Fabrication and Characterization of Vertically Aligned Carbon Nanofibers (VACNF) as Amperometric Biosensors on a Silicon-Compatible Platform

This thesis presents fabrication, characterization and initial results of vertically aligned carbon nanofibers (VACNF)-based electrodes for use as electrochemical sensors. VACNFs are nanostructures that can be fabricated to the desired specifications using a plasma-enhanced chemical-vapor deposition process and are ideal candidates for electrode material because of their excellent electrical and structural properties. The first step of the fabrication of VACNFs on silicon substrates involved photolithography to pattern the interconnects and the catalysts (nickel dots). VACNFs were then grown on silicon substrates from the nickel catalysts, whose size determines the growth of a single nanofiber or a forest of nanofibers. This work presents a method for growth of nanofiber forest for redundancy and uniform vertical growth.

A reservoir was built around the nanofibers to keep the liquid samples in contact with the nanofibers during testing. Nanofiber electrodes were characterized electrochemically using ruthenium hexamine trichloride to ensure proper functionality. The biosensor is customizable to selectively detect various elements or compounds depending on the binding materials used on the nanofibers. One example of a sample that can be detected with VACNF electrodes is glucose. The enzymes, horseradish peroxidase and glucose oxidase, were applied to the nanofibers and were immobilized for the testing of glucose. The reference electrode of the electrochemical analyzer was inserted into the reservoir containing the glucose and multiple analyses were performed. The nanofiber electrodes were able to collect the electrons from the electrochemical reactions of glucose and the enzymes. Amperometric data was gathered for the oxidation and reduction potentials and the current was measured as a function of the glucose concentration.

Vertically aligned carbon nanofibers fabricated on silicon substrates are ideal electrodes for integration with silicon compatible structures such as complementary metal-oxide-semiconductor (CMOS) microelectronics based transmitting and signal processing integrated circuits.