Development of nanostructured material based electrochemical sensors for food safety and quality control
Manikandan, Venkatesh S.
Doctor of Philosophy
Food safety and quality control
Food additives and contaminants (detection)
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The issue of foodborne related illnesses due to additives and contaminants poses a significant challenge to food processing industries. Electrochemical-based strategies offer simple and robust analytical tools, which are ideal for food safety and the quality assessment process, in contrast to conventional instrumentation methods. The development of nanomaterials based electrochemical sensors has garnered significant attention due to their capacity for accurate analytical quantification, which has strong potential toward the replacement of conventional techniques by offering advantages such as high sensitivity and selectivity, real-time monitoring, and ease of use. During my Ph.D. study, four distinct types of nanostructured materials were used to develop electrochemical sensors for the detection of food preservatives in food and beverage products. The consumption of excessive amounts of nitrite (NO2-) can be detrimental to the human body. In light of this, we developed an electrochemical sensor based on cobalt oxide nanosheets and gold nanoparticles (Co3O4/Au) for NO2- sensing. The nanomaterial was synthesized through the electrodeposition of gold (Au) on Co3O4 nanosheets. The Co3O4/Au/GCE was capable of electrooxidizing nitrite with a higher anodic peak current, and the sensor exhibited excellent linearity with a limit of detection (LOD) value of 0.11 μM. A nanoporous gold microelectrode was synthesized for the determination of contaminants (hydrazine, N2H4) and preservatives (sulfite (SO32-), nitrite (NO2-)). The fabricated microelectrode was characterized via scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). The nanoporous gold microelectrode exhibited excellent electrochemical performance for the simultaneous electrochemical oxidation of N2H4, SO32-, and NO2-. In addition, the nanoporous gold microelectrode possessed high selectivity and stability. The performance of ii the electrochemical sensor was further validated using actual samples such as water, wine, apple cider beer, and beef with good recovery rates, thereby confirming its potential for food safety and quality control applications. A novel electrochemical sensor was developed using fluorine-doped graphene oxide (F-GO) for the detection of caffeic acid (CA). The fabricated nanomaterial was systematically characterized using SEM and X-ray photoelectron spectroscopy (XPS). The electrochemical investigation of F-GO/GCE for CA oxidation revealed that it demonstrated high electrocatalytic activity compared with other electrodes (e.g., bare GCE and GO/GCE). The analytical quantitation of CA recorded with the F-GO/GCE produced a stable oxidation signal over the selected CA concentration range (0.5 μM to 100.0 μM, R2 = 0.9960) with a LOD value of 0.018 μM. The fabricated sensor successfully exhibited the capacity to directly detect CA in assorted wine samples without pretreatment. To further explore the applications of the F-GO, a nanocomposite material synthesized with Au and F-GO was employed for the development of an Au/F-rGO/GCE sensor for the detection of vanillin. The electrochemical performance and the analytical capabilities of this novel electrochemical sensor were investigated using electrochemical techniques such as CV and DPV. The excellent sensitivity, selectivity, augmented electrocatalytic activity, and reproducibility of these developed electrochemical sensors can be attributed to the high conductivity of the nanostructured materials. The dimensions and morphologies of the developed nanomaterials played a critical role in enhancing the electrochemical performance of these sensors.