Oral Presentation 26th ACMM “2020 Visions in Microscopy”

Investigation of Novel Nano-scale Triazine Bilayer Crystallites using Atomic Force Microscopy (AFM) (#143)

Yin Yao 1 , Mohan Bhadbhade 2 , Christopher Marjo 2
  1. Electron Microscope Unit/Mark Wainwright Analytical Centre, University of New South Wales, Kensington UNSW Sydney, NSW, Australia
  2. Solid State and Elemental Analysis Unit (SSEAU)/Mark Wainwright Analytical Centre, University of New South Wales, Kensington UNSW Sydney, NSW, Australia

Nano-materials have attracted increasing attention in literature owing to their potential application in energy conversion/storage, catalysis and photovoltaics. Most well characterised nano-materials in literature are based on inorganic systems, best examples are titanium dioxide, graphene and boron nitride1. However, organic nano-materials are often poorly studied. Here, we present a novel type of nitrogen-containing organic heterocyclic molecules, namely triazine, which can self-assemble and form planar nano-crystallites, when deposited from solution onto a flat substrate. The triazine derivatives with bi-substituted alkyl chains of varying lengths are firstly dissolved in chloroform, then deposited or drop casted onto freshly cleaved mica. AFM measurements of topography show that crystallites only a few molecules can be formed on the mica substrate, and such crystallites show very interesting morphologies and mechanical properties on the nanoscale. The step height of these crystals are measured to be approximately 1.8±0.2nm, which is in good agreement with crystallographic models. The DMTmodulus of the crystals are estimated to be 0.5-1.5GPa, which is substantially higher than long-chain organic compounds such as paraffin wax2. The higher than expected modulus could be related to the strong hydrogen bonding in the ab plane of the crystals. Additional AFM measurements have shown that it is possible to form multiple layers of crystals, which can stack on top of each other. Moreover, it is observed by adjusting the concentration of the triazine in solution, it is possible to deposit a semi-continuous film on the surface. Therefore, by adjusting the concentration and operating parameters, it is possible to form not just 2D crystallites on the surface, but also continuous thin films.

  1. 1. Liang, Y., Wang, H., Sanchez Casalongue, H. et al. Nano Res. (2010) 3: 701. https://doi.org/10.1007/s12274-010-0033-5
  2. 2. DeSain, John & Brady, Brian & Metzler, Kelly & Curtiss, Thomas & Albright, Thomas. (2009). Tensile Tests of Paraffin Wax for Hybrid Rocket Fuel Grains. 45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit. 10.2514/6.2009-5115.