Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - NGUEC (Nanostructuring graphene under electrochemical control)

Teaser

Overall Objectives of the ProjectNGUEC aims to develop experimental protocols for controlled and reproducible functionalization, and characterization of graphene in a nanostructured fashion by using chemisorption (covalent) strategies in combination with physisorption...

Summary

Overall Objectives of the Project

NGUEC aims to develop experimental protocols for controlled and reproducible functionalization, and characterization of graphene in a nanostructured fashion by using chemisorption (covalent) strategies in combination with physisorption (non-covalent) approaches, relying on the power of electrochemical control.
Noncovalent functionalization of graphene by using physisorption of organic building blocks is an attractive route as it offers the possibility of attaching functional groups without disturbing the unique electronic structure of graphene. Whereas, functionalization of graphene by chemisorption locally leads to changes in the hybridization of the C-atoms, thereby changing its chemistry and electronic properties.
Importance of society
Graphene, a material consisting of a single atom thick sheet of sp2-hybridized carbon, has recently attracted tremendous interest in both fundamental studies and potential applications due to its unique electronic, optical, mechanical and thermal properties. Despite these exceptional qualities however, some inherent characteristics of graphene itself preclude its widespread usage in technological applications. A prerequisite for the use of graphene in several low- as well as high-end applications, is its controlled and reproducible functionalization in a nanostructured fashion, towards doping and band gap opening, a challenge that has not been addressed in a satisfactory way yet. The present, relatively incoherent experimental protocols suffer from following important shortcomings.
- Firstly, graphene functionalization occurs randomly in solution based methods and there is scarcity of methods that can exert precise control over how and where the reactions/interactions occur.
- Secondly, from a fundamental perspective, a molecular level understanding of the functionalization process is still lacking which precludes systematic strategies for manipulation of graphene.
- In addition, the potential of electrochemistry based functionalization protocols and electrochemistry based characterisation approaches in imaging and analysis of graphene is hardly explored.
Therefore, the fundamental understanding at the molecular level attained from this project is a firm basis for manipulating the properties of graphene in a controlled manner leaned on the power of electrochemistry. More importantly, the experimental findings open new avenues to investigate supramolecular self-assembly of doping molecules in nanoconfined spaces under electrochemical control towards bottom-up creation of nanoconfined doped 2D materials for nanoscale electronics applications.
Conclusions of the Action
The main goal of the project is to control molecular patterns on graphitic surfaces using an electrochemical approach. The project has been executed according the work packages and the following conclusions were made:
- The self-assembly of dibenzyl viologen (DBV) on graphitic surfaces was in-situ characterized by electrochemical scanning tunneling microscopy (EC-STM). A combination of Kelvin probe force microscopy (KPFM) and Raman spectroscopy and microscopy results elucidates that the reduced DBV0 adlayer leads to n-doping of graphene. The collective experimental information obtained on the interfacial structure of DBV and the influence of its adsorption phases on the electronic properties of graphene are valuable for engineering DBV/graphene interface based electronic device applications.
- DBV enables to adsorb within “nanocorrals” created by both top-down and bottom-up approaches. The level of control over the size and shape of nanocorrals will allow investigating nucleation and monolayer growth processes in nanoconfined spaces under electrochemical control. In-situ visualization of the self-assembled layer of DBV on graphitic surfaces reveals the possibility to create such nano p-n junctions based on a combination of physi- and chemi-sorption strategies.

Work performed

During the period of the running project, all proposed work packages were conducted efficiently as follows:
WP1: Non-covalent functionalization of graphene by molecular self-assembly of dibenzyl viologen (DBV) under electrochemical control: the physisorption approach: Using a combination of EC-STM, Raman and KPFM characterization one enables the conclusion of the doping effect of the DBV monolayer on graphene material. The collective experimental information obtained on the interfacial structure of DBV and the influence of this adlayer on the electronic properties of graphene are valuable for engineering DBV/graphene interface for electronic device applications.
WP2: Covalent functionalization of graphene with controlled nanopatterning: In this regard, we were successful in functionalizing covalently the graphene by nano-corrals upon using both top-down and bottom-up approaches.
WP 3: Dual functionalization of graphene under electrochemical control: With respect to this approach, the as-formed nanocorrals can be used as template for further functionalization under electrochemical control such as supramolecular self-assembly. Our finding showed that (i) DBV enables to adsorb within the nanocorrals; (ii) The level of control over the size and shape of nanocorrals will allow investigating nucleation and monolayer growth processes in nanoconfined spaces under electrochemical control; and (iii) In-situ visualization of the self-assembled DBV adlayer on HOPG revealed a possibility to create such nano p-n junctions based on a combination of physi- and chemi-sorption approaches.

Dissemination and Exploitation of Results

Scientific Publications
Nanoconfined self-assembly on a grafted graphitic surface under electrochemical control
Thi Mien Trung Huynh,* Thanh Hai Phan, Oleksandr Ivasenko,a Stijn F. L. Mertens and Steven De Feyter*, Nanoscale, 2017, 9, 362–368.

Dissemination and Communication Activities
Through Conference
ACS 253rd National Meeting & Exposition 2017, San Francisco, United States of America
Through Outreach activity
Giving lectures in the course “Surface chemistry at the nanoscale” to Master and PhD students in February 2017 at Chemistry department, Quy Nhon University, Vietnam where the fellow works as lecturer after finishing the project.
Participation at the “Ladies@Science” event in April 2018 at KU Leuven: This is a one-day event organized by the Faculty of Science, addressing exclusively female students (16 – 17 years old).

Final results

The key scientific achievement of this project is to optimize protocols for controlled and producible functionalization of graphene in a nanostructured fashion. Our novel findings represent an important step for engineering both morphological and electronic properties of graphene at the nanoscale. With respect the fellow, the project have had such important impact on my long term career. Conducting a project on one of the most promising materials, i.e. graphene, helped me to master this new research topic. Having worked together with Prof. De Feyter on this project was a great experience on scientific managements and collaborations. Finally, I am establishing my own independent research group in the area of surface science and electrochemistry at Department of Chemistry, Quy Nhon University. I believe that the knowledge, experience, skills and international collaborations obtained during my fellowship period will definitely be useful for my long-term scientific career in Vietnam.