Date of Graduation

12-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Microelectronics-Photonics (PhD)

Degree Level

Graduate

Department

Microelectronics-Photonics

Advisor/Mentor

Omar Manasreh

Committee Member

Simon Ang

Second Committee Member

Jiali Li

Third Committee Member

Jingxian Wu

Fourth Committee Member

Rick Wise

Keywords

Electrochemical, Enzyme, Glucose Sensors, Nanorods, Silicon Nanowires, ZnO

Abstract

Electrochemical sensors based on the nanostructure of the semiconductor materials are of tremendous interest to be utilized for glucose monitoring. The sensors, based on the nanostructure of the semiconductor materials, are the third generations of the glucose sensors that are fast, sensitive, and cost-effect for glucose monitoring.

Glucose sensors based on pure zinc oxide nanorods (NRs) grown on different substrates, such ITO, FTO, and Si/SiO2/Au, were investigated in this research. Silicon nanowire (NW)- based glucose sensors were also studied. First, an enzyme-based glucose sensor was fabricated out of glass/ITO/ZnO NRs/BSA/GOx/nafion membrane. The sensor was tested amperometrically at different glucose concentrations. The device showed a high sensitivity and a lower limit of detection in the order of 10.911 mA/cm2 mM and 0.22 μM, respectively. In addition, the device exhibited a fast and a sharp amperometric time response of ~3 s with different glucose concentrations.

The high surface-to-volume ratio provided by the ZnO NRs was investigated by characterizing the sensor with and without the ZnO NRs grown on Si/SiO2/Au substrates. The sensor showed almost a negligible amperometric response to the changes in the glucose concentrations without ZnO NRs. After applying the ZnO NRs, the sensor exhibited a linear response to the glucose concentrations from 1-8 mM. Furthermore, very clear oxidation peaks were observed at the scan rates of 100 and 200 mV/s in the presence of 2 mM of the glucose. The device showed no dependency on different scan rates without applying the ZnO NRs.

An enzyme-free glucose sensor was fabricated based on ZnO NRs grown on FTO and modified with Fe2O3. The device showed a high sensitivity and a wide amperometric linear response on the order of 0.052 μA/cm2 and from 100-400 mg/dL, respectively. Reactive ion etching and nanosphere lithography methods were utilized to grow the Si NWs vertically on top of a silicon wafer. The sensor showed a high linearity from 1-9 mM for changes in glucose concentrations. In addition, the high surface-to-volume ratio provided by the Si NWs helped in adsorbing higher concentrations of the enzyme.

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