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Local work function determination of HOPG dendronized with amino-aryl/nitro-aryl structures

Research Project
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01.02.2017
 - 31.03.2017

The molecular self-assembly is known to offer a strong tool for creating functional and ordered structures, controlled by the interaction molecule-molecule and molecule-substrate. Self-assembly of dendrons onto a surface is a simple synthetic methodology that offers significant advantages over other polymers to modify the surface. The multi-functionality and versatility achieved by the use of dendritic molecules in molecular arrangements are extremely useful features in the design of new devices, as well as the subject of the study of many scientific fields ranging from heterogeneous catalysis to energy sciences. The large number of chemical groups that these structures expose on their surface offers the unique opportunity of tailor the interfacial properties, thus changing the identity of metal and semiconductors. In that regard, the nature of the peripheral groups alters the interfacial behaviour of the film depending on the interactions that take place: hydrogen-bond, hydrophobic interactions, π-π stacking, etc. As a consequence, controlled differences in features can be obtained. The study of electrical properties of HOPG modified with dendrons containing a peripheral acceptor or donor-electron group could provide valuable information on the chemical reactivity. It may also lead to understand the phase aggregation process of HOPG modified with both dendrons and therefore to the development of surfaces with customized chemical potentials. The technique called Kelvin Probe Force Microscopy (KPFM) has emerged as a versatile and robust tool to study the electrical properties of an important variety of nanomaterials. This technique offers valuable information such as a mapping of the local surface potential of nanostructured materials at surfaces and interfaces. In the case of metallic samples, the measured contact potential difference (CPD) is the work function difference between the tip and the sample. For self-assembly monolayers (SAMs) or thin films (TFs), instead, it measures an effective work function that is the sum of that of the substrate and the dipole moment of the SAM or TF. Importantly, the work function depends on intrinsic properties of the surface arrangement such as its conformation, the chain lengths of its organic skeleton, but also on extrinsic variables such as the density and the packing of the chemisorbed or physisorbed molecules, humidity conditions, etc. The main objective of this project is the study of the electrical properties of HOPG surfaces modified by G1-NH2 and G1-NO2 dendrons at fully controlled humidity conditions. A comparative study of the variation of local CPD according to the type of peripheral functional group is proposed. Moreover, a morphological and electrical study of HOPG surfaces modified by both dendrons to study the possible formation of phase segregated structures and its effect on the variation of the CPD.

Funding

Local work function determination of HOPG dendronized with amino-aryl/nitro-aryl structures

SNF Projekt (GrantsTool), 02.2017-03.2017 (2)
PI : Glatzel, Thilo.
CI : Farias, Eliana.

Members (2)

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Thilo Glatzel

Principal Investigator
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Eliana Farias

Co-Investigator