recognize the heavy metal ions in water. The overall field-effect transistor (FET) structure consists of a thermally reduced graphene oxide (rGO) channel with a thin layer of Al2O3 passivation as a top gate combined with sputtered gold nanoparticles that link with the glutathione (GSH) probe to attract Pb2+ ions in water. Using a preprogrammed microcontroller, chemo-capacitance based detection of lead ions has been demonstrated with this FET sensor. With a rapid response (∼1−2 s) and negligible signal drift, a limit of detection (LOD) < 1 ppb and excellent selectivity (with a sensitivity to lead ions 1 order of magnitude higher than that of interfering ions) can be achieved for Pb2+ measurements. The overall assay time (∼10 s) for background water stabilization followed by lead ion testing and calculation is much shorter than common FET resistance/current measurements (∼minutes) and other conventional methods, such as optical and inductively coupled plasma methods (∼hours). An approximate linear operational range (5−20 ppb) around 15 ppb (the maximum contaminant limit by US Environmental Protection Agency (EPA) for lead in drinking water) makes it especially suitable for drinking water quality monitoring. The validity of the pulse method is confirmed by quantifying Pb2+ in various real water samples such as tap, lake, and river water with an accuracy ∼75%. This capacitance measurement strategy is promising and can be readily extended to various FET-based sensor devices for other targets. KEYWORDS: pulse capacitance, FET sensor, reduced graphene oxide, portable and rapid lead ion detection, real water analysis
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aging of the reference electrode, and background current instability. Also, the presence of a high concentration of common metal ions in real water can significantly impact the results. Therefore, rapid, portable, low cost automated detection of lead ions in water is in great demand. Graphene as a representative 2D material is found to be promising for FET-based sensor applications due to its unique one atomic layer structure, high specific surface area, great signal/noise ratio, excellent mechanical strength, and small size.4−6 Chemical exfoliation in the liquid phase can produce one atomic layer thickness of ultrafine nanosheets in large scale from bulk graphite. The high surface area of graphene can be functionalized with various ligands to attract metal ions,7−9
ecently, lead contamination and related health hazards has raised a serious global issue. Direct intake of lead through drinking water on a daily basis can affect the central nervous system, and the hematopoietic, hepatic, and renal system.1 An alarming level of increase of lead was found in the blood of people living in the city of Flint, Michigan, USA due to the poor conditions of the water supply system (lead leaching from the pipeline during the water conveyance).2,31−33 The conventional inductively coupled plasma mass spectrometry (ICPMS), atomic absorption spectroscopy (AAS), and atomic emission spectrometry (AES) tests are costly due to their long procedure, bulky setup, and need for a professional operator.3 Electrochemical stripping analysis using voltammetry has also been successfully used for measuring various metal ions in trace level selectively with high reproducibility.35−37 However, it is limited by working electrode maintenance with proper cleaning, reduction/oxidation potential peak position drifting due to the © 2017 American Chemical Society
Received: July 18, 2017 Accepted: October 17, 2017 Published: October 31, 2017 1653
DOI: 10.1021/acssensors.7b00496 ACS Sens. 2017, 2, 1653−1661
Article
ACS Sensors Table 1. Comparison of Capacitance-Based Sensing Performance with Other Techniques Reported in the Literature sensing materials and test method
concentration detected (nM) and chemical target 2+
1.7%
rGO/GSH-Au NPs (DC)
10 nM Pb
Ti3C2−MXene (DC) Graphene/olfactory receptors (DC)
100 nM dopamine 0.04 × 10−6 nM odorant (amyl butyrate) 10 000 nM Hg2+
PII2T-Si polymer/33-base thiolated DNA probeAu NPs (DC) Polypyrrole/rGO (DC)
0.1 nM H2O2
Pt NPs/rGO (DC) Bismuth-coated carbon electrodes (stripping voltammetry) rGO/GSH-Au NPs (Pulse)
2.4 nM SsDNA 1−150 ppb Pb2+
a
response (%)
