Chemical Mapping of Nano-defects within 2D Covalent Monolayers by Tip-enhanced Raman Spectroscopy
ACS Nano, vol. 12: no. 5, pp. 5021-5029, Washington, DC: American Chemical Society, 2018.
Dr. Wenyang Dai
Main content
Research Interests
My research interest is in the creation of robust 2D polymers [1] preferably at the air/water interface and the analysis of their properties. Hereby the focus is on the mechanical characteristics as obtained by e.g. AFM nanoindentation experiments. These latter experiments are being carried out in collaboration with the groups of Prof. Andreas Stemmer (ETH/IBM) and Prof. Hans-Jürgen Butt, MPI-P, Mainz, Germany.
In particular, I am extending on the method by T. Bauer et al. [2] and polymerize monomers with complexing sites at the air-water interface by providing transition metal salts as connectors from the subphase (Figure 1). The porphyrin-based monomer (M4-0) was synthesized and the polymerization of the monomers was conducted on the Langmuir-Blodgett trough (Figures 2 and 3).
Figure 1: Chemical structure of one of the monomers in study and the typical procedure on how to create metal-organic sheets (monolayer MOFs) using a Langmuir Blodgett trough under ambient conditions. (a) Spreading of the monomer, (b) compressing the monomer to an optimum mean molecular area and (c) injecting the metal ion connectors.
Figure 2. Idealized chemical structure of the obtained metal-organic sheet. Structure analysis involves transfer over holes, AFM imaging, GI-XRD (in collaboration with Prof. Motomu Tanaka, U Heidelberg), UV/vis spectroscopy, fluorescence spectroscopy, STM etc.
Figure 3. Left: Photograph of a metal-organic sheet formed on the water surface. Observe the yellowish part. Right: SEM image of metal-organic sheet prepared at the air/water interface after horizontal transfer onto a TEM grid with holes of 20x20 mycrom2. Ruptures are due to the drying event and possibly SEM imaging and create the necessary contrast to actually see the sheets
Relevant literature:
[1] J. Sakamoto, J. van Heijst, O. Lukin, A. D. Schlüter, Angew. Chem. Int. Ed., 2009, 48, 1030-1069; J. W. Colson, W. R. Dichtel, Nature Chemistry, 2013, 5, 453-465
[2] T. Bauer, Z. Zheng, A. Renn, R. Enning, A. Stemmer, J. Sakamoto, Angew. Chem. Int. Ed., 2011, 50, 7879-7884 Z. Zheng, L. Opilik, F. Schiffmann, W. Liu, G. Bergamini, P. Ceroni, L.-T. Lee, A. Schütz, J. Sakamoto, R. Zenobi, J. VandeVondele, A. D. Schlüter, J. Am. Chem. Soc., 2014, 136, 6103-6110
Publications
Three-Legged 2,2'-Bipyridine Monomer at the Air/Water Interface: Monolayer Structure and Reactions with Ni(II) Ions from the Subphase
Langmuir, vol. 33: no. 7, pp. 1646-1654, Washington, DC: American Chemical Society, 2017.
Synthesis of a Two-Dimensional Covalent Organic Monolayer through Dynamic Imine Chemistry at the Air/Water Interface
Angewandte Chemie. International Edition, vol. 55: no. 1, pp. 213-217, Weinheim: Wiley, 2016.