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Electrochemical functionalization of epitaxial graphene

Lindgren, Petter LU (2015) BMEM01 20151
Department of Biomedical Engineering
Abstract
In this work graphene has been functionalized with antibodies. Different functionalization methods of graphene already found in literature have been evaluated. An electrochemical functionalization process with subsequent immobilization of antibodies have been chosen for this thesis.
The purpose of the thesis has been formulated in collaboration with Graphensic AB. From them a wish to implement an electrochemical cell has been brought up. If graphene could be functionalized it could be used as an electrode in an electrochemical cell to measure many different processes.
Four graphene samples have been used, all of them manufactured by Graphensic AB. The graphene has been grown epitaxially on the silicon terminated surface of 4H-silicon... (More)
In this work graphene has been functionalized with antibodies. Different functionalization methods of graphene already found in literature have been evaluated. An electrochemical functionalization process with subsequent immobilization of antibodies have been chosen for this thesis.
The purpose of the thesis has been formulated in collaboration with Graphensic AB. From them a wish to implement an electrochemical cell has been brought up. If graphene could be functionalized it could be used as an electrode in an electrochemical cell to measure many different processes.
Four graphene samples have been used, all of them manufactured by Graphensic AB. The graphene has been grown epitaxially on the silicon terminated surface of 4H-silicon carbide. The samples have been of a high quality, three of them were monolayers, monolayer compromising more than 95% of the surface, and one a bilayer, bilayer compromising more than 50 % of the surface.
The functionalization could be divided into two steps. First the attachment of aryl radicals to the graphene surface. Then the attachment of antibodies to these aryls, both a primary antibody and a secondary. The attachment of aryl radicals were done in an electrochemical cell utilizing a diazonium salt. The decomposition of the diazonium salt into aryl radicals was driven electrochemically in the cell.
The graphene samples were measured electrochemically between each functionalization step so that the changes could be evaluated. The impedance and the peak values of the cyclic voltammograms increased after the diazonium salt step. They then decreased again to values close to the initial value when attaching antibodies. The attachment of the secondary antibody slightly increased the peak values of the cyclic voltammogram.
The secondary antibody contained a fluorescent molecule which was used to evaluate the functionalization. For two of the samples this showed that the functionalization most likely had been successful. For the other two it was hard to distinguish whether or not it had been successful. (Less)
Popular Abstract
Graphene, world’s thinnest material, made useable
World’s thinnest material graphene, as thin as a single atom but consisting of millions of atoms. By attaching molecules from our own immune system to it quick diagnostics might be possible. This attachment has been shown to be possible.
Graphene, long thought to be an impossible material, was first produced in the early 2000s. Graphene has many extreme properties, it is incredibly strong, conducts electricity and heat incredibly good and is of course as thin as it gets. However just as graphene is incredibly strong it is also very hard to modify.
The part of the immune system that have been combined with graphene are molecules called antibodies. Antibodies can be found in our blood and... (More)
Graphene, world’s thinnest material, made useable
World’s thinnest material graphene, as thin as a single atom but consisting of millions of atoms. By attaching molecules from our own immune system to it quick diagnostics might be possible. This attachment has been shown to be possible.
Graphene, long thought to be an impossible material, was first produced in the early 2000s. Graphene has many extreme properties, it is incredibly strong, conducts electricity and heat incredibly good and is of course as thin as it gets. However just as graphene is incredibly strong it is also very hard to modify.
The part of the immune system that have been combined with graphene are molecules called antibodies. Antibodies can be found in our blood and are part of the first line of defense against sickness. They attach to harmful substances in our blood and signal the body to destroy them. By attaching the antibodies to graphene it is possible to detect when if the antibodies have attached to harmful substances and thus it is possible to detect if someone is sick or not. This can be detected by applying a voltage to the graphene and measure the current. If the antibodies have attached to a harmful substance the current will change.
Attaching anything to graphene is not easy. Graphene is a very stable material and is quite satisfied with being the way it is. To be able to attach an antibody first another molecule has been used to break up the graphene. A small molecule called an aryl radical which is very reactive was used. This molecule attached to the graphene and then the antibodies were attached to them. Normally attaching this aryl radical takes many hours but by using a smart trick it only takes a few seconds. If a molecule called a diazonium salt is put together with the graphene a current can be used to produce aryl radicals from the diazonium salt. Then the aryl radicals will have no choice but to attach to the graphene.
The work has shown that attaching antibodies to graphene is possible and that the function of the antibodies is detectable by electrical measurements. The way of attaching the antibodies is such that after the initial attachment of aryl radical the antibodies can be switched to any other biomolecule. Using this initial step graphene can be modified with almost any biomolecule, increasing its usefulness massively. (Less)
Please use this url to cite or link to this publication:
author
Lindgren, Petter LU
supervisor
organization
course
BMEM01 20151
year
type
H2 - Master's Degree (Two Years)
subject
language
English
additional info
2015-04
id
5276630
date added to LUP
2015-04-20 09:19:50
date last changed
2015-04-20 09:19:50
@misc{5276630,
  abstract     = {In this work graphene has been functionalized with antibodies. Different functionalization methods of graphene already found in literature have been evaluated. An electrochemical functionalization process with subsequent immobilization of antibodies have been chosen for this thesis.
The purpose of the thesis has been formulated in collaboration with Graphensic AB. From them a wish to implement an electrochemical cell has been brought up. If graphene could be functionalized it could be used as an electrode in an electrochemical cell to measure many different processes.
Four graphene samples have been used, all of them manufactured by Graphensic AB. The graphene has been grown epitaxially on the silicon terminated surface of 4H-silicon carbide. The samples have been of a high quality, three of them were monolayers, monolayer compromising more than 95% of the surface, and one a bilayer, bilayer compromising more than 50 % of the surface.
The functionalization could be divided into two steps. First the attachment of aryl radicals to the graphene surface. Then the attachment of antibodies to these aryls, both a primary antibody and a secondary. The attachment of aryl radicals were done in an electrochemical cell utilizing a diazonium salt. The decomposition of the diazonium salt into aryl radicals was driven electrochemically in the cell.
The graphene samples were measured electrochemically between each functionalization step so that the changes could be evaluated. The impedance and the peak values of the cyclic voltammograms increased after the diazonium salt step. They then decreased again to values close to the initial value when attaching antibodies. The attachment of the secondary antibody slightly increased the peak values of the cyclic voltammogram.
The secondary antibody contained a fluorescent molecule which was used to evaluate the functionalization. For two of the samples this showed that the functionalization most likely had been successful. For the other two it was hard to distinguish whether or not it had been successful.},
  author       = {Lindgren, Petter},
  language     = {eng},
  note         = {Student Paper},
  title        = {Electrochemical functionalization of epitaxial graphene},
  year         = {2015},
}