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Tom Steentjes

 ‘Self-assembled monolayers probed by electrochemistry: from layer properties to sensors’

 






In this thesis two different types of monolayer surfaces are described, with the aim to tune and study their electron transfer properties. ‘Self-assembled monolayers (SAMs) provide a highly tunable platform,’ says Tom Steentjes. ‘The layers can be implemented on metallic electrodes, for the use of electrochemical techniques.’

First, six multivalent β-cyclodextrin (β-CD) adsorbates are described, thereby focusing on: the effect of different functional groups on the adsorption kinetics, thickness and layer stability.

The adsorbates were designed with their cavity in close contact to a gold electrode. ‘Decreasing the distance between the β-CD core and the underlying substrate, led to an increase in the electron transfer rates,’ Tom concluded.

Also studied within this PhD thesis work: the electron transfer to and from ferrocene (Fc) moieties, tethered to long linear poly(ethylene glycol) (PEG) molecules attached to a gold electrode. ‘It was made possible to shuttle electrons between two nanospaced electrodes,’ Tom says. ‘This provided a powerful mechanism for signal-enhanced biosensor devices.

Looking from an electrochemical point of view towards novel detection principles in biological research, was the general outlook for this PhD work.

‘Conventional DNA detection tools involve long chains of molecules using covalent bonds on a single electrode,’ Tom Steentjes says. ‘The use of a second electrode to enhance the signal has been done before. But we were one of the first researchers to actually  attach them to electrodes inside a nanogap device without the need for mediators, in order to characterize them properly.’

Mutual interest

The two layers under investigation in this PhD work differ in fabrication technology, whereas the characterization methods are comparable. ‘In this project we collaborated closely with the BIOS labs-on-a-chip Group,’ Tom says. ‘We had a mutual interest in this project: they provided their expertise on fabricating, I brought in mine on testing and characterizing the electrochemical properties.’

The BIOS labs-on-a-chip Group provided their expertise on fabricating, I brought in mine on testing and characterizing the electrochemical properties

‘Also the involvement of the Nanoionics Group was inspiring, especially for formulating the research steps in the second part of the PhD work. I learned to know their expertise and experience on functionalized platinum electrodes and nanodevices during monthly strategic orientation meetings within Mesa+.’

Electrochemistry

Learning more on functionalized materials and using characterizing instruments such as Atomic Force Microscopy and InfraRed and Fluorescence Microscopy, Tom added to his skills. ‘Especially I learnt a lot on electrochemical processes,’ he says.

‘This was a new expertise field for me. I found out that electrochemistry is key in many research topics. Electrons literally are everywhere! I am glad to have gained extra knowledge, as many people are somewhat discouraged by this complex field.’

I found out that electrochemistry is key in many research topics. Electrons literally are everywhere!

Future job

As to his future Tom would like to work in industry.

Tom: ‘The academic route does not appeal to me. After a postdoc job, one has to choose, either a job as a professor or then pursue a career in industry. The size of the company to work at, doesn’t matter so much to me. Especially in The Netherlands, I believe research teams are quite informal in nature, both in smaller and in bigger companies. More important to me is the R&D aspect of the job. During the PhD project, I loved coming up with new ideas and new experimental setups.’

The size of the company to work at, doesn’t matter so much to me. Especially in The Netherlands, I believe research teams are quite informal in nature, both in smaller and in bigger companies.