Graphene is a perfect 2D crystal of covalently bonded carbon atoms that exhibits extraordinary properties in many fields of physical sciences [1].  As a template it consists of the basis for the formation of all graphitic structures.   Nevertheless, 2D crystals cannot have a significant impact in the real world, until efficient production techniques are developed to harvest their unique properties in global applications and devices.

Chemical Vapor Deposition (CVD) is the most well-known method of automated graphene growth [2]. The chemical process is rather complex, as it involves multiple steps on a solid metal catalyst (SMCaT), such as hydrocarbon decomposition, carbon adsorption and diffusion, generation of nucleation points and graphene consolidation. Thermal mismatch effects on cooling down from elevated temperatures and subsequent transfer to other substrates, induce morphological defects and contaminations, which impair the inherent physical properties of graphene (and other 2DMs). Switching to liquid metal catalysts (LMCat) might be a solution for the production of defect-free single graphene domains at high production speeds due to the enhanced atomic mobility, homogeneity, and fluidity in that process.  Videos of graphene grown on molten copper will be presented in which both self-alignment of crystals of random orientations and growth of large single crystals will be observed at real time. Moreover, removing the formed 2D membrane from the hot metal substrate appears feasible as the the viscous forces that hold the grown material on the liquid metal are extremely weak.

In-situ monitoring of chemical reactions within the CVD reactors is of paramount importance for the control of graphene growth and the understanding of growth kinetics. In particular, I will be presenting recent results on the use of Laser Reflectometry for monitoring graphene growth in SMCaT processes.  Furthermore, I will show how another optical technique (laser Raman) using a near UV excitation line at 405 nm to reduce the black body radiation, can be employed to monitor graphene growth in LMCaT processes at high temperatures (>1000 C).

Mechanical properties of 2D materials is another active area of research of our group.  I will show you some aspects of our recent work on the control of wrinkle formation in monolayer graphene and also on the bending behavior of both homo- and hetero- 2D structures.  Moving to applications, I will be showing new processing strategies for the production of macro-scale CVD-graphene/polymer nanolaminates based on the combination of ultra-thin casting, wet transfer and floating deposition [3, 4]. These composites possess excellent mechanical and electrical properties and can be employed as coatings for EMI shielding or electro-active displays. 

Finally, the use of large transparent graphene veils for the protection of art works such as paintings will also be covered briefly in this presentation [5].

References

[1] Novoselov K. S. et al., Proc. Natl. Acad. Sci., 102, 10451, 2005

[2] Bae S. et al., Nat. Nanotechnology, 5, 574, 2010

[3] Vlassiouk I et al., ACS Appl Mater Interfaces, 20, 10702, 2015

[4] Pavlou Ch. al, Nature Comms, revised manuscript submitted, 2021

[5] Kotsidi et al, Nat. Nanotechnology, revised manuscript submitted, 2021

Multiblock copolymers with charged blocks are complex systems which show great potential for enhancing the structural control of block copolymers. We investigate the morphologies formed in thin films prepared from aqueous solutions having different pH values. In my talk, I will present two examples: (i) The morphologies formed by pentablock quaterpolymers featuring hydrophobic end blocks as well as pH-responsive and hydrophilic midblocks can be controlled by the choice of the pH value during film preparation and the solvent polarity during solvent vapor swelling. (ii) A pentablock terpolymer with hydrophobic end blocks and two types of weak cationic polyelectrolyte midblocks. In this system, the mixing behavior of the blocks and the block sequence, governing the bridging behavior, result in strong variations of the nanostructures and their repeat distances.