Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Electrical Engineering and Computer Science

First Advisor

Qiquan Qiao


The goal of this work was to develop electrochemical sensors for heavy metal ions (e.g., Cd2+, Hg2+, Pb2+) and phosphate detections in fertilizers with high sensitivity, high detection range, repeatability and portability. The heavy metal electrochemical sensors were made using novel graphene oxide/silver nanowire (GO/AgNWs) composite as working electrode. The phosphate electrochemical sensors were fabricated using ammonium molybdate tetrahydrate/silver nanowires (AMT/AgNWs) modified screen printed electrode. Most of the heavy metals such as mercury, lead, cadmium, and arsenic have dangerous effects on human body. These ions can enter human body system via agriculture food chain such as fish. Phosphorous-containing fertilizer is imperative to plant and animal nutrition. Essential biomolecules of the human body and plant growth depend upon the proper availability of phosphate ions in the fertilizer. There is a need for inexpensive, portable, repeatable, highly sensitive and field deployable sensors with high detection range to monitor the health of the field soil. Mercury, lead and cadmium ions have oxidation peaks at three different potentials, which indicates good selectivity of the GO/AgNWs sensing electrode. In this experiment, the sensitivities of the GO/AgNW working electrode sensors are found to be 7.89 μA/μM, 4.21 μA/μM, 2.63 μA/μM for Cd2+, Hg2+, Pb2+ respectively. The detection ranges of these sensors are very broad at 5μM - 10 mM. From cyclic voltammetry measurements, the sensitivities of AMT modified SPE without and with AgNWs are 0.1 μA/μM and 0.71 μA/μM with a detection range of 5 μM - 50 mM. Therefore, the use of AgNWs increased the sensitivity of the AMT modified SPE significantly. I-V curves showed the sensitivities of the SPE without and with AgNWs are 0.2 Ω/μM and 1.6 Ω/μM, respectively. The sensors response shows a negative linear (R∞1/Q) relation between concentration (Q) and resistance (R). The repeatability tests show an error of only 5-6%. The sensing electrodes including GO/AgNWs composite film for heavy metal detection and AMT/AgNWs for phosphate ion detection invented in this work can be a potentially simple, low-cost system owing to easy fabrication processes and use of inexpensive materials; and portable as it is small and needs less equipment to collect data for field deployment.

Library of Congress Subject Headings

Electrochemical sensors.
Metal ions.
Fertilizers -- Health aspects.


Includes bibliographical references (pages 52-53)



Number of Pages



South Dakota State University


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