University of Twente Student Theses


Electrochemically controlled gradients : towards directed motion of molecules

Veerbeek, Janneke (2012) Electrochemically controlled gradients : towards directed motion of molecules.

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Abstract:Directed motion of molecules is necessary for the controlled buildup of molecular architectures, local reactions at the nanoscale, and for fundamental understanding of processes at the molecular scale. While the synthesis of gradients has been studied extensively, almost no research has been performed on the directed motion of molecules by chemical gradients. The few studies available did not include any tunable and dynamic gradients. Therefore, the research performed in this project aimed for the directed motion of molecules by using electrochemically controlled gradients. Supramolecular chemistry and electrochemistry were combined because of their reversibility and tunability/downscaling characteristics, respectively. Multivalent interactions were used to ensure tunability by competition or electrochemistry instead of spontaneous desorption. At first, a covalent host surface gradient on glass was fabricated at the μm scale. Click chemistry was used to synthesize a surface gradient of coumarin units. CD molecules were reacted on top, thus forming a host surface gradient which could be visualized by fluorescence spectroscopy. Incubation with guest molecules led to a gradient in the wrong direction, which has to be further investigated. Secondly, a non-covalent surface gradient of guest molecules was created for the first time, to our knowledge. A solution gradient of FcMeOH was produced electrochemically, that acted as a competitor for Ad2-rhodamine on the CD printboard and resulted in a surface gradient of guest molecules at the μm scale. The direction of the gradient could be reversed by adding CD in solution. Further research is necessary to optimize the gradients, e.g. in steepness. Thirdly, directed motion was intended to occur via a surface gradient of host molecules, or a solution gradient of a host or competitor. Motion on the synthesized host and guest gradients was not tried yet. Directed motion was tested by unequal spreading of microcontact printed lines with a host solution gradient on top. This resulted in a higher spreading rate, but no directed spreading was observed. It is recommended to focus further research on the two successful systems, since these seem to be the most promising. Further research is needed to understand the systems completely and direct the motion of molecules by the produced gradients.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:35 chemistry
Programme:Chemical Engineering MSc (60437)
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