Investigating Electrochemical Behavior of Biosensor Based on Vertically Aligned Carbon Nanotubes
Gholizadeh, Azam | 2013
- Type of Document: Ph.D. Dissertation
- Language: Farsi
- Document No: 44085 (48)
- University: Sharif University of Technology
- Department: Institute for Nanoscience and Nanotechnology
- Advisor(s): Shahrokhian, Saeed; Iraji Zad, Azam; Mohajerzadeh, Shamsoddin; Vossoughi, Manoochehr
- In this research we focus on fabrication, characterization and performance of biosensors based on vertically aligned carbon nanotubes. Carbon nanotubes have been used as high density carbon nanotubes and nanoelectrode array. Carbon nanotubes have been grown using plasma enhanced chemical vapor deposition method. Characterization and performance of biosensors have been studied by cyclic voltammetry and electrochemical impedance spectroscopy methods.
The mediator-less glutamate biosensor is prepared based on covalently attached glutamate dehydrogenase on vertically aligned carbon nanotubes. The biosensor has a low detection limit of 57 nM, two linear range of 0.1-20 µM with sensitivity of 0.976 mA mM-1 cm-2 and the range of 20-300 µM with sensitivity of 0.182 mA mM-1 cm-2. The effect of the other biological compounds on the voltammetric behavior of the prepared biosensor and its response stability have been investigated. The results demonstrated that the GLDH/VACNTs electrode, even without electron mediator, is a suitable electrode for detection of glutamate.
For fabrication of nanoelectrode array, nickel catalyst layer has been patterned by UV and nanosphere lithography methods. Carbon nanotubes have been grown with 3 µm distance from each other. Passivation layer of silicon dioxide has been deposited on carbon nanotubes using RF plasma enhanced vapor deposition method. Then chemical mechanical polishing method has been used for planarization of silicon dioxide layer and opening the tips of carbon nanotubes. The fabricated array illustrated sigmoidal cyclic voltammogram with steady state current dominated by radial diffusion.
The nanoelectrode array was employed as electrochemical glutamate biosensor. The performance of the biosensor based on nanoelectrodes array was compared with the biosensor based on high density vertivally aligned carbon nanotubes. By using the fabricated nanoelectrode array, the sensitivity increased approximately to a value of 2180 mA mM-1 cm-2 in the range of 0.1-20 µM and to 100 mA mM1 cm-2 in the range of 20-300 µM glutamate. By using this electrode a record of detection limit of 10 nM was achieved for glutamate
- Vertically Aligned Carbon Nanotubes ; Plasma Enhanced Chemical Vapor Deposition (PECVD) ; Nanoelectrode Array ; PhotoLithography ; Glutamate Electrochemical Biosensor ; Nanosphere Lithography