Development of portable electrochemical sensors for determination of heavy metals, nitrogen oxides and thiocyanate ion

Abstract

This dissertation focused on the development of portable electrochemical sensors using the paper-based analytical device (ePAD) for the determination of the important compounds/biomarkers in various applications. Considering the target applications, this dissertation can be divided into three main parts including food safety application, environmental analysis and clinical application, respectively. In the first part, two sub-sections relating to the detection of heavy metals contaminated in food will be discussed. For the first sub-section, an ePAD coupled with a boron-doped diamond electrode was developed for the determination of total arsenic. The device was performed using the origami paper device for the preparation of gold nanoparticle-modified boron-doped diamond electrodes and the measurement of arsenic (III) using anodic stripping voltammetry on a single device. For the second sub-section, an ePAD coupled with a portable potentiostat was demonstrated for the simultaneous determination of tin and lead using a bismuth nanoparticle-modified screen-printed graphene electrode as working electrode. In the second part, an ePAD was engineered for NOx gas determination as a model for environmental analysis. The functionality of the developed platform was enhanced by integrating the gas absorber and copper nanoparticle-modified screen-printed graphene electrode within the same device for selective capturing. This novel gas sensing device could be applied to determine NOx gas in various gaseous samples, such as air and exhaust gases from cars with high accuracy and reliability. Lastly, an ePAD coupled with colorimetric detection was demonstrated for the biological sensing of salivary thiocyanate. Here, the microcapillary grooves fabricated on a paper device functioned as a microcapillary pump to facilitate the viscous salivary transportation along the microfluidic channel without requiring for sample pretreatment steps/bulky instrumentations. All in all, these ePAD formats exhibited good performances for the practical analysis and allowed for further development of an advanced platform.