ترغب بنشر مسار تعليمي؟ اضغط هنا

Transferring Axial Molecular Chirality Through a Sequence of On-Surface Reactions

45   0   0.0 ( 0 )
 نشر من قبل Dimas G. de Oteyza
 تاريخ النشر 2020
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

Fine management of chiral processes on solid surfaces has progressed over the years, yet still faces the need for the controlled and selective production of advanced chiral materials. Here, we report on the use of enantiomerically enriched molecular building blocks to demonstrate the transmission of their intrinsic chirality along a sequence of on-surface reactions. Triggered by thermal annealing, the on-surface reac-tions induced in this experiment involve firstly the coupling of the chiral reactants into chiral polymers and subsequently their transformation into planar prochiral graphene nanoribbons. Our study reveals that the axial chirality of the reactant is not only transferred to the polymers, but also to the planar chirality of the graphene nanoribbon end products. Such chirality transfer consequently allows, starting from ad-equate enantioenriched reactants, for the controlled production of chiral and prochiral organic nanoarchi-tectures with pre-defined handedness.

قيم البحث

اقرأ أيضاً

Self-diffusion and impurity diffusion both play crucial roles in the fabrication of semiconductor nanostructures with high surface-to-volume ratios. However, experimental studies of bulk-surface reactions of point defects in semiconductors are strong ly hampered by extremely low concentrations and difficulties in the visualization of single point defects in the crystal lattice. Herein we report the first real-time experimental observation of the self-interstitial reactions on a large atomically smooth silicon surface. We show that non-equilibrium self-interstitials generated in silicon bulk during gold diffusion in the temperature range 860-1000^oC are annihilated at the (111) surface, producing the net mass flux of silicon from the bulk to the surface. The kinetics of the two-dimensional islands formed by self-interstitials are dominated by the reactions at the atomic step edges. The activation energy for the interaction of self-interstitials with the surface and energy barrier for gold penetration into the silicon bulk through the surface are estimated. These results demonstrating that surface morphology can be profoundly affected by surface-bulk reactions should have important implications for the development of nanoscale fabrication techniques.
363 - M.-Y. Yao , J. Noky , K. Manna 2021
Quasiparticle excitations described by the Weyl equation in solids have attracted massive attention in recent years. So far, a wide range of solids have been experimental realized as Weyl semimetals (WSMs). On the other hand, for a compound to displa y Weyl points it must exhibit either inversion symmetry breaking or time reversal symmetry breaking. Hence, the Weyl fermions are vulnerable to annihilation from structural distortions or lattice imperfections. In the absence of both mirror and inversion symmetry, SrSi2 has been predicted as a robust WSM by recent theoretical works. Here, supported by first-principles calculations, we present systematical angle-resolved photoemission studies of undoped SrSi2 and Ca-doped SrSi2 single crystals. However, our result shows no evidence of the predicted Weyl fermions at the kz = 0 plane, as well as the Fermi arcs on (001) surface. Combined with the first-principles calculations, we suggest that SrSi2 is a topologically trivial semiconductor.
The first principles density functional theory (DFT) is applied to study effects of molecular adsorption on optical losses of silver (111) surface. The ground states of the systems including water, methanol, and ethanol molecules adsorbed on Ag (111) surface were obtained by the total energy minimization method within the local density approximation (LDA). Optical functions were calculated within the Random Phase Approximation (RPA) approach. Contribution of the surface states to optical losses was studied by calculations of the dielectric function of bare Ag (111) surface. Substantial modifications of the real and imaginary parts of the dielectric functions spectra in the near infrared and visible spectral regions, caused by surface states and molecular adsorption, were obtained. The results are discussed in comparison with available experimental data.
Anisotropic magnetoresistance (AMR), originating from spin-orbit coupling (SOC), is the sensitivity of the electrical resistance in magnetic systems to the direction of spin magnetization. Although this phenomenon has been experimentally reported for several nanoscale junctions, a clear understanding of the physical mechanism behind it is still elusive. Here we discuss a novel concept based on orbital symmetry considerations to attain a significant AMR of up to 95% for a broad class of $pi$-type molecular spin-valves. It is illustrated at the benzene-dithiolate molecule connected between two monoatomic nickel electrodes. We find that SOC opens, via spin-flip events at the ferromagnet-molecule interface, a new conduction channel, which is fully blocked by symmetry without SOC. Importantly, the interplay between main and new transport channels turns out to depend strongly on the magnetization direction in the nickel electrodes due to the tilting of molecular orbital. Moreover, due to multi-band quantum interference, appearing at the band edge of nickel electrodes, a transmission drop is observed just above the Fermi energy. Altogether, these effects lead to a significant AMR around the Fermi level, which even changes a sign. Our theoretical understanding, corroborated in terms of textit{ab initio} calculations and simplified analytical models, reveals the general principles for an efficient realization of AMR in molecule-based spintronic devices.
77 - N. Foley , S. Cazaux , D. Egorov 2018
We present experimental data on H2 formation processes on gas-phase polycyclic aromatic hydrocarbon (PAH) cations. This process was studied by exposing coronene radical cations, confined in a radio-frequency ion trap, to gas phase H atoms. Sequential attachment of up to 23 hydrogen atoms has been observed. Exposure to atomic D instead of H allows one to distinguish attachment from competing abstraction reactions, as the latter now leave a unique fingerprint in the measured mass spectra. Modeling of the experimental results using realistic cross sections and barriers for attachment and abstraction yield a 1:2 ratio of abstraction to attachment cross sections. The strong contribution of abstraction indicates that H2 formation on interstellar PAH cations is an order of magnitude more relevant than previously thought.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا