Two-Dimensional Nanomaterials and Their Composites for Electrochemical Detection of Toxic Mercury Ions in Water

Author

Md Tawabur Rahman, South Dakota State UniversityFollow

Document Type

Dissertation - Open Access

Award Date

2020

Degree Name

Doctor of Philosophy (PhD)

Department / School

Electrical Engineering and Computer Science

First Advisor

Qiquan Qiao

Keywords

Electrochemical, Graphene oxide, Mercury, microflowers, silver nanowires, WS2

Abstract

The presence of trace amounts of mercury ion (Hg²⁺) in drinking water has a detrimental effect on human health. The development of an electrochemical sensor for Hg²⁺ detection is still challenging to obtain ultra-trace sensitivity, excellent selectivity, wide Linear Detection Ranges (LDRs), and ultra-low detection limit. This work presents an electrochemical sensor based on two-dimensional nanomaterials and their composites for the enhanced sensing of Hg²⁺ in water. Graphene oxide (GO)-silver nanowires (AgNWs) composite and metallic 1T phase tungsten disulfide (WS2) microflowers were utilized for the fabrication of electrochemical sensors using drop-casting. Under the optimized experimental conditions, the GO-AgNWs composite modified sensor showed a high sensitivity of ~ 0.29 μA/nM and linear response in the range of 1-70 nM toward Hg²⁺, whereas 1T-WS2 microflowers modified sensor showed excellent sensitivities of ~ 15.9 μA/μM, 2.54 μA/μM, 13.84 μA/μM, and 0.04646 μA/μM toward Hg²⁺ with LDRs of 1- 90 nM, 0.1-0.4 μM, 0.5-1.0 μM, and 0.1-1.0 mM, respectively. An ultra-low detection limit of 0.1 nM and 0.0798 nM or 79.8 pM toward Hg²⁺ was obtained by GO-AgNWs composite and 1T-WS₂ modified sensors, which are well below the guideline value recommended by the World Health Organization and the United States Environmental Protection Agency. The sensors exhibited excellent selectivity for Hg2+ against other heavy metal ions including Cu²⁺, Fe³⁺, Ni²⁺, Pb²⁺, Cr³⁺, K⁺, Na⁺, Ag+, Sn²⁺, and Cd²⁺. The thus obtained excellent sensitivity and selectivity with wide LDRs and ultra-low detection limits can be attributed to the synergistic effect of GO and conductive AgNWs, high conductivity, large surface area microflower structured 1T-WS², and the complexation of Hg²⁺ ions with sulfur (S2-) and GO. In addition to good repeatability, reproducibility, and stability, these sensors showed practical feasibility of Hg²⁺ detection in tap water suggesting a promising device for real applications.

Library of Congress Subject Headings

Mercury -- Toxicology.
Nanostructured materials.
Metal ions.
Electrochemical sensors.
Electrochemical analysis.
Drinking water -- Contamination.
Nanocomposites (Materials)

Format

application/pdf

Number of Pages

161

Publisher

South Dakota State University

Recommended Citation

Rahman, Md Tawabur, "Two-Dimensional Nanomaterials and Their Composites for Electrochemical Detection of Toxic Mercury Ions in Water" (2020). Electronic Theses and Dissertations. 4020.
https://openprairie.sdstate.edu/etd/4020