Development of optical sensor for detection of chloride ions and electrochemical sensor for detection of clinical indicators

Abstract

This dissertation concentrated on the development of nanomaterials-based miniaturized platforms for the detection of some important compounds/indicators from environmental, pharmaceutical, and clinical application. This dissertation can be classified into two main parts: (1) development of nanomaterials-based miniaturized platforms for optical sensing application, and (2) development of nanomaterials-based miniaturized platforms for electrochemical sensing applications. In the first part, two sub-sections were discussed. For the first sub-section, the paper-based colorimetric sensor for chloride ion determination using silver nanoprisms was developed. Using a smartphone as an optical readout, the color change from the oxidative etching of the silver nanoprisms to the silver nanospheres induced by chloride ion can be monitored. In the second sub-section, a screen-printed electroluminescent displaymodified with graphene oxidewas engineered for optical sensing applications for the first time. The potential of the proposed device was extended for a variety of applications, including a basic lamp, an ionic concentration sensor, a humidity sensor, and a human breath sensor. In the second part, electrochemical sensors were also developed. In this part, two sub-sections were discussed in detail. For the first sub-section, an anti-fouling electrochemical sensor for vitamin D determinationusing graphene/Nafion nanocompositewas developed. A greatly enhance in analytical performance and the anti-fouling capability was obtained. Lastly, in the second sub-section, a paper-based sequential microfluidic device modified with graphene and gold nanoparticles was developed for the fluid delivery system. Various target compounds including ascorbic acid, serotonin, and alpha-fetoprotein were chosen as model analytes and tested by the developed platform. Results obtained from these miniaturized devices demonstrated here provided a good promising for on-field testing with excellent sensitivity, selectivity, and portability.