Presenter: Prof. JonasBjörk (Department of Physics, Chemistry and Biology, IFM, Linköping University,Sweden）
Topic:Insightsinto on-surface synthesis of novel nanomaterials from theoretical modeling
Time: 03:00 PM, Nov.23th (Wednesday)
Location: ConferenceRoom B, BLDG 909-1F
Abstract
On-surface synthesis is a promisingapproach for engineering atomically-precise covalent nanostructures. Bytriggering chemical reactions between molecular building blocks on surfaces,covalent nanoarchitectures are constructed in a bottom-up fashion. Thedimensions of the resulting structures are controlled by the molecules and thekind of reactions induced between them, and a plethora of novel nanomaterialsare within reach, promising for use in nanoelectronics, optoelectronics andother fields where new low-dimensional materials with tailored properties areneeded.
Despite outstanding prospects,on-surface synthesis faces great challenges. Most critically, thepredictability for how molecules react on surfaces is low, and the success hasto a large extent been relying on experimentation. This approach has beensuccessful providing synthesis routes of a handful of new materials, such asatomically precise graphene nanoribbons1 and single-chirality carbonnanotubes.2 However, to unleash the full potential of on-surfacesynthesis, 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 tostudy the mechanisms related to on-surface synthesis computationally, usingtransition state theory together with density functional theory.3 The choice of DFT is due to that it provides, in most cases, the highest levelof theory computational viable to treat these reactions. By combining DFT withmethods for finding transition states, we can obtain detailed information aboutthe reactions.
In the seminar I will present myresearch that has focused on gaining atomic insight into on-surface synthesis.The seminar will particularly attend to two types of reactions: On-surfaceUllmann coupling � probably the most commonly applied on-surface synthesisprotocol � which has been used to create for example graphene nanoribbons and porousgraphene. General aspects of the reaction will be discussed, such asdehalogenation and concomitant coupling of aryl halides,4 as wellhow the processes are affected by choice of molecular building blocks and thepresence of metal adatoms on the surfaces. We will also examine the surfacechemistry of terminal ethyls, which was recently employed to manufacturephthalocyanine tapes from tetraazaporphyrins.5 In this case, we willparticularly concentrate on the thermodynamics of the reactions.6
References
1. J. Caiet 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 carbonnanotubes”, Nature 2014, 512, 61.
3. J.Björk. “Reaction mechanisms for on-surface synthesis of covalentnanostructures”, J. Phys. Condens. Matter 2016, 28, 083002.
4. J.Björk, F. Hanke and S. Stafström. “Mechanisms of halogen-based covalentself-assembly on metal surfaces”, J. Am. Chem. Soc. 2013, 135, 5768.
5. B.Cirera, et al. “Thermal selectivity of intermolecular versus intramolecularreactions 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
