Methods: Molecular mechanics, Molecular dynamics

In this master thesis, the hybrids of carbon nanomaterials - graphene (G) and graphene oxide (GO) with photochromic azobenzene will be studied. Azobenzene isomerizes, i. e. changes its configuration under UV light, going to the bent cis-state, and back to the flat trans-state under blue light. Both G and GO materials contribute to the green technologies [1].

The goal is to simulate reversible changes in the geometrical structure of the junction, immersed in water.

An illustration of “G-azo-GO” junctions and their response to the light irradiation: the reversible changes in thickness Δh of the layer (1), the GO restructuring (2), the changes in the water content at the SAM/GO interface (3), the conformational transitions in the flexible linkers or changes in tilting angles of the molecules in SAMs (4). Water molecules are omitted for clarity.

Tasks:

1. To prepare the system shown in figure (parameters could be the molecular grafting density in the azobenzene layer, different oxidation degree of graphene oxide)
2. To equilibrate the initial trans bilayer in molecular dynamics simulation
3. To switch the isomerization state of azobenzene (parameter could be the isomers’ ratio) and equilibrate it
4. To analyse both systems 2) and 3) prior and after isomerization. The properties to evaluate are: the overall morphology and stability, thickness Δh of the layer, the hydration of the azobenzenes (interface hydrophobicity), etc.

Key words: azobenzene, graphene, graphene oxide, junction, molecular dynamics, switching

Betreuer: Dr. Olga Guskova / IPF Dresden

References:

[1] Min M., Seo S., Lee S.M., Lee H., Voltage-Controlled Nonvolatile Molecular Memory of an Azobenzene Monolayer through Solution-Processed Reduced Graphene Oxide Contacts, Adv. Mater., 2013, 25(48), 7045