PhD ceremony mr. A.J. Shaikh: Single molecule electronics. A systematic approach to study the properties of single porphyrin molecules

PhD ceremony: mr. A.J. Shaikh, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Single molecule electronics. A systematic approach to study the properties of single porphyrin molecules

Promotor(s): prof. J.C. Hummelen, prof. J.H. van Esch

Faculty: Mathematics and Natural Sciences

Porphyrins are very interesting and important complex organic molecules, studied in prototypical molecular electronic devices. We were interested to study the conductance behaviour of porphyrin molecules at the single molecule level.

We synthesized required trans-amine and thiol functionalized porphyrins and studied their binding with gold nanoparticles as a model surface for nano-electrodes to learn about their interaction strength and dynamics. Among a series of functionalized porphyrins developed for this study, the compounds with four amino functionalities showed the highest binding interaction with gold nanoparticles. We observed photo-induced charge transfer from porphyrins to quantum dots in hybrid systems, while investigating the binding interaction of porphyrins with PbSe quantum dots. This result indicates that these porphyrins are good candidates for single molecule electronic studies.

Finally, we focused on single molecule electronic behaviour of porphyrins using platinum electromigration and mechanically controllable break junction techniques. Amino (-NH2) and thiol (-SH) anchoring groups of porphyrins were bound to the platinum electrodes (for electromigration) and gold electrodes (for MCBJ) using respectively. We distinguished molecular transport from background-tunneling conductances in platinum electromigration technique. A change in conductance was observed, when porphyrin molecules with and without thiol terminations, free base, Zn- and Ru- porphyrins were present in MCBJs. Our porphyrin derivatives showed both planar and perpendicularly probed configurations.

These studies increase our understanding of metal – molecule interactions and electron transport in a single molecule, which is crucial for further development in nanoscale electronics.