2020 - PCPP - Soot E-bridge formation PAH
2020 - ApJ - PAHs to carbonaceous dust grain
- Low-temperature Formation of Carbonaceous Dust Grains from PAHs
- L.G. Marin, S. Bejaoui, M. Haggmark, N. Svadlenak, M. de Vries, E. Sciamma-O’Brien, and F. Salama, ApJ 889, 101 (2020).
This is an experimental study on the connection between PAHs (gas phase) and carbonaceous dust grain (solid phase) for understanding the evolution of cosmic carbon.
- fig: different PAHs -> resulting grain
What is the existence form of cosmic carbon?
- Gas phase, PAHs
- large PAHs with compact regular structures
- PAHs with aliphatic side groups
- mixed aromatic/aliphatic structures
- Solid phase, dust
COSmIC facility in NASA Ames
- carbon-bearing molecules in circumestellar, interstellar and planetary environments
- low temperatures and densities
- the pulsed discharge nozzle is used as a plasma reactor for the generation of grains
2020 - J. Phys. Chem. C
- Oligomerization of Dehydrogenated Polycyclic Aromatic Hydrocarbons on Highly Oriented Pyrolytic Graphite
- J. Weippert, J. Hauns, J. Bachmann, J.-F. Greisch, A. Narita, K. Müllen, A. Böttcher, and M.M. Kappes, J. Phys. Chem. C 124, 8236 (2020).
This paper demonstrates a controllable method to generate PAH oligomers on graphite.
The process starts with the fragmentation of PAH in the gas phase using electron impact (60 ~ 70 eV).
The dominant fragmentation pathway is the loss of n H2.
The resulting PAH radical after mass selection is deposited on graphite with a low kinetic energy (< 6 eV).
The absorbed radicals react with each other to form covalently binding PAH dimer, trimer, ..., oligomer.
- The synthesis of graphene nanoribbon on non-mental surfaces is important for integration into electronic devices. This is understandable, since the commonly used transition metal surfaces in GNRs thesis is too active and may easily get erosion under the working condition of electronic devices, if the metal surfaces have to stay in electronic devices. But GNRs synthesis on graphite requires PAH fragment generated by electron impact. Is this durable for electronic devices? Will graphite stay in electronic devices as well? If one has to remove GNRs from surface after synthesis, why not use metal surfaces?
2017 - ApJ - PAH with atomic carbon
- In the introduction, the authors have mentioned that small PAHs should be destroyed, but large PAHs (30-50 carbon atoms) can survive in the harsh astrophysical environments.
- Factors influencing molecular abundances include UV irradiations and chemical reactions.
2013 - PNAS - Oligomerization of protein by MD
This paper combines metadynamics and parallel tempering to explore the free energy land scape of protein oligomerization.
The oligomerization is assumed to be a multi step process.
- Folding of monomer
- Dimerization of two
prefolded monomers (avoid sampling irrelevant regions of the configuration space at high temperature used in the parallel tempering)
Borrow from replica exchange in MD, can we perform operations on multiple candidates in GOFEE?
2013 - JPCA - PAH dimer in soot formation
- Dimerization of Polycyclic Aromatic Hydrocarbons in Soot Nucleation
- H.-B. Zhang, X. You, H. Wang, and C.K. Law, J. Phys. Chem. A 118, 1287 (2014).
(U)PM6 and (U)M06-2X almost predicts the same optimized structure of PAH dimers and bond features including:
- the bond order
- the number of bonds
- the bonding sites
- $\pi$ electrons play an important role in the dimerization (in a stacked way) of PAHs and a bond tends to be formed in the region where the density of $\pi$ electrons is high.
- The dimerization of two non-identical PAHs are more likely than two identical PAHs under the flame environment.
- PAH dimers are important intermediates in combustion and soot formation