Presenter: Prof. Jonas Björk (Department of Physics, Chemistry and Biology, IFM, Linköping University, Sweden）
Topic:Insights into on-surface synthesis of novel nanomaterials from theoretical modeling
Time: 03:00 PM, Nov. 23th (Wednesday)
Location: Conference Room B, BLDG 909-1F
On-surface synthesis is a promising approach for engineering atomically-precise covalent nanostructures. By triggering chemical reactions between molecular building blocks on surfaces, covalent nanoarchitectures are constructed in a bottom-up fashion. The dimensions of the resulting structures are controlled by the molecules and the kind of reactions induced between them, and a plethora of novel nanomaterials are within reach, promising for use in nanoelectronics, optoelectronics and other fields where new low-dimensional materials with tailored properties are needed.
Despite outstanding prospects, on-surface synthesis faces great challenges. Most critically, the predictability for how molecules react on surfaces is low, and the success has to a large extent been relying on experimentation. This approach has been successful providing synthesis routes of a handful of new materials, such as atomically precise graphene nanoribbons1 and single-chirality carbon nanotubes.2 However, to unleash the full potential of on-surface synthesis, we need to improve our outstanding of the on-surface reactions, which often behave fundamentally different from their wet chemistry analogues.
Last years it has become customary to study the mechanisms related to on-surface synthesis computationally, using transition state theory together with density functional theory.3 The choice of DFT is due to that it provides, in most cases, the highest level of theory computational viable to treat these reactions. By combining DFT with methods for finding transition states, we can obtain detailed information about the reactions.
In the seminar I will present my research that has focused on gaining atomic insight into on-surface synthesis. The seminar will particularly attend to two types of reactions: On-surface Ullmann coupling – probably the most commonly applied on-surface synthesis protocol – which has been used to create for example graphene nanoribbons and porous graphene. General aspects of the reaction will be discussed, such as dehalogenation and concomitant coupling of aryl halides,4 as well how the processes are affected by choice of molecular building blocks and the presence of metal adatoms on the surfaces. We will also examine the surface chemistry of terminal ethyls, which was recently employed to manufacture phthalocyanine tapes from tetraazaporphyrins.5 In this case, we will particularly concentrate on the thermodynamics of the reactions.6
1. J. Cai et al. “Atomically precise bottom-up fabrication of graphene nanoribbons”, Nature 2010, 466, 470.
2. J. R. Sanches-Valencia et al. “Controlled synthesis of single-chirality carbon nanotubes”, Nature 2014, 512, 61.
3. J. Björk. “Reaction mechanisms for on-surface synthesis of covalent nanostructures”, J. Phys. Condens. Matter 2016, 28, 083002.
4. J. Björk, F. Hanke and S. Stafström. “Mechanisms of halogen-based covalent self-assembly on metal surfaces”, J. Am. Chem. Soc. 2013, 135, 5768.
5. B. Cirera, et al. “Thermal selectivity of intermolecular versus intramolecular reactions on surfaces”, Nat. Commun. 2016, 7, 11002.
6. J. Björk. “Thermodynamics of an electrocyclic ring-closure reaction on Au(111)”, J. Phys. Chem. C 2016, 120, 21716.
Contact：Prof. Lifeng Chi