A Fully Inkjet-Printed Sensor for Electrochemical Detection of Heavy Metals
Authors: Shamkhalichenar Hamed , Choi Jin-Woo 
Published: February 2020

Heavy metals are present in soil and water as a non-degradable element in environment usually in their cationic form. Some of these metals, such as iron, copper, etc. are crucial for life. On the other hand, some of them are toxic such as lead (Pb) that could cause a detrimental effect on the human nervous system and cadmium (Cd) that could cause damage to kidney [1]. Various detection methods have been employed to determine Pb(II) and Cd(II) concentration including atomic absorption, emission spectroscopy, inductively-coupled plasma mass spectrometry, cold vapor atomic fluorescence spectrometry, and electrochemical analysis. Among them, electrochemical analysis has gained more attention due to its high selectivity, high sensitivity, low cost, and simple determination process [2]. Stripping voltammetry in conjunction with mercury-based electrodes was initially used in heavy metal electrochemical sensing platforms, but due to the toxicity of mercury, bismuth-based electrodes has become a good alternative for electrochemical detection of heavy metals. Bismuth (Bi), an environmentally-friendly element, offers a wide electrochemical window, low background current, and clear separation between neighboring peaks [3, 4].
Employing paper to develop sensing platforms has become popular in recent years due to, porous structure and extremely low cost. Paper-based electrochemical sensors can be good candidate for environmental analysis especially in the resource limited areas due to their extremely low cost [5]. In this work, we present a fully inkjet-printed electrochemical sensor for determination of Pb(II) and Cd(II). Inkjet-printed sensors offer many advantages including mass automated printing process, uniform deposition and low waste of the materials, and scalable manufacturing comparing to the conventional screen printing approach. The sensor basic design structure is illustrated in the figure. The inkjet printing process was based on our previously development described in [6, 7]. In situ plating of the Bi on the carbon nanotube electrode occurred at the preconcentration step of the anodic stripping voltammetry by applying negative voltage to the working electrode. Acetate buffer solution containing various amount of Pb(II) and Cd(II) was then introduced to the presented paper-based sensing platform, and the anodic stripping analysis has been performed to determine the Pb(II) and Cd(II) concentration.
References
[1] G. March, T. Nguyen, and B. Piro, “Modified Electrodes Used for Electrochemical Detection of Metal Ions in Environmental Analysis,” Biosensors, vol. 5, no. 2, pp. 241–275, 2015.
[2] M. B. Gumpu, S. Sethuraman, U. M. Krishnan, and J. B. B. Rayappan, “A review on detection of heavy metal ions in water - An electrochemical approach,” Sensors Actuators, B Chem., vol. 213, pp. 515–533, 2015.
[3] J. Wang, J. Lu, S. B. Hocevar, P. A. M. Farias, and B. Ogorevc, “Bismuth-coated carbon electrodes for anodic stripping voltammetry,” Anal. Chem., vol. 72, no. 14, pp. 3218–22, 2000.
[4] J. Wang, “Stripping analysis at bismuth electrodes: A review,” Electroanalysis, vol. 17, no. 15–16, pp. 1341–1346, 2005.
[5] J. Adkins, K. Boehle, and C. Henry, “Electrochemical paper-based microfluidic devices,” Electrophoresis, vol. 36, no. 16, pp. 1811–1824, 2015.
[6] T. H. da Costa, E. Song, R. P. Tortorich, and J.-W. Choi, “A Paper-Based Electrochemical Sensor Using Inkjet-Printed Carbon Nanotube Electrodes,” ECS J. Solid State Sci. Technol., vol. 4, no. 10, pp. S3044–S3047, 2015.
[7] A. Economou, “Bismuth-film electrodes: Recent developments and potentialities for electroanalysis,” TrAC - Trends Anal. Chem., vol. 24, no. 4, pp. 334–340, 2005.

Figure 1