[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

https://absimage.aps.org/image/MAR14/MWS_MAR14-2014-020819.pdf

Van der Waals heterostructures

Petroleum is one of the most precious and complex molecular mixtures existing. Because of its chemical complexity, the solid component of crude oil, the asphaltenes, poses an exceptional challenge for structure analysis, with tremendous economic relevance. Here, we combine atomic-resolution imaging using atomic force microscopy and molecular orbital imaging using scanning tunnelling microscopy to study more than 100 asphaltene molecules. The complexity and range of asphaltene polycyclic aromatic hydrocarbons are established in detail. Identifying molecular structures provides a foundation to understand all aspects of petroleum science from colloidal structure and interfacial interactions to petroleum thermodynamics, enabling a first-principles approach to optimize resource utilization. Particularly, the findings contribute to a long-standing debate about asphaltene molecular architecture. Our technique constitutes a paradigm shift for the analysis of complex molecular mixtures, with possible applications ...

Unraveling the Molecular Structures of Asphaltenes by Atomic Force Microscopy

Surface chemistry of porphyrins and phthalocyanines

An sp-hybridized all-carboatomic ring, cyclo[18]carbon: Electronic structure, electronic spectrum, and optical nonlinearity

Carbon allotropes built from rings of two-coordinate atoms, known as cyclo[n]carbons, have fascinated chemists for many years, but until now they could not be isolated or structurally characterized because of their high reactivity. We generated cyclo[18]carbon (C18) using atom manipulation on bilayer NaCl on Cu(111) at 5 kelvin by eliminating carbon monoxide from a cyclocarbon oxide molecule, C24O6 Characterization of cyclo[18]carbon by high-resolution atomic force microscopy revealed a polyynic structure with defined positions of alternating triple and single bonds. The high reactivity of cyclocarbon and cyclocarbon oxides allows covalent coupling between molecules to be induced by atom manipulation, opening an avenue for the synthesis of other carbon allotropes and carbon-rich materials from the coalescence of cyclocarbon molecules.

https://science.sciencemag.org/content/sci/early/2019/08/14/science.aay1914.full.pdf

An sp-hybridized molecular carbon allotrope, cyclo[18]carbon

On the early stages of soot formation: Molecular structure elucidation by high-resolution atomic force microscopy

Combustion-generated soot particles can have significant impact on climate, environment and human health. Thus, understanding the processes governing the formation of soot particles in combustion is a topic of ongoing research. In this study, high-resolution atomic force microscopy (AFM) was used for direct imaging of the building blocks forming the particles in the early stages of soot formation. Incipient soot particles were collected right after the particle nucleation zone of a slightly sooting ethylene/air laminar premixed flame at atmospheric pressure and analyzed by AFM after a rapid sublimation procedure. Our data shed light on one of the most complex and still debated aspect on soot formation, i.e., the nucleation process. The molecular constituents of the initial particles have been individually analyzed in detail in their chemical/structural characteristics. Our data demonstrate the large complexity/variety of the aromatic compounds which are the building blocks of the initial soot particles. Nevertheless, some fundamental and specific characteristics have been clearly ascertained. These include a significant presence of penta-rings as opposed to the purely benzenoid aromatic compounds and the noticeable presence of aliphatic side-chains. In addition, there were indications for the presence of persistent π radicals. Incipient soot was also investigated by Raman spectroscopy, the results of which agreed in terms of chemical and structural composition of the particles with those obtained by AFM.

Insights into incipient soot formation by atomic force microscopy

Hexagonal boron nitride (h-BN) is a prominent member in the growing family of two-dimensional materials with potential applications ranging from being an atomically smooth support for other two-dimensional materials to templating growth of molecular layers. We have studied the structure of monolayer h-BN grown by chemical vapor deposition on Ir(111) by low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) experiments and state-of-the-art density functional theory (DFT) calculations. The lattice mismatch between the h-BN and Ir(111) surface results in the formation of a moir\'e superstructure with a periodicity of $\ensuremath{\sim}$29 \AA{} and a corrugation of $\ensuremath{\sim}$0.4 \AA{}. By measuring the field emission resonances above the h-BN layer, we find a modulation of the work function within the moir\'e unit cell of $\ensuremath{\sim}$0.5 eV. DFT simulations for a 13-on-12 h-BN/Ir(111) unit cell confirm our experimental findings and allow us to relate the change in the work function to the subtle changes in the interaction between boron and nitrogen atoms and the underlying substrate atoms within the moir\'e unit cell. Hexagonal boron nitride on Ir(111) combines weak topographic corrugation with a strong work function modulation over the moir\'e unit cell. This makes h-BN/Ir(111) a potential substrate for electronically modulated thin film and heterosandwich structures.

/pdf/epitaxial-hexagonal-boron-nitride-on-ir-111-a-work-function-122nimpljj.pdf

Epitaxial hexagonal boron nitride on Ir(111): A work function template

Using low-temperature scanning tunneling microscopy, we show that monolayer hexagonal boron nitride (h-BN) on Ir(111) acts as ultrathin insulating layer for organic molecules, while simultaneously templating their self-assembly. Tunneling spectroscopy experiments on cobalt phthalocyanine (CoPC) reveal narrow molecular resonances and indicate that the charge state of CoPC is periodically modulated by the h-BN moire superstructure. Molecules in the second layer show site-selective adsorption behavior, allowing the synthesis of molecular dimers that are spatially ordered and inaccessible by usual chemical means.

Fabian Schulz

Papers

An sp-hybridized molecular carbon allotrope, cyclo[18]carbon

On the early stages of soot formation: Molecular structure elucidation by high-resolution atomic force microscopy

Insights into incipient soot formation by atomic force microscopy

Epitaxial hexagonal boron nitride on Ir(111): A work function template

Templated self-assembly and local doping of molecules on epitaxial hexagonal boron nitride.